Response to plant defense elicitation is genotype and context dependent in diverse oat (Avena sativa L.) germplasm

Pests and pathogens contribute to substantial crop yield losses, and these losses are predicted to be exacerbated by varying and new pest pressures associated with climate change. As such, characterizing variation in immune responses is critical for developing new plant breeding approaches for multiple biotic stress resilience. We thus tested the extent to which plants vary in responsiveness to defense elicitation and associated growth-defense trade-offs, and how these responses depended on field and pathogen conditions. Using a panel of >250 spring oat (Avena sativa L.) genotypes, we evaluated phenotypic and genetic variation in defense elicitation by measuring avenanthramides, specialized defensive metabolites, and disease resistance, as well as yield and growth traits. We found that defense elicitation increased the concentration of defensive avenanthramides across trials, and reduced the severity of crown rust and Fusarium head blight. There was substantial genetic variation in responses, and also genotype-by-elicitation state interactions in field trials. While plant growth was reduced in some trials, there were no loci identified by genome-wide association mapping for either growth or defense regulation. These results demonstrate that targeting variation in regulation of defense can contribute to breeding for resilient crops, and that breeders could develop genotypes with reduced growth-defense trade-offs.