Multiple resistance to thifensulfuron-methyl and fomesafen in redroot pigweed (Amaranthus retroflexus L.) from China

Hengzhi Wang1, Wenlei Guo1, Lele Zhang1, Kongping Zhao1, Luan Ge1, Xueshen Lv1, Weitang Liu1, and Jinxin Wang1*
Redroot pigweed (Amaranthus retroflexus L.) is a troublesome weed infesting soybean (Glycine max [L.] Merr.) productions in China. One redroot pigweed population, collected from Heilongjiang (HLJ) Province, China, was suspected to be resistant to thifensulfuron-methyl and fomesafen. The other one redroot pigweed population, collected from Shandong (SD) Province, was susceptible. The study aimed to characterize the level of thifensulfuron-methyl and fomesafen resistance using HLJ population and identify the potential resistance mechanisms to thifensulfuron-methyl. The sensitivity to other herbicides with and without the same target site was also evaluated. Acetolactate synthase (ALS) gene sequencing revealed that Trp574Leu or Ala205Val amino acid substitution were present in the HLJ population. Whole-plant herbicide bioassays showed that, compared with SD population, HLJ population displayed high level of resistance to thifensulfuron-methyl and moderate resistance to fomesafen. The 50% growth reduction (GR50) value of thifensulfuron-methyl with malathion pretreatment was reduced by 23%, suggesting that both target-site resistance and non-target-site resistance mechanisms were present in thifensulfuron-methyl resistance of redroot pigweed. Cross-resistant patterns showed that the HLJ population evolved resistance to pyrithiobac-sodium, pyroxsulam, imazethapyr and fluoroglycofen, but susceptible to bentazone.
Keywords: Acetolactate synthase, gene mutation, protoporphyrinogen oxidase, multiple resistance.
1Shandong Agricultural University, Key Laboratory of Pesticide Toxicology and Application Technique, Shandong Taian 271018, PR China. *Corresponding author (wangjx@sdau.edu.cn).