Keywords

9.1 Introduction

Plant genetic resources—constituting genotypes or populations of cultivars (landraces, advance/improved cultivars), genetic stocks, wild and weedy species which are maintained in the form of plants, seeds, tissues, etc.—hold key to food security and sustainable agricultural development (Iwananga 1994). Genetic diversity is an essential resource for crop breeding and reservoirs of identified and unidentified genes are essential for the study of the breeders of all generations. The primary and secondary centers of origin are the source for germplasm due to the natural hybridization and flow of genes throughout their existence. Detailed study on germplasm gives us the source material for resistance to biotic and abiotic stresses which can be further used in the improvement aspect.

India is the land of spices and is the primary or secondary center of origin to major spices especially black pepper, cardamom, ginger, turmeric, cinnamon, tamarind, and garcinia, where genetic diversity is rich and their wild forms still exist. In others, the diversity is limited. The important spices relevant in Indian context are black pepper, cardamom, ginger, turmeric, coriander, cumin, fennel, fenugreek, cinnamon, turmeric, cloves, allspice, garcinia, vanilla, and a few herbal spices (Ravindran et al. 2005b; Peter and Nirmal Babu 2006; Ravindran et al. 2006).

9.2 Origin, Distribution, and Diversity

9.2.1 Black Pepper

Black pepper one of the oldest spices known to the world (Piper nigrum L.) is a native of the humid tropical forests of the Western Ghats, from where it has spread throughout the tropics. P. nigrum L. belongs to the pepper family Piperaceae of the series Microembryeae of Monochlamydeae. The genus Piper is generally distributed in the tropical and subtropical regions of the world. The main centers of distribution are Central and South America and South Asia (Trelease and Yuncker 1950). The main center of distribution for Neotropical species is Central America. In the Central American forests, the genera are distributed in four different habitats, viz. edge of the semi-deciduous forests, inside the semi-deciduous forest, edge of the swampy forest, and inside the swampy forests. The greatest diversity of Piper species occurs in Tropical America with over 700 species followed by southern Asia with over 400 species (Fig. 9.1). Diversity of Piper is also occurring in South Pacific (40 spp.) and in the African tropics (15 spp.) (Jaramillo and Manos 2001).

Fig. 9.1
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The global geographical distribution of Piper and probable centers of origin of genus Piper (Saji 2006)

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About 114 species are reported from the Indian subcontinent (Table 9.1), of which about 18 species are found in sub-mountainous tracts of Western Ghats and adjacent peninsular and coastal region (Ravindran and Nirmal Babu 1994; Ravindran 2000; Ravindran et al. 2000, 2005; Tyagi et al. 2004; Ravindran and Kallupurackal 2012). In India, the north-eastern region and the south-western (Western Ghats) region are recognized as two independent centers of diversity. Piper species occurring in India are unisexual, but the Central and South American species are generally bisexual types. However, the cultivated black pepper is bisexual. Probably, the bisexual types might have originated from the wild unisexual ones as a result of domestication and conscious and continuous selection for high-yielding types and their maintenance by vegetative propagation by people through the ages.

Table 9.1 Piper species reported from India
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Over 100 cultivars of black pepper are known to India. The Dutch in the seventeenth and eighteenth centuries brought pepper cultivation on to Java, Sumatra, Borneo, Sarawak, the Malay Peninsula, Siam, Philippines, and later into the West Indies on a plantation scale. Black pepper is believed to be introduced to America during the middle of eighteenth century (Gentry 1955).

In addition to black pepper, the other economically important species of Piper are Indian long pepper (P. longum L), betel vine (P. betle L.), Java long pepper (P. chaba Hunter), tailed pepper (P. cubeba L.), Kawa pepper (P. methysticum Forster), West African pepper (P. clusi C. DC.), Benin pepper (P. guineense Schum. & Thonn.) and Japanese pepper (P. kadzura (Choisy) Ohwi.).

The community composition, species richness, relative abundances of different species, and species diversity in a community were studied by Saji (2006) using Shannon diversity index (H) which indicated that the Western Ghats region of South India could be divided into seven, based on relative abundance of different species and species diversity in a community. Southern tip of India has highest diversity, while the coastal regions have low diversity. The hilly regions of Kerala and Tamil Nadu are the two regions with maximum diversity—especially the mountainous regions between the states (Fig. 9.2). The effort by the Government of India to protect these natural habitats as bio-parks is helping in conservation of biodiversity in these regions. This is helping many Piper species getting protected and they multiply into viable populations due to prevailing vegetative propagation. Because of these efforts, we find some endangered species like Piper wightii and P. schmidtii which are multiplying in Nilgiri reserves in Tamil Nadu and recently we discovered an ecological niche of Piper barberi a critically endangered species of Piper in the forest region of Idukki dist of Kerala, in India.

Fig. 9.2
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Diversity indices of distribution of Piper species in Western Ghats of India

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The cultivar diversity is very high in India where over 100 cultivars of pepper have been reported (Ravindran et al. 2000) from Western Ghats (Table 9.2). It is probable that the cultivated forms in different regions have originated from wild peppers of the same region.

