Biodiversity and Conservation of Ornamental Crops

Abstract

Ornamental plants are grown for decorative purposes in gardens and landscape design, as house plants, for cut flowers and specimen display, and are associated with the mankind from time immemorial. Approximately, 406,700 species of plants are available on Earth, and out of these plants, 85,000–99,000 species of plants have ornamental value such as trees, shrubs, climbers and creepers, palms, ferns, orchids, grasses, bamboos and reeds, cacti and succulents, annuals, bulbs, and other flowering crops, spreading over the tropical, subtropical, and temperate zones of the world. The market for ornamental plants is constantly increasing day by day but at the same time is subjected to periodic trend-driven changes. Indeed, every year, hundreds of new cultivars, replacing the current assortment, are produced. Hence, this diversity in ornamentals constitutes a great breeding material source for development of novel varieties. For this reason, the protection and storage of these valuable genetic resources is of great importance to be always able to meet market demands. Conservation of the biodiversity of the Earth’s ornamental crops is a continuous process of development for human benefit in response to changes in the design of gardens as well as the commercial exploration of different flowering crops. In this chapter, a wide diversity of ornamental species and their methods of conservation using various approaches are described. Presently, ornamental germplasm are conserved through in situ and ex situ methods in forests, national parks, botanical gardens, and arboreta. Also, the use of recent biotechnological tools, ranging from the drying of seeds to cryopreservation of embryos, pollens, etc., has served as a boon in preserving the diversification of ornamentals and also in producing quality planting materials available to the actual market of ornamental plants.

1 Introduction

In the past, ornamental plants were produced mainly for their aesthetic value. These plants have been an important element of human culture and economy since ancient times. Conservation of the biodiversity of the Earth’s ornamental crops is a continuous process of development for human benefit in reponse to changes in the design of gardens as well as the commercial exploration of different flowering crops. The Melbourne Botanic Gardens in all its publications has stressed this concept, that “the garden is an ever changing museum of living plants.” (Almond 1993). Approximately 406,700 species of plants are available on our Earth, and some of these species have ornamental value, such as trees, shrubs, climbers and creepers, palms, ferns, orchids, grasses, bamboos and reeds, cacti and succulents, annuals, bulbous, and other flowering crops, spread over the tropical, subtropical and temperate zones of the world. There are 12 world mega-biodiversity centers, 17 mega-diverse nations, 8 centers of origin of crop plants, and 34 Hot Spots of Biodiversity in the world. Diversification of these plants began during the Vedic period (3000–2000 BC) through the acts of kings and rulers. Now, various types of gardens, such as home gardens, institutional gardens, industrial gardens, window gardens, roof gardens, rock gardens, water gardens, cemetery gardens, moon gardens, sunken gardens, marsh gardens, island gardens, boulevard gardens, and wall gardens, are established in our society. Regarding the cultivation aspect, many species and varieties have been domesticated and diversified for commercial exploitation by farmers and nursery growers. In developed countries, ornamental plants were diversified long ago for improvement in the standard of living. In developing countries, however, people with lower incomes are not interested in ornamental plants; they are more interested in other horticultural crops such as fruits, vegetables, spices, and plantation crops, their food security being of prime importance. The horticultural enterprise has been handled by “hand-to-mouth” peoples in developing countries. The importance of this enterprise has gained momentum during the past decade, because people are more conscious of their standard of living, with rapid urbanization and increased export avenues. Farmers are searching for alternative high-value crops instead of traditional field crops farming, so that they can survive in the field of agri-business. Governmental institutions are considering the biodiversity and conservation of ornamental crops, but nursery enterprises also have a vital role in dissemination of ornamental foliage and flowering plants. The botanical gardens of the world have a fundamental role in the scientific management of ornamental plants. These institutions have emphasized the identification, domestication, diversification, conservation and the improvement of ornamental crops for the benefit of researchers, students and end users. The biodiversity and conservation of ornamental crops have seen great benefits in the Netherlands, which controls the world floriculture market, with 52% of the total produce in the world; nine other important countries contribute 40%, including Columbia (15%), Ecuador (9%), Kenya (7%), Belgium (3%), Ethiopia (2%), Malaysia (1%), Italy (1%), Germany (1%) and Israel (1%). Now, the effects of biodiversity and conservation of ornamental plants in developing countries are reflected in the production system of the world floriculture export scenario as well as in the domestic market.

2 Scope of Biodiversity and Conservation of Ornamental Crops

At present, this sector is very promising, with a 12% to 25% growth rate, whereas the growth rate of agriculture in the world is less than 4% on an average. Regarding the cost–benefit ratio, it was found that the maximum return per unit area can be obtained from floricultural crops. Also, there is scope in the nursery business for quality plant material production for domestic consumption as well as export. Since the beginning, biodiversity of ornamental plants has been mishandled throughout the world because of control by private sectors, which brought different kinds of plants from various sources: plants were collected, domesticated, multiplied and sold for the interest of the margin of profit, not for the sake of conservation for future use. For this reason, some important native ornamental plants are distinct from their sources of origin. The time has come to conserve scientifically, by either in situ or ex situ conservation, the ornamental plants we have or that are imported. During the past decade, many national and central institutes, agricultural universities, and the private sector have shown keen interest in the conservation of ornamental plants. Government funding agencies and different government departments are also giving emphasis to the biodiversity and conservation of ornamental plants, providing project-based government subsidies for the establishment of infrastructures and human resources development through training for the promotion and production of ornamental horticultural crops.

3 Biodiversity

3.1 Ornamental Trees

Trees are the largest specimens of woody perennial plants having a definite trunk. Trees constitute an important group of ornamental plants that maintain ecological balance, check air pollution, collect air pollutants, reduce noise pollution, reduce soil erosion, improve water conservation and beautify their surrounding environments. Most of the tree species in the world are planted through forest departments with the aim for harvest of the timber as well as fuel. However, from the ornamental point of view, for the development of various types of gardens, parks and roadside decoration with different trees, species having important flowers or good foliage or aesthetic value, etc., are collected, domesticated, and propagated by different botanical gardens, national institutes, central institutes, or State Agricultural Universities (SAUs), and some reputed nongovernmental organizations (NGOs) and nurseries. Important ornamental tree species planted in different parts of the world in tropical, subtropical and temperate zones are listed in Table 1.

Table 1 List of ornamental trees species biodiversity in the world

3.1.1 Ornamental Trees Diversified for Gardening in Moist Areas

Moist areas have a high water table in the groundwater or are in high rainfall areas, or may be areas with longer duration of rainfall, but are not necessarily waterlogged conditions. Under these circumstances not all types of flowering plants can survive. In such situations, gardening has developed with such tree species as Alstonia scholaris, Amherstia nobilis, Barringtonia spp., Bauhinia variegata, Brownea coccinea, Colvillea racemosa, Delonix regia, Dillenia indica, Lagerstroemia speciosa, Peltophorum pterocarpum, Samanea saman, Polyalthia longifolia, Pongamia pinnata, Putranjiva roxburghii, Saraca asoca, Terminalia arjuna, and Tamarindus indica.

3.1.2 Ornamental Trees Diversified for Gardening in Marshy Areas

Some areas remain waterlogged for a certain period of the year. Plants must be adapted to survive for a long time for unavoidable circumstances during this period, and thus they perform better in such situations. For gardening at these locations, plantings include Barringtonia spp., Eucalyptus rostrata, Hibiscus tiliaceus, Salix babylonica, and Tamarix articulata.

3.1.3 Ornamental Trees Diversified for Gardening in Dry Areas

Dry areas, where annual rainfall is less than 500 mm, have continued long spells in summer in which the temperature is above 40 °C during the daytime, with sudden drops in temperature in the night, and, having a very low water table, causes water stress in the soil so that it is difficult for plants to survive. Thus, plantings are based on a deep root system, tolerance to salt, tolerance to drought, tolerance to hot winds, etc., including Acacia auriculiformis, Butea monosperma, Bombax ceiba, Callistemon citrinus, Cassia fistula, Ceiba pentandra, Cochlospermum religiosum, Erythrina indica, Eucalyptus robusta, Ficus spp., Milligtonia hortensis, Plumeria spp., Pterygota alata, and Sterculia foetida.

3.1.4 Ornamental Trees Diversified for Gardening in Arid Areas

In ecological conditions prevailing in areas with scanty rainfall and high temperature, with a land cover of only sand, plant survivability is a big problem. However, the vital role of some flowering plants, such as Albizia lebeck, Butea monosperma, Cassia fistula, Casuarina equisetifolia, Eucalyptus citriodora, Melia azadirachta, Prosopis juliflora, and Parkinsonia aculeata, is to perform better in these conditions.

3.1.5 Ornamental Trees Diversified for Gardening in Saline Areas

Saline areas are mainly coastal, where tidal waves submerge the land periodically, but there are also other saline belts lacking a drainage system with water loss from the soil by evaporation only. Under such gardening conditions, the most suitable trees to be planted include Acacia auriculiformis, Butea monosperma, Casuarina equisetifolia, Cochlospermum religiosum, Eucalyptus citriodora, Heritiera macrophylla, Inga dulcis, Parkinsonia aculeata, Pongamia pinnata, Samanea saman, Tamarindus indica, Tamarix articulata, Terminalia arjuna, and Thespesia populnea.

3.1.6 Ornamental Trees Diversified for Avenue Plantation in Narrow Roadsides

Most sub-roads, streets and lanes in urban areas are decorated with ornamental trees bearing the characteristics of a less horizontal spreading canopy area and lesser height. The most suitable plants for these sites include Callistemon citrinus, Cassia javanica, Cassia nodosa, Cassia renigera, Grevillea robusta, Ixora parviflora, Jacaranda mimosifolia, Juniperus chinensis, Melia azadirachta, Nyctanthes arbortristis, Podocarpus elongata, Polyalthia pendula, and Putranjiva roxburghii.

3.1.7 Ornamental Trees Diversified for Avenue Plantation in Wide Roadsides

For beautification, wide roadsides, such as those of national or state highways, are planted with tall and wider-spreading trees such as Alstonia scholaris, Alstonia macrophylla, Anthocephalus cadamba, Bauhinia blakeana, Bauhinia purpurea, Bombax ceiba, Bombax ellipticum, Butea monosperma, Casuarina equisetifolia, Ceiba pentandra, Couroupita guianensis, Cassia fistula, Cassia spectabilis, Delonix regia, Erythrina indica, Ficus bengalensis, Ficus benjamina, Ficus religiosa, Lagerstroemia flosreginae, Lagerstroemia speciosa, Lagerstroemia thorellii, Michelia champaca, Mimusops elengi, Peltophorum ferrugineum, Pongamia pinnata, Polyalthia longifolia, Pinus longifolia, Plumeria lutea, Plumeria obtusa, Salix babylonica, Saraca asoca, Spathodia campanulata, Tabebuia chrysantha, Tabebuia avellanedae, Tabebuia palmeri, Tabebuia rosea, Tecoma gaudichaudi, Thevetia peruviana, and Thespesia populnea.

3.1.8 Ornamental Specimen Trees Diversified in Gardening

Some trees having a special shape or attractive foliage or flowers are placed in a corner or at a road junction or on a lawn to bring the attention of visitors to enjoy their beauty, including Araucaria cooki, Couroupita guinensis, Diospyros peregrina, Ficus bengalensis var. variegata, Ficus benjamina var. variegata, Ficus elastica, Kigelia pinnata, Magnolia grandiflora, Mimusops elengi var. variegata, Pterogata alata var. diversifolia, and Plumeria alba.

3.1.9 Ornamental Screening Trees Diversified in Gardening

Some tall trees grow horizontally with dense foliage and are planted with close spacing in the garden to make a screen for a windbreak as well as to cover views of ugly spots. The most suitable plants used in a garden are Eucalyptus spp., Grevillea robusta, Polyalthia pendula, Populus spp., and Putranjiva roxburghii.

3.1.10 Ornamental Trees Diversified in the Garden Based on Season of Flowering

Every garden should have a colorful attactiveness that continues year round. Permanent beautification in the garden is only possible by proper planning with plantation of ornamental flowering trees. The flowering trees listed following are diversified in various types of gardens, in which flowers emerge in different seasons in nature, and these trees are planted in different tropical and subtropical gardens.

