Optimizing conditions for growth and sporulation of Pyrenophora semeniperda

The effects of photoperiod, light quality, wounding and sealing of culture plates on in vitro growth and sporulation of Pyrenophora semeniperda were examined to define conditions conducive to the abundant and rapid production of conidia. For maximum growth and sporulation, the leaf-spotting and seedborne plant pathogen required an alternating light/dark sequence. Fewer conidia were produced under conditions of constant illumination or constant darkness. Growth was enhanced by light of wavelengths longer than 500 nm, while sporulation was enhanced by light of wavelengths shorter than 500 nm. Sporulation was enhanced under conditions of alternating temperature with a diurnal photoperiod and by mycelial wounding. Sealing of Petri plates had an inhibitory effect on sporulation. Significantly more conidia of higher quality formed when unsealed cultures, wounded after 7 days, were exposed to 23degreesC during the light phase and 19degreesC during darkness. Under these optimal conditions, conidial numbers were increased by 800% or more compared with unwounded cultures grown at constant 25degreesC in 12 h alternating cool-white light.