Fungal endophytes and their role as protective agents against herbivores

Endophytes are defined to be fungi or bacteria that live within asymptomatic plant tissue for all or part of their life cycle without causing detectable damage to its host. More specifically, fungal endophytes started being studied extensively in the last decade and since then different ecological roles have been attributed to them. Some of these include: being dormant saprobes and/or dormant pathogens, micorrhizal associates and protective agents against biotic and abiotic stresses. Our interest is to explore the protective agent functional role fungal endophytes play when in association with plants and investigate the effects these might have on insect herbivore performance. First off we were able to artificially inoculate cultivated cotton, Gossypium hirsutum with two different fungal endophytes in greenhouse conditions. Then these inoculated plants were exposed to Aphis gossypii a sucking-piercing insect in cultivated cotton where a significant reduction on the reproduction of the aphid was observed (P=0.002). Based on these results, we tested the same fungal endophytes used in the aphid study against a chewing lepidopteran insect Helicoverpa zea (cotton bollworm) also an important pest in cotton. Through a non-choice in planta feeding assay we evaluated both insect and plant performance in a fully factorial design. Insects fed on endophyte inoculated plants from 1^st instar to adult developmental stage. Plants colonized or uncolonized by the endophyte with or without insect exposure were evaluated for dry above and belowground biomass at the end of the experiment. Our results indicate a positive fungal endophyte-plant relationship against insect herbivores and we hope to elucidate the mechanism underlying these interactions because of its potential use in integrated pest management approaches.