The Ile‐2041‐Val mutation in the ACCase gene confers resistance to clodinafop‐propargyl in American sloughgrass (Beckmannia syzigachne Steud)

Abstract

BACKGROUND Exploring herbicide resistance mechanisms in weeds is regarded as an important part of designing resistance management strategies and rationalizing the use of herbicides. Beckmannia syzigachne is one of the most important agricultural weeds in China. Long‐term use of acetyl‐CoA carboxylase (ACCase)‐inhibiting herbicides has led to evolution of herbicide resistance in B. syzigachne. ACCase‐inhibiting herbicides consist of three chemical families, including the aryloxyphenoxypropionates (APPs), cyclohexanediones (CHDs) and phenylpyraxoline (DENs). RESULTS Based on whole‐plant dose–response experiments, a B. syzigachne population (BS‐R) was confirmed to be 20‐ and 12‐fold resistant to the APP herbicides clodinafop‐propargyl and quizalofop‐P‐ethyl; 2.2‐, 2.8‐, and 2.8‐fold resistant to fenoxaprop‐P‐ethyl, the CHD herbicide sethoxydim and PPZ herbicide pinoxaden, respectively, compared to the susceptible counterpart (BS‐S). Resistance to clodinafop‐propargyl in the BS‐R population could not be reversed by the known cytochrome P450 (CYP450) inhibitor malathion and glutathione S‐transferase (GST) inhibitor 4‐chloro‐7‐nitrobenzoxadiazole. In addition, no difference in CYP450 and GST activity was confirmed in BS‐R and BS‐S population. ACCase gene sequencing revealed an Ile‐2041‐Val mutation in the BS‐R population. A derived cleaved amplified polymorphic sequence (dCAPS) marker was developed for rapid detection of the specific Ile‐2041‐Val mutation. Correlation quantification of resistance in homo‐ and hetro‐resistant versus WT plants showed that the resistance to clodinafop‐propargyl in this population is conferred by the Ile‐2041‐Val mutation. CONCLUSION Unlike the previous reports on the unique cross‐resistance pattern by the 2041 mutation, this study demonstrates that the BS‐R population confers resistance to certain ACCase‐inhibiting APP, CHD and PPZ herbicides in B. syzigachne.