Bacterial shoot blight caused by Pseudomonas cerasi, a new pathogen of pear tree

In 2018, bacterial shoot blight was observed on Asian pear trees (Pyrus pyrifolia) in an orchard in Jinju, South Korea. The young pear shoots were infected and showed shoot blight symptoms: the shoot tips shriveled and turned tan in color, and this spread from the shoot tip down the stem and into the leaves. The causal pathogen was isolated from the diseased lesions and identified as Pseudomonas cerasi based on API tests and multilocus sequence analysis (MLSA) using the 16S rRNA, gyrB, rpoB, and rpoD gene sequences. The symptoms after artificial inoculation were identical to natural field symptoms, whereas negative control plants were asymptomatic. Bacteria were re-isolated from the artificially induced lesions on blossoms and shoots, and their identity was confirmed by rpoD sequencing. This is the first report of bacterial shoot blight on pear tree caused by Pseudomonas cerasi Griffin in the world.