Genetic Analysis And Gene Mapping Of A Withered Leaf-tip Mutant In Rice (Oryza Sativa L.)

Leaf is an important organ for photosynthesis and respiration in plants, and plays a key role in its life activity. Also leaf development is important for plant-types and grain production. Leaf senescence in rice can lead to reduction of photosynthesis power, and gradual loss of assimilation ability. Then it affects the formation and accumulation of organic compounds in the later stage of rice growth, and the formation of production. So leaf senescence is one of the limiting factors in identification and utilization of rice high-yield potential.A withered leaf-tip1 (wlt1) mutant of rice (Oryza sativa L.) by mutagenesis of ethylene methylsulfonate (EMS) treatment from Nipponbare was identified and used in this study. The mutant exhibited phenotypes of leaf scorch and withered leaf tip, and heavier leaf scorch and emergence of upper-node tillers during later growth stage. In this study, we use the wlt1 mutant to conduct some research on physiologic characters, genetic analysis and gene mapping. They are beneficial to dissection of melocular machenism of leaf senescence and upper-node tillers in rice.To analyze whether wlt1 was controlled by a single gene, genetic analysis with reciprocal crosses between wlt1 and an indica cultivars TN1 or ZF802 was conducted and revealed that wlt1 possesse a recessive mutation. Based on their F2 segregation individuals derived from the crosses, the ratio of mutant phenotype: wild type was 1:3 (χ2c<χ20.05=3.84), confirming that the wlt1 phenotype was controlled by a single recessive gene. Allelic tests between wlt1and another mutant wlt2 showed that they are different genes. Cytology observation of wlt1 in later growth stage indicated that the vascular bundle size in the mutant is smaller than that of the wild-type. Chlorophyll content detection of functional leaves between wlt1 and the wild-type during tillering stage showed the reduction of the total chlorophyll content in wlt1 which mainly results from the reduction of Chl a.Using 142 F2 mutant individuals from the cross between wlt1 and TN1, the WLT1 gene was primarily mapped to the region of the long arm of chromosome 10 between the two markers STS1 (6.69 cM) and SSR3 (2.11 cM). Fine-mapping delimited it to a 21.3 kb physical distance, where 5 open reading frames were predicted. We are just sequencing for these genes.