GAINS FROM SELECTION UNDER DROUGHT VERSUS MULTILOCATION TESTING IN RELATED TROPICAL MAIZE POPULATIONS

Ideal maize (Zea mays L.) cultivars for tropical areas should yield well both in the presence and absence of drought, but optimal selection strategies for accomplishing this goal are not clear. This study evaluated progress from selection of two related tropical populations across a broad range of environmental conditions. 'Tuxpeno Sequia' (TS) had undergone full-sib recurrent selection for eight cycles at one location under managed levels of drought stress, while Tuxpeno 1' (T1) was selected for six cycles in a modified full-sib selection scheme that relied heavily on multilocation yield trial data. Combined over 12 environments (with mean yields ranging from 0.30-7.83 Mg ha(-1)), regression analysis revealed significantly different rates of change per cycle for TS and T1, respectively, for grain yield (1.68 and 1.06%, P < 0.10), anthesis-silking interval (ASI) (-8.59 and 0%, P < 0.10), ears per plant (1.26 and 0%, P < 0.05), and plant height (-0.83 and 1.29%, P < 0.01). Days to anthesis decreased in both TS and T1 (-0.36 and -0.15% per cycle, respectively), but the difference between populations was not significant at P < 0.10. The interaction of environments with the linear rate of gain in grain yield was not significant in either population, indicating similar progress across the range of environmental conditions sampled. Stability analysis indicated that TS Cycles 6 and 8 and the check variety 'La Posta Sequia Best' were the most stable and high yielding entries in the trial. Better yield gain in TS is likely related to its selection for reduced ASI under controlled stress at a single site. Selection under managed levels of drought stress at one location together with multilocation testing may be desirable components of maize breeding programs for drought-prone tropical areas.