| In the fall of 2000, we first observed grapes with unusual symptoms. The symptoms consisted of individual and groups of adjacent berries with a watery appearance on the berry surface, disintegrated tissue, hairline cracks and wounds on the berries, flaccid berries, and the presence of “slip-skin.” Bacteria and yeasts cultured from the samples were isolated, purified, grouped, and screened for pathogenicity. One yeast (Hanseniaspora guilliermondii Pijper), and four bacteria (three were Bacillus subtilis and one was Bacillus licheniformis) were determined to be pathogenic, and were later identified. In all cases, infection occurred only in wound-inoculated berries. Inoculating wounded ‘Redglobe’ berries with different mixtures of purified microorganisms had a synergistic effect, resulting in larger lesions and greater incidence and severity of hairline and severe cracks compared to single isolate inoculations. Disease development occurred in wounded ‘Redglobe’ berries inoculated with a mix of purified microorganisms and incubated at both 0°C and 25°C. |
