Submitted to: American Phytopathology Society
Publication Type: Abstract only
Publication Acceptance Date: 4/15/2007
Publication Date: 7/10/2008
Citation: Macarisin, D., Cohen, L., Eick, A., Rafael, G., Wisniewski, M.E., Droby, S. 2008. Pathogenicity of Penicillium digitatum is associated with the suppression of the defense-related hydrogen peroxide burst in citrus fruit. American Phytopathology Society. San Diego, CA 97: S-69. Interpretive Summary:
Technical Abstract: The high susceptibility of citrus fruit to green mold disease and lack of resistance responses suggest that P. digitatum has the ability to suppress host defenses. The current study demonstrated that during infection, P. digitatum suppresses the defense-related oxidative burst in host cells. In contrast, the non-compatible pathogen, P. expansum, triggers production of a significant amount of H2O2 in citrus fruit exocarp. Using laser scanning confocal microscopy, we demonstrated in vivo that P. digitatum did not induce a substantial elevation in H2O2 within 40-42 h after inoculation, while the level of H2O2 around the wounds inoculated with P. expansum exceeded by 63-fold the H2O2 level present in the control. P. digitatum continued to suppress H2O2 production in citrus fruit exocarp 60-66 h after inoculation, and in fact, H2O2 levels were approximately three fold below that of non-inoculated controls. In contrast, the H2O2 level was about 11-fold above the control value in wound sites inoculated with P. expansum. Studies on the effect of organic acids (as pH modulators) and H2O2-scavenging enzymes on the response of citrus fruit to compatible and non-compatible pathogens suggest that citric acid and catalase act as virulence factors for P. digitatum in green mold pathogenesis.