Observations on chytridiaceous parasites of phanerogams

Abstract

Resting spores of the chytrid parasite of Claytonia virginica or “Spring Beauty”, Physoderma claytonianum var. sparrowii, were overwintered in plastic containers buried at the site of collection near Ann Arbor, Mich., USA. Germination took place in the field in early March. The process was followed in the laboratory and involved dehiscence of an operculum, protrusion of an endosporangium, zoospore formation and discharge. Resting spore zoospores were repeatedly placed in contact with young Claytonia plants but there was no evidence that they ever developed into epibiotic, “ephemeral” sporangia. Rather, in all instances within 36 hours the endobiotic, polycentric thallus was established inside the host. Both observational evidence and the speed with which the endobiotic thallus first appeared pointed to the complete lack of an epibiotic stage in our material.