Influence of formulation on triticonazole solubilisation and sorption in a soil–water system

The effect of agronomic doses of three suspension concentrate formulations and two anionic surfactant adjuvants on the solubilisation and sorption characteristics of triticonazole fungicide in a loamy clay soil was investigated. Soil sorption of [¹⁴C]triticonazole alone, in the formulations, and in the presence of increasing doses of formulation additives was measured using the classical batch equilibration technique. Triticonazole solubilisation in water‐formulation systems was also evaluated using a batch procedure, and sorption of the formulation aqueous phases on soil was examined. Solubilisation of triticonazole in the formulation systems occurred in excess of the solubility in water (S_w). This was attributed to triticonazole association with surfactant monomers. Sorption isotherms of triticonazole with diluted surfactants and other formulation additives were similar to that of triticonazole alone. We concluded that in soil‐formulation systems, triticonazole solubilisation in excess of the S_w may increase the amount available in soil solution for plant absorption. However, triticonazole molecules preferentially associated with the soil surfaces, and the presence of diluted amounts of the formulation adjuvants would not significantly affect the soil sorption process. © 2000 Society of Chemical Industry     

Influence of soil type and water content on release of triticonazole from coated maize seed

The release of [¹⁴C]triticonazole from coated maize seeds into soil, and its incorporation in maize, were studied under laboratory conditions over seven days in two soils at two different water contents (equivalent to a matrix potential of −3 kPa and −1580 kPa). The behaviour of a commercial coating formulation was compared to that of the same formulation supplemented with a pellicle to improve coated seed handling. Triticonazole released into soil, remaining in the integument and incorporated in different parts of the plant (stem, root, albumen) was measured. The triticonazole released into the soil corresponded to 25% of the initial applied amount on the seed under the best conditions (sandy soil, matrix potential of −3 kPa, set without pellicle). In these conditions, 13% of applied triticonazole was incorporated into roots and stems after seven days. The presence of an additional pellicle to improve the coating decreased the quantity of triticonazole released into soil and consequently the quantity of triticonazole incorporated into the plant. In all cases, the diffusion of triticonazole from the seed to the soil was not limited by the water solubility of triticonazole. Instead, the sorption of triticonazole on soil appears to be the key process governing its fate in soil. © 2000 Society of Chemical Industry     

The fungicide captan reduces nuclear DNA content in maize seedlings

Captan, a major fungicide used by the US maize industry, was studied to determine its effect on the nuclear DNA content of maize (Zea mays L.) seedlings. Captan was applied to kernels at the recommended agronomic rates. The nuclear DNA content of the seedlings was determined by flow cytometry. In two maize hybrids examined, a reduction in nuclear DNA content was observed. Two different fluorochromes, with different staining mechanisms, were used to determine nuclear DNA content. Both of these fluorochromes revealed a reduction in nuclear DNA. Captan is reported to inhibit DNA synthesis in several animal systems. The reduction of maize nuclear DNA observed in this study may be a result of DNA synthesis inhibition induced by captan.     

灭菌唑与氰烯菌酯复配对水稻恶苗病菌的抑制活性

采用菌丝生长速率法，测定了灭菌唑对水稻恶苗病菌的毒力，测得灭菌唑对10株水稻恶苗病菌的EC₅₀值范围为0.0664~0.7661 μg/mL。采用有效成分质量浓度分别为60、120和240 μg/mL的25 g/L灭菌唑种子处理悬浮剂处理水稻种子后，对水稻发芽率、株高、鲜重均无影响。表明灭菌唑对水稻恶苗病菌具有较好的抑制活性，且对水稻安全，可用于水稻恶苗病的化学防控。氰烯菌酯对10株水稻恶苗病菌的EC₅₀值范围为0.0076~0.2629 μg/mL。将氰烯菌酯和灭菌唑分别按质量比4 : 1、3 : 1、2 : 1、1 : 1、1 : 2、1 : 3和1 : 4复配，测定了复配药剂对水稻恶苗病菌的联合毒力，所得增效系数在0.5~1.5之间，均为相加作用。研究表明，将氰烯菌酯与灭菌唑复配后施用，不仅能显著降低单剂的使用剂量，且能降低氰烯菌酯对病原菌群体的选择压力，延缓抗药性的发生和发展速度，保障病害防效和水稻生产安全。     

Uptake of Triticonazole,during Imbibition,by Wheat Caryopses after Seed Treatment

The uptake of ¹⁴C-labelled triticonazole by wheat caryopses during imbibition was investigated. The uptake from an aqueous solution appeared to be driven by mass flow rather than by accumulation in seed lipids. During treatment with a liquid seed-dressing preparation of triticonazole, c. 1 μg triticonazole per caryopsis (2·4% of applied triticonazole) entered the seed. During germination in soil, another c. 1 μg triticonazole per caryopsis entered the seed in 24 h. In killed seeds, no penetration was observed between 24 h and 72 h after the beginning of imbibition. After seed treatment and imbibition in soil, triticonazole appeared to be located in the seed coats and embryo, but not in endosperm; experiments suggested that the testa acted as a barrier. Under our conditions, the pathway from seed coats to shoots was not an important route for triticonazole uptake by the shoots. © 1997 SCI.     

