Abstract:

Weedy rice refers to rice plants growing in paddy field and its surrounding area as a weedy type, which is distributed in rice-transplanting areas in Liaoning Province of north China. Field surveys were conducted to define the distribution region of Chinese weedy rice, weedy rice resources were collected from the main rice-growing regions of Liaoning Province in the autumns 2003–2005, and the phenotypic diversity of weedy rice was tested at the Rice Research Institute of Shenyang Agricultural University in 2006. Weedy rice seeds were sown on 12 April and seedlings were transplanted to the field on 20 May 2006. Data were collected on various morphological variables of weedy rice. Samples of weedy rice were analysed with 30 SSR makers and compared with the collections of cultivated rice and wild rice O. rufipongon. The percentage of polymorphic loci was 86.67% and Shannon's information index was 0.762, showing that the genetic diversity of Liaoning weedy rice is very high. The GST of 0.843 suggested that the main genetic variation of weedy rice resided among populations. Weedy rice populations in Liaoning were closely related to cultivated japonica rice but distantly related to O. rufipongon and cultivated indica rice. Weedy rice in Liaoning most probably originated from the local cultivated japonica rice through natural hybridization and natural mutation. The weakness of breeding and cultivation methods promoted the producing of Liaoning weedy rice.

Key words: Weedy rice, Distribution, SSR, Genetic diversity, Origin, Population differentiation