Development of a muskmelon cultivar with improved resistance to gummy stem blight and desired agronomic traits using gene pyramiding

Abstract

Gummy stem blight (GSB), caused by Didymella bryoniae(Auersw.) Rehm., is a severe disease affecting Cucurbitaceae crops including melons. The resistance of current melon varieties that carry a single Gsb resistance gene is insufficient to protect against the abundant variation of the D. bryoniae isolates.Pyramiding multiple Gsb resistance genes into melon cultivars is an effective way to develop a broad resistance spectrum and to increase the duration of GSB resistance. In this study, two resistance genes (Gsb-4 and Gsb-6) from two resistant accessions, PI482398 and PI420145, were pyramided into one variety using marker-assisted selection (MAS). The donor parent 4598 that contained Gsb-4 and Gsb-6was hybridized with muskmelon Baipicui to produce BC₁F₁ and BC₂F₁. Phenotyping and MAS enabled identification and pyramiding of two Gsb genes in individuals of F_1, BC₁F₁ and BC₂F₁. Field cultivation showed that individuals carrying both Gsb-4 and Gsb-6 had improved resistance to GSB and improved fruit quality. The results indicated that MAS-based pyramiding is an effective strategy for breeding melon cultivars with increased resistance to GSB.