EVALUATION OF PRE-FERTILIZATION BARRIERS BY OBSERVATION OF POLLEN TUBE GROWTH AND ATTEMPTS FOR OVERCOMING POST-FERTILIZATION BARRIERS IN INTERGENERIC HYBRIDIZATION BETWEEN ALSTROEMERIA AND BOMAREA BY OVULE CULTURE

Abstract

In the flower market there is a continuous demand for new cultivars of Alstroemeria as an ornamental flower. Many interspecific hybrids of Alstroemeria are utilized for commercial cultivars. However there is no report about intergeneric hybridization between Alstroemeria and Bomarea. We are investigating the possibility of creating intergeneric hybrids between Alstroemeria and Bomarea. Moreover, ovule culture conditions were examined for overcoming post-fertilization barriers after pollination of Bomarea pollen grains to A. aurea, A. pelegrina var. rosea and A. magenta. The frequency of pollen tube entry into ovules was compared in the pistil of A. aurea, A. pelegrina var. rosea and A. magenta after pollination of B. coccinea pollen grains. Pollen tubes in Alstroemeria ovaries were observed with aniline blue staining 48 hours after pollination. The frequencies of pollen tube entry into ovules were 0.3, 5.6 and 10.0% in A. aurea, A. pelegrina var. rosea and A. magenta, respectively. For ovule culture, pollinated ovaries were harvested 3 and 7 days after pollination, and the ovules were cultured on 2 g L -1 gellan gum-solidified MS medium with or without gibberellic acid, and supplemented with sucrose at different concentrations (30, 60, 80 or 100 g L -1 ). As a result, 3 plantlets were obtained in A. pelegrina var. rosea x B. coccinea cultured on MS medium supplemented with 80 g L -1 sucrose. Although pollen tubes of B. coccinea were reached to A. aurea ovules, this combination might have stronger pre-fertilization barriers than those of A. pelegrina var. rosea and A. magenta. It supposed to be different intensity of pre-fertilization barriers among species. Our data also suggested that sucrose concentration at 80 g L -1 in culture medium was effective to obtain progenies after intergeneric pollination. Confirmation of hybrid natures for the plantlets is now in progress.