abstract
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The improvement of self-pollinated crops employs crosses between different genotypes. Repeated use of "the best" genotypes may lead to restriction of the genetic diversity of the crop. Analysis of gliadin (storage protein) polymorphism has provided evidence that, in wheat, genetic diversity is high, stable throughout the 20th century and structured spatially worldwide. An unexpected finding is that many registered wheat cultivars are genetically non-uniform, due to the presence of authentic biotypes (multiple genotypes originating from the initial cross) in spite of current crop-registration rules having a strict demand for each new cultivar to be genetically uniform. We suggest that each cultivar is the fruit of joint effects of a breeder and of a region's environmental factors. There may be a need to re-evaluate relevant rules of cultivar registration for crop species in general.