Sorption of low levels of nonionic and anionic surfactants on soil: effects on sorption of triticonazole fungicide

The sorption of two anionic surfactants and a series of seven nonionic alkylphenolethoxylate surfactants of increasing hydrophilic/lipophilic balance (HLB) in a loamy clay soil was evaluated. The effect of low doses of these surfactants on the sorption characteristics of the fungicide triticonazole was investigated. The critical micellar concentration (CMC) of the surfactants in pure water and soil–water systems, and surfactant sorption were estimated by surface tension measurements using a batch equilibration technique. Triticonazole sorption, alone and in the presence of low doses of surfactants, was also measured by batch equilibration. CMC of the alkylphenol surfactants increased with their HLB. The sorption of surfactants increased with their lipophilicity. CMC in the soil–water systems were considerably higher than in pure water. Sorption of the most lipophilic alkylphenol surfactants at the higher doses significantly increased triticonazole sorption. Proposed mechanisms are modifications of soil surface properties, and increase of soil organic carbon content. Sorption of the other nonionic and anionic surfactants only resulted in monomeric surfactant concentrations in pore water, and did not affect triticonazole sorption. © 1998 Society of Chemical Industry     

Effects of Two Triazole Seed Treatments,Triticonazole and Triadimenol,on Growth and Development of Wheat

The triazole fungicides, triadimenol and triticonazole, applied as seed treatments at various rates on spring wheat, affected plant growth, shoot development, and root axis production. The main growth regulatory effects were reductions in lengths of the coleoptile, the first leaf and the subcrown internode. A marked effect on tiller appearance occurred with high rates of triadimenol. Modification of root-system development included a reduction in the number of seminal roots, increased outgrowth of roots associated with the coleoptilar node, and a reduction of roots at the first foliar node (correlated with reduced production of Tiller 1). Seed treatment effects on both shoot and root development illustrated the close relationship between these plant structures. Both fungicides induced both beneficial and deleterious effects on wheat growth and development, but the magnitude of deleterious effects was less with triticonazole than with triadimenol.     

Mechanism of action and fate of the fungicide chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in biological systems 3. Interaction with mammalian DNA,histones, and isolated rat liver nuclei

The reactions of chlorothalonil with calf thymus histones, DNA, and isolated rat liver nuclei were studied utilizing labeled fungicide, polyacrylamide gel electrophoresis, and nucleohistone thermal denaturation. The reaction was dependent on pH, type of histones, and the histone and fungicide concentrations. In addition, two types of fungicide-histone binding patterns were observed. These patterns were characterized by the amount of label bound to protein after dialysis or after dialysis and acid precipitation. There was little binding of chlorothalonil to DNA. Polyacrylamide gel patterns of treated lysine-rich calf thymus histones were characterized by a loss of up to 80% of the stained protein without a change in the migration of the bands. Gel patterns of treated calf thymus whole histones were characterized by small variations in band density and minor loss of stained protein. The results of thermal denaturation experiments using chlorothalonil-treated lysine-rich histones and nontreated calf thymus DNA were not different from those using nontreated histones. Almost all of the radioactivity from [¹⁴C]chlorothalonil was bound by isolated rat liver nuclei. The binding patterns observed with rat liver nuclei were very similar to those using purified histones. Fractionation of proteins from treated nuclei revealed that the label was unequally distributed between the nuclear sap protein, ribonucleoprotein, and deoxyribonucleoprotein.     

