Introduction

In India, bamboo encompasses about 8.96 million hectares of forest area and its present usage is to the tune of Rs. 2,043 crores. Over the next 2 years the projected rate of growth could be as high as 20% per year. Bamboo, being an important forest produce, plays a vital role in the rural economy of our country. In order to meet the future demand of bamboo, its growth and productivity has to be hastened from the nursery stage onwards. Inoculations of different bamboo species with bio-fertilizers including arbuscular mycorrhizal (AM) fungi have been shown to significantly increase the plant growth and yield under variable conditions. In Tamilnadu, Ravikumar et al. [1] have reported significant increase in the growth and biomass production of Dendrocalamus strictus Nees. After inoculation with Glomus aggregatum Schenck & Smith emend. Koske, G. fasciculatum Becker & Gerdemann and G. mosseae Gerdemann & Trappe. Similarly, Muthukumar and Udaiyan [2] have reported that combined microbial inoculations (Glomus aggregatum, Bacillus polymixa and Azospirillum brasilense) in two soil types (alfisol and vertisol) with or without fertilizer application significantly increased growth of D. strictus. From Central India, Dash et al. [3] have reported higher growth and biomass production of D. strictus, Bambusa bambos (L.) Voss. and B. vulgaris Wendl. ex Nees, after inoculation with an unidentified AM species. Gautam and Maitra [4] have reported increase in height and culm production in D. strictus after inoculation with G. macrocarpum Tul. et Tul. Jamaluddin et al. [5] have reported significant increase in growth and biomass of B. nutans G. C. Wall. ex Munro after inoculation with AM inoculum obtained from rhizosphere of field grown plants of B. nutans, which contained G. mosseae, G. intraradix Schenck & Smith and an unidentified species of Gigaspora.

Above-mentioned information is mostly based on commercial formulations involving unknown AM endophytes or limited number of AM species. The present study was carried out to find out the effect of common AM fungi isolated from rhizosphere of bamboo and other important agroforestry tree species of Bundelkhand region on seedling growth and biomass production of two bamboo species viz., B. bambos and D. strictus. Both bamboo species have been found suitable for cultivation in semi-arid conditions of Bundelkhand region [6].

Materials and Methods

The study was conducted at National Research Centre for Agroforestry (NRCAF), Jhansi (25o27′ N latitude, 78o35′ E longitude and at 271 m above msl) during 2008–2009. On agro-ecological zone map of India, Jhansi lies in the hot semi-arid region. The area receives annual rainfall between 700 and 1150 mm mostly during South West monsoon period (Mid June–September) with an average of 52 rainy days per year. Mean maximum temperature ranges from 47.4°C (June) to 23.5°C (January) and mean minimum temperature from 27.2°C (June) to 4.1°C (December). Diurnal variation in temperature is quite high. May and June are the hottest months. The maximum recorded temperature on a particular day often touches 47–48°C during summer.

Native AM fungi were isolated from the soil samples collected from rhizosphere of D. strictus from five sites of Baruasagar, district Jhansi by following procedure. Each sample was mixed in 1:1 ratio (v/v) with autoclaved coarse sand, separately and transferred to 15 cm plastic pots, which were seeded with maize and black-gram. The trap plants were grown in greenhouse for 4 months. For purification of AM fungi, spore/sporocarps were extracted by wet sieving and decantation method [7] from the pot culture material and were used to inoculate pre-geminated seedlings of sorghum, which were immediately transplanted, watered gently and placed in a room with indirect lighting for 24 h and then moved to greenhouse. Purified AM species were characterized by using standard methods [8] and multiplied on maize.

Separate net house experiments were laid out for B. bambos and D. strictus on the response of their seedlings to AM inoculations. Treatments consisted of five AM species isolated from rhizosphere of D. strictus (Acaulospora scrobiculata Trappe, Glomus aggregatum Schenck & Smith emend. Koske, G. arborense McGee, G. diaphanum Morton and Walker and G. intraradix Schenck and Smith), seven other purified cultures available in lab (A. mellea Spain & Schenck, G. cerebriforme McGee, G. etunicatum Becker & Gerdemann, G. fasciculatum Thaxter, G. hoi Berch & Trappe, G. occultum Walker and an unidentified Glomus species) and control (un-inoculated seedlings). Each treatment was replicated four in completely randomized design (CRD). Red soil (alfisol) was used as substrate, its chemical properties were as follows: pH 6.29 (1:2.5 H2O), EC 134 μS cm−1, OC 0.27%, Olsen P 2.5 ppm. The soil was passed through 2 mm sieve, moistened and filled in cotton bags and autoclaved for 8 h at 15 psi. The sterilized soil was potted in 7–8 kg capacity plastic pots, seeds were sown and inoculation with different AM fungi was done by using 50 gm of mycorrhizal inoculum as per treatments. The pots were kept under green house conditions and watered as and when required. After germination one healthy plant was maintained in each pot. The observations were recorded after 4 months of sowing on shoot length, fresh and dry weights and P concentration [9]. Mycorrhizal dependency (MD) was calculated according to Plenchette et al. [10]: [(M-NM)/M] × 100, where: M is the total dry biomass of mycorrhizal plant; NM is the total dry biomass of non-mycorrhizal plant. The data were statistically analyzed by ANOVA and the differences among means were tested by using critical difference (C.D.) values at 5% level of probability [11].

