EVALUATION OF RELATIONSHIP BETWEEN CHITINASE PRODUCTION AND BIOCONTROL CAPACITY OF TRICHODERMA ISOLATES

Twenty-four fungi were isolated from five plant hosts collected from 15 governorates. The mean percentage of fungal recovery from hosts showed that Trichoderma spp. (35.98%) were the most dominant fungi. The other fungi occurred at frequencies ranged from 0.07 to 17.67%. Occurrence of Trichoderma spp. was negatively correlated with incidence of five pathogenic fungi. However, the significant correlation was observed between isolation frequency of Trichoderma spp. and isolation frequency of Fusarium spp. (r= -0.57, p= 0.03). Fifteen isolates of Trichoderma spp. were screened for their biocontrol capacity against soil-borne fungal pathogens under greenhouse conditions by using eight pathosystems. These isolates showed various levels of antagonism within each pathosystem. When the same isolates were in-vitroscreened for chitinase activity, 20% of the isolates were high producers, 40% were medium producers, and 40% were low producers. Regression analysis was used to study the effect of chitinase activity (independent variable) on percentage of surviving seedlings (dependent variable) in each pathosystem. In most pathosystems, the in-vitro efficiency of Trichoderma isolates in producing chitinase was not significantly correlated with the percentage of surviving seedlings, which was used as a parameter for evaluating the antagonistic activity of Trichoderma isolates under greenhouse conditions. This finding may indicate that the in-vitro chitinase activity of Trichoderma isolates is of no practical value because it cannot be used as a criterion to predict their in-vivo performance. Grouping the isolates by cluster analysis, based on their biocontrol patterns, was not related to their chitinase activity. This result suggests that chitinase may not be involved in the biocontrol process of the tested isolates. Similarly, grouping the isolates by cluster analysis, based on their RAPD banding patterns, was not related to their chitinase activity. This result indicates that RAPD banding patterns were unable to differentiate among the isolates based on their chitinase activity.