Effects of glycerol ethers on monocotyledon nucleic acid and protein biosynthesis

The growth of the root systems of 2-day-old wheat seedlings was more sensitive to the experimental herbicide WL 29226 than was the growth of the shoots. Inhibition of root growth was observed after 12 hr of exposure to the herbicide. The nuclear activity in these root systems, as estimated by RNA and DNA synthesis, was significantly inhibited before this time, ～30% after 4 hr increasing to ～55% after 8 hr. Nuclear activity was inhibited by ～80% after 24 hr and showed little increase in inhibition with any further increase in exposure to the herbicide. Protein synthesis was initially less inhibited, ～6% after 4 hr, rapidly increasing to ～40% after 8 hr. DNA polymerase activity was monitored as an indication of the nucleic acid biosynthetic capacity of herbicide-treated maize and barnyard grass chromatin. In both plants, the herbicide induced an inherent modification of this activity. In maize this was reflected by an inhibition of activity and in barnyard grass by a stimulation. The effect on barnyard grass chromatin is likely to be more complex than in maize because of the presence of a chromatin-bound DNase in the chromatin from control plants. There is no evidence for such an enzyme in the chromatin from either maize or glycerol ether-treated barnyard grass. The apparent stimulation of DNA polymerase activity may in some way be associated with the loss of this nuclease activity. In order to obtain an inhibition of chromatin DNA polymerase, the plants must be pretreated with the herbicide prior to chromatin extraction. The failure of the herbicide to induce an inhibition in vitro on isolated chromatin does not support a direct interaction between the herbicide and chromatin. The results suggest that, following herbicide application to the plant, chromatin integrity has been altered.     

Characterization of Botryosphaeria dothidea Isolates Collected from Pistachio and Other Plant Hosts in California

ABSTRACT Eighty-six isolates of Botryosphaeria dothidea, the causal agent of Botryosphaeria panicle and shoot blight of pistachio, were collected from pistachio and other plant hosts in California. The isolates were characterized by microsatellite-primed polymerase chain reaction (MP-PCR), sequences of the nuclear ribosomal DNA internal transcribed spacer region (ITS1, 5.8S gene, and ITS2), morphological and cultural characters, osmotic and fungicide sensitivity, and pathogenicity on pistachio. Three groups of these isolates were identified based upon analysis of MP-PCR data and ITS sequences. Group I contained 43 pycnidiospore-derived isolates collected from pistachio and other hosts. Group II consisted of 20 ascosporic isolates obtained from a single sequoia plant. Group III consisted of 20 ascosporic isolates from three shoots on a single blackberry plant, two pycnidiospore-derived isolates from incense cedar, and one from pistachio. Group I predominated over the other two groups in California pistachio orchards. B. dothidea isolates of group III grew faster on acidified potato dextrose agar (APDA) than the isolates of groups I and II. Isolates of group III produced pycnidia on both APDA and autoclaved pistachio shoots, but the isolates of the other two groups produced pycnidia on only autoclaved pistachio shoots. Additionally, significant differences in osmotic and fungicide sensitivities were observed among these three groups. Results from lathhouse inoculations demonstrated that the representative isolates for each of the three groups were all capable of infecting pistachio and producing characteristic disease symptoms of Botryosphaeria blight. The virulence of group II isolates on pistachio was, however, significantly lower than that of group I isolates.     

Dissipation of propiconazole residues in and on wheat (Triticum aestivum L.)

In a 2-year investigation, the dissipation of residues of the fungicide propiconazole from winter wheat straw and leaves was measured by periodic sampling of the green plant material from several plots that had been sprayed with ‘Tilt 2.50EC’ at three different rates. The fungicide deposits on straw and leaves at day 0 were approximately one-quarter of the dose applied on all treatment plots, and this fraction did not differ significantly between three dosage rates. The fungicide residues disappeared rapidly, and the half-life of the fungicide on straw and leaves was approximately 5 days. At harvest time, the fungicide residues in grain and soil were negligible, but the residues remaining on straw and leaves were considerable, especially at higher spraying rates than the recommended dosage.     

多因子联合诱导系统的构建及对黄瓜白粉病防治试验

由多个不同的抗病诱导因子组成植物抗病诱导系统的1个子系统。每个因子都是这个系统中的1个要素。系统的性质不但取决于系统中的要素,还取决于要素的结构。合理的配伍可以使要素与要素之间、要素与系统之间的关系得以优化,使系统的功能得以强化。把筛选得到的多个不同的抗病诱导因子进行配伍,组合成新的"诱导组合体",其诱导效应比单一因子显著提高;用不同的"诱导组合体"进行"相继诱导"和"循环诱导",则进一步提高诱导效应,对黄瓜白粉病的田间防治效果达到78.16%,高于常规杀菌剂的防治效果。     

Inhibition of DNA polymerase β activity in isolated bovine liver nuclei by captan and related compounds

