Physiological responses of maize and sorghum to four different safeners for metazachlor

The ability of the herbicide safeners, BAS-145138 (1-dichloroacetyl-hexahydro-3,3,8a-trimethyl-pyrrolo(1,2a)pyrimidin-6(2H)-one), dichlormid (N,N-diallyl-2,2-dichloroacetamide), flurazole (phenylmethyl ester), and MG-191 (2-dichloromelhyl-2-methyl-1,3-dioxolane) for preventing metazachlor injury to maize (Zea mays L.) and sorghum (Sorghum bicolor L.) seedlings were compared with their effects on ¹⁴C-metazachlor metabolism to a glutathione (GSH) conjugate, effects on non-protein thiol contents (mainly GSH) and effects on Glutathione S-transferase (GST) activity in these two species. Sorghum shoot growth was reduced by 41% and maize shoot growth was reduced by 54%, by metazachlor concentrations in vermiculite nutrient culture of 0·6 μM and 7·5μM, respectively. In this system, all four compounds had significant activity as safeners for metazachlor in both sorghum and maize seedlings. BAS-145138 and flurazole were the most effective safeners in maize and sorghum, respectively. In the absence of safeners, the rate of non-enzymatic conjugation of metazachlor and GSH was much greater than the enzymatic rate. However, the rate of enzymatic conjugation of metazachlor with GSH was increased by safener treatment in both maize and sorghum. Safener effectiveness was highly correlated with increases in ¹⁴C-metazachlor uptake and metabolism in both species. Safener effectiveness was more highly correlated with safener effects on GST activity in maize or sorghum when ¹⁴C-metazachlor was used as the substrate than when the non-specific CDNB (1-chloro-2,4-dinitrobenzene) was used as the substrate. Safener effectiveness was also strongly correlated with safener effects on GSH levels in sorghum, but not in maize, possibly because of the greater importance of non-enzymatic conjugation of metazachlor with GSH in sorghum as compared to maize.     

除草剂安全剂作用机理研究进展

除草剂安全剂是一类可在不影响除草剂对靶标杂草活性的前提下,有选择性地保护作物免受除草剂伤害的特殊用途化合物,有关安全剂作用机理的研究对新安全剂的开发具有重要意义。目前关于除草剂安全剂的作用机理主要有4种观点:1）影响除草剂在作物体内的吸收和转运;2）与除草剂竞争靶标位点;3）影响靶标酶的活性;4）增强作物对除草剂的代谢。文章对近年来安全剂作用机理及安全剂对杂草的影响等研究进展进行了综述,并分析了当前存在的问题及未来的研究方向,旨在为深入研究安全剂的作用机理及新安全剂开发提供参考。     

Physiological interactions between the herbicide EPTC and selected analogues of the antidote naphthalic anhydride on two hybrids of maize

The efficacies of nine structural analogues of the herbicide antidote naphthalene-1,8-dicarboxylic acid anhydride (naphthalic anhydride, NA) for the protection of maize (Zea mays L. cv. DeKalb XL72AA and DeKalb XL67) against injury by the herbicide S-ethyl dipropyl(thiocarbamate) (EPTC) were elevated under greenhouse conditions. The chemical analogues of NA tested were: acenaphthenequinone (ACQ); 4-aminonaphthalene-1,8-dicarboxylic acid anhydride (NH₂NA); 1,8:4,5-naphthalenetetracarboxylic acid dianhydride (NDiA); naphthalene- 1,8-carboximide (NHNA); 4-chloronaphthalene-1,8-dicarboxylic acid anhydride (C1NA); biphenyl-2,2′-dicarboxylic acid anhydride (diphenic anhydride; DA); 2-phenylglutaric anhydride (PGA); phthalic anhydride (PHA); phenalen-1-one (PA). Pre-plant incorporated applications of EPTC at 2.2, 4.5, 6.7, and 9.0 kg ha^?1 were highly toxic to XL67 maize. Appreciable injury to XL72AA maize by EPTC was observed only with the high rates of EPTC (6.7 and 9.0 kg ha^?1). Of the analogues tested PGA and PA were very toxic and inhibited germination of both maize hybrids. NA, ACQ, NH₂NA, NDiA, NHNA, C1NA, DA, and PHA applied as seed dressings at 5.0 and 10 g per kg of seed offered satisfactory protection to XL72AA maize against EPTC rates higher than 6.7 kg ha^?1. The same antidotes significantly antagonised the EPTC activity against XL67 maize but the overall protection obtained was partial and not agronomically important. The presence of the dicarboxylic anhydride group and of at least one aromatic ring attached directly to the anhydride appeared to be essential for the exhibition of protective activity by the structural analogues of NA. NA was slightly toxic to both hybrids of maize and chlorination of NA increased the phytotoxicity of this molecule. A genetic component that is present in the thiocarbamate-tolerant XL72AA hybrid but absent from the thiocarbamate-susceptible XL67 hybrid of maize appeared to be important for the phytotoxic activity of EPTC and may be involved in the protective activity of NA and its structural analogues.     

