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Flag leaf of rice is one of the most important traits determined rice yields and plant architecture, which has been studied extensively in recent years among genetics and/or molecular biology researches. In present study, a series of specific lines, near-isogenic lines with long and short flag leaves, and the qLFL1chromosome segment substitution lines, derived by backcrossing method for three years, were been obtained and investigated. Agronomic and physiological characters were analyzed on qlfl genetype and qLFL genetype NILs and their parents. Results are as follows:1. In this study, F1segregation population were chosen of Zhe04B/Zhehui815, near-isogenic lines with long and short flag leaves derived by backcrossing method for three years, they are BC3F5-SFL lines and BC3F5-LFL lines. In the same time, the BC2F2segregating population of Zhehui815X04A were selected for the gene mapping. According to statistical analysis, the site, which we named qLFL1, was finally located on rice chromosome9between SSR markers RM3700and RM7048. In order to isolated and cloned this sites, we build the qLFL1genes chromosome segment substitution lines. Molecular markers detecting individuals of long flag leaf, and then the individuals backcross with Zhe04B. Finally, we obtain the qLFL1chromosome segment substitution lines.2. Near-isogenic lines with long and short flag leaves, and the qLFL1chromosome segment substitution lines were been chosen to mapping the site. Five hundred twenty SSR molecular markers, which evenly distributed on12chromosomes in rice, were used to test88individuals with long flag leaf phenotype in BC2F2. According to statistical analysis, the qLFL1site was located on rice chromosome9between SSR markers RM3700and RM7048with a genetic distance of7.1cM. Furthermore, certain In/Del markers were developed within this region, and tested1478individuals with long flag leaf phenotype in BC3F2, BC4F2and BC5F2. The qLFL1locus was finally mapped between In/Del markers ID22and ID21with a physical distance44kb, the target region contained14candidate genes.3. Agronomic and physiological traits of coleoptile length, plant height, number of tillers, flag leaf length/width, top second leaf length/width, top third leaf length/width, panicle length, total grains number per panicle, fertile grains per panicle,100-grain weight, seed setting rate, grains weight per panicle, grain yield per plant and photosynthesis capcity were investigated. The results showed that qlfl gene have positive effects on coleoptile length, flag leaf length, top second leaf and top third leaf length; qlfl gene have no obvious negative effects on major agronomic characteristics. But qlfl gene would diminish the capcity of photosynthesis. Upon these results, it was hint that the yield potential of qlfl gene would result from the increase of leaf area. It will be benefit of exploration of qlfl gene to modificate plant type and improve yields in rice.
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