Phenotypic and Genotypic Characteristics of Erwinia amylovora Isolates from Different Hosts in Shiraz City



During 2007 – 2008 different fruit gardens in Shiraz (Fars Province, Iran) were surveyed for samples being collected from infected apple, pear and quince trees. Symptoms of the infected trees included water soaking of infected tissue, wilt and tissue necrosis, scorched and blackend of blossom bracts or young shoots. A total of 47 strains were isolated from infected trees using NA medium. On the basis of standard physiological, biochemical and nutritional tests the isolates were identified as Erwinia amylovora. The isolates were compared through physiological and biochemical characters, pathogenicity test, polymerase chain reaction (PCR) and rep-PCR. The isolates were gram and oxidase negative, catalase positive and facultative anaerobs with shiny smooth cream colonies on NA and translucent, smooth, large, light blue with entire margin colonies on CCT medium. All isolates induced hypersensitive reaction on tobacco, produced levan and acetoin and reduced substances from sucrose but were negative in induced potato soft rot and fluorescent pigment production on KB medium, pink pigment on YDC medium, reduction of nitrate, growth at 39?C and urease. Wound inoculation of bacterial suspension into apple pear and quince seedlings led to the slight formation of wilting, necrosis and chlorosis as well as necrosis of leaves and shephered crook at the tip, after a passage of three weeks. In PCR assay, 47 isolates identified as E. amylovora, produced predicted 1000bp with A/B specific primers. In rep-PCR assay, representative strains identified as E. amylovora, produced different fingerprints in weight with REP, ERIC and BOX primers. The results of this study demonstrated that E. amylovora strains isolated from different hosts in Shiraz Province are genotypically homogenous.