Isolation, purification and characteristics of strains of Sclerotium rolfsii in Ghana

Abstract

The physiological and morphological characteristics of five strains of Sclerotium rolfsii identified by the phenomenon of aversion were studied. The appearance of the five strains of Sclerotium rolfsii on PDA plates was similar and mycelial dry weights in PDB after 6 day incubation varied statistically and the dry weight declined due to autolysis after 6 days differed according to the strains. Autolysis was moderate in strain SrXLL and extreme in strains SrEL1 and SrEL2. However, extensional growth on PDA was fastest in strains SrEL1 and SrEL2, moderate in strains SrXLL and SrXA1 and slowest in strains SrXA2. Strain SrXLL produced a mean number per Petri plate of 185 larger and heavier weight spherical, or ellipsoidal white sclerotia, which turned brown on maturing, whereas the remaining four strains formed 324 to 364 smaller and lighter weight sclerotia per Petri plate. Strain SrXLL with the smaller number of sclerotia had the heavier sclerotial weight and the greatest sclerotia diameter and volume, which was significantly different (P < 0.05) from those of the remaining four strains. A clear relationship was established between the number of sclerotia on one hand and the size and weight of sclerotia on the other hand. The larger sized sclerotia produce more emerging hyphae on germination than the smaller sized ones and the greater number of hyphae compensated the smaller number of sclerotia during establishment of strain SrXLL in the habitat