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Screening of drought tolerant varieties of wheat are important for ameliorating productivity of water scarce areas. Six wheat genotypes including two local checks were evaluated for drought tolerance against different osmotic stress levels induced by Polyethylene Glycol (PEG)-6000. Experiment was set in completely randomized design (CRD) with three replicates and four treatments [0, -0.5 MPa, -0.75 MPa and -1.0 MPa PEG concentrations]. Wheat genotypes Khirman and Chakwal-86 were employed as check varieties. Four test genotypes evaluated were SD-621, SD-222, NIA Saarang and 22-03. Data were recorded on various seedling parameters such as germination percentage, germination index, shoot length, root length, fresh and dry weight of shoot and root, chlorophyll contents (a and b) and ionic contents (K+ and Ca2+, and K+ /Ca2+ ratio). No seedling survived at -1.0 MPa osmotic stresses. Best results were illustrated by wheat genotypes SD-222 and SD-621 with 98.89% and 96.7% germination at -0.5MPa and -0.75MPa osmotic stress, respectively. NIA Saarang and genotype 22-03 also exhibited better results at moisture stress. Reduction in chlorophyll and ionic contents was occurred with rise in water deficit in all genotypes. These findings appreciate the future use of these genotypes for obtaining high yield in water sparse areas.

High temperature retards plant growth and development. Major objective of this study was to assess heat tolerant potencies of forty rice cultivars at seedling stage and check the effectiveness of salicylic acid (SA) in improving thermotolerance. Rice seeds were sown in plastic bowls containing sand and heat stress (45°C) was applied on 15-days old seedlings for 12 and 24 h in growth incubators. Growth related stress tolerance indices were used as screening tools.Among all, two heat sensitive (Rambir and DM 15-1) and heat tolerant (RP2 and DM1-30-15-04) cultivars were selected for SA studies. SA spray (100 mg L -1 ) was used on 15-days old seedlings and heat stress (45°C) was imposed on 19-days old seedlings for 12 h and 24 h. Growth (root and shoot lengths and fresh and dry biomasses) and biochemical attributes (nitrate and nitrite reductase, total soluble sugars, proteins, nitrogen, potassium, phosphorous and magnesium) were measured. Heat shock reduced seedling growth, enzymatic activities and mineral contents.However, SA enhanced fresh and dry biomass, concentration of organic and inorganic solutes in all genotypes under heat stress. SA improved thermo-tolerance in RP2 and DM1-30-15-04 genotypes. These heat tolerant genotypes have capability to give better seedling growth and stand establishment.

Wheat productivity is drastically affected by late sowing, as it faces high temperatures during grain filling which decreases the crop yield. In this experiment, several seed priming agents were used to improve performance of two wheat varieties under normal and late sowing regimes. Hydropriming, Osmopriming with 2% calcium chloride and hormonal priming with salicylic-acid (50 mg/L) used as seed priming treatments. All treatments resulted in better seedling establishment, physiological attributes, growth and yield as Salicylic-acid proved superior in synchronized seedling stand establishment by reducing time required for 50% emergence and mean emergence under both sowings. Overall, growth and yielding traits were improved in both varieties subjected to seed priming with salicylic-acid and CaCl 2 under normal and late sowings. Salicylic-acid and CaCl 2 priming showed highest proline, sugars, phenolics, chlorophyll and relative water contents in Sarsabz and Khirman, while hydro-priming gave maximum glycine-betaine and membrane thermo-stability. Sarsabz showed more tolerance against high temperature. Seed priming improved high temperature tolerance under late sowing; however, CaCl 2 and salicylic-acid priming remained more effective in mitigate drastic effects of high temperature by maintaining better growth and yield as well as improved physiological attributes in both varieties. These enhancers can give more production under adverse climatic conditions.

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