High-frequency heterokaryon formation by Mucor racemosus.

Heterokaryons from Mucor racemosus were produced from two auxotrophic strains of the fungus. Germlings were converted to spheroplasts by using commercial chitinase and purified Myxobacter AL-1 chitosanase. Spheroplasts from the auxotrophic strains were mixed and fused in solutions of polyethylene glycol and CaCl2. Under optimal conditions, prototrophic heterokaryons were formed at a frequency of about 5%.