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Six isolates of Erwinia carotovora were isolated from naturally infected potato tubers in different localities in Egypt. All isolates gave the same results in the pathological, morphological, physiological and biochemical tests and identified as E. carotovorasubsp. carotovora. The isolates showed variation in their virulence. The isolate ET was selected because this isolate was the nearest isolate to E. carotovora and also it was the most severe isolate on potato tubers. The effects of oxalic acid and biological control agents, Penicillium simplicissmum GP17-2, Pseudomonas putida T15, Pseudomonas vranovensi A30, Pseudomonas resinovorans A5 and Pseudomonas brassicacearum N32 on disease progress were evaluated. Oxalic acid at concentrations of 5, 10 and 20 mM and biological control agents significantly reduced soft rot development in wounded entire potato tubers cv. Kara as compared with the control. Disease development was significantly decreased by the tested treatments with increasing soaking time. Data obtained in this study showed that the tested concentrations of oxalic acid proved to be superior to biological control agents in reduction of soft rot disease except for GP 17-2 and T15 isolates. |
