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"The INBAR-UPLB-ERDB International Training on Bamboo Propagation: Techniques, Utilization and Program Development"
Micro-Propagation of Bamboo
Dr. Alfinetta B. Zamora
Plant Cell and Tissue Culture laboratory
Institute of Plant Breeding, College of Agriculture,
University of the Philippines Los Banos,
Los Banos, Laguna, Philippines
Funded and On-line Published by
International Network for Bamboo and Rattan (INBAR)
Branch Box 100101-80, Beijing 100101
Peoples’ Republic of China
TABLE OF CONTENTS
1. Micro-propagation Protocols
2. What Do I Need To Do Micro-propagation?
3. Making the Most of Seeds and Seedlings
4. I Wanna Be Just Like You
5. Getting Ready for the Real World
6. Try Mini-clump Division
7. Making Up For Lost Forests
8. Help Me Out
Appendix . Preparation of Stock Solution
SECTION 1. MICROPROPAGATION PROTOCOLS
In this section, we would like you to learn about in vitro technologies and their application to plant propagation. "In vitro" connotes artificiality and the first mental picture that you might have will be a test tube. This is essentially what micropropagation is. Plants are grown under an artificial environment within confines of a culture vessel typified by a test tube. How can a plant grow in such conditions? Will you have to use seeds?
What is micropropagation?
Micropropagation is the development of new plants in an artificial medium under aseptic conditions. You do not have to start with seeds but you can use different parts of a plant as a starting materials to establish an in vitro culture. These will include embryos, pollen grains and parts such as stems, shoot tips, nodes, root tips, callus and single cells.
You may consider using seeds when asexual methods using traditional horticultural techniques are not possible, for example in coconut. Seeds are not useful to initiate tissue cultures when the candidate plant are apomictic. In such plants, the embryos are not regular embryos that form from fusion of male and female gametes. Instead, it develop from the cells in the nucellus or integuments of the seed. Seeds are also useful for initiating in vitro cultures of plants when it is difficult to use other plant parts and when it is not necessary that the plants are copies of a selection. Such is the present situation in bamboo.
When other parts of the plant are used for in vitro culture, you can anticipate the outcome. Almost exact copies of the source plant are typical.
High tech stuff?
The beginnings of this method can be traced to the earliest (although unsuccessful) attempt to grow plant tissues in aseptic culture by Haberlandt in 1902. Initially, the tissue culture methodologies were research tools. However, with a greater understanding of how cells grow and how shoots and roots can form in vitro in many economic plants, the methodologies were applied to propagation.
Why propagate plant through in vitro technologies? The primary applications of these techniques to plant propagation are: (a) to enable rapid multiplication under conditions that maintain freedom from disease, (b) to establish pathogen-free plants, and (c) to isolate genetically unique cells or cell lines that can become new plant variants (Hartmann and Kester, 1975).
Can we micropropagate bamboo?
The bamboo is among the many plants that have been successfully propagated by in vitro technologies, being the subject of many researches undertaken by several laboratories for many years (Zamora, 1994). The earliest report on bamboo tissue culture was in 1968 by Alexander and Rao. The increase in published papers in the last 10 – 15 years signify that it will simply be a matter of time (and research and interested scientists) before each and every economic bamboo would be cultured in vitro. Table 1.1 summarizes the genera and species for which reports are available on micropropagation.
What can you use for establishing cultures?
A scan of literature shows that the most amenable initial material for micropropagation is the seed. The seed, specifically the embryo, is most adapted to any propagation system, be this in vitro or ex vitro. It has several characteristics that make it ideal as planting material for tissue culture. First, it is small and as such several seeds can be disinfected in a small container at the same time. Second, the embryo is dormant and as such more amenable to harsher disinfection procedures, Third, seeds are easier to transport than other plant parts, Fourth, you may store them and initiate cultures from them throughout the year.
Other juvenile materials, e.g. seedlings, are also very amenable to culture. Seeds can be aseptically germinated and the seedlings in vitro can be used to initiate new cultures.
Aside from juvenile plant materials, the initial plant materials for culture may be obtained from well-grown bamboo mats. The nodes and internodes from secondary branches and tissues from the ground corm are among plant parts in mature clumps which are used for culture. Some have also used flowers of bamboo to initiate cultures.
Table 1.2 compares three explants or explant sources (i.e. the seed, seedlings and adult clump) for micropropagatiing bamboos. Some points were taken from Saxena and Dhawan (1994).
How can you approach micropropagation?
You may consider several approaches to micropropagation in bamboo (Fig. 1.1 and 1.2). You may germinate seeds or embryos directly in vitro. You may induce the seeds to form multiple shoots or callus depending on the culture medium and environment. You may use the seedlings as sources of nodes for multiple shoot formation in media with cytokinins and auxins. Subsequently, you may root these shoots in vitro with auxin-supplemented medium.
You may induce seedling tissues to form calli. Then, you may multiply the calli by subculturing them regularly in an appropriate culture medium (usually with 2,4-D or a combination of auxins) and induce them to regenerate new shoots. If you were able to induce somatic embryoids, you may germinate them in vitro.
These different approaches using seed, embryo, seed/seedling tissues will give you more plants. If you label the individual sources, you will be able to tell later on on that some seeds and seed sources propagate better than others. We observed this in Gigantochloa levis. With this observation, several questions came to mind. First, if there is no selection, will I be propagating more of the potentially good bamboos? Does growth rate in vitro match growth rate ex vitro. Will the more persistent genotypes in vitro also have longer life spans ex vitro? We still have many questions regarding the possible performance of these propagations.
Aside from seed, you may use non-seed tissues that are meristematic (or with a capacity to cell division). You may induce callus with auxins (usually 2,4-D) and micropropagate the calli. Plants may also be obtained through the intermediary callus stage or through the germination of somatic embryoids formed directly from seed tissues or from embryogenic calli. You may use the nodes of lateral branches or culm buds for multiple shoot formatiom.
What is significant in the micropropagation protocols is that you use plant parts from mature clumps. Thus, this approach would be most useful in propagating superior bamboo clones. Succeeding sections shall describe various methodologies commonly applied to bamboo micropropagation. These will include the use of seed and seedling tissues as well as tissues and nodes from mature clumps.
Thought For the Section:
And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.
And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good. Taken from the book of Genesis 1:11-12 (Holy Bible).
The striking part of this page from the Holy bible is that the first group of plants God singled out was grass. When Mt. Pinatubo erupted in the Philippines, lahar and ashfall covered many towns in the Philippines. People thought these areas would take many years before anything could grow. The first vegetation that grew without man’s intervention was grass. Grass is the first among plants, in the succession of growths possible on land.
Bamboo belongs to the grass family and biblically can be used as one of the choices for man to reforest and rehabilitate degraded lands. Have you ever thought that we are in line with bible when we choose bamboo for replanting degraded lands?
