Assessment of Rhodococcus sp. (MG1) induced biochemical alterations and genotoxicity in Spodoptera litura

Abstract

Spodoptera litura (Lepidoptera: Noctuidae) is recognised as a major agricultural pest causing economic losses to a number of agricultural and vegetable crops. Chemical insecticides remain the primary control method. However, excessive and repeated applications have led to the evolution of resistance, environmental contamination and risk to nontarget organisms. To address these issues, sustainable and eco-friendly alternatives like microbial control have become key strategies in integrated pest management. The present study evaluates the effects of entomopathogenic bacterium, Rhodococcus sp. (MG1) on digestive, detoxifying, and antioxidant enzymes along with histological and genotoxic effects on S. litura larvae. Our results revealed a significant drop in the activity levels of major digestive enzymes—including α-amylase, glucosidases, galactosidases, lipases, and proteases due to MG1 infection. Feeding larvae with castor leaves treated with LC₅₀ MG1 cell suspension significantly increased the level of detoxifying enzymes. Maximum induction of acid phosphatases (1.95-fold) and glutathione S-transferases (2.47-fold) were observed in larvae after 48 h and 96 h, respectively over control. Catalase (CAT) and Superoxide dismutase (SOD) activities were also significantly elevated in treated larvae. Significant effect of bacterial infection was also recorded on immune response of larvae with an increase in the activity of lysozyme and phenoloxidase. However, total hemocyte count was found to be reduced following infection. Additionally, Rhodococcus sp. infection induced genotoxicity as manifested by increased values of all the comet parameters viz. tail length (TL), tail intensity (TI), tail moment (TM) and olive tail moment (OTM) compared to control.