Genetic Analysis And Gene Mapping Of Yellow-Green Leaf Mutant 505ys And Degenerated Panicle Mutant 6642 In Rice

Leaf color mutant was a familiar mutant type in nature. which attracted much attention for a long time. Chlorophyll is the main pigment involved in photosynthesis in the chloroplasts of green plants. Leaf color will be changed if the genes associated with chlorophyll metabolic pathways were mutated or chloroplast development was not complete, therefore, the rice leaf color mutant can be used as an important test material to study the chlorophyll synthesis and degradation pathways, chloroplast morphology and development, photosynthetic mechanism, and plant growth characteristics. In addition, the leaf color mutants can be used as color markers in hybrid rice breeding because of the leaf color can be distinguished clearly and easily, thus they have great value in breeding.Meanwhile, as a model plant of monocots. rice is an important material to research the panicle development. Making a depth research in the morphogenesis and development process of young panicle in rice maybe not only conducive to reveal the development mechanism of panicle, but also can improve rice yield.In this study, we had obtained a yellow-green leaf mutant 505ys and a panicle degradation mutants 6642 based on chemical mutagenesis (EMS) of the japonica rice variety Nipponbare. furthermore we had made the genetic analysis, phenotypic observation and measurement, and gene mapping of 505ys and 6642, which would be beneficial to gene cloning and rice breeding.The main results were as following:1. Based on the phenotype observation and main agronomic traits investigation, we found that the 505ys mutant exhibited yellow-green leaf phenotype throughout the growth period. Compared with the wild-type parent, the plant height, panicle length and grains per panicle were increased 9.80%,17.95% and 23.75% in 505ys,but number of productive panicles per plant and 1000-grain weight reduced by 21.32% and 3.15% in 505ys, respectively, at the maturity. Compared the chlorophyll content of 505ys and Nipponbare in seedling stage and booting stages, the chlorophyll a content was 2.19 mg.g-1 and 1.14 mg.g-1 in 505ys, and decreased by 25.66% and 44.45%, respectively. Chlorophyll b content was 0.72 mg.g-1 and 0.40 mg.g-1, and decreased by 32.11% and 48.26%, respectively. By the transmission electron microscopy analysis of 505ys and Nipponbare in seedling stage. we found that the mesophyll cell of the 505ys was regular, but there were many starch granules accumulated in the internal structure. Genetic analysis suggested that the yellow-green leaf trait of the 505ys mutant was controlled by one pair of recessive nuclear genes. Genetic mapping of the mutant gene was performed using F2 population of 505ys/Minghui 63 with SSR and InDel markers. The data suggested that the 505ys mutant gene was located in a region between InDel markers W2 and W3 on the long arm of rice chromosome 2, with genetic distances of 0.42 cM and 1.38 cM, respectively, and with physical distance of approximately 410kb, where 53 genes were predicted, and there was no leaf color mutant gene cloned, thus this gene is considered to be a novel gene for yellow-green leaf trait in rice, and designated tentatively as 505ys(t).2. By observation of the phenotype of the degenerated panicle mutants 6642, there was no significant difference between the mutant and wild type Nipponbare before heading. But the mutants only had a few primary branches. its secondary branches and spikelets were degenerated severely. After heading, the mutant plants almost cannot produce seed, and only a few of panicles has very few several seeds. Genetic analysis suggested that the degenerated panicle trait of the 6642 mutant was controlled by one pair of recessive nuclear genes. Because the mutants basically cannot produce seed, we used the hybrids for reproduction. Genetic mapping of the mutant gene was performed using F2 population of the 6642 hybrids/Gang46 with SSR and InDel markers. The data suggested that the 6642 mutant gene was located in a region between InDel markers 243-0 and 243-7 on the long arm of chromosome 6, with genetic distances of 0.38 cM and 0.67 cM, respectively, and with physical distance of approximately 70kb, where 10 genes weres predicted. By gene function analysis, This gene is considered to be a novel gene associated with panicle development, and designated tentatively as 6642 (t).