3.1.10.1 Spring Season Blooming

Included are Amherstia nobilis, Barringtonia acutangula, Barringtonia racemosa, Bauhinia variegata, Bombax ceiba, Brownea arisa, Brownea coccinea, Brownea grandiceps, Brownea hybrida, Brownea macrophylla, Cassia siamea, Castanospermum australe, Cochlospermum religiosum, Gliricidia maculata, Jacaranda mimosifolia, Milletia ovalitolia, Saraca asoca, Saraca thaipingensis, Spathodea campanulata, Tabebuia avellanedae, Tabebuia chrysantha, Tabebuia palmeri, and Tabebuia rosea.

3.1.10.2 Summer Season Blooming

Included are Bignonia crispa, Calophyllum inophyllum, Cassia fistula, Cassia spectabilis, Cassia lancasteri, Cassia moschata, Cassia grandis, Cassia javanica, Cassia nodosa, Cassia renigera, Delonix regia, Erythrina indica, Gardenia indica, Gardenia latifolia, Jacaranda mimosifolia, Kigelia pinnata, Lagerstroemia flosreginae, Lagerstroemia speciosa, Magnolia grandiflora, Magnolia pterocarpa, Michelia champaca, Ochna squarrosa, Peltophorum ferrugineum, and Poinciana regia.

3.1.10.3 Rainy Season Blooming

Included are Anthocephalus cadamba, Brassaia actinophylla, Callicarpa lantana, Cananga odoratum, Cassia marginata, Colvillea racemosa, Hibiscus collinus, Lagerstroemia thorellii, Millingtonia hortensis, Plumeria alba, and Plumeria rubra.

3.1.10.4 Autumn Season Blooming

Included are Acacia auriculiformis, Chorisia speciosa, and Nyctanthes arbortristis.

3.1.10.5 Winter Season Blooming

Included are Bauhinia purpurea, Monodora grandiflora, and Sesbania grandiflora.

3.1.10.6 Ever-Blooming

Included are Caesalpinia pulchirima, Callistemon lanceolatus, Callistemon pollandi, Cordia sebestena, Kleinhovia hospita, Mimusops elengi, Plumeria spp., and Thespesia populnea.

3.1.11 Ornamental Trees Diversified in the Garden Based on Colour of Flower

A garden should have more flowering plants than foliage plants. The colour combination of the ornamental trees in the garden is most important for the greatest beauty. Many plants are used in various gardens based on their flower colours and season of flowering. Some gardens use specific colours of flowers, such as a cemetery garden beautified with white or cream-coloured flowering trees. Following are some ornamental trees in different parts of the world summarized on the basis of their colour or flower diversity.

3.1.11.1 White Coloured Flower Ornamental Trees

Alstonia scholaris, Baikiaea insignis,Cerbera manghas, Magnolia pterocarpa, Millingtonia hortensis, Plumeria accuminata, Plumeria obtusa.

3.1.11.2 Yellow Coloured Flower Ornamental Trees

Acacia auriculiformis, Bauhinia tomentosa, Caesalpinia pulcherima, Cassia fistula, Cassia moschata, Cassia spectabilis, Cochlospermum religiosum, Markhamia platycalyx, Peltophorum pterocarpum, Saraca thaipingensis, Tabebuia chrysantha.

3.1.11.3 Creamy or White Coloured Flower Ornamental Trees

Albizia chinensis, Albizia lebeck, Bombax ellipticum var. album, Crescentia cujete, Madhuca indica, Magnolia grandiflora, Michelia champaca, Mimusops elengi, Plumeria lutea, Pterospermum acerifolium, Terminalia arjuna, Thevetia peruviana.

3.1.11.4 Greenish-Yellow Coloured Flower Ornamental Trees

Caesalpinia cacalaco, Duabanga sonneratioides, Monodora grandiflora, Cananga odorata.

3.1.11.5 Red Coloured Flower Ornamental Trees

Amherstia nobilis, Bombax ceiba, Cassia marginata, Delonix regia, Erythrina variegata, Plumeria rubra, Saraca asoca, Schotia latifolia.

3.1.11.6 Scarlet Coloured Flower Ornamental Trees

Barringtonia acutangula, Brownea ariza, Poinciana regia, Erythrina blachei, Callistemon lanceolatus.

3.1.11.7 Pink Coloured Flower Ornamental Trees

Bauhinia monandra, Bombax ellipticum, Cassia javanica, Cassia renigera, Gliricidia sepium, Kleinhovia hospita.

3.1.11.8 Purple Coloured Flower Ornamental Trees

Bauhinia purpurea, Melia azedarach, Tabebuia rosea.

3.1.11.9 Orange Coloured Flower Ornamental Trees

Cordia sebestena.

3.1.11.10 Orange-Red Coloured Flower Ornamental Trees

Butea monosperma, Colvillea racemosa, Spathodea campanulata.

3.1.11.11 Blue Coloured Flower Ornamental Trees

Guaiacum officinale, Jacaranda acutifoilia, Millettia ovalifolia, Solanum grandiflorum.

3.1.11.12 Mauve or Violet Coloured Flower Ornamental Trees

Lagerstroemia speciosa, Lagerstroemia thorelli.

3.1.12 Ornamental Trees Diversified in the Garden Based on Foliage Beauty

Colourful foliage and various leaf shapes enrich the beauty of a garden. Also, dense foliage provides shade and acts as an air conditioner in the garden during summer. Similarly, foliage works as an umbrella in the monsoon, and some deciduous trees look very pretty when defoliated during the dormancy period, which happens especially during the winter season, when people can enjoy sunlight when sitting underneath the tree while enjoying the beauty of the garden. Some attractive foliage plants listed next, based on their importance in gardens in different zones in the world, include Acer campbellii, Adansonia digitata, Albizia lebeck, Alstonia scholaris, Alstonia macrophylla, Arucaria cookii, Artocarpus altalis, Azadirachta indica, Brassaia actinophylla, Callistemon citrinus, Callistemon pollandi, Calophyllum inophyllum, Casuarina equisetifolia, Couroupita guianensis, Diospyros peregrina, Eugenia operculata, Eugenia jambolana, Ficus bengalensis, Ficus benjamina var. variegata, Ficus bengalensis var. Krishnee, Ficus elastica, Ficus religiosa, Ficus rumphii, Filicium decipiens, Grevillea robusta, Grewia columnaris, Ixora parviflora, Kegelia pinnata, Mimusops elengi, Mimusops elengi var. variegata, Parkia roxburghii, Pinus longifolia, Podocarpus macrophylla, Polyalthia longifolia, Polyalthia pendula, Pterospermum acerifolium, Putranjiva roxburghii, Pterygota alata var. diversifolia, Ravenala madagascariensis, Salix babylonica, Samanea saman, Santalum album, Sterculia alata, Tamarix chinensis, Tamarix ramossiana, Taxodium distichum, Taxus baccata, Terminalia catappa, Thespesia populnea, and Thuja orientalis.

3.1.13 Ornamental Trees Diversified in the Garden Based on Agro-Climatic Zones

3.1.13.1 Tropical Zones and Subtropical Zones

Acacia auriculiformis, Acacia decurrens, Adansonia digitata, Albizia lebeck, Alstonia scholaris, Alstonia macrophylla, Anthocephalus cadamba, Araucaria cookii, Araucaria cunninghamii, Araucaria heterophylla, Artocarpus altalis, Azadirachta indica, Baringtonia acutangula, Baringtonia racemosa, Baikiaea insignis, Bauhinia blakeana, Bauhinia purpurea, Bauhinia variegata, Bombax ceiba, Bombax ellipticum, Brassaia actinophylla, Brownea arisa, Brownea coccinea, Brownea grandiceps, Brownea hybrida, Brownea macrophylla, Butea monosperma, Cassia fistula, Cassia spectabilis, Casuarina equisetifolia, Ceiba pentandra, Chorisia speciosa, Couroupita guianensis, Callistemon citrinus, Callistemon pollandi, Calophyllum inophyllum, Caesalpinia cacalaco, Cananga odorata, Careya arborea, Cassia grandis, Cassia lancasteri, Cassia marginata, Cassia moschata, Cassia nodosa, Cassia renigera, Cassia javanica, Castanospermum australe, Cochlospermum religiosum, Colvillea racemosa, Cordia sebestena, Crescentia cujete, Delonix regia, Diospyros peregrina, Duabanga sonneratioides, Erythrina indica, Eugenia operculata, Eugenia jambolana, Ficus bengalensis, Ficus benjamina var. variegata, Ficus bengalensis var. Krishnee, Ficus religiosa, Ficus rumphii, Ficus elastica, Filicium decipiens, Gardenia latifolia, Gustavia augusta, Grevillea robusta, Grewia columnaris, Heterophragma adenophyllum, Ixora parviflora, Jacaranda mimosifolia, Kigellia pinnata, Lagerstroemia flosreginae, Lagerstroemia speciosa, Lagerstroemia thorellii, Mesua ferrea, Michelia champaca, Mimusops elengi, Mimusops elengi var. variegata, Magnolia grandiflora, Magnolia pterocarpa, Mimusops elengi var. variegata, Millettia peguensis, Monodora grandiflora, Napoleona imperialis, Nauclea orientalis, Nyctanthes arbortristis, Parkia roxburghii, Plumeria lutea, Plumeria obtuse, Podocarpus macrophylla, Polyalthia pendula, Polyalthia longifolia, Pterospermum acerifolium, Putranjiva roxburghii, Pterygota alata var. diversifolia, Putranjiva roxburghii, Pachira cyathophora, Parkinsonia aculeate, Plumeria rubra, Ravenala madagascariensis, Salix babylonica, Samanea saman, Saraca thaipingensis, Santalum album, Saraca asoca, Spathodia campandulata, Sterculia alata, Taxodium distichum, Tabebuia avellanedae, Tabebuia chrysantha, Tabebuia palmeri, Tabebuia rosea, Tecoma gaudichaudi, Thevetia peruviana, Terminalia catappa, Thespesia populnea, Thuja orientalis, Tipuana tipu, Wrightia tomentosa.

3.1.13.2 Temperate Zones

Acer campbellii, Arucaria cunninghamii, Arucaria heterophylla, Bauhinia spp., Citharexylum quadrangulare, Pinus longifolia, Pyrus persica, Rhodendron spp., Tamarix chinensis, Tamarix ramossiana, Taxus baccata, Ulmus alata.

3.2 Biodiversity of Ornamental Shrubs

Shrubs are woody and semi-woody pennenial plants growing to a height of 4 m. Some are dwarf and bushy, making excellent groundcover when used in a shrubbery border around the lawn area of a garden or in a shrubbery beside a road and sub-road or paths. For garden beautification, ornamental shrubs have special characteristics such as attractive shape, colorful foliage or various cheerful colours or fragrance. A huge number of shrubs have been diversified throughout the world for decoration of different gardens on the basis of such special characteristics as size and shape of plants, growth habit, growing locations, and colour of foliage and flowers with or without fragrance. The major work on biodiversity of ornamental shrubs has been done by amateur garden lovers and nursery plant growers. Many clusters of nursery-based enterprises have been developed for ornamental plant production around urban areas. These entrepreneurs brought different varieties of rare and uncommon shrub species from abroad, collected for years as mother plant stock or genetic resources, followed by propagation for sale at high prices. Some important ornamental plants from the world’s diversity are described here (Table 2).

