The Genetic Analysis And Gene Targeting Of A New Yellow-Green Leaf Mutant In Rice

Chlorophyll is an important pigment involved in photosynthesis in plant chloroplasts, and it’s the main component of the photosynthetic pigments universally exist in photosynthetic organisms. The blade is the most main photosynthesis organ of plant, the normal leaf mainly contains chlorophyll and usually it appears as green. Variation of leaf color is a mutant character with higher mutation frequency and easy to identify in the higher plants. The leaf color mutant often used as marker traits of crops, and it is an ideal material in the research of plant photosynthesis mechanism, the biosynthetic pathway of chlorophyll, chloroplast structure and function, and regulation mechanism of genetic development. Rice (Oryza sativa) is not only the one of the world’s most important food crops, but also the model crop studying plant functional genomics. The more common type of a mutant in the rice is leaf color mutant, it has irreplaceable value in rice functional genomics research, physiological and biochemical mechanisms in plant photosynthesis, and genetic breeding applications.In this study, a yellow green mutant "yg151" was isolated from the chemical mutagenesis in rice japonica rice variety Nipponbare. The morphological characteristics, the main agronomic traits, physiological characteristics of the mutant throughout the growth period were observed and analyzed, and had genetic analysis with the F1generation of yg1511Nipponbare and yg1511Minghui63, while taking advantage of the F2generation of yg1511Minghui63as a mapping population of the mutation gene carried out the initial positioning of the microsatellite markers, and then had it’s fine mapping through the InDel markers. The results are as follows:1.Phenotypic characteristics and agronomic traits of the mutant yg151:Under natural conditions in Wengjiang, Sichuan, the mutant leaf color exhibit yellow-green from seedlings, until heading、harvest and so on the entire growth period of the whole plants have shown the yellow trait. The number of tillers per plant, Plant height, spike length, the length and width of flag leaf, the grains per panicle, grain setting rate1000-grain weight and other major agronomic characters were investigated at maturity stage, and found that the mutant’s number of tillers per plant decreased by8.8, plant height decreased by7.5%, the flag leaf’s length and width increased by1.4%, panicle length decreased by4.7%, the grains had10.8%reduction in per panicle,1000-grain weight decreased by10.5%, seed setting rate was reduced by42.8%especially, the change was very significant.2.The contents of chlorophyll and carotenoid of the mutant yg151:content of photo synthetic pigments of yg151decreased significantly at seedling stage and booting stage, compared with Nipponbare, The chlorophyll content of yg151decreased by66.6%at seeding stage, and decreased by27.6%at booting stage. The carotenoid content decreased by51.3%at seeding stage,24.8%at booting stage. The chlorophyll a and chlorophyll b contents decreased by63.0%、80.0%at seeding stage and23.7%、43.3%at booting stage, respectively. This showed that the mutant pigment synthesis was blocked.3. The genetic analysis of yg151mutation:The genetic analysis of crosses ygl51mutants were prepared with two normal green rice lines (japonica variety Nipponbare and indica variety Minghui63) showed that:F1generations were all normal green, and the F2generations could be classified into normal green and yellow-green two groups. The chi-square (χ2) test, the segregation ratio of green seedlings with yellow-green seedlings are in line with expectations3:1. These results indicated that the yellow-green leaf mutation characteristic was controlled by one pair of recessive nuclear gene.4.The fine mapping of the mutant gene of yg151:F2generations from the hybrid combinations of Mutant yg151and Minghui63as the mapping population, and use of the350SSR markers distributed in12chromosomes for initial positioning, we found that the mutant gene was linked with the SSR primers located on the long arm of chr.3, i.e. RM55, RM186, RM168, and their genetic distance were7.20cM,5.83cM,3.23cM respectively. To encrypt the positioning interval we use of the rice genome data to developed InDel markers in the RM168marker’s upstream region,and had linkage analysis with the application of the MAPMARKER software and the partial molecular linkage map of the yellow green leaf mutant gene of yg151was constructed, ultimately the gene is located on the InDel markers Ch3,-274-2and Ch3,-272-1, the genetic distances both were0.31cM and the physical distance was120kb. Infer that the gene is a new mutated gene of yellow green leaves,so,it was named as yg151(t) temporarily.