In microscopic analyses of the infection behavior of the fungal pathogen Mycovellosiellanattrassii, causal agent of eggplant leaf mold, fewer appressoria and penetration hyphae formed on UV-B-treated leaves of eggplant than on the control leaves. Phenylalanine ammonia lyase (PAL) and β-1,3-glucanase activities were higher in the UV-B-treated leaves at 5 and 7 days post-treatment, respectively. A 6-h daily exposure of eggplants to UV-B light in the greenhouse reduced the incidence of eggplant leaf mold significantly compared with the control plants. These results suggest that UV-B irradiation to eggplant activates defense-related enzymes and is effective in disease control.
Severe stem rot of cabbage (Brassica oleracea L.) in heading stage has been observed in Gunma Prefecture, Japan since 2004. The causal agent was identified as Pythium ultimum Trow var. ultimum, a pathogen of Pythium rot of cabbage, based on morphological properties and rDNA-ITS sequence. When cabbage stems were inoculated with the isolates, the symptom of disease was reproduced, and the fungus was reisolated from the plants. To our knowledge, this is the first report of stem rot of cabbage in heading stage caused by P. ultimum var. ultimum. We propose adding stem rot as the new symptom of Pythium rot of cabbage.