Genetic Characterization and Differentiation of Natural Populations of Wild Soybean from Middle and Lower Valleys of Huanghe and Changjiang as Well as Their Genetic Relationship with the Cultivated Soybean
|School||Nanjing Agricultural College|
|Course||Crop Genetics and Breeding|
|Keywords||Wild soybean (Glycine soja Sieb. et Zucc) Natural population Genetic differentiation Cultivated soybean [Glycine max (L.) Merr.] Origin center|
It is well known that annual wild soybean, Glycine soja Sieb. et Zucc., is the ancestral species of the cultivated Soybean, Glycine max(L.)Merr.. It is an important source of major genes for resistance to pests, diseases and environmental stresses thus a natural gene bank for cultivated soybeans. In China, more than 6500 accessions of annual wild soybeans have been collected, representing more than 90% germplasm of G. soja in the world. Studies on the genetic characterization of annual wild soybeans provide the gene sources and materials for cultivated soybeans to broaden their genetic base. The origin centre of cultivated soybean can be presumed though the relationship between wild and cultivated soybean nowadays.This provides a base for the research on the origin and evolution of soybeans, which called attention by both botanists and soybean breeders.Many reaserchers thought that cultivated soybean was originated from the yellow river valley especially the middle and lower valley of Huanghe, but our team concluded that the ancestoral wild soybean in the middle and lower valley of Changjiang may be the primitive ancestor of cultivated soybean. Based on the viewpoint above, We prioritially chose nine wild natural populations from Zhengzhou and Yuanyang (Henan province), Jiaxiang (Shandong province), Linxiang and Xiangtan(Hunan province), Nanchang and Jiujiang (Jiangxi province), and randomly selected 24 accessions from each population, so we obtained a sample with 216 wild soybean accessions from the middle and lower valleys of Huanghe and Changjiang. In order to evaluate genetic charaterization, genetic relationship among different wild soybean populations based on the unclear and chloroplastic DNA variation, we analyzed the allelic profiles at 60 nuclear simple-sequence repeat (nuSSR) markers and 11 chloroplastic SSR (cpSSR) markers. Combined with the data of cultivated soybean provided by Soybean Research Institute of Nanjing Agricultural University, we can speculate the genetic relationship between wild populations and cultivated soybean.1. Genetic characterization of the natural populations of wild soybean The present analysis detected 795 alleles at the nuSSR loci in 9 G. soja populations, The cpSSR loci performed relatively low level of variation (only 21 alleles). The allele numbers and Simpson index of wild soybean from Nanchang population was much higher than those of other populations at nunclear SSR and chloroplastic SSR(A value was 348 and Simpson index was 0.66), and it had the most population-specific alleles(A value was 141). The coefficients of genetic similarity among nine populations at the chloroplastic SSR levels were much higher than those at the nunclear SSR levels. The genetic similarity coefficients between Zhengzhou and Yuanyang population had the largest value at both nuSSR (0.671) and cpSSR (0.970) level. The least coefficient at nuSSR level was 0.110 between Zhengzhou and Linxiangl population, and 0.773 between Zhengzhou and Xiangtan population at cpSSR level. The genetic richness of wild populations from the middle and lower valley of Changjiang was much higher than that from the middle and lower valley of Huanghe not only at nuclear genome level but also at chloroplastic genome level, their A value were 737 and 190, and Simpson index were 0.78 and 0.39, respectively.2. Genetic relationship among natural populations of wild soybean Cluster analysis of all accessions from nine populations based on nuSSR and cpSSR clearly showed that the wild accessions can be divided into four major clusters, i.e. populations from Zhengzhou and Yuanyang as a cluster(sojaⅠ), population from Jiangpu s the second(sojaⅡ), populations from Linxiang as the third(sojaⅢ), and populations from Xiangtan, Nanchang and Jiujiang as the last(sojaⅣ). Then we analyzed genetic diversity and specificity of the four clusters, populations from Xiangtan, Nanchang and Jiujiang(sojaⅣ) had the highest genetic diversity(A value was 501), the most population-specific alleles (277) and the least population-deficit alleles (6). Populations from the middle and lower valley of Huanghe had lowest genetic diversity(A value was 190) and the most population-deficit alleles (27). Population from Jiangpu(sojaⅡ) had the least accessions, but had the highest value of the average allells per accession (10.29) and average population-deficit allells per accession (0.50), and the value of average population-specific allells per accession (3.85) was only less to that of sojaⅣ.3. The evolutionary relationship between wild and cultivated soybean. Cluster analysis of wild and cultivated soybean samples clearly showed that wild accessions from Hunan (Xiangtan) and Jiangxi (Nanchang and Jiujiang) had a relatively smaller genetic distance with the cultivated soybean populations from six ecological regions. Some alleles in the cultivated soybean populations from Northeast China and HuangHuai valleys could not find in the related Analyses of population-specific alleles between the cultivated and wild accessions showed that 15 alleles from 11 Loci of nuSSR were commonly distributed in all cultivated populations and some wild accessions from Hunan and Jiangxi province, and only one allele (NTCP10-117) of cpSSR had a similar trend. Local wild populations, but were found in the wild population from the middle and lower valleys of Changjiang. It inferred that the wild populations from Hunan and Jiangxi might be most possible the ancestral species of cultivated soybean according to the progresses of the comparative biology and archaeology research.