Effect of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates of Phoma bakeriana

Summary The effects of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates (PB1, PB2, PB3) of Phoma bakeriana were investigated in vitro. There was no isolate effect on growth and pycnidium production but some evidence of a medium effect. Exceptionally high growth rate on two media corresponded with high pycnidium production; while low growth rates on other media were generally associated with high sporulation. There was a large temperature effect and an isolate effect on growth with a significant temperature by isolate interaction. Temperatures of 5°C, 10°C and 35°C inhibited pycnidium formation completely while the range 15–30°C had no effect on sporulation. Maximum growth and pycnidium production occurred at 25°C. Near‐ultraviolet radiation seemed to have caused higher pycnidium counts than the other light sources.