Acetohydroxyacid synthase (AHAS, E.C. 2.2.1.6) is the target site of several herbicide classes including imidazolinones. Imidazolinone resistance in wheat is conferred by two major genes AhasL-D1 and AhasL-B1. The objective of this work was to evaluate the in vitro and in vivo AHAS activity and plant growth in response to imazamox of nine wheat cultivars. Dose-response curves for two-gene resistant cultivars were significantly different from the single-gene resistant and susceptible cultivars in the in vitro AHAS assay. Resistance levels at the in vivo AHAS and whole-plant assays for resistant cultivars were >10-fold higher than susceptible cultivars. Moreover, in vivo dose-response curves showed differences among cultivars with the same number of resistance genes. It was concluded that in the in vitro AHAS assay cultivar variability was due to differences in target-site sensitivity while the in vivo AHAS assay reflected the resistance at whole-plant level. Both in vitro and in vivo AHAS dose-response curves could be useful tools when exploring mechanisms involved in imidazolinone resistance in different wheat genetic backgrounds and for the selection of higher resistant genotypes.

中文翻译：

---

小麦对Izamox抗性的品种变异：对早期选择的酶促测定的认识。

乙酰羟酸合酶（AHAS，EC 2.2.1.6）是包括咪唑啉酮在内的几种除草剂类别的目标位点。小麦对咪唑啉酮的抗性由两个主要基因AhasL-D1和AhasL-B1赋予。这项工作的目的是评估对9个小麦品种的Izamox的体外和体内AHAS活性和植物生长。在体外AHAS分析中，两基因抗性品种的剂量-反应曲线与单基因抗性和易感品种显着不同。在体内AHAS和全株试验中，抗性品种的抗性水平比易感品种高10倍以上。此外，体内剂量-反应曲线显示了具有相同数量抗性基因的品种之间的差异。结论是，在体外AHAS分析中，品种变异性是由于靶位敏感性的差异所致，而体内AHAS分析则反映了全株水平的抗性。在探索不同小麦遗传背景下咪唑啉酮抗性相关机制以及选择更高抗性基因型时，体外和体内AHAS剂量反应曲线都可能是有用的工具。