除草剂中的安全剂研究进展

综述除草剂中安全剂的应用历史、国内外研究现状、分类、目前商业化种类及应用情况,较为系统地介绍了其作用机制,并展望了安全剂的发展前景。     

Adsorption-desorption studies of alachlor, metolachlor, EPTC, chlorothalonil and pirimiphos-methyl in contrasting soils

Five soils with different organic matter contents ranging from 0.48 to 10.4% were used to study the adsorption and desorption of alachlor, metolachor, EPTC, chlorothalonil and pirimiphos-methyl in batch experiments. The isotherm shapes according to Giles classification were S-type for alachlor, metolachlor and chlorothalonil, changing to L-type for the latter as the level of soil organic matter increased, and L-type for EPTC and pirimiphos-methyl. The adsorption isotherms fitted the Freundlich equation x/m = KfCe1/n. The Kf values increased with the increase of organic matter content. The amounts of pesticides adsorbed over a range of concentrations of 0.1-20 mg litre-1 reached 63.1% for alachlor, 69.2% for metolachlor, 89.3% for EPTC, 98.4% for chlorothalonil and 96.3% for pirimiphos-methyl. The increase of the amounts desorbed with acetone indicated that the sorption of organic compounds onto organic matter occurred principally via weak London-type induction forces, or dispersion forces which are characteristics of the physical adsorption process.     

磺酰脲类除草剂及其安全剂研究进展

本文简述了磺酰脲类除草剂的概况、长残留药害以及使用安全剂缓解残留药害的研究进展,并展望了磺酰脲类除草剂及其安全剂的发展前景。     

Comparative responses of selected corn (Zea mays L.) hybrids to EPTC and metolachlor

