Toxicological impacts of neoteric Vip3A toxins from <i>Bacillus thuringiensis</i> on survival and development of <i>Spodoptera frugiperda</i> and <i>S. litura</i>

The toxicity of Vip3A proteins encoded by <i>vip3Aa44, vip3Aa67, vip3Aa68, vip3Aa69</i> and <i>vip3Aa72</i> genes previously cloned from Indian <i>Bacillus thuringiensis</i> isolates and BGSC strains in our laboratory was investigated toward <i>Spodoptera frugiperda</i> (Fall army worm, Lepidoptera: Noctuidae) and <i>S. litura</i> (tobacco cutworm/ cotton leaf worm, Lepidoptera: Noctuidae). Diet incorporation bioassays were performed using five toxins for <i>S. frugiperda</i> and three toxins for <i>S. litura</i> neonates. The LC₅₀ values for <i>S. frugiperda</i> and <i>S. litura</i> ranged from 1.381 to 13.509 ppm and 3.538 to 13.233 ppm<i>,</i> respectively, indicating higher susceptibility of <i>S. frugiperda</i> towards these toxins as compared with <i>S. litura</i>. Investigation of the impact of expressed Vip3A proteins on the development of <i>S. frugiperda</i> and <i>S. litura</i> revealed considerable post-larval mortality along with various sub-lethal effects on growth and fecundity. These sub-lethal effects encompassed reductions in larval and pupal weights across the concentration spectrum, prolonged generation period, and malformations in pupae and adults. Vip3Aa69 protein was found to be the most toxic among all proteins tested for both insects. Together with our previous study, in which Vip3Aa69 was found to be most toxic to <i>Helicoverpa armigera</i>, this toxin has the potential for biocontrol of multiple agriculturally important lepidopteran pests. Preliminary molecular docking of Vip3Aa44 and Vip3Aa69 proteins to Fibroblast growth factor receptor-like protein (<i>Sf</i>-FGFR) and Scavenger Receptor Class C like Protein (<i>Sf</i>-SR-C), the reported receptors in <i>S. frugiperda,</i> showed similar binding interactions for these toxins.