Genetic Analysis And QTL Mapping For Rolled Leaf In Rice (Oryza Sativa L.)

Rice rolled leaf is an important morphological character in plant type. Many high yield rice varieties or hybrids showed rolled leaf, such as LiangyouE32. A series of studies on effects of rolled leaf on photosynthetic physiology and ecological effects and economic traits showed that, rolled leaf exhibited some outstanding effects. For instance, making leaf erect, optimizing canopy light transmission, increasing effective leaf area, improving the quality of population in rice late-growing stage.Up to now, numerous rolled leaf rice have been found. However, rolled leaf in rice appeared to be a complex trait since many cultivars showed different leaf rolling type and degree. Some of them rolled slightly, and some rolled moderate, whereas some rolled cylindrically. Furthermore, there were few reports about molecular mapping or cloning of genes for rolled leaf. Therefore, in the present experiment, two representative varieties, GuangChaoSiMiao, a semi-rolled leaf indica variety, and another one, Ketan Nangka, a flat leaf javanica variety with wide compatibility gene were used to study. An F₂ population with 185 plants, which was derived from F₁ of Ketan Nangka/GuangChaoSiMiao, was used to analyze and gene map for rolled leaf.1 Genetic analysis for rolled leafGuangChaoSiMiao is a semi-rolled leaf indica variety, and its rolled leaf index(RLI) is 47.14ï¼…. Ketan Nangka, a javanica variety, its flag leaf is flat and RLI is denoted as 0. Flag leaf RLI of Ketan Nangka/GuangChaoSiMiao F₁ is 22.53ï¼…, and that of reciprocal F₁, GuangChaoSiMiao/Ketan Nangka is 11.93ï¼…. The result implied that rolled leaf is controlled by incomplete dominance inheritance of cell nucleus.The F₂ population derived from Ketan Nangka/GuangChaoSiMiao F₁ was genetically analyzed and QTL mapped for rolled leaf. In F₂ population, phenotype of flag leaf segregated dramatically and some over-parent rolled leaf plants were observed. There was a peak in distribution of flag leaf RLI in F₂ population. Primary genetic analysis of RLI implied that rolled leaf trait was controlled by numerous quantitative trait loci rather than one or two major genes. 2 Mapping of QTL for rolled leafA whole genome linkage genetic map containing 110 SSR markers was constructed by MAPMAKER/EXP3.0, with total length of 2051.3 cM on whole genome. Flag leaf RLI of 7 days after heading was measured and took as rolling degree, the phenotype of parents and 185 plants were analyzed. The position and effect of each locus were performed by WinQTLcart2.5 based on composite interval mapping method(CIM). QTLs for rolled leaf were detected throughout whole genome. A total of three QTLs for rolled leaf were detected on Chromosome 4 and 5. There were two QTLs on Chromosome 5 and denoted as qRL-5-9 and qRL-5-10. Their LOD score was 4.5 and 4.9 with phenotypic variation explained by 16.08ï¼…and 27.98ï¼…, respectively. Another QTL on Chromosome 4 was named qRL-4-2. Its LOD score was 2.9, phenotypic variation explained by the QTL was 7.27ï¼…. The QTL was seemed to be a newly detected QTL. The results showed that, three loci of qRL-4-2, qRL-5-9 and qRL-5-10 from GuangChaoSiMiao increased leaf rolling degree.On the basis of mapping results from the F₂ population, the present experiment confirmed that, three loci controlling leaf rolling in GuangChaoSiMiao were incomplete dominant genes. The rice rolled leaf of the present experiment was controlled by QTLs. The QTLs might be useful in rice breeding since their effects were expressed rolled leaves in rice late growing stage rather than early growing stage.The present results would facilitate to gene clone and research on the mechanism for leaf rolling. In addition, in the present paper, miRNA regulatory mechanism to rolled leaf, development and mapping methods of qualitative-quantitative major gene and QTLs, and rice resource utilization of rolled leaf were also reviewed and discussed.