Eleven corn (Zea mays L.) hybrids were evaluated in terms of their growth response to treatment with a high rate (6.7 kg ha^?1) of the thiocarbamate herbicide, EPTC, and the chloroacetanilide herbicide, metolachlor. Most of the tested hybrids were more susceptible to treatment with metolachlor than EPTC. It was apparent that the degree of tolerance observed for one of these herbicides was not necessarily matched by a similar degree of tolerance to the other. No correlation between glutathione content and herbicide tolerance was observed for the 11 hybrids tested. A relationship between glutathione S–transferase (GST) activity and metolachlor tolerance was suggested by this study. In general, higher GST activities were characteristic of the more tolerant hybrids. The monooxygenase inhibitor, piperonyl butoxide (PBO), in combination with EPTC resulted in a synergistic effect on eight of the eleven tested hybrids. PBO acted synergistically in combination with metolachlor on only two hybrids and to a lesser extent than with EPTC. Soil treatment with the oxygen evolving compound, calcium peroxide, appeared to have an antagonistic effect on the growth response of ‘Northrup–King 9283’ corn treated with EPTC. In contrast the same treatment had a synergistic effect on the growth response of this hybrid to metolachlor. Both the synergism of EPTC by PBO and the antagonism by calcium peroxide are believed to be due to the importance of monooxygenase activity in the metabolism of EPTC. Tolerance to EPTC is consequently more likely to be influenced by oxidative reactions than is tolerance to metolachlor. Réponses comparées d'hybrides sélectionnés de mai's (Zea mays) a l'EPTC et au métolachlor Onze hybrides de mai's (Zea mays) ont étéétudiés en regard de leur croissance suite à un traitement à une dose é1evée (6.7 kg ha^?1) de 1'herbicide thiocarbamate, EPTC et de 1'herbicide chloroacétanilide, métolachlor. La plupart des hybrides testés étaient plus sensibles au métolachlor qu' à l'EPTC. II est apparu que le degré de tolérance observé pour 1'un de ces herbicides n'était pas nécessairement accompagné par un degré similaire de tolérance pour 1'autre. Aucune corrélation entre la teneur en glutathion et la tolérance herbicide n'a été observée pour les 11 hybrides testés. Une relation entre 1'activité de la glutathion S–trans–férase (GST) et la tolérance au métolachlor a été suggérée par cette étude. En général les activités GST plus élevées étaient caractéristiques des hybrides les plus tolérants. L'inhibiteur monooxygénase, le pipéronyl butoxide (BPO) en mélange avec l'EPTC a abouti a un effet synergique sur 8 des 11 hybrides testés. PBO a agis en synergic en mélange avec le métolachlor chez seulement 2 hybrides et à une échelle moindre qu'avec 1'EPTC. Un traitement du sol avec un composé oxygéné, du calcium peroxyde, est apparu avoir un effet antagoniste sur la croisance du mai's ‘Northrup–King 9283’ traitéà l'EPTC. Au contraire, le même traitement a eu un effet de synergie sur la croissance de cet hybride traité au métolachlor. Tant la synergie entre l'EPTC et le PBO, que l'antagonisme avec le calcium peroxidé semblent être liés à l'importance de l'activité monoxygenase dans le métabolisme de l'EPTC. La tolérance à l'EPTC est en conséquence plus étroitement influencée par les réactions oxydantes que la tolérance au métolachlor. Reaktion ausgewählter Mais-Hybriden (Zea mays L.) auf EPTC und Metolachlor Das Wachstum von 11 Mais-Hybriden (Zea mays L.) nach Behandlung mit einem hohen Aufwand (6,7 kg ha^?1) des Thiocarbamats EPTC und des Chloracetanilids Métolachlor. Es war deutlich, daß der Grad der Toleranz gegenüber einem dieser Herbizide nicht notwendigerweise dem bei dem anderen entsprach. Bei allen 11 Hybriden konnte keine Korrelation zwischen dem Glutathion-Gehalt und der Herbizidtoleranz gefunden werden. Auf Grund dieser Untersuchung wird eine Beziehung zwischen der Aktivität der Glutathion-S-Transferase (GST) und der Metolachlor-Toleranz angenommen, denn tolerantere Hybriden hatten im allgemeinen eine höhere GST-Aktivität. Der Monooxygenase-Hemmer Piperonylbutoxid (PBO) hatte zusammen mit EPTC eine synergistische Wirkung auf 8 der 11 Hybriden. Mit Metolachlor wirkte PBO synergistisch nur bei 2 Sorten und in geringerem Maße als mit EPTC. Eine Bodenbearbeitung mit dem sauerstoffabgebenden Calciumperoxid hatte offensichtlich eine antagonistische Wirkung auf das Wachstum von ‘Northrup-King 9283’ bei Behandlung mit EPTC. Im Gegensatz dazu wirkte dieselbe Behandlung dieser Hybride mit Metolachlor synergistisch. Es wird angenommen, daß sowohl der Synergismus von EPTC mit PBO als auch der Antagonismus mit Calciumperoxid für die Bedeutung der Monooxygenase-Aktivität für den Metabolismus von EPTC sprechen. Die Toleranz gegenüber EPTC ist deshalb wahrscheinlich mehr durch oxydative Reaktionen beeinflußt als die Toleranz gegenüber Métolachlor.     

Comparative metabolism of atrazine and EPTC in proso millet (Panicum miliaceum L.) and corn

