Sweetpotato (Ipomoea batatas (L.) Lam.) is recognized as one of the most important root crops in the world by the Food and Agriculture Organization of the United Nations. The yield of sweetpotato is closely correlated with the rate of storage root (SR) formation and expansion. At present, most of the studies on sweetpotato SR expansion are focused on the physiological mechanism. To explore the SR expansion mechanism of sweetpotato, we performed transcriptome sequencing of SR harvested at 60, 90, 120, and 150 days after planting (DAP) to analyze two sweetpotato lines, Xuzishu 8 and its crossing progenies named Xu 18-192, which were selected from an F₁ segregation population of Xuzishu 8 and Meiguohong, in which SR expansion was delayed significantly. A total of 57,043 genes were produced using transcriptome sequencing, of which 1312 were differentially expressed genes (DEGs) in four SR growth periods of the sweetpotato lines. The combination of the KEGG and trend analysis revealed several key candidate genes involved in SR expansion. The SBEI gene involved in starch metabolism, and transcription factors ARF6, NF-YB3 and NF-YB10 were all significantly up-regulated during SR expansion. The data from this study provide insights into the complex mechanisms of SR formation and expansion in sweetpotato and identify new candidate genes for increasing the yield of sweetpotato.

Although salinity stress is one of the principal abiotic stresses affecting crop yield, a suitable concentration of NaCl has proven to be useful for increasing crop quality. This study used low salinity (34 mmol/L NaCl) and high salinity (85 mmol/L) to cultivate purple sweetpotato. Using transcriptomics and metabolomics to profile the pathway indicated that glycometabolism, secondary metabolite biosynthesis and the starch catabolic process were the significant pathways under the salinity stress. Further research showed that purple sweetpotato could regulate genes related to the regulation of the cellular Na⁺, K⁺, and other ions concentration in response to the low salinity tolerance, but loses this ability under high salinity. Meanwhile, under low salinity, the activity of antioxidant enzymes and their related gene expression are maintained at a high level. The low salinity influences the monosaccharide composition as well as the content and regulation of genes related to starch synthesis. Quality analysis showed that the low salinity could increase the starch content and influence the amylopectin biosynthesis. It suggested that low salinity promotes substance accumulation. High salinity could increase the anthocyanins biosynthesis and low salinity had a significant impact on phenolic acid and flavonol. Finally, the gene expression levels also prove the low salinity could change the composition and content level of the purple sweetpotato. This study showed that an appropriate concentration of NaCl can be used as an elicitor for application in purple sweetpotato planting.

Abscisic acid (ABA), a critical phytohormone that regulates plant development and stress response, is sensed by the ABA receptors PYR/PYL/RCAR (PYLs). The PYL genes have been widely studied in multiple plant species, while a systematic analysis of PYL genes in the genus Ipomoea remains unperformed. Here, a total of 13, 14, and 14 PYLs were identified in Ipomoea batatas, Ipomoea trifida, and Ipomoea triloba, respectively. Fragment duplication was speculated to play prominent roles in Ipomoea PYL gene expansions. These Ipomoea PYLs were classified into three subfamilies via phylogenetic analysis, which was supported by exon–intron structures and conserved motif analyses. Additionally, the interspecies collinearity analysis further depicted a potential evolutionary relationship between them. Moreover, qRT-PCR analysis showed that multiple IbPYLs are highly and differentially responsive to abiotic stress treatments, suggesting their potential roles in sweetpotato stress responses. Taken together, these data provide valuable insights into the PYLs in the genus Ipomoea, which may be useful for their further functional analysis of their defense against environmental changes.

Purple-fleshed sweetpotato (PFSP) (Ipomoea batatas (L.) Lam), whose flesh is purple to dark purple, is a special variety type of sweetpotato, which has the characteristics of food crop, industrial crop and medicinal crop. The storage root (SR) of PFSP is rich in anthocyanins, starch, protein, soluble sugar, mineral elements, polyphenol, dietary fiber and so on, which has balanced and comprehensive nutritional value. And in recent years, its unique nutritional elements are increasingly known for their health functions. At present, there is no article on the characteristics and quality analysis of industrial xz8 variety. To explore the influence of different environments on the processing quality of xz8, we selected nine regions (Xuzhou, Jiawang, Pizhou, Xinyi, Peixian, Sihong, Yanchen, Xiangyang and Tianshui) to measure its yield and quality changes. The data demonstrated that xz8 has a very consistent high yield performance. In Tianshui, the anthocyanins, protein and minerals contents were significantly higher and yield also above average. Moreover, the variety with the lowest starch content exhibited the best taste. On the basis of the above results, it suggested that quite practicable to promote xz8 cultivation and suitable for processing in these areas. Thus, our present findings improve our understanding of xz8 variety and provide the basis for the industrial production of PFSP with strong prospects for success.