Influence of temperature and water activity on the antagonism of Trichoderma harzianum to Verticillium and Rhizoctonia

This paper reports the in vitro antagonism of an isolate of Trichoderma harzianum under a range of water (0.85–0.995 aw) and temperature (15–25 °C) regimes when associated with two phytopathogenic fungi: Rhizoctonia solani and Verticillium dahliae. The effects of ecophysiologic factors on the individual and dual growth of these fungal species were investigated and the index of dominance (ID) of each fungus was analysed according to its interaction. Growth rate of all the fungi tested increased as water availability in the medium increased and had the fastest growth rate at highest aw levels (0.995). Growth also varied with temperature and decreased as temperature dropped from 25 to 15 °C. T. harzianum grew faster at 15 and 25 °C than R. solani and V. dahliae at aw levels of 0.98 and 0.995 when the fungi were grown together. In addition, T. harzianum inhibited the development of R. solani and V. dahliae upon contact (ID of 4) at both temperatures when aw was between 0.95 and 0.995. The results obtained show that the T. harzianum strain was antagonistic in vitro to R. solani and V. dahliae, and may be considered a potential biocontrol agent.