Pollen Quantitative and Genetic Competitiveness of Rice (Oryza sativa L.) and Their Effects on Gene Flow

The gene flow rate in rice (Oryza sativa L.) is a critical factor for establishing safe isolation distances between genetically modified (GM) and non-GM varieties and for ensuring varietal purity in rice breeding programs. This study refines existing gene flow models by disentangling two key components of rice pollen dynamics: quantitative pollen competition and genetic competitiveness. We define B as the proportion of GM pollen within mixed pollen, representing quantitative pollen competitiveness. The outcrossing parameter Cb reflects the likelihood of successful fertilization and seed development by foreign pollen, while the hybrid compatibility parameter Cp captures the relative fertilization success of GM versus non-GM pollen within the same pollen pool. Together, Cb and Cp characterize the genetic competitiveness of rice pollen. Our findings reveal a nonlinear relationship between B and the observed GM pollen rate G, which may exhibit either upward or downward curvature. A nonlinear model provides a significantly better fit to this relationship than a linear model, improving R2 by 4.1-21.4% and reducing RMSE by 9.9-47.8%. The parameters Cb and Cp play central roles in determining gene flow; higher values correspond to stronger GM pollen competitiveness, resulting in higher gene flow rates and greater dispersal distances. Specifically, Cb sets the range of the B-G curve, while Cp determines its curvature.