Molecular Plant Breeding 2024, Vol.15, No.3, 112-131 http://genbreedpublisher.com/index.php/mpb 120 5.2 Major breakthroughs in breeding for resistance to biotic and abiotic stresses The advent of molecular techniques has revolutionized cucurbit breeding, particularly in the context of resistance to biotic and abiotic stresses. The development of genetic transformation and gene editing technologies, such as CRISPR/Cas9-mediated gene knockout and base editing, has been a game-changer, allowing for precise modifications that confer resistance to various stresses (Feng et al., 2023). These breakthroughs have not only enhanced the resilience of cucurbit crops but have also accelerated the breeding process, bypassing some of the limitations of conventional breeding methods. 5.3 Development of cultivars with improved yield, quality, and nutritional value In the quest to combat micronutrient malnutrition, particularly in developing countries, breeding strategies for cucurbit crops have increasingly focused on biofortification and the enhancement of nutrient content and quality (Shafiin et al., 2020). The genomic information of cucurbit species has been instrumental in this regard, enabling breeders to identify and manipulate genes associated with nutritional content, thereby developing elite varieties with improved traits (Shafiin et al., 2020; Ma et al., 2022). The genome sequences of 18 different cucurbit species have been deciphered, shedding light on evolutionary relationships and functional genes that are key to agronomic traits such as fruit quality (Ma et al., 2022). This genomic knowledge, combined with nonconventional breeding approaches, has significantly contributed to the development of cucurbit cultivars with superior yield, quality, and nutritional value, offering promising solutions to global nutritional challenges (Shafiin et al., 2020; Ma et al., 2022). 6 Case Studies This section of the review focuses on key studies concerning major Cucurbitaceae species-cucumber, melon, and squash-highlighting the significant insights gained from genetic and genomic research and discussing their practical applications in modern agriculture. 6.1 Detailed review of key studies focusing on major Cucurbitaceae species 6.1.1 Cucumber (Cucumis sativus) The landmark study in the genetic research of cucumber that involved sequencing its genome is detailed in the paper titled “A chromosome-scale genome assembly of cucumber (Cucumis sativus L.)” (Li et al., 2019). This study presents a high-quality and complete cucumber genome assembly using single-molecule real-time (SMRT) long reads, which provided a more accurate and comprehensive reference genome than previous versions. The assembly revealed novel features of the cucumber genome, including a higher guanine-cytosine or adenine-thymine content in newly assembled regions and the identification of novel genes and full-length long terminal retrotransposons (Li et al., 2019). Another significant contribution to cucumber genome sequencing is described in the paper “The genome of the cucumber, Cucumis sativus L.” (Huang et al., 2009). This research reported the draft genome sequence of cucumber, which was assembled using a combination of Sanger and next-generation Illumina sequencing technologies. The study provided insights into the cucumber’s chromosome evolution, sex expression, disease resistance, and other traits (Huang et al., 2009). These two papers (Huang et al., 2009; Li et al., 2019) are pivotal in the field of cucumber genetics, providing essential resources for further genetic research and breeding programs. 6.1.2 Melon (Cucumis melo) Genomic studies in melon (Cucumis melo) have significantly advanced our understanding of the genetic determinants of fruit quality traits such as sweetness, aroma, and texture. These traits are essential for consumer preference and market value, and their genetic bases are being unraveled through various quantitative trait loci (QTL) mapping approaches.
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