An extensive collection of Spanish maize was subjectively classified into 20 races and 32 intermediate varieties using morphological and agronomic data. Five of those 32 varieties were lost, and the remaining 47 populations are maintained at the Misión Biológica de Galicia. The objectives of the present study were to investigate the isozyme variation and the historical relationships of the Spanish maize races and intermediate varieties. Eleven isozyme systems encoded by 20 loci (15 polymorphic) were used to classify 20 races and 27 intermediate varieties. The isozyme classification showed that the intermediate varieties did not cluster together with their corresponding main races. Twenty-seven of the 47 populations originated from a single geographic area. Thus, a second isozyme classification was made for these 27 populations to investigate the relationships between the isozyme classification and the variability expected from historical records. The isozyme classification presented five to ten clusters. The first introductions of maize from the West Indies came to southern Spain and had little success. Guatemalan maize was more successful in the South of Spain and appears to have expanded to the East. South American maize had less influence in Spain than North American maize. North American maize was well established in the North and Northwest of Spain around the 17th Century, and it kept coming during the succeeding Centuries, including hybrids of the modern race Corn Belt Dent. The conclusions are (1) the classification of Spanish maize into 20 races and 27 intermediate varieties does not appear to reflect the structure of the variability of Spanish maize, and (2) maize came to Spain from all over the Americas, mainly from Central America at the beginning and from North America during the last four centuries. Although most of the primitive introductions may have been lost, some remain in our collection of local maize varieties; these represent a unique set of tropical to temperate populations adapted to temperate European conditions.

Research supported by the European Union (Project RESGEN-CT96-88).

Peer reviewed