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.