Study on the Biological Characteristics of Erysiphe necator (Syn. Uncinula necator), the Causal Agent of Grape Powdery Mildew Disease in Meshkinshahr

Grape powdery mildew، Erysiphe necator، economicallyis one of the most important diseases of grapevine around the world including Iran، and it may cause considerable damage to vineyards under appropriate conditions for the disease progress. In order to study the biology of the causal agent as well as primary inoculums sources for the establishment of the epidemic، an experiment was carried out in the Meshkinshahr in 1387-1389. Results of the histopathological experiments showed that the fungus survives as mycelia in the dormant infected buds of the grapevine during the winter. Results on the study of the effect of environmental factors on the biology of the causal agent revealed that the temperature range between 16-19°C for 4 days and the relative humidity above 50% favor the growth and activity of the causal agent in the beginning of the growth season. Our results also showed that optimum temperature and relative humidity for the sporulation of the causal agent was 20-25°C and 50-100% respectively with weak light. Fungal conidia were trapped during the formation of 5-6 true leaves and after post bloom. Disease colonies were first observed in the fruit formation and buckshot berries stages. Fungal chasmothecia were observed abundantly at the end of growth season on the leaves، petioles and twigs but they were not able to survive during winter. Our results also revealed that ascospores were not pathogenic on young leaves.