Etiology Of Pear Blossom Blast And Associated Bacteria

China is the world's largest pear-producing country playing a pivotal role in the development of pear in the world. Pear blossom blast and bud blight occurred in two orchards of Zhejiang Province in the spring of 2006. The diseased pear branch showed no typical symptoms of "shepherd's-crook", which can be distinguished from fire blight. To determine the causal organism of pear blossom and bud blast in Zhejiang and differentiate it from other diseases of pear to carry out effective disease management. Sixteen samples of pear blossom blast and bud blight were collected, and six representative strains were identified as Pseudomonas syringae pv. syringae based on the colony morphology of initial bacteriological characteristics, Kock's postulate pathogenicity test, observation by electro-microscopy, Biolog identification, fatty acid methyl esters analysis(FAMEs),16S rDNA and ITS sequence analysis, besides, compared with the three P. syringae pv. syringae standard reference strains, one standard reference strain of tomato bacterial wilt. The data supported the fact that pear blossom blsat and bud blight in Hangzhou, China could be caused by P. syringae pv. syringae.Four representative bacterial strains were selected from strains isolated from leaf and twig dieback of pear plants companied with pear blossom and bud blast for determining the causal agent. They were identified as Bacillus sp. by physiological and biochemical properties, carbon source utilization profile, FAMEs and analysis of 16S rDNA gene sequence. Bacillus sp. was identified as the causal agent of leaf and twig dieback of Asian pear tree. To exploit the possible casual agents of disease symptom of running rusty water (RRW) from pear tree,3 representative strains isolated were identified based on the colony morphology characteristics, Kock's postulate test, Biolog, and FAMEs analysis,16S rDNA sequence analysis, and compared with the 2 strains of P. syringae pv. syringae,2 Dickeya chrysanthemi and 2 Xanthomonas axonopodis pv. poinsettiicola standard reference strains, respectively. D. chrysanthemi was proposed as potential pathogen causing RRW.