Behaviour of DNA-induced inositol-independent transformants of Neurospora crassa in sexual crosses.

Treatment of inositolless (inl) strains of Neurospora crassa with DNA from the wild type (allo-DNA) gives rise to inositol-independent (inl (+)) colonies. Some of these DNA-induced inl (+) strains (transformants) are sterile in sexual crosses on minimal medium that selects for the maintaining of the inl (+) character. The same inl (+) transformants, when crossed with an inl standard strain, are fertile on complete (inositol-containing) medium. There are, however, an increased number of unusual non-Mendelian tetrads (24%) among the progeny. The inl (+) and inl progeny from these complete non-Mendelian tetrads were further examined for the inheritance of the inl (+) trait. Several inl (+) progeny of these tetrads segregate inl conidia if growing on inositol-containing medium. The number of inl (+) conidia in certain inl (+) cultures decreases quickly under non-selective conditions. In transformants carrying mutant markers in linkage groups III, IV and VI non-Mendelian segregation of these traits can also be detected.The mechanism of the development of sterility and of the aberrant segregation is discussed.