Genetic Conservation

The genetic conservation movement was initiated by Otto Frankel, who was a wheat breeder concerned exclusively with vertical resistance. Frankel feared that the local landraces of wheat in the Middle East would be lost, as the Green Revolution produced an explosion of wheat production, and imposed an incredible genetic uniformity on that production. It must be appreciated that these Middle East landraces were the source of vertical resistance genes to wheat parasites. In those days, it was believed that a good source of resistance was essential in any breeding for resistance. If that source of resistance were lost, the breeding would become difficult, even impossible.

Many scientists and environmentalists followed up Frankel's initiative, and genetic conservation is now a major activity in most crop research establishments. It is also a very expensive and time-consuming activity that involves many thousands of seed accessions stored in so-called 'gene banks'. Even though the seed is stored with a very low moisture content, and kept at low temperature, to prolong its viability, each accession must be periodically grown in order to supply fresh seed. This is a costly business. After all, there are several hundred species of cultivated plant, and many of them have cultivars numbered in the thousands. The gene bank of a tree crop is generally preserved as an arboretum. There are now many scientists and technicians employed full-time in this work of genetic conservation.

Frankel did not recognise the possibility of horizontal resistance. His case for genetic conservation was correct only so long as vertical resistance was the sole resistance available to plant breeders. This concern over genetic conservation is a concept of the Mendelian school of genetics, because it applies only to singlegene characters that are amenable to gene-transfer breeding techniques. However, as we have seen, Mendelian characters of agricultural significance are rather rare in cultivated plants. They include vertical resistances and short straw in the dwarf wheats and rices. Breeders who employ horizontal resistance do not work with single-gene characters. Nor do they need a source of resistance (see 7.2.7). They can obtain all the quantitative resistance they need from a population of susceptible plants, provided a reasonably wide genetic base is present. Obviously, as the use of horizontal resistance increases, so the importance of genetic conservation will decline.

If the postulations made in this book are correct, there will be a multiplicity of breeding programs in a multiplicity of agro-ecosystems, producing thousands of progressively improved cultivars. There will then be little need for formal genetic conservation, as it is recognised at present. This is because the genetic conservation, like the crop improvement itself, will become self-organising. The farmers themselves will conserve the best cultivars and, on a global basis, the genetic diversity will be extremely wide.

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