-Isolation trials from potato tubers showing bacterial soft rot collected from Giza, Kalubia, Sharkia and
Gharbia governorates yielded 35 bacterial isolates. The isolated bacteria were purified and identified as Pectobacterium
sp., Bacillus spp. and Pseudomonas spp. The frequency of the isolated bacteria was not greatly differed in the four
governorates. 15 strains of the isolates proved to be Pectobacterium carotovorum subsp. carotovorum. The
identification of the 15 isolates was confirmed by the Biolog system based on their sugar contents. Electron
micrographs of the nine isolates of P.carotovorum bacteriophages were taken. Of the fifteen isolates of P. carotovorum
(Pc) , only 4 isolates ,i.e. Pc2, Pc4, Pc7 and Pc10, were highly pathogenic to the five potato cultivars , i.e.. Belini , Cara, Hermes,
Mondial and Spunta . On the other hand, the tested isolates of Pc1, Pc3, Pc5, and Pc11 showed moderate effect on potato tubers.
Meanwhile, Pc9, Pc13 and Pc14 isolates had low effect on potato tubers and the other isolates, i.e. Pc6, Pc8, Pc12 and Pc15 failed to
cause any infection to four potato cvs. ,i.e.. Bilini, Cara , Hermes and Mondial, but infected cv. Spunta cv. Four isolates of the
bacteriophages (1, 2, 8 and 9) inhibited all the isolates of the causal bacterium . In addition, isolate (3) inhibited two
pathogenic isolates only (Pc7 and PC10). Meanwhile, the mixture of the nine isolates of the bacteriophage inhibited all
isolates of the causal bacterium. All the isolated phages were specific for P.carotovorum isolates and formed circular,
clear plaques with or without halo and ranged from 1.0 to 5.0 mm in diameter.
The tested 9 bacteriophages were effective in controlling bacterial soft rot on potato tubers comparing with the
control treatment. In addition, the mixture of these isolates was more efficient in decreasing the incidence and severity
of the disease as soft rot 2 and 4 days after the infestation with P. carotvorum isolates (Pc2, Pc4, Pc7and Pc10) than
the efficient of each of them alone. |
