Pathovar-Specific PCR Method for Detection and Identification of pv. .

Bacterial leaf streak disease caused by pv. is an economically important disease threatening wheat and barley crops around the globe. Thus far, specific PCR-based detection and identification tests for pathovars are not available. In this study, we used comparative genomics approach to design a pathovar-specific primer pair for detection of pv. in naturally infected seeds and its differentiation from other pathovars of the species. For this aim, complete genome sequences of strains of different pathovars were compared and the specific PCR primer pair XtuF/XtuR was designed. These primers were strictly specific to pv. because the expected 229-bp DNA fragment was not amplified in the closely related pathovars or in other xanthomonads, wheat-pathogenic bacteria, and other plant-pathogenic bacteria. High sensitivity of the primer pair XtuF/XtuR allowed detection of pure DNA of the pathogen in a concentration as low as 4.5 pg/μl. The pathogen was also detected in water suspension at a concentration of 8.6 × 10 CFU/ml. The PCR test was capable of detecting the pathogen in extracts of naturally infected wheat seeds at a concentration of 3.5 × 10 CFU/g while a culture-plate method was able to detect the pathogen at a concentration of 50 × 10 CFU/g of the same seeds. The PCR test developed in this study is a step forward for precise detection and identification of pv. to prevent outbreaks of the bacterial leaf streak disease.