Abstract
To ascertain genetic diversity, population structure and linkage disequilibrium (LD) among a representative collection of Chinese winter wheat cultivars and lines, 90 winter wheat accessions were analyzed with 269 SSR markers distributed throughout the wheat genome. A total of 1,358 alleles were detected, with 2 to 10 alleles per locus and a mean genetic richness of 5.05. The average genetic diversity index was 0.60, with values ranging from 0.05 to 0.86. Of the three genomes of wheat, ANOVA revealed that the B genome had the highest genetic diversity (0.63) and the D genome the lowest (0.56); significant differences were observed between these two genomes (P<0.01). The 90 Chinese winter wheat accessions could be divided into three subgroups based on STRUCTURE, UPGMA cluster and principal coordinate analyses. The population structure derived from STRUCTURE clustering was positively correlated to some extent with geographic eco-type. LD analysis revealed that there was a shorter LD decay distance in Chinese winter wheat compared with other wheat germplasm collections. The maximum LD decay distance, estimated by curvilinear regression, was 17.4 cM (r2>0.1), with a whole genome LD decay distance of approximately 2.2 cM (r2>0.1, P<0.001). Evidence from genetic diversity analyses suggest that wheat germplasm from other countries should be introduced into Chinese winter wheat and distant hybridization should be adopted to create new wheat germplasm with increased genetic diversity. The results of this study should provide valuable information for future association mapping using this Chinese winter wheat collection.
Highlights
Wheat (Triticum aestivum L.) is one of the most important cereal crops worldwide
The genetic diversity of the 90 Chinese winter wheat accessions in this study was at a lower level, as reflected by the mean genetic diversity value (0.6) and average number of alleles per locus (5.05)
The genetic diversity of 559 French wheat accessions was evaluated using 42 SSR markers; 14.5 alleles were identified per locus and a polymorphic information content (PIC) value of 0.66 was obtained [21]
Summary
Wheat (Triticum aestivum L.) is one of the most important cereal crops worldwide. In China, wheat is grown on about 24 million hectares with a total annual production of 115 million tons and an average yield of 4.75 tons ha-1. Over the past 60 years, wheat breeders have made remarkable progress in improving grain yield, disease resistance, quality and agronomic performance by using excellent germplasm resources. The recurrent use of a few elite germplasm lines as parental stock, has led to a decrease in genetic diversity and has narrowed the genetic base for wheat improvement [1]. The degree of genetic diversity found in contemporary germplasm from breeding programs may indirectly reflect the level of genetic progress achievable in future cultivars. Evaluation of wheat genetic diversity is essential to the effective use of genetic resources in breeding programs
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