Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Université de Lorraine, INRAE, IAM, Nancy, France.
Plant Cell Environ. 2022 Aug;45(8):2292-2305. doi: 10.1111/pce.14360. Epub 2022 May 31.
Pathogenic diseases frequently occur in drought-stressed trees. However, their contribution to the process of drought-induced mortality is poorly understood. We combined drought and stem inoculation treatments to study the physiological processes leading to drought-induced mortality in Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) saplings infected with Heterobasidion annosum s.s. We analysed the saplings' water status, gas exchange, nonstructural carbohydrates (NSCs) and defence responses, and how they related to mortality. Saplings were followed for two growing seasons, including an artificially induced 3-month dormancy period. The combined drought and pathogen treatment significantly increased spruce mortality; however, no interaction between these stressors was observed in pine, although individually each stressor caused mortality. Our results suggest that pathogen infection decreased carbon reserves in spruce, reducing the capacity of saplings to cope with drought, resulting in increased mortality rates. Defoliation, relative water content and the starch concentration of needles were predictors of mortality in both species under drought and pathogen infection. Infection and drought stress create conflicting needs for carbon to compartmentalize the pathogen and to avoid turgor loss, respectively. Heterobasidion annosum reduces the functional sapwood area and shifts NSC allocation patterns, reducing the capacity of trees to cope with drought.
病原性疾病经常在遭受干旱胁迫的树木中发生。然而，它们对干旱引起的死亡率过程的贡献还不太清楚。我们将干旱和茎接种处理相结合，研究了感染 Heterobasidion annosum s.s. 的挪威云杉（Picea abies）和欧洲赤松（Pinus sylvestris）幼树导致干旱引起的死亡率的生理过程。我们分析了幼树的水分状况、气体交换、非结构性碳水化合物（NSCs）和防御反应，以及它们与死亡率的关系。幼树在两个生长季节中进行了监测，包括人为诱导的 3 个月休眠期。干旱和病原菌的综合处理显著增加了云杉的死亡率；然而，在松树上没有观察到这些胁迫之间的相互作用，尽管单独的每种胁迫都会导致死亡率。我们的研究结果表明，病原菌感染降低了云杉的碳储备，降低了幼树应对干旱的能力，导致死亡率增加。在干旱和病原菌感染下，两种物种的针叶脱落、相对水分含量和淀粉浓度都是死亡率的预测因子。感染和干旱胁迫分别为了 compartmentalize 病原菌和避免膨压损失对碳提出了相互冲突的需求。Heterobasidion annosum 减少了功能边材面积，并改变了 NSC 分配模式，降低了树木应对干旱的能力。
