INTERACTIONS BETWEEN FUSARIUM-CULMORUM AND ITS POTENTIAL BIOCONTROL AGENT, TRICHODERMA-HARZIANUM, IN A PACKED-BED, CONTINUOUS-FLOW COLUMN REACTOR

The interaction between the filamentous fungi Fusarium culmorum and Tr ichoderma harzianum was studied. A continuous-flow column reactor anal ogous to a soil column was used to provide a unidirectional flow of nu trients and solid support particles to which the fungi could attach. S uch a system gave rise to a heterogeneous distribution of microorganis ms and concentration gradients, and thus exhibited the most significan t physical characteristics of the the soil. In columns inoculated with both fungal species, a succession in population dominance was observe d. F. culmorum was the dominant organism at the beginning of the exper iment; however, it was gradually replaced by T. harzianum. To analyze the results obtained from the dual culture columns, a mathematical mod el was developed. Three functions representing interaction between the two species were tested to determine which represented the experiment al results most accurately. The best qualitative fit was obtained with a model incorporating Monod kinetics and making logistic limitation o ff. culmorum a linear function of the population density of T. harzian um. The implication of combined experimental and mathematical evidence was that the interaction between the two species was not solely compe tition for a single resource; the population of T. harzianum had a dir ect effect on that off. culmorum. (C) 1997 Elsevier Science Inc.