Molecular Detection of Rice Blast Resistance Genes in Major Varieties of Rice in Jilin Province

[ Objective] This study aimed to detect flee blast resistance genes in major varieties of rice in Jilin Province. [ Method ] Ten molecular markers closely linked with rice blast resistance genes were used for molecular identification of resistance genes in 24 rice varieties from Jilin Province. [ Result] The 24 major vari- eties of rice widely lacked in rice blast resistance genes Pib, Pil, Pikh and Pia; Pi9 gene was absent in 17 of the 24 major varieties, especially in Jijing 88 and Changbai 9 which occupied the largest cultivation area in Jilin Province ; in addition, Jijing 88 harbored five rice blast resistance genes, including Pita, Pikm, Pt2, P/-d2 and P/z. [ Conclusion] Pib, Pil, Pikh, Pia and Pi9 are the major resistance genes for improving flee blast resistance of major varieties of rice in Jilin Prov- ince.

A Comparative Study of SSR Diversity in Chinese Major Rice Varieties Planted in 1950s and in the Recent Ten Years(1995-2004)

Forty pairs of SSR markers were used to compare the genetic diversity changes in 151 Chinese major rice varieties planted in 1950s and in the recent ten years. Of 40 SSR loci, 39 were found to be polymorphic while one locus （RM479） monomorphic. A total of 213 alleles were identified from the 39 polymorphic loci. The average number of alleles per locus （Na） was of 5.5, ranging from 2 to 11. Nei＇s gene diversity index （He） varied drastically among loci from 0.309 at RM174 to 0.869 at RM418, with an average value of 0.649. There existed significant difference in SSR allelic diversity between indica and japonica subspecies, and indica had more variation than japonica both in Na and He. By comparison with the genetic changes in Na and He, it was revealed that the varieties planted in 1950s had more alleles and higher He than those in the recent ten years both for indica and japonica rices. The difference between two subspecies for Na was significant in a tendency over time （indica： z = 2.677, P = 0.007; japonica： z = 3.441, P = 0.001）, but not significant for He （indica： z = 1.471, P = 0.141; japonica： z = 1.932, P = 0.053）. Analysis of molecular variance （AMOVA） indicated that there existed significant difference （P 〈 0.05） in genetic variation between the two periods, of which more genetic variation was contributed by indica （Fst= 0.050） and japonica （Fst= 0.082） subsets. Using locus-by-locus AMOVA procedure, significant genetic differentiations were observed in 13 loci （RM21, RM128, RM147, RM169, RM190, RM221, RM231, RM251, RM253, RM317, RM341, RM418, and RM478） for indica varieties and 11 loci （RM101, RM135, RM152, RM159, RM169, RM190, RM251, RM253, RM311, RM418, and RM478） for japonica ones between the two periods. It was found some alleles had been lost in current major rice varieties as comparing with those in 1950s. Therefore, it should be necessary to exploit more alien elite genetic resources for extension of genetic background in current rice breeding program.

Temporal changes in SSR allelic diversity of major rice cultivars in China

Forty simple sequence repeats （SSRs） were used to assess the changes of diversity in 310 major Chinese rice cultivars grown during the 1950s-1990s. Of the 40 SSR loci, 39 were polymorphic. A total of 221 alleles were detected with an average of 5.7 alleles per locus （Na）. The Nei＇s genetic diversity index （He） varied drastically among the loci （0.207 to 0.874, mean 0.625）. Comparing the temporal changes in Na and He, the cultivars from the 1950s had more alleles and higher He scores than the cultivars from the other four decades. Analysis of molecular variance （AMOVA） indicated that the genetic differentiation among the five decades was not significant in the whole set, but significant within indica and japonica. More changes among the decades were revealed in indica cultivars than in japonica cultivars. Some alleles had been lost in current rice cultivars in the 1990s, occurring more frequently in indica. These results suggest that more elite alien genetic resources should be explored to widen the genetic backgrounds of rice cultivars currently grown in China.