Epsilon Archive for Student Projects

Abstract

Plant-plant interactions can significantly influence growth, development, and disease resistance, yet their role in shaping immune responses remains insufficiently understood. This thesis investigated whether neighboring oat genotypes and co-occurring Fusarium pathogens can alter disease development in oat. A genetically characterized oat panel from the Nordic Oat Taskforce was grown under controlled phytotron conditions in monoculture and mixed-genotype configurations and challenged with Fusarium graminearum and Fusarium culmorum, either singly or in combination. Detached-leaf and pot-based assays were evaluated through visual scoring and image-based phenotyping. In the diversity oat panel, physical separation of the two pathogens on the same leaf reduced mean disease severity, indicating disruption of a cooperative disease interaction. The strongest reduction was observed for F. graminearum. This effect was weak or absent in modern cultivars. In mixed-genotype assays, donor genotype identity shifted receiver plants away from the intermediate control phenotype. Among 117 donor genotypes, 43 shifted receivers toward resistance and 36 shifted receivers toward susceptibility. Donors with measurable biomass were more often associated with resistance shifts, but total biomass alone did not explain the pattern. Instead, donor tillering and growth architecture appeared more informative. Overall, this study provides proof-of-concept evidence for social immunity in oat and identifies both pathogen interaction and neighbor genotype identity as important factors influencing Fusarium disease outcomes in crop mixtures.