Meiotic polyploidization with homoeologous recombination induced by caffeine treatment in interspecific lily hybrids

Caffeine solution was injected into the flower bud to recover F₁ fertility of the intersectional diploid Lilium species hybrid (2n=2x=24). 0.3% of caffeine solution was the most effective concentration to produce fertile 2n-gametes. The male and female gametes had a range of fertility following caffeine injection in relation to the different sizes of flower buds. The gametes from the treated OA-hybrids showed to be fertile. They were crossed both as male and female parents to the Asiatics, and produced 279 BC₁ progeny plants. Flowcytometric and chromosomal observation confirmed that all progenies were triploid (2n=3x=36), indicating that the 2n-gametes from the OA-hybrid were functional following caffeine treatment. There was no homoeologous recombination between parental species in the progeny derived from male gametes of the OA-hybrid. However, three plants originating from the female gametes showed homoeologous recombination between Oriental and Asiatic genomes. The functional female gametes were produced when treated at the range of 20-23mm and 34-37mm of flower bud length. Based on the chromosome constitution of the triploid BC₁ progenies, it was concluded that FDR 2n-gamete was functional and homoeologous recombination had occurred during the origin of 2n gametes.