Abstract
The genetic feature of protoperithecium formation and the cause of its persistent variation in Neurospora crassa were investigated.
In the F1 progenies from reciprocal crossings between strains showing different ability of protoperithcium formation, most segregants showed the ability similar to the maternal parent.
The ability to form protoperithecia of a culture was generally transmitted to isolates obtained from single conidium, hyphal tip or hyphal segment. However, significant variations in the ability were observed depending on the kinds of cells isolated.
The ability of protoperithecium formation decreased during succesive transfers, and it was lost after several transfers.
The protoperithecium formation in the culture of heteroplasmic hyphae obtained by making anastomosis between two strains was more vigorous than either one of the parental strains.
From these results it was considered that a cytoplasmic factor is responsible for the protoperithecium formation, and the variation in the ability of protoperithecium formation among cultures from every sexual, asexual spores and hyphal segments may not only result from an irregular distribution of the cytoplasmic factors but also come from physiological abnormalities accompanied by cellular differentiation and aging, and regenerated by cellular meeting with other cytoplasm or nucleus.
