Structure-activity relationships in fungitoxicants related to triforine and chloraniformethan. I. Synthesis and fungitoxicity to Erysiphe graminis on barley

Seventy analogues of chloraniformethan and triforine were prepared and tested for activity against barley powdery mildew caused by Erysiphe graminis. Structural variations, including replacement of the trichloromethyl, formamido, 3,4-dichloroanilino or piperazin-1,4-diyl groups, yielded information concerning the structural characteristics required for activity in leaf-spray or root-drench tests, and it appears that the XCHNHCO grouping (where X=substituted nitrogen, oxygen or sulphur) is a prerequisite for activity.     

The fungitoxicity of substituted 2-phenylbenzofurans

Thirty-seven 2-phenylbenzofurans, variously substituted in the homocyclic rings, were synthesised and assessed for antifungal activity in laboratory tests. High activity was shown only by compounds containing a hydroxy group, though amino compounds were also fungitoxic but at a lower level. Possible mechanisms by which these substitutions impart fungitoxicity are discussed with particular reference to the partitioning properties of the molecule.     

The metabolism of carboxin in growing barley

The major soluble metabolite of carboxin (2,3-dihydro-6-methyl-5-phenylcarbamoyi-1,4-oxathiin) in barley seedlings and mature plants was identified as the-hydroxy phenyl derivative. This phenol was also bound to the lignin fraction. The distribution of carboxin and its metabolites in seedlings and mature plants grown from treated seed was studied; maximum residues were found in the three oldest internodes, with traces in the roots and flowering heads. Treated plants had altered chlorophyll/carotenoid ratios, and raised levels of some free amino acids.     

Studies on the selective fungitoxicity of aliphatic amines

A comparison of the uptake of simple (C₁–C₄) aliphatic amines byPenicillium digitatum revealed that the fungitoxicity of (?)sec-butylamine [(?)SBA] was not due to its accumulation by hyphae since (+)SBA was accumulated to the same extent and methylamine, which showed negligible antifungal activity, accumulated to twice the level of SBA. Amines with a secondary alkyl structure were resistant to fungal metabolism, whereas primary amines were degraded to a significant extent byP. digitatum during a 4 h incubation period.(?)SBA accumulated in the fresh hyphae ofP. digitatum to a level 24 times higher than that in the culture medium containing 1 μmol ml^?1; most of the SBA effluxed from the hyphae when transferred to fresh culture medium minus SBA. SBA did not accumulate when hyphae were incubated in N₂ or in the presence of respiratory inhibitors. The absorption and accumulation of SBA is characteristic of active transport.Penicillium species and biotypes that are sensitive to SBA did not accumulate more (?)SBA than resistant fungi. SBA-resistant biotypes ofP. digitatum accumulated SBA to twice the level of SBA-sensitive biotypes, but did not accumulate pyruvate in the hyphae, which is characteristic of SBA-altered metabolism.No evidence was found to implicate exclusion or metabolic detoxification as mechanisms of SBA resistance. More probably, resistance involves cytoplasmic sequestration of SBA or low affinity of the biochemical target, pyruvic dehydrogenase.     

A note on the bimodal concentration response of Pythium aphanidermatum to carboxin and carbendazim

The concentration/respone curve for carboxin and carbendazim against mycelial growth of Pythium aphanidermatum measured in vitro is bimodal, suggesting the involvement of more than one concentration-dependent site of action.     

Studies on the selective fungitoxicity of aliphatic amines

A comparison of the uptake of simple (C₁–C₄) aliphatic amines byPenicillium digitatum revealed that the fungitoxicity of (–)sec-butylamine [(–)SBA] was not due to its accumulation by hyphae since (+)SBA was accumulated to the same extent and methylamine, which showed negligible antifungal activity, accumulated to twice the level of SBA. Amines with a secondary alkyl structure were resistant to fungal metabolism, whereas primary amines were degraded to a significant extent byP. digitatum during a 4 h incubation period.(–)SBA accumulated in the fresh hyphae ofP. digitatum to a level 24 times higher than that in the culture medium containing 1 mol ml^–1; most of the SBA effluxed from the hyphae when transferred to fresh culture medium minus SBA. SBA did not accumulate when hyphae were incubated in N₂ or in the presence of respiratory inhibitors. The absorption and accumulation of SBA is characteristic of active transport.     

Synthesis and fungitoxicity of O,O-diaryl S-ethyl phosphorothioates

Twenty new O,O-diaryl S-ethyl phosphorothioates were synthesised and tested for fungitoxicity in vitro against Pyricularia oryzae, Helminthosporium oryzae, Alternaria alternata, Rhizoctonia bataticola, and Pythium aphanidermatum. Of these compounds, S-ethyl O,O-bis(2, 4,5-trichlorophenyl) phosphorothioate and S-ethyl O,O-bis(pentachlorophenyl) phosphorothioate exhibited high activity against all the test species.     

