Controlled Flowering in the Genus Lilium - Review of the Past Achievements and the Future Direction of Research

Many new cultivars of Lilium longiflorum, L. xelegans (Asiatic hybrid lily), and many hybrid lilies have been introduced in recent years. In the past 10-15 years, interspecific hybrids of L. longiflorum x L. xelegans (LA hybrids), L. longiflorum x Oriental lilies (LO hybrids), and Oriental lilies x Trumpet lilies (OT hybrids) were also introduced. LA hybrid lilies are available in many colors and forms and are now gradually replacing the Easter lily in the US as they are forced year-round. Growth and flowering of the Easter lily and Asiatic hybrid lilies, as influenced by temperature and photoperiod, has been investigated in detail. Information on the physiology of bulb development, controlled flowering, and timing for the Easter, and to certain extent for the Asiatic hybrid lily is readily available. However, LA, LO, and OT hybrids are generally forced following bulb vernalization. Available information on bulb dormancy, maturity, and requirements for temperature and photoperiod involved in growth, forcing, and flowering obtained in the Easter lily will be reviewed. Can breeding efforts provide new cultivars (a) that do not require temperature and photoperiod treatment for flowering - temperature and photoperiod neutral characters, (b) that produce stem bulbils that can be forced to flower without involving the bulb production phase, (c) that produce flowers from small scales, seeds or bulbs, (d) that can flower under a low light intensity, or (e) that can combine lines obtained from classical breeding and genetic engineering to create disease and insects resistant lines, particularly in the L. longiflorum? The feasibility of accomplishing objectives of producing high quality and disease-free hybrid lilies in one year from propagation will be discussed.