APPLICATION OF THREE POLLINATION TECHNIQUES AND OF HORMONE TREATMENTS FOR OVERCOMING INTERSPECIFIC CROSSING BARRIERS IN TULIPA

In tulip, interspecific crossing is restricted by both pre-fertilization and post-fertilization barriers. In order to introduce traits from wild species into the cultivar assortment these barriers must be bypassed. By application of embryo rescue techniques, unique hybrids have been obtained of several interspecific tulip crosses. Recently, four techniques have been tested on their capacity to overcome interspecific crossing barriers in tulip, namely hormone treatments of ovaries, cut-style method, grafted-ovary method and placental pollination. After treating ovaries with 0.1 percent BAP at 12 days after pollination, seeds were obtained on the plant from the cross T. gesneriana x T. agenensis. This cross has never been given seeds in vivo before. Treating ovaries with 1 percent BAP seemed to have a negative effect on seedset in compatible crosses, 1 percent NAA did not give any effect. After the application of the cut-style method, the percentage pollen tube penetration did not increase in crosses between T. gesneriana and 5 other Tulipa species. Apparently, crossing barriers were not overcome by using the cut-style method, nor after using the grafted-ovary method. After placental pollination, pollen tube penetration percentages were not increased compared to stigmatic pollination, however, most of the penetrated ovules with pollen tube penetration showedd embryo germination.