Genotype×Environment Interactions of Maize Hybrids Among Temperate and Tropical Inbreds in Temporal and Spatial Environments

Multi-location trials represent a major cost to the breeder of temperate corn hybrids. High stability of corn hybrids across a wide range of spatial environments is essential in oder to be accepted by farmers. In the tropics, however, it is possible to exploit year-round growing conditions and evaluate in multi-seasonal trials. Stability across a wide range of temporal environments is equally essential to grower acceptance in the tropics. This study involved a comparison between a set of 21 temporal environments in Hawaii imposed on a 6-entry diallel crosses and a set of 6 spatial environments in 4 dispersed locations (Colombia, Hawaii, Iowa, and Korea) imposed on a 10-entry diallel crosses. Extremely wide variations occurred not only depending on different hybrids but also on different environments. Each diallel crosse involved both temperate (temp) and tropical (trop) inbred parents. Fifteen hybrids among 3 temp and 3 trop inbreds were common to both the temporal and spatial trials. These hybrids showed a highly significant rank correlation (r = 0.75**), indicating that temporal environments were as effective as spatial environments in identifying superior germplam. Stability parameters were based on both regression coefficients and deviations from regression. They were highest across both temporal and spatial environments among trop×trop and trop×temp hybrids. About half of the trop×temp hybrids showed superior average grain yields and stabilities. The results suggest that tropical inbreds contributed stability while temperate inbreds contributed high performance. Analysis of the diallels permitted evaluations of GCA×E and SCA×E effects, of which the former was highly significant while the latter was only mildly significant. Thus G×E interactions could be interpreted as due primarily to the linear response of GCA effects to the environment, encouraging breeder selection for stability of inbred parents across temporal environments such as those available in Hawaii.