Barnyardgrass [Echinochloa crus-galli(L.) P. Beauv] is the foremost weed in rice (Oryza sativaL.) systems, and its control is crucial to successful rice production. Quinclorac, a synthetic auxin herbicide, has been used effectively to manageE. crus-galli. However, occurrences of quinclorac-resistant genotypes are frequently reported, and its resistance evolution has led to questions about the continued utility of quinclorac for grass control. Identification of the resistance mechanism(s) of resistant genotypes will facilitate development of integrated weed management strategies that sustain quinclorac use for management ofE. crus-galli. We evaluated the responses to quinclorac of two contrasting genotypes: E7 (resistant, R) and LM04 (susceptible, S). Quinclorac induced ethylene and cyanide biosynthesis in the S-genotype. Both genotypes responded similarly to an increasing application of exogenous 1-carboxylic acid aminocyclopropane (ACC) and potassium cyanide, and their growth was inhibited at higher doses. The key mechanism for cyanide (HCN) detoxification in plants, β-cyanoalanine synthase (β-CAS) activity, was evaluated in both genotypes, and no significant difference was observed in the basal activity. However, quinclorac significantly induced β-CAS–like activity in the S-genotype, which is consistent with the increased synthesis of ethylene and cyanide. This work suggests that the resistance to quinclorac of the E7 R-genotype is likely related to an alteration in the auxin signal transduction pathway, causing a lower stimulation of ACC synthase and, therefore, limited synthesis of ethylene and HCN after quinclorac treatment.

中文翻译：

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在乌拉圭的抗喹氯酸稗 (Echinochloa crus-galli) 中观察到乙烯和氰化物合成的有限诱导

稗草 [稗草(L.) P. Beauv] 是水稻中最重要的杂草（水稻L.) 系统，其控制对水稻生产的成功至关重要。喹氯酸是一种合成生长素除草剂，已被有效用于管理E. crus-galli. 然而，经常报道出现耐喹氯酸的基因型，其抗性进化导致了关于喹氯酸在草地控制中的持续效用的问题。确定抗性基因型的抗性机制将促进综合杂草管理策略的发展，以维持喹氯酸用于管理E. crus-galli. 我们评估了两种对比基因型对喹氯酸的反应：E7（抗性，R）和 LM04（易感，S）。Quinclorac 在 S 基因型中诱导乙烯和氰化物生物合成。两种基因型对外源性 1-羧酸氨基环丙烷 (ACC) 和氰化钾的应用增加的反应相似，并且它们的生长在较高剂量下受到抑制。在两种基因型中评估了植物中氰化物（HCN）解毒的关键机制，即β-氰丙氨酸合酶（β-CAS）活性，并且在基础活性方面没有观察到显着差异。然而，喹氯酸显着诱导 S 基因型中的 β-CAS 样活性，这与乙烯和氰化物的合成增加一致。