Effects of ecological conditions on main quality traits of sweetpotato

Sweetpotato is one of the world's most important foods and industrial raw materials that is highly nutritious with a variety of beneficial ingredients. Sweetpotato chromosome is highly heterozygous with highly separable characteristics after hybridization. Furthermore, sweetpotato is a vegetatively propagated plant with stabilized traits during hybrid generation such that each line is a potential genotype. Storage root quality characteristics included the contents of total carotene, starch, reducing sugar, soluble sugar and protein. These storage traits are important indicators in measuring the consumption and processing quality of sweetpotato and are closely related with sweetpotato commodity. To study variations in storage root quality characteristics under different ecological environments and to provide a theoretical basis for screening specific cultivation areas conducive to the accumulation of certain quality traits, hybrids of "Xushu 25" and "Xu 22-5" were selected for research in four sites (Xuzhou, Jiangsu Province; Yantai, Shandong Province; Wanzhou, Chongqing City; Nanchang, Jiangxi Province) and two years (2008 and 2009). The results showed that ecological environment (E), year (Y), genetype (G), E×G and Y×G interactions had significant impacts on the contents of total carotene, starch, reducing sugar, soluble sugar and protein. Carotene showed that G×E interaction effect was larger than genotype and environmental effects. However, other quality traits showed that environmental effect was larger than genotype and G×E interaction effects. Soluble sugar and protein indicated that inter-annual effect was significantly higher than genotype or G×Y interaction effect. The remaining three quality traits indicated that G×Y interaction effect was larger than genotype or year effect. At the four experimental sites, the highest total carotene, reducing sugar and soluble sugar contents and the lowest starch content occurred at the Xuzhou site. The highest protein and lowest carotene contents occurred at Yantai site. Also the lowest protein and highest carotene contents occurred at Nanchang site. Then the lowest reducing and soluble sugar contents occurred at Wanzhou site. It was worthy to note that sweetpotato storage root protein content apparently increased with increasing latitude. For the two years, total carotene, reducing and soluble sugar contents in 2008 were higher than in 2009. Also starch and protein contents in 2008 were lower than in 2009. While the range of difference in starch and soluble sugar contents between the two years was small, that in the other traits was big. For the hundred different genotypes, coefficient of variation in total carotene content was largest, and that in starch content was smallest under different eco-sites and years.