Abstract:
Twenty five spring wheat
genotypes were evaluated for terminal heat
stress tolerance in field environments in the
Agro Ecological Zone-11 of Bangladesh,
during 2009-2010 cropping season. The
experiments were conducted at Wheat
Research Centre, Bangladesh Agricultural
Research Institute, using randomized block
design with three replicates under non-stress
(optimum sowing) and stress (late sowing)
conditions. Seven selection indices for stress
tolerance including mean productivity (MP),
geometric mean productivity (GMP),
tolerance (TOL), yield index (YI), yield
stability index (YSI), stress tolerance index
(STI) and stress susceptibility index (SSI)
were calculated based on grain yield of
wheat under optimum and late sowing
conditions. The results revealed significant
variations due to genotypes for all
characters in two sowing conditions.
Principal component analysis revealed that
the first PCA explained 0.64 of the variation
with MP, GMP, YI and STI. Using MP,
GMP, YI and STI, the genotypes G-05 and
G-22 were found to be the best genotypes
with relatively high yield and suitable for
both optimum and late heat stressed
conditions. The indices SSI, YSI and TOL
could be useful parameters in discriminating
the tolerant genotypes (G-12, G-13, and G-
14) that might be recommended for heat
stressed conditions. It is also concluded
from the present studies that biomass, grain
filling rate and spikes number m-2 are
suitable for selecting the best genotypes
under optimum and late sowing conditions
because these parameters are highly
correlated with MP, GMP, YI and STI.
However, high ground cover with long pre
heading stage and having high grain filling
rate would made a genotype tolerant to late
heat to attain a high grain yield in wheat.
