Variability in response to UV-B among species and strains of Metarhizium isolated from sites at latitudes from 61° N to 54° S
Journal of Invertebrate Pathology
The effects of irradiances of 920 and 1200 mW m−2 (biologically effective weighted irradiance) were examined in 2 Metarhizium album strains, 26 M. anisopliae strains, 1 M. flavoviride strain, and 1 M. taii strain isolated from sites located at latitudes from 61°N to 54°S. Conidia were exposed to UV-B from 1 to 6 h and subsequently examined for relative percentage culturability. Total dosage received at the end of the exposure periods ranged from 3.3 to 19.9 kJ m−2 for the lower irradiance and from 4.3 to 25.9 kJ m−2 for the higher irradiance. Both the irradiance values and the doses are environmentally realistic and can be observed even in temperate regions. The relationships between latitude of origin and UV-B tolerance were compared for the two levels of irradiance for the data from 1 and 2 h exposure. Exposure to both irradiances drastically reduced the relative percentage culturability of all strains. Tolerance to UV-B varied widely among strains and high variation was observed for both irradiances after all periods of exposure. After 1 h of exposure, a difference between the two irradiance levels was detectable, and this difference was magnified at longer irradiations. A significant quadratic relationship of decreasing UV-B tolerance with increasing latitude was observed after exposure of 1 and 2 h. The shape of the relationship did not differ for the two levels of irradiance. Also, we studied the effect of 1200 mW m−2 irradiance on conidial germination time in 1 M. album strain, 7 M. anisopliae strains, and 1 M. taii strain. Exposure to UV-B delayed the germination of surviving conidia of all strains. In general, the delay in germination was directly proportional to the dose.
Braga, G.U.L., S.D. Flint, C.D. Miller, A.J. Anderson and D.W. Roberts. 2001. Variability in response to UV-B among species and strains of Metarhizium isolated from sites at latitudes from 61° N to 54° S. J. Invertebrate Pathology. 78: 98-108.