The International Center for Maize and Wheat Improvement(CIMMYT) conducts selection of stress-tolerant genotypes under managed stress conditions. Data sets
for this study were from Intermediate to Late Hybrid Trials (ILHT) conducted in
five Eastern and Central Africa (ECA) countries from 2008 to 2011. Several trials,
which were categorized into four management systems and two yield levels were
used for this study. Variance Components, broad sense heritability (H), Site
Regression (SREG), Genotypic Regression (GREG) and Factor Analytic (FA)
models were fitted. We argue that it is preferable to first fit the fixed effect models
before proceeding to the mixed effect model, as the former shows the level of
complexity of the GE component and the number of axes required to explain it.
The fixed effect model, SREG2, is preferable for trials targeting comparison of
hybrids with checks. From the GGE biplots it was noted that the first two
principale components (PC) did not account for sufficient percentage of variation
for all years. Nevertheless, since PC1 accounted for large percentage of variation
than PC2, the plot gives some idea of which hybrids won where. Most importantly,
location of genotypes along PC1 can serve for judging yielding potential of the
genotypes to guide in selection decision. Equivalence between Finlay - Wilkinson
and GREG was established. The few environmental covariables obtained for 2009
were used to fit Partial Least Square (PLS) regression. The result indicated
complexity in the GE component, as PLS latent factors accounted for small
percentage of variation. It was recommended to use information from SREG2,
GREG2 and FA(1) models in order to identify stable genotypes.
