| dc.description.abstract | The study was undertaken at the research farm and laboratory of Crop Physiology and
Ecology Department, Hajee Mohammad Danesh Science and Technology University
(HSTU), Dinajpur during November 2015 to April 2016 to study on phenology, heat-use
efficiency and yield performance of four wheat genotypes under normal and late growing
heat stress conditions. The experimental treatments included sowing conditions- normal
sowing condition (sowing at November 30), late sowing condition (sowing at December 30)
and four wheat varieties such as BAW-1170, BARI Gom 25, BARI Gom 26 and E 22. The
experiment was laid out in split plot design with three replications. Results revealed the
number of days for attaining different phenological stages, the requirement of heat unit
(GDD) and heat-use efficiency (HUE) were higher for normal growing condition compared
to late growing condition. Wheat genotypes BAW-1170, BARI Gom 25, BARI Gom 26
needed higher number of days, GDD and HUE for different phenological stages compared
to E 22 in both the sowings conditions. All the genotypes showed a common tendency of
higher PSR mobilization to grain under late growing high temperature stress condition.
Irrespective of growing conditions genotype E 22 showed higher pre-anthesis stem reserves
(PSR) mobilization to the final grain weight compared to BAW-1170, BARI Gom 25, and
BARI Gom 26. Genotypes BAW-1170, BARI Gom 25, BARI Gom 26 showed higher
canopy temperature depression (CTD) in both the growing conditions than the E 22. The
late sowing high temperature stress condition significantly reduced the flag leaf area,
chlorophyll and sugar content, plant height, spike length, number of spike per plant, number
of kernel per spike, grain weight per spike and 1000 grain weight, flag leaf proline.
Genotype BAW-1170 attained the highest flag leaf area, chlorophyll of flag leaf at 8 days
after anthesis, flag leaf sugar at 16 days after anthesis, plant height, spike length, number of
spike per plant, number of kernel per spike, grain weight per spike, 1000 grain weight and
flag leaf proline, whereas genotype E 22 showed the lowest value of those parameter at both
the sowing conditions. In these characters the relative performance was highest in BAW1170 and the lowest in E 22, whereas BARI Gom 25 and BARI Gom 26 showed
intermediate relative performance. Finally, in yield parameter, genotype E 22 showed lower
performances in both the growing conditions compared to other genotypes. At late growing
condition, the grain yield and biological yield of all genotypes were significantly reduced at
different magnitude compared to normal growing condition. Genotypes BAW-1170, BARI
Gom 25, BARI Gom 26 attained higher relative yield compared to E 22. From heat
susceptibility index it was observed that BAW-1170 and BARI Gom 26 were clearly lower
heat susceptible (S<1.0) in grain yield compared to other genotypes. The results of present
study suggested that greater growth duration minimize the changes in flag leaf chlorophyll,
proline content in flag leaf, less dependence on stem reserves mobilization, ability to
maintain a cooler canopy environment reflected on yield and important yield determinants
and those can be considered as selective criteria of heat tolerance in wheat. | en_US |
