| In the process of wheat breeding in some major agronomic, yield and quality, due to repeated use of the same parental genotypes in modern breeding programs, genetic diversity in wheat cultivars has been increasingly narrowed. It is thus important to assess the genetic diversity in wheat germplasm for collection, conservation, and effective application of genetic resources and ultimately broadening genetic bases in wheat cultivar development. In this paper, SSR markers were used to study the diversity among 65 cultivars from different provinces or ecological zones in China, and 13 representative wheat materials were selected to do cytological analysis. The results obtained are as follows:1. The diploid chromosomal number of all 13 wheat varieties is 2n= 6x= 42. Chromosomes have little differences in size and shape, and the ranges of relative length are closed to each other. The ratio of the longest and the shortest chromosome ranges from 1.6 to 4.0, the average arm ratio ranges from 1.199 to 1.366. All tested materials contain a pair of satellites in 1B and 6B chromosomes. The asymmetry coefficient of the materials ranged from 54.36% to 57.23% with an averaging of 55.80%. The karyotypes of all materials are all belong to symmetrical karyotype. The karyotypes of zhengmai9405 and shan228 belong to 1A, and karyotypes of kanto107 and yanzhan 1 belong to 2B, and others are belong to 1B.2. There are some differences of N-band in 13 tested wheat varieties. The total number of bands is detected from 43 to 83 with an average of 54. The variance of centromere bands is smaller in different materials, which ranged from 16 to 21 with an average of 18. The large variance is detected in intercalary band of 13 materials, ranged from 13 to 30 with 18 on average on long arm of chromosome and from 11 to 30 with an average of 17 on short arm of chromosome. By N-band,13 wheat materials can be identified. According to the N-banding idiogram, we can conclude that B genome has the highest variability in wheat 3 genomes and A genome has the smallest one.3.47 pairs of SSR primers, uniformly distributed in 21 linkage groups of common wheat, were used to study the genetic diversity of 65 wheat cultivars. The results showed that the 47 pairs of primers produced a total of 416 polymorphic sites. The average number of alleles per SSR locus was 8.8, ranged from 3 to 15. The polymorphism information content (PIC) of SSR loci varied from 0.752 to 0.804 with an average of 0.770. Comparing the 3 genomes of the germplasm, the average allele richness was B(9.28) > A(9.07)> D(8.13), and the average PIC value was B(0.774)> A(0.772)> D(0.766), this result is similar to N-band analysis. Genetic distances among the 65 cultivars ranged from 0.398 to 0.672 with an average of 0.561. Cluster analysis based on genetic distance of SSR markers indicated that all 65 tested cultivars could be classified into 7 clusters at the level of GD=0.568, basically reflected the genetic relationships among species. |
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