SECTION 2. "WHAT DO I NEED TO DO MICROPROPAGATION?"
Now that you are interested in propagating bamboo by micropropagation, let us consider what you will need. Basic to all micropropagation technologies is a tissue culture facility. This does not have to fancy, just functional.
There are two main activities in a laboratory. These are preparative activities such as preparation of stock solutions and culture media, preparation of culture vessels when making media, preparation of plant materials for introduction to culture and when you want to pot them out. The other activities are all asepsis-related, such as disinfection and introduction to clean culture and maintenance for propagation and rooting. You should allot space in your laboratory for these activities.
A typical research laboratory would define space for distinct activities. So, separate rooms may be allotted to the storage of chemicals and equipment, culture media preparation, sterilization, inoculation, culture storage, observation and acclimatization.
On the other hand, a production laboratory needs not to be fancy. For example, orchid cultures have been stored in a nursery, in a garage, ordinary bedroom or in just a spare room in the house. What can we recommend for bamboo? It is up to you whether it is one room or more. However, you should consider the following points in your decision-making (a) mandate of the laboratory, and the (b) resources available for the laboratory. The mandate is important and covers questions like what crops will be cultured and whether it will be production only or research-production. The resources to be allocated are important. Whether you will consider an available space for renovation or construct a facility, when you will hire or whether you have to generate income to sustain your activities are all related to available resources.
With these considerations in mind, we can best help you to other references on establishing a facility and our perspective on establishing a facility. Among these references is "Mageau, O.C. 1991. Laboratory Design. Pp. 15-30. In: Micropropagation technology and application. Edited by P.C. Deberg and R.H. Zimmerman and published by Kluwer Academic Publishers, Netherlands." Other references for laboratory designs are included in this article. The floor layouts of a few laboratories that adapted available space are included in this section (Fig. 2.1).
Activities and suggested equipment vis a vis space
Enumerated are activities that you need to consider in the planning of your laboratory and the suggested equipment for these activities:
Stock solution preparation and storage
This area will house (a) weighing balances, (b) a refrigerator with freezer, (c) a distilling apparatus, (d) a stirrer-hot plate and (e) a work area with drawers and cabinets.
In places where power failure is frequent or unannounced, have pre-weighed amounts of chemicals for stock solution/media preparation. Stock solutions and crystals of growth regulators are often stored under reduced temperatures. Stock solutions are also best stored under refrigerated temperature to delay algae growth. Growth complexes such as coconut water can be stored in plastic bags and frozen in measured volumes. This permits you to retrieve frozen coconut water in volumes sufficient for your media preparation.
Distilled water is used in small quantities in the laboratory for your stock solution preparation and in large quantities for your media preparation. You may want to fabricate a unit for single distilled water (Fig. 2.2) or buy distilled water. These are available as bottled water (check labels).
Note: If you have a good rainwater collector, rainwater is an option to distilled water. However, you must be sure you do not have a problem of factories around your laboratory location, lest you collect polluted water.
A stirrer-hot plate can make media preparation and disinfection easier.
Preparation of culture media
For this activity, you will need (a) balances for macro and micro weighing, (b) a distilling apparatus, (c) stirrer-hot plate, (d) a pH meter and (e) a work table with access to sink and running water.
Note: (a) You can melt the agar using a stirrer-hot plate, cook it on a stove and stir it to prevent burning, put it in a microwave oven for a few minutes or you can put it in a pressure cooker and let the steam cook the agar. (b) a fancy pH meter is not necessary. A small, cheaper pH pen (electronic pH paper pen) will accomplish this job well.
Storage of culture medium before inoculation
You will need storage shelves where you can put the sterile culture media.
You will need: (a) a sterile working bench, (b) an air conditioner unit, (c) a dissecting microscope, (d) a storage shelf for small equipment, alcohol and sterile water and (e) a cart to facilitate transfer/movement of culture media from storage to inoculation area and back to storage or wash area.
The list of small equipment includes: forceps (different lengths which depend on the type of culture vessel used), scalpel handles and blades, curved scissors, sprayer or atomizer for alcohol, heavy bottles or couplin jar for alcohol and sterile water rinses, and a sterilizer for forceps, and other small equipment (may range from alcohol lamp, Bunsen burner or more fancy sterilizers). You will need a source of gas if you have a Bunsen burner for heat sterilization of small equipment.
Note: (a) If you are serious with your micropropagation, we recommend that you get an air conditioner if your laboratory is in the tropics. This increases protection for laminar flow cabinet and cultures against dust and dust-borne contaminants and increases efficiency of working staff. (b) Dissection of embryos becomes easier with a dissecting microscope. You can mount a magnifying glass and use this instead of a dissecting microscope to help you during dissection (Fig 2.3).
Culture storage area with storage shelves with light fixtures and timers
Note: (a) A room measuring 4x3 sq.m. and a ceiling height of 2.4 m when used as culture storage area can accommodate 4 shelves, each 3 m long and 40.5 cm wide, with 7 tiers. The total shelf space can accommodate more than 14,700 cultures or roughly 73,500 plants at a time. (b) Separate the ballasts of the light fixtures to minimize heating of shelves. (c) You may reduce number of light fixtures if the room has adequate natural light.
Kitchen/Washing area cum sterilization area
You will need (a) sterilizers (pressure cookers or autoclave), (b) stove or heavy duty burners and gas or electrical power, (c) draining and drying shelves, (d) storage shelves for clean glassware, (e) sink and (f) exhaust fan.
Washing can be segregated so that very dirty glassware or plant materials can be washed in this "dirty kitchen" area.
This area should have (a) work table or working carts, (b) a storage space for cultures being acclimatized and (c) a sink.
This area should have (a) a potting area, (b) a shaded area for newly potted plants, (c) storage bins for potting mix, (d) a sterilizer for potting mixes, (e) a source of water and (f) water storage containers.
Staff room and lavatory
The equipment which may be needed include (a) a simple typewriter or computers, (b) filing cabinet and (c) a small library for references.
Human resources are critical. Your propagation strategies may be implemented well with well-trained personnel. Changes in technicians also affect the productivity of a laboratory. So, help your staff remain with your laboratory. A room for the staff and a lavatory area should be included in the design of the laboratory. Provide a table where they can meet and discuss problems regarding their work or just to relax and eat. A lot of the work becomes routine and boring. You should invest in your staff to encourage them to remain with you.
Aside from function, you must plan for safety and efficiency in the layout of the available space you want to adapt for the facility. You should consider the number of access doors, ease of monitoring potential accidents and the ease of movement in case you need to vacate a room or the facility. Monitoring for potential accidents can be made easier if your work areas have glass panels (Fig. 2.4).
Safety also includes the availability of fire extinguishers, a manual on safety precautions regarding equipment use and first aid instructions particularly with materials used in the laboratory.
