Report of the Test Performance Study: Molecular detection of Xylella fastidiosa through quantitative real time assays- Implementation of the Proficiency test EU-XF- PT-2017-02. This interlaboratory validation followed the proficiency test (PT) EU-XF- PT-2017-02 carried out in early 2017, and aimed to assess the performance and the accuracy of different qPCR assays to detect Xylella fastidiosa in host plants. In the framework of this test performance study (TPS), five different qPCR assays were compared using a common panel of DNA templates. DNA extracts were those previously recovered in the framework of the PT EU-XF- PT-2017-02,  from olive tissues spiked with bacterial suspension of X. fastidiosa subsp. pauca strain De Donno, at known concentrations (CFU/ml). More specifically, the DNA extracts used in this TPS were  recovered from artificially contaminated olive sap, processed using either the DNeasy® mericon™ Food kit (Qiagen) or the CTAB-based extraction protocol.