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Postharvest Pathology and Mycotoxins

Promotion of Infection of Orange Fruit by Penicillium digitatum with a Strain of Pseudomonas cepacia. Yong Huang, Department of Plant Pathology and Agricultural Entomology, University of Sydney, NSW 2006, Australia; B. J. Deverall(2), and S. C. Morris(3). (2)Department of Plant Pathology and Agricultural Entomology, University of Sydney, NSW 2006, Australia; (3)Sydney Laboratories, CSIRO Division of Horticulture, P.O. Box 52, North Ryde, NSW 2113, Australia. Phytopathology 81:615-618. Accepted for publication 7 December 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-615.

Susceptibility of wounds in orange fruit to infection by Penicillium digitatum decreased during periods of healing at 25 C and more so at 30 C. Healing was correlated with lignification in wounded tissue and phenylalanine ammonia-lyase (PAL) activity that was 0.2 units per milligram of protein per hour in fresh wounds and, after 72 h, was 5.9 units at 25 C and 8.8 units at 30 C. A strain of Pseudomonas cepacia (ID 2129), added to fresh wounds, suppressed the healing process as revealed by slower lignification, a PAL activity after 72 h of 1.1 units at 25 and 30 C, and a high susceptibility to infection by P. digitatum. The suppression was probably caused by a diffusible metabolite from P. cepacia present also in culture filtrates of the bacterium.

Additional keywords: wound healing.