Abstract:Leaves are the main organs for photosynthesis in rice (Oryza sativa L.), and leaf morphology affects the photosynthetic efficiency of rice plants. Identification of genes that control leaf curling and revealing their genetic mechanisms, could provide genetic resources for optimizing the architecture of rice varieties with moderately curled leaves. In this study, the spontaneous rolled leaf mutant rl76 was measured on their agronomic traits, content of leaf cellulose and chlorophyll, histomorphological observation was carried out as well. In addition, the rice GSR40K chip was applied to map the mutant gene rl76. At the seedling stage, there was no significant difference between the mutant rl76 and the wild type on their leaf rolling severity, both of which showed slightly rolled leaves; through the tillering to the maturity stages, the leaves of rl76 severely rolled into shallot-like shape and erect, while the leaves of wild type were flat and slightly drooping. Comparing with wild type, the leaf rolling index of rl76 increased significantly, while the plant height and effective tiller number decreased significantly, there was no significant difference on leaf width, flag leaf length and panicle length. The chlorophyll content in leaves of rl76 was significantly higher than that of the wild type, the carotenoid content did not significantly vary; nevertheless, the content of cellulose and lignin were lower in rl76 than those in the wild type. The leaf histomophology was observed by paraffin sectioning, in the leaves of rl76 mutant, the two air cavities disappeared, the development of the sclerenchymatous cells on the abaxial surface was defective, and the area and number of the bulliform cells decreased. Genetic analysis showed that the rolled leaf was determined by a single gene inheritance pattern with incomplete dominant. By use of the rice GSR40K chip, the mutant gene rl76 was preliminarily mapped within the region of 12.179-16.436 Mb on chromosome 9. With 949 plants showing severely rolled leaf in an F2 population, the gene rl76 was further fine mapped within the chromosomal segment delimiting by the SSR markers T5904-7 and T5904-9, corresponding to a physical distance of 30.26 Kb. It contains three annotation genes within this chromosomal segment, among which the gene LOC_Os09g23200 encoding SHALLOT-LIKE 1 (SLL1) has been reported, it determines leaf curling by regulating the development of leaf distal surface cells. Therefore it is speculated that the rolled leaf in the mutant rl76 may be regulated by the gene SLL1. In summary, the rolling leaf in the rl76 mutant was resulted from abnormal development of the bulliform cells and abaxial sclerenchymatous cells that were regulated by a single incompletely dominant gene on chromosome 9.