Effect of pollen source on germination of Vanilla planifolia, V. pompona (Orchidaceae), and their interspecific hybrids

Background: Vanilla planifolia and V. pompona exhibit low seed germination rates. Although their fruits are obtained through manual self-pollination, the effect of intra- and interspecific cross-pollination on their fruits and seeds remains unknown. Hybrids organisms are considered potential alternatives to traditional cultivation. Questions: How does cross-pollination affect germination in V. planifolia and V. pompona? Do hybrids seeds exhibit greater germination than their parental species? Studied species: Vanilla planifolia, V. pompona, V. planifolia × V. pompona, V. pompona × V. planifolia (Orchidaceae) Study site and dates: Mesa de Guadalupe, Alto Lucero, and La Concepción, Jilotepec, Veracruz, Mexico, in April 2024. Methods: Manual pollinations (self-pollination, geitonogamy, and metaxenia/xenia) were performed, and fruits from natural pollination were collected. Hybrids were only self-pollinated. Fruits and seeds were characterized, and seeds were planted in vitro under a 16:8 hours light-dark photoperiod, and total darkness. Results: Higher germination values occurred in natural pollination (67.83 % in V. planifolia and 44.66 % in V. pompona) and metaxenia/xenia (63.2 and 51.66 %, respectively), along with larger fruits and seeds. Geitonogamy exhibited intermediate results (24.46 and 22.79 %, respectively), while self-pollination resulted in the lowest values (4.82 % in V. planifolia and none in V. pompona). Hybrids produced larger fruits, but their seeds did not germinate. Light exposure enhanced germination. Conclusions: Intra- and interspecific cross pollination promotes germination in vanilla. Hybrid fruits could represent a commercial alternative to traditional vanilla crop.