Cross-resistance to imidazolinone herbicides in chlorsulfuron-resistant Raphanus raphanistrum.
Raphanus raphanistrum L has evolved widespread resistance to sulfonylureas in the Western Australia (WA) wheat belt. With the introduction of imidazolinone-tolerant (IT) wheat (Tritcum aestivum L) and IT canola (Brassica napus L) in the WA wheat belt, it is important to understand the status of cross-resistance in this weed to sulfonylurea and imidazolinone (Imi) herbicides. A study was conducted to examine cross-resistance between chlorsulfuron and Imi herbicides (a mixture of imazapic and imazapyr) in 46 R raphanistrum populations collected from across the WA wheat belt. Plants were treated with herbicides and assessed for phytotoxicity under glasshouse conditions. Of the 46 R raphanistrum populations, 32 were resistant to chlorsulfuron and four were resistant to imazapic + imazapyr. Of the 70% chlorsulfuron-resistant populations, 13% showed cross-resistance to imazapic + imazapyr. However, the cross-resistant populations treated with imazapic + imazapyr showed a lower resistance level than the chlorsulfuron-treated populations. These results suggest that weed populations with such cross-resistance will not be controlled effectively by Imi herbicides. Although the resistance levels of the cross-resistant populations to Imi herbicides were low, the cross-resistance levels of R raphanistrum should be determined before growing IT crops, particularly IT canola.
Hashem
Abul
A
Department of Agriculture, Centre for Cropping Systems, PO Box 483, Northam, Australia 6401. ahashem@agric.wa.gov.au
Dhammu
Harmohinder S
HS
D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D006540:Herbicides / Q000494:pharmacology* / Q000633:toxicity; D007093:Imidazoles / Q000494:pharmacology / Q000633:toxicity; D009525:Niacin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000633:toxicity; D009539:Nicotinic Acids / Q000494:pharmacology / Q000633:toxicity; D031224:Raphanus / Q000187:drug effects* / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology*; D014227:Triazines / Q000494:pharmacology*
D006540:Herbicides; D007093:Imidazoles; D009539:Nicotinic Acids; D013449:Sulfonamides; D014227:Triazines; D009525:Niacin; C076656:imazapyr; C481028:imazapic; C037137:chlorsulfuron