Table 2 List of ornamental shrub species biodiversity in the world

3.2.1 Flowering Shrubs Diversified in Tropical and Subtropical Regions for Beautification of Shrubbery Borders

Acokanthera spetabilis, Abelia chinensis, Abutilon darwinii, Abutilon hybridum, Angelonia angustifolia, Angelonia grandiflora, Aphelandra sinclairiana, Asclepias curassavica, Asystasia chelonoides, Asystasia gangetica, Barleria prionites, Barleria strigosa, Bauhinia acuminata, Bauhinia galpinii, Bauhinia tomentosa, Beloperone amherstae, Beloperone guttata, Brunfelsia americana, Brunfelsia calycina, Brunfelsia undulata, Buddleia asiatica, Buddleia davidii, Buddleia lindleyana, Caesalpinia gillwsii, Caesalpinia pulcherrima, Calliandra brevipes, Calliandra emarginata, Calliandra haematocephala, Calliandra houstonii, Calliandra hybrida, Calliandra protoricensis, Calliandra tweedii, Callicarpa cana, Callistemon lanceolatus, Cananga kirkii, Canthium glabrum, Capparis spinosa, Caryopteris mascanthus, Cassia alata, Cassia bicapsularis, Cassia glauca, Cassia laevigata, Catesbaea spinosa, Cerbera fruticosa, Cestrum aurantiacum, Cestrum diurnum, Cestrum elegans, Cestrum parqui, Cestrum nocturnum, Clerodendron fragrans, Clerodendron macrosiphon, Clerodendron paniculatum, Clerodendron phlomidis, Clerodendron siphonanthus,Crossandra undulaefolia, Cuphea hyssopifolia, Cuphea melvillea, Cuphea miniata, Datura fastuosa, Datura suaveolens, Daedalacanthus macrophyllus, Daedalacanthus nervosus, Dombeya mastersii, Dombeya natalensis, Dombeya wallichii, Erythrina blakei, Erythrina cristagalli, Erythrina resupinata, Euphorbia fulgens, Gardenia jasminoides, Gardenia longistyla, Gardenia lucida, Gardenia radicans, Galphimia gracilis, Gmelina asiatica, Gustavia insignis, Hamiltonia suaveolens, Hibiscus mutabilis, Hibiscus rosa-sinensis, Hibiscus schizopetalus, Hibiscus syriacus, Hydrangea macrophylla, Ichroma tululosum, Ixora acuminate, Ixora barbata, Ixora coccinea, Ixora duffii, Ixora hybrid, Ixora lutea, Ixora macrothyrsa, Ixora singaporensis, Ixora superba, Jacobinia carnea, Jasminum humile, Jasminum pubescens, Jatropha panduraefolia, Justicia aurea, Justicia ovate, Lagerstroemia lancasteri, Lantana camara, Lantana sellowiana, Leea alata, Ligustrum robustum, Magnolia mutabilis, Magnolia pumila, Malvaviscus arboreus, Melastoma malabathricum, Memecylon edule, Memecylon ellipticum, Mussaenda erythrophylla, Mussaenda frondasa, Nerium odoratum, Nerium oleander, Ochna kirkii, Ochna squarrosa, Oncoba spinosa, Pachystachys lutea, Pentas karmesiana, Petrea arborea, Plumbago indica, Pogonopus exsertus, Pootia grandiflora, Portlandia grandiflora, Posoqueria latifolia, Quassia amara, Randia macrantha, Randia maculata, Reinwardtia trigyna, Rondeletia odorata, Ruellia lorenziana, Ruellia rosea, Russelia juncea, Russelia sarmentosa, Ruttya fruticosa, Sambucus canadensis, Sarcocephales cordatus, Stachytarpheta indica, Stachytarpheta mutabilis, Stemmadenia bella, Streptosolen jamesoni, Strobilanthus glomeratus, Strobilanthus dichotomous, Strobilanthus wallichii, Tabernae montana coronaria, Tabernae montana dichotoma, Tarenna zeylanica, Tecoma gaudichaudi, Tecoma stans, Tecomaria capensis, Thryallis glauca, Thunbergia hybrida, Turnera ulmifolia, Vitex agnuscastus, Woodfordia floribunda, Wormia burbidgii.

3.2.2 Flowering Shrubs Diversified in Tropical and Subtropical Regions for Beautification of Hedges and Edges

Acalypha hispida, Allamanda nerifolia, Allamanda schottii, Barleria cristata, Clerodendron inerme, Hamelia patens, Ixora chinensis, Jasminum sambac, Lagerstroemia indica, Murrya exotica, Pentas lanceolata, Plumbago auriculata, Ravenia spectabilis, Thunbergia erecta, Vinca rosea.

3.2.3 Foliage Shrubs Diversified in Tropical and Subtropical Regions for Beautification of Shrubbery Borders

Acalypha godseffina, Acalypha williksiana, Alternanthera amoena, Alternanthera bettzickiana, Alternanthera dentate, Alternanthera versicolor, Aralia spp., Brya ebenus, Evordia elegans, Cordium variegatum, Coleus blumei, Coleus rehneltianus, Duranta repens, Duranta lorentzii, Eranthemum albo-marginatum, Eranthemum bicolor, Eranthemum laxiflorum, Eranthemum nigram, Eranthemum tricolor, Euphorbia cotinifolia, Evodia elegans, Excoecaria bicolour, Ficus triangularis, Graptophyllum pictum, Jacquinia ruscifolia, Jatropha podagrica, Lawsonia inermis, Malphigia coccigera, Malphigia glabra, Manihot esculenta ‘Variegata’, Muehlenbeckia platyclada, Murraya paniculata, Mussaenda erythrophylla, Mussaenda frondosa, Mussaenda luteola, Mussaenda philippica, Nandina domestica, Nandina nivosus, Phyllanthus spp., Poinsettia heterophylla, Poinsettia leucocephala, Poinsettia pulcherrima, Polyscias balfouriana, Polyscias filicifolia, Polyscias fruticosa, Polyscias guilfoylei, Polyscias paniculata, Polyscias scutellaria, Pseudoeranthemum alatum, Pseudoeranthemum atropurpureum, Pseuderanthemum reticulatum, Pseuderanthemum sinuatum, Sanchezia nobilis, Serissa foetida, Strobilanthes dyerianus, Thuja compacta.

3.2.4 Foliage Shrubs Diversified in Tropical and Subtropical Regions for Beautification of Hedges and Edges

Acalypha godseffiana, Alternanthera amoena, Alternanthera bettzickiana, Alternanthera dentate, Alternanthera versicolor, Aralia spp., Duranta repens, Eranthemum bicolor, Phyllanthus spp., Polyscias balfouriana, Polyscias filicifolia, Polyscias fruticosa.

3.2.5 Flowering Shrubs Diversified in Temperate Regions for Beautification of Shrubbery Borders and Hedges

Azalia spp., Camelia spp., Hydrangia spp., etc.

3.2.6 Foliage Shrubs Diversified in Temperate Regions for Beautification of Shrubbery Borders and Hedges

Iresine herbstii, Juniperus chinenesis, Thuja compacta, etc.

3.3 Biodiversity of Ornamental Climbers and Creepers

Climbers are grown throughout the world for the beautification of garden features such as covering arches, pergolas, bowers, walls and topiary work. Also, some sweet-scented flowering climbers have been grown for commercial use in the perfumery industry in the private or public sector. These kinds of plants are now mostly handled by nursery growers and some public institutes, conserved, domesticated and promoted to plant lovers or farmers or nursery growers. Some important climbers are listed next (Table 3), based on their uses in garden decoration and colour variability.

Table 3 List of climbers and creepers species biodiversity in the world

3.3.1 Classification Based on Importance of Garden Beautification

3.3.1.1 Pergola Decoration

Derris scandens, Faradaya splendida, Quisqualis indica etc.

3.3.1.2 Arch Decoration

Clitoria spp., Petrea volubilis, Pyrostegia venusta, Quisqualis indica, Thunbergia mysorensis, etc.

3.3.1.3 Arch and Wall Decoration

Adenocalymma comosum, Anemopaegma chamberlaynii, etc.

3.3.1.4 Wall and Pillars

Allamanda violacea, Ficus pumila, Ipoemea spp., etc.

3.3.1.5 Arch, Wall, Pillar and Porch

Allamanda cathartica, Bougainvillea spp., Clerodendrum splendens, Pseudocalymma alliaceum, Stictocardia tilifolia, Wisteria sinensis, etc.

3.3.1.6 Pergola and Wall

Amphilophium mutisii, Aristolochia elegans, Banisteria laevifolia, Camoensia maxima, Clerodendrum thomsonae, Odontadenia grandiflora, Phaedranthus buccinatoria, Rhynchodia wallichii, Strophanthus gratus, etc.

3.3.1.7 Arch and Pergola

Antigonon guatemalense, Antigonon leptopus, Aristolochia grandiflora, Aristolochia ornithocephala, Beaumontia grandiflora, Clematis flammula, Clematis gouriana, Combretum coccineum, Combretum decandrum, Lonicera sempervirens, Melodinus monogynous, Passiflora caerulea, Passiflora spp., Thunbergia grandiflora, etc.

3.3.1.8 Wall and Fence

Capparis horrida, Clitoria ternatea, Pandorea jasminoides, Podranea ricassoliana, Senecio confusus, Stephanotis floribunda, Thunbergia laurifolia, Trachleospermum jasminoides, Vernonia elaeagnifolia, etc.

3.3.1.9 Trellis and Fence

Clytostoma callistegioides, Clytostoma purpureum, Dioclea glycinoides, Echites caryophyllata, Ipoemea spp., Lonicera confusa, Lonicera japonica, Passiflora spp., Quamoclit coccinea, etc.

3.3.2 Classification Based on Colour of Flower

3.3.2.1 White Colour Flower

Antigonon leptopus, Bauhinia diphylla, Bauhnia vahlii, Beaumontia grandiflora, Bougainvillea spp., Camoensia maxima, Capparis horrida, Cardiospermum halicacabum, Chonemorpha macrophylla, Clematis flammula, Clematis gouriana, Clerodendrum thomsonae, Cryptostegia madagascariensis, Derris scandens, Echites caryophyllata, Faradaya splendida, Hiptage madablota, Hoya bella, Jasminum angustifolium, Jasminum auriculatum, Jasminum flexile, Jasminum grandiflorum, Jasminum nitidum, Jasminum officinale, Lonicera confusa, Lonicera japonica, Melodinus monogynous, Passiflora edulis, Pithecoctenium cynchoides, Porana paniculata, Stephanotis floribunda, Strophanthus grandiflorus, Strophanthus gratus, Tetracera sarmentosa, Thunbergia alata, Thunbergia fragrans, Trachleospermum jasminoides, etc.

3.3.2.2 Yellow Colour Flower

Adenocalymma comosum, Allamanda cathartica, Anemopaegma chamberlaynii, Aristolochia elegans, Banisteria laevifolia, Bougainvillea spp., Cissus discolor, Clytostoma callistegioides, Doxantha unguiscati, Ipomoea tuberosa, Odontadenia grandiflora, Rhynchodia wallichii, Solandra nitida, Stigmaphyllon ciliatum, Stigmaphyllon periplocifolium, Tristellateia australis, etc.

3.3.2.3 Greenish White Colour Flower

Ipomoea bonanox.

3.3.2.4 3.3.2.4. Greenish-Yellow Colour Flower

Aristolochia tomentosa, Artabotrys odoratissimus, Pergularia odoratissimus, etc.

3.3.2.5 Purple Colour Flower

Allamanda violacea, Amphilophium mutisii, Aristolochia grandiflora, Aristolochia ornithocephala, Aristolochia ringens, Hoya imperialis, Ipomoea palmata, Ipomoea pescaprae, Ipomoea purpurea, Ipomoea rubro-caerulea, Podranea ricasoliana, etc.

3.3.2.6 Purplish-Violet Colour Flower

Arrabidaea magnifica, Clytostoma purpureum, Cobaea scandens, Ipomoea learii, Wisteria sinensis, etc.

3.3.2.7 Rosy-Purple Colour Flower

Argyreia nervosa, Bougainvillea spp., Thunbergia mysorensis, etc.

3.3.2.8 Rosy-Pinky Colour Flower

Pandorea jasminoides.

3.3.2.9 Reddish-Purple Colour Flower

Crytostegia grandiflora, Gloriosa rothschildiana.

3.3.2.10 Blue Colour Flower

Clitoria ternatea, Jacquemontia violacea, Passiflora caerulea, Solanum wendlandii, Thunbergia grandiflora, Thunbergia laurifolia, etc.

3.3.2.11 Mauve Colour Flower

Passiflora violacea, Petrea volubilis, Pseudocalymma alliaceum, etc.

