Survival and germinability of Rhynchosporium secalis conidia exposed to solar radiation

Abstract Rhynchosporium secalis, the causal agent of barley scald disease, is a fungus commonly found in the environment. Disease spread within a field and between fields occurs through the aerial dispersal of the fungal spores. However, not much is known about the survival potential of fungal conidia exposed to solar radiation. In the present study, detached conidia of R. secalis were exposed simultaneously in the field to direct sunlight or placed in an adjacent ventilated enclosure in the dark for periods ranging from 0.5 to 8h. In addition, conidia were either exposed or not exposed to UV-C light (254 nm) for periods ranging between 0.5 and 60 min in the laboratory. After exposure, conidia were placed on water agar Petri dishes and allowed to germinate for 24h. Germinability of conidia was reduced by up to 94% after 8h of exposure to solar irradiance (670-860 Wm-2) in the field in comparison to the non-exposed control. Germinability of conidia in the laboratory was reduced up to ~100% by doses of UV-C light of 3.2±0.7 Wm-2. The results of this study will contribute to a better understanding of the relationship between climatic conditions and barley scald epidemics