设施黄瓜细菌性角斑病菌气溶胶形成传播机制及生态防治的基础研究

Microbial aerosol is an important medium for the spread of pathogenic bacteria. However, there are few reports about the occurrence of plant diseases caused by pathogenic aerosols. Cucumber angular leaf spot disease is caused by Pseudomonas syringae pv. lachrymans (Psl), which can cause serious economic losses in cucumber production worldwide. Based on the results of field investigation, angular leaf spot disease can be spread to the whole greenhouse in a week from a center infected plant. It is difficult to explain the phenomenon using traditional transmission route. Previous studies show that Psl strains were detected in the air around the infected plants in the appropriate conditions, which implies that Psl may spread through biological aerosols. Therefore, we speculate that Psl aerosol is an important way for rapid propagation of angular leaf spot disease. However, the formation mechanism, propagation law and environmental factors of Psl aerosols have not been illuminated. In this study, we will study the Psl aerosol in greenhouse cucumber production. The rapid quantitative methods for Psl aerosol detection will be established, and the formation mechanisms and propagation laws of Psl aerosol also will be fully revealed. Meanwhile, the cultivation environmental factors which affect the spread of Psl aerosol also will be naturally revealed. This study will be assistance for proposing practicable and scientific management for angular leaf spot disease, and will have important guiding significance for cucumber safe and green production.

微生物气溶胶是病原细菌传播的重要媒介，但有关病原细菌通过气溶胶传播引起植物病害发生的报道相对较少。黄瓜细菌性角斑病由丁香假单胞流泪致病变种(Pseudomonas syringae pv. lachrymans，Psl)引起，该病分布广泛，危害严重。设施黄瓜生产中，该病可在短期内迅速传播，传统的病害传播途径难以解释该现象。前期研究表明，适宜的温湿条件下，发病黄瓜植株周围的空气中可检测到Psl，能够形成气溶胶，故推测Psl气溶胶是设施黄瓜细菌性角斑病菌快速传播的重要途径。但是，Psl气溶胶形成机制、传播规律以及环境影响因子尚未阐明。本项目以设施黄瓜生产中Psl气溶胶为切入点，通过建立Psl气溶胶快速定量检测体系，深入研究Psl气溶胶的形成机制和传播规律，并揭示影响其传播的环境因子。本研究的开展将有助于提出科学有效的黄瓜细菌性角斑病的生态防治对策，对设施黄瓜的安全、绿色生产具有重要指导意义。

黄瓜细菌性角斑病由扁桃假单胞流泪致病变种（Pseudomonas amygdali pv. lachrymans，简称Pal）引起，给黄瓜产业带来了巨大的经济损失。本项研究以设施黄瓜生产中Pal气溶胶为切入点，通过建立Pal气溶胶快速定量检测体系，深入研究Pal气溶胶的形成机制和传播规律，并揭示影响其传播的环境因子。.（1）明确了发病黄瓜植株是Pal气溶胶的重要来源。在天津、河北和山东地区采集自然发病黄瓜棚室的气溶胶样本中分离得到Pal菌株，均对黄瓜幼苗有致病性；采用qPCR对气溶胶样本中的Pal进行定量分析，均能检测到Pal。而在健康对照棚室的气溶胶样本中未分离出、检测到Pal菌株。.（2）揭示了Pal气溶胶的产生规律、粒径分布特征及致病阈值。在人工构建的气溶胶发生室接种荧光标记菌株Pal::GFP，发现接种黄瓜植株释放Pal::GFP气溶胶浓度随其细菌性角斑病病情指数的增加而降低。Pal::GFP气溶胶的粒径分布在0.65 - > 7.0 μm之间。Pal::GFP气溶胶对黄瓜植株致病阈值是84 - 179 cfu/m3，低于该浓度则不会引起细菌性角斑病，该结果为黄瓜细菌性角斑病的预警提供了理论依据。.（3）Pal::GFP气溶胶可以传播黄瓜细菌性角斑病。通过在气溶胶传播室进行模拟试验，Pal::GFP气溶胶可以传播细菌性角斑病，被传播黄瓜植株的病情指数与Pal::GFP气溶胶浓度呈正相关。在设施温室中设置接种区和非接种区进行传播试验，温室内Pal::GFP气溶胶总细胞数和活细胞数分别为172 - 677 cells/m3和114 - 597 cells/m3。同时对黄瓜细菌性角斑病进行病害调查，发现非接种区黄瓜发生细菌性角斑病，表明黄瓜细菌性角斑病可以由接种区传播至非接种区。因此，Pal::GFP气溶胶是传播黄瓜细菌性角斑病重要途径。.（4）温湿度对Pal::GFP气溶胶的释放、气溶胶中Pal的存活具有重要的影响。低温高湿条件下气溶胶中Pal的存活率和存活时间显著高于高温干燥条件。发病黄瓜在25°C、95% RH条件下，发病黄瓜植株释放的Pal气溶胶的浓度最高；且在该条件下Pal气溶胶引起黄瓜细菌性角斑病的病情指数最高。高温低湿（35°C、35% RH）条件下，Pal气溶胶不能引起黄瓜细菌性角斑病。该研究将为黄瓜细菌性角斑病绿色、高效防控奠定理论基础。