The effects on DNA synthesis of the fungicide captan and several structurally related compounds were investigated in isolated bovine liver nuclei. Captan, folpet, captafol, and trichloromethanesulfenyl chloride inhibited DNA synthesis to the same degree with ID₅₀ values of approximately 50 μM in a 40-min assay. The inhibition is concentration dependent and the degree of inhibition increases with time. Studies with structural analogs of captan indicated that inhibition of DNA synthesis by captan is mediated through the trichloromethylthio moiety of the captan molecule. In addition, the data indicate thiophosgene is probably not the toxic species involved in the inhibition of DNA synthesis. The isolated nuclei used in this study were shown to exhibit only a single DNA polymerase activity which was determined to be of the β or low-molecular-weight type. In addition to its inhibition in intact nuclei, captan inhibited the activity of the β polymerase in nuclear extracts as well as in partially purified enzyme preparations. These results indicate that captan inhibits DNA synthesis in our preparation of isolated nuclei by acting directly on the DNA polymerase-catalyzed reaction rather than by causing a nonspecific or indirect effect in the nuclear system such as alterations in the nuclear membrane or aggregation of the nuclei. The site of captan's inhibitory action is the DNA polymerase molecule. The interaction of captan with the polymerase results in irreversible inhibition of the enzyme. Interaction of captan with the template, if it occurs, does not appear to be involved in mediating the inhibition.     

Uptake and fate of triticonazole applied as seed treatment to spring wheat (Triticum aestivum L.)

Following seed treatment of wheat (Triticum aestivum L.) with ¹⁴C-labelled triticonazole at a dose of 1·8 g kg^-1 seed, the uptake of radioactivity by shoots and roots was investigated from the two- to three-leaf stage up to the beginning of the booting phase, 80 days after sowing. Triticonazole equivalents taken up by wheat plants reached 5·7% and 14·6% of the applied dose in the shoots and the roots, respectively. Between the two- to three-leaf stage and the beginning of the booting phase, the concentration of triticonazole equivalents in the shoots decreased from 2·5 to 0·15 μg g^-1 fresh weight. This was attributed to uptake of triticonazole by roots not keeping pace with shoot growth and increased retention in the roots of triticonazole taken up. The main factor limiting the uptake of triticonazole by the roots may be the rapid growth of the uptake-active apical root parts out of the dressing zone which had formed in the soil. Distribution of triticonazole equivalents taken up by the main shoot showed a decreasing concentration gradient from the oldest to the youngest leaf. An increase in the seed treatment dose was investigated as a way to increase the concentration of triticonazole in the shoots, but its influence remained limited. © 1998 SCI     

Target and non-target site mechanisms of fungicide resistance and their implications for the management of crop pathogens

Fungicides are indispensable for high-quality crops, but the rapid emergence and evolution of fungicide resistance have become the most important issues in modern agriculture. Hence, the sustainability and profitability of agricultural production have been challenged due to the limited number of fungicide chemical classes. Resistance to site-specific fungicides has principally been linked to target and non-target site mechanisms. These mechanisms change the structure or expression level, affecting fungicide efficacy and resulting in different and varying resistance levels. This review provides background information about fungicide resistance mechanisms and their implications for developing anti-resistance strategies in plant pathogens. Here, our purpose was to review changes at the target and non-target sites of quinone outside inhibitor (QoI) fungicides, methyl-benzimidazole carbamate (MBC) fungicides, demethylation inhibitor (DMI) fungicides, and succinate dehydrogenase inhibitor (SDHI) fungicides and to evaluate if they may also be associated with a fitness cost on crop pathogen populations. The current knowledge suggests that understanding fungicide resistance mechanisms can facilitate resistance monitoring and assist in developing anti-resistance strategies and new fungicide molecules to help solve this issue. © 2023 Society of Chemical Industry.     

不同杀菌剂对稻粒黑粉病菌冬孢子萌发的影响

稻粒黑粉病(Rice kernel smut)是一种真菌病害。在离体条件下,采用孢子萌发测定法,测定了嘧菌酯、灭菌唑、拌种灵、多菌灵、咪酰胺和二硫氰基甲烷抑制稻粒黑粉病菌冬孢子萌发的最低抑制浓度(MIC);同时研究了药剂浸种处理对稻种的安全性以及浸种处理效果。结果表明,嘧菌酯和二硫氰基甲烷对稻粒黑粉病菌冬孢子萌发的抑制活性较高,MIC为0.4μg/mL,多菌灵的抑制活性次之,MIC为0.8μg/mL,其他3种药剂的抑制活性不高,MIC均大于1.6μg/mL。种子安全性试验表明,嘧菌酯在2.0、4.0、8.0μg/mL和多菌灵在4.0、8.0、16.0μg/mL处理3d和7d后,稻种的萌芽率与对照相比无显著性差异;而二硫氰基甲烷在4.0和8.0μg/mL处理下,所选稻种的萌芽率显著低于对照,说明该药剂在浸种处理后会影响所选稻种的萌芽,但其在低剂量处理下对稻种的萌芽率影响较小。关于稻粒黑粉病浸种处理的合适农药剂型仍需要进一步研究。     

A note on the mode of action of the systemic fungicide tridemorph

The effects of the systemic fungicide tridemorph on fungal and plant protoplasts have been investigated. No evidence of reaction at the plasma-membrane was revealed by microelectrophoresis. The fungicide did not affect oxygen uptake by fungal protoplasts but incorporation of labelled histidine was reduced. Fungi-toxicity tests showed that tridemorph had little effect on spore germination but inhibited mycelial growth. It is suggested that the fungicide may act by interfering with the synthesis of proteins essential for hyphal extension.     

