Dual resistance of melon to Fusarium oxysporum races 0 and 2 and to papaya ring-spot virus is controlled by a pair of head-to-head-oriented NB-LRR genes of unusual architecture
Résumé
Potyviruses such as Papaya ring-spot virus (PRSV) cause important yield losses in cucurbits. Two distinct resistant alleles were identified in the Cucumis melo germplasm. Accession PI 414723 ( Supplemental Table 1) possesses mono-genic resistance, controlled by the Prv2 allele, and reacts to PRSV by systemic necrotic lesions; plants with the Prv1 allele, described in cultivar WMR-29, remain symptomless (Pitratand Lecoq, 1983). Fusarium oxysporum f. sp. melonis (FUS) exclusively attacks melon, causing severe wilt. Monogenic dominant resistance was described against races 0, 1, and 2. The Fom-2 gene, controlling resistance to races 0 and 1, was cloned by Joobeur et al. (2004), and encodes a nucleotide binding domain (NB)–leucine rich repeat (LRR) protein. Our study focused on the Fom-1 gene, which confers resistance to races 0 and 2 (Risser et al., 1976), and on the Prv gene; the two are tightly linked on melon linkage group IX. Molecular markers were developed for the Fom-1/Prv locus, but no study has provided the resolution required for positional cloning.