Investigating the role of arbuscular mycorrhizal fungi (AMF) in squash plant tolerance to water stress and resistance to aphid herbivory

Symbiosis with arbuscular mycorrhizal fungi (AMF) can provide host plants with several benefits including improved nutrient (primarily phosphorous) and water uptake, tolerance to abiotic stresses (i.e. scarcity of water), and increased defense against biotic stresses (i.e. insect herbivory). In natural environments, plants commonly experience both abiotic and biotic stresses simultaneously. In this study, we investigated how AMF-inoculation affects squash plant tolerance to water stress and resistance to aphid herbivory. We hypothesized that AMF would support plant growth and photosynthesis despite lower water availability. Moreover, we expected reduced aphid performance on AMF-inoculated plants that were either water-deprived or received sufficient water and that AMF inoculation would help plants compensate for aphid damage by helping the plants to regrow, even under water stress. To evaluate how AMF affects squash plant tolerance to water stress, we inoculated zucchini (Cucurbita pepo) plants with AMF and subjected them to either water stress or sufficient watering. We then measured plant growth traits of the AMF-inoculated and control plants under both watering conditions, including above- and below-ground biomass, plant height, root expansion, and photosynthesis. In a separate experiment to determine how AMF affects squash resistance to aphids with water stress or sufficient watering, we applied melon aphids (Aphis gossypii) to AMF-inoculated and control plants under both watering conditions. We then measured aphid performance (i.e., number of aphids) and resulting plant biomass. This study will provide insights on the potential of AMF use in sustainable agriculture to protect plants against abiotic and biotic stresses.