Discovery And Research On A Spontaneous Variation With High-frequency In Rice

Variation is a quite common phenomenon in living species. Isolation of mutants and further study of their variation mechanisms are the major purpose for functional genomic research. As the model of monocot crop, rice (Oryza sativa L.) brings substantial benefit to other monocot plants. We obtained a spontaneous mutant from an indica variety, zhongxian3037, in the progeny of somatic tissue culture plants. By investigation of their variation characteristics and morphology of the mutants, the major results were shown as follows:1. Genetic characterization of the mutant: (1) The spontaneous mutant has a little frequency of reverse mutation. The total variation frequency is about 36.25%, and more than 97% of the mutants are rather stable. Since the spontaneous variations occurred in the course of somatic propagation, they are belonging to one kind of asexual variation. (2) Being a hot spot of variation, the drooping leaf mutation could be always found in the progeny of the mutants and most of them showed a severely aberrant segregation ratio, other than three normal to one dropping leaf.2. Identification and isolation of the mutants: We have isolated more than 70 different kinds of mutants with distinct and stable mutation phenotype in culm,panicle,leaf and so on. Some of the mutant alleles, which are resemble to the phenotype of DL, EUI,D1and LA, had been identified though allelic tests with their reported loci.3. Mapping of the lesion mimic gene. We isolated a lesion mimic mutant with severe phenotype deriving from the variations. Genetic analysis shows that it is controlled by a single recessive gene. Using the map-based cloning strategy, the lesion mimic gene was mapped on the long arm of rice chromosome 1, between the molecular markers S3412 and S3735.