Gene flow in self-pollinated weed species affected by environmental factors

Abstract The rapid spread of herbicide resistance in weeds, driven by gene flow through multiple pathways, poses an increasing challenge for agricultural systems. This review summarizes the extent and distance of pollen- and seed-mediated gene flow (PMGF and SMGF, respectively) in selected self-pollinated weeds and the environmental factors that influence PMGF. A comprehensive literature review was focused on assessing PMGF patterns, dispersal mechanisms, and influencing factors across self-pollinated weed species. Statistical analyses were conducted to evaluate correlations between PMGF and environmental variables, including temperature, precipitation, humidity, and elevation. Self-pollinated weeds in the Asteraceae family show the highest PMGF (average 10.63%), with common groundsel showing 24% at 0.5 m from the pollen source. Solanaceae and Chenopodiaceae are plant families with the second and third highest PMGF (average 10.00% and 1.58%, respectively). Within Solanaceae , eastern black nightshade exhibited the maximum PMGF (17%), whereas in Chenopodiaceae, magenta spreen showed the highest gene flow, reaching 3% at 15 m from the pollen source. In contrast, the lowest mean PMGF was observed in Poaceae and Brassicaceae (average 1.87% and 0.33%, respectively). Furthermore, among environmental variables, only temperature showed a significant correlation (P < 0.05). Due to the limited number of studies, this correlation should be viewed cautiously, as it likely reflects general patterns rather than a causal link to PMGF. Bold-seeded grasses such as oat may disperse seeds at low frequency (14-18%), however, light-seeded species such as horseweed can disperse as high as 99% of their seeds. Understanding gene flow in self-pollinated weeds with high fecundity is vital to limiting herbicide resistance spread in such species.