Abstract
Twenty-five genotypes of wheat were studied under different moisture regimes in both pot and
field conditions to screen these for drought tolerance during 2000-01 cropping season. The pot
and field experiments were conducted at the farm of Bangladesh Institute of Nuclear Agriculture
(BINA) and field laboratory of Genetics and Plant Breeding Department, Bangladesh
Agricultural University, Mymensingh, respectively. The moisture stress treatments were 80, 55
and 30% field capacity (FC) under pot condition. Under field condition, the moisture regimes
consisted of irrigated, rainfed and stress (protected from rain and dew) treatments. The genotypes
Shatabdi, Kanchan, BAW-969 and BAW-56 appeared to be tolerant to moisture stress due to
having higher absolute growth of plant height, total tiller, leaf area index, total dry matter, dry
matter stress index, yield stability and lower drought susceptibility stress index values resulting
in higher grain yield under water deficit condition. Considering the results of growth and drought
indexing parameters in both pot and field conditions, the genotypes Shatabdi and Kanchan were
graded as tolerant; BAW-969 and BAW-56 were moderately tolerant and the remainders were
susceptible to moisture stress. The detailed mechanism of drought tolerance studies in both pot
and field conditions during 2001-03 cropping seasons demonstrated that the most tolerant
genotypes Shatabdi and Kanchan accumulated more cellular osmolytes like soluble protein, total
amino acid, leaf proline and reducing sugar resulting in more reduction in 4100 450 and RWC
but higher RWD of leaf as compared to susceptible Agrani under Stress condition. Both
genotypes Shatabdi and Kanchan also maintained noon values (Shatabdi =-23.1 bar,
Kanchan=-22.7 bar) above ys values (Shatabdi =-23.1 bar, Kanchan= -22.7 bar) under 30% FC
treatment. The genotypes Agrani and BAW-944 suffered from turgor loss during peak stresses
and both genotypes showed declining u, values concomitantly to –16.80 bar and – 17.9.00 bar,
respectively which were less negative than their values (Agrani=17.5 bar, BAW-944=18.4
bar) under 30%FC condition in 2001~02 experiment and the trend was similar in 2002-03. This
result indicated that the degree of stress was higher which exceeded the capability of leaf
osmotic adjustment within those genotypes. Studies of transpiration declining components
during 2001-02 and 2002-03 years resulted in that Shatabdi and Kanchan also had lower STR
and CTR maintaining longer time to close stomata and maintaining lower RWC value under 30
% FC indicating indirectly its capability of osmotic adjustment to drought. This suggests that
those genotypes sustained transpiration and thereby dry matter gain even when RWC was too 14 low under stress condition. The translocation studies with c isotope resulted in the similar
ability of translocation of assimilates in all genotypes under 80% FC' treatment. But under 30
%FC, the genotypes Shatabdi, Kanchan and BAW-969 could translocate higher amount of 14C
assimilate from the fed leaf after 48 hours of exposure. The susceptible one Agrani translocated
slowly and little labelled assimilate towards stem and grain under drought condition. In multiple
regression studies, the parameters like number of fertile tillers, number of grains, weight of 1000
grains, LAI, total chlorophyll, NR activity, dry matter, RWC, leaf water potential, SLA, LAD,
HI, soluble protein, amino acid, leaf proline and reducing sugar showed significant regression
co-efficients with yield. Two years drought management studies in farmers' field of
Chapainowabgonj, Magura and Rangpur districts during 2001-02 and 2002-03 exhibited that
poly mulch was very much effective in altering and conserving longer time the residual soil moisture and
it caused higher yield.