Kappamyces, a new genus in the Chytridiales (Chytridiomycota)

A new genus for a chytrid member of the Rhizophydium clade is described. Many Rhizophydium clade members exhibit simple and variable thallus morphology, and thus some species may be identical, while others may be members of species complexes and represent distinct genera. A minute chytrid found colonizing pollen grains had zoospore ultrastructure and a sequence of the large subunit ribosomal rRNA gene different from the molecular constitution of 22 isolates in the core Rhizophydium clade. Unlike typical Rhizophydium zoospores, the zoospore of Kappamyces laurelensis gen. et sp. nov. lacked a rumposome, kinetosome-associated electron-opaque spur, and kinetosome-associated microtubular root. Distinct from the typical Rhizophydium zoospore, the kinetosome abutted a single mitochondrion, both the kinetosome and non-flagellated centriole had an electron-opaque core composed of dense material, and a ring of distinct vesicles surrounded the kinetosome. In a parsimony analysis of large subunit rRNA gene sequences, a grouping of K. laurelensis and two other isolates were sister to the core Rhizophydium clade, and both the K. laurelensis group and the core Rhizophydium clade had 100% boot-trap support. The zoospore of K. laurelensis may be the simplest type of zoospore in the Chytridiales.