Abstract
Roegneria kamoji, a perennial monocot weed that belongs to the tribe Triticeae (family: Poaceae), is an emerging problematic weed in winter wheat (Triticum aestivum) fields in China. We have previously confirmed four R. kamoji populations tolerant to acetyl-CoA carboxylase (ACCase) inhibitors, and failed control of these populations by metsulfuron-methyl was observed. The objective of this study was to characterize the level of tolerance to metsulfuron-methyl, the basis of tolerance mechanism, and cross-tolerance to acetolactate synthase (ALS) inhibitors in R. kamoji. A whole-plant dose–response assay showed that plants of all R. kamoji populations (both from wheat fields and uncultivated areas) exhibited high tolerance to metsulfuron-methyl, based on their 100% survival at 6-fold recommended field dose (RFD) and ED50 values >6.84-fold RFD, no susceptible population was found. Gene sequencing indicated that no reported amino acid substitutions associated with resistance to ALS inhibitor were found in the ALS gene among the R. kamoji populations. Pretreatment with the known cytochrome P450 monooxygenases (CytP450) inhibitor malathion reduced the ED50 values of metsulfuron-methyl in two R. kamoji populations. These populations also exhibited cross-tolerance to RFD of mesosulfuron-methyl and bispyribac-sodium. The activities of glutathione-S-transferase (GST) and CytP450 could be induced by metsulfuron-methyl in R. kamoji, which is similar to the known tolerant crop wheat. This is the first report elucidating metsulfuron-methyl tolerance in R. kamoji. The reversal of tolerance by malathion and the GST and/or CytP450 enhanced herbicide metabolism suggests that non-target-site mechanisms confer tolerance to metsulfuron-methyl in R. kamoji.
Highlights
Roegneria kamoji is a common perennial weed that belongs to Roegneria of the tribe Triticeae (Poaceae family)
The dose–response experiments indicated that all R. kamoji populations showed similar response patterns with the increasing metsulfuron-methyl dose, and all plants survived from the treatment of metsulfuron-methyl at 45 g ai ha−1 (6-fold recommended field dose (RFD), Supplementary Figure S2)
6.8-fold greater than that of the RFD dose of metsulfuron-methyl. These results suggested that R. kamoji had high tolerance levels to metsulfuron-methyl
Summary
Roegneria kamoji is a common perennial weed that belongs to Roegneria of the tribe Triticeae (Poaceae family) It is widely distributed across China, Korea, and Japan, and is usually found in hillside, grassland, urban green spaces, and field borders [1,2]. Anhui, and Zhejiang provinces of China (Supplemental Figure S1), and has become a dominant weed in some regions [3,4]. It has been the practice of many farmers to use acetyl-CoA carboxylases (EC 6.4.1.2, ACCase) inhibitors, such as fenoxaprop-ethyl, clodinafop-propargyl, and pinoxaden for postemergence control of graminaceous weeds in wheat [5,6].
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