Weed to Weed Transfer of Glyphosate Resistance

Crop to weed transmission of glyphosate resistance via gene flow has been frequently researched but little information is available on weed to weed interactions. To determine the possible occurrence of weed to weed transfer of the glyphosate resistance, researchers at the Iowa State University and University of Delaware examined hybridization in Conyza, a prevalent weed species in the Midwestern United States. The researchers observed that hybridization and transfer of herbicide resistance can occur between C. canadensis and C. ramosissima.

The researchers have determined that approximately 3% of ova were fertilized by pollen of the opposing species and produced viable seeds. The interspecific hybrids were found to have intermediate phenotype between the parents but exhibit superior resistance to glyphosate compared to the herbicide resistant C. canadensis parent.

The possibility of introgressive hybridization suggest complications in the management of glyphosate resistant weed populations in glyphosate resistant crops and the containment of glyphosate resistance genes within these agroecosystems. The researchers reiterated that weed control should be combined with alternative management tactics to mitigate the evolution of herbicide resistance in the current agroecosystems.

The paper published by the American Journal of Botany, can be accessed at http://www.amjbot.org/cgi/content/abstract/94/4/660.