Efficiency considers the flow of activities and materials from the start to the finish of the culture systems and the maximum use of available resources.
You may also want to invest in a generator so that you have stand-by power in case of power failures.
Chemicals and other supplies
Aside from work areas and equipment, chemicals, laboratory and nursery supplies are necessary for the laboratory. The chemicals for the culture media are dependent on the formulation to be used. You will also need (a) ethyl alcohol, (b) buffer solutions, potassium hydroxide and hydrochloric acid to adjust pH of the media and solutions, (c) agar and (d) sucrose (or white high grade refined sugar).
The list of supplies include: (a) glassware such as measuring cylinders, culture vessels, amber glass bottles, etc., (b) detergent, (c) bleach, (d) matches, (e) liquefied petroleum gas for cooking, (f) rubber slippers which you can wash and disinfect, (g) cleaning implements (scotch brite, brush for bottles, sink, etc.) and (h) other supplies (fluorescent bulbs, cleaning materials) to maintain the laboratory.
Thought For the Section:
"Yea, if thou criest after knowledge, and liftest up thy voice for understanding; If thou seekest her as silver, and searchest for her as for hid treasures; Then shalt thou understand the fear of the Lord, and find knowledge of God. For the Lord giveth wisdom; out of His mouth cometh knowledge and understanding." Proverbs 2:3-6.
SECTION 3. MAKING THE MOST OF SEEDS AND SEEDLINGS
In the heart of a seed, very deep so deep,
A dear little plant lay fast asleep,
"Wake up!" said the sunshine, "and creep to the light"
"Wake up!" said the voice of the raindrops bright,
The little plant heard and he rose to see
What a wonderful world God made for you and me!
-V. B. S. Manual (1992)-
Seeds just might be available for the bamboo species of interest to you. Literature on bamboo flowering in your area would be most useful. Get in contact with the Forestry Department and you may be able to contact people who have many observations on times (or months) of flowering of particular species of bamboo.
Bamboo species have different types of inflorescences. Gigantochloa levis have long inflorescences, which looks like a "curtain" around the culm (Fig. 3.1). Schizostachyum lumampao has short inflorescences that are near terminally located. When we saw gregarious flowering of Bambusa vulgaris and G. levis even the old stumps had flowers. You will have to adjust on how to proceed with each collecting situation.
A. Collecting seeds and seedlings
First, let us go through some dos and don’ts.
1. Plan the collection trip. You must have an idea where flowering clumps of bamboo have been sighted. It is helpful to have a survey trip.
What should you bring? The following are the things (Fig. 3.2) we found convenient to have on a collection trip:
b. Large net which we can lay on the ground to catch inflorescences
c. Pruning shears
d. "Bolo" (similar to machete) or scythe
e. Rope, preferably nylon (long enough to lasso bamboo branches or support a collector, about 20-25 m long)
Note: At times, the flowering clump may be located along the river or creekside. Under these conditions, it will be difficult to position the net for the collection. Once, our driver tied a rope to the bridge. Then he used the rope to swing down to the flowering culm so that he could reach the inflorescences to get us some samples.
Fine nylon net bags (for the seeds and florets and for sheaths and leaves)
Note: You may use paper, cloth or plastic bags to hold unprocessed flowers and seeds. Protect the seeds from increased humidity in these bags by rolling down their sides during the collection trip and travel back to the laboratory. Protect from heat by putting bags in shade. Do not put them in a parked vehicle because temperatures may rise above 40oC. Excessive prolonged heat could drastically affect seed viability.
g. Stick broom for sweeping fallen inflorescences/ florets
Permanent markers and shipping tags
Jacket or long-sleeved shirt which you can button up and a cap or hat
Note: This protective gear can save you from scratches and itching.
Medicine kit (insect creams, Band-Aids, etc.)
When you locate a flowering clump, seek the owner of the land or its caretaker.
Record his name, address, date and interview notes to include when flowering was first observed and tentative identification of the species.
Make a location map showing the flowering clump in relation to other structures, trees or landmarks.
Collect culm sheaths. These will help you identify the bamboo. Culm sheaths of different bamboos have distinct features (Fig. 3.3). Put all the materials from one clump together.
You may collect seeds following one or more techniques or their combinations (Pukittayacamee, 1996). These methods include (a) collecting from seeds that had fallen to the ground naturally, (b) collecting by shaking the culms and (c) collecting from the felled culms. Aside from these techniques and depending on fertility of the bamboo species, you may also cut inflorescence from unfelled culms
Of the different methods, the least preferred is to cut down the flowering culm. However, some situations warrant the use of this method. For example, some communities have an aversion to flowering bamboo because this signals bad luck or hard times to them (Fig. 3.4). The flowering bamboo will soon be cut down anyway.
Of the various methods of collection, culm-shaking yielded seeds with the highest percent germination, followed by culm branch cutting in Bambusa bambos while germination was closely similar for ground collection and culm-shaking for Thyrsostachys siamensis (Pukittayacamee, 1996). We also recommend this method for species with low fertility such as Gigantochloa levis.
Collecting from seeds which have fallen on the ground naturally
You may opt for this technique when the flowering clump is near a community and you can arrange with a possible collector. The technique is most useful if the clump is accessible and you can return to collect seeds every 3-5 days. However, daily collection would minimize the exposure of seeds to soil-borne pests.
Clear the area beneath the flowering clump.
Lay a large fine net underneath the flowering clump. A plastic sheet or canvas can be spread late in the afternoon each day to avoid morning dew and condensation that would moisten the seeds and make them more susceptible to fungal infection (Seethalakshmi and Soman, 1992 and Pukittayacamee, 1996).
Note: If you do not have a net, canvas or sheets of plastic or woven mats, particularly for unplanned collections, sweep the area underneath the clump thoroughly with a stick broom. Collect fallen inflorescences and seeds.
Protect the collection area from rats, birds and other animals that eat the seed.
Label the bags. Include tentative identification of clump source, area of location, owner and date collected.
Collecting by shaking the culms
Clear the area of tall grass or small shrubs (if permitted) with your "bolo"/scythe.
Spread the net underneath the flowering clump. Consider the direction of the wind when positioning the net (Fig. 3.5).
Tie the rope on the culm so that you can tug on the rope to shake the culm. You may climb up the culm, jump on it or shake other stems and branches (Fig. 3.6).
Collect the florets that fall into the net. Transfer the florets into net bags.
Label the bags. Include tentative identification of clump source, area and, whenever possible, the owner of the land. If more than one mat is flowering within the same area, label each mat as individuals.
Collecting seed-bearing inflorescence from felled and unfelled culms
Inspect the culm for relative fertility. Highly fertile bamboos, e.g. S. lima, S. lumampao, have many seeds in clumped inflorescence.