Table 9.2 Important cultivars of black pepper in India and other countries
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India has assembled a world collection of black pepper germplasm with over 3500 accessions of cultivars, related species, land races, and maintains them in ex situ clonal field repositories. In addition, over 17 improved varieties are released for cultivation with good characters like high yield, bold berries, resistance to Phytophthora and nematodes, high dry recovery, high piperine, oleoresin and essential oil contents (Table 9.11). However, due to the preference of high-yielding varieties and debilitating diseases like Phytophthora foot rot, many of the old primitive cultivars are being replaced and are slowly disappearing from cultivation.

9.2.2 Small Cardamom

Small Cardamom is the dried fruit of Elettaria cardamomum Maton, belonging to Zingiberaceae. Cardamom occurs in its native state only in the tropical evergreen forests of the Western Ghats. The wild populations of cardamom gradually declined because of the large-scale destruction of forest habitats. E. cardamomum in India is monotypic genus with only one species. Its closest species is the Sri Lankan wild cardamom E. cardamomum namely, var. major. Seven other species of Elettaria were reported from southeast Asia.

The species E. cardamomum comprises a freely interbreeding population, and the genus Elettaria seems to be a “Cenospecies,” in India, with a single “ecospecies” corresponding to the taxonomic species, E. cardamomum Maton. The ecotype can be divided into three mini local populations as local types  they are ‘Travancoria,’ ‘Oblongata,’ and ‘Kanarensis.’ Cardamom consists of three morphologically distinct types, namely, Malabar, Mysore and Vazhukka. Cardamom being a cross-pollinated crop, a lot of phenotypic variants exists in nature. Some of exceptional variants in cardamom have panicles of various types, terminal panicle, branched raceme, female sterility and cleistogamy. Good variability exists in cardamom with regard to various morphological characters such as fruit (capsule) size, shape, leaf, and plant pubescence and quality characters, such as essential oil and its components, such as 1, 8-cineole and alpha-terperyl acetate. (Madhusoodanan et al. 1994, 2002) reported that a wide range of variation was observed between and within cultivars of small cardamom for economically important characters. In general, the ‘Vazhukka’ and ‘Mysore’ types are robust compared to Malabar types (Ravindran and Madhusoodanan 2002; Korikanthimath et al. 2006; Parthasarathy and Prasath 2012).

Over 900 accessions of cardamom germplasm are maintained as clonal repositories at various centers in India. The characters which are found to least occur are compound panicle, basal branching of panicles, and red pseudostem pigmentation. The diversity is very narrow with respect to biotic and abiotic stresses. In addition, over 10 improved varieties are released for cultivation with good characters like high yield, bold capsules, high-quality attributes, resistance to viruses, rhizome rot and drought (Table 9.11). However, due to the preference for newer high-yielding varieties and debilitating viral disease and fungal diseases like katte and rhizome rot, many of the low yielding cultivars are being replaced.

9.2.3 Ginger

Ginger (Zingiber officinale Roscoe) belongs to family Zingiberaceae. The north-eastern region is a major producer of ginger. Indo-Malayan region is the native home of this family. Ginger is not found in the truly wild state. It is believed to have originated in southeast Asia, but was under cultivation from ancient times in India (Purseglove et al. 1981; Mohanty and Panda 1994). There is no definite information on the primary center of origin or domestication. It was brought to the Mediterranean region from India by traders during the first century AD. During the thirteenth century AD, the Arabs took ginger to eastern Africa from India. Later, it was spread to West Africa by the Portuguese for commercial cultivation. Because of the ease with which ginger rhizomes can be transported long distances, it has spread throughout the tropical and subtropical regions in both hemispheres. The main areas of ginger cultivation are India, China, Nigeria, Indonesia, Jamaica, Taiwan, Sierra Leone, Fiji, Mauritius, Brazil, Costa Rica, Ghana, Japan, Malaysia, Bangladesh, Philippines, Sri Lanka, Solomon Islands, Thailand, Trinidad, Tobago, Uganda, Hawaii, Guatemala and many Pacific Ocean islands.

The genus Zingiber, consisting of about 150 species, is widely distributed in tropical and subtropical Asia. Some important species of Zingiber (Sabu and Skinner 2005, Ravindran and Nirmal Babu 2005a) are given in Table 9.3. In India, variability for cultivated ginger exists mainly in the north-eastern region and Kerala. A botanically distinct variety Z. officinale var. rubrum having pink outer skin of rhizome is under cultivation in Malaysia. The genus Zingiber includes many species grown as ornamentals, but some are cultivated for valuable medicines. They bear showy, long-lasting inflorescences and often brightly colored bracts and floral parts; they are widely used as cut flowers in floral arrangements. Some of them are good foliage plants due to their arching form and shining leaves.

