ISHS Acta Horticulturae 495: WCHR - World Conference on Horticultural Research
IN VITRO CONSERVATION OF HORTICULTURAL GENETIC RESOURCES REVIEW OF THE STATE OF THE ART |
| Author: | F. Engelmann |
| Abstract:
A large number of agricultural crops have seeds which are termed orthodox, i.e. that can be dehydrated down to low water contents and can thus be stored at low temperature for extended periods (Roberts, 1973). There are three main categories of plant species for which conservation in seed form is problematic. Firstly, some crops such as banana and plantain do not produce seeds and are thus propagated vegetatively. Secondly, some species such as potato or sugarcane include both sterile genotypes and genotypes which produce orthodox seeds. However, these seeds are generally highly heterozygous and are thus of limited interest for the conservation of particular genotypes. These species are thus mainly maintained as clones. Thirdly, numerous fruit and forest tree species, especially from tropical origin, produce recalcitrant seeds, i.e. seeds that cannot be dried to sufficiently low moisture level to allow their storage at low temperature (Roberts, 1973). There is also a large number of species, termed intermediate (Ellis et al., 1990) for which conservation in seed form is still problematic. The traditional ex situ conservation method for these categories of plant species is in the form of field collections. Conservation in the field presents major drawbacks which limit its efficacy and threaten the safety of plant genetic resources conserved in this way (Withers & Engels, 1990). Finally, the development of biotechnology leads to the production of a new category of germplasm including clones obtained from elite genotypes, cell lines with special attributes and genetically transformed material (Engelmann, 1994). This new germplasm is often of high added value and very difficult to produce. The development of efficient techniques to ensure its safe conservation is therefore of paramount importance. Tissue culture techniques are of great interest for the collecting, multiplication and storage of plant germplasm (Engelmann, 1991). Tissue culture systems allow to propagate plant material with high multipfication rates in an aseptic environment. Virus-free plants can be obtained through meristem culture in combination with thermotherapy, thus ensuring the production of disease-free stocks and simplifying quarantine procedures for the international exchange of germplasm. The miniaturisation of explants allows to reduce space requirements and consequently labour costs for the maintenance of germplasm collections. This paper presents a brief overview of the techniques employed or under investigation for in vitro conservation of plant tissues and organs. | |
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