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Fungal pathogens of canker disease trigger canopy dieback in poplar saplings by inducing functional failure of the phloem and cambium and carbon starvation in the xylem
Physiological and Molecular Plant Pathology ( IF 2.7 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.pmpp.2020.101523
Junchao Xing , Ping Li , Yinan Zhang , Jinxin Li , Ya Liu , Barbara Lachenbruch , Xiaohua Su , Jiaping Zhao

Abstract Tree canker diseases are mainly caused by necrotrophic fungal pathogens, which induce canker lesions, wilting, or dieback in many species. We hypothesized that canker-associated canopy dieback is related to functional failure of the phloem and cambium, carbon starvation and/or hydraulic failure. Using a girdling and inoculation system, we evaluated gas exchange and hydraulic parameters, concentrations of non-structural carbohydrates (NSCs), leaf characteristics, stem phenotyping and symptoms of 6-month-old poplar saplings with Botryosphaeria or Valsa canker disease. Pathogen inoculations inhibited callus formation and phloem regeneration and altered the physiological parameters, water potential, NSC content in stems, and symptoms on leaves and stems, while the girdling-only control did not. Results suggest that the functional and structural integrity of the phloem and cambium play crucial roles in the pathogenesis of canker disease. Botryosphaeria canker decreased photosynthetic rate (−54% to −75%), stomatal conductance (−71% to −80%) and transpiration rate (−58% to −66%), while Valsa canker decreased photosynthetic rate (−53% to −83%), stomatal conductance (−71% to −87%) and transpiration rate (−53% to −76%) at 20, 25, and 30 days after inoculation. Results suggest that the two fungal pathogens induce carbon starvation by inhibiting photosynthesis. The leaf water potential was higher and the change in specific hydraulic conductivity was smaller in the canker region than in the adjacent regions, while the NSC content was lower in the region below cankers than above them, suggesting that the fungal pathogens caused poplar canopy dieback by initially inducing carbon starvation, not hydraulic failure.

中文翻译:

溃疡病的真菌病原体通过诱导韧皮部和形成层的功能衰竭以及木质部的碳饥饿引发杨树树苗的冠层枯死

摘要 树木溃疡病主要是由坏死性真菌病原体引起的,可引起许多物种的溃疡病、枯萎或枯死。我们假设溃疡相关的冠层枯死与韧皮部和形成层的功能故障、碳饥饿和/或液压故障有关。使用环剥和接种系统,我们评估了气体交换和水力参数、非结构性碳水化合物 (NSC) 的浓度、叶特征、茎表型和 6 个月大的葡萄球菌或瓦尔萨溃疡病杨树树苗的症状。病原体接种抑制愈伤组织形成和韧皮部再生,并改变生理参数、水势、茎中 NSC 含量以及叶和茎上的症状,而仅环剥对照则没有。结果表明韧皮部和形成层的功能和结构完整性在溃疡病的发病机制中起着至关重要的作用。Botryosphaeria 溃疡病降低了光合速率(-54% 至 -75%)、气孔导度(-71% 至 -80%)和蒸腾速率(-58% 至 -66%),而 Valsa 溃疡病降低了光合速率(-53% 至 -80%)接种后 20、25 和 30 天的 -83%)、气孔导度(-71% 至 -87%)和蒸腾速率(-53% 至 -76%)。结果表明,这两种真菌病原体通过抑制光合作用导致碳饥饿。溃疡病区叶片水势较高,比水力传导率变化小于邻近区域,而溃疡病区以下区域的NSC含量低于其以上区域,
更新日期:2020-12-01
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