INTERNATIONAL SYMPOSIUM ON THE TAXONOMY OF CULTIVATED PLANTS FINAL SUMMING UP

The Symposium began with two keynote addresses, the first by Professor W. T. Stearn, tracing the history and background of the Cultivated Plant Code. This was followed by an equally valuable contribution by C. D. Brickell on the aims and possible future development of the Code, making a plea for standard specimens, and perhaps also standard descriptions, to be linked to each cultivar when it is registered.

From the first section on Nomenclature and others which followed, it became clear that much discussion was needed before stability of naming and simplicity of classification could be attained. In fact, several speakers emphasised the need for simple classifications which would themselves help towards nomenclatural stability at levels higher than that of the cultivar.

The nature of the lowest classificatory unit - the cultivar - was discussed at length, different viewpoints arising partly from the fact that some cultivars are clones, and thus genotypically constant, whilst others are propagated by seed, in which at least a narrow range of genetic diversity is inevitable. Even so, the stability of all cultivars was considered to be one of their essential features. A misunderstanding about clonal selection was resolved when it was pointed out that certain materials thought to be genotypically constant clones were in fact mixtures of genotypes, probably arising through somatic mutations. In such circumstances clonal selection could result in the separation of pure genotypes, some of which might be better adapted to certain conditions than the original mixture.

Above the cultivar level and still below the level of species two main ways of classification were discussed:

1. The Linnaean hierarchical system, often of great complexity, and with latin names and validly published descriptions at each level.
2. The informal group system of a limited hierarchical structure, or none at-all. This was proposed as a simpler, more flexible system, more in true with the biological situation under consideration.

On the whole, and particularly for the vegetable and field crops, the group system was favoured by many contributors. For ornamentals the Linnaean system, was favoured by many contributors. For ornamentals the Linnaean system, or even possibly dual systems, were considered possible. More discussion on this point is needed in the future.