Collect inflorescence that has turned brown (due to maturity). Pick mature seeds or cut inflorescence from low-lying unfelled culms with a pruning shears (Fig. 3.7).
Note: If bamboo clumps are easily accessible, collect mature seeds only. Leave immature seeds to develop further and inspect after a week or so for another collection.
Return to collect more inflorescence as they mature.
Transport inflorescence in a paper or wrapped in newspapers, within net bags.
Put all net bags in a polystyrene box to ensure safety during transport.
Handling after harvest
Remember that drying and cleaning affect the quality of your seed lots since seed moisture at harvest may vary with species, e.g. 16% for T. siamensis to 21% for B. tulda. You will have to reduce moisture content.
If you collect seeds during the rainy season and if the seeds remain wet for a sufficient time, they may germinate before you even use them. So, dry them. You may need to lay the seeds on lots of newspapers or other absorbent material to absorb excess moisture (Fig 3..
Air dry inflorescence or seeds as soon as possible. You may hasten air drying with a fan or hair dryer during the trip.
It is also worthwhile to investigate if seeds had fallen earlier around the flowering clump. These seedlings can be gently lifted and potted in the nursery. You may want to use them to improve methodologies using juvenile tissues, including nodes and shoot tips.
Locate seedlings beneath the canopy of flowering bamboo, particularly near sources of water.
Use a stick or other alternative to lift the roots and soil of the seedling.
Put some moist soil from the vicinity of the seedling in a plastic bag or alternative container, which will help keep the humidity around the plant during the trip. Moisten soil if it needs a bit of water.
Put the seedlings with some leaf mold on the soil and ensure that these are protected from desiccation.
Place these seedlings in the shade until all collection activities have been completed. You may put them in the vehicle when it is time to go.
B. Processing of the inflorescences for seeds
You need to process the collected inflorescence and florets for seed. The technique for processing will depend largely on the characteristics of the flowers. The flowers may vary, depending on the bamboo species. Glumes may be absent, loosely enveloping the seed or closely clinging to the seed. Seed-bearing florets and seeds, before and after processing, are shown for G. levis, S. lumampao and D. strictus (Fig 3.9). Processing would mean selection of florets with seed and cleaning seeds.
Winnow the florets to separate chaff from the filled florets. Most of the empty florets will separate from those with seed during winnowing.
Press each floret. Florets with seed are hard to the touch. If the seed is immature, the floret will be more malleable to the touch.
Note: We have tried to improve on the processing for G. levis using seed processing equipment but to no avail. For other species without glumes, postharvest equipment may make work simpler.
3. Extract the seed from the glumes manually.
Sort the seeds to mature (hard dough stage), less mature (soft dough stage) or immature (milk stage).
Note: The seeds can also be differentiated by the flotation method. Put some seeds in water. Those that float are most likely immature and at the milk stage. Those that sink are mature seeds. Inspect the seeds and differentiate each batch based on color and "feel". Use these observations in subsequent batches to sort seeds. For G. levis, the immature seeds are green while the mature seeds are brown. For S. lumampao, immature seeds are purplish-green, mature seeds are brown.
Discard seeds that are at the milk stage.
Store mature seeds.
Germinate embryos from less mature seeds.
Storage of seeds
You may need to store seeds since their availability is very limited. Bamboo seeds are orthodox. They can withstand desiccation and storage.
2. Test each seed batch for viability and percentage moisture content if you want to store the seeds for several months.
Note: If your seeds are too few, you may not want to waste any of the seeds by using them for a viability test. You will have to rely on visual appraisal of the embryos. Healthy embryos are white and plump. With prolonged storage, the embryo may look shriveled and on the creamy side. Not all of these will germinate, but some will.
3. You may use a desiccant to dry seeds to 5-6% MC. You may also sun dry or kiln dry the seeds at 40-50oC for 3-6 hrs (Pukittayacamee, 1996).
Line a plastic bag or plastic/glass bottle with an absorbent material such as cotton or paper.
Put in the seeds and seal the container.
Label properly. Include species, collection data, percentage viability, and date of storage.
Store in a refrigerator (about 15oC) for 18 months. You can prolong storage life with storage at even lower temperatures (2oC).
Testing for Seed Viability (Taken from Pukittayacamee, 1996)
Deglume seed to get the embryo.
Soak seeds in 1% H2O2 solution (100 ml/50 seeds) and incubate overnight in the dark at room temperature. Change the solutions daily for 3 days.
Observe for radicle protrusion. Renew the solution for another 3 days if the radicle has not yet protruded.
Evaluate radicle protrusion. Viable seed would have radicles longer than 5 mm.
D. Aseptic germination
In vitro germinated seedlings represent opportunities for a micropropagator. They serve as sources of nodes, shoots and rhizomes for other micropropagation techniques.
Disinfection is successful if aseptic materials are established from the tissues of interest. Seeds of different bamboo species vary in shape and characteristics (Fig. 3.9). Although seeds are generally amenable to disinfection, the harshness and duration of treatment are influenced by the characteristics of the seed. Some seeds have very smooth and tough surfaces; these are easily disinfected. Others have fine hairs and a thin skin. These characteristics make them more difficult to disinfect. Contaminants may not be easily disinfected since air bubbles may be trapped in the tufts and the thin skin makes the seed less resistant to the disinfecting solutions.
With variations among species, it is best to look for literature on the species of interest to you or to choose a procedure for a species with seed characteristics like your species. Table 3.1 summarizes some disinfection procedures for seeds of some bamboo species. Whenever data is available, the characteristics of the seeds are also indicated.
The following disinfection protocol works for D. strictus and G. levis. Seed batches of G. levis stored for 7-8 weeks and used for embryo culture showed 79-84% germination.
a. Obtain an appropriate quantity of seeds from storage.
b. Wrap the seeds loosely in a piece of gauze, fine net, nylon stocking or similar material.
c. Tie the "seed bag" to the water tap (faucet) and leave the water running for two hours.
Note: If your water source warms up with time, you need to modify the system. Collect water in a container (e.g. plastic jug, clay water container) with a tap. Allow the water to cool. Wash your seeds.
d. Transfer the seed bag to a flask or appropriate vessel, add pure commercial bleach and cover with a piece of foil. Shake the solution or stir the seeds with a magnetic bar on a magnetic stirrer for fifteen minutes.
e. Transfer the flask to a clean air bench or a sterile inoculation box.
Wash the seeds thoroughly with sterilized (distilled or tap) water to remove the bleach.
Table 3.1. Disinfection procedures for seeds of bamboo species.
Keep the dehusked seeds in running water for 1 hr, then dip in 5% Teepol for 5 min.; wash in running tap water and distilled water; wash seeds with rectified spirit for few seconds; sterilize with 0.1% HgCl2 for 15 min.
