INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE
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GROUP B/2 resistance: (ALS INHIBITORS)
Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)
MUTATION: TRYPTOPHAN 574 to LEUCINE
) is a dicot plant in the amaranthaceae family. A single amino acid substitution from Tryptophan 574 to Leucine has led to resistance to ALS inhibitors as indicated in the table below.
Resistant > 10 fold
Resistant > 10 fold
"Considerable pleiotrophic effects" have been associated with Trp574Leu in A. powellii. See Tardif et al. (2006) for details.
Tardif, F. J. ; Rajcan, I. ; Costea, M.
A mutation in the herbicide target site acetohydroxyacid synthase produces morphological and structural alterations and reduces fitness in
251 - 264
We investigated the effect of a herbicide resistance-conferring mutation on fitness in
. Morphological and histological observations were made. Growth and leaf appearance were recorded for six resistant and six susceptible populations. The competitiveness of a susceptible population was compared with that of a resistant population using a replacement series experiment. Leaves of the resistant plants were distorted and much smaller than those of susceptible plants. Additionally, they exhibited an abnormal morphological and structural pattern consisting of a mosaic of heterogeneous areas in the same leaf blade. The roots and stems had similar structures in susceptible and resistant plants, but the former were up to four times more developed. The resistant plants were slower to develop and produced 67% less biomass and 58% lower leaf area than susceptible plants. Under competitive conditions, one susceptible population outperformed one resistant population by 7-15 times. The Trp
Leu acetohydroxyacid synthase (
) mutation appears to have considerable pleiotropic effects on the early growth and development of the plants which, in competitive conditions, greatly reduce fitness.
McNaughton, K. E. ; Letarte, J. ; Lee, E. A. ; Tardif, F. J.
confer herbicide resistance in redroot pigweed (
) and Powell amaranth (
17 - 22
A number of redroot pigweed and Powell amaranth populations from various locations in Ontario, Canada, have distinct patterns of resistance to the acetolactate synthase-inhibiting herbicides imazethapyr and thifensulfuron. This suggested the presence of diverse
gene mutations among these populations. Seven polymerase chain reaction primer pairs were used to amplify the gene to obtain full sequence information and to determine the identity of resistance-conferring mutations. There was a high degree of similarity in the
gene of the two species with only five nucleotides and one amino acid differing. A total of four herbicide resistance-conferring mutations were identified in the two species. The Ala
Val, and Trp
Leu amino acid substitutions were found in redroot pigweed whereas Ala
Leu, and Ser
Thr were detected in Powell amaranth. The pattern of resistance known to be conferred by the mutations concurred with the resistance level observed at the whole plant level. Distinct mutations being found in geographically separated populations suggest that selection for resistance occurred simultaneously in different locations. It reinforces the fact that resistance to ALS inhibitors is easily selected and that growers need to take this into account when formulating weed management strategies.
This case was entered by Patrick Tranel Email:
PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site. Citation:
Heap, I. The International Herbicide-Resistant Weed Database. Online.
Sunday, January 24, 2021
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