Colonization of Serendipita indica promotes resistance against Spodoptera exigua in onion ( Allium cepa L.).

Plant-endophyte symbiosis influences plant defense and growth. is a root endophyte that promotes growth and induces tolerance against biotic and abiotic stress in plants. In this study, we examined the effect of colonization on herbivore () resistance of onion ( L.). We found that colonization of in the roots of onion significantly reduced the feeding damage of leaves by larvae, and also resulted in a reduction in weight gain of the larvae when fed on plants. This enhanced resistance is a result of modulation of antioxidant and defense enzymes/genes in the host by mutualism. Specifically, the activities of enzymes such as Superoxide dismutase, peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, and HO content were significantly higher in the early stages of feeding in the colonized plants compared to the non-colonized counterparts. Similarly, defense genes also showed modulation in response to this tripartite interaction of onion - mutualism and herbivory. The hierarchical cluster analysis and principal component analysis indicated a clear difference in the onion biochemical responses, which is due to the symbiosis. Our investigation demonstrates that onion- symbiosis significantly decreases chewing injury by efficiently modulating antioxidant and defense enzyme activities and gene expression in response to herbivory. Therefore, can be used as a potential biocontrol agent for sustainable management of this important pest of Alliums.