Plant Gene and Trait 2024, Vol.15, No.6, 305-313 http://genbreedpublisher.com/index.php/pgt 309 environmental stresses such as drought. Sweet potato, being a key crop for food security, especially in developing countries, faces significant challenges due to osmotic stress, which impacts its agronomic and economic productivity. Plants respond to water stress through various signaling pathways that modify growth patterns, activate antioxidants, accumulate suitable solutes and chaperones, and produce stress proteins. These physiological, metabolic, and genetic modifications serve as indicators for selecting drought-tolerant genotypes (Figure 2). The main objective of sweet potato breeding in drought-affected regions is to develop varieties that combine drought tolerance with high yields. This involves studying the physiological and biochemical features of certain varieties to implement effective drought resistance measures. By regulating genetics, the creation of drought-resistant varieties can become cost-effective for smallholder farmers (Sapakhova et al., 2023). The use of multi-trait selection indices, stability, and genetic gain analysis in multi-environmental evaluations has proven effective in selecting superior sweet potato genotypes that exhibit better profiles and stability (Rosero et al., 2023). Transcriptomic analyses have also revealed mechanisms for different drought tolerance levels in sweet potato cultivars, identifying new genes and transcripts that play roles in drought response (Liu et al., 2023). Figure 2 Mechanism of plant tolerance to drought stress (Adopted from Sapakhova et al., 2023) 6.2 Case analysis: promotion of drought-resistant sweet potato in northern China In Northern China, where drought is a frequent environmental stress during the sweet potato growing season, the promotion of drought-resistant sweet potato varieties has been a significant focus. China, having the largest sweet potato planting area worldwide, faces challenges in maintaining growth and yield under drought conditions. Studies have shown that the application of salicylic acid (SA) can mitigate drought stress in sweet potato by enhancing antioxidant defense systems and modulating abscisic acid-related gene expression (Zhao, 2024). This approach has been effective in reducing oxidative damage and maintaining optimized osmotic environments in drought-stressed plants. For instance, foliar spraying of SA on drought-stressed sweet potato varieties has been shown to induce resistance, thereby increasing growth and crop yield (Huang et al., 2022). Transcriptomic analyses have provided insights into the molecular mechanisms underlying drought tolerance in different sweet potato cultivars, revealing that drought-tolerant cultivars regulate various metabolic pathways to cope with stress. These findings are crucial for selecting and promoting drought-resistant sweet potato varieties in regions like Northern China, where drought conditions are prevalent (Liu et al., 2023). 7 Summary of Case Analyses and Evaluation of Breeding Effectiveness 7.1 Comprehensive analysis of case studies The case studies on sweet potato breeding have demonstrated significant advancements in addressing key agronomic traits such as drought tolerance, yield improvement, and nutritional enhancement. The study by the
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