The viability of sclerotia of Sclerotinia sclerotiorum was assessed for eight months in three cultivated Cerrado soils. Sclerotia produced in vitro were placed in nylon mesh bags and buried 5 cm deep in soils either previously treated or untreated with methyl bromide. After 10 days of incubation, sclerotia were retrieved and were examined for viability and presence of antagonistic fungi. Viability was assessed based on the number of sclerotia germinated after a 7-day incubation period on semi-selective Neon-S medium. Viability of the sclerotia varied among Cerrado soils. Sclerotia from soils not treated with methyl bromide were less viable and were often contaminated by antagonistic fungi, indicating the presence of suppressive elements of biological origin in the untreated Cerrado soils. Sclerotium viability was negatively related to the population of some soil microorganisms. Treatments with higher incidences of Trichoderma spp. also presented lower sclerotium viability, and fumigation strongly suppressed this antagonist.
Soil suppressiveness; Soil fumigation; Trichoderma; Gliocladium
