ARUM LILLIES

Propagation Technique for Zantedeshia aethiopica

For most bulbous crops there are a few propagation techniques that have been developed over the years and choosing the type of technique is very important.

For the Arum lily (‘Zantedeshia aethiopica’) there are but two different ways of propagating the bulbs, scaling and micro propagation. Because the speed of the scaling method is often low, introduction of newly bred cultivars or of pathogen free bulbs requires a long period of time. Micropropagation considerably shortens this period. Furthermore, because of the large number of propagation cycles in the field, conventionally produced bulbs may become easily infected. Micropropagation produces starting material that is completely pathogen free.

When Micropropagation is used, bulblets is produced instead of microcuttings (with scaling technique). This is important due to the fact that bulblets mostly do not require a rooting treatment and acclimation. But they do require breaking of dormancy.

Micropropagation consists of six stages:

1. Mother plant preparation: Storage of bulbs may determine the ability to regenerate. To avoid contamination, healthy undamaged bulbs are used. 
   
2. Initiation: Explants are derived from scales or flower stems. From these explants, adventitious shoots/bulblets regenerate in-vitro. Apical and axillary buds may also be used and may be the preferable explant, since they give better results in virus elimination and also have better propagation rates.
3. Propagation: Both shoots and bulblets can be used for further adventisious or axillary propagation.
4. Bulb growth: In the final propagation cycle, bulblets should be produced. They are firm structures and can be handled easily. Conditions stimulationg bulb growth include high sucrose concentration, absence or very low concentration of growth regulators, darkness, charcoal and moderate temperatures.
5. Dormancy breaking: For fast uniform sprouting and for optimal growth, bulblets need a temperature treatment to break dormancy. This requires either several weeks at low temperatures (2°-9°C)
6. Planting: For planting usually the same steamed potting composts can be used as for conventionally propagated bulbs. During the first year, growth should be done in a greenhouse with regulated temperatures, humidity and also Carbon dioxide. 

Materials:

1. Clean, healthy bulbs
2. 70% (v/v) Alcahol
3. Sterile water
4. Sodium hypochlorite solution (1% available chlorine)+ 0.03 / Tween 20 (Polysorbate 20)
5. Containers with medium: the mediumconsists of MS salts, 3% sucrose(w/v), 100mg/L myo-inositol, 0.4 mg/L thiamine-HCL, 0.27 mMc NAA, 0.6% (w/v) agar, and a pH of 6 before autoclaving. This medium can be used both for initiation and propagation. Bulb growth in the final step can be on the same medium, but with 6% extra sucrose

Method:

1. Remove roots.
2. Wash bulbs thoroughly with sterilized water.
3. Remove brown or damaged outer scales.
4. Peel off clean and healthy-looking scales. Remove brown tips. Since regeneration is best at the basal side of the scale, take care not to damage this part.
5. Rinse scales for about 30 s with 70% alcohol.
6. Sterilize scales for about 30 min in sodium hypochlorite.
7. Rinse 3 times with sterile water.
8. Cut explants of, about 7 x 7 mm.
9. Place explants with abaxial side on medium.
10. Explants can be cultured at 20°-25°C. In the dark, larger bulblets are obtained than in the light.
11. After about 10 weeks, regenerated bulblets can be used for further propagation. Individual scales of the bulblets are used as explants; large scales can be cut in two or three parts. this step can be repeated every 10 weeks.
12. After the final propagation cycle, larger bulblets ca be obtained by sub culturing single bulblets on medium with high-(6%) sucrose concentration for a number of weeks or months. This method is used to "store" the bulblets until planting time in the spring.
13. Before planting, bulblets receive a cold treatment of several (6-12) week at 5°C in the dark.
14. Bulblets are excised from the explant, planted in soil, and grown in a gauze house (at 17°C, most bulblets will sprout within 2-4 weeks)

Notes :

• Before storage the bulbs are given cold treatment after harvest, and then packed in moistened sterilized peat and stored at -1°C.
• The optimal NAA concentration for regeneration decreases with the duration of the storage time.
•   To obtain regeneration after a hot water treatment, bulbs should be stored dry at 30°C immediately after harvest.
• Rooting is essential for optimal growth after planting. Without roots, leaves remain small and die a few weeks later. Rooted bulblets do not need a cold treatment to break dormancy.

Fertilizer:

Although inorganic fertilizers are more readily available,we believe in using organic fertilizers. Inorganic fertilizers has the ability to burn the roots, the basal plate as well as the leaves if it comes in direct contact with it, which is another reason why we prefer organic products as it does not have these dramatic negative effects when the concentration of the fertilizer is slightly off.

Fertilizers come in granular or liquid form. Granular fertilizers are better because the don't dissolve as quickly, they remain in the soil longer, and the longer the better.
Nitrogen (N) is important for preparing soils for bulbs to be able to start their leaf growth. Phosphorus(P) and Potash are good for overall health, resisting disease, root growth and flowering.

When adding granular fertilizers, mix with soil ate the bottom of the planting holes. Adding a very diluted liquid fertilizer to the misting system, that regulates the relative humidity in the greenhouse, is a good way of insuring that the plants have enough nutrients, as the fertilizers will permeate directly into the plants system through the leaves.



Preparation of Soil:

Adding organic matter for preparing soil for bulbs improve the soil by improving low fertility, poor water-holding sandy soils and fertile but poorly draining clay soils( the soil in Paarl is slightly acidic and usually require the addition of lime). When adding organic matter to the soil, remember that it breaks down each year and has to be replenished each year.
It's easier to amend the soil when you dig up the land before planting each year. This method allows you to layer about 5 cm of organic matter and work it in well with the soil. After that, in the future we can simply apply the organic matter as mulch and it will work into the soil below.