Summary• Reduction in the degree of powdery mildew infection of wheat leaves is observed after treatments with trehalose, a nonreducing disaccharide commonly found in a wide variety of organisms, including fungi.• Wheat ( Triticum aestivum ) cv. Sideral plants grown in phytotrons were inoculated with Blumeria graminis f.sp. tritici . In addition to degree of infection, the effect of trehalose solution was further investigated using light and fluorescence microscopy and enzyme assays.• Infection in wheat leaves was reduced by 50 and 95% with trehalose solution (15 g l − 1 ) following a single spraying and three sprayings, respectively; in a detached leaf assay, trehalose was effective at concentrations as low as 0.01 g l − 1 . Trehalose did not inhibit conidial germination and differentiation of appressoria ( in vitro or on the leaf epidermis), but enhanced papilla deposition in epidermal cells. Trehalose also enhanced phenylalanine ammonia-lyase (PAL) and peroxidase (PO) activities; both markers of plant defence responses. However, the level of three cinnamyl alcohol dehydrogenase (CAD) activities (conyferyl, p -coumaryl and sinapyl alcohol dehydrogenase) was unchanged.• Trehalose treatment of wheat confers resistance to B. graminis infection by activating plant defence responses (e.g. papilla deposition, PAL and PO activities).

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Novel carbamic esters possessing a carbohydrate moiety derived from glycerol or D-glucose with two N,N-diethyldithiocarbamoyl groups and a series of bisdithiocarbamic esters having a ketone or an alkyl ester have been synthesized. The in vitro activity of these new compounds was evaluated against Fusarium oxysporum f. sp. lini. Some of the compounds [bis[1,3-S-(N,N-diethyldithiocarbamoyl)]-1, 3-dideoxyglycerol) and diethyl N,N'-(1,3-dideoxyglycer-1, 3-diyl)bis(dithiocarbamate)] were more active for inhibiting vegetative mycelium growth than, respectively, the commercial N, N-diethyldithiocarbamic acid sodium salt and Maneb. The structure activity of these new compounds is discussed.

An extracellular lipase (EC 3.1.1.3) from the fungus Botrytis cinerea has been purified to homogeneity and characterized. The purification included ammonium sulfate fractionation and sequential column chromatography. The purification of the preparation was 31-fold and recovery yield was 21%. The purified enzyme was associated with esterase activity according to activity staining on polyacrylamide gel. The molecular weight was determined as 60 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and estimated at 72 kDa using gel filtration, which suggests that the enzyme may be a monomer. The isoelectric point was 6.5, and optimal activity was obtained at 38 degrees C and pH 6.0. This lipase showed a high specificity for synthetic substrates containing long-chain unsaturated fatty acids using umbelliferone esters. The effect of beta-cyclodextrin on the hydrolysis of olive oil has been studied. The specific activity was 25 mumole/min/mg in the absence of beta-cyclodextrin and 132 mumole/min/mg in its presence.

Ri-T-DNA-transformed carrot roots were used for investigating sterol metabolism by the arbuscular mycorrhizal (AM) fungus Glomus intraradices under three distinct experimental conditions: (i) a symbiotic stage (fungus still attached to the host roots); (ii) a detached stage (fungus physically separated from the roots); and (iii) a germinating stage (germinating spores). In all three stages, G. intraradices was found to contain a mixture of 24-alkylated sterols, with 24-methyl and 24-ethyl cholesterol as the main compounds, but no ergosterol, the predominant sterol in most fungi. Feeding experiments with [1-14C]sodium acetate were performed to check the ability of the fungus to synthesize sterols. Whatever the experimental conditions, G. intraradices was able to actively take up exogenous acetate and to incorporate it into sterols and their precursors. Our data provide first evidence for de novo sterol synthesis by an AM fungus.