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ARS Home » Midwest Area » Morris, Minnesota » Soil Management Research » Research » Publications at this Location » Publication #125152
Title: GIANT FOXTAIL (SETERIA FABERI) SEEDLING ASSAY FOR RESISTANCE TO SETHOXYDIM

Author
item RETRUM, JULIE - UNIVERSITY OF MINNESOTA
item Forcella, Frank

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2002
Publication Date: 4/1/2002
Citation: RETRUM, J.B., FORCELLA, F. GIANT FOXTAIL (SETERIA FABERI) SEEDLING ASSAY FOR RESISTANCE TO SETHOXYDIM. WEED TECHNOLOGY. 2002. V. 26. P. 464-466.

Interpretive Summary: Repeated use of herbicides, such as Poast, cause populations of some weed species to develop resistance. Detecting resistance can be time- consuming and expensive. Consequently, we developed a simple test for detecting resistance to Poast (and similar herbicides) in giant foxtail, which is the most important weed in the Corn Belt. The test involves placing sprouted seeds on blotter paper soaked in a solution of 10 mg/L of sethoxydim, which is the active ingredient in Poast, and measuring the change in shoot growth after 6 days at 21 deg C. If the shoots grew 30 mm or more, then the seedling is resistant to Poast. The value of this simple bioassay is that it allows agrichemical companies and other scientists to test for resistance quickly using readily available and inexpensive tools.

Technical Abstract: Repeated application of ACCase-inhibitor herbicides may select for resistant weed populations, making a rapid and reliable seedling bioassay a useful tool. Such a bioassay was developed to determine shoot and root responses of giant foxtail seedlings to sethoxydim. Known susceptible (S) and resistant (R) giant foxtail seedlings were exposed to a sethoxydim dilution series in petri dishes and were measured for root and shoot growth at 3 and 6 days after treatment (DAT). A bioassay concentration of 10 mg/L sethoxydim easily discriminated between S and R biotypes of giant foxtail at 6 DAT, with R:S shoot and root growth ratios of about 3 and 10, respectively.