Molecular Plant Breeding 2025, Vol.16, No.2, 133-145 http://genbreedpublisher.com/index.php/mpb 140 7.3 Genome-wide association studies (GWAS) for identifying yield and nutrient-related genes Genome-wide association studies (GWAS) are a powerful method for identifying genetic loci associated with important agronomic traits. By analyzing the genetic variation across a diverse panel of genotypes, GWAS can pinpoint specific SNPs linked to traits such as yield, nutrient content, and stress resistance. For example, GWAS has been used to dissect the genetic architecture of grain yield in bread wheat, identifying loci that can be targeted for marker-assisted selection (Li et al., 2019). Applying GWAS to sweet potato can similarly uncover key genes involved in nutrient composition and yield, providing valuable targets for breeding programs aimed at improving these traits. The integration of high-density genetic markers and advanced statistical methods enhances the reliability and resolution of GWAS, making it a crucial tool for sweet potato genomic breeding 8 Case Studies 8.1 Enhancing beta-carotene content through genomic approaches Beta-carotene is a vital nutrient, and enhancing its content in sweet potatoes can significantly contribute to alleviating vitamin A deficiency. A study evaluated the genotype by environment interactions in the yield and nutraceutical traits of orange-fleshed sweet potato (OFSP) storage roots in different agro-climatic zones of northern Ethiopia. The results demonstrated that certain genotypes, such as Ininda, Gloria, and Amelia, provided higher yields and beta-carotene content, suggesting that genotype selection can effectively enhance beta-carotene levels in sweet potatoes (Lamaro et al., 2023). This approach highlights the potential of using genomic tools to select and breed sweet potato varieties with improved nutritional profiles. 8.2 Improving drought tolerance via gene editing techniques Drought tolerance is a critical trait for sweet potato cultivation, especially in regions prone to water scarcity. Several studies have focused on identifying and manipulating genes associated with drought tolerance. For instance, the overexpression of the IbMIPS1 gene in transgenic sweet potatoes significantly enhanced drought tolerance by up-regulating genes involved in stress responses and the ABA signaling pathway (Zhai et al., 2016). Additionally, RNA-sequencing analysis identified numerous drought-responsive genes, including those from the bHLH, bZIP, and WRKY families, which are crucial for developing drought-tolerant sweet potato cultivars (Figure 3) (Arisha et al., 2020). These findings underscore the effectiveness of gene editing and genomic approaches in improving drought tolerance in sweet potatoes. Figure 3 Transcription factors differentially expressed (A) and stress related protein genes (B) induced under drought stress in Xuzi-8 sweetpotato cultivar (Adopted from Arisha et al., 2020)
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