SIMILARITIES AMONG TEST SITES BASED ON CULTIVAR PERFORMANCE IN THE HARD RED WINTER-WHEAT REGION

Maximizing crop productivity requires effective selection and targeting of cultivars for appropriate production areas. Understanding similarities in cultivar response among test sites and underlying production zones within a crop production region is important for breeders to effectively choose test sites and interpret test data. Thirty years of wheat (Triticum aestivum L.) yield data from the Southern and Northern Regional Performance Nurseries (SRPN and NRPN, respectively) were analyzed in order to determine similarities among test sites and production zones in the Great Plains hard red winter wheat growing area. Correlations of cultivar yields among locations each year were averaged and used as a basis for principal factor analysis. Six intraregional production zones were identified in the SRPN, with six factors accounting for 55% of the variability in the location correlation dependence structure. Four of the factors essentially divided the central plains region on north-south, east-west axes, representing the south-central plains, north-central plains, southern high plains, and central high plains areas. Five production zones were identified in the NRPN, with five factors accounting for 55% of the variation in the location correlation dependence structure. Factor analysis was used to further classify sites within three of the larger production zones in the SRPN and two in the NRPN. Sixteen smaller production areas were identified within these major zones. Elucidation of intraregional cultivar production zones should facilitate more precise targeting of wheat breeding and evaluation efforts.