Studies on the breeding systems of O. appendiculatum and O. banksii subsp. banksii were carried out at Viçosa, Minas Gerais State, southeastern Brazil. Both species are self-compatible and seeds that resulted from self- and cross-pol linatio'ns presented a high viability. The low rate of fruit set in O. banksii subsp. banksii flowers exposed to visitors (open pollination) may be related to the lack of pollination (extrinsic factor). In O. appendiculatum the low rate of fruit set can be related to intrinsic factors, regulated by the plant itself. Interspecific pollinations resulted in viable seeds and the F1 hybrid presented 64% of fertile flowers; this hybrid has not yet been found under natural conditions. Self-pollinations in F1 flowers also yielded viable seeds.
Asclepiadaceae; compatibility; interspecific pollination; Oxypetalum