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Babes in the wood: from embryo to plantlet
We often speak of plants’ developmental plasticity and their ability to regenerate from excised pieces. However, gardeners and horticulturalists know that, actually, plants are extremely variable in this respect. Some plant species can regenerate from seemingly unpromisingly small fragments (as I know from moving an acanthus in my garden). At the other end of the scale are plants that we cannot get to regenerate from any sort of cutting. The same range of interspecific variation is seen in the propagation of plants from in vitro culture, and it is this topic that has been studied by Corredoira et al. (Santiago de Compostela, pp. 129-136). They note that chestnut (Castanea sativa) is suitable for improvement by GM technology, especially in respect of resistance to fungal diseases. However, this approach has so far failed because of failure to regenerate plants from culture. So, where does one start? There are obvious general principles and there are also procedures known to have worked with similar species, but in the end it has to be a thorough, painstaking empirical approach, evaluating all possible factors. This is clearly seen in the work of these authors and furthermore, the approach has been successful. Good embryogenic cultures have been established and plants have been regenerated from them. The original embryogenic cultures were obtained from leaf explants and the somatic embryos were multiplied either directly or via callus. The ‘germination’ potential of these somatic embryos was strongly affected by the carbohydrate source and by temperature. Maltose was the ideal carbohydrate and the temperature regime needed to include 2 months at 4 deg Celsius. Somatic embryos matured in this way showed a 39 % conversion rate to plantlets, which were then multiplied by micro-propagation. We are still a long way from the first GM chestnut, but the authors’ careful work has given them an excellent start.
Professor J. A. BryantUniversity of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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