Common lambsquarters is highly competitive in many cropping systems and has demonstrated resistance to several herbicide mechanisms of action. However, predicting the spread of resistance is difficult due to limited information about gene flow. We conducted research to determine the potential for movement of resistance alleles in common lambsquarters under field conditions. Chenopodium giganteum (a member of the C. album aggregate) that has a dominant magenta phenotypic marker was used as a pollen parent in gene flow experiments. A wild-type accession of common lambsquarters was used as a seed parent. Seed parents were grown in a soybean field and arranged in concentric circles 2 to 15 m from a center which contained 24 pollen parents. The concentric circles were divided into eight directions. Pollen movement was estimated by determining the percentage of progeny with the magenta phenotype from seed parents. Average cross-pollination across directions was greatest (3.0%) at 2 m and decreased to low levels (0.16%) 15 m from the center, consistent with observations of other primarily self-pollinated species. Cross-pollination was greatest (P < 0.10) in the south-southwest, west-southwest, and west-northwest directions, approximately 180° from the prevailing wind direction during the time of pollen shed. Since common lambsquarters does not have an active dispersal mechanism for seeds, pollen-mediated gene flow may play an important role in the transfer and frequency of resistance alleles within and between populations.

Nomenclature: Common lambsquarters, Chenopodium album L. CHEAL; magenta spreen, C. giganteum D. Don; soybean, Glycine max (L.) Merr.