Genetic Basis of Chlorsulfuron, Atrazine, and Mesotrione Resistance in a Palmer Amaranth (Amaranthus palmeri) Population

A population of Palmer amaranth (Amaranthus palmeri S. Watson) in Kansas (KSR) was found to have evolved resistance to three commonly used herbicides, i.e., chlorsulfuron, atrazine, and mesotrione. Our previous research confirmed the predominance of metabolic resistance to these herbicides in KSR, although a small percentage of plants also showed target-site alteration conferring resistance. In this research, we investigated the inheritance of resistance to these three herbicides in KSR Palmer amaranth. F-1 and F-2 progeny were generated by a conventional breeding approach. On the basis of the response of F-1 and F-2 progeny to three herbicide applications and chi(2) analyses, we found that the resistance of KSR Palmer amaranth to chlorsulfuron and atrazine is controlled by single nuclear genes. However, resistance to mesotrione was found to be imparted by multiple nuclear alleles in this population. Single-gene resistance can spread rapidly, while multiple-gene traits are slower to evolve and spread. Regardless, adoption of integrated weed management strategies can minimize the spread of resistance.