Rapid results from micropropagation

Plants can be propagated vegetatively as well as sexually: vegetative propagation generally produces a new generation of genetically similar plants, whereas sexual reproduction may result in offspring with unpredictable characteristics. Plant breeders often need to produce huge numbers of plants, all of which can be guaranteed to have the characteristics so painstakingly bred into their parental lines: this can be achieved through vegetative propagation. Traditional techniques of vegetative propagation practised by horticulturalists, or by cassava farmers who plant from cuttings, tend to be slow and tedious. These techniques are carried out in natural conditions (in vivo). Plant scientists have developed more efficient means of achieving the same ends, through techniques that are carried out in sterile conditions in laboratories(in vitro). Single cells can be regenerated into whole plants in some cases, and this permits remarkably rapid rates of propagation to be achieved. CTA has published a new title (No 4) in its a Technical Memoir series: 'Study on the rapid multiplication of plant material', by Dagmar Jordens-Rottger. This publication will interest anyone who is faced with the need to rapidly propagate large numbers of plants with identical genotypes. But not all plant species can be propagated in this way, although the list of species amenable to this technology continues to grow. There are many reasons why plant propagators welcome the opportunity to use these techniques on a wider range of plant species: rapid multiplication means that new varieties can be developed more quickly; the material produced can be disease-free; it is more uniform, and there is more control over quality; growers are independent of natural growing seasons, and much space can be saved. Some of these benefits, it has to be admitted, are of little interest in the Third Worid, where uniformity is not always required and where space is usually not at a premium. The author of this Technical Memoir has considered carefully the applicability of these techniques to developing countries, and has concluded that the most appropriate approach involves a combination of in vitro cultivation and subsequent in vivo propagation of disease-free juvenile material. Most of the study is concerned with in vitro propagation. The principles of micropropagation are reviewed. There is a useful and interesting section in which the suitability of specific crops for micropropagation is examined; not surprisingly, the techniques are considered particularly relevant to woody species which are naturally very slow growing. The technologies have been slow to develop: there is, for example, still no tried and tested method of propagating tea or cacao, despite the commercial importance of those crops. On the other hand, successful techniques have been developed for coffee. The study contains a review of methodologies for testing for pathogens, and there is a brief account of trends in research and application. For those who want to study the subject further, there is advice on how to set up a laboratory. In addition to a comprehensive bibliography, the study also includes practical information about 52 organizations, mainly in Europe and North America, which are actively using or developing micropropagation techniques. Copies of Technical Memoir No.4 are available from CTATechnical Memoir No 4: 'Study on the rapid multiplication of plant material', by Dagmar Jordens-Rottger CT