Cross-resistance pattern and alternative herbicides for Cyperus difformis resistant to sulfonylurea herbicides in Korea.
A Cyperus difformis L accession from Chonnam province, Korea was tested for resistance to the sulfonylurea herbicide, imazosulfuron. The accession was confirmed to be resistant (R) and was cross-resistant to other sulfonylurea herbicides, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, the pyrimidinyl thiobenzoate herbicide, bispyribac-sodium, and the imidazolinone herbicide imazapyr, but not to imazaquin. Multiple resistance was tested using twelve herbicides with target sites other than acetolactate synthase (ALS). The R biotype could be controlled by other herbicides with different modes of action such as butachlor, carfentrazone-ethyl, clomeprop, dithiopyr, esprocarb, mefenacet, oxadiazon, pretilachlor, pyrazolate and thiobencarb, applied to soil at recommended rates. Several sulfonylurea herbicide-based mixtures can control both the R and S biotypes of C difformis, except sulfonylurea plus dimepiperate, molinate or pyriftalid, and pyrazolate plus butachlor. Although mixtures of sulfonylurea herbicides might be more effective, they should be avoided and used only in special cases. In terms of in vitro ALS activity, the R biotype was 1139-, 3583-, 1482-, 416-, 5- and 9-fold more resistant to bensulfuron-methyl, cyclosulfamuron, imazosulfuron, pyrazosulfuron-ethyl, bispyribac-sodium and imazapyr, respectively, than the S biotype. The in vivo ALS activity of the R biotype was also less affected by the sulfonylurea herbicides, imazosulfuron and pyrazosulfuron-ethyl, than the S biotype. Results of in vitro and in vivo ALS assays indicated that the resistance mechanism of C difformis to ALS inhibitor herbicides was primarily due to an alteration in the target enzyme, ALS. Greenhouse experiments showed delayed flowering and reduced seed production of the R biotype, which could possibly result in reduced fitness. This unusual observation needs to be confirmed in field situations.
Kuk
Yong In
YI
Biotechnology Research Institute, Chonnam National University, Gwangju 500-757, Korea. yikuk@chonnam.ac.kr
Kim
Kyung Hyun
KH
Kwon
Oh Do
OD
Lee
Do Jin
DJ
Burgos
Nilda R
NR
Jung
Sunyo
S
Guh
Ja Ock
JO
D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D029786:Cyperus / Q000187:drug effects / Q000201:enzymology*; D004351:Drug Resistance / Q000187:drug effects; D006540:Herbicides / Q000008:administration & dosage / Q000378:metabolism* / Q000633:toxicity; D007723:Korea; D008954:Models, Biological; D013453:Sulfonylurea Compounds / Q000008:administration & dosage / Q000378:metabolism* / Q000633:toxicity
D006540:Herbicides; D013453:Sulfonylurea Compounds; D000095:Acetolactate Synthase