Construction and Phenotypic Characterization of a Recombination Inbred Line (RIL) Population from a Melo-agrestis Melon Hybrid

Melon (Cucumis melo L.) is an economically important horticultural crop worldwide, while its production is continuously endangered by powdery mildew (PM), a fungal disease mainly caused by Podosphaera xanthii, due to the insufficiency of disease resistant germplasms. Here, a melon recombinant inbred line (RIL) population that consisted of 188 independent individuals was obtained through the crossing of ‘SN-1’ (C. melon L. ssp. melo) and ‘YJM’ (C. melon L. ssp. agrestis), two parents with contrasting PM resistance, followed by 7-round selfings. Comprehensive phenotypic investigation revealed substantial variations in key agronomic traits among these RILs, such as stem diameters of 3.7~12.6 mm and internode lengths of 1.6~12.2 cm at the anthesis stage, as well as peduncle lengths of 0.5~9.5 cm and soluble solid content of 1.6~17.4% at the maturation stage. Particularly, 95 RILs, of which 60 and 35 belonged to thin-peel and netted types, respectively, were identified to be highly resistant to P. xnathii infection, providing new germplasms for melon improvement. Altogether, the generation of this melo-agrestis RIL population, together with the phenotypic observations, lays a solid foundation for mechanistic investigation of the traits with economic importance and could contribute to future breeding programs of melon cultivars with PM resistance.