不同湿润持续时间及叶片温度对温室黄瓜霜霉病发生的影响

为探明不同湿润持续时间及叶片温度与黄瓜霜霉病发生的关系,通过观察不同湿润条件下黄瓜霜霉病的初显症时间,计算逐日显症率及累积显症率,并利用热红外成像仪对显症后叶片温度进行连续监测。结果显示,不同湿润持续时间对黄瓜霜霉病的初显症时间、逐日显症率产生影响。叶片湿润持续4 h,黄瓜霜霉病在接种后7.00 d显症;叶片湿润持续12 h,黄瓜霜霉病初显症时间最早,仅为3.25 d。叶片湿润持续时间不同,黄瓜霜霉病初显症时的叶片温度存在显著差异。回归分析表明,初显症时间与最大温差呈显著正相关,与平均温度呈显著负相关。叶片湿润持续4、6 h的病斑出现高峰在显症后第2、3天,逐日显症率分别是37.50%和41.18%,比叶片湿润持续10、12 h的早。显症后期,湿润持续时间4、6、8、10、12 h的病斑累积显症率分别是87.94%、93.71%、90.25%、84.24%和88.36%,差异不显著。表明接种黄瓜霜霉菌Pseudoperonospora cubensis后叶片湿润持续时间越长,潜育期越短,叶片最大温差越小,叶片平均温度越大。

Effects of the duration of leaf wetness and leaf temperature on downy mildew in cucumber

To better understand the effects of different leaf wetness durations on the occurrence of cucumber downy mildew, and to explore the changes in leaf temperature after the infection of downy mildew in cucumber, the initial time of symptomatic appearance, the daily symptom appearance rate, and the accumulative symptom appearance rate of downy mildew at different wetness durations were observed and compared, and the maximum temperature difference and the average temperature of the leaves were continuously monitored using thermal infrared imaging. The results showed that leaf wetness durations had a significant effect on the initial time of symptomatic appearance and the daily symptom appearance rate. After inoculation, leaf wetting for four hours had the longest incubation period of 7.00 days, and wetting for 12 hours had the shortest incubation period of 3.25 days. Leaf temperatures at symptomatic appearance differed significantly between the treatments of different leaf wetness durations. The initial time of symptomatic appearance was significantly and positively correlated with the maximum temperature difference and negatively correlated with the average temperature. Compared with wetting for 10 hours or 12 hours, leaf wetting for four hours or six hours resulted in the appearance peak of lesions at two or three days after symptomatic appearance and a daily symptom appearance rate of 37.50% and 41.18%, respectively. In the late lesions, the cumulative symptom appearance rates for 4, 6, 8, 10, 12 h wetness durations were 87.94%, 93.71%, 90.25%, 84.24% and 88.36%, respectively, with no significant differences. These results indicate that a longer wetness duration caused a shorter P. cubensis incubation period, which further caused a lower maximum temperature difference and a higher average temperature in the leaves.