APPLICATION OF FOUR POLLINATION TECHNIQUES AND OF HORMONE TREATMENT FOR BYPASSING INTERSPECIFIC CROSSING BARRIERS IN LILIUM L.

Abstract

Crosses between genotypes of the 3 commercially important groups of lilies, i.e. Lilium longiflorum Thunb., the Asiatic hybrids and the Oriental hybrids, are hampered by interspecific crossing barriers. Several methods have been developed to bypass pre-fertilization barriers or post-fertilization barriers in lily, e.g. the cut-style method and embryo rescue techniques. Five techniques were studied comparatively for their capacity to bypass barriers between different types of lilies: the grafted-ovary method, placental pollination, warm-water treatment, the mentor pollen technique and hormone treatment. For the grafted-ovary method, a compatible pollinated pistil was grafted one day after pollination on the ovary of another species. It appeared that the pollen tubes were not able to penetrate from one ovary into another ovary. After placental pollination, no embryo germination was found, even not when pre-pollinated styles were placed near the ovules. After a warm-water treatment (6 minutes of 50 C) of pistils, many seeds were harvested of self-pollinated flowers of L. longiflorum. However, interspecific crossing barriers could not be bypassed. The percentage of ovules with pollen tube penetration did not change by mixing pollen with radiated mentor pollen. It appeared that the mentor pollen were able to penetrate the ovules. After treating ovaries with 0.1% BAP, on average 6 embryos per flower of the cross L. longiflorum 'Gelria' x Asiatic hybrid 'Mont Blanc' could be rescued when ovule culture was started around 40 days after pollination.