The Platform of Polymorphic Markers and Genetic Mapping of a Drought Tolerance Gene at Seedling Stage in Rice

• Main Authors: Jen-Hao Hsu, 徐仁浩
• Other Authors: Chieh-Wei Kuo
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/75540753777878350642

碩士 === 國立嘉義大學 === 農藝學系研究所 === 100 === In this study, we surveyed polymorphic DNA fragments among 5 common indica and japonica varieties from Taiwan and one indica variety from Mainland China to establish the platform of high-density polymorphic markers in rice for the application to variety identification, linkage mapping of gene (s), and phylogenetic analysis. We implemented the large mined polymorphic markers above to do coarse and fine mapping of drought gene (s) by using progeny of japonica CNY922301 crossed with a drought tolerant variety, indica Hang-Yu 15. PCR-based markers, SSR (simple sequence repeats), indel (insertion and deletion), and STS (sequence tagged site), were applied to survey polymorphism among inter- or intra- subspecies. A total of 1167 markers, covered a total length of 1525.8 cM on 12 chromosomes with an average of 1.31 cM, were selected. A total of 736 (63%) markers exhibited polymorphism among 6 varieties, included 6 intra-subspieces specific polymorphism markers. Out of them, 730 polymorphic markers were uncovered between indica and japonica subspecies, with an average of 2.09 cM, which is relative dense and sufficient for linkage analysis of genes segregating in populations derived from indica/japonica crosses. The average distance of polymorphic markers among indica varieties was 4.8 cM, which was larger than those of among 6 varieties and between two subspecies, indicating the genetic diversity of indica was narrow resulting to uncover less polymorphic markers. The average distance of polymorphic markers among japonica varieties was 13.27 cM, indicating the genetic relationship of japonica varieties was very close. The genetic diversity of japonica varieties was relative narrow, leading to polymorphic markers no evenly distributed, for which there were insufficient polymorphic markers at some chromosome segments. For genetic linkage analyses, the polymorphic marker density was high enough for indica/indica crosses but insufficient for japonica/japonica crosses. More polymorphic markers are underwent mining to increase the density of polymorphic markers. We used the high-density polymorphic markers uncovered above for mapping rice drought gene (s) during the seedling stage of rice. The F2 and F3 populations of japonica CNY922301 crossed with indica Hang-Yui a drought tolerant variety. The progenies were evaluated for drought tolerance by using 28% of PEG-6000 solution, which was used to mimic drought, at 3-leaf seedling stage. The ratio was 9: 7 for drought tolerant : sensitive F2 individuals, indicated the drought tolerance of Hang-Yui 15 might be inherited by two complementary dominant genes. By using the F2 population, these two genes were coarsely mapped on chromosome 12 and linked with RM277 (62.2-64.4 cM), and RM6693 (91.9-94.6 cM), named with DTS and DTL, respectively. After fine mapping of the drought tolerant gene DTL by using the F2 and F3 populations, the gene was located between RI12007 and CH1207, in a region of 365 kb. An F3 population generated by SSD were used for mapping DTL, and we confirmed the drought tolerant gene might be linked with five markers, RM6693, RM235, RI12007, CH1207, and E60843 (91.9-94.6 cM). The information paves ways for positional cloning of DTL and marker-assisted selection of drought tolerance by using these five linked markers for foreground selection, which promotes the efficiency of breeding new drought tolerant varieties in Taiwan and abroad.