CHARACTERIZATION AND GENETIC ORIGIN OF THREE MAIZE RACES BASED ON CHROMOSOMIC KNOBS DATA

Abstract

At present time there is general consensus that maize was originated and domesticated from the annual Mexican teosinte. The cytological results have found that the beginning of this plant occurred in five origin and domestication centers in Mesoamerica. Many researchers have studied the great genetic variation that maize shows in various regions of Mexico, but none has proposed the mode and place of origin of each of the Mexican races. It was though that through the analysis of geographic and racial patterns of distribution of chromosome knobs obtained from a larger number of accessions and plants per race the origin and evolution of each of them could be known. Fifteen accesions of the Chalqueño race, 22 of Cónico and 19 of Cónico Norteño were studied trying to analyze 20 plants of each accesion. Groups of knobs (long chromosomes vs. short chromosomes, long arms vs. short arms, etc.) were graphically compared looking for distribution patterns that could characterize and evidence the possible origin of each of the three races. In general, results showed that Cónico Norteño is characterized because it has a high frequency of large knobs, higher than that of Cónico and Chalqueño, races that shared these frequencies with the medium-sized knobs but differ in that Chalqueño has predominance of small knobs. The characterization of the three races, along with previous information on the knob complexes, allowed to propose the genetic origin of each one of them. These results suggest chromosome knobs are important elements in the evolution of races in the genus Zea.