3.3.2.12 Pink Colour Flower

Antigonon leptopus, Bougainvillea spp., Hoya carnosa, Quisqualis densiflora, Quisqualis indica, etc.

3.3.2.13 Orange Colour Flower

Campsis grandiflora, Campsis radicans, Pyrostegia venusta, etc.

3.3.2.14 Orange-Red Colour Flower

Combretum coccineum, Combretum decandrum, Gloriosa superba, Holmskioldia sanguine, Quamoclit coccinea, Senecio confusus, etc.

3.3.2.15 Crimson Red Colour Flower

Phaedranthus buccinatoria, and Stictocardia tilifolia.

3.3.2.16 Scarlet Orange Colour Flower

Lonicera sempervirens.

3.3.2.17 Scarlet Red Colour Flower

Clerodendrum splendens, Dioclea glycinoides, Passiflora coccinea, Passiflora quadrangularis, etc.

3.4 Biodiversity of Ornamental Palms

The ornamental palms of the world have a vital role in gardening, either outside or indoors, and most of these palms originated in tropical and subtropical zones. Tall palms are used for roadside beautification; small palms are grown in pots, and bushy palms are planted in gardens by a wall. The important palms used in gardening worldwide are listed below (Table 4).

Table 4 List of palm species biodiversity in the world

3.4.1 Classification Based on Gardening

3.4.1.1 Indoor Gardening

Acoelorrhaphe wrightii, Actinorhytis calapparia, Adonidia merrillii, Areca nagensis, Areca triandra, Arenga engleri, Arenga porphyrocarpa, Asterogyne martiana, Balaka seemannii, Bentinckia condapanna, Butia paraguayensia, Butia yatay, Chamaedorea adscendens, Chamaedorea arenbergiana, Chamaedorea brachypoda, Chamaedorea cataractarum, Chamaedorea costaricana, Chamaedorea elegans, Chamaedorea metallica, Chamaedorea seifrizii, Chambeyronia macrocarpa, Coccothrinax argentata, Cryosophila warscewiczii, Cyrtostachys renda, Dypsis albo-farinosa, Dypsis lutescens, Dypsis madagascariensis, Elaeis guineensis, Howea forsteriana, Hyophorbe lagenicaulis, Latania lontaroides, Latania verschaffeltii, Licuala grandis, Licula paludosa, Licuala peltata, Licuala ramsayi, Licuala spinosa, Livistonia australis, Livistonia chinensis, Livistonia jenkinsiana, Livistonia rotundifolia, Pelagodoxa henryana, Phoenicophorium borsiganum, Phoenix roebelinii, Phoenix rupicola, Pinanga adangensis, Pinanga coronate, Pinanga dicksonii, Pritchardia pacifica, Ptychosperma elegans, Ptychosperma furcatum, Ptychosperma lineare, Ptychosperma macarthurii, Ptychosperma propinquum, Ravenea rivularis, Rhapis excels, Rhapis humilis, Reinhardtia gracilis, Roscheria melanochaetes, Sabal barmundana, Serenoa repens, Thrinax excelsa, Thrinax parviflora, Thrinax radiate, Wallichia caryotoides, Wallichia densiflora.

3.4.1.2 Outdoor Gardening

Acrocomia aculeate, Aiphanes aculeate, Aiphanes minima, Archontophoenix alexandrae, Archontophoenix cunninghamiana, Archontophoenix myolensis, Areca catechu, Areca catechu cv. alba, Areca catechu cv. dwarf, Areca concinna, Areca macrocalyx, Areca nagensis, Areca vestiaria, Arenga caudate, Arenga hookeriana, Arenga microcarpa, Arenga obtusifolia, Arenga pinnata, Arenga tremula, Arenga undulatifolia, Arenga westerhoutii, Arenga wightii, Astrocaryum alatum, Astrocaryum maxicanum, Attalea allenii, Attalea cohune, Bactris grasipaes, Bactris major, Bentinckia nicobarica, Brahea aculeate, Brahea edulis, Brahea aculeata, Calamus arborescens, Calyptrocalyx spicatus, Calyptrogyne ghiesbreghtiana, Calyptronoma plumeriana, Carpentaria acuminate, Caryota mitis, Chamaedorea arenbergiana, Chamaerops humilis, Cocos nucifera, Copernicia bailyana, Copernicia brittonorum, Copernicia gigas, Copernicia hospita, Copernicia macroglossa, Copernicia prunifera, Corypha utan, Corypha umbraculifera, Daemonorops jenkinsiana, Dictyosperma album, Drymophloeus hentyi, Dypsis cabadae, Dypsis decaryi, Dypsis lastelliana, Dypsis leptocheilos, Dypsis lutescens, Elaeis oleifera, Euterpe edulis, Gaussia maya, Heterospathe elata, Hydriastele microspadix, Hyophorbe lagenicaulis, Hyophorbe verschaffeltii, Hyphaene coriacea, Kerriodoxa elegans, Latania loddigesii, Livistonia decora, Livistonia muelleri, Loxococcus rupicola, Nannorrhops ritchiana, Normanbya normanbyi, Nypa fruticans, Oncosperma tigillarium, Phoenix paludosa, Pritchardia thurstonii, Pscudophoenix ekmanii, Rhopaloblaste augusta, Roystonea borinquena, Roystonea oleracea, Roystonea regia, Sabal “riverside,” Salacca zalacca, Satakentia liukiuensis, Schippia concolor, Syagrus cearensis, Trachycarpus fortune, Trachycarpus martianus, Trachycarpus takil, Veitchia arecina, Veitchia joannis, Veitchia winin, Verschaffeltia splendida, Wallichia disticha, Washingtonia filifera, Washingtonia robusta, Woodytia bifurcata.

3.5 Biodiversity of Ornamental Ferns

Ferns, one of the most important graceful foliage ornamental plants, are grown in a wide range of climate, about 2120 species in shaded and semi-shaded areas on the ground worldwide. Almost all ferns like to grow in hilly areas in subtropical zones. Now, many ferns domesticated in the plains are used for house plants by growing them in pots or beds in the garden or cut foliage. Ferns look very beautiful when grown in a group in the garden. The most important ferns having ornamental value for garden beautification and indoor gardening include Adiantum, Asplenium, Blechnum, Crytomium, Davallia, Dicksonia, Doryopteris, Nephrolepis, Pityrogramma, Platycerium, Polypodium, Polystichum, and Pteris spp.

3.6 Biodiversity of Ornamental Cacti and Succulents

More than 5000 species of this group of plants mostly inhabit dry and arid habitats or a red lateritic belt. The most suitable genera with available species of cacti and succulents of the world are described by Bose et al. (2008) and listed below (Tables 5 and 6), but some of them are brought year after year and domesticated, multiplied and established in gardens by private and government sectors.

Table 5 List of cactus species biodiversity in the world

Table 6 List of succulent species biodiversity in the world

3.7 Biodiversity of Ornamental Grasses

Grasses have a vital role for beautification of gardens in the world, specially in lawn development, and now these are used commercially as turf in playgrounds. The many grasses diversified all over the world, as based on seasonal growing, are reported by Tiwari et al. (2015).

3.7.1 Warm Season Grasses

Axonopus affinis, Axonopus aureus, Axonopus compressus, Axonopus fissifolius, Axonopus furcatus, Buchloe dactyloides, Cynodon dactylon, Eremochloa ciliaris, Pennisetum clandestinun, Paspalum notatum, Paspalum vaginatum, Stenotaphrum secundatum, Zoysia japonica, Zoysia tenuifolia.

3.7.2 Cool Season Grasses

Agrostis palustris, Agrostis tenuis, Festuca ovina, Festuca rubra, Lolium multiflorum, Poa annua, Poa perenne, Poa pratensis, Poa trivialis.

3.8 Biodiversity of Ornamental House Plants

Most of the house plants of the world are grown under the forest canopy in tropical and subtropical zones in shaded and semi-shaded locations. It is important to realize that people in cities want to feel closer to nature by establishment of indoor gardening, and now the demand is increasing day by day in response to rapid urbanization. Some of the species available worldwide that are used for beautification of home gardens, indoor gardens, and public gardens, etc., are listed below (Table 7).

Table 7 List of indoor gardening plant species biodiversity in the world

3.8.1 Classification Based on Light Requirement

3.8.1.1 Moderate Light to Full Filtered Sunlight

Aechmea spp., Chlorophytum bichetii, Dracaena deremensis, Dracaena fragrans, Dracaena godseffiana, Ficus benjamina, Ficus cyathispula, Ficus diversifolia, Ficus elastica, Ficus nitida, Ficus triangularis, Ficus triangularis ‘Variegata’, etc.

3.8.1.2 Full Filtered Sunlight

Aeschynanthus spp., Anthurium crystallinum, Anthurium forgetii, Anthurium magnificum, Anthurium pedato-radiatum, Anthurium scherzerianum, Asparagus densiflorus, Asparagus plumosus, Asparagus setaceus, Fittonia verschaffeltii, Guzmania lingulata ‘Major’, Guzmania lingulata ‘Minor’, Leea rubra, Oxalis hedysaroides rubra, etc.

3.8.1.3 Moderate Filtered Sunlight

Aglaonema spp., Alocasia spp., Begonia spp., Bilbergia spp., Bromelia balansae, Bromelia serra, Chrysothemis pulchella, Dianella tasmanica, Hypocyrta glabra, Impatiens linearfolia, Medinilla magnifica, Tillandsia spp., etc.

3.8.1.4 Direct Sunlight

Alpinia zerumbet, Ananas bracteatus, Costus speciosus ‘variegata’, Pandanus baptistii, Pleomele reflexa, Sansevieria cylindrica, Sansevieria guineensis, Sansevieria trifasciata, Stanotaphrum secandatum ‘Variegatum,’ etc.

3.8.1.5 Partial Shade

Aphelandra squarrosa, Aspidistra elatior, Calathea spp., Callisia repens, Cordyline terminalis, Cryptanthus bivittatus, Cryptanthus bromelioides, Cryptanthus ‘Golden green’, Episcia spp., Heliconia spp., Hemigraphis colorata, Hoffmannia refulgens, Pellonia daveauana, Peperomia spp., Phalaris arundinaceae, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Ruellia devosiana, Saintpaulia ionantha, Schefflera arboricola variegata, Spathiphyllum clevelandii, Tradescantia albiflora, Tradescantia fluminensis, Vriesea spp., Xanthosoma lindenii, Zebrina pendula ‘Rubra’, etc.

3.8.1.6 Partial Shade or Shade

Ctenanthe lubbersiana, Cyclanthus bipartitus, Dieffenbachia spp., Euonymous japonica, Hedera helix, Homalomena spp., Kaempferia pulchra, Maranta arundinacea, Monstera deliciosa, Monstera oblique, Neoregelia carolinae, Nidularium innocentii, Pelargonium spp., Pilea serpyllacea, Pleomele angustifolia, Schefflera venulosa, Scindapsus spp., Stromanthe sanguine, Syngonium podophyllum variegatum, Taccca chantrieri, etc.

3.8.2 Classification Based on Importance of Plant Parts

3.8.2.1 Foliage Beauty

Aglaonema spp., Alocasia spp., Alpinia zerumbet, Ananas bracteatus, Anthurium crystallinum, Anthurium forgetii, Anthurium magnificum, Anthurium pedato-radiatum, Anthurium scherzerianum, Asparagus densiflorus, Asparagus plumosus, Asparagus setaceus, Aspidistra elatior, Billbergia spp., Calathea spp., Chlorophytum bichetii, Cordyline terminalis, Cryptanthus bivittatus, Cryptanthus bromelioides, Cryptanthus ‘Golden green’, Ctenanthe lubbersiana, Cyclanthus bipartitus, Dianella tasmanica, Dieffenbachia spp., Dracaena deremensis, Dracaena fragrans, Dracaena godseffiana, Euonymous japonica, Ficus benjamina, Ficus cyathistipula, Ficus diversifolia, Ficus elastica, Ficus nitida, Ficus triangularis, Ficus triangularis ‘Variegata’, Fittonia verschaffeltii, Hedera helix, Hemigraphis colorata, Homalomena spp., Leea rubra, Maranta arundinacea, Monstera deliciosa, Monstera oblique, Neoregelia carolinae, Neoregelia carolinae, Neoregelia carolinae, Nidularium innocentii, Oxalis hedysaroides rubra, Pandanus baptistii, Pelargonium spp., Pellionia daveauana, Peperomia spp., Phalaris arundinaceae, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Pilea serpyllacea, Pleomele angustifolia, Pleomele reflexa, Ruellia devosiana, Sansevieria cylindrica, Sansevieria guineensis, Sansevieria trifasciata, Schefflera arboricola variegata, Schefflera venulosa, Scindapsus spp., Stanotaphrum secandatum variegatum, Stromanthe sanguine, Syngonium podophyllum Variegatum, Taccca chantrieri, Tradescantia albiflora, Tradescantia fluminensis, Xanthosoma lindenii, Zebrina pendula ‘Rubra’, etc.

