Molecular biology of Trichoderma and biotechnological applications

Trichoderma spp. comprise common soil Hyphomycetes found in all climate zones ranging from Antarctica to the tropics (Domsch et al. 1980). Characteristic of the genus Trichoderma is the ability to effectively degrade a range of natural polymers, especially cellulose and hemicellulose, which also provides foundation for the commercial uses of Trichoderma. The taxonomy of the genus Trichoderma has been and still is under some dispute, however, the basis being on the work of Rifai (1969) assigning the Trichoderma strains to nine species aggregates differentiated primarily by patterns of conidiophore branching and conidium morphology. Recent studies have used DNA fingerprinting, restriction fragment length polymorphism and amplification, and ITS sequencing to further clarify the taxonomy of Trichoderma (revieved in Gams and Bissett 1998; Lieckfeldt et al. 1998). This analysis has revealed that the industrially most relevant species, Trichoderma reesei, is an anamorph of the species Hypocrea jecorina. A genetically well-defined lineage of strains originating from the isolate QM6a was classified as T. reesei and all current biotechnologically relevant strains are derivatives of QM6a (see Nevalainen et al. 1994), which is a unique situation.