RACIAL COMPLEXES OF MAIZE POPULATIONS EVALUATED IN SAN MARTíN HUAMELULPAN, OAXACA

The milpa system produces and maintains the major proportion of maize diversity of Mexico and particularly in the Mixtec-Oaxaca region such event occurs since pre-Columbian age. In order to evaluate the phenotypic variation of the Mixtec maize, 100 samples were collected in 14 municipalities of the Tlaxiaco district, Oaxaca. The collection was morphologically characterized under a simple lattice design with two replications during summer-fall 2008. Morphological description was made by 18 variables as well as grain yield. The analysis of variance showed significant differences among the samples for all evaluated variables, except for the number of secondary branches on tassel and rachis diameter of the pith. According to principal component analysis, the morphological variation presented a pattern of altitudinal variation following the accession origin. Cob and plant height, length and number of branches on tassel, days to tasseling and to silking, cob length and number of rows on cob, explained the major proportion of the morphological variability. All samples were classified into nine phenotypic groups by cluster analysis; they were called as Mixteco race, Chalque o race, and seven racial complexes that joined combinations of the Chalque o, Conico, Mixteco and Pepitilla races. There was a high morphological variation among evaluated samples and the Mixteco and Chalque o races were differentiated, but also seven groups that phenotypically correspond to racial complexes. In the evaluation were observed samples with cob characteristics closely to the description of the Bolita, Serrano Mixe and Ancho races.