Analysis Of Diversity And Establishment Of The Core Collection Of Improved Rice Varieties In China

Four isozymes including esterase (EST), malatedehydraogenase(Mal), phosphoglucose isomerase (Pgi) and aminiopeptidase (Amp) were used to analyze 462 rice improved varieties. 12 isozyme loci and 34 alleles were detected. The number of alleles of Indica were equal with that of Japonica. Genetic diversity was analyzed in different criteria of classification. Results showed that the genetic diversity index of Indica was higher than that of Japonica . Of the six rice zones the genetic diversity index of Central China rice region (II) was the highest. The genetic diversity indexes of Shannxi, Henan and Sichuan were the three highest in 26 administrative provinces. From 1950s to 1990s the genetic diversity index of decades is ascending somewhat at isozyme level.Thirty six SSR (simple sequence repeats) loci distributed at 12 chromosomes evenly were used to analyze 520 rice improved varieties. The coefficent of genetic differentiation for Indica and Japonica was between 0.0177 and 0.5799 and the average coefficent was 0.1850. One hundred and thirty-five alleles which were found only in Indica or Japonica were detected. The average molecular weight of Indica is higher than that of Japonica at 36 SSR loci. Of the six rice zones the genetic diversity index of Central China rice zone was the highest. The genetic diversity indexes of Henan, Jiangxi and Anhui were the three highest in 26 administrative provinces. The genetic diversity index of the 1970s is the highest in the five decades and after 1970s the genetic diversity index descended. The parameters such as ratio of phenotypic retained, ratio of alleles retained,genetic diversity index, coefficient of variation, ratio of maximum and minimum of each sampling ratio of the four sampling strategies,ie cluster by phenotype character,SSR,phenotype character and SSR, and random sampling were compared. Results showed the sampling strategy of cluster by SSR and phenotype character is better than other three strategies. At last we select 338 materials clustered by SSR and phenotype character as the core collection of Chinese rice improved varieties, the core collection retained 0.9928 phenotype character and 0.9752 alleles of primary materials. It was predicted that the core collection retained 98.36% phenotype and 85.40% alleles of 4085 original materials.