Breeding for heat tolerance in bread wheat ( Triticum aestivum
L.) is a serious global concern due to the
increasing threats of high temperature. Thus, 189 wheat
genotypes coded from 1 to 189 were evaluated for heat
tolerance in normal and late seasons in the International
Centre for Agricultural Research in Dry Areas (ICARDA),
Tel Hadya, Syria, from 2010 to 2012. The experiments
were laid out in alpha lattice designs with two replicates.
Data collected on the grain yield, days to heading and
maturity, grain filling duration and plant height were
subjected to restricted maximum likelihood (REML)
analysis for generation of the best linear unbiased estimates
(BLUEs). Very highly significant effects (p ≤ 0.001) of
genotype, season, and genotype by season interaction on
grain yield and other traits were obtained. The grain yield
and other traits performance of the wheat genotypes were
significantly (p ≤ 0.05) higher in the normal season than
in the late season. Genotype 148 was among the 30 top
grain yielding genotypes in all the environments, while
genotypes 172 and 124 were among the top yielding
genotypes in all the environments except in late season 2.
The relative heat tolerance of the genotypes ranged from
-33.69% to -77.95% in late season 1 vs.
normal season 1
and -65.28% to -95.83% in late season 2 vs.
2. The high variability obtained in the germplasm underlies
sufficient genetic variability for improving heat tolerance
in bread wheat.