Introduction
In the first part of the tissue culture of Lily, you’ve learned a brief description of the Lily plant and the techniques to grow these plants. You’ve learned a protocol of tissue culturing Lily using bulb-scale as an explant, which is a well-known technique to clone plants at a commercial scale.
This article provides a glimpse of the types of Lily present around us and talks about other tissue culture techniques, other than what we discussed in the previous article, that can also be used to grow these plants under in vitro conditions.
Types of Lily Plant
How many types of lilies are you aware of? Well, generally gardeners don’t know about all the lilies, which grow and bloom at different times of the summer. Let’s have a look at what they are:
- Asiatic Lilies: These lilies bloom in early to midsummer. They are produced after breeding several different species of lilies. Their color ranges from orange, red, yellow, and creamy white. Asiatic lilies are not fragrant and smaller than other types of lilies. They have straight and strong stems and have 3 to 6 flowers per stem with spotted petals.
- Martagons: They are also known as Turk’s cap lilies. They are available in shades of orange, yellow, red, and pink. They grow 3-4 feet tall and each stem contains a dozen of flowers.
- Trumpet Lilies: They are named after their trumpet-shaped flowers. They are sub-categorized into two groups: Aurelian lilies and Easter Lilies. They are long-lasting and highly fragrant, and present in a spectrum of colors, ranging from white, yellow, orange, cream, to pink.
- Tiger Lilies: These have larger, pendulous blooms with recurved petals. Their colors range from golden yellow, orange, to red colors and have a dozen or more flowers on each stem.
- Rubrum Lilies: They resemble tiger lilies with recurved petals. They are fragrant and range from white to deep pink in color.
- Oriental Lilies: They are the most fragrant of all lilies. They are present in color shades of pink, purplish red, white, and creamy yellow. They are tall and bloom around mid to late summer during the time of Asiatic lilies.
Tissue Culture of Lilies
Direct and Indirect organogenesis is one of the most commonly used tissue culture techniques, to grow lilies, by culturists worldwide. In the previous part of the tissue culture of lilies, you learned to grow the plant using bulb scale as explant. But, in this article, we’ve covered the ways to culture the plants using other different explants including bulbscale, root, and leaves.
Bulbscale is the most commonly used explant for the propagation of Lilies. But scientists have observed a high contamination rate in plants, grown using bulbscales when transferred to soil. Modified MS media or LS media are used to grow the Lily plant under in vitro conditions.
Takayama and Misawa (1979, 1983) used liquid cultures of microscales and got an estimate of 1.2x 1010 bulblets of L.speciosum per year and 3.2x1012 bulblets of L. aurantum per year. Further, some scientists have observed that liquid cultures with aeration give the best result in the mass propagation of Lilies. Increased bulblet differentiation can be achieved by using g 3/4 strength MS salts, 40% sucrose, and 0.1 mg/l NAA.
In the tissue culture of L.dvidii, the lower part of the bulb scale cultured on MS media supplemented with 2 mg/1 BA and 0.2 mg/1 NAA is observed to have the best results. But, in Asiatic and oriental lilies, the middle part of the bulb scale shows more regenerative capacity than the distal and basal portions.
Some reports suggest that leaf explants are best when it comes to enhancing the productivity of lily plants. Leaf segments of oriental and Asiatic hybrids of lily, when grown on MS medium supplemented with 1 or 1.5 mg/l NAA provided efficient and direct bulblet regeneration.
There are some advantages of using root as an explant for lily propagation, which includes easy manipulation and less oxidation after excision compared to other organs of plants. It has been observed that in the hybrid Rosato, the middle portion of the root explant provides the highest number of bulblet regeneration compared to the distal portion.
Embryo, Ovule, and Ovary Culture
Post-fertilization barriers can be overcome by using embryo rescue techniques which include ovary culture, ovary-ovule culture, and immature embryo culture. Studies report seedling formation in Lily plant when ovule with placental tissue (as an explant) is collected from each carpel after 30 and 40 days of pollination, and cultured on a medium composed of major salts of B5, macronutrient, micronutrient, Fe-EDTA (Fe-ethylenediamine tetraacetic acid) and vitamins of MS, 5% sucrose and 0.2% gel.
In the case of ovary culture, the ovary collected after four weeks of pollination resulted in a greater number of plantlets. The same case was observed for embryos, that is in vitro culture of embryos excised four to six weeks after pollination provided better results. MS medium supplemented with 3% sucrose, 0.7% agar, and 0.01 mg/l NAA was found to be most suitable for growing the plant.
Protoplast culture and Somatic Embryogenesis
Cell suspension cultures and regenerative callus have vast applications in tissue culture. During the regenerative phase of cell suspension culture, which is initiated from a friable callus, somatic embryogenesis is observed.
Embryogenic suspension cultures is a recent technique discovered for the propagation of bulbous crops. Mii et al. (1994) reported the regeneration of plantlets from protoplasts using suspension culture of seed-derived callus of L. x formolongi. Several studies confirm that regeneration of lilies using protoplast culture is possible, which results in embryo-like structure through somatic embryogenesis.
Factors Affecting In Vitro Bulblet Growth
The in vitro propagation and production of lily plants depends on several factors, which is covered in this section of the article:
Sucrose, Light, and Temperature Effect
- High sucrose concentration (60-90 grams/liter) facilitates the formation of large size of bulblets.
- Treatment of plants by low temperature before planting is an effective technique to break dormancy. For example, treatment of Lilium auratum at 5°C for 50 to 100 days; L. longiflorum at 4°C for at least one week; and L. speciosum at 2°C for six weeks.
- In L. longiflorum, the mass of bulblet is found to be significantly greater in dark than light.
- Supplementing the medium with maleic hydrazide, salicylic acid, and paclobutrazol increases the in vitro bulblet growth of Lilium cv. Toscana.
Acclimatization Conditions
- A high survival rate of Lilium x 'Connecticut King’ has been observed when transplanted in the potting mixture of sand, peat moss, and humus soil (1:1:1).
- Vermiculite has been observed as the best medium for the propagation of Lilium.
- Bulblets of Lilium longiflorum cv. Ace cultured in vitro in the dark at 30°C produced leaves more rapidly after transplanting to vermiculite.
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