To identify orthologous gene groups among C. pepo, C. melo, C. sativus, C. lanatus and A. thaliana we used OrthoMCL software with default settings. The association between reference R-genes (http://prgdb.crg.eu/) and relative orthologous group (OG) was detected using Best BLAST Hit method (BlastP, E < 1 e−5) and the output was filtered for a query coverage and identity percentage, both >50%.