Production of 2n pollen of Asiatic hybrid lilies by nitrous oxide treatment Masako Akutsu Æ Satomi Kitamura Æ Ryo Toda Æ Ichiro Miyajima Æ Keiichi Okazaki Received: 16 September 2006 / Accepted: 23 November 2006 / Published online: 27 December 2006 Ó Springer Science+Business Media B.V. 2006 Abstract Tetraploid varieties of lilies have supe- rior agronomic traits such as large flowers and resistance to physiological disorders. In the present study, we attempted to induce 2n pollen of Asiatic hybrid lilies by arresting the meiotic process with nitrous oxide (N 2 O) gas. To determine which meiotic stage is optimal for induction of 2n pollen, plants with attached buds at different meiotic stages were treated with N 2 O for 24 h in a pressure-tolerant cylinder. A few 2n pollen grains were induced using plants with anthers in prophase I, whereas mixed pollen grains of differing size were produced using plants undergoing meiotic metaphase predominantly in anthers. Although normal lily pollen grains are elliptical, nitrous oxide exposure induced giant pollen grains that appeared spherical. Flow cytometry analysis showed that the giant pollen grains were diploid. When mixed pollen that included normal and giant pollen was crossed to tetraploid cultivars, the resulting seedlings were tetraploid and aneuploid, indicating that the giant pollen grains were diploids that could generate tetraploid seedlings through fusion to diploid eggs supplied from a tetraploid female parent. Thus, treatment with N 2 O is useful for the production of 2n lily pollen and may provide a new approach for tetraploid lily breeding. Keywords Chromosome doubling Á Flow cytometry Á Lilium Á Meiosis Á Nitrous oxide Á 2n pollen Introduction Asiatic hybrid lilies (Lilium spp.) are derived from interspecific crosses with species of the section Sinomartagon, including Lilium dauricum, L. lancifolium and others (Nishikawa et al. 2001), and are some of the most commercially important types of cut flowers in the world. Asiatic hybrid lily bulbs are produced mainly in Holland and many cultivars of Asiatic hybrid lilies have been registered in Holland (Lim et al. 2002), but their production has increased recently in southern hemisphere countries such as Australia, New Zealand and Chile because these regions can supply bulbs in the off-season of the northern hemisphere. M. Akutsu Á S. Kitamura Á R. Toda Á K. Okazaki (&) Faculty of Agriculture, Niigata University, Ikarashi, Niigata 2-8050, Japan e-mail: okazaki@agr.niigata-u.ac.jp I. Miyajima Horticultural Research Center, Niigata Agricultural Research Institute, Seiro, Niigata 957-0111, Japan Present Address: M. Akutsu Local Crop Breeding Research Team, National Agricultural Research Center for Hokkaido Region, 1 Hitsujigaoka, Toyohiraku, Sapporo, Hokkaido 062-8555, Japan 123 Euphytica (2007) 155:143–152 DOI 10.1007/s10681-006-9317-y