ISOZYMATIC PROFILE OF MAIZES NATIVE TO THE TEHUANTEPEC ISTHMUS, OAXACA, MÉXICO. I. CHARACTERIZATION OF GROUPS

Abstract

Maize (Zea mays L. ssp. mays) is the most important and diverse of the cultivated species in México. Genetic diversity of the primary Mexican races of maize has been studied on the basis of agronomic, morphological and molecular markers such as isozymes data; however, the studies involving isozymes have only considered a low number of representative populations for each race; therefore, more in-depth studies are necessary for revealing the extent of genetic variation within races. The objective of this research was to evaluate the isozymatic polymorphism of maize populations from the Tehuantepec Isthmus, at Oaxaca, México, which is the area of natural distribution of the Zapalote Chico race. Forty native populationns and 10 populations representative of other maize races, were evaluated in order to analyze genetic variation of 19 isozyme loci. A total of 52 alleles, with an average of 2.7 alleles per locus, were found. Native populations had 49 alleles, outnumbering representative populations of other races by 10 alleles. Analysis of genetic diversity of the native populations, based on the statistic for genetic differentiation (GST) showed that 88 % of the isozymatic variation resides within populations and 12 % among populations. Cluster analysis separated two groups of native maize, the first one integrated populations of the Zapalote Chico race, while the second one grouped populations locally known as Maíz Grande, with some influence of races Zapalote Chico and introgression of Tuxpeño, Vandeño and Tepecintle. Gene frequencies analysis revealed the isozymatic profile for each group. Results indicate the presence of genetic variation into native maize populations from the Tehuan-tepec Isthmus, readily available for use in breeding programs.