Interlaboratory performance of a Real-Time PCR method for detection of Ceratocystis platani, the agent of canker stain of Platanus spp

Ceratocystis platani (CP), an ascomycetous fungus, is the agent of canker stain, a lethal vascular disease of Platanus species. Ceratocystis platani has been listed as a quarantine pest (EPPO A2 list) due to extensive damage caused in Southern Europe and the Mediterranean region. As traditional diagnostic assays are ineffective, a Real-Time PCR detection method based on EvaGreen, SYBR Green, and Taqman assays was previously developed, validated in-house, and included in the official EPPO standard PM7/14 (2). Here, we describe the results of a test performance study performed by nine European laboratories for the purpose of an interlaboratory validation. Verification of the DNA extracted from biological samples guaranteed the high quality of preparations, and the stability and the homogeneity of the aliquots intended for the laboratories. All of the laboratories reproduced nearly identical standard curves with efficiencies close to 100%. Testing of blind-coded DNA extracted from wood samples revealed that all performance parameters-diagnostic sensitivity, diagnostic specificity, accuracy and reproducibility-were best fit in most cases both at the laboratory and at the assay level. The previously established limit of detection, 3 fg per PCR reaction, was also validated with similar excellent results. The high interlaboratory performance of this Real-Time PCR method confirms its value as a primary tool to safeguard C. platani-free countries by way of an accurate monitoring, and to investigate the resistance level of potentially canker stain-resistant Platanus genotypes

Inter-laboratory validation of PCR-based protocol for detection of olive viruses

Sanitary selection and certification of olive cultivars require sensitive diagnostic methods and effective sanitation protocols. Although much attention has been paid in the past few years to the development of diagnostic tools for reliable virus identification, the need to define a common and standardized diagnostic protocol led to the implementation of a ring test among nine Italian diagnostic laboratories. A one-step RT-PCR protocol and different primer sets, targeting the most common olive viruses covered by phytosanitary rules, were tested in each laboratory, using the same batch of positive and healthy controls as well as the same amplification conditions and reaction components. The one-step RT-PCR, performed using several specific primer sets, was able efficiently to detect the target viruses in all laboratories. Furthermore, a one-step RT-PCR protocol was used successfully for the first time for detection of Tobacco necrosis virus (TNV) and Olive mild mosaic virus (OMMV). Results showed that all target viruses were not uniformly distributed in the canopy, and that at least two subsets of samples must be collected from each plant. This standardized protocol is now being used to produce nuclear stocks for 70 different Italian olive cultivars, in the framework of the national project OLVIVA, which involves 25 national research institutions