Table 9.3 Species of Zingiber and their distribution
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Cultivated ginger Zingiber officinale does not occur in wild but maintained only under cultivation. Ginger has no seed set and is only propagated vegetatively. There is moderate varietal/cultivar diversity in India. In India, over 1200 accessions are maintained in clonal repositories. The cultivars are often named after the locality. Good variation with respect to plant height, days to maturity, dry recovery, rhizome shape, size, yield, fiber content, color and quality attributes was observed (Ravindran et al. 2005a; Nirmal Babu et al. 2011a; Valsala 2012). This is due to accumulated natural mutations maintained in the population efficient vegetative propagation. Chemical variations in essential oil, oleoresin and gingerol, shogaol contents, have been reported. However, genetic diversity for biotic and abiotic resistances is almost absent making this crop susceptible for diseases and pests. In addition, over 12 improved varieties are released for cultivation with good characters like high gingerol and shogaol content and dry recovery. High/low fiber, plumpy rhizomes, vegetable types, and high dry recovery (Table 9.11). Rhizome rot caused by Pythium spp. and bacterial wilt caused by Ralstonia spp. are the most destructive diseases affecting ginger plantations. As no resistance source is reported so far in ginger or related species, many of the local cultivars are facing threat of elimination.

9.2.4 Turmeric

Turmeric Curcuma longa (L.) belongs to Zingiberaceae, and is one of the most ancient spices used in India. India is the largest producer and exporter of turmeric. Turmeric is believed to have originated in the Indo-Malayan region.

The genus Curcuma consists of about 70–110 (true identity is unclear) species distributed chiefly in southeastern Asia (Skornickova et al. 2007). In addition to C. longa, the other economically important species of the genus are C. aromatica, which is used in medicine and in toiletry articles; C. kwangsiensis, C. ochrorhiza, C. pierreana, C. zedoaria and C. caesia, which are used in folk medicines of the southern and southeastern Asian nations; C. alismatifolia, C. elata and C. roscoeana, with floricultural importance; Curcuma amada, which is used as medicine and in a variety of culinary preparations, pickles, and salads; C. zedoaria, C. pseudomontana, C. montana, C. angustifolia, C. rubescens, C. haritha and C. caulina which are all used in manufacturing arrowroot powder. The other species of minor importance are C. purpurescens, C. mangga, C. heyneana, C. zanthorrhiza, C. phaeocaulis and C. petiolata (Nirmal Babu et al. 1993; Rama Rao and Rao 1994; Velayudhan et al. 1999; Ravindran et al. 2007a, b; Skornickova et al. 2007).

The greatest diversity of the genus occurs in India, Myanmar and Thailand and extends to Korea, China, Australia and the South Pacific. This genus is also distributed in Cambodia, Indonesia, Malaysia, Laos, Madagascar and the Philippines. Many species of Curcuma are economically valuable and different species are cultivated in China, India, Indonesia and Thailand and throughout the tropics, including tropical regions of Africa, America and Australia. Genus Curcuma has about 42 species distributed in India, out of which C. longa is cultivated for turmeric, C. aromatica is grown for use in toiletry articles, and C. amada (mango ginger) is cultivated in limited areas for use as a vegetable. The country of origin of cultivated turmeric (C. longa) is presumed to be the southeast Asia. India is the single largest producer and exporter of turmeric in the world (Manohar Rao et al. 2006; Nirmal Babu et al. 2011b).

Different species of turmeric are used in folk medicine, as a spice, as a vegetable in a variety of culinary preparations, pickles, and salads, in the production of arrowroot powder, and in toiletry articles. Many Curcuma species are highly valued as ornamentals. Turmeric oil is also now used in aromatherapy and the perfume industry. Many Curcuma species were recognized by local and tribal people all over Asia as valuable sources of medicine. Distributions of Curcuma species in southeast Asia and India are given in Tables 9.4 and 9.5.

Table 9.4 Distribution of Curcuma species in Indo—Malayan region
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Table 9.5 Distribution of Curcuma species in Indiaa
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Good cultivar diversity occurs in India, with over 1500 accessions are conserved in various centers. In India, turmeric set seeds and seedling populations of over 300 progenies supplement the existing germplasm. There is a high variation with regard to morphology, yield, quality attributes, and dry recovery. In addition, over 34 improved varieties are released for cultivation with good characters like short duration, resistance to rhizome rot, plant height, high curcumin, and oleoresin content and dry recovery (Table 9.11).

9.2.5 Vanilla

Vanilla planifolia [syn. Vanilla fragrans) is a member of Orchidaceae, the only commercially important spice in this family. Vanilla is a crop of great commercial importance as the source of natural vanillin; a major component of flavor industry. It originated in Mexico but is grown in many Pacific Ocean islands, Indonesia and many African countries. The genus Vanilla comprises about 110 species, distributed in tropical parts of the world (Purseglove et al. 1981; Cuvelier and Grisoni 2010; De Guzman and Zara 2012). Few important vanilla species are V. andamanica, V. aphylla syn. V. vatsalana, V. pilifera, V. tahitensis, V. pompon, V. wightiana, V. parishii, and V. walkeriae (Table 9.6).

