Detecting Spiroplasma citri: a comparison of PCR methods to be used for quarantine diagnostics

Spiroplasma citri, a plant pathogenic bacterium responsible for citrus stubborn disease in citrus, is listed as a quarantine pest in Europe and in other parts of the world. For this reason, the introduction of this pathogen is prohibited in many countries and post-entry quarantine is required for imported citrus plants. Therefore, reliable and highly sensitive detection methods are required to test plants in post-entry quarantine. This paper presents a study that characterizes the test parameters of a number of PCR protocols for the detection of S. citri. First, during intra-laboratory evaluation, we characterized four PCR methods and selected three of them. Second, those three methods were compared in the framework of an inter-laboratory study involving five laboratories. As a result, the real-time PCR developed by Yokomi et al. (Plant Disease, 92, 253-60, 2008) targeting the putative gene of the adhesin P58 is recommended for routine use in post-entry quarantine.