Recently, high throughput KASP markers for resistance to GSB have been reported in watermelon. Among these assays, HRM and Kompetitive allele specific PCR (KASP) assays have relatively simple, fast, and cost-effective approaches. GBS and ddRAD-seq techniques have been used for mapping genes and development of markers in several plant species such as rapeseed, soybean, maize, strawberry and melon. CAPS/HRM markers have been reported for ‘PMR 5’ resistance to powdery mildew race 5 in melon. This facilitated the development of high throughput molecular markers such as Cleaved amplified polymorphic sequence (CAPS) markers, high-resolution melting (HRM) and PCR amplicon using InDel based markers in Cucurbitaceae. The release of draft genomes of watermelon and genotyping by sequencing (GBS) has made it possible to discover genome-wide sequence variations including single nucleotide polymorphism (SNP) and Insertion/Deletion (InDel) especially in the causal genes within the QTL regions. Besides, QTLs for GSB resistance have also been identified in other cucurbits, such as Cucumber and melon. ![]() Several studies have mapped the QTLs underlying GSB resistance in watermelon, including one QTL on chromosome 8 of PI 189225 explaining 32% of the phenotypic variations three QTLs on chromosomes 3, 5 and 7, explaining between 6.4 and 21.1% of the phenotypic variations and another three QTLs on chromosomes 8 and 6. Genetic studies of these resistant genotypes indicated various patterns of genetic control of resistance to GSB, including monogenic control in PI 189225 and polygenic control with minor effects from individual genes in PI 189225, PI 482283, and PI 526233. Several sources of genetic resistance to GSB have been identified, mostly in the wild relative, Citrullus amarus and later, in both C. Therefore, development of resistant cultivars is the most eco-friendly, cost-effective and sustainable method of watermelon production. Although chemical control methods had been moderately effective in controlling GSB, the repeated use of chemicals has a negative impact on the environment, and may become ineffective due to the rise of resistance to chemicals in certain pathogenic isolates. ![]() GSB symptoms include circular dark tan lesions that blight the leaf, stem cankers, and gummy brown ooze exuding from cankers. Stagonosporopsis cucurbitacearum), is the most devastating disease of watermelon. Watermelon production is frequently hampered by various insects and diseases, of which gummy stem blight (GSB), caused by the soil, airborne, and seed-borne fungal pathogen Didymella bryoniae (syn. Watermelon fruit is rich in water (91%), and important nutritional compounds such as sugars, lycopene, β-carotene and citrulline, which are very beneficial to human health. Watermelon ( Citrullus lanatus) is one of the most popular fruits in the Cucurbitaceae family, and is grown throughout tropical to temperate regions of the world where the climate is favorable (FAOstat 2021). These findings will help breeders to develop watermelon cultivars resistant to GSB. ![]() Five potential candidate genes were predicted to be associated with GSB resistance. Two high resolution melting (HRM) markers, WmGSB1.1–2 and WmGSB1.1–7 having a high positive correlation with the phenotypic variations, were developed. ![]() Among these, the QTL ClGSB1.1 on chromosome 1 is identified as a major QTL harboring five candidate genes associated with GSB resistance including two RLKs ( ClC01G014900 and ClC01G015010), two WRKY transcription factors ( ClC01G014910 and ClC01G014990), and one AvrRpt-cleavage domain protein ( ClC01G015130). Three QTLs namely, ClGSB1.1, ClGSB10.1, and ClGSB11.1 associated with GSB resistance, explaining approximately 10% of the phenotypic variation, were identified. Inheritance analysis indicated that resistance to GSB is a multi-genic trait in this population. We identified the genome-wide single nucleotide polymorphisms (SNPs) by genotyping by sequencing (GBS) of an F 2 population developed from C. In this study, we aimed at identifying quantitative trait loci (QTLs) linked to GSB resistance in melon. Identification of genetic determinants and sources of resistance to this devastating GSB disease in watermelon is essential for developing resistant varieties. Stagonosporopsis cucurbitacearum), produces devastating symptoms on whole plants of watermelon ( Citrullus lanatus) and other cucurbits, significantly reducing yield and quality. Gummy stem blight (GSB), caused by Didymella bryoniae (syn.
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