Table 9.6 Some important species of Vanilla
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The germplasm available in vanilla in India is very narrow. The primary gene pool of V. planifolia is narrow and is evidently threatened due to destruction of its natural habitats making the secondary gene pool important as a source of desirable traits especially for resistance to diseases. The species diversity in the country is represented by five species, viz., V. aphylla, V. walkeriae, V. wightiana, V. pilifera, and V. andamanica and most of them are considered endangered. Intense works of selection, breeding, and conservation of genetic resources are required to overcome the narrow genetic base of this vegetatively propagated crop. Effective procedures for micropropagation and in vitro conservation by slow growth in selected species of vanilla are available.

Although vanilla is cultivated throughout the tropics, its natural populations in Southern Mexico—the most critical sources of novel genetic diversity—are on the verge of disappearing due to deforestation and over collection (Lubinsky 2003). Since the narrow primary gene pool is evidently threatened, the secondary gene pool comprising the close relatives of V. planifolia, which is also equally threatened, becomes important as a source of desirable traits—especially for self-pollination, higher fruit set, and disease resistance (Minoo 2002; Minoo et al. 2006; Bory et al. 2010). Many species of vanilla are considered endangered (Table 9.6) and there is urgent need to conserve them. The recent International Congress on vanilla emphasized the need to conserve these species before they go extinct (International Congress on Vanilla 2003). Thus a major challenge is to conserve the vanilla gene pool from the onslaught of habitat destruction, over collection, climate changes and destructive diseases in monocultures.

Recent advances in conservation have paved the way to safeguard plant biodiversity with a biotechnological approach, which can be regarded as complementary to the traditional clonal orchards and seed banks. Traditionally, Vanilla germplasm is conserved in clonal repositories belonging to botanical gardens and in scientific institutions. However, the high costs of this traditional conservation system limit the number of accessions that can be preserved. In order to stem the flow of loss of biodiversity, an attempt to conserve Vanilla species, in vitro has been made (Minoo et al. 2006).

9.2.6 Tree Spices

There are many tree spices which are important. The most important ones, in Indian context, are cinnamon (Cinnamomum verum syn: Cinnamomum zylanicyum), nutmeg (Myristica fragrans), clove (Syzygium aromaticum Syn: Eugenia Cariophyllus), and garcinia (Garcinia sp.) (Ravindran et al., 2004a, b, 2005a), some of which are native and others introduced (Krishnamoorthy and Rema 1994).

9.2.6.1 Nutmeg

Nutmeg tree is the only plant that produces two separate spices, namely nutmeg (kernel of the seed) and mace (aril covering the seed). Nutmeg belongs to Myristicaceae and the species is believed to have originated in the Moluccas Islands of Indonesia. The important species occurring in India are M. amygdalina, M. andamanica, M. attenuata, M. dactyloides, M. beddomeii, M. gibbosa, M. glabrae, M. glaucescensr., M. irya Gaertn., M. kingii., M. longifolia., and M. magnifica. Being a dioecious plant, good variability exists in nutmeg, especially for characters such as fruit size and shape, mace, and seed volume. (Krishnamoorthy et al. 1996). The chemical composition also shows quantitative variations for major quality components. Myristicin, elemicin, and 1,8-cineole are the important constituents in nutmeg. There is an increase in genetic diversity in cultivated nutmeg due to variation through segregating progenies. But the nutmeg population (nutmeg swamps) are slowly disappearing. Over 475 accessions are maintained at various centers in India. About six varieties of high-yielding, high-quality cultivars were recommended for release in India (Table 9.11).

9.2.6.2 Cinnamon

True cinnamon is obtained from C. verum belonging to Lauraceae; indigenous to Sri Lanka and Southern Western Ghats of India. Cassia cinnamon is obtained from various sources, the most important being C. cassia (Chinese cassia, Vietnam cassia or Saigon cassia). The other cassia cinnamons are Indonesian (Javan) cassia (C. burmanii), Saigon (Vietnam) cassia (C. loureirii), and Indian cassia (C. tamala). The genus is a native of south-western tropical India and SriLanka, consisting more than 250 species distributed in southeast Asia, China and Australia. Seychelles and Malagay Republic are the major cinnamon-producing countries besides Sri Lanka. Some important species of Cinnamomum are given in Table 9.7. Over 26 species occur in India. Endemic species are C. macrocarpum Hk. F., C. malabathrum Bl., C. nicolsonianum Manilal and Shylaja, C. riparium Gamble, C. keralaense Kosterm, C. travancoricum Gamble, C. wightii Meiss., C. heyneanum Nees, C. gracile (Miq.), and C. chemungianum Mohan and Henry. Non-endemic species are C. citriodorumThw., C. filipedicellatum Kosterm., C. goaense Kosterm, C. perottetii Meiss., C. sulphuratum Nees, and C. walaiwarense Kosterm (Haldankar et al. 1994; Krishnamoorthy et al. 1996; Tyagi et al. 2004; Ravindran et al. 2004a, b).

Table 9.7 Species diversity in tree spices
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Cinnamon trees are naturally cross-pollinated and as a result much variation exists in natural populations for morphological, chemical as well as bark characters. The quality of cinnamon depends on the essential oil content and composition of leaf and bark oil. The leaf oil contains eugenol as the chief component, while the bark oil has cinnamaldehyde. Over 430 accessions are maintained at various centers in India. About six varieties of high-yielding, high-quality cultivars were recommended for release in India (Table 9.11).

