Abstract
A study was conducted to identify common arbuscular mycorrhizal (AM) fungi present in rhizosphere of Jatropha curcas L., an important bio-diesel crop, from different arid and semi arid regions of India viz., Jodhpur (Rajasthan), Hissar (Haryana), Jhansi and Lalitpur (Uttar Pradesh) and Hyderabad (Andhra Pradesh). A total of 20 AM species were recorded, which consisted of two species of Acaulospora and 18 species of Glomus. The highest frequency of occurrence was recorded for Glomus intraradix (100%), followed by Acaulospora scrobiculata (83%), G. etunicatum (50%) and Glomus 1 (50%). Maximum species richness was recorded at Jodhpur, followed by Jhansi, Hissar, Hyderabad and Lalitpur. The results seem to suggest that species richness was more in arid regions as compared to semi arid areas.
Keywords: Acaulospora, Arid and semi arid regions, Arbuscular mycorrhizal fungi, Glomus, Jatropha curcas
Inoculations of Jatropha curcas L., which is gaining importance as bio-diesel plant, with bio-fertilizers including arbuscular mycorrhizal (AM) fungi have been shown to significantly increase the plant growth and yields under variable conditions. Morphological and biochemical contents of Jatropha plants have been reported to increase significantly after combined microbial inoculations with Azospirillum, Azotobacter, phosphate solubilising bacteria and AM fungi under tropical conditions of Tamil Nadu [1]. Early flowering and fruiting in J. curcas has been reported after inoculation of plants with microbial formulations [2].
Above-mentioned information is mostly based on commercial formulations involving unidentified AM species and other bio-fertilizers. Studies on effect of inoculation of purified AM cultures, isolated from diverse conditions, on growth of J. curcas could be helpful in realization of full potential of these fungi as bio-fertilizers, as it has been done in many other plant species [3]. To begin with, efforts were made in present study to identify common AM fungi present in rhizosphere of J. curcas from different arid and semi arid regions of India viz., Hissar (Haryana), Hyderabad (Andhra Pradesh), Jodhpur (Rajasthan), Jhansi and Lalitpur (Uttar Pradesh). Pantnagar (Uttaranchal) was also included in this study as occurrence of J. curcas in lower hills is quiet common.
The study was conducted at National Research Centre for Agroforestry, Jhansi (24°11′ N latitude and 78°17′ E longitudes), Uttar Pradesh, India. A total of 30 samples of rhizosphere soil were collected from above mentioned locations, five from each location during 2007–2008. Trap cultures were set by mixing different soil samples with autoclaved coarse sand in 1:1 ratio (v/v), separately. The mixture was transferred to 15 cm plastic pots, which were seeded with maize and black-gram and were maintained in green house. After 3–4 months, spore/sporocarps were isolated from the substrate taken from the trap cultures according to the method of Geredmann and Nicolson [4]. AM species were identified by using the keys of Schenck and Perez [5]. Species richness and frequency of occurrence of AM fungi associated with different locations were also calculated [6]. Soil properties and other details of different sampling sites are given in Table 1.
Table 1.
