Leaf morphology is an important agronomic trait in rice. A rolled leaf mutant was induced by Ethyl Methane Sulfonate (EMS) treatment on Koshihikari rice, a japonica type. This mutant showed phenotypes of rolled and reduced leaf width in the seedling stage, and lower seed setting rate. Plant height of the mutant was also reduced as compared with wild type due to the insufficient elongation of the second and the third internode. Microscopic analysis revealed that the size of adaxial bulliform cells were reduced and the number of small veins was decreased in mutant leaves.
To seek out the reason of lower seed setting rate in rolled leaf mutant, pollen fertility test was performed and the mutant showed irregular shaped and yellowish pollens regarded as sterile one.
Genetic analysis of F2 segregation population derived from the cross between the rolled leaf mutant (Oryza sativa ssp. japonica) and Milyang23 (O. sativa ssp. indica) indicated that the rolled leaf mutant was controlled by a single recessive gene. The fine-mapping with STS (sequence tagged site) markers revealed that the mutant gene was located on the long arm of chromosome 12. We were able to narrow it down until 130Kb interval where 6 functional genes, 6 expressed genes and 2 hypothetical genes were found.