Abstract Tetraploid plants usually grow more vigorously and produce larger flowers than their diploids. To breed tetraploid poted Asiatic lilies, the present study carried out the crosses among Asiatic lily(Lilium) cultivars Petit Brigitte, Orange Pixie, Black Bird, and Pollyanna with normal artificial pollination, then, the scales of the progenies obtained from three crossing combination were treated 4 h with 0.001%, 0.002%, 0.003% and 0.005% Oryzalin, and the regenerated bulblets were analyzed with chromosome preparation and fluorescence in situ hybridization(FISH) technique. The results showed that the chromosome doubling rates were 19% and 23% with 0.003% and 0.005% Oryzalin respectively, and FISH not only confirmed the chromosome doubled plants, but indicated that some particular chromosomes might not be doubled in some plants. The present result conformed that Oryzalin is effective to double lily chromosomes, and that cytological method, combined with FISH technique, enable individual chromosomes whether to be doubled or not more accurately.
