Progress from recurrent full-sib family selection for potential yield improvement in two tropical maize (Zea mays L.) populations

Abstract

Abstract The objectives of the experiment were: (a) to evaluate the effectiveness of a recurrent full-sib family selection scheme in the improvement of grain yield, plant height, ear height, maturity and standbility; and (b) to determine if there were any correlated response on tassel size, stalk rots, husk cover and husk extension in two tropical maize populations: Tuxpeno 1 and Mezcla Amarilla. Yield trials were conducted during the winter season of 1975/1976 and, the summer season of 1976 at two locations in Mexico. The entries consisted of four Cn populations of Tuxpeno: C0, C4, C8 and C12; five Cn populations of Mezcla Amarilla: C1, C2, C4, C6 and C8; plus each of the above Cn populations selfed. A randomised complete block design with three replications was used for each population. There were three sub-plot densities in each plot: (a) a low density of 32 000 plants per ha; (b) a common density of 50 000 plants per ha; and (c) an optimum density for each entry. The Tuxpeno Cn selfed populationsshowed significant grain yield improvement at all the densities used. However, the Tuxpeno Cn populations showed no significant grain yield improvement (P = 0.05) when tested at the densities of 32 000 plants per ha; (b) a common density of 50 000 plants per ha; and (c) an optimum densities, the Cn populations ot Tuxpeno showed a grain yield improvement of 45% in twelve cycles of selection. In the Mezcla Amarilla population there were no significant changes in the mean of grain yield at all densities. The lack of progress in yield improvement in Mezcla Amarilla was attributed to: (a) the initiation of selection in a population that was not in genetic equilibrium; and (b) a narrow base of additive genetic variation. There was a significant reduction in the number of days to anethesis, plantheight, ear height and tassel size in both populations. The Cn populations of Tuxpeno and Mezcla Amarilla showed no significant changes in the percent stand. However, the Cn selfed populations of Tuxpeno showed some significant improvement (P = 0.05) in percent stand at 32 000 plants per ha and the optimum density. There were no significant changes (P = 0.05) in the husk extension, husk cover, Diplodia stalk rot and Fusarium stalk rot.