9.2.6.3 Clove

Clove, belonging to the family Myrtaceae, is a native of Moluccas Islands and was introduced to India. Because of the limited introductions that have taken place and due to self-pollinating nature of the species, the genetic base of germplasm available in India is very narrow for use in any meaningful crop improvement program. The spice is dried, mature, unopened flower buds (Nurdjannah and Bermawie 2012). The clove buds contain around 15–17 % volatile oil, the main component of which is eugenol (about 70–90 %). There are many species of Syzygium occurring in India. Over 250 accessions are maintained at various centers in India.

9.2.6.4 Garcinia

The genus Garcinia of the family Clusiaceae is a large genus of evergreen polygamous trees, shrubs, lianas, and herbs. It consists of over 200 species distributed in the tropics of the world chiefly in Asia, Africa, and Polynesia. Garcinia is native to old world tropics and maximum concentration of Garcinia species occurs in Asian countries. It is hypothesized that the genus Garcinia has originated before the continental drift followed by separate diversification in canters in the Afro-Madagascar and Indo-Malayan areas. About 35 species occur in India, many of which are endemic and economically important including G. mangostana, G. indica G. gummi-gutta, G. cowa, G. pedunculata, G. xanthochymus Hk.f, with immense medicinal properties. Garcinia is the source for a natural diet ingredient hydroxy citric acid (HCA) which is an anti-obesity compound. However, lack of awareness coupled with habitat destruction, is leading to genetic erosion of this forest resource and many species are threatened.

Parthasarathy et al. (2013) reported that using GIS technique mapping of potential distribution of wild species of Garcinia of Western Ghats with the help of GIS techniques was done. Collection sites were plotted on map with the help of ArcGIS software. Based on the GIS prediction surveys, the authors found that Garcinia cambogia is distributed throughout the Western Ghats, whereas G. indica is predominantly seen in the northern parts of Western Ghats. This indicated that their distribution and population size is reduced to dangerous levels. Unless located and preserved, these species may quickly become endangered. There is considerable variation in yield and other characters studied.

9.2.7 Seed Spices

The major seed spices grown in India are coriander, cumin, fennel and fenugreek which are grown on a commercial scale. Cultivation of the remaining seed spices is limited to certain areas only. Three of the major seed spices, coriander (Coriandrum sativum L.), cumin (Cuminum cyminum L.), and fennel (Foeniculum vulgare Mill), belong to family Apiaceae, whereas fenugreek (Trigonella foenum-graecum L.) belongs to Fabaceae. Most of the seed spices cultivated in India are Mediterranean in origin. In none of the seed spices, wiled relatives, which could contribute by way of hybridization to cultivated forms, are known to exist in India. Most of the germplasms, therefore, exist in the form of traditional varieties. Most of such varieties have been subjected to natural selection for local adaptation and therefore, these are expected to pose valuable genes for resistance against biotic and abiotic stresses. Good collections are also maintained in China (Coriander-99, Fennel-35)2, Australia (coriander and fenugreek), Germany (Coriander and fennel), Netherlands (Coriander and Fennel), USA (Coriander, fenugreek, fennel, and cumin), as well as the countries of Mediterranean region namely Morocco, Egypt, Iran, as well as horn of Africa (Ethiopia). Most of the European and North American as well as Australian collections are the introductions from either India or Mediterranean countries. Cumin is a major crop in Syria, and hence the country is expected to have good genetic diversity in cumin. (Sharma 1994; Malhotra and Vijay 2003; Singhania et al. 2005a, b, c; Sastry 2009, Agarwal and Sharma 1990).

The major seed spices grown in India are coriander, cumin, fennel, and fenugreek which are grown on a commercial scale. Cultivation of the remaining seed spices is limited to certain areas only. Three of the major seed spices, coriander (Coriandrum sativum L.), cumin (Cuminum cyminum L.), and fennel (Foeniculum vulgare Mill) belongs to family Apiaceae, whereas fenugreek (Trigonella foenum-graecum L.) belongs to Fabaceae 1986.

9.2.7.1 Coriander

Coriander is native to southern Europe, Asia Minor, and Caucasus where it also grows wild. Now India is a major producer of coriander. The diversity of coriander is rather limited in India. C. sativum var indicum belongs to India. The small fruited types are recognized as C. sativum L. var. microcarpum and the large fruited one are described as C. sativum L. var. vulgare (Diederichsen and Hammer 2003). The sub-species of C. sativum Subsp. Sativum are var. sativum and var. africanum Stolet. The Subsp. of C. sativum Subsp. asiaticum are var. asiaticum, var. anatolicum and var. afghanicum. The other sub-species are C. sativum Subsp. vavilovii var. vavilovii and C. sativum Subsp. pygmaeum Stolet.

