Resurrection of Petunia occidentalis R. E. Fr. (Solanaceae) Inferred from a Cross Compatibility Study

In order to obtain additional taxonomic information about infraspecific taxa of Petunia integrifolia, we examined reciprocal cross compatibility between combinations of var. integrifolia, var. depauperata, subsp. inflata, subsp. occidentalis, as well as P. axillaris. Subsp. occidentalis completely failed to set capsule when it was used as the pollen parent. Similarly, the crossings in the opposite direction were rarely successful, and the number of hybrid plants obtained was limited. In contrast, all other taxa, including P. axillaris, could be crossed reciprocally with a higher rate of capsule set. The pollen fertility of the subsp. occidentalis hybrid was inferior to that of all the other hybrids. Based on the results of a previous study (Ando et al. 1995) and those of the present one, we treated subsp. occidentalis as an independent species herein.