6.3.3  Attempts at interspecies hybridization between Cephalosporium
           acremonium and Emericellopsis minima

The genus Emericellopsis was established by van Beyma in 1940 and is recognised as the perfect state of Cephalosporium (Acremonium; Gams, 1971). Although several species of Emericellopsis were examined (Table 6.3) only in one case could the sexual stage be demonstrated. E. minima produced an abundance of cleistothecia on CMA, CM and MM (Fig. 6.2) whereas the other species could not be induced to form cleistothecia on any of these media. Either they had lost this ability through subculture and storage or the conditions employed were not stringent enough. The inability to demonstrate a perfect stage could raise some doubts about the authenticity of these cultures. Therefore, E. minima was used in the subsequent hybridization experiments.

Several auxotrophs were obtained from ascospores of E. minima following UV treatment and it was noted that nonleaky mutants had apparently lost the ability to produce cleistothecia. Protoplasts were readily isolated from these strains but attempts to produce interspecific hybrids or heterokaryons with nutritionally complementary strains of C. acremonium after protoplast fusion proved unsuccessful. Selection was carried out on hypertonic minimal medium (SMS) and two auxotrophic markers were present in each strain to avoid confusion between potential inter-specific hybrids and back mutants.

References

van Beyma Thoe Kingma, F. H. (1940). Beschreibung einiger neuer Pilzarten aus dem Centraalbureau voor Schimmelcultures, Baarn (Nederland), V. I. Mitteilung. Antonie van Leeuwenhoek, 6, 263-290.

Gams, W. (1971). Cephalosporium-artige Schimmelpilze (Hyphomycetes). Gustav Fischer Verlag, Stuttgart, Germany.

TABLE 6.3  Species of Emericellopsis used in this study