Conidia survival of Aspergillus section Nigri, Flavi and Circumdati under UV-A and UV-B radiation with cycling temperature/light regime
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Bio-geographical differences in fungal infection distribution have been observed around the world, confirming that the climatic conditions are decisive in colonization. This research is focused on the impact of ultraviolet radiation (UV) on Aspergillus species, based on the consideration that an increase
in UV-B radiation may have large ecological effects. Conidia of six mycotoxigenic Aspergillus species isolated from vineyards located in the Northeast and South of Spain were incubated for 15 days under light/dark cycles and temperatures between 20 to 30 °C per day. Additionally, six hours of exposure to UV-A or UV-B radiation per day were included in the light exposure. UV irradiance used were 1.7 ± 0.2 mW·cm(-2) of UV-A (peak 365 nm) and 0.10 ± 0.2 mW·cm(-2) of UV-B (peak 312 nm). The intrinsic decrease of viability of conidia along time was accentuated when they were UV irradiated. UV-B radiation was more harmful. Conidial sensitivity to UV light was marked in A. section Circumdati. Conidia pigmentation could be related to UV sensitivity. Different resistance was observed within species belonging to sections Flavi and Nigri. An increase in UV radiation could lead to a reduction in the Aspergillus spp. inoculum present in field (vineyards, nuts, cereal crops). In addition, it could unbalance the spore species present in field leading to a higher predominance of dark pigmented conidia.