ADAPTATION OF TUXPENO MAIZE TO MEXICAN HIGH VALLEYS THROUGH MASS SELECTION

Mexico has an ample, unexploited genetic variability in maize (Zea mays L.). Maize breeding programs in the highlands have mainly used varieties of the local races Conico and Chalqueno, with little or no use of exotic materials from other regions. In this study, grain yield of four Tuxpeno maize populations was evaluated as a criterion for adaptation to the highlands. The populations were assessed in their Cycle 1 (unadapted) and Cycle 7 (adapted) versions, along with the H-S2, Promesa, and San Jose hybrids as controls. The evaluation was carried out at the Experimental stations at Colegio de Postgraduados and INIFAP in Texcoco, State of Mexico. In both locations, randomized complete blocks designs with three replications were used. Male and female flowering, plant and ear height, ear length, ear diameter, number of rows, kernels per row, and grain yield were recorded. Results showed significant changes in grain yield and its components in the advanced selection C7 (5.5 to 7.9 t ha(-1)), compared to C1 (1.5 to 2.2 t ha(-1)). Yield components with significant favorable changes were ear length and diameter, number of rows, and kernels per row. Cycle 7 populations outperformed up to five times those of the initial cycle; however, it did not match the yield of 11.4 t ha(-1) of the control hybrids. Tuxpeno C7 maize populations can be considered as exotic tropical varieties adapted to highlands, as they showed yields of 5 to 7 t ha(-1). Furthermore, they provide valuable novel genetic variation that could be used to improve local maize or used per se as new varieties.