Studies on herbicidal carbamoyltetrazolinone derivatives: Selection of fentrazamide

1-Phenyl-5(4 H )-4-dialkylcarbamoyltetrazolinones represent a new class of herbicides that are active against barnyardgrass ( Echinochloa spp.) in paddy fields. To select the most favorable compound as a paddy herbicide, herbicidal activity and selectivity of the carbamoyltetrazolinone compounds to transplanted rice were determined in greenhouse tests. Higher herbicidal activities were associated with the compounds having a 2-Cl- or 2-Cl-6-Me-substituted or an unsubstituted phenyl ring, and a combination of C_2–3 linear alkyl group and a C₄ branched-chain alkyl or a C_5–6 cycloalkyl group on the nitrogen atom in the carbamoyl structure. In addition, the compounds carrying a total of seven to nine carbon atoms in the substituents on the carbamoyl nitrogen exhibited a good selectivity between barnyardgrass and transplanted rice plants. From the results of soil thick-layer chromatography, the good crop compatibility of carbamoyltetrazolinones was correlated to the mobility of the compounds in paddy soil. The investigation resulted in the selection of an excellent compound, 4-(2-chlorophenyl)- N -cyclohexyl- N -ethyl-4,5-dihydro-5-oxo-1 H -tetrazole-1-carboxamide (common name: fentrazamide), as a rice paddy herbicide for controlling barnyardgrass.     

Novel 3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2] benzopyran derivatives: synthesis of chiral glycol benzyl ether herbicides

Novel tricyclic 3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2]benzopyran (TFB) derivatives were synthesized, and their herbicidal activities were elucidated. They were synthesized from D-glucose as a natural chiral source. The formation of the TFB skeleton was achieved by a Friedel-Crafts type intramolecular cyclization of methyl 5-deoxy-2,3-O-dibenzyl-5-C-methyl-D-xylofranosides. The intramolecular cyclization was dependent upon the electronic effects of the substituents at the C-2 benzyloxy group of methyl xylofranosides. Some TFBs exhibited a remarkable herbicidal activity to annual paddy weeds, such as Echinochloa sp, without injury to the rice.     

水稻与无芒稗的竞争和化感作用

用差时播种共培法的改进方法对105份水稻、6份巴西陆稻进行了化感作用抗稗草评价。 结果表明长匡7号、P4、Kogyoku、 IR27316、 Milyang 54和巴西陆稻AJ035等材料对无芒稗有较好的化感作用。盆栽研究表明,谷梅2 号、中156对无芒稗的抑制作用显著大于对照,而化感作用材料TN1对无芒稗的抑制作用与无化感作用材料秀水63无显著差异。中156的抑制作用强与其株高有关,而谷梅2号对无芒稗的抑制作用强主要在于其本身的化感作用。随着水稻密度增加,无芒稗受抑程度加剧,化感作用水稻对稗草根部的抑制似乎要比无化感作用水稻强。TN1对无芒稗的化感作用不明显,可能是由于对不同生态的稗的作用不同之故。     

Q刈割对稗草生物量生殖分配及生长特性的影响

为了解稗草(Echinochloa crusglli(L)Beauv.)在不同刈割强度下资源分配特点,对其进行了3种刈割强度处理,分别测定了不同刈割强度条件下稗草的根、茎、叶、花(果)器官的生物量、株高、分蘖数,并对生物量和各器官生物量分配比例进行了对比分析.结果表明:从盛花期到结实期,在各处理条件下,根、茎器官生物量和分配比例下降,生殖器官生物量和分配比例上升,叶器官无明显变化规律;盛花期生殖分配比例为:轻度刈割(Y1)＞对照≈重度刈割(Y3)＞中度刈割(Y2),结实期生殖分配比例为:对照～轻度刈割(Y1)≈重度刈割(Y3)＞中度刈割(Y2);株高表现为轻度刈割促进其绝对高度的增加,而在中度及重度刈割条件下,表现为抑制作用;在重度刈割条件下,单株分蘖数与刈割强度呈正相关.     

60Co γ射线诱发谷稗和御谷的辐射生物学效应研究

研究利用60Co γ射线以10、20、30 Gy的剂量处理谷稗Echinochloa crusgalli和御谷Pennisetum glaucum 2种牧草种子,以未经处理的种子作为对照,进行了发芽、幼苗生长和根尖细胞染色体畸变的研究。结果表明,60Co γ射线辐照抑制了谷稗和御谷的种子萌发,不同程度刺激了幼苗的苗高增高。60Co γ射线辐照后,谷稗和御谷的根尖细胞中出现了单微核、双微核、单桥、双桥等各类的染色体畸变类型。随着60Co γ射线辐射剂量的增大,微核和染色体畸变率也逐渐增大,在30 Gy时达到最大。谷稗对于60Co γ射线辐射的敏感性要大于御谷。     

