Aislamiento de cepas de Aspergillus sección Nigri en la yerba mate comercializada en Posadas (Misiones, Argentina) y evaluación de su potencial ocratoxigénico / [Isolation of Aspergillus section Nigri strains in yerba mate in Posadas (Misiones, Argentina) and evaluation of their ochratoxigenic potential].

The objectives of the present work were to investigate the isolation frequency of genus Aspergillus in canchada yerba mate (YMCH) and elaborated yerba mate (YME) (Ilex paraguariensis) and the proportion of section Nigri isolates, as well as to determine ochratoxin A production by Aspergillus species section Nigri. Three hundred twenty eight Aspergillus strains from 20 samples of YMCH and 1306 Aspergillus strains from 36 samples of YME were isolated; of the total, 279 from the first group of strains and 1215 from the latter group, belonged to section Nigri. For the detection of ochratoxin A production, the strains were cultivated on Czapeck yeast extract agar and the toxin was detected by thin layer chromatography under UV light. Uniserate species predominance was observed in the 1494 strains of Aspergillus section Nigri obtained (Aspergillus japonicus var. japonicus and Aspergillus japonicus var. aculeatus), whereas none of the strains analysed showed ochratoxin A production in vitro at the detection level of the methodology employed.

Production of ochratoxin A by a strain of Aspergillus ochraceus on different seeds

A produçäo de ocratoxina A foi estudada usando-se sementes selecionadas como substrato nutritivo estéril para Aspergillus ochraceus. A produçäo foi maior no girassol do que nas demais sementes examinadas. Dentre os três cultívares de sorgo testados, dois foram altamente resistentes ao ataque do fungo