T39butenolide and harzianopyridone production was
elicited in co-cultures with B. cinerea and R. solani. In
contrast, harzianolide, a reduced form of T39butenolide,
was not detected in the interactions between T. harzianum
strain T39 and pathogen biomasses, as previously
observed in plate confrontation assays with R. solani (Vinale
et al. 2006). Serrano-Carreo`n et al. (2004) found that
the production of 6-pentyl-a-pyrone (6PP) was stimulated
by the cultivation with nonviable pathogen mycelium,
but not in the co-culture condition. Therefore, they
suggested that 6PP production in T. harzianum is elicited
by R. solani as an antagonistic response determined by
the physiological status of the host.