Sunday, March 05, 2006

Strategies in Clonal Mass Propagation of Orchids

Strategies in Clonal Mass Propagation of Orchids

Written by [Philippine Orchid Review] Norberto R. Bautista
Friday, 01 February 2002
Orchids are valued for their exotically beautiful flowers. They are economically important crops for they are used in cut flower business, while some are valued as a potted plant collected by numerous orchid collectors  hobbyist around the world. With a large demand, orchids can be reproduced by the millions and each seedling is an exact duplicate of its parent.
These plants are propagated either by the conventional and the non-conventional means. Conventional means of clonal propagation means reproducing orchids asexually through divisions of pseudobulbs, top-cutting in monopodial orchids, or induction of keikes (anak) through the use of plant growth regulators or subject to stress. This method is used by the hobbyist in reproducing their collections in their gardens. Unfortunately, this method is slow (produces about 2-3 plants a year) and the plant is in the risk of being infected with the viruses.
Non-conventional means of propagation involves reproduction through plant tissue culture. Unfortunately, this method needs a sterile laboratory wherein all manipulations can be done and the plant tissue to be use is grown in an artificial culture medium under artificial lightning and temperature. It is capital, technological and labor intensive, but if done right, produces millions identical progenies from a single mother in just 1 year!
Although plant tissue culture is the fastest way of cloning orchids, sexual propagation (seed culture) which could be done either by dry seed method or through the green capsule method is still the second most fastest and surest means of propagating orchids. However, this method produces a lot of variant offsprings and are not all true to type.
The development of the technique of plant tissue culture of orchids and its practical usefulness needs to be created to Morel in 1952. Also, the development of various protocols and studies on the micropropagation of orchids in the Philippines needs to be given recognition.
Contributory to these are the works of Dr. Valmayor, Prof. Sajise, Prof. Arquiza, and Dr. T. Amore. Some foreign scientist which are also very important in the development of orchid micropropagation are those of Murashige, Skoog, Arditti, Sagawa, Rotor, Vajrabhaya, Kunisaki, Teo and others.
Plant tissue culture is a broad term which means the growing or cultivation of plantlets or plant parts in an artificial culture medium under aseptic conditions, The orchid industry was one of the most benefited with this technique because is the only means of mass propagating orchids. With the success in orchids, the technique was adopted to other ornamental plants. It is a generic name which includes the following techniques:
Embryo culture/embryo rescue – culture of isolated mature or immature embryos (seeds). It is a sexual means of propagation, but nevertheless, orchids produces thousands seeds (20,000 – almost a millions in some species). However, there is a great variation within offsprings. This is a very ideal for hybridization works. Also, based from Kamemoto et al (1999) there is no case yet that viruses from an infected mother plant is transferred to the seeds if dry seed method is used. Thus, It is also a means of producing virus free orchids from virus infected ones.
Shoot tip culture – culture of an apical meristem with some leaf primordial attached, in an effort to produce plantlets. These technique in orchids usually puts the mother plant in danger of death a sacrificing the mother plants. However, other techniques can be used like the use of flower buds.
Meristem culture – culture of the apical meristematic dome. It is popularly called “mericloning’’. The technique is similar to shoot tip culture, however, the term is strictly refers to isolating the apical dome. The explant is much smaller compared to that of the shoot tip. This is technique is done to primarily eliminate viral diseases in orchids.
Tissue (or callus) culture – culture of tissue arising from explants of plant organs like meristems, leaves, roots etc. and induced to form a callus (undifferentiated mass of dividing cells), which is prelude to production of protocom like bodies (PLB) and could later be induced to regenerated into whole plants. Most of the procedure in plant tissue culture pass through this stage  formation of callus.
Organ culture – culture is isolated plant organs like leaf, very young & undifferentiated flower buds, nodal segments of flower buds, roots and buds from pseudobulb or stem and permitted to form callus, undergo embryogenesis and regenerate into whole plants.
Anther culture – culture of anther (pollinia) or immature pollen grains in an effort to obtain a haploid cell or callus line. These haploid cells can be induced to become diploid by chemicals like colchicine (or other substances, while other automatically become diploid). These is useful in obtaining orchids with pure recessive lines.
Cell suspension culture – culture of isolated cells or very small aggregates of cells remaining dispersed in liquid medium. It is used prior to protoplast culture, or for production of protocom like bodies.
Protoplast culture – culture of naked cells (plants cells devoid of their cell walls using a cellulose digesting enzyme). Protoplast can be use in protoplast fusion (or genetic engineering), wherein two separate genomes can be combined into one cell, and the cell regenerated into a whole plant. A transgenic or genetically modified orchid (GMO) can be produced.
The steps in orchid micropropagation involves (a) selection of mother plants (b) sterilization of explant (the tissue you are going to use in tissue culture); (c) initiate culture; (d) proliferation, subculture and division of the plant tissue until desired number of plantlets are obtained; (e) differentiation and regeneration of tissue who plants and rooting; (f) acclimatization in the greenhouse; and (g) outplanting (compotting).
Culture media used for orchid micropropagation are Murashige & Skoog’s Media (MS), White’s Media, Knudson C Media, Vacin & Went Media, R Media, Gamborg B5 Media, Nitsch & Nitsch Media and a lot more. These media are usually supplemented with coconut water, sugar, and plant growth regulators (benzyl adenine, naphthaleneacetic acid, indolebutyric acid or kinetin).