Spatial and temporal impact of fungicide spray strategies on fungicide sensitivity of <Emphasis Type="Italic">Mycosphaerella graminicola</Emphasis> in winter wheat

Field experiments, involving various fungicide strategies with pyraclostrobin and/or epoxiconazole were carried out in 2004 and 2005, with the overall purpose of monitoring the evolution of fungicide sensitivity in Mycosphaerella graminicola on different isolates per leaf, leaf levels at different points of time, and points in the field. Sensitivity was assessed on single isolates by means of epoxiconazole EC₅₀-values, and monitoring of the G143A-mutation, which confers strobilurin resistance. In both years, fungicide application strategies did not cause any significant shifts in epoxiconazole sensitivity of the population median or variance over time compared to the starting population. In 2004, the end-population median was the same for all sprayed strategies, although compared to untreated median sensitivities were higher. In 2005, epoxiconazole sensitivity levels were similar on individual flag leaves and different points in the field. Measured on all isolates the EC₅₀-values ranged from 0.007–1.15 mg l⁻¹. In 2004, due to the high initial level of pyraclostrobin resistance, stabilisation of pyraclostrobin resistance was observed following the various combination treatments. No correlation between epoxiconazole sensitivities and pyraclostrobin resistance were observed. High input strategies using a mixture of epoxiconazole and pyraclostrobin resulted in the best control and yield response. A subpopulation of the isolates from 2004 was also screened for sensitivity towards five different triazoles of which tebuconazole proved to be least sensitive, and this could further be split into two subpopulations.     

植物病原菌抗药性及其抗性治理策略

随着现代高活性的选择性杀菌剂的研发和广泛使用,病原菌的抗药性问题日趋严重,这已成为植物病害化学保护领域最受关注的问题之一。本文阐释了抗药性相关术语的定义,概述了病原菌的抗药性现状,并从自然选择和诱导突变两种学说的角度分析了抗药性产生的原因。进一步分析了抗药性群体流行与病原菌自身特点、杀菌剂类型和作用机制等影响因子密切相关,综述了抗药性风险评估、抗药性机制、抗药性进化以及抗药性常规和分子检测方法等内容。最后,提出了抗药性治理的目标和策略,即根据抗药病原群体形成的主要影响因素,针对性地设计抗药性治理短期和长期策略,特别是需进一步加强对新药剂和新防治对象开展抗药性风险评估、制定抗药性管理策略、建立再评价机制等。综上,明确植物病原菌抗药性发生发展特点并制定科学合理的抗性治理策略,对进一步开展植物病害的科学防控具有重要的参考价值。     

Dynamics of pear-pathogenic Stemphylium vesicarium in necrotic plant residues in Dutch pear orchards

Brown spot disease on pear caused by Stemphylium vesicarium may affect leaves and fruits. Inoculum sources present on orchard floors play an important role in the epidemiology of pear brown spot. The pathogen can overwinter on plant residues and multiply and spread on the residues during the growing season. In the Netherlands, brown spot characteristically occurs only in a fraction of the orchards per season. Until now, no tools are available for Dutch pear growers to predict the risk of brown spot in specific orchards. As a consequence, preventive fungicide sprayings are common. The concentration of DNA of pear-pathogenic S. vesicarium was quantified by a specific TaqMan-PCR assay for various types of plant residues present on orchard floors to evaluate their importance as potential inoculum source. The pathogen was often found in residues of pear leaves, grasses and weeds, but only occasionally in mummies and prunings. Studies of the population dynamics showed that S. vesicarium decreased in dead pear leaves during early winter whereas pathogen populations developed with irregular pattern during the growing season on residues of weeds and grasses. Based on DNA concentrations of S. vesicarium in plant residue samples taken in 78 to 106 orchards in the springs of 2010, 2011 and 2012, the risk of brown spot development could be predicted for individual orchards. Such a risk prediction will allow growers to adapt their fungicide spray schedules to avoid unnecessary sprays in low-risk orchards.