Skip to main content
ARS Home » Research » Publications at this Location » Publication #68317
Title: USING THE IN VIVO ALS ASSAY FOR IDENTIFYING HERBICIDE-RESISTANT WEEDS

Author
item LOVELL, SARAH - UNIV OF ILLINOIS
item WAX, LOYD
item SIMPSON, DAVID - UNIV OF ILLINOIS
item MCGLAMERY, MARSHAL - UNIV OF ILLINOIS

Submitted to: Weed Technology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: We conducted greenhouse and laboratory experiments to evaluate the effectiveness of a new technique for determining whether or not a weed is resistant to herbicides that inhibit the ALS (acetolactate synthase) enzyme. Many of the common herbicides in use today kill weeds by inhibiting this enzyme, and there is considerable potential for spread of weed resistance. Biotypes of the weed kochia from Montana and Idaho that had been determined to be resistant to certain ALS herbicides by other methods were used in these tests. These biotypes were compared to susceptible biotypes of the same weed species. The new technique, using tissue from living plants, allowed us to determine resistance or susceptibility without destroying the plants, and perform the tests more quickly and efficiently than with previous methods. The results obtained compared favorably with results gained with other methods. Using the new in vivo assay, the Montana and Idaho biotypes were 490 and 70-fold more resistant to the herbicide chlorsulfuron, respectively, than were the susceptible biotypes with which they were compared. There was only a low level of cross resistance to the herbicide imazethapyr. We also found this new technique to be useful in determining degree of resistance of cocklebur biotypes to the herbicide imazaquin. These studies showed that the new in vivo assay can be used effectively for identification of resistant biotypes at several timings, as well as for determining the extent of cross resistance to other herbicides. These results should help researchers who are investigating weed resistance and personnel who are developing management strategies for resistant weeds.

Technical Abstract: An in vivo ALS assay was used to differentiate between susceptible and resistant kochia biotypes from Idaho and Montana. Furthermore, studies were conducted to determine the effect of the timing of herbicide application on ALS activity in resistant and susceptible cocklebur biotypes from Mississippi. When treated with chlorsulfuron, resistant kochia biotypes demonstrated 160- and 170-fold resistance at the whole plant level for the Idaho and Montana biotypes, respectively, when compared to susceptible biotypes. Using the in vivo ALS assay, the Montana and Idaho biotypes had 490- and 70-fold resistance, respectively, based on I-50 results. The biotypes demonstrated a low level of cross resistance to imazethapyr at the enzyme level. Resistant cocklebur biotypes showed approximately a 200-fold resistance factor at 6 and 24 HAT compared with susceptible biotypes. This research demonstrated that the in vivo assay can be effectively used to identify resistant biotypes at several timings, as well as determine the extent of cross resistance.