Light-dependent morphogenesis of conidia of Trichometasphaeria turcica in vitro
Induced changes in morphogenesis of developing and germinating conidia of Trichometasphaeria turcica Luttrell (Helminthosporium turcicum Passerini) exposed to various intensities and wavelengths of light were studied. A method to evaluate production of conidia on irradiated mycelium is described. Conidial production and germination were directly correlated with the quantity and quality of incident energy utilized. In white light highest conidial production occurred at an intensity of 23 000 ergs/cm2 s. Green light (515 nm) significantly further enhanced conidial production. Primary hyphae of conidia exposed to green light produced appressoria when germinated in white light. Hyphae of conidia exposed to orange light (640 nm) were branched or curled without appressoria. Only sensitivity to incident energy could account for the behaviour of T. turcica in vitro and by inference account for the pathogenic adaptation of this fungus in the reflected green light of the sweet-corn leaf surface.