Phylogenetic study of the bacterium causing orchid soft rot disease in Pakdasht region

Subject Areas : Plant Pests

Tayyibah Yousefieh ¹ , Abul Qasem Ghasemi ² , Ali Alizadeh Aliabadi ³

1 - Former MSc. Student, Department of Plant Pathology, College of Agriculture, Varamin-Pishva Branch,Islamic Azad University, Varamin, Iran.
2 - Assistant Professor Department of Plant Diseases, Iranian Research Institute of Plant Protection, Tehran, Iran.
3 - Associate Professor, Department of Plant Diseases, Iranian Research Institute of Plant Protection, Tehran, Iran.

Received: 2014-01-03 Accepted : 2014-05-15 Published : 2014-06-22

Keywords: PCR, sequencing, Orchid, Dickeya sp, soft rot,

Abstract :

Orchids which are considered as one of the most worthy plants, is affected mostly by soft rot disease. Samples of orchid plants that showed soft rot symptoms were collected frequently from greenhouses in Pakdasht region of Iran during the spring of 2013. The pathogenic agent was isolated from infected samples through culturing them on Eosin Methylene Blue Agar (EMBA) and Nutrient Agar (NA) media. Pathogenicity of isolates was tested and proved through inoculation on orchid leaves. Based on the results of phenotypic characteristics comparison (oxidative-fermentation, gram stain, facultative aerobic growth, indol production, nitrate reduction, Erythromycin sensitivity, and phosphatase activity) and other standard methods, the bacterial isolates were determined to be belonged to Dickeya sp. This determination was confirmed by pectate lyase gene amplified by ADE primer vs. EXPECC and Y1/Y2. Sequence analysis of the Recombinase A and RNA polymerase beta sub­unit genes showed the 99 to 100% similarity with deposited Dickeya sp. and distinct differences with other identified species existing in NCBI.