Herbicides cross resistance of a multiple resistant short-awn foxtail (Alopecurus aequalis Sobol.) population in wheat field

Abstract

Alopecurus aequalis Sobol. is a common grass weed, which has become increasingly troublesome to control in China wheat fields. One A. aequalis population, collected from Anhui Province China, was suspected to be resistant to fenoxaprop-P-ethyl and mesosulfuron-methyl. This study aimed to establish the cross-resistance pattern using the purified subpopulation and explore the potential targetsite and non-target-site based resistance mechanisms. Sequencing results showed that a single nucleotide change of ATT to AAT was present in acetyl-CoA carboxylase (ACCase) gene of the resistant (R) plants, resulting in an Ile2041Asn amino acid substitution. Besides, another single nucleotide change of CCC to CGC was present in acetolactate synthase (ALS) gene of the R plants, resulting in a Pro197Arg amino acid substitution. The homozygous resistant plants were isolated and the seeds were used in whole-plant herbicide bioassays. Compared with the susceptible (S) population, R population displayed high level resistance to fenoxaprop-P-ethyl and mesosulfuronmethyl. Cross resistance patterns showed that the R population was highly resistant to clodinafop-propargyl, moderately resistant to pyroxsulam and flucarbazoncsodium, lowly resistant to pinoxaden, and susceptible to tralkoxydim, sethoxydim, and isoproturon. The pretreatment of piperonyl butoxide reduced the 50% growth reduction (GR50) value of fenoxaprop-P-ethyl, suggesting that target-site resistance and non-target-site resistance mechanisms were both present in fenoxaprop-P-ethyl-resistance of A. aequalis. This is the first report of ACCase Ile2041Asn and ALS Pro197Arg mutation in A. aequalis.

Target site mutations and cytochrome P450s confer resistance to fenoxaprop‐P‐ethyl and mesosulfuron‐methyl in Alopecurus aequalis

“…Of these two mutations, the Ile-to-Asn mutation is the most common amino acid substitution at the 2041 codon of the ACCase gene, and it has since been documented in many weed species, including A. aequalis. 9,12 Noteworthy, our study confirms the first case of a grass weed wileyonlinelibrary.com/journal/ps possessing resistance to ALS-inhibiting herbicides due to a very rare Pro-197-Tyr mutation in the ALS gene. To our knowledge, the frequency of Pro-197-Tyr is the lowest among the 12 amino acid substitutions identified in the 197 codon, 31 and it has only been reported thus far in two broad-leafed weed species.…”

“…[36][37][38][39] Undoubtedly, AHTC-06F1 showed high-and low-level resistance to APPs and DENs, respectively, but no resistance to CHDs, which is consistent with a recent study. 12 The cross-resistance to ALS inhibitors in weeds due to a Pro-197-Tyr point mutation has not been tested yet. 31 In our study, AHTC-06F1 conferred relatively high-level resistance to the SUs, TPs, and SCTs, and moderate resistance to IMIs and PTBs.…”

Herbicides cross resistance of a tribenuron-methyl resistant Capsella bursa-pastoris (L.) Medik. population in wheat field

“…Among 12 amino acid substitutions identified at Pro197 of AHAS gene, the frequency of Pro197Arg substitution is relatively low compared with other substitutions. The Pro197Arg substitution has only been reported in four weed species and all confers high level resistance to SU but low level resistance to other AHAS-inhibiting herbicides (Beckie and Tardif, 2012;Guo et al, 2016). However, we found the R population with Pro197Arg substitution conferring moderate resistance to TP (florasulam) herbicides in shepherd's purse.…”

“…The resistance index (RI) was calculated as the ratio of the GR 50 of the R population to the GR 50 of the S population (Guo et al, 2016).…”

“…The doses of tribenuronmethyl were showed in Table 2, with or without malathion. Treated plants were harvested after 21 d, when dry weights of the above-ground part were assessed as described above (Guo et al, 2016).…”