Effect of water potential on sclerotial germination and mycelial growth of Macrophomina phaseolina

The effect of the osmotic (Ψs) and matric (Ψm) potential on the sclerotial germination and mycelial growth of Macrophomina phaseolina was examined at room temperature. Sclerotial germination was determined in 0.1% water agar and mycelial growth on potato dextrose agar (PDA) and potato dextrose broth (PDB) amended with sodium chloride and polyethylene glycol (PEG 6000). Treatments consisted of 6 levels of osmotic and matric potentials (0, -0.3, -0.6, -0.9, -1.2, and -1.5 MPa) arranged in a factorial manner in a completely randomized design. Decreasing the matric and the osmotic potentials to -1.2 and -0.6 MPa, respectively, increased sclerotial germination and mycelial growth, but any further decrease caused both sclerotial germination and mycelial growth to decline again. It was concluded that the matric potential was more important as a factor than the osmotic potential in promoting the vegetative growth of M. phaseolina.