Abstract: Cauliflower downy mildew is one of the major fungal diseases affecting its production and quality. In order to explore the effects of genotype, environment and their interaction effect on the disease index of cauliflower downy mildew, four varieties of cauliflower (Xiamei 80, Xueyuan 80, 830-F and Huang 80) were artificially inoculated, and the disease index in three developmental stages under four field conditions with different temperatures and relative humidities were investigated. The correlations between the disease index of cauliflower downy mildew and five meteorological factors including temperature, humidity, temperature difference between day and night, accumulated temperature and sunshine hours were also analyzed.The results showed that the contribution rate order to the resistance of cauliflower downy mildew was genotype>environment>genotype and environment interaction,the variation ranges were 77.52%~87.04%, 12.33%~19.94%, 0.63%~2.54%, respectively. Huang 80 had strong resistance to downy mildew and could be used as a resistance resource for breeding.The resistance to downy mildew was significant positive correlated with daily average humidity and temperature difference between day and night,significant negative correlated with daily average temperature and accumulated temperature, and had no significant relationship with sunshine hours. Above all, low temperature and high humidity might aggravate the incidence of downy mildew cauliflower. Measures such as selecting resistant varieties, paying attention to heat preservation, maintaining ventilation in autumn and winter could effectively reduce downy mildew.

Key words: cauliflower, downy mildew, genotype, temperature, humidity, interaction effect