Final policy review: Alternative risk management measures to import Lilium spp cut flowers from Taiwan
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Lilium spp. propagation, commercial cultivation and Taiwan’s commercial production practicesThis chapter provides general information on varieties of Lilium spp. of commercial floricultural importance, and on lily propagation. It also provides specific information on the commercial production practices for Lilium spp. cut flowers in Taiwan and considers pre-harvest, harvest and post-harvest practices. The export capacity of Taiwan is also outlined. 1.4Lilium spp. varieties, propagation and commercial cultivationThis review will cover varieties of Lilium of commercial floricultural importance. Lilies comprise more than 80 species belonging to several sections or divisions (Lim et al. 2008). The divisions have no botanical significance but are for the convenience of gardeners (Mikolajski 2004). Lilies have been divided to 10 divisions of closely related hybrids and taxa for horticultural use. These include Asiatic, Martagon, Candidum, American, Longiflorum hybrids (mostly L. longiflorum × Asiatic), Trumpet and Aurelian hybrids, Oriental, Orienpet (Trumpet Aurelian × Oriental) hybrids, as well as true species and miscellaneous (not included in other divisions) (Mc Rae 1998).Within the divisions, cultivars bred from Lilium longiflorum (Leucolirion) hybrids, Asiatic (Sinomartagon) and Oriental (Archelirion) hybrids are the most important in the commercial market (Lim et al. 2008). These important hybrid groups for cut flowers have distinctive characteristics. Longiflorum hybrids have trumpet-shaped, outward-facing white flowers, a distinctive fragrance with the ability for forcing year-round (Lim and Van Tuyl 2007). Asiatic hybrids have a large range of colours with upright-facing flowers and have early to late flowering types; Oriental hybrids also have early to late flowering types, a strong fragrance with pink or white flowers, sturdy stems with wide dark green leaves (Lim and Van Tuyl 2007). Many new hybrids have been introduced in recent years, interspecific hybrids of L. longiflorum × L. × elegans (LA hybrids), L. longiflorum × Oriental lilies (LO hybrids), and Oriental × Trumpet lilies (Orienpet or OT hybrids) (Roh 2011). Lilies are propagated through seeds (providing genetic diversity and freedom from viral and other pathogens) or vegetatively (exact copies of the mother plant) predominantly through bulbs, bulb scales, bulblets, and bulbils (McRae 1998, Jefferson-Brown and Howland 2002). Bulblets are daughter bulbs that develop on the underground portion of the stem in close proximity to the mother bulb. Bulbils are adventitious bulbs formed on the stem or inflorescence above ground of some species of Lilium, and have a demonstrated capacity to regenerate new plant material (McRae 1998, Jefferson-Brown and Howland 2002). Propagation from underground parts such as basal plate scales, stem bulblets (juvenile bulbs that are produced below soil level above the top of the bulb) are all vegetative methods of lily propagation that are not of concern in cut flowers. However, lily plant tissues of some species (and their cultivars) have a high generation potential and may also be propagable by bulbils, or by leaf and stem cuttings (Luo and Liu 1993, Anon. 1993, Ruffoni et al. 2011). Kim et al. (2007) induced bulbil formation by growing bulbs (of L. longiflorum ‘Nellie White’) at different temperature and photoperiod regimes, though this is undesirable as it is presumed to be detrimental to bulb production since bulbils are a competitive sink for carbohydrates from the main plant. Ruffoni et al. (2011) state that lilies are one of the most important bulbous crops produced in tissue culture and on an industrial scale nowadays. Commercial hybrid floricultural varieties are usually bred to maximise flower beauty and attractive cut flower features (e.g. scent). These are not known to form bulbils like the original mother species used to generate commercially viable crosses, and thus are not propagable via bulbils. A few species of Lilium, such as Lilium lancifolium (or L. tigrinum), L. sargentiae, L. sulphureum (or L. myriophyllum) and L. bulbiferum (L. croceum, L. chaixii), as well as L. × elegans (an Asiatic lily), and their cultivars and hybrids, are known for producing stem or leaf axis bulbils in abundance (Roh 1992, McRae 1998, Jefferson-Brown and Howland 2002, GRIN 2012, Asker 2012). For instance, LA hybrids (LAIH) of L. longiflorum and L. × elegans Asiatic hybrid lilies may carry axil bulbils derived from L. × elegans in interspecific crosses (Roh et al. 1996). Later research by the same author describes bulbils only from L. × elegans (Asiatic hybrid) and the use of tissue culture for propagation of interhybrid crosses of Asiatics with Longiflorum (LAIH) (Roh et al. 2008, Roh 2011). Roh (2011) also identified some L. longiflorum × Oriental lilies (LO hybrids) as able to form axil bulbils. Another example is Asiatic hybrid cultivar “Brunello” (Asker 2012). It is noteworthy that the bulbil-production trait by hybrid lily varieties/cultivars can occur at a very low rate depending on the parent lineages used in the cross. If the parent/ancestor is a known bulbil producer (for example L. sargentiae, a Trumpet lily parent, or L. lancifolium, an Asiatic lily parent) crossed with non-bulbil-forming varieties, the resulting hybrid may occasionally produce bulbils. However, not all hybrids will have a bulbil-producing parent/s, or the same ancestry. Bulbils develop early in the season and can be harvested shortly before they would drop naturally, that is when the parent plant flowers. Several studies have reported the stimulation of bulbil formation by various treatments such as flower bud removal, use of growth regulators and retardants, and use of organic acids (Asker 2012). Ryczkowski (2012) states that not all Lilium species form bulbils but can be forced to do so by removing flower bulbs and cutting off the upper half of stems (Ryczkowski 2012, Asker 2012), while other sources state bulbils can only be forced from the species listed above that are naturally bulbil-forming (Herbs 2000). Thus, commercially grown non-bulbil forming lilies, intended for commercial sale, that have reached flowering stage in flower bud, or in bloom, cannot be forced to produce bulbils. Furthermore, if the conditions of import require only bulbil-free flowers to be traded, the presence of bulbils will be evident upon visual inspection. Most bulbs used for cut-flower production and sold to cut flower growers are grown in the Netherlands, Chile, France, New Zealand, South Africa, and north-western USA as commercial production of bulbs requires a cool environment (Gill et al. 2006). Lilies can be grown in the field in raised beds, in high tunnels, or in greenhouses (some in crates). Best conditions combine a loamy soil with good drainage, pH of 6.3–6.8, 6–8 hours of daily sun, and frequent watering. Cut flower stems are harvested when flowers are in the bud stage, when the lower-most buds show colour to allow the flowers to open after purchase by consumers. Prior to shipping, cut flowers are pulsed in sucrose solution and germicides, and stored with floral preservatives (silver thiosulphate or STS) to prolong their vase life (up to
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