Protomyces Unger (1833)

Publisher Summary This chapter studies the genus Protomyces. In the determination of the asexual reproduction, it is seen that cell division is by budding on a narrow base near the poles of the cell. The cells are ovoid to elongate, and elongate cells may be asymmetrical. Pseudohyphae and true hyphae are not formed in culture. In sexual reproduction it is found that the ascosporic state is confined to the tissue of infected plants. Heavy walled spherical structures, variously termed ascogenous cells, synasci, and “chlamydospores,” are formed in infected tissue. The ascogenous cells germinate to form a vesicle (ascus) that in turn produces 50–200 spherical or ellipsoidal ascospores. Ascospore release is through a slit in the vesicle. Ascospores germinate to form asaprophytic, yeast-like budding stage. Reinfection of the host seems only to occur by hyphae, which results following conjugation of compatible yeast cells. Where examined, species are heterothallic. The chapter also discusses physiology/biochemistry and phylogenetic placement of the genus in which sugars are not fermented, nitrate is assimilated by most species, carotenoid pigments are usually produced by yeast phase cells in culture, and formation of extracellular starch-like compounds is strong, weak, or variable. The major ubiquinone is coenzyme Q-10 and the diazonium blue B reaction is negative. The type species taken is Protomyces macrosporus.