The monitoring of causal agent of cotton bacterial blight and investigation of epiphytic gram negative bacteria on cotton seeds

Phylosphere is a site for living micro-organisms including bacteria. Plants species and plant leaf type have important role on diversity and density of bacteria live on them. There are several bacteria as epiphytic on aerial parts of plants and plant seeds which cause diseases in suitable conditions. Cotton bacterial blight has been appeared as epidemic in Iran particularly in Golestan province in recent years. Some suggestion propounds the presence of this bacterium on cotton seed surface. This study was conducted in Golestan province to identify the gram negative bacteria on seed surface. For this purpose, samplings were done randomly from cotton cultivar seeds Sahel, Varamin, Bakhtegan, Sepid and Khordad for planting. The seeds were incorporated into sterile distilled water and small amount of tween 20 as a detergent was added to it, and put to room temperature for one hour for better washing of bacteria on seed surface. Then the above suspension was streaked on bacterial culture media. The bacteria were isolated, purified and identified. The results revealed that Pseudomonas fluorescens, P. syringae, Pantoea annanas and Pectobacterium sp. were identified based on authentic references. The presence of Xanthomonas citri subsp. Malvacearum was not proved as causal agent of bacterial blight as epiphyte on cotton seeds.