High Frequency of Chlorsulfuron-Resistant Wild Radish (Raphanus raphanistrum) Populations across the Western Australian Wheatbelt1

Abstract

In 1998, field populations of wild radish suspected of being resistant to chlorsulfuron were collected and screened for resistance to this herbicide using the Quick-Test technique. This test successfully identified chlorsulfuron-resistant populations of wild radish. Detailed dose–response experiments with the progeny of these populations confirmed their resistance and validated the use of the Quick-Test for a dicot species. Subsequently in 1999, a random survey was conducted employing this test to establish the current extent of chlorsulfuron resistance in wild radish populations. The survey covered more than 200 fields in the northern, central, and eastern wheatbelt regions of Western Australia. Wild radish plants were collected from wheat crops in 133 of these fields. The Quick-Test method was used to screen these plants with the acetolactate synthase (ALS)-inhibiting herbicide chlorsulfuron. Overall, 21% of randomly collected wild radish populations were found to be resistant to chlorsulfuron. Nomenclature: Chlorsulfuron; wheat, Triticum aestivum L.; wild radish, Raphanus raphanistrum L. Additional index words: Herbicide resistance, Quick-Test, resistance survey. Abbreviations: ALS, acetolactate synthase; WA, Western Australia.