Arbuscular mycorrhizal fungus improves common vetch resistance to powdery mildew and influences subsequent insect feeding preferences

Arbuscular mycorrhizal fungi (AMF) represent a critical symbiotic relationship that enhance plant resistance to plant diseases and insect attacks. However, the effects of AMF on aphids and their natural predator, the ladybug ( Harmonia axyridis ), particularly regarding feeding preference under pathogenic fungi invasion remain largely unexplored. To investigate whether AMF influence the feeding preferences of aphids and ladybugs, we conducted a pot experiment using common vetch ( Vicia sativa ) that was naturally infected with powdery mildew ( Erysiphe pisi ). The common vetch was inoculated with or without AMF, alongside pea aphids ( Acyrthosiphon pisum ) and the simulated aphid feeding conducted through needling. The results demonstrated that AMF colonization increased the root dry weight of common vetch and enhanced the activity of plant defense enzyme including superoxide dismutase, peroxidase, and polyphenol oxidase, while also reducing the severity of powdery mildew. Additionally, AMF decreased the total phenolic (TP) content in treated plants, it increased TP and salicylic acid levels in needling treatments. Mycorrhizal plant significantly attracted pea aphids compared to non-mycorrhizal plants. Furthermore, when subjected to aphid stress or simulated insect feeding, mycorrhizal plants also significantly attracted ladybugs. These findings indicate that AMF play an important role in regulating complex interactions among pathogens, pests, and their natural enemies. This interplay has important implications for developing sustainable pest management strategies in agricultural ecosystems. • AMF increased vetch growth, defenses, and reduced powdery mildew severity. • Mycorrhizal plants attracted pea aphids and their ladybug predators. • AMF altered plant chemical profiles, influencing pest-pathogen interactions. • AMF drive ecosystem-level pest control through modulation of multitrophic interactions.