Wash seeds with 2% Teepol solution on a magnetic stirrer for 5 min.; wash in running tap water for 15-20 min.; rinse in distilled water; immerse in chlorine water (saturated chlorine water diluted 5 times with distilled water); wash thoroughly in sterile distilled water.
Wash the dehusked seeds with 2% Teepol solution on a magnetic stirrer; wash in running tap water for 15-20 min.; rinse in distilled water; immerse in chlorine water for 5 min. (saturated chlorine water diluted 5 times with distilled water); wash thoroughly in sterile distilled water.
Surface-sterilize with 75% ethanol for 1 min.; dip into 10% sodium hypochlorite for 15 min. and, then rinse thoroughly in sterile distilled water.
Niraula and Bhandary, 1987
Rao et al., 1987
Rao et al., 1985
Otatea acuminata O. aztecorum
Wash for 10 min. in water containing a few drops of detergent; rinse in distilled water; dip in 70% ethanol for 1 min.; immerse for 15 min. in 30% commercial bleach (1.6% sodium hypochlorite final concentration) and rinse 3 times in sterile water. Final rinse with sterile water at a pH of 3.5 (achieved by addition of HCl).
Woods et al., 1992
Sterilize with 75% ethanol for 1 min.; dip into 2% sodium hypochlorite for 10 min.; rinse thoroughly in autoclaved distilled water.
Yeh and Chang, 1987
54 species from 15 genera*
Spray with 70% ethanol; surface-sterilize for 30 min. in 1% sodium hypochlorite; wash 3 times in sterile water.
Prutpongse and Gavinlertvatana, 1992
*Arundinarea pusila, A. superecta, Atatea aztecorum, Bambusa srundinacea, B. flexuosa, B. glaucescens, B. gracilis, B. humilis, B. longispiculata, B.multiplex (variegata), B. nigra , B. multiplex, B. oldhamii, B. polymorpha, B. ventricosa, B. ventricosa (variegata), B. vulgaris, B. cv. Dam Khan, B. cv. Bong ban, B. Bong Naew, Cephalostachyum pergracile, Dendrocalamus asper, D. giganteus, D. hamiltonii, D. Bong Kaiy, D. latiflorus, D. membranaceus, D. nutans, D. strictus, Dinochloa scandens, Gigantochloa albociliata, G. apus, G. auricurata, G. compresa, G. densa, G. hasskarliana, G. hossuesii, Hibanobambusa triangullans, Helocatamus compactiflorus, Oxytenanthera albociliata, Phyllostachys aurea, P. bambusoides, P. gramineus, P. nigra f. megurochiku, P. pubescens, P. sulphurea, P. viridis, P. iaponica, Sasa fortunei, Sasaella sumekoana, Schizostachyum aciculare, Sch. brachycladum, Sch. zollingeri, Semiarundinaria fastuosa, and Thyrsostachys oliveri
2. Excision and inoculation of embryos
Place the sterile stainless steel dishes lined with sterile paper, scalpels, forceps, alcohol lamp, a couplin jar with 95% ethyl alcohol, bottles with sterile water and soapy solution (Fig. 3.10), in the sterile working area. A dissecting microscope is also helpful.
Note: Kitchenware steel plates may be replaced with petri dishes.
Open the flask with caution to maintain sterility of seed.
Transfer some seeds onto the sterile paper on petri dishes or steel plate with a pair of sterile forceps.
Hold the seed aseptically with the forceps and make a slit on the seed coat over the embryo with the tip of the scalpel blade.
Excise the embryo from the rest of the seed tissues. Use a dissecting microscope to make your work easier.
Inspect the embryo.
Inoculate the embryo onto the culture medium.
Note: (a) In literature, others use the intact seed. We have also used the embryonal end, without the endosperm. However, the bigger the explant, the higher the risk of contamination. With many grooves in the bamboo seed, it is best to reduce the size of the explant to the essentials. For callus and somatic embryogenesis, clean the embryo of other tissues. (b) A culture medium recommended for seed germination consists of half-strength MS macronutrients and micronutrients, full strength MS vitamins and iron and 20 g/l sucrose, pH 5.7.
h. Position of the embryo on the culture medium embryo-side up and away from the culture medium (Fig. 3.11).
Note: The components of the culture medium vary depending on the route for multiplication. See Table 3.2. Routes of micropropagation and culture media for seed-based tissue cultures of B. arundinacea and D. strictus.
i. Maintain the cultures under 16-hour photoperiod, 42 uE m-1 sec-1 in an air-conditioned room at 22-27 oC.
j. Inspect for bacterial and fungal contamination. Discard contaminated cultures.
k. Observe for germination 4 to 8 days after inoculation.
Table 3.2. Routes of micropropagation and culture media for seed-based tissue cultures of B. arundinacea and D. strictus.
In vitro germination
a. B. arundinacea
b. D. strictus
Whites + 2% sucrose
Nadgir et al, 1984
Multiple shoot formation
a. B. arundinacea
b. D. strictus
Medium + 1 mg/L NAA + 4 mg/L 6-BAP
Vasana et al, 1985
a. B. arundinacea
b. D. strictus
N6 + 7 mg/L 2,4-D
B5 (0.5x) + vitamins + 30 uM 2,4-D + 2% sucrose + 0.8% agar, pH5.8
Metha et al, 1982
Rao et al, 1987
Note: You will first observe swelling of the embryonal end, a change in color to more opaque to creamy, radicle protrusion and lastly shoot growth.
You are successful! Your seedlings are slowly putting on more leaves and nodes! (Fig. 3.12). You are now in business.
E. Multiple shoot formation from nodes of aseptic seedlings
Using aseptically germinated seedlings as sources of node cuttings can amplify your propagation scheme. Seedlings would have the advantage of the full utilization of its biological life span.
Inspect cultures of germinated seedlings. In a month or so after seed/embryo establishment, sort the seedlings according to vigor.
Note: If you had opted to use the culture medium for multiple shoot formation right at germination, shoot growth will be slower.
Establish your coding system so that you can sort out the sister lines from one embryo and from one clump source. This will help us release plants from several genotypes to supply requests of communities responsibly.
Prepare appropriate culture media for multiple shoot formation.
Important! The culture medium for multiple shoot regeneration in juvenile sources of nodes consists of MS at full strength, 30 g/l sucrose, 1 mg/L NAA,and 4 mg/L BAP, pH 5.7.
Using aseptic techniques and working in a clean air cabinet cut the stems near the base of the plant with a pair of curved scissors (Fig. 3.13). Leave some nodes at the base to keep the remainder of the seedling productive.
Draw out the cut stems (upper part) and place them on a stainless steel dish.
Prepare node cuttings. Cut shorter stub on the upper part of the node cutting to differentiate polarity and favor early bud break.
Inspect node cuttings for lateral buds by pulling on the leaf sheath encasing the node area.
