ABSTRACT
Success in hybrid formation has been most readily achieved when the parental strains belong to closely related fungal taxa. Protoplast fusion techniques have been used to bypass many natural barriers to cross-breeding in fungi. Protoplast fusion has been reported in numerous species of Deuteromycetes where no sexual cycle exists. In Ascomycetes, where the sexual cycle is difficult or impossible to demonstrate, protoplast fusion has been successful in allowing genetic exchange. Parasexual recombination has been overshadowed by the development of protoplast fusion technology. Protoplast fusion is regarded as an effective technique to study the genetics and biochemistry of fungi and yeasts and for leading to new approaches in genetic manipulation. The introduction of polyethylene glycol (PEG) as powerful fusogenic agent in plant protoplast systems spurred the interest in use of PEG to induce fusion in other protoplast systems. PEG was first used in conjunction with protoplasts in 1953 when C. Weibull used a PEG solution to stabilize Bacillus megaterium protoplasts.
