Archivio Journal of Plant Pathology

Abstract:

In October 2013, a blight condition was observed on the fruiting bodies of Pleurotus eryngii in Beijing (China). Symptoms began as yellow spots on the stipe surface near the pilei, fruiting bodies became blighted and their growth stopped. Pieces from the inside of diseased fruiting bodies were excised, placed in 0.85% NaCl and the suspension was spread on trypticase soy agar (TSA) plates that were incubated at 30°C. Round yellow cultures were obtained, made up of bacterial cells 2.0-3.0×1.0 μm in size. The 16S rRNA and the atpD, gyrB, infB, rpoB genes of four isolates were amplified and sequenced (GenBank accession Nos. KJ654341-KJ654345). Although neighbour-joining tree constructed with 16S rRNA sequences and a multilocus sequence analysis (MLSA) showed that these isolates had the highest similarity with Pantoea agglomerans JCM 1236T (99.8% and 99.3%, respectively) the results of biochemical properties based on API 20E, 20NE, ZYM (bioMérieux) and GN2 MicroPlate (Biolog) disclosed 18 differences with P. agglomerans JCM 1236T. Bacterial suspensions in PBS (pH 7.0) ca. 1×106 CFU/ml were sprayed onto the surfaces of healthy fruiting bodies which 5-10 days post inoculation reacted with symptoms similar to those observed in the naturally infected samples, while the negative control sprayed with sterile PBS remained symptomless. Koch’s postulates were fulfilled by re-isolating a bacterium identical to that used for inoculation based on biochemical properties, 16S rRNA gene and MLSA. P. agglomerans was reported as the causal agent of blight disease of several hosts in many countries (Lee et al., 2010; Kim et al., 2015). To the best of our knowledge, this is the first report of Pantoea sp.-induced bacterial blight of P. eryngii in China.