Cross resistance patterns to acetyl-CoA carboxylase inhibiting herbicides associated with different mutations in Italian ryegrass from China. (May 2021) - Zhang, Pei
Abstract: Fenoxaprop- P -ethyl is widely used to control the Italian ryegrass ( Lolium multiflorum Lam.) in China. Recently, Italian ryegrass populations have been reported with resistance to fenoxaprop- P -ethyl in two provinces (Jiangsu and Henan) of China. It was important to clarify the resistance patterns of these populations which had evolved resistance to fenoxaprop- P -ethyl. In this study, we investigated three Italian ryegrass populations (HZGX-2, HZYC-4, and HZYC-5) that were involved with high resistance to fenoxaprop- P -ethyl. The HZGX-2 population showed low cross-resistance to clethodim, haloxyfop- R -methyl, clodinafop-propargyl, and quizalofop- P -ethyl, but was still susceptible to sethoxydim and pinoxaden. The HZYC-4 and HZYC-5 populations showed cross resistance to all tested acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. We examined the genetic changes in three Italian ryegrass populations and identified four mutations, named D2078G, C2088R, I1781L, and I2041N and occurring within different frequencies in these populations. These mutations have been reported to underlie resistance to ACCase-inhibiting herbicides. In the HZGX-2 population wild type frequency was 73%, and the mutation frequencies at positions 1781, 2041, and 2078 were 13%, 7%, and 7%, respectively. In the HZYC-4 population, the mutation frequencies were 93% at 1781 and 7% at 2041. In the HZYC-5 population, the mutation frequencies were 72% at 1781, 16% at 2041, and 12% at 2088. There was no wild type found in the HZYC-4 and HZYC-5 populations, either. The cytochrome P450 inhibitors was shown to slightly reduce the ED50 values of fenoxaprop-P-ethyl-resistant populations, which implied a combination of target-site resistance and non-target-site resistance was involved in resistance. This study can help the weed management of agricultural activities in China and other countries. Highlights: Three Italian ryegrass populations were found resistant to fenoxaprop- P -ethyl. Cross-resistance patterns were detected in Italian ryegrass populations. Four mutations were found in three Italian ryegrass populations. Non-target-site resistance was involved in resistance as well.