EFFECT OF CULTURE CONDITIONS ON SPORE SHELF-LIFE OF THE BIOCONTROL AGENT TRICHODERMA-HARZIANUM

The influence of pH, carbon:nitrogen (C:N) ratio, carbon content and h arvesting time on spore attributes of the biocontrol agent Trichoderma harzianum was evaluated. The effect of these culture parameters on vi ability, shelf-life and ultrastucture was also assessed. pH was a key parameter to manipulate for both growth and sporulation, while carbon concentration and C:N ratio strongly affected spore production time. A t fixed pH, the C:N ratio had a limited influence on production yield, but was critical for spore shelf-life. The highest spore longevity wa s found in a medium with a C:N ratio of 14 and a pH of 7.0, when most resulting spores were still alive after 45 d storage. These spores als o remained viable during storage under a broad range of relative humid ities, indicating that they would be more sustainable in the field.