Variation in Oxidized Proanthocyanidins in Chinese Weedy Rice Seeds and Their Impact on Ecological Adaptation

Weedy rice, also known as red rice, mainly originates from the de-domestication of cultivated rice and is a vicious weed in paddy fields around the world. Its red seeds are rich in oxidized proanthocyanidins (OPAs). This study investigates whether OPA content varies among different weedy rice strains, whether these variations are possibly related to their adaptation to the local environment, and whether the change in OPA content could affect seed germination. A total of 202 weedy rice accessions from 69 populations across China were collected. Their OPA content, Rc/Rd genotypes, and seed germination percentage on the second, third, and seventh day were detected, respectively. Using bivariate Pearson’s two-tailed correlation analysis and generalized linear mixed models, our results showed that the content of OPAs varied widely among the different strains of weedy rice and were significantly correlated with local environment (latitude) and Rc/Rd genotypes but not with seed germination percentage on the second, third, and seventh day. Thus, the content of OPAs in Chinese weedy rice seeds is closely related to its ecological adaptability. These findings provide insights into the effect of OPA content on the ecological adaptability of weedy rice, which is beneficial to the control and germplasm resource utilization of weedy rice.