Isozyme variability among European maize populations and the introduction of maize in Europe

Abstract

Several theories have been advanced to explain the origin of European maize (Zen mays L.) based on history, yet neither the introduction of this crop, nor the variability among European populations, have been extensively studied until recently. The aim of the present investigation was to relate isozyme variation in European maize populations to the introduction of the species on this continent. Ten isozyme systems encoded by 19 loci were used to classify 404 maize open-pollinated populations from six European countries. The average number of alleles per locus in the collection was 3.1. Allele richness was quite homogeneous across countries. The distribution of rare alleles supports the historical conclusion that Spain was the main entrance of maize to Europe. Alleles shared by maize from Mediterranean countries and Mexico or Guatemala sugggest that the source of Mediterranean maize could have been these areas of Central America. Some rare alleles absent in Spain suggest that maize was also introduced through other countries. The collection of European populations was classified into two main groups, the smaller containing those of Northern Europe and the larger divided into Mediterranean and miscellaneous subgroups. Several singularities were seen that might be explained by drift or particular introductions. The results suggest that maize from North America came to Europe via the European Atlantic coast, and from Central America to the Mediterranean region, though introduction through other ways cannot be discarded on the basis of the present isozyme data.