Studies on association of arbuscular mycorrhizal fungi with gluconacetobacter diazotrophicus and its effect on improvement of sorghum bicolor (L.)

Considerable attention has been paid on endophytic diazotrophs in recent times, because of its of ability to fix and transfer fixed nitrogen to the host plant. Arbuscular mycorrhizal (AM) fungi are ubiquitous and play a significant role in improving the growth of plants through better uptake of nutrients, especially phosphorus. Interaction between AM fungi and nitrogen fixing bacteria and its impact on the host plant has been studied in several instances. In the present study, an attempt has been made to know the combining ability of G.diazotrophicus with AM fungi on S.bicolor. Spores of ten species of AM fungi were isolated from the rhizosphere soils of S.bicolor from different localities of Madurai and Sivagangai districts of Tamil Nadu. G.diazotrophicus was isolated from stem tissues of sugarcane (Saccharrum officinarum L.) from Madurai districts. The AM fungi in association with G.diazotrophicus were evaluated on the basis of root colonization, fresh and drymatter yield, N, P, soluble sugars and photosynthetic pigments in leaves of S.bicolor. Fresh weight and dry weight was significantly higher in dual inoculated plants. The highest values were recorded with Glomus fasciculatum + G.diazotrophicus combination. AM fungal infection was significantly higher in dual inoculated plants. N concentration was significantly increased by G.diazotrophicus even more in association with the efficient fungal strains. Dual inoculated plants showed a significant increase in P, soluble sugars, photosynthetic pigments in leaves was observed in G.diazotrophicus + Glomus fasciculatum combination. Such morphological modification may enhance water and nutrient uptake. Our results confirm the importance of studying plant-microbial interrelationship to provide useful information for agricultural system management