Influence of culture media in viability test of conidia of entomopathogenic fungi

Abstract

This work aimed at investigatimg whether the culture medium used in viability tests affects the conidial germination of Lecanicillium lecanii, Beauveria bassiana and Paecilomyces fumosoroseus isolates. The tests were performed on microscope slides containing one of the culture media: agar-water (AW), minimal medium (MM), potato-dextrose agar (PDA), potato-dextrose-1% yeast extract agar (PDAY), Sabouraud-dextrose-yeast extract agar (SDAY), and complete medium (CM). Three areas per slide were delimited and 0.05ml of a 5.5 x 105 conidia ml-1 suspension was applied to each area. One bioassay was performed for each isolate. Germination was determined after 15 hours of incubation at 26±0.5°C. The culture media influenced the germination of the species studied, verifying within and inter specific variations. CM and PDA provided the highest germination of L. lecanii isolates and the lowest was obtained on SDAY and AW. The germination of B. bassiana isolates was favoured by CM, PDA and PDAY media, a fact not observed in AW and MM. P. fumosoroseus isolates showed the highest germination on CM and PDA media and the lowest on SDAY. However, some isolates presented high germination on nutrient-poor media (AW and MM).