Variability of sweet potato storage root under different ecological environments and its correlation with quality traits

Sweet potato is an important food/energy crop and is crucial for addressing poverty and malnutrition in developing countries. In addition to inherited issues, sweet potato is highly sensitive to environment conditions. Genotypic variations in yield-related traits and their relationships with main storage root quality traits were investigated using the 105 sweet potato hybrids (derived from "Xushu 25" and "Xu 22-5") in four ecological environments (Xuzhou City, Yantai City, Wanzhou City and Nanchang City). The vine length, stem diameter, branch number, storage root number, aboveground fresh weight, aboveground dry matter content, storage root fresh weight, and storage root dry matter content were investigated in the study. Carotene content was determined using the acetone extraction method. Starch, reducing sugar, soluble sugar and protein contents were measured using the near infrared reflectance spectrometer method in the laboratory. The results showed that environment (E), genotype (G) and their interactions (E×G) had significant (P < 0.01 or P < 0.05) impacts on main yield traits. E×G had no significant effect on aboveground dry matter content. The effects of environment on main yield-related traits were much higher than those of genotype and E×G. There was a wide range of main yield traits for different ecological conditions. The highest coefficient of variation was for the fresh weight of storage root per plant, followed by dry weight of storage root per plant (which was for Yantai site). The lowest coefficient of variation was dry matter content of storage root (for Xuzhou site). For the four experimental sites, the highest vine length and branch number per plant, and the lowest stem diameter and storage root number per plant were in Xuzhou site. The highest stem diameter, aboveground fresh weight, aboveground dry weight and fresh weight of storage root per plant, and the lowest aboveground dry matter content were in Yantai site. The lowest vine length, aboveground fresh weight and aboveground dry weight per plant, and the highest aboveground dry matter content, dry matter content of storage root, storage root number and dry weight of storage root per plant were in Nanchang site. The lowest dry matter content of storage root, branch number, fresh weight of storage root and dry weight of storage root per plant were in Wanzhou site. For Xuzhou site, dry weight of storage root per plant had a positive correlation with starch content. Fresh and dry weights of storage root per plant had negative correlation with protein content. For Yantai site, fresh weight of storage root had positive and significant correlation with total carotenoid content. Also the fresh and dry weights of storage root had negative correlation with protein content. For Nanchang site, fresh weight of storage root had positive correlation with soluble sugar content, but negative correlation with protein content. The dry weight of storage root was positively correlated with starch content. Then for Wanzhou site, fresh weight of storage root was positively correlated with starch content. It was then concluded from the results of the correlation analysis that the fresh weight of storage root per plant was negatively correlated with protein content. This suggested that it was difficult to get sweet potato varieties with high yield and high protein.