Roegneria kamoji Ohwi (Poaceae), a wild relative plant of wheat which is widely distributed across China, has become a dominant and problematic weed in wheat fields in some regions. We have previously confirmed that R. kamoji is highly tolerant to foliar-applied acetyl-CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors in wheat (Triticum aestivum L.). The sensitivity of R. kamoji to pre-emergence (PRE) herbicides and the basis of fenclorim increase selectivity to butachlor between wheat and R. kamoji were evaluated in this study. Screenhouse bioassay showed that R. kamoji exhibited similar sensitivity to wheat to PRE herbicides at their recommended field doses (RFD); it also showed that buatchlor provides the highest relative control for R. kamoji (53.4% emergence and 81.5% fresh weight reduction, respectively), while it had no impact on seedling emergence of wheat among the six PRE herbicides. When butachlor was applied at four-fold RFD, no R. kamoji seedlings emerged; however, it significantly reduced the above-ground biomass of wheat compared with the non-treated control. Pre-treatment with herbicide safener fenclorim by seed soaking increased the ED₁₀ value of butachlor to wheat from 221.8 to 1600.1 g a.i. ha⁻¹, thus increasing the selectivity index from 9.6 to 68.9 between wheat and R. kamoji. The activities of α-amylase activity and protein content during germination, and glutathione-S-transferase (GST) and β-ketoacyl-CoA synthase (KCS) in the seedlings, could be induced by butachlor in both wheat seeds with or without fenclorim pre-soaking. These results suggested that butachlor provides the highest control for R. kamoji and did not affect germination and emergence in wheat. The basis of fenclorim-increased selectivity to butachlor was associated with the induced GST and KCS-mediated enhanced herbicide metabolism in wheat.

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.

Understanding the ability of hybrids of genetically modified (GM) soybean and wild soybean to survive and reproduce under unfavorable conditions is critical for answering questions regarding risk assessment and the existence of transgenes in the environment. To investigate the effects of high-temperature stress on soybean growth and competitive ability, the GM soybean DBN8002, which expresses the VIP3Aa and PAT proteins, and F₂ generations derived from a cross between GM soybean and NJW (wild soybean) were placed in a greenhouse with an elevated temperature (38/32 °C) for 14 days, and the plant agronomic performance and foreign protein levels of hybrid soybean were evaluated to observe their responses to high temperature. The results revealed that the VIP3Aa and PAT protein levels in F₂ and GM were not influenced by high-temperature stress. In contrast, the pollen germination, pod number, hundred-seed weight, and seed vigor of the F₂ hybrid and parent soybean plants decreased after high-temperature stress. However, except for the number of fully filled seeds per plant, the above parameters of the F₂ hybrid were similar to or slightly lower than those of wild soybean, and no significant difference in fitness was observed between the F₂ hybrid and wild soybean, indicating that the growth and competitive ability of the hybrid were similar to those of its female parent under heat stress conditions, resulting in the transgenes persisting and spreading within agricultural ecosystems. Our results enhance the understanding of the GM soybean plant’s response to heat stress, lay the foundation for breeding heat-resistant soybean varieties, and provide new insights and advanced information on the ecological risks arising from the escape of transgenes.