Mapping quantitative trait loci and developing first molecular marker for race 5 of Podosphera xanthii resistance in melon (Cucumis melo L.)

Powdery mildew of melon caused by the Podosphaera xanthii factor is a disease that causes serious yield losses economically in all areas where melon is grown from Asia to Europe and America. The use of resistant varieties for the control of the disease is the most environmentally friendly method. However, traditional methods of melon breeding have made a noteworthy input to resistance varieties improvement, but they have been slow and incompetent in targeting complex powdery mildew disease resistance traits. To overcome these problems and to facilitate breeding programs, molecular markers closely linked to the Pm-RS gene are needed for marker-assisted selection (MAS). The present study aimed to map quantitative trait locus for powdery mildew resistance and identify the molecular markers linked with the Pm-R gene which provides resistance to race 5 of P xanthii for MAS breeding in melons. A total of 310 primers/combinations belonging to six marker systems including SRAP, SSR, ISSR, TRAP, CAPS, SCAR in the RIL population consisting of 136 genotypes, developed from crosses PMR-6 and susceptible inbred line were used for QTL mapping. Quantitative trait loci analysis determined one major QTL (Pm-R) on linkage group I for resistance to races 5 of powdery mildew. The SSR12202 marker is linked to the Pm-R gene QTL at 2.12 cM genetic distance, and the CMCT170b and CMMS30-3 markers are determined in the support interval of this QTL. The co-dominant markers, together with the map information reported here could be used for genotyping selection of resistance to race 5 of P. xanthii in melon breeding.