Molecular Plant Breeding 2024, Vol.15, No.6, 379-390 http://genbreedpublisher.com/index.php/mpb 380 potato varieties, and evaluate the potential of modern breeding techniques to enhance sweet potato improvement efforts. By harnessing the genetic diversity of sweet potatoes, this study aims to facilitate the development of improved varieties to meet global food security challenges and meet the nutritional needs of a growing population. 2 Genetic Diversity in Sweet Potato 2.1 Sources of genetic diversity Sweet potato (Ipomoea batatas L.) exhibits significant genetic diversity, which is crucial for breeding and crop improvement. The sources of this diversity include natural genetic variation, human intervention, and the plant's out-crossing nature. Studies have shown that sweet potato landraces from different regions, such as Puerto Rico, display high levels of genetic diversity due to these factors (Rodríguez-Bonilla et al., 2014). Additionally, the presence of long terminal repeat (LTR) retrotransposons in the sweet potato genome contributes significantly to its genetic diversity (Meng et al., 2021). These retrotransposons are highly abundant and play a crucial role in the genetic makeup of sweet potato, making them valuable markers for genetic diversity studies. 2.2 Evolutionary history and domestication The evolutionary history and domestication of sweet potato are complex and involve multiple events of selection and adaptation. Sweet potato is believed to have been domesticated in Central or South America and subsequently spread to other parts of the world. The genetic diversity observed in sweet potato today is a result of both ancient domestication events and more recent human-mediated dispersal. For instance, the genetic diversity of sweet potato in Puerto Rico can be traced back to pre-Columbian times, indicating a long history of cultivation and selection (Rodríguez-Bonilla et al., 2014). Furthermore, studies using chloroplast SSR markers have shown that sweet potato accessions from different regions, including Korea, Japan, Taiwan, and the USA, exhibit distinct genetic clusters, reflecting their unique evolutionary paths (Lee et al., 2019). 2.3 Assessment of genetic diversity Assessing the genetic diversity of sweet potato is essential for effective breeding and conservation strategies. Various molecular markers, such as SSR, SNP, and retrotransposon-based markers, have been employed to evaluate the genetic diversity of sweet potato germplasm. For example, an assessment using SSR markers in Puerto Rico revealed a high level of genetic diversity among 167 sweet potato samples, with observed heterozygosity of 0.71 (Rodríguez-Bonilla et al., 2014). Similarly, a genome-wide assessment using SNP markers identified significant genetic variation among 197 sweet potato accessions, which were grouped into three major clusters based on their genetic relationships (Su et al., 2017). Retrotransposon-based insertion polymorphism (RBIP) markers have also been used to study the genetic diversity of sweet potato, revealing significant intergroup genetic variation (Meng et al., 2021). These assessments provide valuable insights into the genetic structure of sweet potato populations and inform breeding programs aimed at improving this important crop. 3 Key Traits for Sweet Potato Improvement 3.1 Yield and biomass Yield and biomass are critical traits for sweet potato improvement, as they directly impact the economic viability and food security potential of the crop. Genetic variability in sweet potato genotypes for traits such as tuber yield per plant, fresh weight of tubers, and the number of branches per plant has been observed, indicating significant potential for breeding programs to enhance these traits. The positive phenotypic correlation between fresh weight of tubers per plant and the number of tubers per plant, as well as days to maturity, suggests that selecting for these traits can lead to improved yield outcomes (Solankey et al., 2015). Additionally, the application of genetic transformation techniques has shown promise in enhancing yield and stress tolerance simultaneously, which is crucial for maintaining productivity under varying environmental conditions (Imbo et al., 2016). 3.2 Abiotic stress tolerance Abiotic stress tolerance is essential for the resilience of sweet potato crops, especially in the face of climate change. Various strategies have been employed to improve tolerance to stresses such as drought, salinity, and temperature extremes. For instance, the overexpression of the betaine aldehyde dehydrogenase (BADH) gene from spinach in sweet potato has been shown to enhance tolerance to multiple abiotic stresses, including salt,
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