Evaluation of the real-time PCR applicability for the identification of bacterial ear rot of wheat Rathayibacter tritici

Bacterial ear rot of wheat Rathayibacter tritici (Carlson & Vidaver) Zgurskaya et al. is included in the Common List of Quarantine Pests of the Eurasian Economic Union. Rapid identification of the pathogen is an important element in the field of plant quarantine. The “real time” PCR method (real-time PCR) is the most optimal for laboratory diagnosis. Currently, there are only two real-time PCR tests for identification of Rathayibacter tritici developed by Postnikova et al., 2017. The tests are designed to identify Rathayibacter tritici in pure bacterial cultures. The original article does not contain information on the values of the main parame- ters of the real-time PCR test applicability – analytical specificity, including exclusivity and inclusivity, and analytical sensitivity, as well as on testing the test for detecting the pathogen in plant samples. The aim of this work was to assess the applicability of previously known real-time PCR tests for the identification of R. tritici. The study materials were R. tritici strains, as well as 26 strains of bacteria of the genus Rathayibacter, including all existing species within this genus. As a result of assessing the applicability of real-time PCR tests for the identification of the causative agent of bacterial ear rot of wheat Rathayibacter tritici, it was found that the inclusivity value – the ability of the test to identify the entire diversity of bacterial strains within a species – for the studied tests is 83.3%. The use of these tests allowed us to identify 5 out of 6 strains of the target object – Rathayibacter tritici. The exclusivity value – the ability of the test to distinguish target strains from non-target ones – was 100% for both tests. The real-time PCR tests developed by Postnikova et al., 2017, despite their high exclusivity (100%), are not applicable for phytosanitary diagnosis, since in the case of their use the risk of false negative results and, as a consequence, the introduction of the quarantine pest into new territories is quite high.

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