Genetic and adaptational diversity in Chinese and European elite soybeans

Soybean (Glycine max [L.] Merr.) contributes to global food security through the supply of high-quality vegetable protein. China is the center of soybean origin, but soybean adaptation to European environments is important for mitigating climate change effects through increasing of domestic production in order to serve the growing need for plant-based protein in food production. Due to the short breeding history of European soybeans, a comparative analysis of genetic diversity and adaptational potential of Chinese and European elite cultivars would support future breeding initiatives. Therefore, 140 early maturity elite soybean cultivars of either Chinese or European origin were both genotyped (200K SNP array, SSR marker set, E-gene composition at E1-E4 loci) and evaluated across 17 European environments spanning a latitude range from 45 to 52°N. Genotyping results were revealing a clear differentiation between elite cultivars of either European or Chinese origin, and the level of diversity was similar between the two regions. Unique SSR alleles and E-haplotypes were found for both populations which demonstrates the preservation of genetic variation through a continuous selection for specific adaptation. European cultivars appear to be roughly based on two major ancestral lines, and genotypes are markedly structured along maturity groups due to regional adaptation needs. In contrast, Chinese cultivars trace back to a larger number of ancestors reflecting the rich background diversity present in soybeans from China. Wild-type alleles at E-loci significantly delayed flowering, and effects of particular E-alleles were clearly depending on geographic latitude. Photoperiod-insensitive E-haplotypes carrying non-functional E-alleles proved to be suitable for cultivation in higher latitudes of Europe with longer day-length, whereas photoperiod-sensitive late-maturity E-haplotypes are adapted to southern latitudes with respect to flowering time exclusively. The results suggest that specific diversity has been preserved both in Chinese and European cultivars of similar maturity, which could reciprocally be utilized in future breeding. This also applies to photoperiodic response, were new E-haplotypes could be created by combining Chinese and European alleles, which might enhance the potential of soybean adaptation to northern growing regions.