Cross compatibility of Petunia cultivars and P. axillaris with native taxa of Petunia in relation to their chromosome number

To obtain information about the breeding of garden petunias for future reference, we crossed six cultivars of petunias and their historical seed parent (Petunia axillaris subsp. axillaris) with 41 native taxa of Petunia sensu Jussien. The existence of two groups of the native taxa differing in their chromosome numbers (2n = 14 and 18) was confirmed. Petunia cultivaris (2n = 14) and P. axillaris subsp. axillaris (2n = 14) failed to set capsules when crossed with the taxa having a chromosome number of 2n - 18. In contrast, hybridizations were possible when they were crossed with taxa of 2n - 14, except for P. integrifolia subsp. occidentalis.