Diversity in receptor-like kinase genes is a major determinant of quantitative resistance to Fusarium oxysporum f.sp matthioli

Resistance to wilt fungus Fusarium oxysporum f.sp. matthioli (FOM) is a polygenic trait in Arabidopsis thaliana. RFO3 is one of six quantitative trait loci accounting for the complete resistance of accession Columbia-0 (Col-0) and susceptibility of accession Taynuilt-0 (Ty-0). We find that Col-0 and Ty-0 alleles of RFO3 are representative of two common variants in wild Arabidopsis accessions, that resistance and susceptibility to FOM are ancestral features of the two variants and that resistance from RFO3 is unrivalled by other genes in a genome-wide survey of diversity in accessions. A single receptor-like kinase (RLK) gene in Col-0 is responsible for the resistance of RFO3, although the susceptible Ty-0 allele codes for two RLK homologs. Expression of RFO3 is highest in vascular tissue, which F. oxysporum infects, and root-expressed RFO3 restricts FOM infection of the vascular system. RFO3 confers specific resistance to FOM and provides no resistance to two other crucifer-infecting F. oxysporum pathogens. RFO3's identity, expression and specificity suggest that RFO3 represents diversity in pattern-recognition receptor (PRR) genes. The characteristics of RFO3 and the previously published RFO1 suggest that diversity in RLK PRRs is a major determinant of quantitative resistance in wild plant populations.