Abstract: A cleistogamy mutant fod （floret opening defective） was isolated by ethyl methane sulfonate （EMS） from a japonica rice cultivar Xiushui09 （XS09）. Compared with the wild type XS09， the mutant fod showed reduced plant height， round seeds and closed spikelets. Physiological experiments showed that the mutant fod was insensitive to the exogenous brassinosteroid （BR）. Genetic analysis indicated that the phenotype of the mutant was controlled by a single recessive gene. The Osfod gene was mapped on the chromosome 7 between the mark P8 and P9, which was 296 kb in length.

Key words: rice, cleistogamy, brassinosteroid, genetic analysis, gene mapping