Germinability of Cochliobolus sativus Conidia Exposed to Solar Radiation

Under field conditions, conidia of Cochliobolus sativus, the causal agent of barley spot blotch, were exposed to direct solar radiation or placed in a ventilated enclosure in darkness for 0.5–12 h. In addition, conidia were either exposed or not exposed to UV light (254 nm) from 1 to 75 min in the laboratory. Conidia were placed after exposure on water agar in closed Petri dishes and allowed to germinate for 24 h. Germinability of conidia was reduced up to 99% after 12 h of exposure to solar irradiance (GS) (690–900 w/m2). Germinability of conidia that were not exposed to sunlight (GNS) did not decrease significantly during experiment time. Similar results were obtained when the variable (GNS)GS)/GNS was applied. Temperature accounted for limited variation in germinability, whereas solar radiation accounted for most of the variation. Germinability of conidia in the laboratory was reduced up to approximately 100% by doses of UV-C of approximately 14.4 kJ/m2. Germinability of conidia in the field was reduced up to approximately 100% by doses of UV-B of approximately 39.9 kJ/m2. The information obtained from this study will contribute to the development of a forecast system that incorporates the probability of incoming aerial spores.