There are a lot of advantages of micropropagation over the conventional means. Primarily it produces numerous propagules in relatively short period of time. It also uses relatively smaller space than conventional propagation methods. Propagation can be done all year round independent of seasonal changes. The technique also produces large number of disease-free planting materials, free from viruses, fungus, & bacteria. Thus they are not subject to quarantine during transport. However, virus indexing is still a necessity to absolutely certify that the plantlets are virus free. The technique can be use for conservation works and the storage of the plants are free from environmental risks. Since they are inside the lab, no labor and materials for watering, weeding and spraying of pesticides are needed and no care and attention is needed between subculture. Lastly, due to small size of orchid seedlings, they are less bulky to transport.
Plant tissue culture also has its drawback compared to the conventional means of propagation. First of all, it requires staff with high technical skill for successful operation. It also requires specialized and expensive production facilities, laboratory and greenhouse. It also need fairly specific methods or protocols to obtain optimum results from each species. Labor is also intensive (due to subculture), resulting in high cost of propagules. Plantlets obtained are initially small, and are not autotrophic and plantlets are susceptible to water loss. Plantlets need to undergo a transition period of hardening in the greenhouse. And lastly, there are chances that some laboratories could produce genetically aberrant plants due to extensive use of plants growth regulators. In order to prevent this from happening, plant with unstable genomes needs to be subcultured only up to the 7th subculture; after which, “ old cultures” are replaced with fresh new initial cultures.
Identify reputable sources of mother plants – Mother plants are very important in micropropagation, because it is from them where your initial plant tissues will come from. Motherplants which are disease free, properly indexed, and with desirable characteristics (with award winning qualities) is a necessity. The location where the plants are grown needs to be clean (no sources of contamination e.g. mushroom growing area, soil bacteria, or far from diseased plants, pollution free). It is also ideal that the plants to be used as motherplants be grown inside a greenhouse protected from the elements. Also orchid collectors are good sources of mother plants, especially if they have vast collections of different species and hybrids.
Identify & Designate a Service Laboratory - A laboratory equipped with technical capability and sufficient physical facilities which will do the job of micropropagating your orchids needs to be identified. The lab needs preparation room, a transfer room and a culture room. The laboratory operator needs to be capable enough to produce the number of seedlings you need. At least they need also a greenhouse large enough that can acclimatize the plants (compotted) before they are returned back to the client.
Designate a greenhouse or nursery specialist – In case the laboratory does not have a greenhouse, someone with expertise in out-planting and compotting orchid seedlings from flask is an additional requirement to successfully grow orchid seedlings. People in the orchid industry need to specialize into laboratory technicians, nursery men, orchid growers and sellers to simplify the process of orchid growing.
Availability of orchid growing technologies & information –There is a need for technologies in all aspect of orchid culture be readily available to all, especially to the orchid industry. Nowadays the advances in information technology (computers) are beneficial. This can be done by creating linkage or networks with the academe (local and international), government & private agencies, the orchid industry and the orchid societies or organizations. Another option is to have continuous training programs for new and emerging tissue culturists, orchidists, orchidologists, and taxonomists, so that knowledge is passed on to your younger generation
Orchid marketing plan – Market studies needs to be done through consultative meetings between the participants in the orchid industry to identify different problems, either technical or marketing. With this, new markets (locally or overseas) can be identified and targeted. Also, orchid trends and novelties can be identified. Thus, orchids which are mass-produced have sure markets.
Orchid Breeding Plan – There is a need to have an orchid breeding plan to continuously create new orchid hybrids for the cutflower & potted plants industry. This can be done by motivating local orchid breeders to pursue breeding works and selection of orchids with outstanding characteristics. These new hybrids will be the one which will be mass produced.
There is already a vast sea of information on orchid micropropagation. It is just a matter of identifying this information, teach it to interested persons, train them further, & provide sufficient finding to accomplish specific orchid propagating projects. It is an irony that the Philippines is a good teacher in terms of agriculture, but somehow we are being left behind by our Asia neighbors in capability of plant mass-propagation.
ROBERT. 1993. Micropropagation
Of Orchids. New York
John Wiley & Sons, Inc.
ARQUIZA et al. 1999 Orchid
Micropropagation (unpublished),
Philippines University of the
Philippines at Los Banos,
College, Laguna
1999, Breeding Dendrobium
Orchids in Hawaii. Hawaii
University of Hawail Press.
KANG, LEE CHEW. 1983. Orchids:
Their Cultivation &
Hybridization. Rev. ed. Malaysia
Eastern Universities Press SDN.
PCARRD. 1998. The Philippines
Recommends for Orchids
STEWART, JOYCE. Ed. 1992. Orchids
At Kew. Singapore. HMSO
Publications Centre
Orchid Tissue Culture Laboratory
Research & Development Center
Rizal technological University
Boni Avenue, Mandaluyong City
He can be contacted at ( 632)533-6041 loc. 124

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