Detection and differentiation of Xanthomonas translucens pathovars translucens and undulosa from wheat and barley by duplex quantitative PCR

Two probe-based quantitative PCR (qPCR) systems, namely P-Xtt and P-Xtu, were developed for diagnosis of cereal bacterial leaf streak pathogens Xanthomonas translucens pv. translucens and pv. undulosa, respectively. P-Xtt is specific to pv. translucens. P-Xtu is specific to pv. undulosa, pv. cerealis, pv. secalis and pv. pistaciae. P-Xtt and P-Xtu worked on all accessible strains of pv. translucens and pv. undulosa, respectively. Both systems could detect 100 copies of the target gBlock DNA. The two systems could be used in both singleplex qPCR and duplex qPCR with similar efficiencies. On genomic DNA from strains of various X. translucens pathovars, both singleplex qPCR and duplex qPCR could specifically detect and differentiate pv. translucens and pv. undulosa. The duplex qPCR could detect pv. translucens and pv. undulosa from genomic DNA of 1,000 bacterial cells. On infected barley and wheat grain samples, and on one infected wheat leaf sample, the duplex qPCR showed similar efficiency compared to a previously published qPCR system but with the additional capability of pathovar differentiation. The duplex qPCR system developed in this study will be useful in studies on bacterial leaf streak and detection/differentiation of the pathogens.