Weed Science Program, Department of Plant Sciences, University of California, Davis, CA, USA.
Pest Manag Sci. 2012 Jan;68(1):108-15. doi: 10.1002/ps.2230. Epub 2011 Jun 29.
Quinclorac (3,7-dichloro-quinoline-carboxylic acid) is a selective herbicide widely used to control annual grasses and certain broadleaf weeds. Echinochloa phyllopogon (Stapf) Koss. is the most noxious grass weed in California rice fields and has evolved resistance to multiple herbicides with different modes of action. A quinclorac-resistant (R) E. phyllopogon biotype found in a Sacramento Valley rice field where quinclorac has never been applied was investigated.
Resistant to susceptible (S) GR(50) (herbicide rate for 50% growth reduction) ratios ranged from 6 to 17. The cytochrome P450 inhibitor malathion (200 mg L(-1)) caused R plants to become as quinclorac susceptible as S plants. Quinclorac rapidly (6 HAT) stimulated ethylene formation in S plants, but only marginally in R plants. Malathion pretreatment did not reduce ethylene formation by quinclorac-treated S and R plants. Activity of β-cyanoalanine synthase (β-CAS) in tissue extracts was 2-3-fold greater in R than in S plants, and incubation of shoot extracts with 1 mM malathion reduced β-CAS activity by 40% in both biotypes.
Resistance to quinclorac in R E. phyllopogon involved at least two mechanisms: (a) insensitivity along the response pathway whereby quinclorac induces ethylene production; (b) enhanced β-CAS activity, which should enable greater HCN detoxification following quinclorac stimulation of ethylene biosynthesis. This unveils new resistance mechanisms for this multiple-resistant biotype widely spread throughout California rice fields.
苯氧羧酸类除草剂精喹禾灵（3,7-二氯喹啉羧酸）是一种广泛用于防治一年生禾本科杂草和某些阔叶杂草的选择性除草剂。稗草（Echinochloa phyllopogon （Stapf） Koss.）是加利福尼亚稻田中最具危害性的杂草，已经对多种具有不同作用方式的除草剂产生了抗性。本研究调查了在加利福尼亚萨克拉门托山谷的一个从未使用过精喹禾灵的稻田中发现的一种抗精喹禾灵（R）稗草生物型。
抗性与敏感（S）GR50（抑制 50%生长的除草剂率）比值范围为 6 至 17。细胞色素 P450 抑制剂马拉硫磷（200mg/L）使 R 植株对精喹禾灵的敏感性与 S 植株相同。精喹禾灵在 S 植株中迅速（6HAT）刺激乙烯的形成，但在 R 植株中仅略有增加。马拉硫磷预处理并没有降低精喹禾灵处理的 S 和 R 植株的乙烯形成。组织提取物中的β-氰基丙氨酸合酶（β-CAS）活性在 R 植株中比 S 植株高 2-3 倍，在两种生物型中，用 1mM 马拉硫磷孵育芽提取物可使β-CAS 活性降低 40%。
稗草中对精喹禾灵的抗性至少涉及两种机制：（a）对精喹禾灵诱导乙烯产生的反应途径不敏感；（b）β-CAS 活性增强，这应该使在精喹禾灵刺激乙烯生物合成后，能够更好地进行 HCN 解毒。这揭示了加利福尼亚稻田中广泛传播的这种多抗性生物型的新抗性机制。
