Chrysanthemum (Dendranthema grandiflorum) is one of the important cut flowers and pot plants which belong to family Asteraceae. The aim of this study is to isolate and identify causal pathogens of Chrysanthemum bacterial blight disease, samples showing typical symptoms of bacterial blight disease on leaves, buds, stems or flowers obtained from different geographical areas of Egypt were used. The most conspicuous symptoms in infected leaves appear as water-soaked spots then become brown and dry. Ten bacterial isolates were isolated from different parts of Chrysanthemum which collected from different localities. In this respect, the bacterial isolates designated as Wl-1 and Wb-2 which were isolated from leaves and buds respectively of chrysanthemum white variety in Qualubia (Moshtohor). Meanwhile, the isolates coded as Ps-3 and Pf-4 were isolated from stems and flowers of chrysanthemum purple variety respectively in the same governorate (El-kanater El-khairia), the bacterial isolates coded as Ws-5 and Wf-6 were isolated from stems and flowers of chrysanthemum white variety planted in Menoufia governorate (Shebeen El-kom). While, the isolates coded as Yl-7 and Yb-8 were isolated from leaves and buds of chrysanthemum yellow variety respectively in Giza governorate (Kirdasah). The isolate Rs- 9 and Rf-10 were isolated from stems and flowers of chrysanthemum red variety from the same governorate (Elmariotia). Identification of isolated bacteria using the traditional techniques according to their inspected morphological, cultural characteristics, biochemical and physiological characteristics, these traditional tests revealed that these isolates may be belong to three genera i.e., Wl-1, Pf-4 and Rs-9 could be identified as Pseudomonas cichorii, while, the isolate Yb-8 could be identified as Pseudomonas fluorescens while the isolate Wf-6 was identified as Bacillus subtilis. The present study examined the level of genetic diversity and its molecular variation of the bacterial blight disease caused by Pseudomonas cichorii, three isolates from five geographic regions in Egypt. In addition, the isolates were pathogenic to eight plants from different plant families by artificial inoculations. This bacterium has a wide host range and this work is important for cataloging plant pathogenic bacteria that occur throughout special conditions may become epidemic in Egypt. |
