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Drought stress severely limits wheat production worldwide. Availability of moisture for crop during critical growth stages is one of the important factors that determine grain yield. An experiment was conducted with five wheat genotypes (HD 2987, K 7903, HI 1563, HD 2824 and HD 2967) and dates of sowing (15th and 30th November) and 2 moisture regimes (one irrigation at crown root initiation stage and completely rainfed) during rabi(dry) seasons of 2014–2015 and 2015–2016, in order to determine their potential in terms of physiological parameters viz., relative water content (RWC), membrane stability index (MSI), chlorophyll content, proline content, gas exchange parameters and yield attributes. Study revealed that the physiological traits viz., RWC, MSI and total chlorophyll content declined, while moisture-deficit stress indicator level (proline level) increased under rainfed condition across the wheat genotypes, at both the developmental stages (anthesis and A + 20 days). At both stages, genotypes HI 1563 followed by HD 2987 were able to maintain high RWC (69.5 and 65.1%; 68.7 and 65%), MSI (75.2 and 64.5%; 63.1 and 57.7%), chlorophyll content (4.7 and 2.6 mg g−1D.W.; 3.3 and 2.13 mg g−1D.W), respectively as compared to other genotypes. High RWC, chlorophyll content and photosynthetic rate are important for maintaining physiological efficiency under deficit moisture condition to harness optimum yield. Further, high RWC led to more osmotic regulation or less elasticity of tissue cell wall. Moreover, growth and yield attributes were significantly higher under one irrigation as compared to complete rainfed condition. Wheat variety ‘HD 2967’ produced significantly higher number of grains ear−1(44.75). The test weight ranged from 33.2 g in K 7903 to 35.6 g in HD 2824. Wheat sown on 15th November produced higher grain yield (2.9 t ha−1) as compared to 30th November sowing (2.7 t ha−1), but the difference was not significant. One irrigation at CRI stage produced significantly higher grain yield (3.26 and 3.18 t ha−1) as compared to no irrigation (2.52 and 2.30 t ha−1).

A field experiment was conducted under reproductive stage drought stress condition with the objective to determine the effect of water deficit stress on yield and yield attributes of 75 rice genotypes. The effect of drought stress on various physiological and biochemical traits associated with drought tolerance was also studies at reproductive stage in twelve promising genotypes selected on the basis of yield performance under stress condition. Result revealed that significant yield decline was observed almost in all rice genotypes grown under water deficit stress condition as compared to irrigated situation. Drought stress at reproductive stage caused reduction in relative water content (RWC) (31.57 %), membrane stability index (MSI) (25.8 %). grain yield (55.31 %), number of effective tillers (37.70 %), plant biomass (23.65 %), and increase in grain sterility (51.5 %) and proline content (55.9 %) in rice genotypes. However, the responses varied among genotype. Out of the twelve rice genotypes, IR 84895-B-B-127-CRA-5-1-1, IR 83387-B-B-40-1, IR 83376-B-B-24-2, IR55419-04 and IR 83373-B-B-24-3 showed superiority in terms of grain yield, 1000 grain weight, total plant biomass, RWC, leaf area index (LAI), MSI and proline content. Significant and positive correlations were observed between yield and physiological attributes like proline content, LAI, relative water content and plant biomass under drought stress condition. The current study indicated that the physiological and biochemical traits have direct or indirect effect on yield performance of rice genotypes under water stressed environment at reproductive stage.

Fourteen rice genotypes comprising of landraces, high yielding varieties (HYVs) carrying Sub1allele as well as without Sub1allele contrasting in their tolerance to submergence stress were evaluated for plant survival, growth and yield response under submergence stress during kharifseason of 2011 and 2012. Decline in yield was observed almost in all the rice genotypes grown under submergence stress as compared to control condition. Under short term submergence, rice genotypes carrying Sub1allele survived complete submergence up to 14 days, whereas genotypes without Sub1did not survive significantly and gave very low yield. The decline in yield in rice genotypes under stress (submerged) condition ranged from 1.5 to 97 %. Under control condition HYVs with and without Sub1allele showed non significant differences in grain yield, but showed an average yield advantage of more than 2.5 t ha−1over landraces. Non significant difference were observed in landraces for grain yield under submergence and control treatments indicating considerable submergence tolerance. Landraces and HYVs carrying Sub1showed higher survival percentage after submergence than the susceptible parents and check variety IR 42. Variance studies revealed significant differences among genotypes for yield attributing traits. Correlation studies revealed that genotypes with the capacity to maintain higher biomass, higher chlorophyll and higher starch and sugar concentrations after submergence had higher survival of seedling and grain yield. Present study suggested that submergence tolerance related genes from landraces like Atiranga, Gangasuili and Kalaputia apart from FR 13A need to be identified for introgression into HYVs for successful exploitation of low lying flood prone ecosystem.

Field experiment was conducted during the kharifseasons of 2011 and 2012 to evaluate the yield response of one hundred rice genotypes of the low land ecosystem under aerobic cultivation. On the basis of yield performance, ten best genotypes were selected and further evaluated for physiological traits under aerobic condition. Significant yield decline was observed in almost all the rice genotypes grown under aerobic condition in comparison to flooded condition. The yield differences between aerobic and flooded rice ranged between 18 and 73 %. Rice genotypes, IR 83867-B-B-250-3-1-1, IR 84887-B-155-40-1-1, IR 83920-B-B-277-2-1-1-1 and IR 83929-B-B-291-3-1-1 showed higher photosynthetic rate, stomatal conductance as well as chlorophyll content in comparison to national and regional check varieties. Promising genotypes under aerobic condition have higher grain yield, harvest index and low spikelet sterility. Study suggested that genotypes for cultivation under aerobic ecosystem can be selected on the basis of physiological traits.