Comparative fungitoxicity of the insecticide permethrin and ten degradation products

The toxic effects of permethrin and ten of its degradation products on the growth of ten fungi were determined. Permethrin was relativelynon-toxic, with an EC₅₀ of > 100 mg litre^?1 but six of the degradation products were significantly (P= 0.05) more inhibitory. The ester hydrolysis products, 3-phenoxybenzyl alcohol and 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, had EC₅₀ values ranging from 8 to > 100 and 20 to > 50 mg litre^?1, respectively. Other degradation products that were more toxic than permethrin included 3-phenoxybenzaldehyde and 3-phenoxybenzoic acid, with EC₅₀ values as low as < 1 mg lite^?1. Hydroxylated and substituted-benzene metabolites were non-toxic. Combinations of selected test compounds yielded both synergistic, antagonistic and additive interaction responses, depending upon the test system employed.     

Bioassay evaluation of the systemic properties of carboxin in lemon seedlings

Carboxin was toxic to the fungus Deuterophoma tracheiphila. Uptake and translocation of carboxin (2,3-dihydro-6-methyl-5-phenylcarbamoyl-1,4-oxathiin) in lemon seedlings were assessed in plant extracts by a bioassay technique. Root uptake and translocation to stem and leaves were demonstrated from both an aqueous solution and drenched soil. Leaf uptake was lower than root uptake, and could be enhanced by removing the epicuticular wax. Chromatographic tests suggested that the compound responsible for fungitoxicity within plant tissues may have been carboxin itself.     

嘧霉胺对梨黑斑病菌(Alternaria alternata)的毒力及其药效评价

采用菌丝生长速率法测定了嘧霉胺对梨黑斑病病原菌链格孢菌(Alternaria alternata)的毒力,并进行其对梨黑斑病的田间药效试验。结果表明：嘧霉胺对梨黑斑病菌菌丝生长抑制的EC50为0.126 8 μg/mL ;40%嘧霉胺可湿性粉剂250～500 mg/L对梨黑斑病的防效为66%～82%,且该药剂在本试验剂量范围内对梨树安全。     

Fungicidal activity and chemical constitution XXT. The fungitoxicity of aliphatic polyamines

Fifteen polyamines have been prepared and shown to inhibit spore germination of Penicillium expansum and Neurospora crassa in vitro, but not Erysiphe graminis, Sphaerotheca fuliginea or Podosphaera leucotricha; no activity was shown against S. fuliginea on marrow seedlings or P. leucotricha on apple seedlings. Spermine homologues were considerably more active than spermidine homologues, but greatest activity was shown by the two naturally occurring compounds.     

Biological effects of combining carboxin,organomercury fungicides and insecticides as seed dressings for wheat,and the effect of these combinations on adherence of the pesticides to the seed

When seeds of winter wheat were carefully dressed in the laboratory with combinations of fungicides (organomercury alone or organomercury plus the systemic fungicide carboxin) and insecticides (aldrin, carbophenothion or chlorfenvinphos as liquid formulations, or a γ-BHC powder formulation) so as to ensure that nearly all the recommended amounts of the active ingredients stuck to them, the insecticides gave good insect control, but γ-BHC with organomercury fungicide decreased the number of plants that germinated, and γ-BHC with carboxin and organomercury was even more damaging. Commercially dressed seeds had only about 30 to 60% of the target dose of fungicides, but more than 80% of the target doses of the liquid insecticides aldrin, carbophenothion and chlorfenvinphos. With combinations of powder fungicide and liquid insecticide, greater amounts of pesticide on the seed were obtained if the insecticide was put on first. Because of unusually late sowings and little fungal infestation, neither laboratory nor commercially treated seeds provided good tests for control of smut.     

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to glyphosate

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to sublethal concentrations of glyphosate were examined in order to evaluate the possibilities of using a response pattern in plants as a measure of exposure to glyphosate through the growth media, more sensitive than the well-known biomarker shikimate. Rapeseed seedlings were grown in hydroponic nutrient solutions containing varying sublethal concentrations of glyphosate (1–50 μM). After 9 days of glyphosate exposure, the shoots of the seedlings were analysed with respect to the effects on selected metabolites downstream from the primary affected metabolite shikimate, which accumulated linearly in response to glyphosate exposure (from 0 to ∼126 μmol/g DW). The selected metabolites analysed, comprising the free amino acids, and the glucosinolates derived therefrom, showed complex patterns in response to glyphosate exposure. Most noteworthy was though that they responded at the lowest concentrations of exposure to glyphosate (1 μM), where no visual effects, decrease in shoot DW or shikimate could be detected, indicating that a biomarker response more sensitive than that of shikimate can be established for plants exposed to glyphosate.     