Results and Discussion

Six AM species, one belonging to genus Acaulospora (A. scrobiculata) and five to Glomus (G. aggregatum, G. arborense, G. diaphanum, G. intraradix and G. invermayanum) were recorded and isolated from rhizosphere of naturally growing plants of D. strictus from local forest area (Table 1; Fig. 1). Appasamy and Ganapathy [12] have reported the presence of G. albidum Walker & Rhodes from the rhizosphere of a bamboo species, Ochlandra travancorica Benth. from Ponmudi, Kerala. Results on effect of inoculation of different AM species on growth and P uptake by the bamboo seedlings are presented in Table 2. In B. bambos, eight AM inoculants (G. aggregatum, G. arborense, G. cerebriforme, G. fasciculatum, G. hoi, G. intraradix, G. occultum and an unidentified Glomus 1) significantly increased shoot length. Dry shoot weight was increased by all the treatments, except G. etunicatum while dry root weight was increased by all the treatments, except G. diaphanum. Total dry weight and P uptake were significantly increased by all studied fungi. Maximum MD values were recorded for A. scrobiculata (44.2%), followed by G. cerebriforme (41.6%) and G. intraradix (41.0%). MD of AM fungi isolated from D. strictus (A. scrobiculata, G. aggregatum, G. arborense, G. diaphanum and G. intraradix) varied from 29.0 to 44.2 and other AM fungi from 27.3 to 41.6. In D. strictus, all tested AM inoculants significantly increased shoot length, dry shoot weight and P uptake, except Glomus 1. Dry root weight was significantly increased by only two inoculants namely G. cerebriforme and G. etunicatum. Total dry weight was significantly increased by eight AM fungi (A. scrobiculata, G. aggregatum, G. arborense, G. cerebriforme, G. diaphanum, G. etunicatum, G. hoi and G. intraradix). Maximum MD values were recorded for G. cerebriforme (62.9%), followed by G. diaphanum (55.0%) and G. etunicatum (51.3%). MD of AM fungi isolated from D. strictus varied from 39.2 to 55.0 and other AM fungi from −15.2 to 62.9.

Table 1 Characteristics of arbuscular mycorrhizal (AM) species isolated from rhizosphere of Dendrocalamus strictus
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Fig. 1
figure 1

Common arbuscular mycorrhizal species recorded in rhizosphere of bamboo in Bundelkhand region a Acaulospora scrobiculata in melzer’s reagent (×400); b Glomus aggregatum (×400); c G. arborense (×400); d G. diaphanum (×400); e G. intraradix (×400); f G. invermayanum (×400)

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Table 2 Effect of inoculation of different arbuscular mycorrhizal species on growth and phosphorus uptake of Bambusa bambos and Dendrocalamus strictus 4 months after sowing
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Bamboo, being a fast growing plant, requires more nutrients during the initial stage of seedling establishment. During this period, the root system is not well developed and the AM fungal symbiosis might play a vital role by supplying the nutrients to the host plant [2]. The results of present study showed that mycorrhizal inoculations increased the plant growth and P uptake in different treatments with a few exceptions. Similar results have been reported in different bamboo species viz., D. strictus [1], B. bambos and B. vulgaris [3] and B. nutans [5] under variable conditions. This can be due to increase in the soil volume explored for nutrient and water uptake by the mycorrhizal plants from soil solution as compared to non-mycorrhizal plants. Generally, better nutrient (especially P) and water uptake leads to increase in biomass [13]. Among the two bamboo species studied, higher growth was noticed in D. strictus over B. bambos. The results are in conformity with Dash et al. [3].

Thus, in conclusion, it can be stated that in B. bambos, best results were obtained with A. scrobiculata (MD: 44.2%), Glomus cerebriforme (MD: 41.6%) and G. intraradix (MD: 41.0%) whereas, in D. strictus, higher growth and P uptake were noticed with G. cerebriforme (MD: 62.9%), G. diaphanum (MD: 55.0%) and G. etunicatum (MD: 51.3%). Among the two bamboo species studied, higher growth was recorded for D. strictus over B. bambos.