Molecular Pathogens 2024, Vol.15, No.3, 155-169 http://microbescipublisher.com/index.php/mp 161 This study by Shnaider et al. (2022) exemplifies the power of genomic tools in advancing our understanding of disease resistance in crops. By mapping specific genomic regions linked to resistance against PM in melons, researchers provide valuable insights that could lead to the development of more robust melon varieties. The integration of new genomic data with previous findings allows for a more comprehensive understanding of the genetic basis of resistance traits. Such knowledge is crucial for breeding programs aiming to combine various resistance sources to develop cultivars with enhanced durability against PM. The identification of candidate genes within these regions further directs functional studies which are essential for confirming their role in resistance mechanisms and for future applications in precision breeding. 5.2 Recent discoveries in gene localization Recent discoveries have pinpointed several genes and chromosomal regions associated with PM resistance in Cucurbitaceae. In cucumber, the CsGy5G015660 gene, encoding a putative leucine-rich repeat receptor-like serine/threonine-protein kinase, has been identified as a strong candidate for PM resistance (Zhang et al., 2020). In zucchini, the CpPM10.1 locus on chromosome 10 has been associated with resistance, with three genes containing the RPW8 domain being identified as potential contributors to resistance (Wang et al., 2021). Similarly, in melon, resistance to PM has been linked to a 250 and 381 kb region on chromosomes 5 and 12, respectively (López-Martín et al., 2022). 5.3 Chromosomal regions associated with resistance Chromosomal regions associated with PM resistance have been identified across various Cucurbitaceae species. In cucumber, a major resistance gene, pm-s, has been mapped to chromosome 5, with the closest flanking markers being SSR20486 and SSR06184/SSR13237 (Liu et al., 2017). In zucchini, the major dominant locus CpPM10.1 conferring resistance to PM has been located in a 382.9 kb region on chromosome10 (Wang et al., 2021). In melon, the resistance to PM races 1, 2, and 5 has been associated with regions on chromosomes 5 and 12 (Figure 4) (López-Martín et al., 2022). Furthermore, a single major QTL conferring resistance to PM in pumpkin (Cucurbita moschata) has been located in a 6.9~7.3 Mb region on chromosome 3 (Park et al., 2020). This study by López-Martín et al. (2022) exemplifies the power of genomic tools in advancing our understanding of disease resistance in crops. By mapping specific genomic regions linked to resistance against PM in melons, researchers provide valuable insights that could lead to the development of more robust melon varieties. The integration of new genomic data with previous findings allows for a more comprehensive understanding of the genetic basis of resistance traits. Such knowledge is crucial for breeding programs aiming to combine various resistance sources to develop cultivars with enhanced durability against PM. The identification of candidate genes within these regions further directs functional studies which are essential for confirming their role in resistance mechanisms and for future applications in precision breeding. 6 Cloning of Genes Resistant to PM The cloning of genes resistant to PM in Cucurbitaceae plants has seen significant advancements through various methodologies, including the use of molecular markers and GWAS. The case studies highlighted here demonstrate the potential for developing resistant cultivars and the importance of understanding the genetic basis of resistance. However, the ongoing challenges underscore the need for continued research in this field. 6.1 Methodologies for gene cloning in plant-fungal systems The study of plant-pathogen interactions, particularly in the context of PM in Cucurbitaceae, has been advanced through the cloning of genes that confer resistance to this disease. A key methodology involves the isolation and characterization of genes from the pathogen itself, such as the β-tubulin-encoding gene fromP. fusca, which has been used to develop molecular tools for various applications in PM research (Vela-Corcía et. al., 2014). This approach allows for the identification of genetic markers for molecular phylogenetics and the development of allele-specific assays for detecting resistance to fungicides (Vela-Corcía et. al., 2014).
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