Zoospores & Types of Plasmodiophorid Infections

How the two phases (sporogenic=secondary vs . sporangial=primary) in plasmodiophorid life cycles are linked together, and what factors determine whether an infection follows sporangial or sporogenic development deserve further research. It is generally accepted that the primary zoospores released during germination of resting spores initiate sporangial development. Under what conditions, however, could primary zoospores initiate sporogenic infections?

For some plasmodiophorids, secondary zoospores may continue to initiate sporangial infections until specific conditions cause sporogenic development. What are the conditions required for secondary zoospores to initiate sporogenic development?

Regardless of the problems associated with how each phase of the life cycle is initiated by a given type of zoospore, the method of infection of host cells by plasmodiophorid zoospores is unique. Williams (1973) provided an excellent summary of the process in which the contents of an encysted zoospore are injected through host cell wall and plasma membrane into the host cell cytoplasm.

Selected References for the Infection Process and Types of Infections

• Aist, J. R. & P. H. Williams. 1971. The cytology and kinetics of cabbage root hair penetration by Plasmodiophora brassicae Wor. Can. J. Bot. 49: 2023-2034.
• Diriwächter, G. & D. G. Parbery. 1991. Infection of potato by Spongospora subterranea . Mycol. Res. 95: 762-764.
• Dobson, R., L. & R. L. Gabrielson. 1983. Role of primary and secondary zoospores of Plasmodiophora brassicae in the development of clubroot in Chinese cabbage. Phytopathology 73: 559-561.
• Dylewski, D. P. 1987. Woronina pythii . In: Fuller, M. S. & A. Jaworski (eds.), Zoosporic Fungi in Teaching & Research. Southeastern Publishing Corporation, Athens, GA. Pg. 108-109.
• Keskin, B. & W. H. Fuchs. 1969. Der Infectionsvorgang bei Polymyxa betae . Arch. Mikrobiol. 68: 218-226.
• Kole, A. P. & A. J. Gielink. 1963. The significance of the zoosporangial stage in the life cycle of the Plasmodiophorales. Neth. J. Plant Path. 69: 258-262.
• Mithen, R. & R. Magrath. 1992. A contributioon to the life history of Plasmodiophora brassicae : secondary plasmodia development in root galls of Arabidopsis thaliana . Mycol. Res. 96: 877-885.
• Williams, P. H. 1973. Penetration and infection of cabbage roots by Plasmodiophora brassicae . Shokubutsu Byogai Kenkyu (Forsch. Gebiet Pflanzenkrankh.), Kyoto 8: 133-146.