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INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE
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HORSEWEED
(
Conyza canadensis
)
with
GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE )
Inhibition of Acetolactate Synthase
MUTATION: ALANINE 205 to VALINE
Horseweed
(
Conyza canadensis
) is a dicot plant in the asteraceae family. A single amino acid substitution from Alanine 205 to Valine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.
Horseweed
Chemical Family
Example Herbicide
Resistance Level
Imidazolinones
Imazethapyr
Resistant > 10 fold
Pyrimidinyl benzoates
Bispyribac-Na
Resistant > 10 fold
Sulfonylureas
Chlorsulfuron
Resistant > 10 fold
Triazolopyrimidine - Type 1
Chloransulam-methyl
Not Determined
Triazolinones
Flucarbazone-Na
Not Determined
NOTE
Authors suggest resistance to pyrithiobac-sodium (a PTB) may be due to something other than, or in addition to, the ALS mutation.
REFERENCES
Matzrafi, M., T. W. Lazar, M. Sibony, and B. Rubin
.
2015
.
Conyza
species: distribution and evolution of multiple target-site herbicide resistances
.
Planta
242
:
259 - 267
.
Conyza canadensis
(CC) and
Conyza bonariensis
(CB) are troublesome weeds around the world. Extensive use of herbicides has led to the evolution of numerous
Conyza
spp. herbicide-resistant populations. Seeds of 91 CC and CB populations were collected across Israel. They were mostly found (86 %) in roadsides and urban habitats, two disturbed habitats that had been dramatically impacted by human activities, thus we classify these species as anthropogenic. Although pyrithiobac-sodium was only used in cotton fields, 90 % of
Conyza
spp. populations were identified as pyrithiobac-sodium resistant, suggesting possible natural resistance to pyrithiobac-sodium. CC21 and CC17
C. canadensis
populations were highly resistant to all tested ALS inhibitors due to a substitution in the
ALS
gene from Trp574 to Leu. They were also atrazine resistant due to a substitution in the
psb
A gene from Ser264 to Gly. The high level of imazapyr and pyrithiobac-sodium resistance observed in the CC10 population was due to an Ala205 to Val substitution. However, high resistance to sulfometuron methyl and pyrithiobac-sodium in population CC6 was due to a point mutation at Pro197 to Ser. All resistant plants of CC21 population showed both
psb
A (Ser264 to Gly) and
ALS
(Trp574 to Leu) substitutions, leading us to the conclusion that the attempt to overcome resistance to one mode of action by overuse of another will most likely lead to multiple herbicide resistance. Furthermore, we concluded that only individuals that carry both mutations could survive the shift between the two modes of action and overcome the fitness cost associated with the PSII resistance.
.
This case was entered by Patrick Tranel Email:
tranel@illinois.edu
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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.
Wednesday, December 11, 2024
. Available
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