First case of glyphosate resistance in Polypogon fugax: possible involvement of P450-based mechanisms

BACKGROUND: Polypogon fugax has evolved resistance to multiple herbicides in China, yet there has been no documented case of glyphosate resistance. A putative glyphosate-resistant P. fugax (HN-R) population was collected from canola fields in Hunan Province, China, surviving glyphosate treatment at the field-recommended rate [540 g acid equivalent (a.e.) ha⁻¹]. The aims of this study were to elucidate the resistance level and mechanism of HN-R population. RESULTS: Dose–response and shikimic acid assays indicated that the HN-R population has developed a low-level resistance (up to 4.6-fold) to glyphosate, compared to two glyphosate-susceptible populations (HN-S and SC-S). No evidence of EPSPS gene mutations and differential EPSPS gene expression were found in association with the resistance. However, pre-treatment with the known cytochrome P450 monooxygenases (P450s) inhibitor, malathion, reversed glyphosate resistance in the HN-R population. Transcriptomic and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analyses showed up-regulation of the PfCYP51 and PfABCG25 genes in the HN-R population. Expression of PfCYP51 in yeast cells significantly enhanced glyphosate tolerance, whereas expression of PfABCG25 did not. Molecular docking experiments suggest that PfCYP51 may catalyze glyphosate metabolism. CONCLUSION: This is the first report of glyphosate resistance in P. fugax, with evidence suggesting P450 involvement in this resistance. This study enhances our understanding of herbicide-resistant weeds and provides valuable insights into the management of glyphosate-resistant weeds in agriculture.