The Role Of Endohyphal Symbionts In Influencing Fungal Degradation Of Plant Cell Walls Under Field Conditions

Abstract

Many plant-associated fungi form symbiotic relationships with endohyphal bacteria (EHB), which live within fungal tissue. Our goal was to evaluate how EHB (here, Pantoea spp.) influence the ability of fungi to degrade plant material under field conditions, thus extending previous research based only on in vitro assays. We examined the degradation ability of two fungi (9133 and 9140) with (+) or without (-) EHB on foliage of three plant species (Platycladus orientalis, Cupressus arizonica, Juniperus deppeana). Plant material with one treatment (9133+, 9133-, 9140+, 9140-, or control) was placed into mesh litter bags and deployed into field plots. After three months we found that treatment with fungi, regardless of EHB status, increased mass loss relative to controls for two species (C. arizonica, J. deppeana). In contrast to expectations based on in vitro results and a small pilot study, EHB did not increase degradation of plant material by fungi. We anticipate that biotic interactions with other decomposers in soil, especially in a relatively rainy winter with robust microbial activity, could explain the observed results. Future experiments might focus on how EHB influence interactions among the diverse fungi that play a role in plant tissue degradation in complex natural systems.