Genetic Contribution of Introduced Varieties to Wheat Breeding in China Evaluated Using SSR Markers

Abstract

Foreign germplasm has exerted important influence on wheat(Triticum aestivum L.) breeding in China.To uncover the genetic contribution of introduced varieties to Chinese wheat breeding,44 representative accessions,consisting of 11 introduced important parents from 1950s to 1970s and 33 representative domestic varieties which were released in different years in China,were evaluated using 363 SSR markers distributing on 21 chromosomes.The 11 introduced accessions contained 76.3% of the alleles presented in total 33 Chinese accessions.Comparing the pattern of variability among introduced accessions and the groups of varieties released over time,we found that the mean number of alleles amplified was the highest in foreign germplasm(3.92),similar to each other between 1960s and 1970s(2.86 and 3.01,respectively),and that in 1980s was a little higher(3.46).The result on genetic distance among different groups was accorded with the pattern of the allelic diversity.On the other hand,comparing the allelic frequencies between introduced and improved accessions at each SSR locus we found that certain chromosomal regions underwent strong selection in wheat breeding.At least 33 SSR loci on 14 chromosomes with the exception of 4A,6A,7A,1B,3B,3D,and 5D,the alleles amplified in foreign accessions were selected preferentially and transmitted to Chinese accessions,whose frequencies were over 70% in either group of accessions.Furthermore,some of the markers were correlated with known wheat genes controlling important traits reported in literatures,including resistance to pests such as strip rust,leaf rust and powdery mildew,and other characters such as yield,growth stage and dormancy.In conclusion,the chromosomal regions selected preferentially play an important role in the improvement of wheat in China,which should be studied further.