PCR and qPCR are important methods for plant disease diagnosis and quantification of pathogen populations in host tissues or soil. For most plant diseases, DNA extracted from infected tissue or soil is a prerequisite for PCR or qPCR. The efficiency of DNA extraction should have a direct impact on the sensitivity of PCR and qPCR systems. In this study, plant pathogen DNA extraction efficiencies were evaluated based on three plant disease systems and three DNA extraction methods. DNA of bacterial (Pectobacterium atrosepticum), protist (Plasmodiophora brassicae) and fungal (Botrytis cinerea) pathogens was extracted and aliquots were prepared. Aliquots of the DNA were mixed with healthy tissues of the corresponding host plant and DNA was extracted again from the mixture. The resultant mixed DNA, as well as the original pathogen DNA, were analysed by qPCR to assess the quantities of the pathogen DNA. Extraction efficiency was calculated based on the qPCR Cq values of the mixed DNA and the original pathogen DNA for each extraction method on each pathogen. Our results indicated the pathogen DNA extraction efficiencies were generally less than, or near, 50%. This result called attention to the importance of: 1) including the DNA extraction efficiency in the evaluation and announcement of new qPCR diagnostic systems, and 2) developing and using high efficient DNA extraction methods in plant disease diagnosis and pathogen quantification.

PCR和qPCR是用于植物病害诊断和定量宿主组织或土壤中病原体种群的重要方法。对于大多数植物病害，从受感染的组织或土壤中提取的DNA是PCR或qPCR的前提条件。DNA提取的效率应直接影响PCR和qPCR系统的灵敏度。在这项研究中，基于三种植物病害系统和三种DNA提取方法对植物病原体DNA提取效率进行了评估。细菌（Pectobacterium atrosepticum），原生生物（Plasmodiophora brasicae）和真菌（灰葡萄孢）的DNA）提取病原体并准备等分试样。将DNA的等分试样与相应宿主植物的健康组织混合，并再次从混合物中提取DNA。通过qPCR分析所得的混合DNA以及原始病原体DNA，以评估病原体DNA的数量。根据每种病原体上每种提取方法的混合DNA和原始病原体DNA的qPCR Cq值计算提取效率。我们的结果表明，病原体的DNA提取效率通常小于或接近50％。该结果引起人们对以下方面的重要性的关注：1）在新qPCR诊断系统的评估和发布中包括DNA提取效率，以及2）在植物病害诊断和病原体定量中开发和使用高效的DNA提取方法。