INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

CATCHWEED BEDSTRAW (Galium aparine) with GROUP B/2 resistance: (ALS INHIBITORS) Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)

MUTATION: PROLINE 197 to SERINE

Catchweed Bedstraw (Galium aparine) is a dicot plant in the rubiaceae family. A single amino acid substitution from Proline 197 to Serine has led to resistance to ALS inhibitors as indicated in the table below.		Catchweed Bedstraw

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Intermediate Resistance < 10 fold
Pyrimidinylthiobenzoates	Bispyribac-Na	Intermediate Resistance < 10 fold
Sulfonylureas	Chlorsulfuron	Intermediate Resistance < 10 fold
Triazolopyrimidines	Chloransulam-methyl	Intermediate Resistance < 10 fold
Sulfonylaminocarbonyltriazolinone	Flucarbazone-Na	Intermediate Resistance < 10 fold

NOTE

Paper includes citation to prior report (in Chinese) of this mutation. R/S ratios not quantified, but plants with this mutation survived 4x dose of one herbicide from each class.

REFERENCES

Deng, W., Y. Di, J. Cai, Y. Chen, and S. Yuan. 2019. Target-site resistance mechanisms to tribenuron-methyl and cross-resistance patterns to ALS-inhibiting herbicides of catchweed bedstraw (Galium aparine) with different ALS mutations.. Weed Science 67 : 183 - 188.

Catchweed bedstraw (Galium aparine L.) is a problematic dicot weed that occurs in major winter wheat (Triticum aestivum L.) fields in China. Tribenuron-methyl has been widely used to control broadleaf weeds since 1988 in China. However, overuse has led to the resistance evolution of G. aparine to tribenuron-methyl. In this study, 20 G. aparine populations collected from Shandong and Henan provinces were used to determine tribenuron-methyl resistance and target-site resistance mechanisms. In dose–response experiments, 12 G. aparine populations showed different resistance levels (2.92 to 842.41-fold) to tribenuron-methyl compared with the susceptible population. Five different acetolactate synthase (ALS) mutations (Pro-197-Leu, Pro- 197-Ser, Pro-197-His, Asp-376-Glu, and Trp-574-Leu) were detected in different resistant populations. Individuals heterozygous for Pro-197-Ser and Trp-574-Leu mutations were also observed in a resistant population (HN6). In addition, pHB4 (Pro-197-Ser), pHB7 (Pro-197- His), pHB8 (Pro-197-Leu), pHB5 (Asp-376-Glu), and pHB3 (Trp-574-Leu) subpopulations individually homozygous for specific ALS mutations were generated to evaluate the cross- resistance to ALS-inhibiting herbicides. The pHB4, pHB7, pHB8, pHB5, and pHB3 subpopulations all were resistant to sulfonylurea, pyrazosulfuron-ethyl, triazolopyrimidine, flumetsulam, sulfonylamino-carbonyl-triazolinone, flucarbazone-sodium, pyrimidinyl thio- benzoate, pyribenzoxim, and the imidazolinone imazethapyr. These results indicated the diversity of the resistance-conferring ALS mutations in G. aparine, and all these mutations resulted in broad cross-resistance to five kinds of ALS-inhibiting herbicides..

This case was entered by Patrick Tranel Email: tranel@illinois.edu

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