Isozymatic diversity in the races of maize of the Americas

To determine the genetic diversity of the races of maize of the Americas, 1080 accessions representing more than 300 races were analyzed for 13 enzyme systems encoded by 23 genetic loci. The analysis of the data revealed very different levels of genetic diversity across countries. A total of 329 :alleles were recorded; however, about 81% of the alleles found in the :accessions studied were rare, occurring at frequencies below 0.01; some were observed in only one accession or only one race. There are two geographical regions where allelic diversity is concentrated: Mesoamerica and the Andean Region. In general, the levels of racial diversity can be attributed to geo graphic range. The uses by human groups and sample sizes of the seed lots used by farmers from one cycle to the next are factors which likely affect this diversity.