Abstract: 【Objective】Phenotypic and physiological characteristics of an environmentally induced rolled leaf mutant were studied in present paper. Meanwhile, the mutant gene was preliminarily mapped on rice chromosome. 【Method】A rolled leaf mutant, named rl15 (t) (rolled leaf 15), was obtained by 60Coγ-ray mutagenesis from japonica cv. Nipponbare. By field identification, the phenotypes and main agronomic traits of the mutant were investigated. Different temperature and relative humidity treatments could reveal the environment factors that affect leaves rolling in mutant. Both of rl15(t) and wild type at heading stage were divided into 6 groups and were treated with temperature at 24℃, 29℃ and 34℃, and relative humidity at 60% and 95%. After treatment for 1.5 h, flag leaves were used to measure leaf rolling index (LRI). From 6:00 AM to 18:00 PM, the photosynthesis rate (Pn), transpiration rate (Tr), stamatal conductance (Gs) of flag leaves in rl15(t) and wild type were measured at 2-hour intervals by using the portable gas exchange system Li-6400, meanwhile, leaf water potential was measured by WP4 dewpoint potential meter. These physiological characteristics were analyzed and compared between rl15(t) and wild type. The rl15(t) mutant was crossed with the wild type Nipponbare, leaf phenotype of the F1 progeny and segregation ratio of flat leaf plants and rolled leaf plants in F2 population were investigated. On the basis of BSA method according to Michelmore et al., preliminarily mapping of the candidate mutant gene were conducted using a F2 population derived from rl15(t) crossed with indica line Zhenshan97B.【Result】Compared with the wild type, the mutant plants have shortened plant height, reduced tiller numbers, shorter panicle, smaller grains, delayed heading duration, shorter and narrowed leaves. All of the leaves in rl15(t) were observed to highly inward roll at midday hours under sunny conditions, whereas were flat or slightly inward rolled under rainy conditions or at early morning and sunset under sunny conditions. Experiments of different temperature and relative humidity treatments showed that leaf rolling index in rl15(t) mutant were mainly depended on air humidity and could be promoted by high temperature. The photosynthesis rate, transpiration rate, stamatal conductance and leaf water potential of flag leaves in mutant were extremely lower than those in the wild type at midday hours under sunny conditions. However, the instantaneous water use efficiency (WUE) was similar to that of wild type at 6:00, 12:00, 18:00 o’clock, whereas in other time of a day, WUE was dramatically higher than that of the wild type. F1 plants derived from crossing rl15(t) with wild Nipponbare showed normal flat leaves, The segregation ratio of flat leaf plants to rolled leaf plants in F2 population was consistent with the inheritance of single recessive nuclear locus. Further molecular genetics studies revealed that RL15(t) was mapped on the long arm of rice chromosome 10 between SSR markers RM25302 and RM25343, with genetic distances of 0.8 cM and 2.0 cM, respectively. 【Conclusion】Mutant rl15 (t) was environmentally induced rolled leaf in phenotype. RL15(t) gene is located between SSR markers RM25302 and RM25343. In these distance segment, it hasn’t any similar phenotype genes reported up to now. So, RL15(t) gene would be a putative novel rolled leaf gene.

Key words: rice (Oryza sativa L.) , rolled leaf traits , physiological characteristics , molecular mapping , environmental induction