Skip to main content
ARS Home » Research » Publications at this Location » Publication #95450
Title: A KOCHIA (KOCHIA SCOPARIA) BIOTYPE RESISTANT TO TRIAZINE AND ALS-INHIBITINGHERBICIDES

Author
item FOES, MATTHEW - UNIV OF ILLINOIS
item LIU, LIXIN - UNIV OF ILLINOIS
item STOLLER, EDWARD
item WAX, LOYD
item TRANEL, PATRICK - UNIV OF ILLINOIS

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Several growers in Illinois have reported that several class of herbicides that normally control kochia in corn and soybean fields failed to give adequate control. This observation lead us to suspect that this kochia has developed resistance to the herbicides. We conducted greenhouse studies that confirmed the hard-to-control kochia was indeed resistant to the ALS (acetolactase synthase)-inhibiting herbicides imazethapyr, thifensulfuron, and chlorsulfuron as well as the photoythesis-inhibiting herbicide atrazine. Our lab studies proved that both resistances were due to changes at the sites of action in the plant that rendered the herbicides ineffective. Further studies using molecular techniques showed the exact locations on the genes that caused the changes in the enzymes at the sites of herbicide action. Results of the study provide valuable information to growers, extension personnel and researchers that are involved in resistance physiology and weed management.

Technical Abstract: A kochia biotype from McDonough County, Illinois was suspected to be resistant to both triazine and acetolactate synthase-(ALS-)inhibiting herbicides. We performed greenhouse and laboratory experiments to confirm, quantify and determine the molecular basis of multiple herbicide resistance in this biotype. Whole plant phytotoxicity assays confirmed that the biotype was resistant to triazine (atrazine), imidazolinone (imazethapyr), and sulfonylurea (thifensulfuron and chlorsulfuron) herbicides. Relative to a susceptible kochia biotype, resistance to these herbicides ranged from 500- to >28,000-fold. The kochia biotype from McDonough County also displayed high levels of resistance (2000- to 9000-fold) to ALS-inhibiting herbicides in in vivo ALS enzyme assays, indicating that resistance to these herbicides was site-of-action mediated. Results from chlorophyll fluorescence assays indicated that triazine resistance was also site-of-action mediated. Foliar applications of atrazine had little or no effect on photosynthesis in the resistant biotype even when atrazine concentrations were several magnitudes higher than that needed to inhibit photosynthesis in the susceptible biotype. A region of the gene encoding the D1 protein of photosystem II and all of the open reading frame of the gene encoding ALS were sequenced and compared between the resistant and susceptible biotypes. Resistance to triazine and ALS-inhibiting herbicides int eh kochia biotype from McDonough County was conferred by, respectively, a glycine for serine substitution at residue 264 of the D1 protein and a leucine for tryptophan substitution at residue 570 of ALS.