Enhanced metabolism and target gene overexpression confer resistance against acetolactate synthase‐inhibiting herbicides in Bromus sterilis

Abstract

BACKGROUND Intensive application of acetolactate synthase (ALS)‐inhibiting herbicides has resulted in herbicide‐resistance in many weeds, including Bromus sterilis. The present study was conducted to identify the mechanisms conferring resistance to ALS‐inhibiting herbicides in a Bromus sterilis biotype. RESULTS Dose–response studies revealed the resistant biotype to be 288 times less sensitive to pyroxsulam than the susceptible biotype. Furthermore, experiment with a single‐dose, proved this biotype was also cross‐resistant to propoxycarbazone, iodosulfuron plus mesosulfuron and sulfosulfuron. Prior treatment with malathion, a known inhibitor of cytochrome P450s, reduced the level of resistance to pyroxsulam. No mutations were detected from the partial ALS gene sequencing. Flow cytometry and chromosome counting rejected ploidy level variation between the susceptible and resistant biotypes. Relative copy number variation ruled out gene amplification. Quantitative real‐time polymerase chain reaction (PCR) detected a significant difference in ALS gene expression between the susceptible and resistant biotypes. CONCLUSIONS Target gene overexpression and enhanced metabolism by cytochrome P450s are likely mechanisms of resistance to pyroxsulam in Bromus sterilis. The current findings highlight the need to monitor additional brome populations for herbicide resistance in Europe and endorse the need for alternate herbicides in integrated weed management to delay the possible evolution of herbicide resistance in these species. © 2020 Society of Chemical Industry

Identification of the most suitable reference gene for gene expression studies with development and abiotic stress response in Bromus sterilis

“…Recent reports from the United Kingdom and the Czech Republic on B. sterilis , developing resistance against commonly used herbicides, indicate that if they remained uncontrolled, these species might become a concern worldwide 25 , 26 . Herbicide resistance mechanisms can be target-site based (TSR) and/or non-target site-based (NTSR).…”

“…Comparative RNA-seq transcriptome analysis between the control and experimental plants can be regarded as the most straightforward way to identify the genes involved in abiotic stresses like herbicide stress 20 . Recent studies on herbicide resistance mechanisms of B. sterilis suggest that both TSR and NTSR can be linked with the herbicide resistance in these species 25 , 26 . Nevertheless, detailed follow-up studies are essential to delineate further the regulatory mechanisms underlying the observed herbicide resistance mechanism 24 .…”

Identification of the Most Suitable Reference Gene for Gene Expression Studies With Development and Abiotic Stress Response in Bromus Sterilis

“…Recent reports from the United Kingdom and the Czech Republic on B. sterilis, developing resistant against commonly used herbicides, indicate that if remained uncontrolled these species might become a concern worldwide 24,25 . Herbicide resistance mechanisms can be target-site based (TSR) and/or non-target site-based (NTSR).…”

“…sterilis suggest that both TSR and NTSR can be linked with the herbicide resistance in these species 24,25 . Nevertheless, detailed follow-up studies are essential to delineate further the regulatory mechanisms underlying the observed herbicide resistance mechanism 24 . However, among the herbicide resistance mechanisms, NTSR mechanisms are considered as more complex to elucidate than the TSRs 20 .…”

Molecular basis of resistance to bensulfuron-methyl and cross-resistance patterns to ALS-inhibiting herbicides in Ludwigia prostrata

“…ALS gene overexpression occurs less frequently than target-gene mutations in weeds resistant to ALS-inhibiting herbicides. Yu et al (2020) and Sen et al (2021) have discovered that target-gene overexpression is associated with resistance to ALSinhibiting herbicides in annual sedge (Cyperus compressus L.) and barren brome (Bromus sterilis L.), respectively. non-target site based resistance (NTSR) mechanisms include reduction of herbicide translocation or uptake, increased sequestration, and detoxification (Délye 2013;Yuan et al 2007).…”