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Phytopathology
Prusky, D., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States, Dept. Postharvest Sci. Fresh Produce, Volcani Center, Agricultural Research Organization, Bet Dagan 50250, Israel
McEvoy, J.L., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Saftner, R., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Conway, W.S., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Jones, R., Vegetable Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Penicillium expansum, P. digitatum, and P. italicum acidify the ambient environments of apple and citrus fruit during decay development. They use two mechanisms for this: the production of organic acids, mainly citric and gluconic, and NH 4 + utilization associated with H + efflux. Exposure of P. expansum and P. digitatum hyphae to pH 5.0 increased their citric acid production, compared with the production of organic acids at acidic ambient pH. In decayed fruit, both pathogens produced significant amounts of citric and gluconic acids in the decayed tissue and reduced the host pH by 0.5 to 1.0 units. Ammonium depletion from the growth medium or from the fruit tissue was directly related to ambient pH reduction. Analysis of transcripts encoding the endopolygalacturonase gene, pepg1, from P. expansum accumulated under acidic culture conditions from pH 3.5 to 5.0, suggesting that the acidification process is a pathogenicity enhancing factor of Penicillium spp. This hypothesis was supported by the finding that cultivars with lower pH and citric acid treatments to reduce tissue pH increased P. expansum development, presumably by increasing local pH. However, organic acid treatment could not enhance decay development in naturally acidic apples. Conversely, local alkalinization with NaHCO 3 reduced decay development. The present results further suggest that ambient pH is a regulatory cue for processes linked to pathogenicity of postharvest pathogens, and that specific genes are expressed as a result of the modified host pH created by the pathogens.
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תנאי שימוש
Relationship between host acidification and virulence of Penicillium spp. on apple and citrus fruit
94
Prusky, D., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States, Dept. Postharvest Sci. Fresh Produce, Volcani Center, Agricultural Research Organization, Bet Dagan 50250, Israel
McEvoy, J.L., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Saftner, R., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Conway, W.S., Produce Qual. and Safety Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Jones, R., Vegetable Laboratory, Henry A. Wallace Beltsville A., U.S. Dept. Agric.-Agric. Res. Serv., Beltsville, MD 20705, United States
Relationship between host acidification and virulence of Penicillium spp. on apple and citrus fruit
Penicillium expansum, P. digitatum, and P. italicum acidify the ambient environments of apple and citrus fruit during decay development. They use two mechanisms for this: the production of organic acids, mainly citric and gluconic, and NH 4 + utilization associated with H + efflux. Exposure of P. expansum and P. digitatum hyphae to pH 5.0 increased their citric acid production, compared with the production of organic acids at acidic ambient pH. In decayed fruit, both pathogens produced significant amounts of citric and gluconic acids in the decayed tissue and reduced the host pH by 0.5 to 1.0 units. Ammonium depletion from the growth medium or from the fruit tissue was directly related to ambient pH reduction. Analysis of transcripts encoding the endopolygalacturonase gene, pepg1, from P. expansum accumulated under acidic culture conditions from pH 3.5 to 5.0, suggesting that the acidification process is a pathogenicity enhancing factor of Penicillium spp. This hypothesis was supported by the finding that cultivars with lower pH and citric acid treatments to reduce tissue pH increased P. expansum development, presumably by increasing local pH. However, organic acid treatment could not enhance decay development in naturally acidic apples. Conversely, local alkalinization with NaHCO 3 reduced decay development. The present results further suggest that ambient pH is a regulatory cue for processes linked to pathogenicity of postharvest pathogens, and that specific genes are expressed as a result of the modified host pH created by the pathogens.
Scientific Publication
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