Resistance gene homologues in melon are linked to genetic loci conferring disease and pest resistance

Abstract

Genomic and cDNA fragments with homology to known disease resistance genes (RGH fragments) were cloned from Cucumis melo using degenerate-primer PCR. Fifteen homologues of the NBS-LRR gene family have been isolated. The NBS-LRR homologues show high divergence and, based on the partial NBS-fragment sequences, appear to include members of the two major subfamilies that have been described in dicot plants, one that possesses a TIR-protein element and one that lacks such a domain. Genomic organization of these sequences was explored by DNA gel-blot analysis, and conservation among other Cucurbitaceae was assessed. Two mapping populations that segregate for several disease and pest resistance loci were used to map the RGH probes onto the melon genetic map. Several NBS-LRR related sequences mapped to the vicinity of genetic loci that control resistance to papaya ringspot virus, Fusarium oxysporum race 1, F. oxysporum race 2 and to the insect pest Aphis gossypii. The utility of such markers for breeding resistant melon cultivars and for cloning the respective R-genes is discussed.

Five independent loci each control monogenic resistance to gummy stem blight in melon (Cucumis melo L.)

“…Although not yet isolated at the molecular level, both Fom-1 and Fom-2 are tightly linked to sequences bearing NBS-LRR motifs (Brotman et al 2002;Wang et al 2002).…”

Genetic Mapping and Molecular Breeding in Cucurbits

“…Périn et al (1998) mapped this gene at 8 cM from marker T_820. Brotman et al (2002) found a RFLP marker, NBS47-3, linked at 2.6 cM to Fom-1, while another marker K_1180 flanked on the other side at 7 cM (Table 5.2). Aphids (Aphis gossypii) are another serious problem for melon because they seriously damage plants by transmitting viruses.…”

“…Chemical control is ineffective because insecticide resistance is widespread. A gene (Vat) conferring resistance to this aphid has been mapped by PerlTreves' group (Klingler et al 2001;Brotman et al 2002). Vat was flanked with RFLP markers NBS-2 and AC-39 at 3.1 and 6.4 cM, respectively, using 64 F 3 families (Klingler et al 2001).…”

“…Vat was flanked with RFLP markers NBS-2 and AC-39 at 3.1 and 6.4 cM, respectively, using 64 F 3 families (Klingler et al 2001). Brotman et al (2002) identified closer flanking markers (EAB8 and EAF23) within 4 cM of the gene (Table 5.2).…”

“…These markers should be sufficient for cloning nsv by map-based cloning in addition to serving as molecular tools for genotypic selection. For other viral disease resistance genes in melon, Brotman et al (2002) identified a disease resistance gene homolog, NBS47-3, that was linked at 1.2 cM to Prv, a potyvirus PRV resistance gene. Danin-Poleg et al (2002) identified a SSR marker (CMAG36) cosegregating with Zym-1, which confers resistance to zucchini yellow mosaic virus (ZYMV) in melon.…”