Variability in brown line formation and extracellular laccase production during interaction between white-rot basidiomycetes and Trichoderma harzianum biotype Th2

Abstract

Antagonisms between Trichoderma spp. and white-rot fungi are of interest for lignocellulose degradation and mushroom cultivation. Production of emergent hyphae, formation of pigmented barrages and production of laccases were followed and compared during confrontations between mycelia of two T. harzianum isolates with seven wood-rotting and seven leaf litter-rotting basidiomycetes. No specific defense pattern associated with each group of basidiomycete was identified but the number of species forming barrages with pigmented zones was higher in the group of wood decayers. Trichoderma harzianum induced increases in extracellular laccase activities only with some basidiomycete species. The two T. harzianum had been isolated as mushroom antagonists from two different media. Differences in their aggressiveness resulted in differences in the time given to the basidiomycetes for developing their resistance mechanisms. The biotype Th2 from white button mushroom compost was the stronger antagonist and could be a source of problems in solid state fermentations with different white rot basidiomycetes if it contaminates them.

Key Words:

• competition
• laccase
• litter fungi
• mushrooms
• wood fungi