Dried ripe coriander seeds contain both steam volatile oil and fixed oil. The aromatic odor and taste of coriander fruit is due to its volatile oil, which is a clear, colorless to light yellow liquid. The flavor of the oil is warm, spicy aromatic, sweet and fruity. The oil contents of seeds vary widely with geographical origin. Higher volatile oil content is found in Norwegian coriander (1.4–1.7 %) followed by Bulgarian coriander (0.1–0.5 %). Indian seeds are poor in volatile oil content (0.1–0.4 %) (Agrawal and Sharma 1990). Major components of essential oil are linalool (67.7 %), followed by α-pinene (10.5 %), γ- terpinene (9.0 %), geranyl acetate (4.0 %), camphor (3.0 %) and geraniol (1.9 %). Minor components in the oil are β-pinene, camphene, myrcene, limonene, p-cymol, dipentene, α- terpinene, n-decylaldehyde, borneol, and acetic acid esters.

There is good generic diversity in coriander with respect to morphological characters, quality attributes, and resistance to biotic and abiotic stresses. Over 2130 accessions are maintained at various centers in India (Karla et al. 2006; Sharma and Sharma 2012).

Thirty-five high-yielding coriander cultivars are released for cultivation in India (Table 9.8). These varieties exhibit diversity for fruit shape, size, and plant type. Many of them are resistance to biotic and abiotic stresses like wilt, powdery mildew, stem gall, grain mold, tolerance to drought, field tolerance to white fly, mites and aphids early maturity, dual-purpose types, resistant to lodging and shattering, etc.

Table 9.8 Species diversity in seed spices
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9.2.7.2 Cumin

Cumin is native to Egypt and Syria, Turkistan and Eastern Mediterranean region. Cuminaldehyde is the major component in cumin oil. Oil content is low in indigenous germplasm but high in exotic collections (Sharma 1994). Cumin is an aromatic spice with stimulating properties. It has a characteristic strong flavor and is slightly bitter in taste. Seeds contain 2–5 % volatile oil of which 40–65 % is cuminaldehyde (cuminic aldehyde). Over 590 accessions are maintained at various centers in India (Patel et al. 2006; Amin 2012).

Fourteen high-yielding cumin cultivars are released for cultivation in India (Table 9.8). The cv. RZ-19 is moderately resistant to wilt, having attractive fruits. Gujarat cumin-4 is wilt resistant and is the most important variety in India. Diversities for high yield, fruit shape and size, high quality, tolerance to Fusarium wilt, Alternaria blight and powdery mildew and rich in essential oil content exist among these improved varieties.

9.2.7.3 Fennel

Fennel belongs to Apiaceae. It has two sub-species: Foeniculum vulgare sp. Capillaceum (garden fennel) and ssp. Piperitura (wild fennel). Sub-species capillaceum comprises var. vulgare (bitter fennel), var. dulce (sweet fennel or French sweet fennel or Roman fennel) and var. panmoriwn (Indian fennel). The oil content ranges from 0.7 to 6 % in fennel germplasm. The oil of fennel contains mainly anethole, α-pinene, β-phellandrene, dipentene, etc. Over 629 accessions are maintained at various centers in India.

Twenty-one high-yielding fennel cultivars are released for cultivation in India (Table 9.8). These cultivars posses among themselves high yield, high quality, fruit shape and size, tolerance to leaf spot, leaf blight and sugary diseases, shattering of grains, suitability for drought, water logged and saline and alkaline conditions.

9.2.7.4 Fenugreek

Fenugreek belongs to the family Fabaceae, and is native of eastern Mediterranean. Rich diversity exists for fenugreek in Turkey. The seed is used as spice and leaf as vegetable. It has bitter taste of seeds due to alkaloid trigonelline and steroid sapogenin (diosgenin), but in appropriate quantities, it adds a special taste and flavor to culinary dishes. It also has high medicinal and nutritive value (Kakani and Anwer 2012). Over 1118 accessions are maintained at various centers in India.

Twenty-one high-yielding fenugreek cultivars are released for cultivation in India (Table 9.8). These cultivars in addition to high yield, high quality, grain size and color, dual-purpose types, with tolerance to downy mildew, powdery mildew, root rot, high diosgenin content, and medium duration types.

9.3 Genetic Erosion

Due to destruction in their natural habitats, climate change, over exploitation, preference to better yielding varieties many of the species, wild forms and primitive cultivars are slowly disappearing. Some of the important species which were classified by IUCN as rare, endangered and threatened (RET) are given in Table 9.9.

Table 9.9 Rare, endangered, and threatened (RET) species among spice crops
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All the spices crops like any other plant follow either vegetative or sexual reproduction. While many crops show strict self or cross pollination, yet, there are no fixed borders. Because of the sampling errors, the genetic structure of the population is affected; hence, there is danger of loss of valuable alleles in the collections due to the sampling procedures. Similarly, even during the regeneration and multiplication of the samples in germplasm collections also genetic erosion sets in. Before we understand the genetic erosion in nature and in germplasm collection, it is essential that we understand the reproduction in plants and its relation to population structure.

