Molecular basis of resistance to mesosulfuron-methyl in Japanese foxtail, <i>Alopecurus japonicus</i>

Abstract

Japanese foxtail (Alopecurus japonicus) has developed resistance to the acetolactate synthase (ALS) herbicide mesosulfuronmethyl, which has been used continuously for several years in winter wheat fields in eastern China. To ascertain the resistance degree of A. japonicus to mesosulfuron-methyl, whole-plant bioassays and in vitro inhibition assays were conducted. The results of the whole-plant bioassays showed that the resistance index of the resistant population, JS-5, to mesosulfuron-methyl was 100-fold higher than that of the susceptible population, JS-7, and the in vitro activity assays confirmed that the ALS sensitivity of the JS-5 to mesosulfuron-methyl was reduced. To further investigate the molecular basis of the resistance, the ALS genes of the JS-5 and JS-7 populations were cloned, sequenced, and compared. Gene sequence analysis revealed a proline-to-threonine substitution at amino acid position 197 of ALS in Domain A that potentially confers the resistance of A. japonicus to mesosulfuronmethyl in the JS-5 population.

Molecular basis of ALS- and/or ACCase-inhibitor resistance in shortawn foxtail (Alopecurus aequalis Sobol.)

“…However, following several years of successful control, more and more researchers are detecting resistance to mesosulfuron-methyl in some grass species [15,20,21].…”

“…In China, sustained reliance on ACCase and/or ALS inhibitors to control weeds has led to the evolution of many resistant populations resulting from mutant ALS and ACCase [16,20]. In the JTJY-1 population, the presence of two different TSR mechanisms (ALS and ACCase mutations) in individual plants has appeared.…”

Mutation at residue 376 of ALS confers tribenuron-methyl resistance in flixweed (Descurainia sophia) populations from Hebei Province, China

“…Currently, six conserved-region amino acid mutations in the ALS are generally accepted to confer ALSinhibitor resistance in weed populations, including Ala122, Pro197, Ala205, Asp376, Trp574, and Ser653 [9]. Nevertheless, Pro197 mutation is the most common site for ALS-inhibitor resistance in weed species, such as Alopecurus japonicus [30], Anthemis cotula [31] and Papaver rhoeas [32]. Mutations of Pro197 to Ser and Thr are by far the most common [33].…”

The challenge of herbicide resistance around the world: a current summary

“…ACCase and ALS inhibitors are the two major classes of herbicides that have been used post emergence to selectively control grasses in wheat for the past two decades . ACCase resistance was first reported in Beckmannia syzigachne in 2014 and many farmers shifted to ALS inhibitors such as mesosulfuron‐methyl for the control of ACCase‐resistant weeds . This, in turn, led to multiple‐resistance in B. syzigachne and A. japonicus .…”

“…21 ACCase resistance was first reported in Beckmannia syzigachne in 2014 22 and many farmers shifted to ALS inhibitors such as mesosulfuron-methyl for the control of ACCase-resistant weeds. 23 This, in turn, led to multiple-resistance in B. syzigachne and A. japonicus. 21,24,25 Current estimates are that nearly 10% of the area in the Chinese provinces of Anhui and Jiangsu are under serious threat of resistance to both ACCase and ALS inhibitors across all key grasses, and farmers are once again shifting herbicide use to PSII inhibitors.…”