Dryland maize (Zea mays L.) production in western Nebraska and adjacent areas is constrained mainly by water-limiting factors throughout the growing season. Nine elite single-cross (SC) hybrids and their 36 double-crosses (DC) were evaluated in western Nebraska, eastern Wyoming, and northeastern Colorado in 1998 and 1999 under different water regimes to assess differences in yield and drought-related characteristics among them, to estimate combining ability effects of these characteristics, to uncover patterns of GE interaction, and to assess the potential of indirect selection for grain yield in dryland environments based on selection under irrigated conditions. Single-cross hybrids were superior in yield to DC hybrids across all water regimes. On average, DC hybrids yielded 11% less than SC hybrids. However, the difference in yield could not be explained by differences in drought-related characteristics between SC and DC hybrids. A diallel study showed that grain yield was largely controlled by non-additive gene action, whereas drought-related characteristics were under control of additive gene action. Across all water regimes, specific combining ability (SCA) effects were more stable than general combining ability (GCA) effects. A strong association in SCA effects between yield and drought-related characteristics was observed, even under irrigated conditions. Single-cross hybrids showed a superior stability across all environments, and DC hybrids showed a better stability across harsh environments. However, SC hybrids showed superiority in yield even under the lowest-yielding conditions. Yield-component compensation and drought-escape appeared to be the mechanisms of stability among these materials. Crossover and correlated response analysis indicated that selection for grain yield in irrigated conditions for production under the dryland environments might be possible. The study suggested that screening among elite SC hybrids under irrigated environments in the area for low susceptibility to drought stress and earliness might increase the productivity of hybrid maize in the target area. Alternatively, a selection based on SCA effects for yield, which can be applied under irrigated conditions, might indirectly increase drought tolerance in hybrid maize
