Intraspecific hybridization of Trichoderma reesei QM 9414 by protoplast fusion using colour mutants

Abstract

Protoplasts were obtained from mycelia of two colour strains of Trichoderma reesei QM 9414 using a mycolytic enzyme system from Trichoderma viride BIA. Approximately 9–15% of the protoplasts obtained were regenerated on a solid culture medium with a soft agar overlay. When protoplasts from the two colour mutants were treated with an osmotically balanced solution containing 35% poly( ethylene glycol), they fused effectively. The production of well defined white and brown sectors on agar plates demonstrated that the fusants were heterokaryons. The heterokaryons produced cellulase, xylanase and β-glucosidase activities in amounts comparable to those of the parent colour strains or of strain QM 9414. Green conidia were induced from the heterokaryons after treatment with 0.1% d- camphor. This suggested the existence of a parasexual cycle in this species of Trichoderma and presented the possibility that diploidization had occurred.