Soil characteristics and other details of different sampling sites
| Location | Soil order | Application of fertilizers | Type of plantation | pH (1:2.5 H2O) | EC (μS/cm) | Organic C (%) | Olsen P (Kg/ha) |
|---|---|---|---|---|---|---|---|
| Hissar | Entisol | Yes | Pure plantation | 8.4 | 120.0 | 0.47 | 12.0 |
| Hyderabad | Vertisol | Yes | Pure plantation | 6.6 | 110.0 | 0.48 | 13.5 |
| Jhansi | Vertisol | Yes | Agroforestry | 6.5 | 189.4 | 0.74 | 23.4 |
| Jodhpur | Aridisol | Yes | Pure plantation | 8.1 | 200.0 | 0.15 | 10.0 |
| Lalitpur | Vertisol | No | Naturally growing plants | 7.6 | 142.0 | 0.71 | 8.5 |
| Pantnagar | Mollisols | Yes | Pure plantation | 7.1 | 365.0 | 0.81 | 27.9 |
A total of 20 AM species were recorded, which consisted of two species of Acaulospora and 18 species of Glomus (Table 2). Frequency of occurrence varied from 17 to 100%. Its maximum value was recorded for G. intraradix (100%), followed by A. scrobiculata (83%), G. etunicatum (50%) and Glomus 1 (50%). There are many reports which suggest the presence of rich AM biodiversity in rhizosphere of J. curcas from different parts of India. Jamaluddin and Singh [7] reported ten AM species from black cotton and red murumy soils of Jabalpur, Madhya Pradesh. Venkatesh et al. [8] reported the presence of Glomus, Sclerocystis, Gigaspora, Scutellospora and Acaulospora sp., from three agro-climatic zones of Karnataka. Among the surveyed locations, excellent AM species richness was recorded in aridisol of Jodhpur (pH: 8.1) and entisol of Hissar (pH: 8.4). It seems that AM fungi of the region have good adaptation to high pH values. Hasan [9] reported similar results from alkaline soils of Faizabad, Uttra Pradesh. A large number of AM species (Glomus mosseae, G. fasciculatum, Gigaspora margarita, G.gigantea and Acaulospora laevis) were isolated from the farm soil. Among studied vertisols, maximum richness was recorded at Jhansi (pH: 6.5), followed by Hyderabad (pH: 6.6) and Lalitpur (pH: 7.6). The samples from Jhansi were taken from an agroforestry plot (Table 1) and it could be the reason for recorded higher AM biodiversity there. The observations are in accordance with existing reports on stimulatory effects of intercropping on AM activity in tree rhizosphere in agroforestry systems [10]. Relatively lesser number of AM species was recorded in mollisols from Pantnagar, which can be due to higher level of soil phosphorus (P).
Table 2.
Occurrence of arbuscular mycorrhizal (AM) species in rhizosphere of Jatropha curcas at different sampling locations
| AM species | AM species recorded at | Frequency of occurrence (%) | |||||
|---|---|---|---|---|---|---|---|
| Hissar | Hyderabad | Jhansi | Jodhpur | Lalitpur | Pantnagar | ||
| A. mellea | − | − | − | + | − | − | 17 |
| A. scrobiculata | + | − | + | + | + | + | 83 |
| Glomus aggregatum | − | − | + | + | − | − | 33 |
| G. arborense | − | − | + | + | − | − | 33 |
| G. cerebriforme | + | − | − | − | − | − | 17 |
| G. diaphanum | − | − | + | − | − | − | 17 |
| G. etunicatum | + | + | + | − | − | − | 50 |
| G. hoi | − | + | − | + | − | − | 33 |
| G. intraradix | + | + | + | + | + | + | 100 |
| G. microaggregatum | + | − | − | + | − | − | 33 |
| G. microcarpum | + | − | − | − | − | − | 17 |
| G. occultum | − | − | − | − | − | + | 17 |
| G. segmentatum | − | − | − | + | − | − | 17 |
| G. vesiculiforme | + | − | − | − | − | − | 17 |
| Glomus 1 | + | − | + | + | − | − | 50 |
| Glomus 2 | − | − | + | − | − | + | 33 |
| Glomus 3 | − | − | + | + | − | − | 33 |
| Glomus 4 | − | − | − | + | − | − | 17 |
| Glomus 5 | − | − | − | + | − | − | 17 |
| Glomus 6 | − | − | − | + | − | − | 17 |
| Species richness | 8 | 3 | 9 | 13 | 2 | 4 | |
+ Present, − Absent
It may be concluded from above observations that Glomus and Acaulospora were the common genera of AM fungi present in rhizosphere of J. curcas in the surveyed regions. Species richness is more in arid regions as compared to semi arid and sub humid areas. Natural soils in aforesaid areas are predominantly low in P content, except Pantnagar and are favorable for growth of AM fungi.
Acknowledgments
The authors are thankful to Director, National Research Centre for Agroforestry, Jhansi for providing the facilities and University Grant Commission, New Delhi, for Post Doctoral Fellowship to the senior author.
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