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This study evaluated the quaternary ammonium compound cetyl trimethyl ammonium bromide (CTAB) as an alternative to the chemically related dodecylguanidine (dodine) for the selective isolation of entomopathogenic fungi. Oatmeal agar (OA) with chloramphenicol was used as basal medium, and three concentrations of CTAB (0.5, 0.6, 0.7 g/L) were evaluated and compared against OA + 0.46 g/L dodine. Selective isolation and growth studies were performed with the entomopathogens Beauveria bassiana, Metarhizium anisopliae s.l. and Paecilomyces lilacinus and five common non-entomopathogenic non-target species. The three entomopathogenic fungi sporulated earlier on OA + 0.6 g/L CTAB than on OA + 0.46 g/L dodine, while none of the non-target fungi sporulated on OA + 0.6 g/L CTAB. All entomopathogenic fungal isolates grew on OA + 0.6 g/L CTAB, despite some intra-species variation, whereas non-target fungi showed no growth or sporulation. OA + 0.6 g/L CTAB resulted in an efficient medium to isolate B. bassiana, M. anisopliae s. l. and P. lilacinus from soil samples. Results of our study suggest that OA + 0.6 g/L CTAB is a suitable, simple and inexpensive to prepare medium to replace OA + 0.46 g/L dodine for the selective isolation of these fungi.

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The influence of water activity (aw) on deoxynivalenol accumulation in wheat at 25°C was studied. Gnotobiotic grains were conditioned at different aw levels, inoculated with a toxigenic Fusarium graminearum strain, and incubated for ten weeks. The highest accumulation of deoxynivalenol (1130 ug/kg) was detected at aw 0.980. At aw 0.945 and 0.925 the maximum quantities of toxin accumulated were 113 ug/kg and 93 ug/kg respectively. Deoxynivalenol was not detected in the substrate at aw 0.900. Results suggest that intermediate aw levels (0.97 - 0.92) are particularly critical at post harvest time because those are conditions under which deoxynivalenol production is most likely to be initiated naturally.

Aspergillus fuscicans, a new species within Aspergillus section Usti from Argentinean semi-arid soil is introduced. Molecular, morphological and physiological studies were conducted, based on sequence analysis of partial β-tubulin and calmodulin sequence data. Aspergillus fuscicans formed a distinct, well-defined clade related to A. calidoustus and A. pseudodeflectus. In addition, A. fuscicans was able to grow and sporulate at 37 ºC, and had a negative Ehrlich reaction. Morphological and physiological features could be used to differentiate the new species from its phylogenetically related taxa.