Autopolyploid Induced Sterility in the African Tulip tree (Spathodea campanulata)

The African tulip tree (Spathodea campanulata, Bignoniaceae) is a West African evergreen tree that has been introduced throughout the tropics as an attractive landscape species and has become an invasive pest in managed and natural ecosystems in Hawaii, the Cook Islands, Fiji, Guam, Samoa, Tahiti and Vanuatu due to its prolific production of light-weight, wind-dispersed seeds. A sterile, non-seeding form of this species would be desirable for landscape purposes. Since a triploid (3N) plant, the progeny of a tetraploid (4N) crossed to a diploid (2N) would likely be sterile, attempts were made to first create a tetraploid plant by treating meristems of diploid seedlings with solutions of colchicine. Tetraploid and mixoploid (2N and 4N tissues) plants were created. Ploidy increase was verified by guard cell measurements and flow cytometry. One mixoploid plant has shown a high level of sterility, having produced over 100 inflorescences in the past three years resulting in just a single fruit, while control plants produce 6 to 10 fruits per inflorescence.