Survival of buried Sclerotinia sclerotiorum sclerotia in undisturbed soil

Abstract

Sclerotia of S. sclerotiorum are surviving structures and the most important source of inoculum in sunflower fields. There are few studies about sclerotia survival in uncultivated soil and in accordance to that our objective was to establish the effect of burial depth on sclerotia longevity and the ability of carpogenic germination. In the trial (2009-2011) sclerotia were buried at the depth of 5, 10 and 30 cm and recovered every year in June. In laboratory sclerotia survival and carpogenic germination were examined. Our results showed that a large percentage of sclerotia survive at least three years under suitable conditions of temperature and moisture. In the case of continuous flooding (2011) sclerotia placed shallow in the soil (5 cm) were completely destroyed. Achieved results suggest that in undesturbed soil sclerotia placed deeper in the soil (10 and 30 cm) stay alive longer than those in upper soil (5 cm). Regardless of the burial depth sclerotia were able to produce apothecia under laboratory conditions. Resident saprofitic soil fungi (Aspergillus sp., Fusarium sp., Mucor sp. and mycoparasitic Conyothirium sp.) have been isolated equally from alive and deceyed sclerotia, but still less from the viable one.