Genetic Analysis And Mapping Of A Senescence Mutant Psl2 In Rice

Heterosis has been successfully used in hybrid rice for many years. There are many crosses of hybrid rice displaying premature senescence phenomenon on the leaves during late growth stage. It leads to the high rate of empty husks and affects yield potentiality of hybrid rice. In order to clarify the mechanism and regulation of early senescence, we studyed the phenotypes of a senescence mutant (psl2) by aeronautics in rice, and also used a map-based cloning strategy to locate psl2 gene.The results were as follows:â‘ The investigation of premature senescence symptom and agronomic characters of the psl2 mutantAbout 30 days after transplanting, psl2 mutant began to appear senescent symptom. From that time on, a new leaf came out, then the top fourth leaf began to turn yellow, the performance of each leaf was similar. At the beginning of heading date, the top third leaf started to turn yellow. At the late stage of heading, the top second leaf started to senesce. Until the late filling stage, the flag leaf came into senescing. In yellow ripeness stage, all the leaves dried out. The average longevity of a leaf was about 15-20d in the psl2 mutant, while the wild-type varieties Luhui 103 could maintain 25-30 d under the same conditions. Each single leaf aged from the sheath. The status of the agronomy showed that, compared to the wild-type varieties Luhui 103,the spike length of psl2 mutant became shorter, the grain weight decreased, while height and grains per spike was significantly reduced and yield markedly declined.â‘¡Genetic analysis and Mapping of psl2 mutantIn order to determine the inheritance mode of the mutation, we made a cross between the psl2 and R527. All the F1 plants displayed wild-type phenotype, while the F2 progenies segregated in a ratio of 3:1(normal leaf : premature senescence leaf),indicating that a single recessive nuclear gene controls the mutant phenotype. Using 537 SSR markers which distributed on the 12 chromosomes of rice, the psl2 gene was initially located on the chromosome 3, linked with markers RM251 and RM282 .Further searching for primers, the objective gene was flanked by markers RM14704 and RM14710 at 0.1155cM and 0.1540cM intervals, respectively, with the corresponding distance of 370kb.Gen prediction indicated that there were 55 candidate genes.