Mapping Resistance to Alternaria cucumerina in Muskmelon

During the last three decades, numerous muskmelon (cantaloupe) lines have been identified with resistance to the Alternaria leaf blight (ALB) pathogen Alternaria cucumerina, but the genetic basis of this resistance has not been determined. A saturated melon genetic map was constructed with markers developed through genotyping-by sequencing of a recombinant inbred line (RIL) population (F₆-F₁₀; N=82) derived from single seed descent of a F₂ population from a cross between the ALB resistant parent MR-1 and the ALB susceptible parent Ananas Yokneum. The population was evaluated for A. cucumerina resistance using a wounded-leaf inoculation strategy. A saturated genetic map consisting of over 2200 SNP markers and a size of 1,400 cM was generated from this study. Multiple quantitative trait loci (QTL) mapping procedure identified two QTL that explained 33.9% of the resistant phenotype. Several candidate genes within these QTL were identified using the C. melo v3.5 genome.