3.8.2.2 Flower and Foliage Beauty

Aechmea spp., Aeschynanthus spp., Aphelandra squarrosa, Begonia spp., Bromelia balansae, Bromelia serra, Chrysothemis pulchella, Costus speciosus ‘variegata’, Episcia spp., Guzmania lingulata ‘Major’, Guzmania lingulata ‘Minor’, Heliconia spp., Hoffmannia refulgens, Hypocyrta glabra, Impatiens linearifolia, Kaempferia pulchra, Medinilla magnifica, Saintpaulia ionantha, Spathiphyllum clevelandii, Tillandsia spp., Vriesea spp., etc.

3.8.3 Classification Based on Gardening Importance

3.8.3.1 Growing in Hanging Baskets

Aeschynanthus spp., Asparagus densiflorus, Asparagus plumosus, Asparagus setaceus, Callisia repens, Chlorophytum bichetii, Begonia spp., Cryptanthus bivittatus, Cryptanthus bromelioides, Cryptanthus ‘Golden green’, Episcia spp., Hedera helix, Hemigraphis colorata, Hypocyrta glabra, Pelargonium spp., Pellionia daveauana, Peperomia spp., Pilea serpyllacea, Ruellia devosiana, Sansevieria trifasciata, Tradescantia albiflora, Tradescantia fluminensis, Zebrina pendula ‘Rubra’, etc.

3.8.3.2 Growing in Pots and in the Ground

Chrysothemis pulchella, Calathea spp., Cordyline terminalis, Costus speciosus ‘variegata’, Cryptanthus bivittatus, Cryptanthus bromelioides, Cryptanthus ‘Golden green’, Ctenanthe lubbersiana, Cyclanthus bipartitus, Dianella tasmanica, Dieffenbachia spp., Dracaena deremensis, Dracaena fragrans, Dracaena godseffiana, Heliconia spp., Impatiens linearifolia, Phalaris arundinaceae, Pleomele angustifolia, Pleomele reflexa, Sansevieria cylindrical, Sansevieria guineensis, Sansevieria trifasciata, Spathiphyllum clevelandii, Stanotaphrum secandatum variegatum, Taccca chantrieri, etc.

3.8.3.3 Growing of Plants in Pots

Ficus benjamina, Ficus cyathistipula, Ficus diversifolia, Ficus elastica, Ficus nitida, Ficus triangularis, Ficus triangularis ‘Variegata’, Fittonia verschaffeltii, Guzmania lingulata ‘Major’, Guzmania lingulata ‘Minor’, Hoffmannia refulgens, Homalomena spp., Leea rubra, Medinilla magnifica, Miconia hookeriana, Nidularium innocentii, Pandanus baptistii, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Pleomele reflexa, Tillandsia spp., Vriesea spp., etc.

3.8.3.4 Window Garden

Aechmea spp., Alocasia spp., Alpinia zerumbet, Aphelandra squarrosa, Cryptanthus bivittatus, Cryptanthus bromelioides, Cryptanthus ‘Golden green’, Dracaena godseffiana, Guzmania lingulata ‘Major’, Guzmania lingulata ‘Minor’, Impatiens linearifolia, Neoregelia carolinae, Neoregelia carolinae, Neoregelia carolinae, Nidularium innocentii, Oxalis hedysaroides rubra, Schefflera arboricola variegata, Stanotaphrum secandatum variegatum, Tillandsia spp., Xanthosoma lindenii, etc.

3.8.3.5 Corridor Placement

Aglaonema spp., Cordyline terminalis, Ctenanthe lubbersiana, Cyclanthus bipartitus, Dieffenbachia spp., Dracaena deremensis, Neoregelia carolinae, Neoregelia carolinae, Neoregelia carolinae, Nidularium innocentii, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Pleomele angustifolia, Pleomele reflexa, Sansevieria cylindrical, Sansevieria guineensis, Sansevieria trifasciata, Schefflera arboricola variegata, Stanotaphrum secandatum variegatum, etc.

3.8.3.6 Edging

Caladium spp., Calathea spp., Dianella tasmanica, Dracaena fragrans, Kaempferia pulchra, Maranta arundinacea, Saintpaulia ionantha, Sansevieria trifasciata, Scindapsus spp., etc.

3.8.3.7 Pillar Decoration

Monstera deliciosa, Monstera oblique, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Syngonium podophyllum variegatum, etc.

3.8.3.8 Drawing Room and Dining Room Placement

Aglaonema spp., Anthurium crystallinum, Anthurium forgetii, Anthurium magnificum, Anthurium pedato-radiatum, Anthurium scherzerianum, Begonia, Cordyline terminalis, Cryptanthus bivittatus, Cryptanthus bromelioides, Cryptanthus ‘Golden green’, Cyclanthus bipartitus, Dianella tasmanica, Dracaena deremensis, Dracaena fragrans, Dracaena godseffiana, Euonymous japonica, Fittonia verschaffeltii, Hoffmannia refulgens, Neoregelia carolinae, Nidularium innocentii, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Pleomele angustifolia, Pleomele reflexa, Sansevieria cylindrica, Sansevieria guineensis, Sansevieria trifasciata, Schefflera arboricola variegata, Schefflera venulosa, Stanotaphrum secandatum variegatum, Stromanthe sanguine, Taccca chantrieri, Xanthosoma lindenii, etc.

3.8.3.9 Living Room Placement

Aglaonema spp., Aspidistra elatior, Begonia spp., Calathea spp., Cyclanthus bipartitus, Dianella tasmanica, Dracaena godseffiana, Maranta arundinacea, Neoregelia carolinae, Nidularium innocentii, Philodendron ‘Black Cardinal’, Philodendron ‘Black Cardinal spot’, Philodendron ‘Blue mist’, Philodendron ‘Ceylon gold’, Philodendron ‘Charm’, Philodendron elegans, Philodendron erubescens ‘Gold’, Philodendron ‘Goldiana Spot’, Philodendron ‘Pink Princess’, Philodendron selloum, Philodendron ‘Serratum’, Pleomele angustifolia, Pleomele reflexa, Sansevieria trifasciata, Schefflera arboricola variegata, Schefflera venulosa, Stanotaphrum secandatum variegatum, Stromanthe sanguine, Tillandsia spp., Vriesea spp., Xanthosoma lindenii, etc.

3.9 Biodiversity of Bulbous Plants

Bulbous plants in horticulture include underground modified stems such as bulbs, tubers, corms and rhizomes having tuberous roots. There are many bulbous plants growing in the world, and the rich sources are in the plains of tropical and subtropical zones as well as in some hilly areas. The major bulbous plants are listed below (Table 8) based on those commercially exploited in the world for cut flower production and various garden beautifications.

Table 8 List of bulbous plant species biodiversity in the world

3.9.1 Cut Flower Production

Alpinia, Alstomeria, Dahlia, Gladiolus, Heliconia, Lilium, Narcissus, Nelumbo, Polianthes, Solidago, Strelitzia, Tulipa, etc.

3.9.2 Other Bulbous Plants for Garden Beautifications

Achimene, Acidenthera, Agapanthus, Allium, Alpinia, Amaryllis, Arisaema, Begonia, Caladium, Canna,, Cooperia, Costus, Crinum, Curcuma, Dahlia, Eucharis, Gloriosa, Heliconia, Haemanthus, Hedychium, Hemerocallis, Heppeastrum, Hymenocallis, Nymphaea, Strelitzia, Zantedeschia, Zephyranthus, ornamental ginger (Alpinia, Etingera, Tapeinochilos, Zingiber), etc.

3.10 Biodiversity of Roses

The rose is the queen of flowers, and it ranks first in the world flower market among ten important flowers growing commercially. Besides cut flower production, the rose is also used in garden decoration, potted plant production, loose flower production and the perfume industry. Dhua (1999) reported 120 species of roses having more than 30,000 cultivars differing in form, shape, size, colour, fragrance and flowering habit in cultivation and, recently reported by Banerji (2011), there are 316 species of roses with nine groups. Fifteen different classes of roses are found (Hybrid Teas, Floribundas, Hybrid Perpetuals, Teas, Grandifloras, Ramblers, Polyanthas, China Roses, Miniatures, Damask Roses, Bourbon Roses, Cabbage Roses, Moss Roses, French Roses, Albas, Musk Roses, Noisette Roses, Rugosas, Austrian Briars, Ramblers) all over the world, as described by Bose et al. (1989), but in India on the basis of availability and commercial exploitation of roses only seven groups are found, namely, Miniature, Polyantha, Miniflora, Talk Series, Floribunda, Hybrid Tea, and Climber. The prime producer of roses in the world now is Ecuador, supplying 70% of the total rose requirement.

3.11 Biodiversity of Chrysanthemum

The chrysanthemum is one of the most important commercial floricultural crops next to the rose, growing in open conditions as well as in polyhouses. Its origin is in China, but it grows all over the world in almost all zones based on the growing season. The flower is diversified because of the importance of loose flowers, in cut flower production, garden decoration and pot plant production. There are more than 200 species and 10 classes (single, incurved, intermediate, anemone, pompom, spoon, reflexed, fully reflexed, quill, and spider) of chrysanthemum plants based on inflorescence characteristics, as reported by Dhua (1999a, b).

3.12 Biodiversity of the Marigold

The marigold is a very common flower growing in a wide range of climates worldwide. About 4 species of Tagetes are commonly cultivated, although more than 50 species are known in this genus. Some important species are T. erecta, T. patula, T. tenuifolia, T. minuta, T. lucida, T. lacera, and T. lemmonii. Among all of these, Tagetes minuta gives the highest oil yield, 0.8% and 1.0% from leaves and flowers, respectively, whereas other species give a lesser oil yield. Many varieties have been developed throughout the world through hybridization for loose flower production, potted plant production, garden beautification, dry flower production, dyeing, etc.

3.13 Biodiversity of Jasmine

Jasmine is one of the most important fragrance flowers, originating in the tropical and subtropical Asiatic region, with 90 species; some improved varieties are grown for loose flower production and the perfume industry. The most important species under cultivation are Jasminum sambac, J. auriculatum, J. pubescens, J. grandiflorum, and J. humile. It is distributed in such Asiatic countries as India, Pakistan, Sri Lanka, Malaysia, Singapore, and other Gulf countries.

