Abstract
A study including four experiments was conducted during 2015-16 to 2018-19, at BWMRI,
Regional Station, Gazipur to investigate the extent of genetic diversity for traits related to
drought tolerance, to assess relationship of yield/yield contributing morpho-physiological
and biochemical traits and to find out suitable criteria and method of selection. Firstly, 300
wheat genotypes were field screened under optimum irrigation and rainfed condition. Under
stress PHT, DTH, DTA, DTM, GFD. FLA, PL, BMP; and AL, TGW, TGP, GFR, SPAD value
and HI reduced significantly while CT was increased. Moderate to higher estimate of h2 along
with GCV, PCV and GA (%mean) suggested improvement through direct phenotypic
selection for PHT, DTH, DTM, GFD, BMP, GY and TGW is feasible. Under control BMP, GY
and PHT had maximum contribution to PC1 and PC2, whereas, CTveg, CTgf and DTH
contributed the major portion under stress. Non-hierarchical clustering distinguished 300
genotypes into 7 clusters. Based on PC1 and PC2 scores G 89, G 29, G 27, G 82. G 45, G 235, G
117, G 36, G 90, G 32, G 88, G 264, G 93, G 92, G 41, G 210, Prodip, G 270, G 91, G 238, G 152, G
209, G 229, G 253, G 56, G 26, G 16, G 160, Bijoy and G 65 found as to be tolerant and G 43, G
165, G 241, G 108, G 216, G 167, G 170, G 51, G 248, G 70 as sensitive. Based on relative value
and percent yield reduction genotypes were categorized into 4 groups. ARP of the drought
tolerance indices viz. MP, GMP, STI, SSI and TOL gave better opportunity for selection. Based
on ARP values G 82, G 229, G 65, G 242, G 295, G 29, G 235, G 85, G 251, G 123, G 36, G 37
were proved as to be tolerant while G 51, G 189, G 170, G 167, G 70, G 108, G 248 as
susceptible. A 2nd experiment, comprising of 30 selected genotypes from Expt. I, was
conducted to investigate the water status of genotypes and also to assess their relationship
with yield and yield traits. Correlation study revealed that RWC, WRC, XER along with CT
and NDVI could better explain yield under stress. Based on water status results G 295, G 85,
G 82, G 91, G 235, G 29, G 117, G 32, G 210, Bijoy, Prodip and G 89 found as to be tolerant
whereas G 167, G 189, G 70, G 51, G 170, G 248 and G 108 as susceptible. These results were in
accordance with the findings of Expt. I. In the 3rd expt. 10 selected genotypes from expt. II
were tested in lab. condition under 4 different water regimes induced by PEG 6000 viz.
control, 10, 15 and 20% PEG solutions to assess the suitable evaluation criteria at germination
and early seedling stages. Based on different seedling parameters genotypes G 85, G 295, G 89
found to be most tolerant whereas G 167 and G 189 were the most susceptible. These results
were in accordance with the findings of expt. I and II. The 4th experiment was carried out to
assess the growth parameters as well as morpho-physiological and biochemical aspects of
drought tolerance in 5 selected wheat genotypes both under field and laboratory condition. G
295 performed better regarding CGR, NAR, TDM and SDW under stress, whereas, G 189 was
poor. Cell membrane injury increased by 37.5, 33.7, 18.8, 12.1 and 10.2% in the G 167, G 189,
Prodip, G 85 and G 295, respectively. G 85, G 295 and Prodip accumulated the maximum
amount of SS under stress. Maximum proline accumulation was observed in G 85 (5.87 mg g
1DW) which was followed by G 295 (5.78 mg g-¹DW). Minimum 12.5% increase for H2O2 was observed in G 295. Maximum 16.2% increase of CAT activity was observed in G 295 which
was followed by G 85 (13.7%) and Prodip (11.2%). Reduction in CHLa and CHLb contents
was minimum in G 295 and G 85, respectively. Under water deficit condition, the maximum DMT from leaf, sheath, stem and chaff was recorded in G 295 which was followed by Prodip
and G 85. The CCPn as recorded ranged from 1.84 to 0.78% in Prodip, from 1.92 to 0.76% in G
85, from 1.63 to 0.57 in G 167, from 1.68 to 0.58 in G 189 and from 1.73 to 0.76% in G 295
under control and water deficit conditions, respectively. Based on results obtained G 295 and G 85 found to be the most tolerant.