Quinclorac resistance: a concerted hormonal and enzymatic effort in Echinochloa phyllopogon

BACKGROUND: 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. RESULTS: Resistant to susceptible (S) GR₅₀ (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. CONCLUSION: 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. Copyright © 2011 Society of Chemical Industry     

Isolation and expression of genes for acetolactate synthase and acetyl-CoA carboxylase in Echinochloa phyllopogon, a polyploid weed species

BACKGROUND: Target‐site resistance is the major cause of herbicide resistance to acetolactate synthase (ALS)‐ and acetyl‐CoA carboxylase (ACCase)‐inhibiting herbicides in arable weeds, whereas non‐target‐site resistance is rarely reported. In the Echinochloa phyllopogon biotypes resistant to these herbicides, target‐site resistance has not been reported, and non‐target‐site resistance is assumed to be the basis for resistance. To explore why target‐site resistance had not occurred, the target‐site genes for these herbicides were isolated from E. phyllopogon, and their expression levels in a resistant biotype were determined. RESULTS: Two complete ALS genes and the carboxyltransferase domain of four ACCase genes were isolated. The expression levels of ALS and ACCase genes were higher in organs containing metabolically active meristems, except for ACC4, which was not expressed in any organ. The differential expression among examined organs was more prominent for ALS2 and ACC2 and less evident for ALS1, ACC1 and ACC3. CONCLUSION: E. phyllopogon has multiple copies of the ALS and ACCase genes, and different expression patterns were observed among the copies. The existence of three active ACCase genes and the difference in their relative expression levels could influence the occurrence of target‐site resistance to ACCase inhibitors in E. phyllopogon. Copyright © 2012 Society of Chemical Industry     

Evaluation of rice allelopathy in hydroponics

The inhibitory activity of water extracts from the shoots and roots of three rice cultivars, Taichung native 1 (TN1) and IAC165 (both allelopathic rice) and AUS196 (non-allelopathic rice), grown in hydroponics was evaluated. The release of germination inhibitors by allelopathic rice plants into hydroponic solution was also determined with freshly collected solution and XAD-4 resin desorbate. The degree of the inhibition was quantified in terms of root growth in Echinochloa colona, Echinochloa crus-galli, Echinochloa crus-galli var. oryzicola, Triantema portulacastrum and Lactuca sativa. The allelopathic activity of rice was species specific, and depended on source and concentration. Root length of all test species was inhibited by the different concentrations of shoot extract of allelopathic and non-allelopathic rice. However, of the three cultivars, TN1 showed higher inhibition than IAC165 and AUS196 in all test species. Water extracts of shoots and roots significantly inhibited root growth in E. crus-galli but the shoot extract gave a greater inhibitory effect on E. crus-galli than the root extract. Root exudate of TN1 inhibited root elongation of E. crus-galli from 2 weeks after transplanting (WAT) and the inhibition continued for 4 WAT. The results confirmed the previous finding of a laboratory bioassay that the TN1 had allelopathic activity and produced allelochemicals that inhibit growth of some weed species.     

稗草休眠特性及其解除

研究了稗草在不同环境条件下的休眠特性及其解除方法。结果表明,稗草种子在成熟后都将进入休眠,不同环境条件下其休眠期不一样。2004年7月采集的稗草种子在地下贮存条件下5个月就能打破休眠,且持续6个月一直处于休眠解除状态。室内常温条件下需12个月才能打破休眠,而冰箱中贮存12个月不能解除稗草种子的休眠。1 000.0 mg/L赤霉酸浸泡240 h和硫酸浸泡10-20 min均能解除稗草种子的休眠,但其他处理不能有效解除稗草种子的休眠。     

Assessment of allelopathic potential of barnyard grass (Echinochloa crus-galli) on rice (Oryza sativa L.) cultivars

Laboratory, greenhouse and field studies were conducted to assess the allelopathic potential of 44 rice cultivars (Oryza sativa L.) on barnyard grass (Echinochloa crus-galli P. Beauv. var. oryzicola Ohwi). Rice cultivars exhibited marked differences in the inhibition of barnyard grass growth and development. In the laboratory, Gin shun rice cultivar extracts exhibited the greatest activity on the weed seedling growth, reducing dry weight by 61%, while Kasarwala mundara cultivar extracts exhibited the greatest activity on seed germination, reducing germination by 23% and germination speed by 46%. In a greenhouse study of a residue mixture, the Philippine 2 cultivar showed the greatest inhibition percentage on seedling emergence (57%), total seedling length (74%) and dry weight (73%). In the field study, the Juma 10 cultivar demonstrated the most inhibitory effect by reducing barnyard grass tiller number (80%), leaf area (49%) and leaf (61%) and stem (74%) dry weight (68%). These results suggest that there are differences among the varieties for allelopathic inhibition of barnyard grass, and that the development of barnyard grass suppressive rice cultivars that have greater allelopathic potential may be possible.