Ulocladium botrytis Preuss was isolated from spotted tomato leaves of "Pritchard variety" Symptoms are characterized by irregular lesions, dark-gray becoming black with time, mostly begin at the margins and extending to the main vein of leaflets. Also longitudinal dark-gray necrotic lesions are noticed on petioles and on the stem, and some axillary buds were blackened and necrosed.
Pathogenicity tests showed typical disease symptoms after 4 - 7 days incubation. "Cal Ice" variety was highly susceptible to infection, whereas "Super Marmande" was resistant and "Pritchard" moderately resistant.
Morphological characteristics of the pathogen were found to fit with the species description of Ulocladium botrytis Preuss. This identification was confirmed by the Commonwealth Mycological Institute, Kew, Surrey, England.
Profuse sporulation and good growth rate of the pathogen were obtained on Czapecks-Dox agar containing glucose or sucrose as a carbon source and sodium nitrate as a nitrogen source followed by asparagine. Optimum pH was pH 6.0 or slightly lower and temperatures from 21-25°C were most favourable. Continuous light exposure seemed to be essential for maximum sporulation. Red light was also optimum while the blue light and continuous darkness seemed to be suppressive. |
