Different cross-resistance patterns to AHAS herbicides of two tribenuron-methyl resistant flixweed (Descurainia sophia L.) biotypes in China

Flixweed (Descurainia sophia L.) is a troublesome weed in winter wheat fields in China. Two flixweed accessions, HB08 and HB16 with a Pro-197-Leu and Pro-197-Ser AHAS-mutation respectively, have evolved very high levels resistance to sulfonylurea (SU) herbicide, tribenuron-methyl. Cross resistance of HB08 and HB16 to AHAS herbicides of SU, imidazolinone (IMI), triazolopyrimidine (TP) and pyrimidinyl-thiobenozoate (PTB) families was investigated by dose-response experiments. In addition, the effects of AHAS herbicides on the activity of AHAS extracted from HB08 and HB16 plants were evaluated. HB16 exhibited cross resistance to SU herbicides halosulfuron-methyl and triasulfuron, TP herbicides flumetsulam and penoxsulam, but displayed more sensitivity to IMI herbicide imazethapyr. By contrast, HB08 only showed cross resistance to SU herbicides halosulfuron-methyl and triasulfuron. The in vitro sensitivity of AHAS to AHAS herbicides is consistent with the results of dose-response experiments and the estimated Pearson's r values for HB08 and HB16 are 0.996 and 0.912 respectively. These indicated that altered AHAS sensitivity was responsible mainly for cross resistance patterns observed in the two resistant biotypes. (C) 2014 Elsevier Inc. All rights reserved.