PHYSIOLOGICAL AND BIOCHEMICAL-CHARACTERIZATION OF TRICHODERMA-HARZIANUM, A BIOLOGICAL-CONTROL AGENT AGAINST SOILBORN FUNGAL PLANT-PATHOGENS

Monoconidial cultures of 15 isolates of Trichoderma harzianum were cha racterized on the basis of 82 morphological, physiological, and bioche mical features and 99 isoenzyme bands from seven enzyme systems. The r esults were subjected to numerical analysis which revealed four distin ct groups. Representative sequences of the internal transcribed spacer 1 (ITS 1)-ITS 2 region in the ribosomal DNA gene cluster were compare d between groups confirming this distribution. The utility of the grou pings generated from the morphological, physiological, and biochemical data was assessed by including an additional environmental isolate in the electrophoretic analysis. The in vitro antibiotic activity of the T. harzianum isolates was assayed against 10 isolates of five differe nt soilborne fungal plant pathogens: Aphanomyces cochlioides, Rhizocto nia solani, Phoma betae, Acremonium cucurbitacearum, and Fusarium oxys porum f. sp. radicis lycopersici. Similarities between levels and spec ificities of biological activity and the numerical characterization gr oupings are both discussed in relation to antagonist-specific populati ons in known and potential biocontrol species.