Genetic Analysis of Induced Long-Culm Mutants in Rice

Abstract

Five long-culm mutants (LM-1∼-5) induced from a rice cultivar Norin 8 by radia-tions and mutagenic chemicals, were genetically analyzed. The F₁ plants of LM-1x Norin 8 showed similar culm length to the original cultivar. The F₂ plants showed bimodal segregation for culm length and days to heading, respectively, and were grouped into two types in the combination of the above two characters. One type which was the majority corresponded with the Norin 8 type, short culm and early maturity, and the other type corresponded with the LM-1 type, Iong culm and late maturity. The segregation ratio of these two types showed a good fit to the 3 : 1 ratio. Hence, it was concluded that LM-1 was governed by a single recessive induced mutant gene. The F₁ plants of LM-3XNorin 8 had similar culm length to the mutant and their F₂ plants showed a bimodal segregation in the combination of culm length with panicle length; Iong culm and panicle type (LM-3 type) being the majority and Norin 8 type being the minority. It was concluded that LM-3 was governed by a single dominant induced mutant gene. The simultaneous changes in the above characters and probably in the other agronomic characters in these long-culm mutants were considered to be due to the pleiotropic effect of a single mutant gene or the simultaneously induced mutant genes at closely linked loci.