Bacteria-mediated regulation of Aphidius gifuensis parasitism efficacy in Myzus persicae: Implications for biological control strategies

Aphidius gifuensis , a key parasitoid of Myzus persica e in tobacco agroecosystems, has been extensively implemented in Chinese biological control programs for over a decade. This sustained augmentation strategy has not only established stable field populations of A. gifuensis but also significantly suppressed aphid densities and associated viral disease transmission. However, long-term laboratory maintenance of both aphid hosts and parasitoid colonies has resulted in diminished biological fitness of A. gifuensis , manifesting as reduced parasitic efficacy and elevated control costs. To address these challenges in mass rearing and field application, our investigation focused on: (1) Identification of endosymbiotic bacteria within M. persicae and A. gifuensis , and (2) Evaluation of bacterial influences on aphid reproductive biology. Key findings include:1. Microbial characterization: Seven bacterial endosymbionts spanning five genera were isolated. Lysinibacillus fusiformis was uniquely associated with aphids, while Bacillus cereus and Stenotrophomonas maltophilia were specific to parasitoids. Four additional parasitoid-associated species were identified: Bacillus pumilus , Bacillus subtilis , Acinetobacter radioresistens , and Exiguobacterium sibiricum .2. Reproductive modulation: All isolates demonstrated significant effects ( p  < 0.01) on aphid fecundity. S. maltophilia exhibited the strongest oviposition stimulation (88.38% increase vs. control), contrasting with A. radioresistens showing maximal suppression (47.13% reduction).3. Physiological impacts: A. radioresistens significantly upregulated aphid phenoloxidase (1.64% increase) and superoxide dismutase (SOD) activity (2.99% elevation). Notably, this bacterial strain induced differential regulation of stress-response proteins compared to controls.