Endophyte-mediated resistance against white pine blister rust in Pinus monticola

Induced resistance responses, including fungal endophyte-mediated resistance, have been well studied in both agricultural crops and grass systems. Yet, the effect of these processes and symbionts in forest trees is poorly known. Fungal endophytes have been found in all conifer forest systems examined to date and have been hypothesised to be involved in resistance-mediated responses. However, in the absence of functional studies the influence of these endophytes on the extended phenotype of the host plant is unclear. In this study we demonstrate that fungal endophytes from Pinus monticola were effective at increasing survival in host plants against the exotic pathogen Cronartium ribicola, which is responsible for the devastating disease called white pine blister rust. Seedlings previously inoculated with fungal endophytes lived longer than endophyte-free seedlings and also showed some reduction in white pine blister rust disease severity. This endophyte-mediated resistance was found to be effective over time, indicating persistence, and is hypothesised to be a form of induced resistance. Overall, this suggests fungal endophytes may play a determinative role in the structure of biological communities and could provide a useful alternative or ancillary management tool for combating pests and diseases.