Ascending migration of endophytic Bacillus thuringiensis and assessment of benefits to different legumes of N.W. Himalayas

Out of twenty seven Gram positive and spore forming Bacilli, four Bacillus thuringiensis (Bt) were obtained from root nodules of six legumes. Three bipyramidal and one spherical crystal producing B. thuringiensis were isolated from root nodules of ricebean, lentil, gahat (Horsegram) and soybean plant. Double Intrinsic Antibiotic Resistance (IAR) markers were developed to detect/monitor the presence of B. thuringiensis in the natural environment. B. thuringiensis isolates were examined for their ability to enhance plant growth and ascending migration (from roots to aerial plant part) in four legumes in plant growth chamber at 28 °C. Seed bacterization with B. thuringiensis isolates positively influenced the percent germination and enhanced the plant growth of ricebean, soybean, gahat, and lentil seedlings. All B. thuringiensis isolates were recovered from rhizosphere, root endophytic region, stem lower, upper part and leaf after 45 days after sowing (DAS). Isolate VRB1 was able to colonized rhizosphere and endophytic regions (root, stem and leaf) of gahat, soybean and ricebean after 45DAS. Similarly, isolate VL4C and VLS72.1 were able to colonize rhizosphere and endophytic regions (root, stem and leaf) of lentil and soybean. While, isolate VLG15 was able to colonized rhizosphere and endophytic regions (root, stem and leaf) of lentil, soybean and gahat. Therefore, this study suggests that this approach may be utilized for the development of insect resistant crop strategy in sustainable agriculture.

► We studied the ascending migration ability of Bacillus thuringiensis in four legumes.
► Four Bacillus thuringiensis (Bt) were obtained from root nodules of six legumes.
► B. thuringiensis VRB1 colonized rhizosphere and endophytic regions of three legumes.
► Bt isolates VL4C and VLS72.1 colonized rhizosphere and endophytic regions of lentil and soybean.
► This approach may be an alternate choice for the development of insect resistant crop.