3.14 Biodiversity of Orchids

The orchids are handsome flowering plants, and this is the largest group of the plant families grown as a flowering crop all over the world. It is a perennial plant that grows on trees (as epiphytes) or on the ground in forested areas (terrestrial); some are also grown as semi-aquatics. According to Mukherjee (2002), there are two genera of Australian origin which are subterranean. The Asian continent is the prime source of orchids such as Dendrobium spp., found in various countries such as Korea, Japan, Indonesia, Thailand, and Malaysia (Mukherjee 2002). Regarding its biodiversity, India is one of the treasure houses of the orchid, mainly in northeastern hilly regions, the Himalayan region of North India and the Western Ghats of South India. Genera of orchids such as Aerides are found mainly in Southern India, Northern India, Burma, Malaysia and Indonesia; other orchid genera, namely, Vanda, with many species, are found in India, Ceylon, Indonesia, Thailand and some parts of Southeast Asia, whereas Calanthe spp. are found in China, Japan, Vietnam and Australia. The most important orchid genus, Cattleya, is found in South America. The genus Coelogyne with various species is centred in India (Sikkim), Nepal, Bhutan, Burma, China, Philippines, Indonesia, Thiland and Fiji. The Masdevallia species of orchids belong to hill regions of Brazil, Guiana, the Peruvian Andes, Colombia and Mexico. The most important genus of orchid, Dendrobium, is found in Korea, Japan, Indonesia, Thailand, Malaysia, Australia, Polynesia and New Zealand. Cypripedium spp. is located in the north tropical zone and tropical Himalayas of Malaysia, Indonesia, Philippines and New Guinea. Another most important genus of orchid, Cymbidium, is found in a wide range of climate in Korea, Japan, China, New Guinea, Australia and Himalayan regions as well as in Southeast Asia. The Oncidiun orchid species are commonly found in Southern Mexico to Columbia, Equador and Peru. At present, 1,300 species of orchid and 150,000 varieties are found in the world, where of total orchid production, 85% is Dendrobium spp. More than 40 countries are producing orchids; major exporting countries are the Netherlands (39.67%), Thailand (28.4%), Taiwan (10%), Singapore (10%), New Zealand (6%), and others (5.93%). Similarly, in reference to consumption, more than 60 countries are importing orchids, the prime importing countries being Japan (30%), UK (12%), Italy (10%), France (7%), USA (6%), and others (35%).

3.15 Biodiversity of Gerbera

The genus Gerbera is an important commercial flower, originated in South Africa and Asiatic regions but growing all over the world in a wide range of climate as cut flowers, potted plants and garden decoration. Of the 40 species of Gerbera available in the world, only the species Gerbera jamesonii is important for cultivation. It is now grown in hi-tech polyhouses for cut flower production in the subtropical zones of India, with 25 commercial varieties reported by Chowdhuri (2014). The Gerbera species G. jamesonii and G. viridifolia are used for hybridization, and at present thousands of commercial varieties are released for cut flower production by the various institutes and the private sector.

3.16 Biodiversity of Carnations

The carnation flower is indigenous in the Mediterranean regions and Muslim Africa, but it is successfully grown in countries such as Italy, Spain, Colombia, Kenya, Ceylon, Canary Islands, France, Holland, Germany and the USA. Of the 250 species of carnation available in the world, 3 important species are common (Dianthus caryophyllus, D. barbatus, D. chinensis), and more than 100 hybrids and varieties are cultivated in open fields as well as under a polyhouse for cut flower production.

3.17 Biodiversity of Anthurium

This plant, native to South America, grows well in tropical and subtropical regions. From 500 to 600 species are found in the world, and Anthurium andreanum is grown for cut flower production with different varieties. Three species (A. scherzerianum, A. veitchii, A. warocqueanum) are used for potted plant production and garden beautification.

3.18 Biodiversity of Annuals

Almost all the winter annuals originated in temperate regions such as North America and Europe, but these plants grow very successfully in tropical and subtropical regions during winter. Some annuals originated in tropical and subtropical regions and also grow in temperate regions during summers and the rainy season. People now are taking interest in gardening with annual flowers throughout the year for decoration in flower beds or growing in pots. During the past decade, many annuals have been brought by the different seed companies for marketing in terms of seed as well as seedlings for gardening. According to Vishnu Swarup (1995), many herbaceous annuals can grow in India throughout the year for gardening. Some important annuals listed below (Table 9) grow all over the world in different seasons.

Table 9 List of herbaceous plant species biodiversity in the world

3.18.1 Classification Based on Season of Growing

3.18.1.1 Winter Annuals

Acroclinium, Ageratum, Alyssum, Amaranthus, Antirrhinum, Arctotis, Aster, Begonia, Brachycome, Bromuslagus, Browallia, Calceolaria, Calendula, Candytuft, Capsicum, Carnation, Celosia, Chrysanthemum, Cineraria, Clarkia, Cleome, Clianthus, Cock’s Comb, Coleus, Convolvulus, Cornflower, Cosmea, Cosmos, Dahlia, Daisy, Delphinium, Dianthus, Digitalis, Dimorphotheca, Eschscholzia, Gazania, Geranium, Gerbera, Godetia, Gypsophylla, Helichrysum, Heliotrope, Hollyhock, Impatiens, Ipomoea, Lady’s Lace, Larkspur, Lavatera, Lineria, Lobelia, Lupin, Marigold (A), Marigold (C), Marigold (T), Mesembryanthemum, Mimulus, Molucella, Nasturtium, Nemesia, Nicotiana, Pansy, Pelargonium, Petunia (S), Petunia (D), Phlox, Portulaca, Poppy, Rudbeckia, Renunculus, Salvia, Statice, Stock, Sunflower, Sweet Pea, Sweet Sultan, Sweet William, Verbena, Viola, Zinnia.

3.18.1.2 Summer and Rainy Season Annuals

Amaranthus, Balsam, Gompherena, Coreopsis, Cosmos, Gaillardia, Gomphrena, Impatiens, Kochia, Petunia, Portulaca, Sunflower, Tithonia, Zinnia, etc.

3.18.2 Classification Based on Colour of Flower

3.18.2.1 White Colour Flower

Acroclinium, Ageratum, Alyssum, Antirrhinum, Arctotis, Aster, Balsam, Begonia, Brachycome, Bromuslagus, Candytuft, Carnation, Chrysanthemum, Cineraria, Clarkia, Cornflower, Cosmos, Daisy, Delphinium, Dianthus, Digitalis, Dimorphotheca, Eschoscholzia, Gazania, Geranium, Godetia, Helichrysum, Hollyhock, Impatiens, Lady’s lace, Larkspur, Lineria, Lobelia, Lupin, Marigold, Pelargonium, Petunia, Phlox, Portulaca, Poppy, Renunculus, Salvia, Statice, Stock, Sweet Pea, Verbena, etc.

3.18.2.2 Yellow Colour Flower

Antirrhinum, Arctotis, Calceolaria, Calendula, Carnation, Chrysanthemum, Cock’s Comb, Coreopsis, Eschoscholzia, Gaillardia, Gazania, Marigold, Mimulus, Nasturtium, Nemesia, Portulaca, Rudbeckia, Renunculus, Sunflower, Zinnia, etc.

3.18.2.3 Pink Colour Flower

Acroclinium, Alyssum, Antirrhinum, Arctotis, Aster, Balsam, Begonia, Carnation, Cineraria, Clarkia, Cleome, Cock’s Comb, Cornflower, Cosmos, Daisy, Dianthus, Digitalis, Eschscholzia, Gaillardia, Gazania, Geranium, Godetia, Helichrysum, Hollyhock, Impatiens, Larkspur, Lineria, Mesembryanthemum, Mimulus, Pelargonium, Petunia, Phlox, Portulaca, Poppy, Salvia, Stock, Sweet pea, Sweet William, Verbena, Zinnia, etc.

3.18.2.4 Blue Colour Flower

Ageratum, Brachycome, Browallia, Cineraria, Cornflower, Delphinium, Digitalis, Dimorphotheca, Heliotrope, Impatiens, Larkspur, Lobelia, Lobelia, Lupin, Nicotiana, Petunia Stock, Verbena, etc.

3.18.2.5 Violet Colour Flower

Aster, Balsam, Gomphrena, Hollyhock, Lavatera, Lineria, Nicotiana, Petunia, Phlox, Salvia, Statice, Stock, Sweet Sultan, Verbena.

3.18.2.6 Red Colour Flower

Amaranthus, Antirrhinum, Carnation, Clianthus, Cock’s Comb, Dianthus, Hollyhock, Lineria, Marigold, Nasturtium, Portulaca, poppy, Salvia, Sweet William, etc.

3.18.2.7 Orange Colour Flower

Antirrhinum, Calceolaria, Cosmos, Dimorphotheca, Helichrysum, marigold, Nasturtium, Nemesia, Rudbeckia, Tithonia, etc.

3.18.2.8 Multicoloured

Antirrhinum, Dianthus, pansy, Petunia, Phlox, Sweet William, etc.

4 Conservation of Ornamental Crops

Conservation means protecting existing plants in a particular area from any natural calamities and providing scientific management for betterment of the plants for growth and development as well as improvement. In other words, conservation involves collection, domestication and protection, when crops are introduced from other sources. It is realized by the higher authority of the nations, planners, researchers, and users at various levels all over the world that ornamental plant conservation for future consumption is important. The market for ornamental plants is constantly increasing with each passing day but at the same time is subjected to periodic trend-driven changes. Indeed, every year, hundreds of new cultivars, replacing the current assortment, are produced. However, changes in consumer preferences mean that cultivars unfashionable today may in the future once again be attractive for potential buyers. Furthermore, very often these constitute a great breeding material source. For this reason, the protection and storage of those valuable genetic resources is of great importance to be always able to meet market demands. Nevertheless, it is difficult for breeders and horticulturalists to provide enough space and funds for traditional cultivation of such numerous cultivars, which is laborious and threatened with biotic and abiotic stresses (Sekizawa et al. 2011). Traditional genetic conservation in the field or greenhouse requires intensive care of pot cultures or carefully separated field plots (Reed 2006). Haploids (important in breeding) and transgenic cultivars, which are gaining popularity among ornamental plants (Rosa L., Dianthus L., Gladiolus L.), require isolation to protect them from cross-breeding (Joung et al. 2006; Rajasekharan et al. 1994). Additionally, many ornamental species (of Orchidaceae, Cactaceae, Gentianaceae) are on the brink of extinction. Fast and easy access to high-quality gene banks of large material variety is the key for ornamental plant producers, and thus an efficient method for long-time conservation of the plant material may be extremely valuable for breeding and horticultural production (Halmagyi et al. 2004). Today, cryo-preservation is believed to be the most promising and valuable long-term storage method. During the past decade, conservation of plants at international and national levels received excellent momentum, which is reflected in the establishment of different plant genetic resource centers; for example, in India NBPGR established its 10 Regional Stations and 59 National Active Germplasm Sites (NAGS), comprising ICAR Institutes, Project Directorates, NRCs, AICRPs, SAUs, KVKs, etc. Gene banks/germplasm banks refer to a place or organization where germplasm is conserved in the living state, and the germplasm can be stored in the form of seeds, pollens, in vitro cultures or as plants growing in the field.

4.1 Methods of Conservation of Ornamental Crops

There are two important methods of genetic resources conservation- in situ and ex situ. In ex situ conservation, the conventional methods are orthodox seeds or seed gene banks are the conventional methods (orthodox seeds or seed gene banks), in vitro culture (tissue culture/cryo-preservation/DNA libraries), and field gene banks (plant conservation in a botanical garden/arboretum/greenhouse). For in situ conservation, the two important systems are natural habitats (an ecosystem with bioreserves/heritage sites/wildlife sanctuaries) and on-farm collections (farmers’ fields/tribal areas).

Thus, there are many methods of ornamental plants conservation, but in this chapter, ex situ conservation methods like field gene banks, the cryo-preservation method of conservation, and seed gene banks are discussed.

4.1.1 Field Gene Banks

Field gene banks, also called plant gene banks, are areas of land in which germplasm collections of growing plants are assembled. This approach is also ex situ conservation of germplasm. Those plant species that have recalcitrant seeds or do not produce seeds readily are conserved in a field gene bank. In field gene banks, germplasm is maintained in the form of plants as a permanent living collection. Most of the trees, shrubs, climbers, palms, cycades, bamboos, reeds, and grasses are conserved in open field conditions, whereas house plants, ferns, and orchids are conserved in a shaded structure, but commercial crops such as roses, chrysanthemums, anthurium, carnations, and gerbera plants are maintained properly in a polyhouse. Bulbs are stored in cool, dry and airy places.

4.1.2 Standards for Field Gene Banks

As per recommendations for gene bank standards for plant genetic resources for food and agriculture, ten levels of standards are given next.

