Physiological Characters and Gene Mapping of a Yellow Leaf and Early-senescence Mutant osyes1 in Rice

【Objective】Leaf is a main photosynthetic organ and its color mutants of rice are ideal materials for the study of photosynthesis, chlorophyll biosynthesis and metabolism, and chloroplast development in plants. 【Method】The mutant osyes1 (Oryza sativa yellow-leaf and early senescence 1) was obtained through 60Co γ-radiation treatment of indica cultivar Zixuan 1. The seedlings of osyes1 and its wild type were treated with exogenous H2O2. The SOD and CAT activities, ROS level, MDA content, soluble protein contents, chlorophyll contents, the net photosynthetic rate and chloroplast ultrastructure were analyzed for osyes1 and its wild type leaves at heading stage. The main agronomic traits of osyes1 and its wild type plants were analyzed under field conditions at maturation stage in Hangzhou. The recessive individuals in F2 population derived from osyes1/02428 were used to locate the gene by the map cloning method.【Results】The yellow-leaf and early-senescence symptoms started at 3- or 4-leaf stage, and gradually spread to all of the leaves after heading. Due to the early-senescence of the leaves of the mutant osyes1, its major agronomic traits including plant height, panicle length, grain number per panicle and the seed setting rate were markedly reduced. Moreover, the mutant osyes1 exhibited hyper-sensitivity to exogenous H2O2. The physiological analysis indicated that the contents of chlorophyll and the activities POD and CAT in the third-top leaf was significantly lower than those in the flag leaf and the second-top leaf in wild-type (WT) plants, but all of them in the mutant plants were significantly lower than those in its WT. Compared with the WT plants, the contents of MDA, H2O2 and O2? followed a steady increasing trend in the flag, second-top and third-top leaves of the mutant, while their soluble protein levels were progressively dropping. Genetic analysis confirmed that osyes1 was controlled by a single recessive nuclear gene, which was mapped to a region of 708 kb flanked by two SSR markers (RM21353 and RM21384) on the short arm of chromosome 7. 【Conclusion】In this work, the main agricultural traits were significantly reduced in osyes1 for the yellow leaf and early senescence. OsYES1 was located in a 708 kb range between RM21353 and RM21384 by map-based cloning strategy.