Molecular Plant Breeding 2025, Vol.16, No.2, 133-145 http://genbreedpublisher.com/index.php/mpb 136 4.2 Genes associated with stress resistance 4.2.1 Drought, heat, and salinity tolerance genes Several genes have been identified that enhance sweet potato's tolerance to abiotic stresses such as drought, heat, and salinity. The IbMIPS1 gene, which encodes myo-inositol-1-phosphate synthase, improves salt and drought tolerance by regulating inositol biosynthesis and ROS scavenging pathways (Zhai et al., 2016). Similarly, the IbNAC7 gene has been shown to confer salt tolerance by enhancing catalase activity and reducing ROS accumulation (Meng et al., 2020). The ItfWRKY70 gene from Ipomoea trifida also plays a significant role in drought tolerance by regulating ABA biosynthesis and ROS scavenging systems (Sun et al., 2022b). 4.2.2 Impact on consistent yield across different environments The overexpression of stress-responsive genes such as IbBBX24, IbPRX17, and IbMIPS1 not only enhances stress tolerance but also contributes to maintaining consistent yield across different environmental conditions. For instance, transgenic sweet potato plants overexpressing IbMIPS1 showed improved yield under field conditions with salt and drought stress (Zhai et al., 2016). Similarly, the IbBBX24-IbTOE3-IbPRX17 module enhances tolerance to salt and drought, thereby stabilizing yield under adverse conditions (Figure 1) (Zhang et al., 2021). These genetic modifications ensure that sweet potato plants can sustain productivity despite environmental challenges. 4.3 Genes involved in photosynthesis efficiency Photosynthesis efficiency is a critical factor for plant growth and yield. Genes such as IbMIPS1 have been implicated in enhancing photosynthesis under stress conditions by regulating the ROS scavenging system and maintaining chlorophyll content (Zhai et al., 2016). Additionally, the IbNAC7 gene has been shown to improve photosynthesis efficiency by increasing chlorophyll and proline contents while reducing malondialdehyde (MDA) content under salt stress (Meng et al., 2020). These genes help maintain photosynthetic activity, thereby supporting higher yields. 4.4 Genes affecting flowering and maturity Flowering and maturity are key developmental stages that influence yield. While specific genes directly affecting these stages in sweet potato are less documented, the overall stress response and developmental genes such as IbBBX24 and IbMIPS1 indirectly contribute to timely flowering and maturity by ensuring plant health and stress resilience (Zhai et al., 2016; Zhang et al., 2021). Further research into the genetic regulation of these stages could provide more targeted approaches to enhancing yield through genetic manipulation. 5 Genetic Diversity and Domestication of Sweet Potato 5.1 Insights into the origin and domestication of sweet potato The domestication of sweet potato (Ipomoea batatas L. Lam) is a complex process that has involved significant genetic changes from its wild relatives. Sweet potato is believed to have originated in Central or South America, where it was domesticated by indigenous peoples. The genetic diversity of sweet potato is relatively high, which is indicative of its long history of cultivation and selection for various traits. Studies have shown that sweet potato has undergone significant genetic changes during domestication, including the selection for traits such as tuber size, shape, and nutritional content (Lee et al., 2019; Paliwal et al., 2020). 5.2 Genomic studies revealing genetic diversity across cultivars Genomic studies have been instrumental in revealing the genetic diversity present in sweet potato cultivars. For instance, the use of morphological, biochemical, and molecular markers has allowed researchers to assess the genetic variation among different sweet potato genotypes. One study analyzed 21 sweet potato genotypes using these markers and found significant genetic diversity, which is crucial for breeding programs (Paliwal et al., 2020). Another study utilized chloroplast simple sequence repeat (cpSSR) markers to analyze 558 sweet potato accessions, revealing 33 distinct chlorotypes and highlighting the need for more diverse germplasm collection (Lee et al., 2019). Additionally, retrotransposon-based insertion polymorphism (RBIP) markers have been used to study the genetic diversity of sweet potato, further confirming the presence of significant genetic variation among different germplasms (Meng et al., 2021).
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