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Spatial Dependence of Growth Attributes and Local Control in Wheat and Oat Breeding Experiments

Central Soil Salinity Res. Inst., Karnal 132001, India
Hannover Waterworks, P.O. Box 5747, D-3000 Hannover 91, Fed. Rep. of Germany
Inst. of Applied Genetics, Herrenhäuser Stn. 2, D-3000 Hannover 21, Fed. Rep. of Germany

^* Corresponding author.

Adjustment for microenvironmental heterogeneity in inadequately replicated field experiments is desirable for maximizing genetigains through selection. Moving means, empirically weighted means, and a model-based optimal predictor (kriging) have been used to estimate an index of the local heterogeneity of 276 wheat (Triticum aestivum L.) and 336 oat (Avena sativa L.) plots. The adjustments of the data based on this index have been compared. The wheat experiment was unreplicated and that on oat had two replications. Trend variation along rows and columns was about 25% of the variance in wheat and 9 to 18% in the oat trial. Depending on the trait, 39 to 54% of the remaining variability of wheat and 7 to 20% of oat was stochastically isotropically spatially structured. Kriging reduced the coefficient of variation (CV) in all the traits, including yield, and never made overcorrections for the local variation, whereas adjustments based on moving means and empirically weighted means frequently increased the CV. Local control simulated only from check plots was less practical in wheat as compared to oat. Wheat selections from the unadjusted data were paired or clustered in localized parts of the field. These selections became randomly distributed across the entire field after the microenvironmental variation was removed by the kriging method.

Received for publication July 24, 1989.