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Research Project:
Development and Evaluation of New Technologies to Manage Postharvest Decay of Citrus
Location: Commodity Protection and Quality
2006 Annual Report
4d.Progress report.
This report serves to document research conducted under a trust agreement between ARS and the Citrus Research Board to develop new methods to control postharvest decay of citrus fruit. Additional details of research can be found in the report for the parent CRIS 5302-43000-032-00D Emerging Technologies to Maintain Postharvest Quality and Control Decay of Fresh Commodities. Objectives of this project are to reduce postharvest decay losses of fresh citrus fruit caused by fungal pathogens, such as green mold, caused by Penicillium digitatum, and sour rot, caused by Geotrichum citri-aurantii. The most significant new findings in 2006 include the characterization of fungicide resistance in populations of P. digitatum and methods to manage fungicide resistant isolates. Molecular analysis of fungicide resistant isolates of P. digitatum collected from many locations were completed. Resistance to fungicide thiabendazole was associated with mutations at codon 200 of the beta-tubulin gene, and resistance to the fungicide imazalil was associated with up-regulation of cytochrome p450 expression by one of two patterns of alteration in regulatory sequences associated with cytochrome p450 synthesis. The growth and virulence and many other aspects of a large collection of isolates was conducted, and acquisition of fungicide resistance was accompanied by small but significant reductions in growth rate and competitive ability. Development of measures to minimize the development of fungicide resistance, by using mixtures of these fungicides with GRAS compounds or avoiding their use, are in progress.
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Last Modified: 03/24/2010
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