Miracle or menace? : biotechnology and the third world / by Robert Walgate.

  • Walgate, Robert
Date:
[1990]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Miracle or menace? : biotechnology and the third world / by Robert Walgate. Source: Wellcome Collection.

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    Chapter 5: Three crops: cocoa, cassava and trees 69 Australia, Brazil, Canada, Europe, Japan and the United States — on more than 60 tree species. Clones can be made by micrografting the meristems of a tree onto rooted seedlings. In Brazil and the Congo, large areas are already being replanted by the rejuvenation of old trees by coppicing. Century-old redwoods and teaks have been successfully cloned. Plantation owners are already attempting to use tissue culture to clone the best fruit trees, oil palm, date palm, coconut palm, cacao trees, ornamental trees, and wood species for timber and pulp. One paper pulp company — Aracruz, in Brazil — raised pulp output 137% in seven years by propagation of cuttings from selected high-pulp-productive, coppiced eucalyptus. However, the only forest trees which currently benefit from commercial micropropagation are wild cherry and aspen. Unfortunately, as with oil palm, the expected advantages of producing an exact genetic copy of the initial tree are often altered by the persistence in the clone of variations — such as abnormal flowering and poor fruits in oil palm — which develop in the tissue culture. The cause of these changes is still a mystery. Quite considerable differences may develop between the expected and actual productive gain from the clone. Among fruit trees, mango, papaya and clove have been regenerated in Florida with some success. But as with tropical pines, eucalypts and palms, lengthy field trials are needed before it is clear that tissue-cultured trees will be successful. Breeders are targeting growth-rate, shape (to ease fruit picking by reducing stem height, for example), and flowering characteristics [15]. Many billions of hectares of developing country land which are under-productive because of saline, metallifled or otherwise poor soils (there are 150 million hectares of wasteland in India alone) could be reclaimed for forestry if species tolerant to these conditions could be selected and cloned. Biotechnology could help select and propagate Acacia, Prosopia and Sesbania tree species, which fix nitrogen, to maintain soil fertility and protect against erosion. The genetic engineering of trees is less advanced than their cloning. Yet the plant genetic engineers' main tool for transferring genes, the bacterium Agrobacterium tumefaciens, has been used to genetically engineer important US timber trees (Loblolly pine and Douglas fir). Resistance to diseases and chemical stresses such as salts and herbicides will be engineered in and selected through tissue culture, and breeding rates will be greatly increased [16]. In the genetic conservation of tree species, cryopreservation of germplasm would also reduce the present need to plant vast areas with
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