Genetic Diversity Analysis Of Leading Varieties And Accurate Phenotypic Identification Of Germplasm In Brassica Napus L.

To Provide reference for variety evaluation,germplasm improvement and variety breeding,the genetic diversity and genetic relationship of certain leading varieties of oilseed rape(Brassica napus L.)in China were studied.62 varieties including leading varieties and a few new varieties were genotyped by 47 pairs of SSR markers which were specified in the technical specification NY/T2468-2013 for oilseed rape variety identification.Genetic diversity parameters and cluster analysis were calculated according to variety source and suitable planting area.In addition to identify the core phenotypes closely related to yield and screen excellent germplasm resources suitable for utilization in Huang Huai Region,the genetic diversity and phenotypic relationship of oilseed rape germplasm were studied.The phenotypes of 827 germplasm resources were accurately identified,and the variation,distribution and genetic diversity of 17 phenotypes were analyzed.The relationship between phenotypes was studied by correlation,R-type factor clustering,principal component and grey correlation analysis;the important phenotypes were used to select excellent germplasm.The main results are as follows:1)The genetic diversity of four winter ecological area accessions from 62 oilseed rape varieties was moderately rich,from high to low are as follows: the middle reaches of the Yangtze River,the Yellow and Huai area,the upper reaches of the Yangtze River and the lower reaches of the Yangtze River.By allelic variation analysis,the specific deficiency alleles of each area were found,with 4 in the Yellow and Huai area,and the varieties carrying the specific deficiency allele were found;cluster analysis showed that genetic relationships between accessions of the upper and the lower reaches of the Yangtze River were closer,genetic relationships between accessions of the Yellow and Huai area and the middle reaches of the Yangtze River were closer,genetic relationships between accessions of the Yellow and Huai area and the lower reaches of the Yangtze River were the farthest.The genetic diversity of accessions in each suitable planting area is moderately rich,from high to low are as follows: wide adaptation variety,the middle reaches of the Yangtze River,the Yellow and Huai area,the upper reaches,the lower reaches,spring rape region.By allelic variation analysis,the specific deficiency allele of each suitable planting area was found,with 2 in the Yellow and Huai area,and the varieties carrying the specific deficiency allele were found;wide adaptation varieties have 10 high-frequency alleles,the frequency of which is very low in the accessions of Huang Huai area,and the varieties carrying the alleles were found out.The accessions of wide adaptation and the middle reaches of the Yangtze River are grouped into one class by systematic clustering.The genetic relationship between the accessions of the Huang Huai area and wide adaptation is far behind that between the accessions of wide adaptation and the middle,upper and lower reaches of the Yangtze River.2)827 germplasm resources had a wide range of phenotypic variation;the frequency distribution of plant height and plot yield fitted normal distribution,and other phenotypic distribution was similar to normal distribution;Simpson,Shannon,Pielou evenness and Brillouin diversity index showed that the genetic diversity of each phenotype is highly rich.Partial correlation analysis showed that there was a significant direct correlation between plot yield and plant height,1000 grain weight,grain yield per plant.R-cluster analysis showed that there was a close relationship among the start date of flowering,the end date of flowering,the date of maturation and the days of life history;there was a close relationship among the plant height,length of main inflorescence,number of siliques in main inflorescence and the effective branch height;there was a close relationship between the grain and the biomass yield of a single plant;the relationships between other phenotypes were far.Six principal components can account for 74.5% of variance contribution.The first principal component includes plant height,effective branch height,the start date of flowering,days of life history,length of main inflorescence,the date of maturation and the end date of flowering.The results of grey correlation analysis showed that the phenotypes with high correlation degree with plot yield were yield of single plant,plant height,biomass of single plant,Number of siliques in main inflorescence,branch height and harvest index,which were basically consistent with the results of simple correlation analysis.A number of germplasm with good comprehensive characters and specific phenotype were picked out for breeding.