Morphological and genetic characterization of off-type rice plants collected from farm fields in Korea

Off-type rice plants occurring in farm fields cause yield loss due to competition with cultivated rice, in addition to hindering field management and harvest work. This study aimed to observe the agronomic characteristics and trace the origins of off-type rice plants using molecular markers. A total of 116 rice accessions, comprising 35 off-type plants collected from Korean farm fields, 19 Korean commercial cultivars, 12 Korean land races, and 50 weedy rice collections, were phenotyped and genotyped using selected SSR and Subspecies Specific (SS)-STS markers. The results showed that the plant height, culm length, and leaf length of off-type rice plants were larger than those of cultivated rice, which is the typical phenotype of weedy rice. However, off-type plants were highly sterile, as opposed to weedy rice, which were highly fertile. Genotype analysis with SSR and SS-STS markers revealed that off-type rice plants were heterozygous at most of the tested marker loci, suggesting that the off-type rice plants may have originated from natural outcrossing. The genotypes of off-type rice plants were closely related to both weedy and cultivated rice, and the phylogenetic analysis revealed that the relationship of the clustered group of offtype rice plants is intermediate between Indica type weedy rice and Japonica type commercial varieties. These results suggested that off-type rice plants collected in Korean farm fields might have originated from natural outcrossing between Indica type weedy rice and the cultivated Japonica type commercial varieties.