ABSTRACT We evaluated sporangium and zoospore production by three isolates of Phytophthora ramorum on Rhododendron ‘Cunningham’s White’ leaves under light and dark conditions at both variable and constant (14 C) temperature. P. ramorum–infected leaves were detached and placed in funnels inside of a 62-L plastic storage container located in a growth chamber. Cool mist was introduced to the container to create a high-humidity environment. Sporangia and zoospores were collected over a 4-day period by misting leaves with 5 mL of distilled water, which was collected in conical test tubes that also contained runoff from the misting. Spores were collected daily just before a 13-h light period and again just before an 11-h dark period. Sporangia and zoospores in the collection tubes were counted using a dissecting microscope following staining with lactoglycerin/aniline blue. Large differences in sporangium and zoospore numbers observed for the dark versus light periods were observed on days 2, 3, and 4. A diurnal effect has been observed for production of propagules of other oomycetes, but such effects have not been previously reported for P. ramorum. This information will help provide a better understanding of patterns of inoculum production by P. ramorum and resulting fluctuations in inoculum density that will influence sudden oak death epidemics in forest ecosystems in the United States and other countries where it occurs.

中文翻译：

---

Phytophthora ramorum 对'Cunningham's White'杜鹃花孢子囊和游动孢子产生的昼夜影响

摘要 我们评估了 Phytophthora ramorum 的三个分离株在光照和黑暗条件下在可变和恒定 (14 C) 温度下在杜鹃花 'Cunningham's White' 叶子上的孢子囊和游动孢子的产生。将 P. ramorum 感染的叶子分离并放置在位于生长室中的 62 升塑料储存容器内的漏斗中。冷雾被引入容器以创造高湿度环境。孢子囊和游动孢子通过用 5 mL 蒸馏水雾化叶子在 4 天的时间内收集，将其收集在锥形试管中，该试管也包含来自雾化的径流。每天在 13 小时光照期之前和 11 小时黑暗期之前收集孢子。在用乳甘油/苯胺蓝染色后，使用解剖显微镜计数收集管中的孢子囊和游动孢子。在第 2、3 和 4 天，观察到在黑暗与光明时期观察到的孢子囊和游动孢子数量存在很大差异。 已经观察到其他卵菌的繁殖体产生的昼夜效应，但以前没有报道过这种影响对于 P.拉莫鲁姆。此信息将有助于更好地了解 P. ramorum 接种物的生产模式以及由此产生的接种物密度波动，这将影响美国和其他国家的森林生态系统中的橡树猝死流行病。已经观察到其他卵菌的繁殖体产生的昼夜效应，但以前没有报道过这种效应对 P. ramorum 的影响。此信息将有助于更好地了解 P. ramorum 接种物的生产模式以及由此产生的接种物密度波动，这将影响美国和其他国家的森林生态系统中的橡树猝死流行病。已经观察到其他卵菌的繁殖体产生的昼夜效应，但以前没有报道过这种效应对 P. ramorum 的影响。此信息将有助于更好地了解 P. ramorum 接种物的生产模式以及由此产生的接种物密度波动，这将影响美国和其他国家的森林生态系统中的橡树猝死流行病。