Molecular Plant Breeding 2024, Vol.15, No.3, 112-131 http://genbreedpublisher.com/index.php/mpb 123 2) The Vat gene cluster in melon, which confers resistance to pests and pathogens, has been characterized, revealing a high potential for resistance based on SNP variations and leucine-rich-repeat domains (Chovelon et al., 2021). 3) A major quantitative trait locus (QTL) on chromosome 8 of Cucurbita moschata has been linked to resistance against Tomato leaf curl New Delhi virus, with molecular markers identified for breeding programs (Sáez et al., 2020). 4) Inheritance analysis and SNP marker identification have been conducted for Zucchini yellow mosaic virus resistance in Cucurbita pepo, with specific NBS-LRR protein-encoding genes located near resistance-associated SNPs (Capuozzo et al., 2017). 5) QTL mapping has identified candidate genes for powdery mildew resistance in cucumber, with a particular focus on a gene encoding a leucine-rich repeat receptor-like kinase (Zhang et al., 2020). 6) Transcriptome profiling of pumpkin leaves infected with powdery mildew has revealed a complex regulatory network involving hormone signal transduction and defense responses, with several genes significantly upor down-regulated in resistant plants (Guo et al., 2018). 7) A QTL on chromosome 6 of cucumber has been associated with resistance to Cucumber mosaic virus, and a candidate gene with differential expression upon infection has been identified (Shi et al., 2018). 8) The MLO gene family, which plays a role in powdery mildew resistance, has been identified and characterized in pumpkin, with certain genes up-regulated in response to infection (Win et al., 2018). 9) New NBS-LRR gene analogues have been discovered in native cucurbit species in Iran, suggesting a recent common ancestor and potential resistance against bacterial blight and tomato mosaic virus (Gharaei et al., 2017). 10) Genomic tools are being utilized to enhance disease resistance breeding in zucchini, with a focus on identifying R-gene candidates and understanding the genetic basis of resistance mechanisms (Andolfo et al., 2021). Research across various cucurbit species has uncovered a wealth of genetic resources for disease resistance, particularly against powdery mildew and viral pathogens. The identification of resistance genes, QTLs, and gene clusters, along with the development of molecular markers, has facilitated the breeding of resistant cultivars. These advances contribute to sustainable agriculture by reducing the need for chemical pesticides and enhancing crop resilience to disease. 6.2.2 Fruit quality improvement Genomic research has revolutionized the field of plant breeding, enabling the development of fruit varieties with enhanced qualities. By identifying genes linked to desirable traits, breeders can create fruits with improved flavor, color, and nutritional value. In melon breeding, genomic tools have facilitated the selection of varieties with increased sweetness and longer shelf life. 1) Genomic selection (GS) is a promising approach for improving quantitative traits in crops, outperforming traditional marker-assisted selection by using high-density marker scores to predict breeding values, which accelerates the breeding cycle and captures more variation due to small-effect quantitative trait loci (QTL) (Varshney et al., 2017). 2) In table grapes, genomic selection has proven more efficient than QTL analysis for inferring the genetic contribution of marker loci to agronomic traits, suggesting its utility in speeding up selection procedures (Viana et al., 2016). 3) Combining genome-wide association studies (GWAS) and genomic selection (GS) increases the power and
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