SPATIAL AUTOCORRELATION IN THE EVALUATION OF MAIZE COMPOSITES FOR RESISTANCE TO FALL ARMYWORM (Spodoptera frugiperda)

Abstract

Composites of maize (CRL-01, CRL-02 and CRL-03) were synthesized from crosses of adapted materials with exotic materials that have shown resistance to fall armyworm (Spodoptera frugiperda). Full-sib progenies from the three composites were evaluated for resistance to fall armyworm using a scale varying from 0 (no damage) to 5 (destroyed whorl). The experimental design was randomized complete blocks with two replications. Two models were considered: using the classical analysis with independent errors, and a model with spatially correlated errors. In the spatial model, the residual covariance matrix (R) followed a model built according to the spatial autocorrelation detected in the experiment. The test of Durbin-Watson was used to detect the presence of the spatial autocorrelation between plots, which showed to be highly significant. The distance range of the spatial autocorrelation was about 1.5 m. The use of the spatial model allowed a better local control, resulting a reduction in the estimates of residual variances and an increase of heritability coefficient estimates and expected progress with the selection. The ranking of progenies was changed when using different models of analysis. The use of mixed model was more appropriate than classical analysis in such circumstances.

KEY-WORDS: Exotic germplasm; spatial autocorrelation; mixed model; BLUP.