Abstract
Sweet potato (Ipomoea batatas L.) is a nutritious food crop and, based on the high starch content of its storage root, a potential bioethanol feedstock. Enhancing the nutritional value and starch quantity of storage roots are important goals of sweet potato breeding programs aimed at developing improved varieties for direct consumption, processing, and industrial uses. However, developing improved lines of sweet potato is challenging due to the genetic complexity of this plant and the lack of genome information. Short sequence repeat (SSR) markers are powerful molecular tools for tracking important loci in crops and for molecular-based breeding strategies; however, few SSR markers and marker-trait associations have hitherto been identified in sweet potato. In this study, we identified 1824 SSRs by using a de novo assembly of publicly available ESTs and mRNAs in sweet potato, and designed 1476 primer pairs based on SSR-containing sequences. We mapped 214 pairs of primers in a natural population comprised of 239 germplasms, and identified 1278 alleles with an average of 5.972 alleles per locus and a major allele frequency of 0.7702. Population structure analysis revealed two subpopulations in this panel of germplasms, and phenotypic characterization demonstrated that this panel is suitable for association mapping of starch-related traits. We identified 32, 16, and 17 SSR markers associated with starch content, β-carotene content, and starch composition in the storage root, respectively, using association analysis and further evaluation of a subset of sweet potato genotypes with various characteristics. The SSR markers identified here can be used to select varieties with desired traits and to investigate the genetic mechanism underlying starch and carotenoid formation in the starchy roots of sweet potato.
Highlights
Sweet potato (Ipomoea batatas (L.) Lam.) is an important food crop cultivated in over 100 countries (Gao et al, 2000; Huang and Sun, 2000; Hu et al, 2003)
We developed Short sequence repeat (SSR) markers in sweet potato and examined whether these markers were associated with important quality traits, such as dry matter content, β-carotene content, and starch content and composition of the storage root, in a set of 239 sweet potato accessions
The highest β-carotene content observed amongst the 239 genotypes was 8.538 mg/100 g flesh weight, which was obtained in the OFSP variety Tainong 69 in the year 2012 (Table 1 and Figure 2C)
Summary
Sweet potato (Ipomoea batatas (L.) Lam.) is an important food crop cultivated in over 100 countries (Gao et al, 2000; Huang and Sun, 2000; Hu et al, 2003). Sweet potato is cultivated for general consumption (fresh roots and leaves), is processed into livestock feed (Nedunchezhiyan et al, 2012), is grown as ornamental vines, and is an industrial raw material used to produce flour, candy, natural pigment, and a variety of starch-based industrial products (Hu et al, 2003; Nedunchezhiyan et al, 2010, 2012). Developing sweet potato varieties with high levels of dry matter content, starch, and β-carotene is an important goal of breeding programs aimed at generating improved varieties for direct consumption, processing, and industrial applications (Nedunchezhiyan et al, 2012)
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