Effect of arbuscular mycorrhizal colonization on tomato defense metabolites and population parameters of Tuta absoluta (Meyrick)

The tomato leaf miner (TLM), Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is one of the most important and destructive pests of tomatoes and is threatening worldwide tomato production. While control of this pest insect is primarily based on conventional synthetic pesticides, there is a growing concern to use more ecologically sound pest management strategies, e.g., the use of soil microorganisms. In this project, we therefore investigated the effect of a mixture of four species of arbuscular mycorrhizal fungi (AMF) (Funneliformis mosseae, Rhizophagus intraradices, R. irregularis, and Glomus iranicus) when inoculated with tomato plants in relation to the induction of defense in the plant leaves, and also the potential to resist against TLM. For all three plant enzymes investigated, peroxidase, phenylalanine ammonia lyase, and polyphenol oxidase, the inoculation with AMF had induced an increase, and also the total phenol contents in AMF-plants were higher. When AMF-plants were infected with TLM, this caused higher increases. In parallel, the life table parameters of TMF feeding on AMF-plants demonstrated that the insects were retarded in development and reproduction potential, e.g., a lower intrinsic rate of increase (r_m), net reproduction rate (R₀), and fecundity and a shorter oviposition period. These findings do not only provide insights in the synergy between AMF and tomato plants, but are also useful for developing more ecologically sound pest management strategies against this important pest insect of TLM and potentially also other pest in the future.