The Plasmodiophoromycete parasitic on Heteranthera dubia

Abstract

Light and transmission electron microscopy were used to characterize representative stages of sporogenic plasmodia and resting spores of the plasmodiophorid parasite in roots of Heteranthera dubia (Jacq.) MacM. (water-stargrass). Cruciform nuclear divisions occurred in young plasmodia and noncruciform divisions occurred in more mature, transitional plasmodia. Prophase nuclei in transitional plasmodia contained synaptonemal complexes; noncruciform divisions were interpreted, therefore, as meiosis. Host–parasite interfaces were single unit membranes. Centrioles were paired end-to-end in plasmodia, but unpaired, single centrioles were in resting spores. Resting spores also contained crystalline bodies. Sporosori were disklike, consisted predominantly of single layers of resting spores, and were located at the periphery of host cells. Membranosorus heterantherae Ostenfeld and Peterson was considered the appropriate genus–species for the parasite, not Sorodiscus heterantherae Wernham.