ISOZYME VARIATION AND HISTORICAL RELATIONSHIPS AMONG THE MAIZE RACES OF SPAIN

An extensive collection of Spanish maize was subjectively classified i nto 20 races and 32 intermediate varieties using morphological and agr onomic data. Five of those 32 varieties were lost, and the remaining 4 7 populations are maintained at the Mision Biologica de Galicia. The o bjectives of the present study were to investigate the isozyme variati on and the historical relationships of the Spanish maize races and int ermediate varieties. Eleven isozyme systems encoded by 20 loci (15 pol ymorphic) were used to classify 20 races and 27 intermediate varieties . The isozyme classification showed that the intermediate varieties di d not cluster together with their corresponding main races. Twenty-sev en of the 47 populations originated from a single geographic area. Thu s, a second isozyme classification was made for these 27 populations t o investigate the relationships between the isozyme classification and the variability expected from historical records. The isozyme classif ication presented five to ten clusters. The first introductions of mai ze from the West Indies came to southern Spain and had little success. Guatemalan maize was more successful in the South of Spain and appear s to have expanded to the East. South American maize had less influenc e in Spain than North American maize. North American maize was well es tablished in the North and Northwest of Spain around the 17(th) Centur y, and it kept coming during the succeeding Centuries, including hybri ds of the modern race Corn Belt Dent. The conclusions are (1) the clas sification of Spanish maize into 20 races and 27 intermediate varietie s does not appear to reflect the structure of the variability of Spani sh maize, and (2) maize came to Spain from all over the Americas, main ly 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 vari eties; these represent a unique set of tropical to temperate populatio ns adapted to temperate European conditions.