Institute of Arctic Biology, Irving I, University of Alaska, Fairbanks, AK 99775, USA.
New Phytol. 2011 Jan;189(1):295-307. doi: 10.1111/j.1469-8137.2010.03472.x. Epub 2010 Sep 24.
• Following the decades-long warming and drying trend in Alaska, there is mounting evidence that temperature-induced drought stress is associated with disease outbreaks in the boreal forest. Recent evidence of this trend is an outbreak of Cytospora canker disease (fungal pathogen Valsa melanodiscus (anamorph = Cytospora umbrina)) on Alnus species. • For Alnus fruticosa, we examined the effects of water stress on disease predisposition, and the effects of disease and water stress on host physiology. In two trials, we conducted a full-factorial experiment that crossed two levels of water stress with three types of inoculum (two isolates of V. melanodiscus, one control isolate). • Water stress was not required for disease predisposition. However, the effects of water stress and disease on host physiology were greatest near the peak phenological stage of the host and during hot, dry conditions. During this time, water stress and disease reduced light-saturated photosynthesis (-30%), light saturation point (-60%) and stomatal conductance (-40%). • Our results depended on the timing of water stress and disease in relation to host phenology and the environment. These factors should not be overlooked in attempts to generalize predictions about the role of temperature-induced drought stress in this pathosystem.
在阿拉斯加经历了长达数十年的变暖变干燥的趋势之后，越来越多的证据表明，温度引起的干旱胁迫与北方森林中的疾病爆发有关。这种趋势的最新证据是 Cytospora canker 病（真菌病原体 Valsa melanodiscus（同型 = Cytospora umbrina））在 Alnus 物种上的爆发。
对于 Alnus fruticosa，我们研究了水分胁迫对疾病易感性的影响，以及疾病和水分胁迫对宿主生理学的影响。在两项试验中，我们进行了完全因子实验，将两个水分胁迫水平与三种接种物（V. melanodiscus 的两个分离株，一个对照分离株）交叉。
水分胁迫不是疾病易感性所必需的。然而，水分胁迫和疾病对宿主生理学的影响在宿主物候高峰附近和炎热干燥条件下最大。在此期间，水分胁迫和疾病降低了光饱和光合作用（-30%）、光饱和点（-60%）和气孔导度（-40%）。
我们的结果取决于水分胁迫和疾病与宿主物候和环境的时间关系。在试图概括关于温度引起的干旱胁迫在这个病理系统中的作用的预测时，这些因素不应被忽视。
