Plant Gene and Trait 2024, Vol.15, No.6, 275-284 http://genbreedpublisher.com/index.php/pgt 277 3.2 The role of major germplasm banks and research institutions Major germplasm banks and research institutions play a crucial role in the collection, preservation, and characterization of sweet potato germplasm. The CIP, for example, not only maintains a vast collection but also conducts genotyping and phenotyping to ensure the accuracy and utility of the germplasm. Their efforts have identified significant genetic diversity and population structure within their collection, which is essential for breeding and conservation programs (Anglin et al., 2021). The NAC in South Korea also contributes significantly by maintaining a diverse collection and conducting genetic diversity assessments to inform future preservation and breeding strategies (Lee et al., 2019). These institutions provide valuable resources and data that support global sweet potato improvement efforts. 3.3 Advances in germplasm preservation technologies Recent advances in germplasm preservation technologies have greatly enhanced the ability to maintain and utilize sweet potato genetic resources. Techniques such as retrotransposon-based insertion polymorphism (RBIP) markers have been developed to study genetic diversity and population structure in sweet potato. These markers have proven effective in revealing high levels of polymorphism and genetic variation among sweet potato accessions, which is crucial for identifying and preserving diverse genetic traits (Meng et al., 2021). Additionally, genome-wide assessments using specific length amplified fragment (SLAF) sequencing have provided detailed insights into the genetic relationships and population structure of sweet potato accessions, facilitating the development of core germplasm sets for targeted breeding programs (Su et al., 2017). These technological advancements are instrumental in ensuring the long-term conservation and effective utilization of sweet potato germplasm. 4 Genetic Diversity in Sweet Potato 4.1 Progress in studying sweet potato genetic diversity using molecular markers The use of molecular markers, particularly simple sequence repeats (SSRs), has significantly advanced the study of genetic diversity in sweet potato. SSR markers are highly polymorphic and reproducible, making them ideal for genetic studies. For instance, a high-density SSR genetic linkage map was developed for sweet potato, which included 5 057 SSR markers covering 13 299.9 cM with a marker density of 2.6 cM in one parent map and 3 009 SSR markers covering 1 122.9 cM with a marker density of 3.7 cM in another parent map. This map is consistent with the autohexaploid nature of sweet potato and provides a robust foundation for quantitative trait locus (QTL) mapping and marker-assisted breeding (Meng et al., 2021). Additionally, SSR markers have been used to assess the genetic diversity of sweet potato germplasms collected worldwide, revealing significant polymorphisms and genetic variability among accessions (Lee et al., 2019). 4.2 Application of genomic analysis in revealing genetic structure and diversity Genomic analysis using SSR markers has been instrumental in uncovering the genetic structure and diversity of sweet potato. For example, a study using nine chloroplast SSR markers on 558 sweet potato accessions from the National Agrobiodiversity Center (NAC) identified 33 chlorotypes and divided the accessions into four clusters based on their genetic relationships. This analysis highlighted the low genetic diversity of female parents in the NAC collection, suggesting the need for more diverse germplasm collection (Lee et al., 2019). Another study on Brazilian sweet potato landraces using SSR markers found high genetic and intravarietal diversity, with most variability distributed within households rather than between communities. This indicates the influence of outcrossing and anthropic factors such as selection and maintenance of different varieties within small plots and home gardens (Veasey et al., 2008). 4.3 Research on genetic differences and phylogenetic relationships among sweet potato germplasm Research on genetic differences and phylogenetic relationships among sweet potato germplasm has provided insights into the evolutionary history and breeding potential of this crop. The development of SSR linkage maps has facilitated the identification of homologous groups and the understanding of the genetic architecture of sweet potato (Meng et al., 2021). Furthermore, studies using SSR markers have revealed significant genetic diversity among sweet potato accessions from different geographical regions. For instance, the genetic diversity assessment
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