The oldest fungicide and newest phytoalexin – a reappraisal of the fungitoxicity of elemental sulphur

Elemental sulphur (S⁰) is man's oldest fungicide. In biological systems it is formed by certain specialized prokaryotes but the element has rarely been found in eukaryotes. The recent discovery that certain plant species from diverse families produce S⁰ as a localized component of active defence to vascular pathogens, and that S⁰ is constitutive in some crucifers, led to this review. Because of the age and relative inaccessibility of some of the past literature and the inconsistency in the methods used, the spectrum of activity and the toxicity of S⁰ are reassessed here. Interpretation of bioassays of this and other hydrophobic compounds are offered. Also, brief coverage is given to the history of S⁰ use and its suggested mode(s) of action. The element's possible role in defence and the form, location and levels in planta are considered. Sulphur is one of many S-containing defence-related compounds and it is ironic that sulphur deficiency has recently become a widespread nutrient disorder in crops, largely due to restrictions on fossil fuel burning. The problem is being addressed by sulphur application, but the future manipulation of genes for sulphate uptake and sulphur biosynthesis are likely goals.     

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to glyphosate

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to sublethal concentrations of glyphosate were examined in order to evaluate the possibilities of using a response pattern in plants as a measure of exposure to glyphosate through the growth media, more sensitive than the well-known biomarker shikimate. Rapeseed seedlings were grown in hydroponic nutrient solutions containing varying sublethal concentrations of glyphosate (1-50 μM). After 9 days of glyphosate exposure, the shoots of the seedlings were analysed with respect to the effects on selected metabolites downstream from the primary affected metabolite shikimate, which accumulated linearly in response to glyphosate exposure (from 0 to ∼126 μmol/g DW). The selected metabolites analysed, comprising the free amino acids, and the glucosinolates derived therefrom, showed complex patterns in response to glyphosate exposure. Most noteworthy was though that they responded at the lowest concentrations of exposure to glyphosate (1 μM), where no visual effects, decrease in shoot DW or shikimate could be detected, indicating that a biomarker response more sensitive than that of shikimate can be established for plants exposed to glyphosate.     

桃蚜对噻虫嗪代谢抗性机制研究

对桃蚜进行室内噻虫嗪抗性品系筛选,选育至15代后抗性倍数达到75.6倍。对噻虫嗪敏感品系(THI-S)和抗性品系(THI-R)桃蚜的谷胱甘肽S-转移酶(GSTs)、酸性磷酸酯酶(ACP)、碱性磷酸酯酶(ALP)、羧酸酯酶(CarE)、多功能氧化酶(MFO)O-脱甲基活性进行了比较,结果显示:敏感品系(THI-S)和抗性品系(THI-R)的谷胱甘肽S-转移酶比活力分别为3.127 5和3.215 9,差异不显著,桃蚜抗性品系体内酸性磷酸酯酶、碱性磷酸酯酶、羧酸酯酶和多功能氧化酶O-脱甲基活性均显著高于敏感品系,分别达到了1.57、2.10、6.12、2.03倍。表明桃蚜对噻虫嗪抗性的产生与酸性磷酸酯酶、碱性磷酸酯酶、羧酸酯酶和多功能氧化酶O-脱甲基的活性相关。     

Tomato spotted wilt virus in peanut tissue types and physiological effects related to disease incidence and severity*

Three peanut cultivars, Georgia Green, NC-V11, and ANorden, were grown using production practices that encouraged the development of Tomato spotted wilt virus (TSWV). The progression of TSWV infection was examined through the season using enzyme-linked immunosorbent assay (ELISA) tests on different tissue types [roots, leaves, pegs (pod attachment stem structures) and pods] and the effect of TSWV infection on physiological functions was examined at three harvest dates. Plants were classed into three severity categories: (i) no TSWV symptoms or previous positive ELISA tests; (ii) less than 50% of leaf tissue exhibiting TSWV symptoms; and (iii) greater than 50% of leaf tissue affected. TSWV showed a slow rate of infection at the beginning of the season and a greater percentage of infection of the roots than in the leaves. Photosynthesis was reduced in virus-affected infected plants by an average of 30% at the mid-season harvest and 51% at the late season harvest compared with virus-free plants across all three cultivars. Leaf tissue with symptoms had lower photosynthetic rates than healthy leaves. There were small differences among cultivars, with cv. ANorden maintaining higher average photosynthetic levels than cv. Georgia Green and higher transpirational levels than cv. NC-V11. The ability to maintain high assimilation physiology in the presence of the virus may help cultivars withstand TSWV infection and maintain final yields.