CATCHWEED BEDSTRAW (Galium aparine) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase
MUTATION: TRYPTOPHAN 574 to GLYCINE
Catchweed Bedstraw (Galium aparine) is a dicot plant in the rubiaceae family. A single amino acid substitution from Tryptophan 574 to Glycine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Catchweed Bedstraw

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Not Determined
Pyrimidinyl benzoates	Bispyribac-Na	Not Determined
Sulfonylureas	Chlorsulfuron	Resistant > 10 fold
Triazolopyrimidine - Type 1	Chloransulam-methyl	Not Determined
Triazolinones	Flucarbazone-Na	Not Determined

NOTE

Two additional ALS amino acid substitutions were identified in the R biotype, so it is not certain if the Trp574Gly substitution confers resistance and/or if one of the other substitutions plays a role.

REFERENCES

Sun Jian ; Wang JinXin ; Zhang HongJun ; Liu JunLiang ; Bian ShengNan. 2011. Study on mutations in ALS for resistance to tribenuron-methyl in Galium aparine L. Agricultural Sciences in China 10 : 86 - 91.

In recent years, Galium aparine L. has not been controlled by tribenuron-methyl in major Chinese winter wheat fields. The objective of this study is to understand the molecular basis of the resistance mechanism to tribenuron-methyl in G. aparine and to find the specific mutation sites in amino acid sequence of acetolactate synthase (ALS) in the resistant biotype of G. aparine. Fragments that encode the ALS were amplified and cloned from susceptible (S) and resistant (R) biotypes of G. aparine to tribenuron-methyl and sequenced subsequently. The result showed that the nucleotide sequence of R-biotype of G. aparine differed from that of the S biotype with three amino acid substitutions, of which, the amino acid substitution of Trp₅₇₄ (TGG) to Gly (GGG) is located in the highly conserved region Domain B. The substitution of Trp₅₇₄ might be responsible for the resistance to tribenuron-methyl in the R-biotype of G. aparine..

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

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