Abstract Background Arbuscular mycorrhizal fungi (AMF) have attracted considerable attention for their roles in enhancing plant stress resistance and elucidating the underlying mechanisms. However, the effects and mechanisms of AMF in regulating plant resistance to insect herbivores remain insufficiently understood. Here, we investigated how AMF modulates tomato resistance to Spodoptera litura using a factorial experimental design integrating AMF inoculation and insect herbivory, and further examined the associated physiological and molecular responses to explore the underlying mechanisms. Results AMF significantly increased the expression of phosphorus transporter genes SlPT4 and SlPT5 , enhanced phosphorus content, and promoted tomato growth. AMF inoculation also suppressed larval growth of S. litura , reduced leaf damage, increased antioxidant enzyme activities, and decreased malondialdehyde (MDA) accumulation. At 24 h after herbivory, AMF enhanced the expression of JA biosynthesis-related genes ( SlAOC , S lOPR3 , and SlLOXD ), increased jasmonic acid (JA) and JA-Ile levels, and reduced abscisic acid (ABA) content. At 48 h, AMF increased indole-3-acetic acid (IAA) levels and further upregulated insect resistance-related genes, including SlPI1 , SlPI2 , and S lTD . Conclusions These findings suggest that AMF suppresses S. litura feeding and enhances tomato resistance, with temporal changes in hormonal signaling and defense responses.
Liu et al. (Mon,) studied this question.