叶片水分亏缺对猕猴桃细菌性溃疡病抗性的影响

Effect of leaf water deficit on resistance to bacterial canker in kiwifruit

关键词:  水分亏缺, 猕猴桃细菌性溃疡病, 湿度, 抗性机制, Psa, 抗氧化酶

Key words:  water deficit, bacterial canker of kiwifruit, humidity, resistance mechanism, Pseudomonas syringae pv. actinidiae, antioxidant enzymes

摘要:

为明确水分条件与猕猴桃溃疡病菌(Psa)感染的关联机制,该研究以高感病的‘红阳'猕猴桃为材料,设置空气相对湿度(60%±2%)的亏缺组和(90%±2%)的高湿组,采用菌落计数、荧光观察、扫描电镜等方法,探究适度水分亏缺处理对溃疡病的影响及机理。结果表明:(1)提前水分亏缺处理的植株初始过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、谷胱甘肽还原酶(GR)和苯丙氨酸解氨酶(PAL)的酶活性更高,气孔开度更低,接菌12 天后叶片病原菌数量仅约为高湿组的1/5。(2)高湿组带病植株转入水分亏缺环境处理7天后叶片荧光出现弥散现象,处理12 天时病原菌消亡率高达99.38%,并且该处理可有效诱导叶片水势降低、气孔关闭以及抗氧化酶系统活性显著上升。综上,水分亏缺处理可通过降低叶片水势、促使气孔关闭减少病原菌入侵,同时调控抗氧化酶活性增强植株抗性,不仅能抑制Psa的侵染与增殖,还能杀灭植株组织内已定殖的病原菌。该研究证实适度水分亏缺处理可有效防控猕猴桃细菌性溃疡病,丰富“水分-植物-病原体”互作体系的研究内容,为猕猴桃细菌性溃疡病的防控提供了新的思路与理论参考,也为控雨栽培等田间水分调控措施的推广应用奠定了理论基础。

Abstract:

To clarify the correlation mechanism between moisture conditions and Pseudomonas syringae pv. actinidiae(Psa)infection in kiwifruit, this study used the highly susceptible cultivar ‘Hongyang' with two relative humidity treatments: 60%±2%(water deficit group)and 90%±2%(high humidity group). Colony counting, fluorescence observation, and scanning electron microscopy were employed to investigate the effects and mechanisms of moderate water deficit treatment on bacterial canker. The results were as follows:(1)Plants under early water deficit treatment exhibited higher initial activities of catalase(CAT), superoxide dismutase(SOD), glutathione reductase(GR)and phenylalanine ammonia-lyase(PAL), lower stomatal aperture, and had only about 1/5 of the pathogen load in leaves compared to the high humidity group after 12 days inoculation.(2)When infected plants from the high humidity group were transferred to water deficit conditions, leaf fluorescence showed diffuse patterns after 7 days, and pathogen mortality reached 99.38% after 12 days of treatment; this treatment effectively induced a decrease in leaf water potential, stomatal closure, and significantly enhanced antioxidant enzyme activities. In conclusion, water deficit reduces pathogen invasion by decreasing leaf water potential and promoting stomatal closure, while enhancing plant resistance through antioxidant enzyme regulation, not only inhibiting Psa infection and proliferation but also eliminating established pathogens. This study confirms that moderate water deficit effectively controls kiwifruit bacterial canker, enriches the “water-plant-pathogen” interaction framework. It provides new ideas and theoretical references for the prevention and control of bacterial canker in kiwifruit, and also lays a theoretical foundation for the popularization of field water management strategies such as rain-sheltered cultivation.