| Genetic diversity of isozyme variation in rice was investigated based on 12 polymorphic isozyme loci (Pgil, Pgi2, Ampl, Ampl, Amp3, Amp4, Sdhl, Adhl, Est2, Est1, EstS, Est9) using a sample of 6099 accessions of Chinese traditional varieties by starch gel-electrophoresis. A set of 54 rice SSR markers was used for 94 rice cultivars bred in 1930s to 1990s in China to estimate genetic diversity in DNA level.1. The genetic diversity of isozyme in the 6099 Chinese traditional varieties was high (H=0.27 with 4.33 alleles per locus), as compared with most selfing plant species. There were 52 alleles found from the tested materials, which covered 96.3%of total 54 alleles having been found from world's rice germplasm. Allele frequencies ranged from 0.0002 to 0.9903. The average gene diversity index (Ht), genotype frequency (F), and degree of polymorphism(DP) were 0.2702, 0.0974 and 0.1985 respectively. There are 22 genes with gene frequency less than 0.01, 5 genes in 0.001-0.005, 18 genes in 0.051-0.90 and 5 genes higher than 0.90. It was found that allele Pgil-5 was only identified from Chinese rice cultivars. The results revealed Chinese rice germplasm had high genetic diversity in terms ofisozymes.2. The index of average gene diversity (Ht)in the tested indica varieties is 0.2286, being higher than that of japonica (Ht=0.1773). The Gst indexes were low for most of 12 loci between two rice subspecies. The index of genotype frequency in indica is 0.1053, while that in japonica is 0.0857. The observation that indica and japonica subspecies consisted of distinct multilocus phenotypes, suggested that the origin of the indica and japonica rice was parallel.In six Chinese rice eco-regions, the cultivars in Southwest region had hightest average gene diversity (Ht=0.294), followed by that is South (Ht=0.2680) and Central one (Ht=0.2340), Northeast China had the lowest value. On the other hand the cultivars in the Central region showed highest average allele number of 4. It was found that allele Pgi\-5 only identified from Chinese 5 rice cultivars. Comparing the value of isozyme diversity between 29 provinces, the indexes of average gene diverisity (Ht) in the followed provinces were higher: Hainan(0.3724), Yunnan(0.3190), Hubei(0.2884), Guangxi(0.2625), Guizhou(0.2550), Hunan(0.2508), Henan(0.2471), Taiwan(0.2457), Jiangsu(0.2242), Jiangxi(0.2144), Anhui(0.214), Fujian(0.2118). The result indicated that the provinces with higher average gene diversity in rice were located in: Yunnan and Guizhou plateau; themiddle and low area of Yangzi River; South China and Henan province.4. Classification analysis indicated that all 6099 cultivars could be clustered into two groups, one was indica and the other japonica. For each group, it can be divided into two subgroups e.g. typical indica (major subgroup) and second indica (minor subgroup); typical japonica(ma)or one) and second japonica (minor one). 99.75% of the total accessions were belong to the two major subgroups, while a few varieties(0.25%) were belong to two minor groups.5. The 94 modern rice varieties used for microsattelite were bred in 30's-90's and grown in China widely. A total of 311 alleles were detected at 58 loci using the 54 rice SSR primer pairs ( 4 primers amplified 2 loci; all other primers amplified 1 locus each) from the tested genotypes. The number of alleles per locus ranged from 2 to 17, with an average of 5.36 alleles per locus. The values of average polymorphic information content (PIC) was estimated to be 0.647 with a range from 0.452-0.833. The genetic similarity (GS) coefficient for all possible 8836 pairs of genotypes ranged from 0.009 to 0.845 with an average of 0.259. The dendrogram, prepared on the basis of similarity matrix using the UPGMA algorithm, delineated the aboye genotypes into two major clusters, which were matched well to indica and japonica types identified by agronomic trails. It also indicated that the diversity within species was higher than that within subspecies. The indica group showed higher average genetic diver... |
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