A biotype of common waterhemp (Amaranthus rudis) resistant to triazine and ALS herbicides

Abstract

A common waterhemp biotype that was not controlled by triazine or acetolactate synthase (ALS)-inhibiting herbicides was isolated from a field in Bond County, IL, in the fall of 1996. Greenhouse and laboratory experiments determined resistance to atrazine and three ALS-inhibiting herbicides in this biotype. Based on whole-plant response, the Bond County common waterhemp biotype required over 1,000 times more imazethapyr relative to a susceptible biotype to reduce growth 50%. Cross-resistance to thifensulfuron, a sulfonylurea, and flumetsulam, a triazolopyrimidine sulfonanilide, was also detected. Based on in vivo enzyme assays, ALS in the Bond County common waterhemp biotype was 20-, > 8-, and 68-fold less sensitive than ALS in the susceptible biotype to imazethapyr, thifensulfuron, and flumetsulam, respectively. Whole-plant efficacy trials also indicated that the Bond County common waterhemp biotype required more than 20 kg ha−1of atrazine to inhibit growth 50%. Chlorophyll fluorescence assays revealed that 100 nM atrazine inhibited photosynthesis in the susceptible biotype, whereas 10 M did not affect photosynthesis in the resistant biotype. Regions of the genes encoding ALS and D1 proteins were sequenced to determine the molecular basis for the resistances. Triazine resistance was conferred by a glycine for serine substitution at residue 264 of the D1 protein, while ALS resistance was conferred by a leucine for tryptophan substitution at residue 569 of ALS.

Transmission of herbicide resistance from a monoecious to a dioecious weedy Amaranthus species

“…The portion of ALS amplified by PCR (region A, Foes et al 1998) was polymorphic for an EcoRV restriction site between the A. rudis and A. hybridus parental populations used in this study (Fig. 1).…”

“…Imazethapyr (Pursuit, BASF) was applied to plants using a compressed air, moving nozzle, laboratory spray chamber as described previously (Foes et al 1998). Putative hybrid plants were treated with imazethapyr at 210 g acid equivalent ha -1 (3× typical field use rate) when 5-10 cm tall and evaluated 2 weeks later.…”

“…Polymerase chain reactions (PCRs) were performed with alsf1 and alsr1 primers to amplify region A of ALS essentially as described by Foes et al (1998). Samples for the PCRs consisted of a total volume of 25 ul with 20 mM Tris-Cl (pH 8), 50 mM KCl, 2 mM MgCl 2 , 0.2 mM each dNTP, 0.4 uM each primer, 1.0 U Taq DNA polymerase (Gibco BRL), and 40 ng genomic DNA.…”

Nontarget-Site Resistance to ALS Inhibitors in Waterhemp (Amaranthus tuberculatus)

“…Plants from the MCR population were treated with chlorimuron, 46 g ha 21 , or imazethapyr, 70 g ha 21 (equivalent to 43 and 13 typical field use rates, respectively). Surviving plants were evaluated for the presence of the Trp574Leu ALS mutation using a polymerase chain reaction (PCR) restriction fragment length polymorphism essentially as described previously (Foes et al 1998). Primers used for the PCR were AmALS-F2 and AmALS-R2 (Table 2).…”

Acetolactate synthase mutation conferring imidazolinone-specific herbicide resistance in Amaranthus hybridus

“…These regions were amplified using primers and reaction profiles specified in a previous report (Foes et al, 1998). PCR products were sequenced using dye-terminator technology and an ABI 377 automated sequencer (Applied Biosystems).…”