Fine mapping of wmv1551, a resistance gene to Watermelon mosaic virus in melon

Recessive resistance to Watermelon mosaic virus (WMV) in melon has previously been reported in the African accession TGR-1551. Using a population of recombinant inbred lines (RIL), derived from a cross between TGR-1551 and the susceptible Spanish cultivar Bola de Oro' (BO), a major quantitative trait locus (QTL) controlling the resistance was previously mapped to a region of approximately 760kb in chromosome 11. Minor QTLs were also reported with lower effects, dependent on the environmental conditions. A genotyping by sequencing (GBS) analysis of the RIL population has provided new information that allowed the better location of the major QTL in chromosome 11. Moreover, three minor QTLs in chromosomes 4, 5, and 6 were identified. Generations derived from the RIL population were subsequently phenotyped for resistance and genotyped with SNP markers to fine map the resistance derived from TGR-1551. The results obtained have allowed to narrow the position of the resistance gene on chromosome 11, designated as wmv(1551), to a 141-kb region, and the confirmation of a minor QTL in chromosome 5. The effect of the minor QTL in chromosome 5 was significant in heterozygote plants for the introgression in chromosome 11. The SNP markers linked to both QTLs will be useful in breeding programs aimed at the introgression of WMV resistance derived from TGR-1551. Future work will be directed to identifying the resistance gene, wmv(1551), in the candidate region on chromosome 11.