The purpose of this study was to examine the differential activities of proso millet (Panicum miliaceum L.) and corn (Zea mays L.) with respect to atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine] and EPTC (S-ethyldipropyl thiocarbamate) metabolism. GSH-S-transferase was isolated from proso millet shoots and roots. When assayed spectrophotometrically using CDNB (1-chloro 2,4-dinitrobenzene) as a substrate, the shoot enzyme had only 10% of the activity of corn shoot enzyme while the root enzyme had 33% the activity of corn root enzyme. However, when proso millet shoot GSH-S-transferase was assayed in vitro using ¹⁴C-ring-labeled atrazine, it degraded the atrazine to water-soluble products at the same rate as the corn shoot enzyme. Incubation of excised proso millet and corn roots with [¹⁴C]EPTC indicated that uptake of EPTC was similar in both plants. However, proso millet metabolized the EPTC to water-soluble products at only half the rate of corn. Glutathione levels of proso millet roots were 35.9 μg GSH/g fresh wt, compared with 65.4 μg GSH/g fresh wt for corn. However, a 2.5-day pretreatment with R-25788 (N,N-diallyl-2-2-dichloroacetamide) elevated proso millet GSH levels to 62.7 μg GSH/g fresh wt. R-25788 did not elevate the activity of proso millet GSH-S-transferase, in contrast to its effects on corn. We conclude that differences in response to atrazine and EPTC in proso millet and corn are a result of their differential metabolism.     

Induction of wheat and maize glutathione S-transferase by some herbicide safeners and their effect on enzyme activity against butachlor and terbuthylazine

The expression of glutathione S-transferase (GST) activity in wheat and maize shoots was investigated in response to treatments with the herbicide safeners benoxacor, cloquintocet-mexyl, fenchlorazole-ethyl, fenclorim, fluxofenim and oxabetrinil. These safeners significantly enhanced the GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB) as a 'standard' substrate, with the exception of oxabetrinil in maize. The enhancements of GST (CDNB) activity were found to be concomitant with increases in V(max) (the reaction rate when the enzyme is fully saturated by the substrate) in wheat following cloquintocet-mexyl and fenchlorazole-ethyl treatments, and in maize following fenchlorazole-ethyl treatment. Otherwise, decreases in V(max) were observed in wheat and maize following fenclorim and fluxofenim treatments. With the exception of oxabetrinil, all the safeners significantly reduced the apparent K(M) (the substrate concentration required for 50% of maximum GST activity) of both wheat and maize GST. The V(max) and K(M) variations following safener treatments are discussed in terms of an increased expression of GST enzymes and an increased affinity for the CDNB substrate. The activity of wheat and maize GST was also assayed towards butachlor and terbuthylazine respectively; the results indicate the ability of cloquintocet-mexyl, fenchlorazole-ethyl and fluxofenim to enhance the enzyme activity in wheat and of benoxacor and fenchlorazole-ethyl to do so in maize.     

玉米耐旱性的调控研究

水分胁迫下通过一些调控措施可以提高玉米种子的萌发率，改善幼苗的生长状况，抑制保护酶活性的下降，减轻生物膜的伤害，增强玉米的耐旱性，从而提高玉米的产量。本文综述了近几年玉米耐旱性在施用抗旱剂、外源ABA、矿质营养等方面的调控研究，并对其研究前景提出了一些见解。     

Metabolism of EPTC in germinating corn: Sulfone as the true carbamoylating agent

Corn (Zea mays L. single cross hybrid Mv 620) was germinated in a petri dish with addition of carbonyl[¹⁴C]EPTC (S-ethyl-N,N-dipropylthiocarbamate). The shoots and roots of 4-day-old seedlings were crushed and extracted in 80% methanol. On the chromatogram of the extract three radioactive peaks were found. The main peak was identified as S-(N,N-dipropylcarbamoyl)-glutathione. For the comparison of carbamoylating ability [¹⁴C]EPTC, [¹⁴C]EPTC-sulfoxide, and [¹⁴C]EPTC-sulfone were incubated with glutathione. Only EPTC-sulfone reacted in the 10-day incubation time. In aquatic solutions EPTC and EPTC-sulfoxide proved to be stable during the 10 days compared to EPTC-sulfone which quickly degraded, S-(N,N-Dipropylcarbamoyl)-glutathione was converted to S-(N,N-dipropylcarbamoyl)-cysteine in corn shoot homogenate. [¹⁴C]EPTC, [¹⁴C]EPTC-sulfoxide and [¹⁴C]EPTC-sulfone were added to corn shoot homogeneates and each of the three mixtures were analyzed by chromatography after 1 day incubation. EPTC was partly oxidized to EPTC-sulfoxide. EPTC-sulfoxide did not change and EPTC-sulfone produced similar metabolites as had been found in the germination experiment.     

