Identification and Occurrence of Trichoderma harzianum Associated with Cork Oak in Tunisia

Trichoderma harzianum is an endophyte fungus of considerable interest because of its effectiveness as a biocontrol agent against various plant pathogenic fungi. In this study, T. harzianum was isolated from cork oak trees in three forests in northwest Tunisia. Initially, the fungal characterization was carried out based on macroscopic and microscopic features. Sequencing of the internal transcribed spacers 1 and 2 of the DNAr was carried out to confirm fungus identification at the species level. The aims of this work were to study the occurrence of T. harzianum, to understand its relationship with the host plant, and to quantitatively investigate its distribution on the different organs of cork oak trees across three sites (Babouch, Ain snoussi, Ain zana). T. harzianum frequency varied significantly (P inferieur 0.001) among the surveyed forests. The fungus was more common at Babouch forest and was rarely encountered at Ain zana. Correlation analysis was used to determine the relationship between the dendrometric parameters, the phytosanitary status of the investigated trees and the abundance of T. harzianum. The results showed a significant and positive correlation between the fungus frequency and the tree height. A negative and significant correlation was noted between the trees’ chlorosis index and fungus abundance. These findings may afford a contribution to the knowledge of T. harzianum in Tunisian forests and its relationship with cork oak trees which could help to develop control strategies using Trichoderma strains