Effect of Gibberellic Acid, Indole Acetic Acid and Ethylene Gas on The In vitro Biocontrol Activity of Trichoderma harzianumRefai Against Alternaria solani and Botrytis cinerea

ALTERNARIA solani and Botrytis cinerea were isolated from molds infecting tomato plant in Egypt. The biocontrol activity of Trichoderma harzianum Refai against these two pathogens were investigated in presence and in absence of growth regulators . The antagonistic activity of T. harzianum against these two pathogens were affected by the presence of growth regulators. IAA and GA3 alone or in combination was stimulator for Alternaria solani; however this stimulation was suppressed in dual culture with T. harzianum. Ethylene gas was stimulator for the growth of Botrytis cinerea, although this stimulation was hampered when the ethylene gas and T. harzianum were existing together. Although IAA and GA3 alone or in combinations stimulated Alternaria solani especially at low concentrations , it couldn’t affect the growth of T.harzianum .The hormones mycoparasitism relationship were monitored by endo- polygalacturonase , β-1, 3- glucanase, and Endo-chitinases enzymes . The secretion of endo- PG from A. solani was reduced when it was grown in the presence of IAA and GA3 when they were used separate or in mixture .The secretion of endo-PG from T. harzianum was increased as the hormones were also increased, but in the presence of the phytopathogens, the secretion was reduced.The activity of enzymes was increased at concentrations less than 40 ppm for both IAA and GA3 and at concentrations less than 75 ppm for ethylene .The hormones separately or in mixture couldn’t affect the secretion of Endo-chitinase (endo-CH) and β-1, 3- glucanase from T. harzianum directly but it act together with the phytopathogen. Ethylene gas was stimulator for Botrytis cinerea but it couldn't affect the growth of T.harzianum .