Geographic distributions and the regionalization of soybean seed compositions across China.

As one of major food crops, soybean is grown over a broad ecological region in China with considerable variations in environmental conditions, and the seed compositions of soybeans are diverse among different regions. To clarify the spatial patterns of soybean seed compositions, crude oil, protein, and 11 categories of functional components were quantified in 1792 soybean samples collected from a vast range of soybean planting regions across China spanning from 2010 to 2017. The Kriging interpolation maps presented a clear north-to-south (high latitude to low latitude) increasing trend in contents of crude protein and dietary fiber and decreasing trend in contents of crude oil, phospholipids, saponins, and carotenoids. Soybeans with high-level of total oligosaccharide were concentrated in the central region. Based on the geographical distribution of soybean nutritional components, weather conditions, and cultivation systems, the soybean production areas in China were divided into three regions and 10 subregions. This study highlights the geographic distribution of soybean nutritional compositions and provides scientific evidence for guiding the construction of high-quality edible soybean production bases in China.

Analyzing the Effects of Climate Factors on Soybean Protein, Oil Contents, and Composition by Extensive and High-Density Sampling in China.

From 2010 to 2013, 763 soybean samples were collected from an extensive area of China. The correlations between seed compositions and climate data were analyzed. The contents of crude protein and water-soluble protein, total amount of protein plus oil, and most of the amino acids were positively correlated with an accumulated temperature ≥15 °C (AT15) and the mean daily temperature (MDT) but were negatively correlated with hours of sunshine (HS) and diurnal temperature range (DTR). The correlations of crude oil and most fatty acids with climate factors were opposite to those of crude protein. Crude oil content had a quadratic regression relationship with MDT, and a positive correlation between oil content and MDT was found when the daily temperature was <19.7 °C. A path analysis indicated that DTR was the main factor that directly affected soybean protein and oil contents. The study illustrated the effects of climate factors on soybean protein and oil contents and proposed agronomic practices for improving soybean quality in different regions of China. The results provide a foundation for the regionalization of high-quality soybean production in China and similar regions in the world.