Note: Some cuttings may have blind nodes (i.e. lateral buds are not observed). Discard these nodes.
Inoculate cuttings unto a culture medium for multiple shoot formation.
Maintain the cultures under 16 hours photoperiod, 42-uE m-1 sec-1 in an air-conditioned room at 22 - 27 oC.
New stems developed within 2 to 4 weeks.
You may repeat the whole cycle of multiplication.
Note: If your species does not form multiple shoots on the suggested culture medium, try these published media. Table 3.3 summarizes literature on multiple shoot formation using seed and seedlings of various bamboo species. If none of these works, experiment!
With the stems cut short to the base, it is unnecessary to throw away the remaining basal tissues. The rhizome developed during the germination is best used as planting material. You may extend its usefulness by adding fresh medium and waiting for new shoots. You may also trim the roots near the rhizome and transfer the whole shoot to a new culture medium. Alternatively, you can propagate them by micro-division.
Trim roots with close to the rhizome with a pair of curved scissors
Take out the shoot from the culture vessel and transfer to a sterile paper.
Cut it along the rhizome to get small shoot clusters.
Inoculate to fresh medium.
Repeat the whole cycle of multiplication.
G. Calli and somatic embryogenesis from embryo tissues
Embryos are easier to induce to callus and to form somatic embryoids. This approach is potentially more productive within a shorter period of culture than multiple shoot formation. However, the risk of getting somatic variations is potentially higher among plants that were regenerated from calli/somatic embryoids than from multiple shoot formation.
Use procedures for aseptic germination. Follow disinfection procedures. You may use intact seeds (Rao and Rao, 1985) or excised embryos following our procedures adapted from institute procedures for wheat tissue culture. The procedures described below worked for G. levis, D.strictus, and B. bambos and are based on Zamora and Gruezo (1989).
Disinfect the seeds to be used for embryo culture.
Use aseptic techniques.
Transfer to sterile petri plates lined with paper to absorb excess moisture.
Hold the seed aseptically with the forceps and make a slit on the seed coat over the embryo with the tip of the scalpel blade.
Excise the embryo from the rest of the seed tissues. Use a dissecting microscope to make your work easier.
Inspect which is the scutellum-side of the embryo.
Inoculate the embryo with scutellum-side up onto a solid culture medium for callus induction. The embryo-side should face the culture medium.
Important! The culture medium we found useful for inducing and propagating calli/somatic embryos consists of full-strength MS, 20 g/L sucrose, 2 mg/L 2,4-D, 5.0 g/l agar, pH 5.7.
Note: Table 3.4 summarizes the culture media for callusing and somatic embryogenesis in various bamboo species.
Maintain the cultures in eight hr-diffused lights in an air-conditioned room at 22-27 oC.
Note: Cooler temperatures are very favorable for callus induction and propagation.
Inspect for bacterial and fungal contamination. Discard contaminated cultures.
2. Propagation of Calli/Somatic Embryoids
Inspect callus growth after 4 weeks inoculation.
Sort callus cultures into compact, loose-type or combination (Fig. 3.14). Discard the cultures showing only loose-type calli.
Note: (a) If callus is still small, subculture the whole callus to fresh culture medium. (b) The base medium and the growth regulators are important for the type and extent of callus growth (Fig. 3.15).
If compact callus is big enough, segregate it from the loose-type. Subculture onto freshly prepared callus medium.
Note: (a) It generally takes two subcultures (a month apart) before the callus sufficiently enlarges for you to decipher the presence of compact calli.
(b) Embryogenic compact calli give rise to somatic embryoids.
Propagate the compact-type calli/somatic embryoids by subculturing every 2 weeks to fresh culture medium. Break up the proliferations along weak points.
Note: (a) Do not break up calli forcibly with a scalpel. Cutting up will cause the calli to turn brown die. (b) Compact calli the size of an eraser head of a Mongol pencil will yield callus more than four times its size in 4 weeks (Fig. 3.16).
Inspect for any signs of bacterial contamination. Discard contaminated cultures.
Note: Any clouding of the culture medium at the immediate vicinity of the calli makes the culture suspect.
Strategize the propagation of calli/somatic embryoids and regeneration of plants.
Note: When you observe albino callous or plants transfer all calli stock belonging to this batch to the regeneration medium.
g. Initiate a fresh batch of seeds every six months to ensure a continuous stock of embryogenic calli capable of regenerating green plants.
3. Plant Regeneration
a. When you have built up the stock of e-calli/somatic embryoid stock, subculture some stock to the culture medium for plant regeneration and to fresh 2,4-D culture medium to propagate the e-calli/somatic embryoid stock.
Important! The culture medium we found useful for plant regeneration consists of full-strength MS macronutrients, vitamins and iron, half-strength MS miconutrients, 20 g/l sucrose, 150 ml/l coconut water (from young green nuts), 0.1 g/l myo-inositol, 5.0 g/l agar, pH 5.7.
b. Maintain the cultures under 16 hours photoperiod, 42 uEm-1sec-1 in an air-conditioned room at 22 - 27 oC.
c. You will observe the greening up of the compact calli and soon you will see shoot points that develop which will form plantlets within 4 to 8 weeks (Fig. 3.17).
You may use the plants for multiple shoot formation and micro-division if you still need more plants.
H. Wildings or Nursery-Grown Seedlings
Remember the wildlings you collected? These can be cultured. However, the major obstacle is decontamination. We get about 55% clean cultures from greenhouse-grown materials. This could have been improved by improving on nursery culture.
Briefly, our procedures are as follows:
Harvest shoots with at least seven leaves.
Note: Each leaf corresponds to a node so that by counting the leaves, you can approximate the number of nodes.
Cut off the top 3 leaves, including the extended spindle leaf. Discard.
Scrub the remaining shoots under running tap water. Use cotton wad dipped in soapy water. Rinse thoroughly.
Cut the stem into cuttings with one to two nodes, depending on closeness of internodes.
Put the segments in a flask.
Soak the segments in soapy water for 10 min. Decant solution.
Add bleach to flask, soak segments for 15 min. Decant the disinfectant, and rinse with sterile tap water.
Transfer segments to 70% ethyl alcohol. Decant solution after 1-2 seconds.
Add 0.12% calcium hypochlorite (CaOCl2) and soak segments for 10 minutes. Decant bleach.
Add streptomycin (1 g/L) solution and soak segments for 10 min.
Put the segments onto a sterile petri dish lined with sterile paper.
Cut along the base of the sheath along the node. Remove the sheath.
Trim the internodes below and above the bud. Make a shorter stub above the node.
Inoculate onto the culture medium.
Note: The culture medium varies with the propagation methodology. Prepare appropriate medium.
Observe new shoot growth after three to four weeks (Fig. 3.18).
