Data_Sheet_1_Response of Alnus glutinosa to Phytophthora bark infections at ambient and elevated CO2 levels.PDF

IntroductionMortality of the riparian alder population caused by Phytophthora pathogens has been studied for over 20 years throughout Europe, recently gaining more importance in the context of evident climate change. The main objective of this study was to examine the pathogenicity of species from the “Phytophthora alni complex” present in the Czech Republic (P. × alni and P. uniformis) and P. plurivora to Alnus glutinosa seedlings grown at ambient and elevated CO2 concentration.
MethodsAn underbark inoculation test was performed with seedlings grown from seeds collected from two Czech alder populations, one suffering from severe Phytophthora decline and the other disease-free.
ResultsThe results showed significant differences in lesion development and seedling mortality. After a 13-week experimental period, at both CO2 levels P. × alni and P. uniformis showed high aggressiveness to A. glutinosa seedlings causing lesions of variable sizes and mortality of 33.3%, and 45.8% of plants, respectively. In contrast, P. plurivora did not cause mortality to any plant, and lesion sizes did not differ significantly from those in control plants. Physiological measurements did not reveal any significant differences between Phytophthora species except for plants inoculated with P. plurivora showing increased values in specific physiological parameters 4 weeks post-inoculation. Net photosynthesis decreased over the measurement period in all treatments with significant differences found between measurements conducted 2 and 4 weeks after the inoculation. Transpiration showed a decreasing trend in all inoculated plants with no significant differences between Phytophthora species at both CO2 levels. Chemical analyses of root samples showed high variability in sugars and phenolic compounds related to the plant's health status.
DiscussionThis is the first study to examine the response of alder seedlings to Phytophthora pathogens at different CO2 levels. The findings demonstrate high aggressiveness of P. × alni and P. uniformis and weaker aggressiveness of P. plurivora to alder seedlings regardless of the CO2 level.

研究背景：欧洲范围内针对疫霉属（Phytophthora）病原菌引发的河岸桤木种群死亡率已开展超20年的研究，近年来在气候变化日益显著的背景下，该议题愈发受到重视。本研究的核心目标为：探究捷克境内存在的“桤木疫霉复合群（Phytophthora alni complex）”物种（即P. × alni与P. uniformis）以及P. plurivora，对在常态与升高二氧化碳浓度下培育的欧洲桤木（Alnus glutinosa）实生苗的致病力。
试验方法：本研究采用从两个捷克桤木种群采集的种子培育的实生苗开展树皮下接种试验，其中一个种群曾遭受严重的疫霉病害衰退，另一个种群则无病害记录。
试验结果：试验组间的病斑发育与实生苗死亡率存在显著差异。在为期13周的试验周期内，两种二氧化碳浓度水平下，P. × alni与P. uniformis均对欧洲桤木实生苗表现出强致病力，分别导致33.3%与45.8%的植株死亡，病斑大小存在差异；与之相对，P. plurivora未造成任何植株死亡，其病斑大小与对照组无显著差异。生理指标检测结果显示，除接种P. plurivora的植株在接种4周后部分生理参数数值升高外，其余疫霉物种侵染的植株间未出现显著差异。所有处理组的净光合速率随检测周期推进均有所下降，且接种后第2周与第4周的检测结果间存在显著差异。所有接种处理的植株蒸腾速率均呈下降趋势，且两种二氧化碳浓度下不同疫霉物种间的蒸腾速率无显著差异。根系样本的化学分析显示，与植株健康状态相关的糖类与酚类化合物含量存在较高变异性。
讨论：本研究为首项针对不同二氧化碳浓度下桤木实生苗对疫霉病原菌响应的相关研究。研究结果表明，无论二氧化碳浓度水平如何，P. × alni与P. uniformis均表现出强致病力，而P. plurivora的致病力较弱。