جداسازی و بررسی ویژگی‌های فنوتیپی جدایه‌های باکتری‌ مولد پوسیدگی نرم سیب‌زمینی در دوران پس از برداشت

Potato soft rot is one of the diseases that causes damage both in the field and later during storage. The present study was conducted in order to isolate and identify bacteria causing potato soft rot in post-harvest period. First, a potato warehouse (Damaneh warehouse in Fereidan city) and grocery stores in Isfahan were visited. Samples with soft rot symptoms were collected and transferred to the laboratory. Isolation and purification of bacterial isolates were done according to usual methods. The pathogenicity test of all isolates was performed on potato tuber slices and whole tubers. Finally, 13 isolates were confirmed as the causal agents of potato soft rot and were subjected to different phenotypic tests. The isolates were gram negative, facultative anaerobic and catalase positive. Their reaction in the tests of starch hydrolysis, growth at 40°C and tolerance of 7% NaCl was positive. All isolates were negative for the indole test. They didn’t produce fluorescent pigment on King B medium. They were able to utilize citrate, glucose, maltose, raffinose and lactose. The reaction of isolates in the tests of oxidase, gelatin hydrolysis, utilization of inositol, dolcitol, arabitol and sorbitol and hypersensitive reaction was variable. The most of isolates were oxidase negative and showed hypersensitive reaction by inoculation on geranium. Based on the investigated phenotypic characteristics, the isolates were identified as Pectobacterium. The 16s rDNA were sequenced in two representative isolates and a Blast search was performed on GenBank for each sequence. The sequence similarity of both isolates to P. carotovorum was higher than 97%.