Screening of efficient arbuscular mycorrhizal fungi for Azadirachta indica under nursery condition: a step towards afforestation of semi-arid region of western India

Brazilian Journal of Microbiology 44, 2, 587-593 (2013) ISSN 1678-4405 Copyright © 2013, Sociedade Brasileira de Microbiologia www.sbmicrobiologia.org.br Research Paper Screening of efficient arbuscular mycorrhizal fungi for Azadirachta indica under nursery condition: A step towards afforestation of semi-arid region of western India K. Banerjee1, M.H. Gadani1, K.K. Srivastava2, Neelam Verma2, Y.T. Jasrai3, N.K. Jain4 1 Gujarat Forest Research Institute, Research Division, Gujarat, India. 2 Arid Forest Research Institute, Rajasthan, India. 3 Dept. of Botany, University School of Sciences, Gujarat University, Gujarat, India. 4 Department of Life Sciences, University School of Sciences, Gujarat University, Gujarat, India. Submitted: June 10, 2011; Approved: June 5, 2012. Abstract To optimize nursery practices for efficient plant production procedures and to keep up to the ever growing demand of seedlings, identification of the most suitable species of arbuscular mycorrhizal fungi (AMF), specific for a given tree species, is clearly a necessary task. Sixty days old seedlings of Neem (Azadirachta indica A. Juss) raised in root trainers were inoculated with six species of AMF and a mixed inoculum (consortia) and kept in green house. Performances of the treatments on this tree species were evaluated in terms of growth parameters like plant height shoot collar diameter, biomass and phosphorous uptake capabilities. Significant and varied increase in the growth parameters and phosphorous uptake was observed for most of the AMF species against control. Consortia culture was found to be the best suited AMF treatment for A.indica, while Glomus intraradices and Glomus mosseae were the best performing single species cultures. It is the first time in the state of Gujarat that a wide variety of AMF species, isolated from the typical semi-arid region of western India, were tested for the best growth performance with one of the most important tree species for the concerned region. Key words: arbuscular mycorrhizal fungi, Neem, Glomus mosseae, Glomus intraradices. Introduction Neem (Azadirachta indica A. Juss) is one of the most important tree species in the western part of the Indian subcontinent, especially in the state of Gujarat. Every year a large target is set to the Gujarat State Forest Department to produce seedlings of this tree species in abundance in the nursery to meet various objectives including a rigorous afforestation program. Attempts are often made to reclaim degraded soils and wastelands of this part of the country with these nursery raised seedlings as a part of these activities. Neem which is an important multipurpose tree species has been observed to be well suited to all kinds of lands and wide range of environment (Tewari, 1992), especially tolerant to poor soils of arid and semi arid regions (Benge, 1989) and hence makes an obvious choice for the mission. Rapid production of high quality seedlings in nurseries is a pre-requisite for any aggressive re-forestation program, but it has been observed earlier (Michelsen, 1992) that optimal nursery conditions can hardly be achieved for quality seedling production. Moreover, there may be severe shortage in microbial populations including arbuscular mycorrhizal fungi (AMF) owing to the fact that soils used in the nursery are often collected from barren surroundings, subsoil or may have been stored for a long time (Muthukumar et al., 2001). AMF is an imperative component of soil microbial biomass influencing essential processes at the plant+soil interface (Harley and Smith, 1983; Bagyaraj, 1984; Rajan et al., 2000). To counteract the transplantation shock seedlings of tropical tree species raised in the nursery may need to be associated with AMF (Urgiles et al., 2009) besides gaining several conventional benefits of AMF association in terms of growth and nutri- Send correspondence to K. Banerjee. Gujarat Forest Research Institute, Research Division, `j’ Road, Sector 30, Gandhinagar 382 020, Gujarat, India. E-mail: . 588 ent uptake. It may further be noted that in vitro culture of AMF is rather cumbersome and hence a large quantity of inoculum production is highly cost ineffective to warrant inoculation of the soil under field condition. Inoculation in the nursery, on the contrary, may provide dual benefits of being inexpensive and providing better vigour of seedlings to cope with transplantation. AMF are rather obligate symbionts and their role in plant growth and nutrient uptake is well documented (Srinivas et al., 1988; Arya, 1999; Sumana and Bagyaraj, 1999; Garg et al., 1999; Kumar et al., 2000; Bhattacharya et al., 2000; Sharma and Adholeya, 2000; Prasad, 2002). It has been observed that roots of Neem are profusely colonized by AMF and it is considered as a highly mycorrhizal dependent tree species (Habte et al., 1993). Most AMF can form association with susceptible plants, regardless of the genetic diversity or geographical distribution of the two symbionts. Furthermore, the formation and function of mycorrhizas can be quite variable among fungal species and even among isolates of the same species (Smith and Smith, 1997; Smith et al., 2000). A fairly wide range of functional diversity in AMF could have lead to the observed differences among fungal species in the manner they facilitate host plants in resisting biotic and abiotic stress (Smith and Read, 1997). It is, however, more conventional to define in terms of plant growth responses, which may vary monotonically from unprecedented increment in growth to neutral depending on the particular plant-fungus combinations and environmental conditions (Johnson et al., 1997). Plant fungus combinations that promote optimum plant growth are believed to be those that provide the greatest amount of Pi to the plant for the least amount of photosynthate transferred to the fungus (Burleigh et al., 2002). Further, it was reported that different species of AMF differ to the extent by which they increase nutrient uptake and plant growth (Bagyaraj et al., 1989). Hence, the need for selecting efficient AMF that can be used for inoculating different plants was emphasized (Bagyaraj et al., 1989). Most of the studies performed earlier in this context are either highly region specific or symbionts specific and knowledge base is far from sufficient as far as the western part of India is concerned. The objective of the present study was to screen the AMF species, isolated from the semi-arid region and local AMF isolated from the rhizosphere of Neem in order to select an efficient inoculant species of AMF for Neem in nurseries. Materials and Methods Experimental site The study was conducted at the forest nursery of Basan Research range, Gandhinagar, Gujarat (23°13’ N: 72°41’ E, altitude: 80 m). The Gandhinagar district has multi seasonal climate with an average precipitation of 667 Banerjee et al. mm. Minimum temperature records 7.5 °C in winter and maximum temperature records 4 (...truncated)