Genetic relationships and diversity of weedy rice (Oryza sativa L.) and cultivated rice varieties in Okayama Prefecture, Japan

In order to clarify the origin of weedy rice (Oryza sativa L.) in Okayama Prefecture, Japan, we used a set of 15 sequence-tagged site primers to analyze polymorphisms among 27 weedy rice accessions and 88 cultivated rice varieties accessions including common rice varieties from Okayama. The band patterns indicated that 13 of the japonica weedy accessions corresponded exactly with one of the japonica cultivated rice varieties. Furthermore, with the exception of a strong shattering habit, these japonica weedy accessions closely resembled each corresponding rice variety in morphophysiological characteristics. Consequently, in view of the close genetic homology and high morphophysiological resemblance between weedy rice and cultivated rice varieties in Okayama, we conclude that weedy rice originated from cultivated rice varieties as an “off-type” caused by genetic mutation accompanied by the development of a strong shattering habit.