Abstract
Erwinia uzenensis is a plant-pathogenic bacterium, recently described in Japan, which infects pear trees, causing the ‘bacterial black shoot disease of European pear’ (BBSDP). Like other Erwinia pear pathogens, E. uzenensis causes damp, black lesions on young shoots resembling those of E. amylovora, but not blossom blight, fruitlet blight or wilting of the shoot tip. The distribution of E. uzenensis seems restricted to the country where it was reported up to now, but it may spread to other countries and affect new hosts, as is the current situation with E. piriflorinigrans and E. pyrifoliae. Fast and accurate detection systems for this new pathogen are needed to study its biology and to identify it on pear or other hosts. We report here the development of a specific and sensitive detection protocol based on a real-time PCR with a TaqMan probe for E. uzenensis, and its evaluation. In sensitivity assays, the detection threshold of this protocol was 101 cfu ml-1 on pure bacterial cultures and 102–103 cfu ml-1 on spiked plant material. The specificity of the protocol was evaluated against E. uzenensis and 46 strains of pear-associated Erwinia species different to E. uzenensis. No cross-reaction with the non-target bacterial species or the loss of sensitivity were observed. This specific and sensitive diagnostic tool may reveal a wider distribution and host range of E. uzenensis initially considered restricted to a region and will expand our knowledge of the life cycle and environmental preferences of this pathogen.
Highlights
Erwinia uzenensis is a Gram-negative bacterium, non-spore-forming, facultatively anaerobic, pathogenic on European pear (Pyrus communis), causing damp, black lesions on young shoots, which occasionally extend from the shoot through the petioles to the main vein of leaves [1]
Gel electrophoresis of the PCR products generated with primers FGPS6 and FGPL132’ on the three E. uzenensis strains revealed the presence of two bands of ca. 2000 bp and 2250 bp for all of them
The presence of two bands in the PCR reactions suggests that the three isolates possess multiple rRNA operons with intragenomic internal transcribed spacer (ITS) variation, which generally stems primarily from differences in transfer RNA genes (tRNAs) gene composition, as already observed in other Erwinia species [21]
Summary
Erwinia uzenensis is a Gram-negative bacterium, non-spore-forming, facultatively anaerobic, pathogenic on European pear (Pyrus communis), causing damp, black lesions on young shoots, which occasionally extend from the shoot through the petioles to the main vein of leaves [1]. The disease has been named ‘bacterial black shoot disease of European pear’ (BBSDP) and has been recorded only in Japan and only in pear trees [1, 2]. Real-time PCR for detection of the plant pathogen Erwinia uzenensis analysis, decision to publish, or preparation of the manuscript
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