PREMISE Mortality events involving drought and pathogens in natural plant systems are on the rise due to global climate change. In Santa Barbara, California, United States, big berry manzanita (Arctostaphylos glauca) has experienced canopy dieback related to a multi-year drought and infection from fungal pathogens in the Botryosphaeriaceae family. A greenhouse experiment was conducted using Neofusicoccum australe to test the specific influences of drought and fungal infection on A. glauca. METHODS A full factorial design was used to compare four treatment groups (drought + inoculation; drought - inoculation; watering + inoculation; and control: watering - inoculation). Data were collected for 10 weeks on stress symptoms, changes in leaf fluorescence and photosynthesis, and mortality. RESULTS Results indicated significant effects of watering and inoculation treatments on net photosynthesis, dark-adapted fluorescence, and disease symptom severity (P < 0.05), and a strong correlation was found between physiological decline and visible stress (P < 0.0001). Mortality differed between treatments, with all groups except for the control experiencing mortality (43% mortality in drought - inoculation, 83% in watering - inoculation, and 100% in drought + inoculation). A Kaplan-Meier survival analysis showed drought + inoculation to have the least estimated survivorship compared to all other treatment groups. CONCLUSIONS In addition to a possible synergistic interaction between drought and fungal infection in disease onset and mortality rates in A. glauca, these results indicate that young, non-drought-stressed plants are susceptible to mortality from N. australe infection, with important implications for the future of wildland shrub communities.

中文翻译：

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经典耐旱灌木物种（ Arctostaphylos glauca ）严重枯死和死亡的机制

由于全球气候变化，自然植物系统中涉及干旱和病原体的死亡率事件正在上升。在美国加利福尼亚州圣巴巴拉，大浆果曼扎尼塔 (Arctostaphylos glauca) 经历了与多年干旱和葡萄球菌科真菌病原体感染相关的冠层枯死。使用 Neofusicoccum australe 进行温室试验，以测试干旱和真菌感染对 A. glauca 的具体影响。方法 全因子设计用于比较四个处理组（干旱 + 接种；干旱 - 接种；浇水 + 接种；对照：浇水 - 接种）。收集了 10 周的压力症状、叶片荧光和光合作用的变化以及死亡率的数据。结果 结果表明，浇水和接种处理对净光合作用、暗适应荧光和疾病症状严重程度有显着影响（P < 0.05），生理衰退与可见压力之间存在很强的相关性（P < 0.0001）。处理之间的死亡率不同，除对照组外的所有组都经历死亡率（干旱 - 接种死亡率为 43%，浇水 - 接种死亡率为 83%，干旱 + 接种死亡率为 100%）。Kaplan-Meier 生存分析显示，与所有其他处理组相比，干旱 + 接种的估计存活率最低。结论 除了干旱和真菌感染在 A. glauca 的发病率和死亡率之间可能存在协同作用外，这些结果表明，年轻、