Abstract
The protoplast fusion of Mucor pusillus and M. miehei was studied to develop a breeding system for the microbial rennin-producing Mucorales fungi. High yeilds of protoplasts from young germlings of these fungi were obtained by using an enzyme system containing Streptomyces No. 6 chitosanase, a commercial chitinase and sulfatase. Approximately 1 - 10% of these protoplasts regenerated on a solid medium with a soft agar overlay. Intraspecific hybridization between M. pusillus strains, as well as interspecific hybridization between M. pusillus and M. miehei was brought about by protoplast fusion, in the presence of polyethylene glycol in rather high frequencies (5-40%). Several hybrid strains between (+) and (-) strains of M. pusillus showed stable homothallic properties.
