ULTRASTRUCTURAL KARYOLOGY OF SPONGOSPORA-SUBTERRANEA (PLASMODIOPHOROMYCETES)

Sporogenic (cystogenous) stages of development of Spongospora subterranea (Wallroth) Lagerheim f.sp. subterranea Tomlinson infecting potato tubers were examined with transmission electron microscopy. Volume of nuclei in transitional plasmodia was 28.2 +/- 8.3-mu-m3. Serial section analysis revealed 37 synaptonemal complexes, hence the haploid chromosome number was considered to be 37. Total length of synaptonemal complexes per nucleus was 74.6 +/- 1.4-mu-m, with individual synaptonemal complexes ranging in length from 1.34 +/- 0.07-mu-m to 3.48 +/- 0.17-mu-m. No polycomplexes were observed in transitional nuclei. Electron-opaque thickenings of lateral elements occurred irregularly. Additional ultrastructural features of sporogenic plasmodia included end-to-end paired centrioles defining the poles of the nuclei and a host-parasite boundary of a single unit membrane.