Characterization And Gene Mapping Of A New Pale Green Leaf Mutant Hm14in Rice (Oryza Sativa L.)

Pale green leaves are common mutations in plant kingdom. It appears in all growth periods while more often in the seedling stage. Many pale-leaf mutants are ideal and important sources for plant breeding and for understanding the mechanisms for plant photosynthetic organ development and photosynthesis. The genetic controls of about90pale-leaf mutants in rice have been characterized and11leaf color genes have been isolated as well."Not only in rice, but also in other plants have pale-leaf mutants, like Arabidopsis, corn, tomato, and barley and so on. This thesis reviews comprehensively on recent research progress of pale green leaves mutants, and studies on agronomic traits, chlorophyll content, chloroplast development, photosynthetic index, and genetic control of a rice pale-leaf mutant HM14. The main results are as follows:Agronomic traits:Pale green leaf mutant HM14, whether planting in the field in Hangzhou or in Hainan, it can inherit stablely. Pale green leaf trait appears at the seedling stage and lasts through the whole life. Among the agronomic traits observed, plant height of HM14is significantly lower than that of IR64, but no significant differences in other agronomic traits are observed.Chlorophyll content:In tillering period, the contents of chlorophyll a and chlorophyll b of IR64and HM14are highly significant, but no difference in carotenoid content; In heading period, the content of chlorophyll a of IR64and HM14are significantly different. The content of chlorophyll b and carotenoid are significantly different; In maturing stage, the content of chlorophyll a and chlorophyll b are significantly different but no difference in carotenoid content; In filling stage, the content of chlorophyll a of IR64and HM14are significantly different. In summary, the contents of Chlorophyll a of HM14in the first three growth stages are significantly different from those of wild type IR64, But the contents of chlorophyll b are similar between the IR64and HM14. The content of carotenoid varies in the whole growth period.Photosynthetic organ development:the development of chloroplasts in seedling stage, tillering period and grain filling during are observed. In seedling stage, the mutant chloroplast thylakoid developed abnormalities; In tillering stage, the mutant grana lamellae arranged loosely, the distance between the layers is larger, the arrangement of the lamellar structure as a whole is not unified while thylakoid body stamp stack is still small; In the filling stage, the mutant thylakoid membrane grana stack shows increased number of grana that are arranged more regularly than that in seedling and tillering stages.Photosynthetic indexs:Comparing with photosynthetic rate, stomatal conductance and transpiration rate of three photo synthetic factors of IR64, photosynthetic rate, stomatal conductance and transpiration rate of mutant HM14in flag leaf and the last second leaf are significantly different from the wild type.Genetic control of the pale-leaf trait:Genetic analysis of F1, F2and F3generations derived from the crosses HM14/Morobereken and HM14/reyanl indicate that F1plants of two combinations were all normal in green leaf. Segregation occurred in F2populations with wild-type and mutant at a ratio of3:1. The same segregation ratios were confirmed in4segregation lines in F3derived from the two populations. These results suggested that the mutant HM14was controlled by a single recessive nuclear gene, tentatively named pale green leaf4(pgl4).Fine mapping of pg14. Using F2individuals derived from the crosses of HM14/Morobereken (1008mutant type plants) for gene mapping. Firstly, three SSR markers RM7203. RM167and RM26113from chromosome11showing polymorphism in the bulked segregant analysis were found linked to the gene. Then using new SSR, InDel and STS markers, pg14was finally located on the short arm of chromosome11between the two markers, RM26076and RM26079.The physical distances between RM26076and RM26079was39.7kb. No similar genes have been reported in the region, thus pg14is likely a new pale green gene. Bio informatics analysis shows, the interval is covered by two BAC clones containing seven candidate genes including cpSRP54. Candidate gene validation is in progress.