Metabolite Profiling of Annual Ryegrass Cultivars to Assess Disease Resistance and Susceptibility.

Direct immersion solid-phase microextraction coupled with gas chromatography-mass spectroscopy was used to create chemical fingerprints of annual ryegrass cultivars (Lolium rigidum). Extracts made of the inflorescences of four cultivars and one accession of annual ryegrass were assessed to identify differential metabolites between those resistant to and susceptible to bacterial galls associated with annual ryegrass toxicity (ARGT). Numerous compounds were identified. Principal component analysis showed distinct clustering of metabolites from disease-resistant and disease-susceptible cultivars. Partial least-squares-discriminant analysis identified sterols, esters, aldehydes, and terpenes that correlated with resistance to galls formation. Esters, sterols, phenols, heterocyclics, fatty acids, organofluorides, and siloxanes were predominant in resistant genotypes, whereas alcohols, aldehydes, terpenes, and hydrocarbons were predominant in susceptible genotypes. The identification of differentially expressed metabolites provides potential chemical markers to guide breeding strategies for ARGT resistance in ryegrass.