Abstract:
The in vitro biocontrol ability of Trichoderma harzianum on the phytopathogen
Alternaria alternata improved in the presence of the growth regulators gibberellic
acid (GA3), or indolacetic acid (IAA) or benzylaminopurine (BAP) or foliar nutrient at
concentrations similar or higher than those used at the field level. These plant hormones
decreased the secretion of endopolygalacturonase (endo-PG) of A. alternata by approximately
20%, did not modify endochitinase (endo-CH) secretion of T. harzianum and did not alter
germination of conidia or mycelia growth of any of these fungi. The presence of T. harzianum
decreased endo-PGase secretion of A. alternata by about 50%. This inhibitory effect was
independent of the presence of growth regulators. The level of secreted endo-PG of T.
harzianum was not modified by the presence of A. alternata, but the presence of this
phytopathogen in cultures of T. harzianum, increased both the growth of the biocontroller and
its secretion of endo-CH.
