Summary Development of resistant crops is the most effective way to control plant diseases to safeguard food and feed production. Disease resistance is commonly based on resistance genes, which generally mediate the recognition of small proteins secreted by invading pathogens. These proteins secreted by pathogens are called ?avirulence? proteins. Their identification is important for being able to assess the usefulness and durability of resistance genes in agricultural settings. We have used genome sequencing of a set of strains of the melon wilt fungus Fusarium oxysporum f. sp. melonis (Fom), bioinformatics-based genome comparison and genetic transformation of the fungus to identify AVRFOM2, the gene that encodes the avirulence protein recognized by the melon Fom-2 gene. Both an unbiased and a candidate gene approach identified a single candidate for the AVRFOM2 gene. Genetic complementation of AVRFOM2 in three different race 2 isolates resulted in resistance of Fom-2-harbouring melon cultivars. AvrFom2 is a small, secreted protein with two cysteine residues and weak similarity to secreted proteins of other fungi. The identification of AVRFOM2 will not only be helpful to select melon cultivars to avoid melon Fusarium wilt, but also to monitor how quickly a Fom population can adapt to deployment of Fom-2-containing cultivars in the field.
Bibliographical noteWe thank ENZA Zaden for the kind gift of melon Cha‐T and Cha‐Fom2 seeds, Thomas R. Gordon for the kind gift of the Fom VCG tester strains, Michel Pitrat for the kind gift of the Fom012, Fom013 and Fom016 strains, Rafi Perl‐Treves for the kind gift of the Fom009, Fom010 and Fom011 strains and Jose Alvarez Alvarez for the kind gift of Fom004, Fom005 and Fom006. We are grateful to Floris Stevens and Ian Ching for excellent technical help. This work was supported by the Innovational Research Incentives Scheme Vici of The Netherlands Organisation for Scientific Research (NWO) and the Horizon programme of the Netherlands Genomics Initiative through grants to M.R.
- virulence gene
- comparative genomics
- Fusarium oxysporum f. sp. Melonis
- gene-for-gene interaction
- melon Fom-2 resistance gene