I. Invitro Rooting
Prepare appropriate culture media for in vitro rooting.
Using aseptic techniques and working in a clean air cabinet cut the stems near the base of the plant with a pair of curved scissors. Leave some nodes at the base to keep the remainder of the seedling productive.
Draw out the cut stems (upper part) and place them on a stainless steel dish.
Inoculate shoots or cuttings unto a culture medium for rooting.
Maintain the cultures under 16 hours photoperiod, 42 uE m-1 sec-1 in an air-conditioned room at 22 - 27 oC.
Observe roots after 2 to 4 weeks.
Acclimatize them for potting out.
Thought for the Section:
Hearken; behold, there went out a sower to sow;
And it came to pass, as he sowed, some fell by the way side, and the fowls of the air came and devoured it up.
And some fell on stony ground, where it had not much earth; and immediately it sprang up, because it had no depth of earth;
But when the sun was up, it was scorched; and because it had no root, it withered away,
And some fell among thorns, and the thorns grew up, and choked it, and it yielded no fruit.
And the other fell on good ground, and did yield fruit that sprang up and increased; and brought forth, some thirty, and some sixty, and some a hundred. Mark 4:3-8.
We hope the seed you collected will all fall under the last category. For bamboo, seed is precious. "Limited quantity" is not necessarily a hindrance to propagation with tissue culture because we can multiply whatever seed is available by many techniques in vitro instead of waiting for just one plant to arise from one seed. As the word in Mark 4:3-8 says that if seed falls on good ground, and is taken care of, it will increase.
SECTION 4. I WANNA BE JUST LIKE YOU!
"When I grow up, I will be just like you".
If you grow bamboo, you may observe that their performance in terms of growth rate, yield, culm diameter, fiber strength or other characteristics vary. If you have a better plant, you may prefer propagating this selection to the others. You can increase this clone by macropropagation and by micropropagation. We expect the plants propagated by micropropagation techniques to be identical to the source of the initial plant material. They are somaclones or sister lines from somatic tissues.
There are several candidate sources of initial tissues for micropropagation. You may culture small bits of tissues from the soft internode tissues in extended and unextended branches. If you look at the bamboo during the onset of the rainy season, there will be many new branches. However, from each branch, the number of sections you can get is rather limited compared to the fast growing ground corm. What is a ground corm? Are you familiar with the less technical name "bamboo shoot"? When the new shoot is developing and fast elongating, you can get many tissues from the soft internode and node areas for tissue culture work. Common to these tissues in the branches and ground corms are the highly active and dividing groups of cells that can be induced to further divide in culture to form calli.
Aside from these tissues, nodes from unextended and extended branches as well as unenlarged buds are candidate materials. There are differentiated buds, which can serve as the source of new growths by multiple shoot formation. However, the requirements for culturing nodes from mature clumps, whether non-flowering of flowering, are different from nodes from seedlings. Researches using tissues and nodes from mature clumps are limited compared to seed and seedling tissues (Saxena and Dhawan, 1994; Zamora, 1994).
The following protocols were developed in the Institute of Plant Breeding of the College of Agriculture, University of the Philippines Los Baños, Philippines.
I. GROUND CORMS
A. Collecting ground corms
Let us start with some dos and don’ts.
Plan the collection trip. Bring what you need because you might end up not being able to excavate the ground corm. What should you bring? The following is a list of things we found convenient to have to collect ground corms:
a. Sharp pruning shears
b. Desuckering bar, "bolo" or machete
c. Net bags (heavy duty) and newspapers for wrapping
d. Clean water to wet newspapers
e. Markers and shipping tags
f. Polystyrene box, if collection area is far from the laboratory
g. Jacket or long sleeved shirt which you can button up
h. Cap or hat, boots and gloves (or plastic bag)
Visit the clumps two weeks well in the rainy season and inspect if new shoots have come out. Cover with some decomposing leaves or litter fall to protect your discovery!
Note: Guard your mats when two to three weeks of rain has fallen! By this time, the
bamboo would have new shoots and, boy, are they tasty at this time!
Return after a few days to about a week. Harvest when the shoots are about 1.5 to 2 feet high from ground level.
Note: Growth rates of shoots vary with species so familiarize yourself with the species of interest! If you missed the preferred height of the bamboo shoot, make do with your harvest. Your cultures will be restricted to the younger nodes.
When you return, dress for the occasion, with long sleeves, a cap and boots. Be prepared in case it rains.
Note: Some bamboos have many trichomes on them that can be a nuisance to you.
Remove the litter cover to expose the shoot and excavate around the base of the new shoot.
Extract a new shoot with a "bolo" or desuckering bar (Fig. 4.1).
Note: Exercise great care during extraction because the new shoot is tender. Avoid shaking movements that tend to crack the base and open wounds. Make clean cuts. Avoid bruising the sides of the shoots.
Once separated from the rhizome, gently lift the shoot to flat ground and clean the base of adhering soil.
Dampen the newspapers and lay the shoot on them. Wrap the shoot with damp newspaper.
Label. Include species, date/area of collection, and if taken from someone’s backyard, the name of the owner.
Transport in a polystyrene box to prevent cooking or dehydrating the corm.
B. Handling of corms for culture (Fig. 4.2)
In the laboratory, wash the shoots thoroughly in running water.
Trim off the ligules (small leafy structure at the tip) from the leaf sheaths with the pruning shears.
Chop off the very hard tissues in the ground corm.
Remove the outermost leaf sheaths and all loosely fitted sheaths.
Scrub the remaining surfaces with a scrubbing pad or soft brush with soapy water to remove dirt and possibly pests such as insect eggs, aphids and mites.
Rinse with clean water. Air dry.
C. Storage of corms
If you come in from your trip on a weekend and dead-tired from the trip, store the corms. Anyway, who wants to work on a Sunday! They will have to be stored until the next workday!
1. Remove the damp newspapers.
2. Wash the shoots thoroughly in soapy water dry with newspapers and when air-dried, re-wrap in a dry newspaper.
3. Store in the refrigerator.
4. Remember to use them for culture within a week.
Note: The longer you keep them in the refrigerator, the poorer will be your results. In other words, don’t procrastinate! It is best to use them freshly collected.
D. Disinfection of corms (Fig 4.3)
Wrap the shoots in a thin layer of cotton.
Transfer to a big plastic bag.
Wet the entire surface with pure bleach and let this soak for 60 minutes.
Transfer the bag containing the ground corm to the clean air bench.
Remove shoots from the bleach by peeling away the cotton layer.
Transfer to a small tray that will hold the shoot and the water to be used for rinsing.
Hold the shoot by the tip, position the shoot perpendicular to the tray and rinse with sterile water.
Transfer the shoot to a dry tray.
E. Preparation and inoculation of explants (Fig. 4.4)
Remove the bottommost sheath by making an incisive slit at the base of the sheath and pull the sheath away from the shoot to expose the internode and node.
