In answer to your question, yeast has a plethora of dsRNA viruses which are
cytoplasmically inherited, but are not naturally infectious or plaquing agents.
These have been extensively reviewed by several authors, with R. B. Wickner
reviewing them at least every other year for the past several years. See the
Cold Spring Harbor Yeast Books or Annual Reviews. Although the "killer virus"
systems have been most extensively studied, there are others.
The yeast Ty elements similarly can be viewed as non-infectious retroelements
closely resembling retroviruses in their life cycles.
Recent articles in Science by Wickner also discuss the [URE3-1] and [PSI] (also
see Sue Liebman's work on the latter), cytoplasmically inherited elements of
yeast which have prion-like properties (other than infectivity).
Let me know if you need any further intro. to the wonderful world of yeast
UMDNJ-Robert Wood Johnson Medical School