Improved Culture Methods for Rozella and for Olpidiopsis

SUMMARY

Slight modifications of Emerson's culture methods for the obligately parasitic chytrid Rozella allomycis produced dependable procedures for (i) maintenance of stock cultures of Rozella with its host, Allomyces arbuscula, on artificial medium, and (ii) harvest of pure, dense suspensions of Rozella zoospores. Such procedures were required for the initiation of an experimental study of this host-parasite system. The modifications were (i) extreme dilution of the nutrient content in the agar medium, and (ii) maintenance of a shallow layer of water on top of the agar. Under these conditions Allomyces produced no zoosporangia of its own, and its hyphae were filled with Rozella sporangia, which discharged their zoospores spontaneously into the liquid overlay; the latter could then be removed as a pure zoospore suspension from the host thalli which remained anchored in the agar. These procedures were further adapted for culturing Olpidiopsis varians with Achyla flagellata. Schedules for demonstrating these fungi in the teaching laboratory were also worked out.