耳叶水苋对乙酰乳酸合成酶抑制剂的抗性及其分子机制初探

近年来长江下游地区稻田耳叶水苋Ammannia arenaria H.B.K.危害十分严重。采用盆栽法首次测定了耳叶水苋对苄嘧磺隆等药剂的抗性水平,同时分析了其抗性和敏感种群间乙酰乳酸合成酶(ALS)基因的DNA序列及其RNA表达差异。结果表明:采自浙江嘉兴(JX110)、江苏苏州(JS039)、浙江宁波(NB0143-05)和安徽广德(AH014)的耳叶水苋生物型对苄嘧磺隆的抗性指数(RI)分别为67.90、17.59、44.63和8.37,对苄嘧磺隆表现出中高水平抗性的生物型对五氟磺草胺、双草醚及咪唑乙烟酸也产生了低水平的抗性。获得了耳叶水苋ALS基因全长核苷酸序列2235 bp,编码667个氨基酸,仅发现NB0143-05等3种抗性生物型ALS酶的氨基酸序列非保守区第93位的亮氨酸被脯氨酸取代。然而,NB0143-05的ALS酶对ALS抑制剂的敏感性大幅度降低(RI 37.04),且在苄嘧磺隆处理后4 d的ALS基因表达量是敏感生物型(HZ001)的1.86倍。这表明,ALS酶对药剂的敏感性降低以及被苄嘧磺隆诱导后ALS基因表达量显著增加,很可能是耳叶水苋生物型NB0143-05对ALS抑制剂产生抗性的原因。

Resistance and its resistant molecular mechanism ofAmmannia arenaria to ALS inhibiting herbicides

In recent years, Ammannia arenaria H.B.K. has become seriously harmful weed in paddy fields in the lower reach of Yangtze River plain. The resistance level of the biotypes of A. arenaria to four groups of ALS inhibiting herbicides including bensulfuron-methyl (BSM) were investigated by the method of seedling treatment. The DNA sequence and the expression of the ALS gene of the weed were analyzed with fluorescence quantitative PCR technique. The results showed that the resistance index (RI) of four A. arenaria biotypes including JX110 (Jiaxing, Zhejiang), JS039 (Suzhou, Jiangsu), NB0143-05 (Ningbo, Zhejiang) and AH014 (Guangde, Anhui) to BSM were 67.90, 17.59, 44.63 and 8.37, respectively. The biotypes exhibiting medium or high levels of resistance to BSM had evolved low level resistance to penoxsulam, bispyribac-sodium and imazethapyr. The full length sequence (2 235 bp) of the ALS gene which codes for 667 amino acids was cloned. Only the 93th leucine was substituted by proline in the amino acid sequence of the variable region of ALS in those three resistant biotypes including NB0143-05. However, the susceptibility of ALS enzyme from the biotype NB0143-05 to BSM decreased (RI 37.04) significantly, and its ALS gene expression was 1.86 times higher than that of sensitive biotype (HZ001) as induced by BSM. This indicated that the susceptibility decreasing of ALS enzyme to herbicide and the significant increasing of ALS gene expression after BSM induction might contribute to the resistance of A. arenaria (NB0143-05) to ALS inhibiting herbicides.