141 SCREENING OF ARBUSCULAR MYCORRHIZAL FUNGI ASSOCIATED WITH PERSEA BOMBYCINA KOST AND THEIR EFFECT ON IMPROVEMENT OF PLANT HEALTH B.N.Chakraborty 1*, A.Acharya 1 , U.Chakraborty 1 , J.Rabha 2 , D.K.Jha 2 1 Immouno-Phytopathology Laboratory, Department of Botany, University of North Bengal 2 Microbial Ecology Laboratory, Department of Botany, Gauhati University E mail: bncnbu@gmail.com ABSTRACT Persea bombycina Kost, locally known as Som plant is an economically important plant in the North-Eastern region of India which is the primary food plant of the muga silk worm Antheraea assama Westwood. The association of AMF with the Som plants was studied and their diversity was assessed in eight morphotypes. Among these, Glomus sp, Scutellospora sp, Acaulospora sp and Gigaspora sp were found associated with the different morphotypes of Som plants, wherein Glomus sp was predominant. Mass multiplied spores were further inoculated in all eight morphotypes separately. Histopathology of AMF colonized roots of Som plants revealed the presence of intra and inter radical hyphae, vesicles and arbuscules showing the colonization of AMF within the roots of the plant. Growth promotion in Som plants following successful root colonization with AMF was noted in terms of increase in height, no of leaves and no of branches. Plants inoculated with AMF also showed high phosphate solubilizing activity. Two main defense enzymes in plants, Phenylalanine Ammonia Lyase(PAL) and Peroxidase (POX) were found higher in AMF inoculated plants in comparison to control plants indicating induced resistance in Som plants. Keywords: Arbuscular Mycorrhizal fungi, Persea bombycina Kost , Glomus sp, Growth promotion. Persea bombycina (King ex Hook. f.) Kost, locally known as “ Som” is one of the primary food plants of Antheraea assama Westwood, the silkworm that produces muga, or golden colour natural silk. “ Som” belongs to the family Lauraceae, a medium size evergreen tree with spreading branches, bark and foliage usually aromatic, alternate leaves grows abundantly in its natural habitat in Assam particularly Brahmaputra Valley up to an elevation of about 500 meters, apart from its distribution that extends to Khasi and Jayantia Hillls in India, along the Lower Himalaya and as far as to the west of Nepal. Persea bombycina is one of the commercially and economically important plant of the North-east region of India since its leaves are consumed by the muga silkworm and the quality of these leaves in turn affect the quality of the silk produced. There are atleast 51 genotypes of Som plants (S1 – S51) classified based on leaf shape. The most preferred ones are S3 and S6. Arbuscular-mycorhizal fungi (AMF) are soil microbes forming symbiotic association with plant root system of all most all plant species. The fungi from the Phylum Glomeromycota are the major Arbuscular-mycorrhiza forming species. These associations benefit the host plants by increasing the growth, nutrient uptake and defense mechanisms (Mehta et al., 2013). AM fungi like Glomus mossae, G.fasciculatum and some species of Acaulospora, Gigaspora and Scutellospora have been reported to remain associated with different plants such as apple (Bharat and Bhardwaj, 2002), tobacco (Subhashini, 2013), Mandarin (Allay et al, 2012) etc. However reports of association of AM Fungi with plants involved in Sericulture is very meager. Considering the importance of association of AMF, an efforts were made in the present investigation to study the population of mycorrhizal fungi associated with eight different morphotypes of Som plants and their effect on the improvement of health status of the plant. MATERIAL AND METHODS Plant material Eight different morphotypes of Som plants (S1, S2, S3, S4, S5, S6, S7 and S8) considered for the study and were collected from Central Silk Board, Boko, Assam. These plants were grown under green house conditions in Immuno- Phytopathology Laboratory, Department of Botany, North Bengal University and were also transplanted to the experimental field of Department of Botany, NBU for field based investigations. Isolation of AMF spores from soil Arbuscular mycorrhizal fungal spores were screened from the rhizospheric soil collected from the S3 and S6 morphotypes of Som plants cultivated in Shivsagar and Jorhat district of Assam respectively following the Wet sieving and Decanting method (Gerdemann and Nicholson,1963). Approximately 250g of soil was suspended in 1litre or more of water. Heavier particls were allowed to settle for few seconds and the liquid was decanted through sieves of various stainless steel mesh (60, 85, 100, 150,175 and 200m), fine enough to remove the larger particles of organic matter but coarse enough for the desired particles to pass through. J.Pl.Dis.Sci.Vol 8(2) 2013 : 141-147