HOST RANGE STUDIES OF CERTAIN PHYCOMYCETES PARASITIC ON DESMIDS

Abstract

Cook, Philip W. (Indiana U., Bloomington.) Host range studies of certain phycomycetes parasitic on desmids. Amer. Jour. Bot. 50(6): 580–588. 1963.—Several aquatic phycomycetes, parasitic on desmids, have been isolated and maintained on hosts grown in unialgal culture. The parasites include representatives of Entophlyctis, Mitochytridium, Myzocytium, and Ancylistes. An extensive host range study was undertaken to evaluate host‐parasite interactions as an indication of taxonomic relationships of the hosts. The morphological aspects of the host were closely correlated with their susceptibility, as judged by the presence of appressoria or germinated zoospores of the parasites. General susceptibility of Closterium moniliferum and related taxa to several specific parasites supported the delimitation of the group on the basis of vegetative and sexual morphology. Resistance or susceptibility of clones within the Cl. acerosum‐Cl. praelongum complex was more closely associated with sexual morphology than with the vegetative characteristics which are currently used to separate species. The ability of some parasites to attack only certain clones of Cl. praelongum var. brevius was correlated with morphological differences between clones assigned to this variety. Susceptibility of Micrasterias to a strain of Myzocytium provided a basis for grouping species within the host genus. In some instances, the life cycle of the parasite was influenced by the host. The taxonomic significance of host range studies is discussed.