Includes bibliographical references.

Maize (Zea mays L.) is the 3rd most important cereal crop in India (production of 27.64 million tons). In the North East region of India, maize is a staple cereal second to rice. In Meghalaya, the production of maize was 44132 M.T. with a cultivated area of 19482 ha with the average production of 2265 kg/hectare during the period 2022-23. Bacillus thuringiensis (Bt) is a key microbial agent for eco-friendly management of Fall Armyworm (FAW), which is a serious pest of maize. This study focuses on isolating and characterizing various Bt strains from Meghalaya showing vip genes and assessing their toxicity against Fall armyworm, Spodoptera frugiperda (J.E. Smith). A total of 99 samples were collected from 33 different locations representing 15 Blocks within 3 districts of Meghalaya. ‘Sodium acetate’ method was followed for isolation of Bt from soil. A total of 297 Bt like colonies were obtained, out of which 11 isolates were identified as Bt through morphological, microscopical and molecular characterization. Phase contrast microscopy revealed the presence of parasporal bodies in all the 11 isolates. Molecular identification was carried out using universal primers for 16S rRNA gene (27F and 1492R primers) and for cry gene (Lepidopteran specific) Un1 primer was used. Among 11 isolates, 6 native Bt isolates showed the presence of vip3A gene. These isolates also showed the presence of specific vip genes viz., vip3Aa and vip3Ab, which were further examined by bioassay studies. Maximum quantity of extractable insecticidal toxin (vip) was found in the strain WKH-K-2 (3.44 μg/μl) followed by WKH-NP-2 (1.57 μg/μl) and lowest in RB-BH-1 (0.36 μg/μl), respectively through standard Bradford method. Initially, selective bioassays were carried out in 2 different concentrations, i.e., 1 and 7 ppm against 1st and 2nd instar larvae and observation was done at 4th and 7th days with protein extracts in order to screen the most effective strains against FAW. Results revealed that out of 6 Bt isolates, one isolate showed 100% mortality in 7th day exposure of the toxin in 1 ppm concentration and performed better than the reference strains (4D1 Bt serovar. kurstaki) against FAW. Dosage based bioassays along with the reference strain 4D1 were carried out in five different concentrations 0.01, 0.1, 1, 2 and 3 ppm; along with one control. The native strain performed better with a lower LC50 value of 2.05 μg/ml and 0.037 μg/ml on 4th and 7th day respectively than the reference strain 4D1, with LC50 value of 2.89 μg/ml and 0.053 μg/ml on 4th day and 7th day, respectively. This isolate can be utilized to develop new bioinsecticides, which can be integrated into lepidopteran pest management programme.