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

Wenlei Guo1, Lingling Lv1, Lele Zhang1, Qi Li1, Cuixia Wu2, Xingtao Lu2, Weitang Liu1, Jinxin Wang1*
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 target-site 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 mesosulfuron-methyl. Cross resistance patterns showed that the R population was highly resistant to clodinafop-propargyl, moderately resistant to pyroxsulam and flucarbazonc-sodium, 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.
Keywords: Acetolactate synthase, acetyl-CoA carboxylase, cytochrome P450, mutation, resistance.
1Shandong Agricultural University, College of Plant Protection, Taian, 271018, China. *Corresponding author (wangjx@sdau.edu.cn).
2Taian Academy of Agricultural Sciences of Shandong Province, Taian, 271000, China.