4.1.2.1 Standards for Choice of Location of the Field Gene Bank

The agro-ecological conditions of the field gene bank should be as similar as possible to the environment where the collected plant materials were normally grown or collected, as the requirements of climate and soil of the different ornamental plants are varied. The field gene bank should be sited so as to minimize risks from natural and man-made disasters and hazards such as pests, diseases, animal damage, floods, droughts, fires, snow and freezing damage, volcanoes, hail, thefts or vandals. Isolation distance should be adequate for the production of seeds for distribution (to minimize risks of gene flow from crops or wild populations) to maintain genetic integrity. A secured land tenure is essential, with scope for future expansion of the collection of plants and easy accessibility.

4.1.2.2 Standards for Acquisition of Germplasm

All germplasm accessions added to the gene bank should be legally acquired, with relevant technical documentation. All material should be accompanied by at least a minimum of associated data as detailed in the FAO/Bioversity multi-crop passport descriptors. Propagating material should be collected from healthy growing plants whenever possible, and at an adequate maturity stage to be suitable for propagation. The period between collecting, shipping and processing and then transferring to the field gene bank should be as short as possible to prevent loss and deterioration of the material. Samples acquired from other countries or regions within the country should pass through the relevant quarantine process and meet the associated requirements before being incorporated into the field collection.

4.1.2.3 Standards for Establishment of Field Collections

All material should be accompanied by at least a minimum of associated data as detailed in the FAO/Bioversity multi-crop passport descriptors. Propagating material should be collected from healthy growing plants whenever possible, and at an adequate maturity stage to be suitable for propagation. The period between collecting, shipping and processing and then transferring to the field gene bank should be as short as possible to prevent loss and deterioration of the material. Samples acquired from other countries or regions within the country should pass through the relevant quarantine process and meet the associated requirements before being incorporated into the field collection. A sufficient number of plants should be maintained to capture the genetic diversity within the accession and to ensure the safety of the accession. It should have a clear map showing exact location of each accession in the plot. The appropriate cultivation practices should be followed taking into account micro-environment, planting time, root stock, watering regime, pest, disease and weed control.

4.1.2.4 Standards for Field Management Standards

Plants and soil should be regularly monitored for pests and diseases. Appropriate cultivation practices such as fertilization, irrigation, pruning, trellising, rootstock and weeding should be performed to ensure satisfactory plant growth. The genetic identity of each accession should be monitored by ensuring proper isolation of accessions wherever appropriate, avoiding intergrowth of accessions, with proper labelling and field maps and periodic assessment of identity using morphological or molecular techniques.

4.1.2.5 Standards for Regeneration and Propagation

Each accession in the field collection should be regenerated, when the vigour or plant numbers have declined to critical levels, to bring them to original levels and ensure that diversity and genetic integrity are maintained. True-to-type healthy plant material should be used for propagation. Information regarding plant regeneration cycles and procedures, including the date, authenticity of accessions, labels and location maps, should be properly documented and included in the gene bank information system.

4.1.2.6 Standards for Characterization Standards

All accessions should be characterized. For each accession, a representative number of plants should be used for characterization. Accessions should be characterized morphologically using internationally used descriptor lists where available. Molecular tools are also important to confirm accession identity and trueness to type. Characterization is based on recording formats as provided in internationally used descriptors.

4.1.2.7 Standards for Evaluation Standards

Evaluation data on field gene bank accessions should be obtained for traits of interest and in accordance with internationally used descriptor lists where available. The methods/protocols, formats and measurements for evaluation should be properly documented with citations. Data storage standards should be used to guide data collection. Evaluation trials should be replicated (in time and location) as appropriate and based on a sound statistical design.

4.1.2.8 Standards for Documentation Standards

Passport data for all accessions should be documented using the FAO/Bioversity multi-crop passport descriptors. In addition, accession information should include inventory, map and plot location, regeneration, characterization, evaluation, orders, distribution data and user feedback. Field management processes and cultural practices should be recorded and documented. Data should be stored and changes updated in an appropriate database system, adopting international data standards.

4.1.2.9 Standards for Distribution Standards

All germplasm should be distributed in compliance with national laws and relevant international treaties and conventions. All samples should be accompanied by all relevant documents required by the donor and the recipient country. Associated information should accompany any germplasm being distributed. The minimum information should include an itemized list, with accession identification, number and/or weights of samples, and key passport data.

4.1.2.10 Standards for Security and Safety Duplication Standards

A risk management strategy should be implemented and updated as required that addresses physical and biological risks identified in standards. A gene bank should follow the local Occupational Safety and Health (OSH) requirements and protocols. A gene bank should employ the requisite standards to fulfill all routine responsibilities to ensure that the gene bank can acquire, conserve and distribute germplasm according to the standards. Every field gene bank accession should be safety duplicated at least in one additional site or backed up by an alternative conservation method or strategy such as in vitro preservation or cryo-preservation, wherever possible.

4.1.2.11 Advantages of a Field Gene Bank

These gene banks provide opportunities for continuous evaluation of various economic characteristics. The banks can be utilized directly in breeding programmes and for the educational purpose of various students. The infrastructure may be used in recreation and extension education. Exposure visits of trainees such as farmers, students, Self Help Groups (SHG), and rural youth will inculcate them with the importance of PGRs and thereby the conservation, popularization and promotion of minor horticultural crops in particular areas. Production from field gene banks in the form of flowers and planting material may help in revenue generation for concerned organizations. The field gene bank ameliorates the microclimate of the site and helps conserve soil and water as well as wildlife, especially birds and apiculture.

4.1.2.12 Disadvantages of Field Gene Banks

Field gene banks cannot cover the entire genetic diversity of a species, but rather only a fraction of the full range of the diversity of a species. The germplasm in field gene banks is exposed to pathogens and insects, and sometimes is damaged by natural disasters such as bushfires, cyclones, or floods. Also, maintenance of germplasm in field gene banks is a costly affair.

4.1.2.13 Conservations in Field Gene Banks: A Review

There are many national and international institutes, in either the public or private sector, with a vital role in conserving ornamental plants, in addition to natural resources. Some institutes working under the government and private sectors are listed below in Table 10, those that are really remarkable in this line of work.

Table 10 Field gene bank conservation of different species or varieties of ornamental plants at different institutes in the world

4.1.3 Cryopreservation

Cryopreservation refers to the storage of explants from tissue culture at the ultra-low temperature of liquid nitrogen (−196 ^o C). At such temperature, all the biological reactions within the cells are hampered, hence the technique makes available the storage of plant material for theoretically unlimited periods of time at ultra-low temperature of liquid nitrogen (LN, −196 °C/−321 °F) or, seldom, its vapor phase (−150 °C/−238 °F). At this temperature, biochemical, metabolic, and cell division activities are arrested, allowing for long-term storage.

Advantages

The main advantage of this method is the reduction of in vitro culture costs, required space, contamination and somaclonal variation risk. The long-term cryoconservation of embryogenic cell lines could be a valuable tool for genetic transformation. Storage in liquid nitrogen would also help in preserving genetic diversity by storing wild species (e.g., for the purpose of breeding), some of which are already endangered. Moreover, cryotherapy may be used to reduce the number of pathogens, as proven with Pelargonium L’Hér (Gallard et al. 2011; Grapin et al. 2011).

Cryopreservation has been successfully used for many agricultural species. The first information on cryopreservation of ornamental species was reported by Fukai (1989) in a crop of Dianthus hybrida.

4.1.3.1 Material Selection for Cryopreservation

The selected material should be young, demonstrating meristematic potential (or regeneration potential, in the case of non-meristematic explants, such as callus cultures and cell suspensions, which should be in the linear growth phase 7–10 days after subculture), because only cells with dense cytoplasm and small vacuoles can survive freezing. Moreover, the use of a meristematic explant provides a greater chance of avoiding any variation.

4.1.3.2 Cryopreservation of Shoot and Root Tips

Different explants are used for cryostorage, such as apical or axillary shoot tips, seeds, spores, gametophytes, rhizomes or even protoplasts. Among these, shoot tips are used most often. As for vegetatively propagated, sterile plants such as Crocus and Chrysanthemum, crops with a high economic value, shoot tips constitute the best initial material. Plants of elongated growth such as Dianthus and Chrysanthemum are very easy to obtain by inoculating single-node explants on the Murashige and Skoog (MS) (1962) medium for 14 days. The optimal age of the cryopreserved buds should be between 2 weeks (for shoot apices) and 7 weeks (for axillary buds). Shoot tips of older plants are more difficult to isolate because of the development of covering leaves, although Takagi et al. (1997) reported better results when using 2- to 3-month-old mother plants of Colocasia esculenta L. Schott.

4.1.3.3 Cryopreservation of Germplasm

With endangered species (e.g., Lilium ledebourii and members of the Orchidaceae or Cactaceae families), it is important to derive explants without destroying the mother plant. Seeds seem to be a well-founded choice. The seeds are very often stored at subzero temperatures. The plants of the Orchidacae, Bromeliaceae and Cactaceae families have a high tolerance towards drying and freezing (germination higher than or similar to control). Application of cryopreservation in germplasm was found to be successful in many species of Dendrobium with different levels of vitrification as the survival percentage was above 65% (Thammasiri 2008). It is found that, unlike shoot tips, more developed mature seeds (3–4 months after pollination) are preferable, because they show a decrease in water content with increasing time after pollination (Hirano et al. 2005). In orchids such as Vanda tricolor, seed age should not exceed 6 months, as older seeds show lower germination capacity. Similarly, somatic embryos in the cotyledonary stage can be used for cryoconservation provided that efficient embryogenesis induction and embryo synchronization systems are developed, and that the embryos are converted into plants. As for species with recalcitrant seeds, for which their tissue culture and micropropagation systems are not yet established, the pollen cryopreservation of just-opening flowers, after enclosing approximately 0.5 g of sample in gelatin capsules, is a feasible alternative. Long-term pollen storage is important for germplasm preservation, pollen research, germplasm exchange, and improved efficiency in plant breeding, by helping to overcome the problems of geographic isolation and flowering asynchronism (Geng et al. 2011).

4.1.3.4 Cryopreservation of Pollen

Cryopreservation of pollen offers a simple and effective method of long-term pollen storage. Pollen may be stored in liquid nitrogen for many years without loss of its essential capabilities to pollinate, fertilize, and set normal fruit and seed when used in plant breeding, for controlled pollinations, or for the conservation of plant genetic resources. Pollen of Corylus, Fragaria, Pyrus, Rubus, and Vaccinium was frozen in liquid nitrogen either freshly collected and air dried, or after equilibration with atmospheres of 0%, 20%, 40%, 60%, 80%, 90%, or 100% relative humidity. Pollens have a high survival freezing percentage in LN provided the pollen moisture content is adjusted properly. Pollen of the wind-pollinated genus Corylus is intolerant of desiccation and survives freezing at very high moisture content levels relative to insect-pollinated Rosaceae pollens, which survive freezing only when dried before their immersion in liquid nitrogen.

Pollen cryopreservation helps in conserving the desired germplasm at the haploid stage. Because of its minute size, germplasm is highly compact and occupies less storage space in cryobiological containers. Cryopreservation experiences the fewest quarantine problems and facilitates global exchange of any germplasm in pollen.

4.1.3.5 Positive Aspects of Pollen Cryopreservation

• (a) Effective and efficient

• (b) Economically feasible

• (c) Tested and proven

4.1.3.6 Advantages of Pollen Cryopreservation

• 1. Simple protocols: Collection of pollen, and absence of complicated pretreatments makes this method easy to follow by trained personnel.

• 2. Repeatability: The procedures developed provide results with a high degree of repeatability.

• 3. Effective in retaining the genes: The genetic constitution of pollen cryopreservation remains unaltered.

• 4. Safe custody: Pollen remains safe and ready to use at short notice. Loss of genetic material from production plots can be avoided.

• 5. Eco-friendly: Refrigeration is avoided and hence there is no emission of CFC.

• 6. Low manpower unit.

4.1.3.7 Uses of Cryopreserved Pollen in Production Fields

• (i) Poor pollen producers: When the male parent is difficult to grow or is susceptible to some disease or is poor in vigor, this technology can be used.

• (ii) Genetic security for the male parent is ensured.

• (iii) There can be more female plants (double) in a production plot. When lines are used, parental increase of A line can be made easier by storing the pollen of B line.

