Applicability assessment of PCR methods for the diagnosis of bacterial canker in tomato

Bacterial canker of tomato is a harmful disease widespread in tomato crops. The pathogen Clavibacter michiganensis (Smith; Davis et al.) Li et al. exhibits particular virulence in protected ground conditions. Rapid and accurate detection of C. michiganensis in tomato seeds using modern diagnostic methods can help reduce the risk of disease spread and improve crop yield and product quality. The study was conducted at the Laboratory of the Research and Methodology Department of Bacteriology, All-Russian Plant Quarantine Center, in 2022-2023. The study aimed to assess the applicability of three PCR tests proposed in international protocols for diagnosing the bacterial canker in tomato. The objectives included determining the key performance criteria of primer systems: analytical sensitivity and specificity, selectivity, reproducibility, and repeatability. Domestic reagents were used in the study, which helped reduce costs and increase the accessibility of diagnostics. According to the protocols by Sudarshana et al. and Bach et al. the PCR tests demonstrated high analytical sensitivity of of 10³ CFU/mL, while according to the protocol by Oosterhof and Berendsen sensitivity was 10⁴ CFU/mL. All primer systems demonstrated 100% specificity, with no cross-reactions observed with other strains. No selectivity was detected. The repeatability and reproducibility of all tests reached 100% at the sensitivity threshold level. Based on the assessment of the three primer systems, the PCR method described by Sudarshana et al. was selected as a screening tool for detecting bacterial tomato canker in analytical samples from seeds and vegetative parts of the plant. The remaining PCR tests are recommended as confirmatory assays.

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