OCCURRENCE OF PANTOEA BEIJINGENSIS ON PLEUROTUS ERYNGII IN CHINA

Abstract

In September 2012, water-soaked lesions and soft rot of stipes and pilei were observed in China on the fruiting bodies of Pleurotus eryngii, whose growth had halted. Four bacterial isolates with yellow, smooth and convex colonies, identical morphological characters and 16S rRNA, gyrB, rpoB, infB and atpD gene sequences were isolated from diseased tissues. Molecular phylogeny based on 16S rRNA sequence and MLSA data (combined gyrB, rpoB, infB and atpD) showed that the isolates had the highest similarity with Pantoea dispersa LMG 2603T. However, physiological and biochemical tests performed using API 20 E, API 50 CHB (bioMerieux) and GN2 Microplates (Biolog), and DNA-DNA hybridization (33.9±1.3% relatedness with P. dispersa LMG 2603T), differentiated the isolates from P. dispersa, identifiying them as Pantoea beijingensis (Liu et al., 2013). Based on the 16S rRNA gene sequence, a 98% similarity was found between P. beijingensis and Pantoea sp. PA4 reported as the agent of P. eryngii soft rot in Korea (Kim et al., 2007; Liu et al., 2013), suggesting that our isolates belonged to a species differing from Pantoea sp. PA4. Bacterial suspensions (approximately 1×106 CFU/ml) inoculated on the fruiting bodies induced within 5 to 7 days symptoms similar to those observed in natural infection. Controls remained healthy. Bacterial isolates recovered from typical lesions were identical to the inoculated strains in terms of 16S rRNA gene sequence, physiological and biochemical tests, performed using API 20 E, API 50 CHB (bioMerieux) and GN2 Microplates (Biolog), thus fulfilling Koch’s postulates. P. ananatis was first reported as a pathogen of P. eryngii in Korea (Kim et al., 2007), but to the best of our knowledge, this is the first report of P. beijingensis-induced soft rot disease of P. eryngii in China.