Identification of post-harvest rotting microorganisms from tomato fruits (Solanum esculentum Mill.) in Toke Kutaye District of West Shoa Zone, Ethiopia

Tomato (SolanumesculentumMill.) fruits were collected from farmers and retailers in Toke Kutaye District, Ethiopia during main-season (October to December, 2012) and off-season (December, 2012 to March, 2013) with an objective to identify microbial organisms that cause post-harvest rot of tomato. Diseased tissues were cultured in Potato Dextros Agar media for fungal and in Nutrient media for bacterial identification. Identification of isolated microbes were made based on cultural characteristics, microscopic examinations and biochemical test. A total of nine microorganisms comprising five bacteria and four fungi were isolated from the infected tomato fruits. The identified bacteria include:Erwinia carotovora, Clavibacter spp.,Xanthomonas campestris,Ralstonia solanacearumandPseudomonas aeruginosa. Among the isolated bacterial species, X. anthomonascampestris exhibited the highest frequency of occurrence (42.4%) followed byRalstoniasolanacearum (19.55%). Fungal pathogens such as Alternaria spp., Fusarium spp., Penicilium spp. and Rhizophus spp. were isolated from the infected tomato fruit samples. The average frequency of occurrence of Alternaria spp. was 37.5%, and Fusarium spp. and Rhizophus spp., had the frequency of occurrence of 25%. The pathogenicity test revealed that none of these pathogens could initiate the rot symptoms when inoculation was made on unwounded tomato fruits, indicate that these microorganisms fail to penetrate directly through the waxy skin of tomato. However, small wounds created during the post-harvest handling enabled them to infect fruit tissues. Hence, careful handling of the produce is important to minimize bruising and injury to the tissue and to further spread of the disease.