Genetic Analysis And Gene Mapping For A Highly-Tillering And Dwarf Mutant Of Rice (Oryza Sativa L.)

A highly-tillering and dwarf mutant (htd) was found from the progeny of indica rice variety 93-11 after being treated with γ-ray. The mutant shows significantly shorter plant height, much higher tiller number, narrower and smaller leaves and smaller seeds, but its seed production is normal.Using the method of the classical genetics, the plant heights of F₁, F₂ of htd/zhonghua-11 and htd/guangluai-4 were reseached. The F₁ generations showed wild-type phenotype. The F₂ population was segregated into wild-type plants and mutant plants, x² test indicated that the segregation followed the expected proportion of 3 : 1 . The result suggested that the mutant phenotype is controlled by a recessive gene, which we named as htd(t).To examine if the mutant gene is a new gene, 10 wild-type plants and 10 mutant plants were selected randomly from the F₂ population of htd/guangluai-4 and htd/zho-nghuall to make a wild-type DNA pool and a mutant DNA pool respectively for bulked segregant analysis with SSR markers. Two SSR markers, RM303 and RM241, on chromosome 4 were found polymorphic between the two DNA pools. The two SSR markers together with other adjacent SSR markers were assayed on 266 mutants from the F₂ population of htd/guangluai-4 and analyzed with software MAPMAKER/EXP3.0. Result showed that the mutant gene htd(t) was located between the two SSR markers RM303 and RM241 with distances of 3.0 cM and 3.6 cM from the two markers, respectively.Literature search showed that a dwarf gene has been mapped at the same position recently. Therefore, the two genes must be allelic.