DNA Homologies Among Heterothallic Species of Neurospora

SUMMARY

Highly purified DNA from three reference strains representing authentic heterothallic species: Neurospora crassa, Neurospora intermedia and Neurospora sitophila, and from several unidentified Neurospora isolates was characterized by spectrophotometry, and by DNA:DNA reassociation using hydroxyapatite chromatography. These known heterothallic species and isolates were closely related on the basis of morphology, physiology and DNA characteristics such as base composition, thermal denaturation profiles and occurrence of repeated DNA sequences. They were, however, distinguishable by DNA:DNA homology studies. It was concluded that N. crassa is closer to N. intermedia than to N. sitophila. Neurospora sp. Gianjor, a 4-spored pseudohomothallic species, was significantly different from N. crassa and N. intermedia, but had greater homology with N. sitophila. All of the Neurospora isolates which crossed readily with N. crassa, and produced 95% black ascospores, were indistingushable from that species by DNA homology studies. It was possible to assign some of the unidentified isolates to species based on DNA homology studies.