Abstract
A Mutation causing the abnormal development of grains was induced in rlce (Oryza sativa L.) by means of the tetraploid-irradiation technique. The grain was about half of the size of a normal brown rice and consisted entirely of the embryonic tissue. Microscopic observations revealed that the endosperm cells stopped dividing at early developmental stage, while the embryo continued growing into a large cellular clump in which a plumule, a radicle and a scutellum differentiated. We termed these grains endospermless grains. On the basis of the segregation ratios of endospermless grains, it is concluded that a recessive allele on a single locus or a deletion of small chromosomal segment is resposible for the abnormal development of grains.