Seasonal activity of EPTC for Cyperus rotundus L. control in a tropical climate*

Four experiments were conducted at six week intervals to determine the seasonal activity and persistence of soil-incorporated EPTC (5-ethyl N,N-dipropyl(thiocarbamate)) for Cyperus rotundus L. control and tolerance of okra (Hibiscus esculentus L.), cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), red beet (Beta vulgaris L.) and carrot (Daucus carota L.) during the dry and wet seasons in Viçosa, Brazil. Satisfactory control of C. rotundus was obtained at 2 kg/ha EPTC during the dry season and 4 kg/ha or more during the wet season. Only red beet and carrot tolerated these doses of EPTC when the crops were planted five days after application. However, selective control of C. rotundus was obtained when the planting date of lettuce was delayed for three or six weeks after EPTC application. EPTC controlled C. rotundus at half the dose that was required to control three species of annual grass that germinated near the soil surface. EPTC persisted longer when applied to air dry soil and incorporated with a rototiller than when incorporated into moist or wet soil.     

除草剂解毒剂减轻氯磺隆残留对玉米药害的研究

采用室内生物测定方法,研究了除草剂解毒剂5-二氯乙酰基-3,6-二甲基-3-乙基-9-氧代-1,5-二氮杂二环[4.3.0]壬烷减轻氯磺隆对玉米的伤害作用。结果表明:随着土壤中氯磺隆浓度的增大,玉米的生长受到抑制,用解毒剂浸种处理后,可在一定程度上减轻氯磺隆对玉米生长的影响。当土壤中氯磺隆残留量为2μg/kg时,解毒剂浓度在1～5mg/kg时解毒效果最佳,玉米株高、株鲜重、根长、根鲜重的恢复率最高可达101.27%、63.74%、73.29%和51.81%。     

Effects of the herbicide EPTC and the protectant DDCA on incorporation and distribution of [2-14C]acetate into major lipid fractions of maize cell suspension cultures

The rapid effects of the herbicide EPTC (S-ethyl dipropylthiocarbamate) and the protectant DDCA (N,N-diallyl-2,2-dichloroacetamide) on [2-¹⁴C]acetate incorporation into lipids of maize cell cultures were studied in order to determine whether they act at similar sites of lipid synthesis. DDCA, at 0.05 mM and 0.1 mM, increased the incorporation of [2-¹⁴C]acetate into neutral lipids of a total lipid extract within 2 h. It had very little effect on the major polar lipid constituents. DDCA altered neither the distribution of label within the major lipid classes, nor turnover of the major lipids within 2 h. EPTC (0.1 mM) inhibited overall uptake of [2-¹⁴C]acetate into both neutral and polar lipids by about 30% after a 2-h incubation. The major polar lipid affected was an unidentified glycolipid. In addition to reducing the quantity of lipids synthesized, EPTC changed the lipid profile, altering the distribution of label, mainly within the neutral lipid fraction. A crude membrane fraction from maize cells contained both polar lipids and some neutral lipids. DDCA stimulated [2-¹⁴C]acetate incorporation into different lipid species. EPTC inhibited incorporation of [2-¹⁴C]acetate into both neutral and polar membrane lipids but altered significantly only its distribution into neutral lipids. DDCA (0.1 mM) given together with EPTC (0.2 mM) partially counteracted the effect of EPTC within the neutral lipid fraction. It is suggested that DDCA has a rapid effect on lipid synthesis, but it is probably not sufficient to account for the entire mode of action of the protectant.     

我国玉米外来物种入侵防控技术研究与应用

玉米Zea mays作为一种重要的粮食和饲料作物,在生产中受到多种有害生物的严重危害,尤其是外来有害生物,我国高度关注其外来物种入侵防控工作。该文在概述玉米外来有害生物及其全球扩散途径的基础上,对近10年来我国玉米外来物种入侵防控技术的主要研究与应用进展进行分析,涉及风险分析、疫情监测、检测诊断、检疫处理及田间治理技术,并提出加强植物生物安全专业教育与公众教育、科学研究与理论创新、技术研发与推广应用、法规建设与监管服务、国际合作与共同发展的措施建议。     

Sulfur assimilation in plants and weed control: Potential targets for novel herbicides and action sites of certain safeners

