EMBRYO RESCUE BY HALF-OVULE CULTURE FOR THE PRODUCTION OF INTERSPECIFIC HYBRIDS IN ALSTROEMERIA

Interspecific hybridization in the genus Alstroemeria is hindered by p ost-fertilization barriers. Histological analysis revealed poor endosp erm development from 18 days after pollination onwards, followed by ma lformation and abortion of embryos. To create interspecific hybrids be tween Alstroemeria aurea, Alstroemeria pelegrina, Alstroemeria magnifi ca, Alstroemeria inodora and Alstroemeria psittacina in diallelic comb inations, an ovule culture technique was developed. Influence of age o f ovules, sucrose concentration of medium and temperature and light du ring culture were tested. Harvesting ovules before the onset of endosp erm degeneration, i.e. at 14 days after pollination, cutting them into halves and culturing the micropylar halves in a rotating liquid cultu re medium containing 6% sucrose at 21 degrees C in the dark, led to su ccessful embryo rescue. Germinated embryos were subcultured in vitro u ntil rhizomes were formed, a prerequisite for successful transfer to t he greenhouse. Full grown plants all showed interspecific morphologica l traits and analysis of chromosome complement confirmed their hybrid nature. Diploid hybrid plants were obtained in all the 20 interspecifi c 2x-2x combinations. A total of 260 interspecific hybrid plants was p roduced. Half-ovule culture of 2x-4x and 4x-2x crosses resulted in 43 triploid hybrid plants. Because interspecific hybrids were obtained in 100% of the interspecific combinations, it is expected that the descr ibed technique can be applied to overcome post-fertilization barriers in most crosses within the genus Alstroemeria.