Molecular basis of multiple resistance to ACCase‐inhibiting and ALS‐inhibiting herbicides in Lolium rigidum

Abstract

Summary Herbicide resistance in Lolium rigidum is widespread across much of the agricultural land in Australia. As the incidence of herbicide resistance has increased, so has the incidence of multiple herbicide resistance. This reduces the herbicide options available for control of this weed. This study reports on the successful amplification and sequencing of the acetolactate synthase (ALS) gene of L. rigidum using primers designed from sequence information of related taxa. This enables, for the first time, the successful determination of a mutation in the ALS gene of this species that provides resistance to ALS‐inhibiting herbicides. This mutation causes amino acid substitution at Trp574 (numbering standardised to Arabidopsis thaliana) to Leu which had been reported to confer a high level of resistance against all classes of ALS inhibitor herbicides. In addition, multiple resistance to ALS‐inhibiting and acetyl‐coenzyme A carboxylase‐inhibiting herbicides is acquired through the independent accumulation of mutant alleles for the target sites. This may thus explain some of the irregular, mosaic resistance patterns that occur in this predominantly outcrossing species.

Acetolactate synthase activity in Euphorbia heterophylla resistant to ALS- and protox- inhibiting herbicides

“…For the (Patzoldt & Tranel, 2001), Gli 654 (Laplante et al, 2009), and for the sulfonylureas, replacement at position Pro 197 (Yu et al, 2008); Asp 376 (Zheng et al, 2011); Arg 377 (Massa et al, 2011). The replacement of Trp574 causes high resistance to chemical groups of sulfonylureas and imidazolinones simultaneously (Patzoldt & Tranel, 2002;Tan et al, 2007). The replacement of Ala-122-Tyr results in imidazolinone resistance, but not to sulfonylureas, while the replacement of Ala-122-Tir originates imidazolinone resistance, sulfonylureas and sulfonanilide, probably because Tir present a residue much larger and more aromatic than the Thr (Han et al, 2012).…”

Acetohydroxyacid synthase (AHAS) amino acid substitution Asp376Glu in Lolium perenne: effect on herbicide efficacy and plant growth

“…The possibility of target-site-and non-target-site-based resistance mechanisms (NTSR) within a weed population or even within a single individual have been extensively discussed in previous studies [12,23]. The probability of NTSR mechanisms, causing cross-and/or multiple resistance patterns and thus biasing the planned herbicide efficacy studies, had to be reduced for the selected genotypes.…”

“…The detection of NTSR mechanisms in selected genotypes was based on the hypotheses that NTSR results in differential susceptibility to cyclohexanediones (CHD) and aryloxyphenoxy-propionates (APP). It is assumed that plants bearing NTSR are susceptible to cycloxydim (CHD) and resistant against clodinafop (APP) [23,29]. After four multiplication steps, four tillers per parent plant were treated with clodinafop at a rate of 60 g AI ha -1 (Topik 100, 100 g AI l -1 , Syngenta Agro GmbH).…”

Tolerance of blackgrass (Alopecurus myosuroide) to sylfonylurea herbicides in the Czech Republic

“…Plants resistant to chlorsulfuron were reported in previous studies. Tan et al (2007) tested some populations of Lolium rigidum and found 84-100 % of surviving plants at the dose of 15.0 g/ha. Adkins et al (1997) reported the Fallopia convolvulus (F) resistance to chlorsulfuron.…”