Factors influencing the production of sclerotia in the wild rice (Zizania aquatica) pathogen Sclerotium hydrophilum

Abstract

Sclerotium hydrophilum was shown to be auxoheterotrophic for thiamine, with the addition of this vitamin being required for the induction of sclerotia on defined media, but riboflavin and pyridoxine also have a positive effect. In the absence of thiamine, an increase in glucose concentration lead to a decrease in the yield of sclerotia; however, the addition of thiamine negate this inhibition and, instead, as the glucose concentration increased a higher proportion of sclerotial initials matured. Overall it was found that thiamine, specifically the pyrimidine component of thiamine, is crucial for initiating sclerotium production, while glucose stimulates maturation. The effect of light on sclerotium production was found to be complex and dependent on the growth medium. Light is not required for either the induction or maturation of sclerotia, but continuous irradiation of developing cultures with either white light or black light induces an endogenous rhythm whereby sclerotia are formed every 48h. When exposed to alternating light/dark regimes mycelium that formed in the light does not mature sclerotia, but dark-formed mycelium does, even if it is subsequently exposed to light.