Selection of extranuclear mutants of Neurospora crassa

A procedure is described that produce primarily extranuclear mutants, of Neurospora carassa. An analysis of five mutants. [cni-3], [rsp-2], [rsp-3], E1RSP-4], IS PRESENTED. All five mutants segregate in an extranuclear manner. They can be assorted into two classes based on their respiratory properties: (1) those with cyanide-insensitive respiration (cni); (2) those with slow respiration (rsp). All of the mutants are female sterile. The respiratory trait can be placed in different nuclear backgrounds by heterokarytoic transfer. The abnormal respiratory traits are observed in mitochondria isloated from the mutants and it is likely that the mutations are in mitochondrial DNA.