The induction of grain size and colour mutations in rice (Oryza sativa L.) by radioisotopes

Summary Seven mutants with changes in grain size and in pigmentation of various organs were isolated in the M ₂ and M ₃ generations of the Patnai variety of winter rice after treatment with ³² P and ³⁵ S. Some of these could be useful for breeding.The narrow grain mutant, isolated in the M ₃ generation after treatment with ³² P, was high-yielding and had fine grains and an increased number of long panicles.Two short grain mutants with changed husk colour were obtained in the M ₂ generation after treatment with ³² P. One was also early maturing.One purple apiculus and three purple husk mutants were isolated in the M ₂ generation after treatment with ³⁵ S. Some of these also had reduced plant height and short grains. The purple apiculus mutant bred true for stigma and apiculus colour, but segregated for leaf sheath colour. In purple husk mutants the segregation of mutant characteristics was unusual and there was manifestation of new characters.