Cut the internode tissues just above the nodal ring. This will be about 3 - 4 mm thick.
Put the layer in petri dish lined with paper and wrap the dish with a piece of paper to minimize exposure to light. From our experiences, these tissues are very susceptible to browning when left exposed to light. The browning is irreversible.
Continue processing the shoot and extracting internode layers until you have finished nearly all layers.
Discard sections less than 2 cm wide.
From each layer, make a strip 3-4 mm wide that includes the epidermis and inner tissues.
From the strip, cut perpendicular to the epidermis so that you will have 3-4 mm cubes. Each cube should have a piece of the epidermis. These tissues are more responsive for callusing.
Inoculate each explant cube onto the solid culture media consisting of MS, 40 g/L sugar, 1 ppm 2,4-D and 1 ppm BAP, 5 g/L agar (HiMedia), pH 5.7.
Important! If there are protocols reported for your bamboo species, first try these protocols. If your cultures do not form callus, try other media summarized in Table 4.1. It will be a good idea to try several culture media at the onset of experimentation.
Note: See appendices for the preparation of culture media and aseptic techniques. Depending on the width of the vessel used, the number of explants may be more than one. In vessels 18-20 mm diameter (like test tubes), inoculate one explant. In screw-capped bottles (4.5 cm outer diameter), you may inoculate up to 5 pieces.
9. To minimize browning, you may opt to extract the internode layer and immediately process this to get the explant cubes for inoculation. However, you are stuck with a shoot in the laminar flow cabinet, which is not very convenient.
10. Place the cultures in the dark immediately after inoculate to control browning.
Note: You may put cultures in a cabinet, in paper bags or wrap your vessels in carbon paper. Cultures are very susceptible to heat and require cool temperatures from 20 - 25 oC. The lower setting was attained using a growth chamber. However, in the absence of a growth chamber, cooling was achieved with the use of an airconditioner. Temperature ranged from 23-25 oC. Expect some growth (either enlarging, callusing or both) within a month.
F. Subculture and selection of calli (Fig. 4.5)
1. Inspect the explants two weeks after culture.
2. Transfer all explants to fresh media every two weeks.
At the end of the second month (after three transfers), sort out cultures that have formed callus.
Discard brown and unresponsive cultures.
Transfer the remaining cultures (those with callus growth) to fresh media and incubate in darkness under recommended temperatures.
Inspect after a month and select cultures with compact type-calli.
7. Discard the rest of the cultures, including the loose-type calli.
G. Propagation of compact-type calli
Transfer the compact calli to fresh medium containing BA and 2,4-D monthly.
From the compact-type calli, you will recover somatic embryos, which may be propagated by regular transfers to fresh 2,4-D medium.
Note: Avoid making cuts or injuries on the cultures that may induce browning.
H. Shoot and shoot-like structures and plant regeneration (Fig. 4.6)
Observe shoots and shoot-like structures that will form from the compact-type calli even in the presence of 2,4-D or BAP in the medium.
Transfer the cultures bearing shoots and shoot-like structures to semi-solid medium (one-fourth strength MS macronutrients and micronutrients) with 5 ppm NAA to recover plants. Check Table 4.1 for other culture media for germination of somatic embryoids/rooting of shoots.
At this point, you may micropropagate by multiple shoot formation to maximize the plantlets.
Each plant can be used as the initial plant source of nodes for multiple shoot formation.
II. UNEXTENDED AND EXTENDED BRANCHES
Collecting branches (Fig. 4.7)
Prepare for a collection at the onset of the rainy season
Prepare the necessary equipment and paraphernalia for collection, including the culture medium to be used when you return to the laboratory.
a. Sharp pruning shears
b. Plastic bags/pail, net bags (heavy duty) and newspapers for wrapping
c. Clean water to wet newspapers
d. Markers and shipping tags
e. Polystyrene box, if collection area is far from the laboratory
f. Jacket or long sleeved shirt which you can button up
g. Cap or hat, gloves and boots
Inspect the clumps for extended and unextended branches.
Note: Avoid collecting branches with mealy bugs or aphids. They make decontamination difficult.
Cut these branches with a pruning shears and put them in plastic bags or pail with water.
Note: The branches dry up easily so keep the environment most favorable for them. You may wrap them in moist newspapers and transport them within a plastic bag or net bag, depending on travel time.
Bring the branches to the laboratory.
B1. Preparation of nodes and disinfection (Fig. 4.
There are other protocols for preparation and disinfection based on literatures that are summarized in Table 4.2. The following are the procedures presently used by the authors.
Cut branches into sections. Each section should contain a node. Discard the upper stem bearing the spindle and two-three expanded leaves.
Trim the section 0.5-cm below the node and 2 cm from the node to the tip.
Select sections with tight enclosing sheaths.
With a pad of cotton dipped in 95 % alcohol, wipe each nodal section clean to remove the trichomes.
Note: You can use 70% ethyl alcohol but it is easier to wipe of trichomes with 95% alcohol.
Soak in soapy sterile tap water for 30 minutes, change the soapy water and soak the nodal sections again for 30 minutes. Use a magnetic stirrer. Decant the soapy solution.
Soak in antibiotic (1 g/l streptomycin) for 60 minutes. Use a magnetic stirrer. Decant the antibiotic solution.
Soak in commercial bleach (5.25% a.i.) for 60 minutes. Use a magnetic stirrer. Decant the bleach.
Rinse thrice with sterile water.
Transfer the sections onto a sterile steel plate lined with sterile paper.
Make a cut along the base of the leaf sheath and remove the enclosing sheath.
Inspect for buds. If the section is blind, discard it.
Trim stem 1-2 mm above the bud and 3-5 mm below the node.
Note: Use the bud section for multiple shoot formation and the soft internode tissues above the bud section for establishing callus cultures.
Section the soft internode tissues above the bud section into 2-2.5 mm thick slices.
B2. Preparation of unextended branches and disinfection (Fig. 4.9)
1. In the laboratory, wash the unextended branches thoroughly in running water.
2. Trim off the ligules from the leaf sheaths and the hard basal portion with the pruning shears.
3. Wipe the remaining surfaces with a cotton pad wet with 95% ethyl alcohol.
4. Wrap the shoots in a thin layer of cotton.
5. Wet the entire surface with pure bleach. Cover with aluminum foil and let this soak for 60 minutes.
6. Transfer the disinfected unextended branches to the clean air bench.
7. Remove shoots from the bleach by removing the aluminum foil and peeling away the cotton layer.
8. Put each branch in a flask and rinse thoroughly with sterile water (tap or distilled).
9. Take out unextended branches and peel off all sheaths until all soft tissues are exposed.
10. Section the soft tissues (about 3-4 mm thick slices) and inoculate onto a c
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