Epidemiology of Potato Blackleg in Warm Climate
Abstract: Potato (Solanum tuberosum L.) planted in warm climate in September, in Egypt, showed no above ground symptoms of blackleg. The harvested crop showed severe tuber collapse similar to that being produced by the soft rot disease. Tentative identification of the isolated bacteria revealed no affiliation to the soft rot bacterium Erwinia carotovora ssp.carotovora. Verification of identity was made by PCR that showed its close similarity, to E. carotovora ssp. atroseptica at 119 bp, compared to an authentic Dutch isolate PD4202. The present study suggested that the quality of water phase in the field soil may play an important role in rot progress at the time of harvest. Tonicity, cation(s) content and pH of the water phase of soil, suspending the bacterial inoculums, were found important in this regard. The rot increased under hypertonic stress (10g-l NaCl) was attributed to a greater proliferation of bacteria on the expense of nutrients withdrawn from tuber cells. Further increase (20g-l NaCl) in tonicity, however, decreased tuber rot, indicating negative correlation between the aggressiveness of strain to potato tubers and their osmotic tolerance. Pathogen suspended in hypotonic solution produced greater rot possibly due to greater invasion by bacteria and/or maximization of the intercellular

spaces following cell turgidity. The monovalent and divalent cations at approximately similar osmotic strength decreased the rot symptoms. This effect may be attributed to their effect on a group of depolymerases with different optimal conditions and/or their effect on changing optimal Ph for pectinolysis. The tuber rot was recorded over a wide range of pH. Further investigations are needed to study in depth other edaphic factors related to epidemiology of blackleg disease in warm climate.
Publication year 2009
Pages 27-31
Organization Name
serial title Plant Pathology Journal
Author(s) from ARC
Publication Type Journal
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