Storage of soilborne phytopathogenic fungi

Abstract

Preservation of soilborne phytopathogenic fungi for long periods of time is important so that researches can be followed up at any moment. Soilborne phytopathogenic fungi are organisms that can produce resistance structures in face of adverse situations, such as absence of hosts and unfavorable climatic conditions for their survi-val. The objective of this work was to develop preservation methodologies for resistance structures of the fungi Fusarium oxysporum f.sp. lycopersici race 2, Macrophomina phaseolina, Rhizoctonia solani AG4 HGI, Sclerotium rolfsii, Sclerotinia sclerotiorum, and Verti-cillium dahliae. The experiment was carried out in a randomized plots design and the method of resistance structures production was specific for each pathogen. Three treatments [room temperature (28±2ºC), of refrigerator (5ºC) and of freezer (-20ºC)] with two flasks (reps) each were assessed for each fungus. During the period of one year, survival and vigor of the pathogens were evaluated in a monthly basis. Pathogenicity tests were performed with the structures of resistance of each fungus that survived in the best treatment: a) F. oxys-porum f.sp. lycopersici at refrigerator and freezer temperatures (5.2 and 2.9 x 103 ufc.g-1 of talc, respectively); b) M. phaseolina at refrigerator temperature [100% of survival (S) and index 3 of vigor (V)] and S. rolfsii at room temperature (74.4% S and 1 V) and c) S. sclerotiorum and V. dahliae both at freezer temperature (100% S and 3 V). All, but V. dahliae resistance structure, remained pathogenic after one year of storage.