Pollen movement between native maize Yucatán and maintenance of genetic diversity

In Yucatan, Mexico, the cultivation of different native maize populations in the system milpa, promote the interchange of pollen. To evaluate the relationship between the flow of pollen and the dynamics of genetic diversity in 2005 and 2006, a white kernel population and another yellow, both of the Xmejen-nal and Xnuc-nal types, were grown associated with squash. The yellow kernel variety was planted surrounded by the white kernel variety, 540 ears were harvested in 8 directions, from the periphery to the center, and the percentage of yellow grain in the white variety was used as indicator of out crossing rate. For each direction, regression analysis was performed between distance and yellow kernel percentage. The largest out crossing rates in Xmejen-nal (44 %) and Xnuc-nal (42 %) were obtained in the direction northeast-southwest in 2005; and indirection southeast-northwest in Xmejen-nal (37 %) and Xnuc-nal (41 %) in 2006. Both direction and intensity of dominant wind determined trajectories of pollen, and the out crossing rate was reduced with the distance to the source of pollen. Genetic interchange is promoted by management and genotype distribution in both time and space, and gene flow among populations promotes intrapopulation diversity.