Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2001
Publication Date: June 1, 2001
Why do fungi cause disease in specific hosts, but not in others? Part of the answer may lie in the unique chemical composition of the host. Pencillium digitatum and P. italicum readily invade injuries in the rind of citrus fruits. P. expansum has a broad host range, but is not pathogenic on citrus. Pummelo fruit were cured 48 h, and 70% ethanol extracts were prepared from intact and injured peel. Extracts were dried onto filter paper discs, potato dextrose broth (PDB) was added, and growth of the fungi after 24 h were measured by conversion of a vital stain. Intact peel extract stimulated growth of both citrus pathogens at a dilution of 1/200, but growth of P. expansum was unaffected. At concentrations comparable to tissue levels, growth of citrus pathogens increased nearly 10-fold, while growth of P. expansum only doubled. Injured peel extract stimulated growth of citrus pathogens when compared to PDB, but was inhibitory relative to intact peel extract. Peel extracts selectively stimulated growth of pathogenic Penicillium species. Identification of the active components will enhance our understanding of specificity in this disease interaction.