Pear Blossom Blast Caused by Pseudomonas syringae pv. syringae in China

This study was done to determine the causal organism of the pear blossom and bud blast in China. It was identified by a bacteriological test, electro-microscopic observation, Koch's postulate test, Biolog, fatty acid methyl esters (FAMEs), and a polymerase chain reaction (PCR) test, and compared with the standard reference strains. Six representative strains out of 20 pathogenic bacterial isolates from 16 diseased samples showed characteristics similar to three standard strains of Pseudomonas syringae pv. syringae from Belgium. They were identified as P. syringae pv. syringae with a Biolog similarity of 0.57-0.86 and FAMEs similarity of 0.58-0.81. The bacterium was reisolated from the symptomatic plants and blossoms. Identification as P. syringae pv. syringae was confirmed by using PCR primers and sequence tests, and compared with the above-mentioned results. The data supported the fact that the pear blossom and bud blast in China could be caused by P. syringae pv. syringae.