Prevalence of self-incompatibility inOryza barthii Cheval.: Its bearing on the evolution of rice and related taxa

The prevalence of self-incompatibility inOryza barthii Cheval. and its implications on the origin of riceO. sativa L. and some other related taxa are discussed. It is suggested that evolution has been fromO. barthii toO. perennis toO. sativa with corresponding changes in breeding system from allogamy to facultative autogamy to obligate autogamy. The significance of the breeding system for speciation and evolutionary potentialities of these three taxa is pointed out. The presence inO. barthii of the most primitive characters of the genus and its widespread presence in tropical Africa (where nine out of 23 species of the genus occur) have been interpreted as suggesting that this region might have been the centre of origin of the genus.