The enantiomeric composition of triadimenol produced during metabolism of triadimefon by fungi. Part II: Differences between fungal species

The fungi Coriolus versicolor, Cladosporium cucumerinum, Botrytis cinerea and Fusarium culmorum, in shake culture, metabolised triadimefon to triadimenol. Analyses by gas–-liquid chromatography of the triadimenol showed that the fungi produced different qualitative and quantitative combinations of the four possible enantiomers, and that these differences were reproducible. The relationship between the enantiomeric composition of the triadimenol produced and the sensitivity of the test fungi to triadimefon, is discussed in the light of published data on the differences in antifungal activity shown by these enantiomers.     

Metabolism of the 1,2,4-triazolylmethane fungicides,triadimefon, triadimenol,and diclobutrazol,by Aspergillus niger (van Tiegh.)

Metabolism of the triazolylmethane fungicides triadimefon, triadimenol, and diclobutrazol by Aspergillus niger was studied using a replacement culture technique and ¹⁴C substrates. Components of metabolite mixtures were characterized by TLC, GLC, radio-GC, and GC-MS analyses of the free materials and their trifluoroacetate and trimethylsilyl ether derivatives. The three compounds underwent a common metabolic change involving oxidation of C(CH₃)₃ to C(CH₃)₂CH₂OH. In this work the isopropyl analog of triadimefon, previously reported as a metabolite, was an artifact and resulted from nonbiological oxidation of the corresponding primary alcohol. The fungus also reduced triadimefon to triadimenol, giving a mixture of 1R2S, 1S2R and 1R2R, 1S2S diastereoisomers. The less fungitoxic 1R2S, 1S2R triadimenol predominated, so that this conversion may be directly associated with the relative insensitivity of A. niger to triadimefon. Implications of oxidative and reductive metabolism of these fungicides are suggested with particular reference to the differing fungitoxicities of diastereoisomers and enantiomers.     

Reductive and oxidative metabolism of triazolylmethanes by two basidiomycete fungi

The metabolism of [¹⁴C]triadimefon, triadimenol, diclobutrazol, and the oxo-analogue of diclobutrazol by the basidiomycete fungi Coriolus versicolor and Rhizoctonia solani was studied. Reduction of >C = 0 to >CHOH (activation) was more important for triadimefon than oxo-diclobutrazol. Conversely, oxidation of >CHOH to >C = 0 (deactivation) occurred to a greater extent with diclobutrazol than triadimenol. Formation of primary alcohol metabolites, a possible detoxication route, occurred more with diclobutrazol and its oxo-analogue than with triadimefon and triadimenol. The implications of the reduction/oxidation processes and primary alcohol formation on fungitoxicity of the applied triazolymethane are discussed. The enantiomeric composition of metabolically produced triadimenol is discussed in relation to the in vitro activity of triadimefon supplied against each fungus.     

Chromatographic analysis of ergosterol biosynthesis inhibitors

The chlorophyll sensitised photodegradation of 2-dimethylamino-5, 6-dimethylpyrimidin-4-ol (I), a hydrolysis product of pirimicarb, in the solid state on silica gel and in chloroform solution has been investigated. The product distribution in the solid state photodegradation was different from that in chloroform solution and was dependent upon the wavelength range of the incident radiation. When radiation of wavelength greater than 420 nm was used, the products formed in the chlorophyll sensitised degradation of I in the solid state were similar to those obtained when Rose Bengal or Methylene Blue were used as sensitisers. These results indicate that singlet oxygen is implicated in the sensitised photodegradation of I in the solid state. Numerous products were formed in each of the systems studied.     

Control of potato late blight using controlled-release granules containing ofurace

In an attempt to reduce or eliminate the need for spraying to control potato late blight caused by Phytophthora infestans, investigations were made on the use of controlled-release granules containing the systemic fungicide ofurace. The granules when mixed with sand and buried in soil released the fungitoxicant for about 100 days. When the granules were applied in furrows at planting, protection of potato plants (cv. Maris Bard), assessed by inoculation of detached leaflets with P. infestans, lasted for between 85 and 100 days. Application of the granules when the plants were earthed up 48 days after planting did not result in better late-season protection, possibly due to poorer uptake of the fungitoxicant by the plants at this time. Chemical analysis of leaves from plants that had received in-furrow treatment indicated that ofurace at 0.2–0.5 μg g^?1 fresh weight was needed to confer protection from late blight.     

Investigation into the effect of tillage on solute movement to drains through a heavy clay soil

Abstract. Eight lysimeters, each with a surface area of 0.5 m² and a length of 60 cm, were taken over mole drains from a Denchworth soil and divided into two groups with either a standard agricultural tilth or a finer, deeper topsoil tilth. They were variously instrumented to measure soil moisture content at three depths and losses of nitrate, a bromide tracer and radiolabelled isoproturon, all of which were followed over a year. Leaching of isoproturon was initiated by artificial irrigation either 1 or 39 days after application. The finer tilth seemed to increase the water-holding capacity of the topsoil, and this resulted in slower wetting of the subsoil, decreased flow volumes from the first events of the season and a delay of approximately four weeks in the time to the maximum concentration of the bromide tracer in leachate. The finer topsoil tilth also decreased maximum concentrations of isoproturon from 29 to 15 μg l⁻¹ following irrigation 1 day after treatment and from 43 to 9 μg l⁻¹ following irrigation 39 days after treatment. Total losses of isoproturon were three times larger with the standard agricultural tilth. Differences were attributed to a decrease in bypass flow through the topsoil with the finer tilth, particularly during events early in the season. There was a small decrease in total losses of nitrate in leachate from the finer tilth compared to that from the standard tilth.