Phenotypic Analysis Of A Rice Virescent Mutant V13and Fine Mapping Of The Gene Causing Mutation

Mutants of leaf colour in rice are very common, and the first report on them came out in1980s. Researchers focus on the mutants of leaf colour in rice because this type of mutants is easy to distinguish from the wild type and has close relationship with photosystem. The pathway of chlorophyll biosynthesis and decomposition is complicated, and the mutants of leaf colour are suitable material for the research in photosystem of plants, the development of chloroplast and chlorophyll biosynthesis. In additional, the rice mutants of leaf colour can be used as marker in utilizing rice heterosis.In this research, we identified a new virescent mutant from Indica variety9311and designated it as "v13". The morphological characters, agricultural traits, physiological characteristics, the temperature sensitivity and the chloroplast ultrastructure of this virescent mutant were studied. Genetic action of the virescent character was analyzed by using the F1, F2and F2:3progenies from v13crossed with green original parent DJY, a normal leaf color japonica variety. Furthermore, the gene causing mutation was mapped with molecular markers. The results are as follows:1. The virescent mutant showed albino phenotype in seedling stage in the field. It became virescent after20days after seeding and turn green as normal50days after seeding while the phenotype is near the wild type. And then there was little difference between the mutant and the wild type. The agricultural traits such as the plant height, the panicle length, the tillers number and the seed setting rate, etc. were nearly the same.2. By growing the virescent mutant plants in different temperature, we found that the mutant showed albino phenotype in low temperature(23℃) but normal in high temperature(30℃).3. The inner structure of chloroplast of the virescent mutant in low temperature had obvious difference from the wild type in the seeding stage under the transmission electron microscope. The structure of the chloroplast of the mutant was very loose. The granas and grana lemmas were less than the wild type. In most cells can they hardly be seen.4. The population of v13crossed with a normal green japonica variety DJY was used in genetic analysis. The result showed that leaf color of F1progenies represented normal green, and segregation ratio of normal green to virescent fitted the expected ratio of3:1in F2:3population, suggesting that the virescent trait of v13was controlled by one pair of recessive nuclear gene.5.The F2population of v13/DJY was used as the preliminary mapping population. The preliminary mapping of v13using10recessive plants from F2progeny showed that it was located at the short arm of chomosome3, at the bottom. The gene was further restricted between L9and SS9at an interval of43kb on physical map by using a larger population.6. The gene analysis and prediction software GFSelector was used for gene prediction in the target region. We got ten candidate ORFs and two of them are temperature sensitive.