Effet de la température et de l'activité d'eau sur la germination et la croissance de 3 agents fongiques de lutte biologique contre la jacinthe d'eau (Eichhornia crassipes)

The fungi were grown in vitro on plates containing potato dextrose agar medium at different aw values (glycerol being added to adjust the aw). The percentage of viable conidia and radial growth rate decreased with decreasing water activity. Statistical analysis showed a significant effect of aw, temperature and the aw temperature interaction on mycelial growth (P < 0Æ0001). Water activity emerged as the factor exerting the greatest influence. Differences were observed between the fungi tested, the C. malorum appearing more tolerant to low aw and the F. sacchari more tolerant to high temperature (35 C). Growth models predicting the combined effect of aw and temperature were developed and response surfaces generated, showing fairly good agreement with the experimental values. Conclusions: Our results confirm the previous finding that aw has a greater influence than temperature on fungal growth. Under most conditions, variation of environmental factors has a detrimental influence on the percentage of viable conidia and mycelial growth rate of fungal isolates