Cytogenetic relationships among some palearctic and nearctic tetraploid taxa of the Campanula rotundifolia L. group

The cytogenetic interrelationships between tetraploid representatives of Campanula rotundifolia L. group were investigated. The F1 hybrids derived from the crosses between plants of European and American origin were fully fertile, however, some symptoms of hybrid sterility in F2s and Bs were noted. In the F1 the course of meiosis was normal. In some B segregants the disturbances in synchronization of meiotic divisions were observed. Although in most respect the F1 hybrids were intermediate between their parental forms, in some characters, like the shape of the corolla, the colour of pollen grains and the unrepeating flowering, they resembled more their American parents. No essential genetic barriers between tetraploid representatives of the C. rotundifolia L. group from Europe and North America were found. In view of the present data Guinochet’s hypothesis of the independent origin of European and American tetraploids is rather questionable