The genetic erosion can only be monitored when we are aware of the genetic resources of the area. The selection pressure on crops for yield has resulted in the erosion of land races which may be the allelic source of adaptability to a particular region. India being the center of diversity of many spices, the genetic variability in major spices like black pepper and cardamom followed by ginger, turmeric, cinnamon and garcinia is quite reasonable. The natural variability has to be preserved in the place of primary origin as well as in secondary origin by conservation as to escape the risk of extinction of the genetic variability. The wild species presumably became extinct because of over collection. Owing to the strong commercial pressure of food and pharmaceutical industries of today, unregulated gatherings have led to severe genetic erosion of a range of herbs and spices. The status of genetic erosion will be likely speeded up during the process of development of economy. The forest fire causes erosion of wild species and it results in the spread of rhizomatous crops present in the forest fire-infected region, as the aerial shoots get affected by this natural calamity, underground parts escapes the disaster, and further regenerate vigorously as there will be no competition (Table 9.9).

9.4 Conservation Strategies

Many wild and related species of spices still occur in the wild and are severely affected by both natural and manmade ecological disturbances. Identifying and demarking the ecological niches as protected biosphere reserves will help in in situ conservation of these valuable genetic resources for posterity. Most of the cross-pollinated tropical spices are either vegetatively propagated or have recalcitrant and heterozygous seeds. Spices like black pepper, cardamom, ginger, turmeric, and vanilla are essentially vegetatively propagated. Although essentially seed propagated, many tree spices like nutmeg, clove, cinnamon, and garcinia have efficient vegetative propagation methods. Hence, ex situ conservation in clonal repositories or in field gene banks (Fig. 9.3) is essential if we are to conserve these valuable genetic resources especially the cultivated types.

Fig. 9.3
figure 3

Clonal repositories of a black pepper, b cardamom, c ginger, d turmeric, e vanilla, and f nutmeg germplasm

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In many crop species like seed spices, conventional seed storage can satisfy most of the conservation requirements. Seed spices, except fenugreek, are highly cross-pollinated and if sufficient population (Oka 1975) and isolation distance is not maintained, the purity of the variety will get eroded and there will be a genetic drift. In them, maintaining an individual collection in small quantities always poses a problem and theoretically it will be very difficult to eliminate genetic erosion even on small scale. Another approach is to use the gene pool approach. In this, composites are synthesized so that all the genes belonging to constituent lines are conserved in at intermediate gene frequencies. This approach can be applied to annual cross-pollinated spice crops. So its important controlled pollination of minimum population is required to ensure generic purity in subsequent generations. Storing a population of seeds, depending upon the diversity and breeding behavior, in low-temperature seed storage will help in augmenting the seed storage. Because of the heterozygous and heterogeneous nature, the populations of seed spices are particularly vulnerable to changes in gene and genotype structure throughout breeding and selection. Hence, in order to maintain the proper genetic structure of a given collection, the following care should be taken (Breese 1989).

  1. 1.

    Avoid contamination by foreign pollen or seed through proper isolation and seed handling techniques (Fig. 9.4).

    Fig. 9.4
    figure 4

    Field gene bank of seed spices (Inset bagging to maintain purity of genotype)

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  2. 2.

    Minimize the genetic drift by ensuring sufficient population size and reducing opportunities for natural selections.

  3. 3.

    Securing effective random mating through appropriate pollination techniques.

Ex situ conservation is ideal as it maintains the population structure and allows the evolutionary forces to modify the population for better adaptation. Farmer’s fields also can be used for conservation Altieri and Merrick 1987; Brush 1991) of cultivars and varieties of seed spices, since we are dealing with cultivated species. Further, even now, farmers are still growing their traditional varieties.

However, crops with recalcitrant seeds and those having conservation needs cannot be satisfied by seed storage, which have to be stored in clonal repositories and in vitro gene banks. Most field gene banks are prone to high labor cost, vulnerable to hazards like natural disasters, pests, and pathogens attack (especially viruses and systemic pathogens), to which they are continuously exposed and require large areas of space. This supports in vitro and cryoconservation. In addition, other resources like continuous supply of standard stock cultures for experiments to examine physiological and biochemical processes, cell and callus lines developed for in vitro synthesis of valuable secondary products, flavors, and other important compounds will benefit strongly from in vitro cultures.

Many spices are plagued by destructive and epidemic diseases caused by viruses, bacteria, and fungi. This makes germplasm conservation in field gene bank risky. Thus in vitro (Fig. 9.5) and cryostorage system becomes important in the overall strategy of conserving genepool. Each technology should be chosen on the basis of utility, security, and complementarily to other components of the strategy. A balance needs to be struck between seed, field gene bank, in vitro and cryoconservation of propagules, tissues, pollen, cell lines, and DNA storage for overall objective of conserving gene pool (Adams 1997; Nirmal Babu et al. 2007, 2012).

Fig. 9.5
figure 5

In vitro gene bank of vegetatively propagated spices (Inset Ginger cultures under slow growth regime)

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Pollen storage can be considerable value supplementing the germplasm conservation strategy by facilitating hybridisation between plants with different times of flowering and to transport pollen across the globe for various crop improvement programs in addition to developing haploid or homozygous lines. Cryopreservation of pollen (Fig. 9.6) might represent an interesting alternative for the long-term conservation of problematic species (IPGRI 1996).

