Sweetpotato (Ipomoea batatas (L.) Lam.) is a widely grown food crop especially in developing countries. Increasing storage-root yield and dry-matter content has been the main breeding objective of the crop, and DNA marker-assisted breeding is needed for this purpose. In this study, using a mapping population of 500 F₁ individuals from a cross between Xushu 18 (female) and Xu 781 (male), we constructed a high-density genetic linkage map of sweetpotato using 601 simple-sequence repeat (SSR) primer pairs. The Xushu 18 map contained 90 linkage groups with 5547 SSR markers and spanned 18,263.5 cM, and the Xu 781 map contained 90 linkage groups with 4599 SSR markers and spanned 18,043.7 cM, representing the highest genome coverage yet reported for sweetpotato. We identified 33 QTL for storage-root yield and 16 QTL for dry-matter content, explaining respectively 6.5%–47.5% and 3.2%–18.9% of variation. These results provide a foundation for fine-mapping and cloning of QTL and for marker-assisted breeding in sweetpotato.

Sucrose non-fermenting-1-related protein kinase-1 (SnRK1) regulates carbon and nitrogen metabolism in plants. However, its roles and their underlying mechanisms in tolerance to abiotic stresses are little known. The present study indicated that the IbSnRK1 gene was strongly induced by NaCl, polyethylene glycol (PEG) 6000, hydrogen peroxide (H₂O₂), cold (4 ℃), and abscisic acid (ABA). Its overexpression significantly increased salt, drought, and cold tolerance in transgenic sweet potato plants. ABA, proline, and K⁺ contents were significantly increased, whereas malondialdehyde (MDA), Na⁺ and H₂O₂ contents and O₂⁻ production rate were significantly decreased in the transgenic plants under salt, drought, and cold stresses. Overexpression of the gene up-regulated genes involved in ABA biosynthesis, stress response, and stomatal closure; increased enzyme activities in the reactive oxygen species (ROS) scavenging system; and controlled stomatal closure under salt, drought, and cold stresses. These results show that the IbSnRK1 gene confers salt, drought, and cold tolerance in sweet potato by activating the ROS scavenging system and controlling stomatal closure via the ABA signaling pathway.