J.M. van Tuyl, H.M.C. van Holsteijn, A.A.M. Kwakkenbos
Polyploidization plays an important role in the interspecific breeding of lilies. The reasons for using polyploidy in lily breeding are the larger flowers, the stronger stems (especially important for forcing under low light conditions during the winter period) and in interspecific hybridization the restoration of F1-sterility at the tetraploid level. A distinction was made between mitotic polyploidization and meiotic polyploidization. Mitotic polyploidization comprises all techniques in which artificial chromosome number doubling was accomplished by treating bulb material with colchicine. Meiotic polyploidization is a more natural method through which polyploids are obtained by the occurrence of 2n- or so-called unreduced gametes. Detection of tetraploids obtained after colchicine treatment using flow cytometry appeared to be very efficient. Applying this method showed the existence of many chimeras. From the existence of these chimeras it can be concluded that the origin of adventive bulblets from lily scales in most cases is not a one-cell-occurrence. This in contrary to the general opinion up till now. Of various diploid sterile interspecific hybrids tetraploid forms were selected after colchicine treatment. A restoration of fertility in these forms could be demonstrated.

When within populations of interspecific hybrids more carefully was looked for pollen fertility, formation of polyploids in a more natural way by the formation of unreduced gametes was found as well. Wide interspecific lily hybrids (e.g. hybrids of the cross L. longi-florum x L. candidum and L. auratum x L. henryi) are usually completely male and female sterile. In rare cases, however, some fertile pollen was produced. It appeared that 100% of this pollen is 2n-pollen. In the less wide interspecific cross between the Asiatic hybrid 'Enchantment' and L. pumilum the fertile hybrids produce, besides normal n-pollen, a high percentage of 2n-pollen.

van Tuyl, J.M., van Holsteijn, H.M.C. and Kwakkenbos, A.A.M. (1990). RESEARCH ON POLYPLOIDY IN INTERSPECIFIC HYBRIDIZATION OF LILY. Acta Hortic. 266, 323-330
DOI: 10.17660/ActaHortic.1990.266.42

Acta Horticulturae