Triazine Resistance in a Biotype of Wild Radish (Raphanus raphanistrum) in Australia¹

Abstract

This study documents the first case of triazine resistance in wild radish and the resistance mechanism involved. The high survival (57 to 97%) of the resistant (R) biotype progeny plants treated at a rate four times higher than the commonly recommended rate of simazine or atrazine clearly established that the R biotype plants were resistant to triazines. All the plants of the susceptible (S) biotype plants were killed when treated at half the commonly recommended rate of atrazine (0.5 kg/ha) or simazine (0.25 kg/ha). The dry weight of the S biotype was reduced by 89 to 96% at the commonly recommended rate of atrazine or simazine, while the dry weight of the R biotype plants was reduced by only 36 to 54% even when treated at a rate four times higher than the commonly recommended rate of atrazine or simazine. The growth-reduction–ratio values indicated that the R biotype progeny plants were 105 and 159 times more resistant to atrazine and simazine, respectively, than the S biotype plants. Leaf chlorophyll fluorescence yield was reduced by 97% in the S biotype 24 h after application of triazine compared with only 9% reduction in the R biotype, indicating that the resistance mechanism involved is target-site based. The R biotype was effectively controlled by herbicides of different modes of action.

The biology of Canadian weeds. 132. Raphanus raphanistrum L.

“…Triazine-resistant wild radish biotypes were killed at the 2-3 leaf stage by 2,4-D at 0.50 kg ha -1 , glyphosate at 0.46 kg ha -1 , and paraquat at 0.25 kg ha -1 , and well-controlled by chlorsulfuron at 0.015 kg ha -1 (86-95% control), metosulam at 0.05 kg ha -1 (85-95% control) and diflufenican at 0.50 kg ha -1 (97-100% control) (Hashem et al 2001b).…”

“…In addition, a three-to five-fold higher ALS-specific activity was observed in the R biotypes and may affect the resistance level. The first triazine-R biotype was reported in 1999 from a wheat/narrow-leafed lupin/triazine-tolerant canola rotation where triazines had been applied annually for 13 yr (Hashem et al 2001b).…”

Broad resistance to acetohydroxyacid-synthase-inhibiting herbicides in feral radish (Raphanus sativus L.) populations from Argentina

“…In the last decade, the number of herbicide‐resistant biotypes of Raphanus spp. has increased, including those of R. raphanistrum with cross‐resistance to acetohydroxyacid synthase (AHAS)‐inhibiting herbicides from Australia, South Africa and Brazil and with multiple resistance across several modes of action from Western Australia . A biotype of feral radish with herbicide resistance to AHAS‐inhibiting herbicides was reported in Brazil, Chile and Argentina …”

Detection of resistance to acetolactate synthase inhibitors in weeds with emphasis on DNA‐based techniques: a review

“…Resistance can be detected by placing seeds in direct contact with a herbicide prior to germination. An ALS inhibitor‐resistant wild radish population was successfully diagnosed by soaking seeds in metosulam or triasulfuron for 24 h prior to sowing in sand 35. The diagnosis of resistance was 3 weeks quicker than with a conventional bioassay.…”