title: Multiple-herbicide resistance in Echinochloa crus-galli var. formosensis, an allohexaploid weed species, in dry-seeded rice.
abstract: Biotypes of Echinochloa crus-galli var. formosensis with resistance to cyhalofop-butyl, an acetyl-CoA carboxylase (ACCase) inhibitor, have been found in dry-seeded rice fields in Okayama, Japan. We collected two lines with suspected resistance (Ecf27 and Ecf108) from dry-seeded rice fields and investigated their sensitivity to cyhalofop-butyl and other herbicides. Both lines exhibited approximately 7-fold higher resistance to cyhalofop-butyl than a susceptible line. Ecf108 was susceptible to penoxsulam, an acetolactate synthase (ALS) inhibitor. On the other hand, Ecf27 showed resistance to penoxsulam and two other ALS inhibitors: propyrisulfuron and pyriminobac-methyl. The alternative herbicides butachlor, thiobencarb, and bispyribac-sodium effectively controlled both lines. To examine the molecular mechanisms of resistance, we amplified and sequenced the target-site encoding genes in Ecf27, Ecf108, and susceptible lines. Partial sequences of six ACCase genes and full-length sequences of three ALS genes were examined. One of the ACCase gene sequences encodes a truncated aberrant protein due to a frameshift mutation in both lines. Comparisons of the genes among Ecf27, Ecf108, and the susceptible lines revealed that none of the ACCases and ALSs in Ecf27 and Ecf108 have amino acid substitutions that are known to confer herbicide resistance, although a single amino acid substitution was found in each of three ACCases in Ecf108. Our study reveals the existence of a multiple-herbicide resistant biotype of E. crus-galli var. formosensis at Okayama, Japan that shows resistance to cyhalofop-butyl and several ALS inhibitors. We also found a biotype that is resistant only to cyhalofop-butyl among the tested herbicides. The resistance mechanisms are likely to be non-target-site based, at least in the multiple-herbicide resistant biotype.
authors: Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; Crop Production Systems Division, NARO Agricultural Research Center, 3-1-1 Kannondai, Tsukuba 305-8666, Japan.
authors: Satoshi
authors: S
authors: Iwakami
authors: The Japan Association for Advancement of Phyto-Regulators, 860 Kashiwada-cho, Ushiku 300-1211, Japan.
authors: Masato
authors: M
authors: Hashimoto
authors: Crop Production Systems Division, NARO Agricultural Research Center, 3-1-1 Kannondai, Tsukuba 305-8666, Japan.
authors: Ken-ichi
authors: K
authors: Matsushima
authors: Crop Production Systems Division, NARO Agricultural Research Center, 3-1-1 Kannondai, Tsukuba 305-8666, Japan.
authors: Hiroaki
authors: H
authors: Watanabe
authors: The Japan Association for Advancement of Phyto-Regulators, 860 Kashiwada-cho, Ushiku 300-1211, Japan.
authors: Kenshiro
authors: K
authors: Hamamura
authors: Crop Production Systems Division, NARO Agricultural Research Center, 3-1-1 Kannondai, Tsukuba 305-8666, Japan. Electronic address: uchino@affrc.go.jp.
authors: Akira
authors: A
authors: Uchino
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism; D000103:Acetyl-CoA Carboxylase / Q000235:genetics / Q000378:metabolism; D002073:Butanes / Q000494:pharmacology*; D031747:Echinochloa / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D009570:Nitriles / Q000494:pharmacology*; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D057685:Plant Weeds / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*
chemical_list: D002073:Butanes; D006540:Herbicides; D009570:Nitriles; D010940:Plant Proteins; C501583:cyhalofop-butyl; D000095:Acetolactate Synthase; D000103:Acetyl-CoA Carboxylase
keywords: ACCase; ALS; Non-target-site-based resistance; Taiwan barnyard grass