Identification Of Grain Shape Mutant M102 And Gene Cloning In Rice

Rice is an important food crop in China.The grain shape affects both rice yield and grain quality.Mining new genes and exploring the genetic and molecular mechanisms of grain shape traits are important for improving rice yield and quality.In this study,a rice grain shape mutant M102（M₅）was identified from an EMS mutagenized population of Changlixiang.The investigation of agronomic traits,quality traits,genetic analysis,gene mapping,and complementary test of candidate genes were performed.The main results were as follows:1.Compared with the wild type Changlixiang,M102 has internodes and plant height shortened,grain number per panicle increased,and 1000-grain weight decreased.The grain length becomes shorter,grain width becomes wider,and the ratio of length to width decreases.In terms of the quality of M102,the chalkiness slightly increased,milling quality improved significantly,but the amylose content and protein content have no obvious changes.In terms of stem mechanics,the stem diameter of the second elongation node at the base and the fracture resistance of the single stem and the whole plant were increased.2.Genetic analysis using the M102/Changlixiang F₂population showed that the length to width ratio was divided into two distinct peaks with a limit of 2.85.The ratio of length to width ratio≥2.85 plants to the length to width ratio<2.85 plants in the F₂population was 3:1 and indicating that the mutant trat was controlled by a single recessive nuclear gene.In the F₂population,the segregation distribution of grain length,grain width,and plant height presents a single peak or multiple peaks,which is different from the distribution of length to width ratio.Correlation analysis showed that plant height was significantly positively correlated with grain length,but not with grain width and length to width ratio.3.Through re-sequencing of two extreme DNA pools and MutMap analysis,the grain shape gene was mapped within the range of 20 Mb to 22.7 Mb on chromosome10.Two candidate genes,Os10g0532600 and Os10g0533200,were selected based on information such as SNP-index,base inversion type,SNP type,and gene annotation.Os10g0532600 is annotated as OVATE family protein 27（Os OFP27）and Os10g0533200 is annotated as NAD（P）-binding domain-containing protein.The functions of these two genes have not been reported.4.The complementary test of candidate genes showed that introducing the Os OFP27 genomic DNA fragment of Changlixiang into M102 can restore to the long grain shape phenotype,while Os10g0533200 cannot restore the long grain shape.Therefore,Os OFP27 was identified as the target gene for controlling the grain shape of M102.In this study,a grain shape gene Os OFP27 was cloned by genetic mapping in order to explore molecular mechanism and rice grain shape breeding.