4.1.3.8 Nuclear Genetic Diversity Located at IIHR, as of 2012, Has Cryopreserved About 60 Collections of Ornamentals

Synthetic Seeds:

Synthetic seed technology is one of the most important applications of plant tissue culture, as it combines the advantages of clonal propagation with those of seed propagation (i.e., storability, easy handling and transport, use of sowing equipment, protection against diseases and pests). In addition, synthetic seeds are used today in advanced procedures of cryopreservation (such as the “encapsulation-dehydration” method) with very promising results for the long-term preservation of plant germplasm. The first appearance of synthetic seeds (also called “artificial seeds” or “synseed”) dates back to more than 30 years ago and emerged from the idea of encapsulating a single somatic embryo inside an artificial seed coat, thus mimicking the natural seeds. Murashige (1977) was the first to produce an official definition of “synthetic seed:” “an encapsulated single somatic embryo, i.e., a clonal product that could be handled and used as a real seed for transport, storage and sowing, and that, therefore, would eventually grow, either in vivo or ex vitro, into a plantlet.”

Zygotic embryos, which are protected by a seed coat, have access to the nutrients that are accumulated in the cotyledons or in the endosperm, but somatic embryos are naked and dependent on the culture medium. Hence, it was soon evident that the synseed had to be as similar to the natural seed as possible, that is, it required the development of appropriate procedures for the encapsulation and the accumulation of storage compounds, creating an “artificial endosperm.”

As stated by Murashige’s definition, synthetic seed technology was initially restricted to species in which somatic embryogenesis was possible. Later, Bapat et al. (1987) proposed broadening the technology to the encapsulation of various in vitro-derived propagules, and they used axillary buds of Morus indica as a first example of this new application. The new concept paved the way for the encapsulation of explants other than somatic embryos, and to the formulation of a new definition of synseed (Aitken-Christie et al. 1995) as “artificially encapsulated somatic embryos, shoots, or other tissues which can be used for sowing under in vitro or ex vitro conditions.”

4.1.3.9 Application of Synthetic Seeds in Ornamentals

• 1. Propagation

Many important ornamental plants do not produce viable seeds (thus being propagated only by cutting or grafting), or, even if they can be propagated by seeds, several problems arise, including inbreeding depression and nonhomogeneity of cultivars. To avoid that, controlled breedings are often necessary. Moreover, in orchids, the very small seed size and the requirement of an association with mycorrhizal fungi are great limitations to seed propagation. In addition, traditional in vivo propagation methods are time consuming and very costly (Saiprasad and Polisetty 2003).

For all these reasons, micropropagation and somatic embryogenesis have represented a milestone for the reproduction of ornamental plants, providing a powerful tool for mass propagation, as well as for the production of transgenic plants with altered colour or scent or both. In spite of that, in Europe, only a small proportion of the annual production of some ornamental species (i.e., lilac) is currently propagated in vitro, mainly because low proliferation rates affect several species or varieties, as well as the problems faced with the acclimation of plants (Refouvelet et al. 1998). However, in the near future, synthetic seed technology could be the key to overcoming these problems, for example, through automated procedures of synseed production (Aitken-Christie et al. 1995) followed by autotrophic micropropagation (Jeong et al. 1995). Also, the concept of synthetic seed involves the use of small propagules and enables the direct sowing of this material in vitro or in vivo, so this technology could provide great flexibility to the breeders, not only reducing the costs when large quantities of propagules are required for handling, shipping and planting, but also eliminating the acclimation step when direct sowing in vivo is applied (Onishi et al. 1994).

• 2. Transportation

Another potential application is the use of the synseeds as a carrier for microorganisms, plant growth regulators, pesticides, fungicides, nutrients and antibiotics (Saiprasad 2001). For instance, in the case of orchids, the seeds need to be infected by symbiotic mycorrhizal fungi to increase plant access to soil resources (Arditti et al. 1984). A method of encapsulation of orchid seeds in alginate-chitosan or alginate-gelatin beads, together with the mycorrhizal fungus Rhizoctonia, has already been proposed (Tan et al. 1998), achieving an infection rate greater than 80%. One important recent application of synthetic seed technology concerns the preservation of plant germplasm, including endangered species, wild forms, and ancient and obsolete varieties. The concept of germplasm conservation in vitro involves both the slow growth storage of shoot cultures (mainly at a few degrees above 0 °C), and the long-term preservation of explants (shoot tips, nodal segments, zygotic and somatic embryos, cells and callus samples) in liquid nitrogen, at −196 °C (Lambardi and De Carlo 2003). The cryogenic technology, in particular, recently received great improvement by the use of synthetic seeds with the development of procedures named “encapsulation-dehydration” and “encapsulation-vitrification” (Panis and Lambardi 2005).

• 3. Conservation

Slow growth storage provides a useful alternative for the medium-term preservation of ornamental species, that is, with conservation times up to 10 months for somatic embryo synseeds of Cyclamen persicum (Ruffoni et al. 2002). In orchids, encapsulated Protocorm-like bodies (PLBs) of Oncidium and Dendrobium species could be preserved at 4 °C for 45 and 60 days, respectively, maintaining maximum germination rates (100%) (Saiprasad and Polisetty 2003). However, in both species, a decrease in synseed conversion to plantlets was observed when storage at low temperature was prolonged (not shown). A beneficial effect from slow growth storage (from 3 to 9 months) of synthetic seeds is also reported for somatic embryos of Camellia japonica (Janeiro et al. 1997), Citrus reticulata (Germanà et al. 1999) and Paulownia elongata (Ipeki and Gozukirmizi 2003), axillary buds of Morus spp. (Pattnaik and Chand 2000) and Syringa vulgaris (Refouvel et al. 1998), as well as for bulblets of Lilium longiflorum (Standardi et al. 1995).

Although the slow growth storage technique is widely used by micropropagation laboratories for the short- and medium-term conservation of stock cultures, germplasm stored this way is vulnerable to losses from equipment failure, microbial contamination at subculture time, and the effects of somaclonal variation. In contrast, cryopreservation provides a feasible option for the long-term preservation of explants, when effective procedures of ultra rapid freezing have been optimized and explant regrowth is ensured after thawing and plating. At a cryogenic temperature, the rate of chemical and biophysical reactions is practically zero. so that the growth of the frozen organ/tissue is hampered. Hence, in theory, germplasm cryopreservation could be considered unlimited in terms of time. The cryopreservation method based on alginate encapsulation of explants and bead dehydration (named “encapsulation-dehydration”) has been developed for a wide range of plant species (Panis and Lambardi 2005).

4.1.4 Seed Gene Bank

4.1.4.1 International Survey of the Seed Banks/Genebanks in Botanic Gardens

There are more than 1700 botanic gardens and institutions worldwide holding plant collections that serve both conservation and educational purposes. Many gardens have the mandate to preserve rare or threatened wild plants and make the plant material available for research. However, detailed information on their ex situ conservation methods such as seed banking was lacking. Therefore, a review of the available information on botanic garden gene/seed banks, their collections and facilities, was undertaken from data held in the Botanic Gardens Conservation International (BGCI) databases and by analysing the data from the responses to a questionnaire sent to about 1500 botanic gardens worldwide. Of these, 388 replies from gardens were received and analysed, of which 152 reported having a seed bank/gene bank. The questionnaire was divided into four main sections with enquiries about these points:

• Type and nature of accessions stored

• Seed storage facilities and conditions

• Data processing and capacity to hold a database

• Purpose of the collections

• Methods being used at that time by botanic gardens for the maintenance of germplasm collections, including seed banks, field gene banks and tissue culture collections, and to analyse the relative merits and limitations of each system

Results of the Survey, 1994

The main conclusions follow:

• Most of the seed banks surveyed are in warm temperate climates, which includes Europe.

• Distribution is currently one of the main objectives of seed storage in botanic gardens, with a strong emphasis on conservation in long-term seed banks.

• Of botanic gardens surveyed, 30.7% have some form of cool- to low-temperature seed storage.

• There is great variation in the number of accessions representing each species. Long-term storage seed banks collect twice as many sample populations per species than medium- and short-term seed banks (i.e., 36 species per 100 accessions in long-term seed banks as opposed to 75 species per 100 accessions in short-term seed banks).

• At least 255,832 accessions of germplasm are stored by the 152 seed banks/gene banks surveyed, and most of them hold species that are rare or endangered. There are 17,096 known accessions of germplasm held in field gene banks.

• In long-term seed banks maintained by botanic gardens, approximately 77% of their collections of germplasm were collected directly from the wild.

• Medium-term seed banks have a higher proportion of crop plant species than long-term or short-term seed banks.

• Most seed banks that have a collection from a specific geographic area concentrate on the conservation of their regional flora.

• Collections from a specific taxonomic group in long-term seed banks include families of major and minor crop plant species.

• Few seed banks mention having a drying room, and even fewer undertake moisture content tests.

• Paper envelopes are mainly used by medium- and short-term seed banks as packing material whereas laminated foil bags are mainly used by long-term seed banks.

• In seed banks, 65.5% have accessions intended to be stored for more than 15 years; only 27.5% of them store some of their accessions at temperatures below −15 °C.

• Of short-term seed banks, 28.8% have tissue culture facilities and 45.0% have an in situ reserve attached to their gardens.

• Of the seed banks/gene banks, 62.7% use a computer database system to store information generated from germplasm accessions.

• Among long-term seed banks, 82.6% have a distribution policy but only 34.5% of the short-term seed banks do so, even though distribution is their main purpose.

• Half of the seed banks/gene banks surveyed undertake seed germination testing.

• Most botanic garden seed banks/gene banks state that they would benefit from information exchange with other seedbanks or gene banks in botanic gardens.

Current Status of Ornamental Plant Genetic Conservation, OPGC (Ohio State University) and of Herbaceous Ornamental Germplasm Conservation Within the National Plant Genetic System, NPGS (USA)

Seed production, processing and testing techniques, and data entry and management protocols are being established and documented for the preparation of comprehensive Operations Manuals.

In the first seed regeneration cycle during 2002, about 40 accessions were successfully multiplied in greenhouse compartments and field pollination cages by using both honeybees and bumblebees as pollinators (Stieve and Tay 2003).

The OPGC is presently using the 2001 list (Table 11) of 30 genera in its work plan. These 30 genera encompass about 6700 distinct taxa, based on Hortus Third (Bailey and Bailey 1976), which exceeds current OPGC resources.

Table 11 NPGS collections of herbaceous ornamentals and their maintenance sites in the mid-1990s before the establishment of the OPGC

A survey was carried out among floricultural scientists in academia and industry. The top 15 genera in descending order were Begonia, Impatiens, Geranium (more probably referring to Pelargonium as it is known as geranium in the trade), Petunia, Salvia, Pelargonium, Viola, Dianthus, Campanula, Hierocallis, Alstroieria, Lilium, Verbena, Rudbeckia, and Phlox (Tay 2003). Germplasm acquisition is now focusing on four of the genera with the highest rankings: Begonia, Impatiens, Petunia and Pelargonium. In contrast, unique germplasm of the other priority genera, and threatened germplasm irrespective of genera, will also be added to the gene bank and put into long-term storage. Germplasm characterization and evaluation will concentrate on the high-ranking priority genera.

Most of the transferable herbaceous ornamental plant accessions at other NPGS repositories have been transferred to the OPGC, resulting in the acquisition of 966 accessions representing 62 genera (Table 12).

Table 12 Current (2003) OPGC herbaceous ornamental plant accessions in the GRIN database

Through strong working relationships with both public and private sector researchers and plant breeders, some 700 new accessions were acquired in 2003–2004 and given top priority by OPGC numbers: these include the 205 accessions of Pelargonium breeding materials from Pennsylvania State University, 121 accessions of Pelargonium species from Shady Hill Gardens, 26 accessions of Begonia species from the American Begonia Society, and 18 accessions of Impatiens species from the International Impatiens Society. Another 147 accessions of newly collected germplasm have come from Armenia, China, Russia and the Ukraine from recent USDA plant exploration missions, the North American China Plant Exploration Consortium (NACPEC), and the Midwest Plant Collecting Collaborative (MWPCC).

Photographs Show Different Ornamental Crop Field Gene Banks