Attempts to detect extra genomial factors in cytoplasmic male-sterile petunia lines.

In the present study we examined the possibility that viruses, viroids or dsRNA are associated with cytoplasmic male sterile (cms) petunia. The assumption was made that if viruses or viroids were present, the treatments for elimination of viruses and viroids would produce "healthy" fertile plants. Male sterile plants were subjected to heat and cold treatments for 10 weeks and/ or for 5 months, after which apical meristems were isolated and cultured with the addition of antiviral factors. The mother plants, the regenerated plants and their progeny were sterile. These treatments did not affect sterility in sterile plants or the fertility of fertile plants. No dsRNA was found in cms petunia by gel electrophoresis. Thus, our data suggest that there are no viruses, viroids or dsRNA associated with cms petunia. Our data are in agreement with recent data, which suggests that the mitochondrial DNA is the site of the cytoplasmic male sterile gene in petunia.

The relationship between a nuclear restorer gene and the nuclear gene for male sterility in Petunia.

This paper describes the relationship between the restorer gene and the gene for male sterility in the background of normal cytoplasm. We combined these two traits by crosses in one plant, thus making genetic analysis possible. Two main conclusions can be drawn: 1. The restorer gene and the gene for male sterility are located at different loci which segregate independently one from the other. 2. The Rf allele does not affect the expression of the e allele.