Fig. 9.6
figure 6

Viability and germination of cryo-preserved pollen in vanilla

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Consequent with the advancements in gene cloning and transfer has been the development of technology for the removal and analysis of DNA. DNAs from the nucleus, mitochondrion, and chloroplast are now routinely extracted and immobilized onto nitrocellulose sheets where the DNA can be probed with numerous cloned genes. These advances, coupled with the prospect of the loss of significant plant genetic resources throughout the world, have led to the establishment of DNA bank for the storage of genomic DNA. The advantage of storing DNA is that it is efficient and simple and overcomes many physical limitations and constraints that characterize other forms of storage (Adams et al. 1994).

At present, the germplasm collection of spices available in India is the largest in the world comprising cultivars, wild relatives and genotypes having special characteristics (Table 9.10). These are maintained at various research centers. The germplasm conservation is through field gene banks, seed banks supplemented by in vitro, cryogene banks and DNA storage, where ever possible, depending upon the crop involved.

Table 9.10 Genetic resources of major spices conserved at various centers in India
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The existing germplasm available at various centers in India was effectively utilized in selection, hybridization, and mutation breeding programs and over 150 varieties of spices with high yield and resistance to biotic and abiotic stresses were released (Table 9.11).

Table 9.11 Improved varieties of spices in India and their important characters
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9.5 Information System Support

The distribution of the wild species in the wild cannot be manually evaluated as it requires intensively more skilled personnel. GIS analysis of the germplasm data helps to better understand and develop new strategies for exploiting geographic diversity and to predict where species naturally occur or may be successfully introduced. Habitat loss and fragmentation are among the most common threats facing endangered species, making GIS-based evaluations an essential component of population viability analysis.

9.6 Conclusion and Prospects

The genetic resources which are the reservoirs of identified and unidentified different genes are always the source for study for the breeders of all generations. The primary and secondary centers of origin are the source for different germplasms due to the natural hybridization and flow of genes throughout their existence. Detailed study on germplasm gives us the source material for resistance to biotic and abiotic stresses which can be further used in the improvement aspect.

The factors contributing to erosion due to the enormous diversity in cultivated plants, population growth, deforestation, erosion, changing land use and climate factors are major threats to the existing biodiversity of the region.

Natural productivity of any given species is always less, as the survival and continuation of a species is more important in nature than productivity. However, under domestication, the crops have shown the reverse. Due to the efforts of the human being, the productivities of all the crops have constantly raised, and in turn the survival mechanisms of the crops have been put to stake. Thus, the natural balance of maintenance of different forms has been disturbed.

The wild species presumably became extinct because of over collection. Owing to the strong commercial pressure of food and pharmaceutical industries of today, unregulated gatherings have led to severe genetic erosion of a range of herbs and spices. The status of genetic erosion will be likely speeded up during the process of development of economy. The forest fire causes erosion of wild species, and it results in the spread of rhizomatous crops present in the forest fire-infected region, as the aerial shoots get affected by this natural calamity, underground parts escapes the disaster, and further regenerate vigorously as there will be no competition. Preserving the biodiversity hot spots as natural sanctuaries will certainly help in slow in the gene erosion.

Large-scale cultivation is one practice that can take the pressure off wild stocks. This can be possible only by identifying the commercial importance of the wild species and exploring the rare information in the wild species which helps in domestication of the plant genes by the farmers which are possible. Thus it becomes a valid concern to evaluate and utilize the materials.

In many spices, conventional seed storage can satisfy most of the conservation requirements. However, crops with recalcitrant seeds and those having conservation needs cannot be satisfied by seed storage, which have to be stored in vitro. Most field gene banks are prone to high labor cost, vulnerable to hazards like natural disasters, pests and pathogens attack (especially viruses and systemic pathogens), to which they are continuously exposed and require large areas of space.

Most of the spice crops are either vegetatively propagated or have recalcitrant seeds. The spices germplasm is mostly conserved in field gene banks. Most of the spices are plagued by destructive and epidemic diseases caused by viruses, bacteria, and fungi. This makes germplasm conservation in field gene bank risky. Thus in vitro and cryostorage system becomes important in the overall strategy of conserving gene pool. Each technology should be chosen on the basis of utility, security, and complementarily to other components of the strategy. A balance needs to be struck between seed, field gene bank, in vitro and cryoconservation of propagules, tissues, pollen, cell lines, and DNA storage for overall objective of conserving gene pool. The genetic resources of black pepper, cardamom, ginger, turmeric, and vanilla are best conserved in field clonal repositories supplemented in vitro gene banks of active germplasm, while field gene banks are sufficient for perennial tree spices. However, for seed spices, field gene banks field with controlled pollination to maintain the pollution structure is essential with annual resurrection. This should be supplemented by long-term storage of base germplasm in low-temperature seed banks, which is ideal. For all these crops, DNA and pollen storage will supply the conservation methods mentioned above. Certainly, this does not mean to say that in situ conservation through protection of their natural habitats is less important. In fact, all the native genes for crop improvement are in the wild populations and hence have to be protected under biosphere reserves for posterity.