Association of toxicity of native Bacillus spp. with its total protein content against neonates of fall armyworm, Spodoptera frugiperda

A study was conducted to evaluate the toxicity of native Bacillus spp. against fall armyworm, Spodoptera frugiperda where cell suspension and culture supernatant of the native Bacillus were extracted and diet incorporation method of bio-assay was carried out to check their efficacy. Total crude protein content of Bacillus isolates was estimated using Bradford method and correlated with their efficacy. The efficacy of Bacillus isolates against fall armyworm was found maximum at 48 h old cell culture than 24 and 72 h. Among the Bacillus strains, VKK-SL2 (26.67%) showed higher corrected mortality next to VKK9 (73.33%), followed by VKK-AG1 (23.0%) and VKK-SO (16.67%) at 48 h of cell harvest. Among the native Bacillus strains, the VKK9 showed good efficacy against neonates of FAW while VKK-SO was found to be least toxic to FAW. The protein content of cell suspension of the native Bacillus strains lied in the range of 0.89-3.89 μg/mg and 0.87 - 2.95 μg/mg in reference Bt strains at 24 h of incubation. Among the native strains, VKK-MPW and VKK9 were found to have maximum protein content in cell pellet suspension of 2.34 and 3.25 μg/mg, respectively. In our study, we found that the native Bt isolates showed good efficacy in the range of 0 - 73% mortality against neonates of Spodoptera frugiperda at 24 h old cell pellet suspension while the efficacy was lower in 48 and 72 h old cultures. The toxicity and protein content of the native Bacillus strains were found to be positively correlated.