Kandan Aravindaram, Vijayreddy Dumpapenchala, Ashwini Erappa, Shireesh Kumar Melur Prakash, Amala Udayakumar, Manjunatha Channappa, Sivakumar Gopalsamy, Arakalagud Nanjundaiah Shylesha, Kesavan Subaharan, Sushil Satya Nand
Cabbage experiences substantial yield reductions due to diamondback moth (Plutella xylostella) and cabbage aphid (Brevicoryne brassicae) infestation. Recurrent use of insecticides has led to insecticide resistance, necessitating the development of sustainable biocontrol strategies. This study involves the morpho-molecular characterization of Beauveria bassiana isolates from diverse locations. B. bassiana NBAIR-Bb5a exhibited the rapid mycelial growth (87.43 mm) with highest conidial germination rate (94.43%), and notable insecticidal enzymatic activities (chitinase, protease and lipase). Pathogenicity assays identified NBAIR-Bb5a as the most virulent, with LC₅₀ values of 4.60 × 104 conidia mL⁻1 and 8.61 × 104 conidia mL⁻1, and LT₅₀ values of 62.80 h and 70.05 h against B. brassicae and P. xylostella, respectively. Field trials in Unnati hybrid cabbage demonstrated that NBAIR-Bb5a reduced aphid and DBM populations by 100.00 per cent, resulting in a yield of 41.28 t ha⁻1. Metabolite profiling identified bioactive compounds with antimicrobial, insecticidal, and plant growth-promoting properties. Molecular modelling was carried out further to elucidate the interaction of these metabolites. Protein targets of P. xylostella, Glutamate-gated chloride channel and GABA receptor, and Myrosinase 1 and 2 of B. brassicae, were modeled using Swiss-Model and validated with Ramachandran plots. Docking studies showed that Penitrem D and Beauvericin exhibited the strongest binding affinities (≤ - 8.0 kcal mol⁻1), bypassing emamectin benzoate. These metabolites likely interfere the neuronal signalling and detoxification pathways, indicating a multi-target insecticidal activity. The combined findings of biochemical and molecular suggests that B. bassiana NBAIR-Bb5a as a highly effective and eco-friendly biocontrol agent for the integrated pest management in cabbage under the evaluated experimental conditions.