Sulfur is an indispensable element for plants. It is found in sulfur-containing amino acids, cysteine and methionine, and in various other important biochemical components and processes. Inhibitors of sulfur assimilation, or cysteine and methionine synthesis, could be potential herbicides. In the present paper, the sulfur assimilation pathway in plants is described, followed by the introduction of several compounds (inhibitors and safeners) acting on this pathway. Uptake of inorganic sulfate through the roots is the first step of sulfur assimilation in plants. Sulfate is reduced mainly in chloroplasts to sulfide by a multistep process, and sulfide is then incorporated into cysteine. Cysteine is converted to cystathionine, homocysteine and methionine. Cysteine is incorporated into glutathione (GSH) by γ-glutamylcysteine synthetase and GSH synthetase. Three enzymes involved in cysteine and methionine biosynthesis, cysteine synthase, cystathionine γ-synthase and cystathionine β-lyase, have been investigated as target sites for herbicides. Several inhibitors of these enzymes (e.g. rhizobitoxine and propargylglycine) were also phytotoxic, suggesting that the synthetic pathway of sulfur-containing amino acids could be a new target site for herbicides. Some safeners for herbicides were found to act on the sulfur assimilation pathway and on GSH synthesis to increase GSH, which can be involved in herbicide metabolism and detoxification. Several safeners elevate GSH levels by increasing the activities of enzymes involved in sulfur assimilation and GSH synthesis. Further studies on plant sulfur metabolism may lead to the discovery of new herbicides and to the comprehensive understanding of the mode of action of safeners.     

Comparative dynamics of adherent and nonadherent bacterial populations on maize leaves

ABSTRACT The dynamics of the adherent and nonadherent populations of three bacterial species on maize leaves were examined to identify the extent to which bacteria adhere to leaves and the importance of this adhesion to leaf colonization. Pantoea agglomerans strain BRT98, Clavibacter michiganensis subsp. nebraskensis strain GH2390, and Pseudomonas syringae pv. syringae strain HS191R all rapidly adhered to maize leaves following inoculation, but differed in the percentage of cells that adhered to the leaves. Immediately following inoculation, the percentage of adherent cells was highest for the saprophyte P. agglomerans (8 to 10%) and was much lower for the pathogens C. michiganensis subsp. nebras-kensis and P. syringae pv. syringae (2 to 3 and <1%, respectively), although the results for P. syringae pv. syringae HS191R were based on only one experiment. In the 4 days following inoculation, the percentage of the P. agglomerans populations that adhered to the leaves increased to approximately 70%. Similarly, the percentage of C. michiganensis subsp. nebraskensis and P. syringae pv. syringae cells that resisted removal steadily increased in the days following inoculation, although these increases probably reflected both adherence and localization to endophytic sites. Based on differences in the percentage of cells adhering to several cuticular wax mutants of maize, the rapid adherence of C. michiganensis subsp. nebraskensis cells to maize leaves was influenced by the cuticular wax properties, while the rapid adherence of P. agglomerans was not. Finally, bacterial adherence to leaves was advantageous to P. agglomerans survival and growth on leaves based on the finding that the nonadherent populations of the P. agglomerans strain decreased significantly more than did the adherent populations in the 24 h following inoculation, and increased much less than did the adherent populations over the next 3 days. Similar results with the C. michiganensis subsp. nebraskensis and P. syringae pv. syringae strains indicate that bacterial adherence to leaves, bacterial movement to endophytic sites, or both were advantageous to the survival and growth of these strains on leaves.     

Nit突变体技术在玉米弯孢菌研究中的应用

采集了河南省12个地区的玉米弯孢菌叶斑病标样,分离获得了34个菌株,其中3个是画眉草弯孢(Curvu-laria eragrostidis),其余均为新月弯孢(C.lunata)。利用含KClO₃的培养基对其中14个新月弯孢菌株和1个画眉草弯孢菌株(XZ3c)进行诱导,在MM培养基上鉴定均获得了Nit突变体。对获得的190个Nit突变体在MO₂和MH培养基上进行了生理表型的划分,并用于菌株内、菌株间的营养体亲和性研究,发现有不少配对组合中均出现了明显的亲和现象,表明Nit突变体技术可以用于玉米弯孢病菌营养体亲和性的研究。根据亲和性测定的结果将这15个菌株初步分为2个营养体亲和群。