Genetic Analysis And Fine Mapping Of Agronomic Traits In Longliheinuo-Dwarf (Oryza Sativa L. Ssp Japonica)

The food is an important basis for human survival. Rice is one of the most important food crops in the world. Rice production is mainly composed of panicles, grain number per panicle, grain weight and other factors. In addition, such as plant height, plant type, stem strength and number of tiller, and other agronomic traits have a critical influence on the yield in modern agriculture. Studies on the genetics, gene cloning and functional analysis of agronomic traits will facilitate for efficient breeding.In this study, we chose an indica cultivar,05-643(large grain), and a japonica cultivar Longliheinuo-Dwarf (small grain) as the parental lines, because they exhibit great variation in grain shape and plant height. The F2and BC populations were constructed from the cross between the above-mentioned parents. Traits of plant height, grain length and grain width were used for primary QTL analysis and fine-mapping. The main results are summarized as follows:First, the dwarf gene was mapped between two molecular markers, RM7293and RM18402on chromosome5with the genetic distances of6.4cM and0.3cM, respectively. Unexpectedly, there had already been a cloned gene DWARF1(D1) controlling rice height within this region. Sequence difference for Dl allele was thus analyzed between Nipponbare and Longliheinuo-dwarf. The result showed that a point mutation responsible for transition from Gâ†'A occurred at the translation starting site, resulting in the loss of start codon. Another ATG site, however, existed30bp upstream of this mutant site. Unfortunately, the Câ†'T substitution occurring in the second exon lead to a premature stop codon which could not translate the functional Ga protein. Conclusively, this gene is allelic to dl, and result in a new function-loss mutant, named d1-11. The mutant also led to other pleiotropic effects of thick stalk and leaf, dark green leaf, upright panicle, short grain, curved endosperm, and so on.Second, on account of interference of grain length, d1gene was expelled from hybrid progenies by backcross using05-643as the recurrent parent. And it was found that the grain shape in a backcross inbred line RHL2401(BC1F4) were still segregated. Using this line, qGS7, a major QTL controlling grain width and grain length in rice, was primarily mapped between the SSR markers of RM6344and RM8261on chromosome7. According to the preliminary mapping of qGS7, heterozygous individuals at the interval of RM6344and RM8261in RHL2401line were selected to construct a large population for fine-mapping, and the candidate region of QTL qGS7was finally narrowed down to a101kb interval, where fourteen ORFs was predicted, based on Nipponbare sequence.