Volatile organic compounds (VOCs) collected from potato tubers inoculated with Phytophthora infestans (late blight), Fusarium coeruleum (dry rot) or sterilized distilled water (as a control) were analysed using gas chromatography±mass spectrometry (GC±MS) and gas chromatography±flame ionization detection (GC±FID). A total of 52 volatiles were identified by GC±MS in the headspaces above P. infestans-and F. coeruleum-inoculated tubers after incubation for 42 days in the dark at 108C. Of these VOCs, the six most abundant were common to both pathogens. These were benzothiazole (highest abundance), 2-ethyl-1-hexanol (second highest abundance), and at approximately equal third abundance, hexanal, 2-methylpropanoic acid-2,2-dimethyl-1-(2-hydroxy-1-methylethyl)-propyl ester, 2-methylpropanoic acid-3-hydroxy-2,4,4-trimethyl-pentyl ester and phenol. In addition, styrene also occurred at approximately equal third abundance in the headspace of F. coeruleum-inoculated tubers, but at lower abundance in the headspace of P. infestans-inoculated tubers. Some VOCs were specific to each pathogen. Butanal, 3-methylbutanal, undecane and verbenone were found at low levels only in the headspace of tubers inoculated with P. infestans, while 2-pentylfuran and copaene were found only in the headspace of tubers inoculated with F. coeruleum. Additionally GC±FID analysis identified ethanol and 2-propanol in the liquid exudate from both P. infestans-and F. coeruleum-inoculated tubers after incubation for 35 days, and in the headspace after incubation for 42 days. These data provide key information for developing a sensor-based early warning system for the detection of postharvest diseases in stored potato tubers.

Summary The sites of ATPase at pH 7·2 and β‐glycerophosphatase at pH 5·5 and 7·2 in the presence of Mg2+ have been determined by a lead precipitation technique and electron microscopy in leaves of Pisum sativum and Phaseolus vulgaris infected, respectively, with Erysiphe pisi and Uromyces appendiculatus. In the two plants, ATPase activity was similarly high in plasma membranes of epidermal, phloem transfer and companion cells and much lower in those of their mesophylls. The domain of the host plasma membrane invaginated around haustoria showed neither of these enzymic activities but infection did not otherwise alter their activities in either the rest of the plasma membranes of infected cells or the plasma membranes in uninfected cells. In Erysiphe pisi, the plasma membrane showed high activities with ATP and β‐glycerophosphate in haustoria but in other regions and in Uromyces appendiculatus, it lacked activity with both substrates. The sites of transition of the enzymic activities in all instances occurred at annular structures previously described in the haustorial necks. A mechanism of solute transport into haustoria is proposed and discussed in the light of the polarized distribution of ATPase activity in infected cells.

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Aims This study aimed to identify the most effective antimicrobial agent from a selection of essential oils (EO) and investigate its bactericidal properties against Pseudomonas aeruginosa. Methods and Results The disc diffusion assay and minimal inhibitory/bactericidal concentration tests were used to identify antimicrobial potential. Several oils exhibited antimicrobial effects at concentrations as low as 0·03% (v/v). Significantly, cinnamon (Cinnamomum zeylanicum) bark EO exhibited a broad‐spectrum activity against Gram‐negative and Gram‐positive bacteria and showed bacteriostatic and bactericidal effects against P. aeruginosa PAO1 at 0·125% (v/v) and all other tested organisms, including known multidrug resistant species. Time‐kill assays and metabolic activity tests showed cinnamon oil to exhibit rapid killing, with bactericidal activity observed in ≤6 min at ≥0·5% (v/v). Furthermore, scanning electron microscopy and a membrane permeability assay indicated damage to membrane integrity, loss of turgor and cell collapse. Conclusion Cinnamon bark EO is a broad‐spectrum antimicrobial agent capable of rapid killing at low concentrations. Significance and Impact of the Study This study provides a sound basis for further investigation of the potential of cinnamon bark EO as an alternative to conventional antimicrobial products due to its fast‐acting bactericidal properties at low concentrations.

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