Chloroplast Dna Phylogeography Of Subgenus Soja In China

DNA fragments within soybean chloroplast genome in representative Chinese accessions including wild soybean (G soja) and soybean landraces (G max) were sequenced for the study of the genetic patterns and population differentiation of differernt soybean geographic populations in China, the evolutionary rule during the process of domestication, and the origin of soybean by phylogeographical approaches, to further understand the molecular process of soybean domestication and the molecular mechanism of soybean origin and evolution. The main results are as follows:1 Twenty five cpDNA fragments in total of 14 550 bp in 379 soybean accessions were successfully sequenced. 47 SNPs including 41 single-base changes, 4 single-base indels and 2 multi-base indels were found. The 41 single-base changes is composed of 38 transversion and 3 transition, and Ts/Tv is 1:12.7, showing a strong "transversion bias" in soybean cpDNA. 45 and 15 SNPs were found respectively in G soja and G max and the SNPs frequency (θ) was 0.00049 and 0.00013 respectively, indicating that wild soybean harbors much more abundant genetic diversity in contrast to soybean landrace. The diversity of Huanghuai China population was highest in wild soybean and that of Southwest China population was highest in soybean landrace.2 The distribution of minor SNPs frequency in wild soybean was compared with that in soybean landraces. 32 and 3 rare SNPs were found respectively in G soja and G max suggesting that a large number of rare alleles were lost during soybean domestication. And the frequency of some other alleles increased despite the loss of those rare alleles. The distribution of minor SNPs frequency of wild soybean and soybean landraces in the same geographic region was shown to be different.3 Fifty nine haplotypes were detected. 47 and 18 haplotypes were found respectively in G. soja and G. max. In the wild soybean, the largest number of haplotypes (20) was found in North China and Huanghuai China population and the least (6) in Southwest China population. In the soybean landrace, the largest number of haplotypes was still found in North China population, and the least in Middle-south China. Specific haplotypes were detected in all of the geographic populations. Specifically deficient haplotypes which reflects the specificity of each geographic population were found only in few geographic populations.4 The AMOVA revealed that the level of variance between wild soybean and soybean landrace was higher than that among geographic populations, but lower than that within geographic populations, and a large proportion of the total variance existed within geographic populations. The differentiation between North China population of wild soybean and all geographic populations in soybean landrace was found to be the largest, while the differentiation between Midle-south China population in wild soybean and all geographic population in soybean landrace was least.5 The evolutionary relationship among the 59 cpDNA haplotypes detected was analyzed by the construction of haplotype networks based on geographical analysis. It is speculated that the origin center of wild soybean may lie in the North China., and Huanghuai China and Midle-south China may be the domestication centers of cultivated soybean, and most soybean landraces were domesticated in Midle-south China through different evolutionary history.