PHYSIO-AGRONOMIC TRAITS EVALUATION OF WHEAT GENOTYPES FOR ADAPTABILITY UNDER RAINFED CONDITIONS

High temperature stress during grain filling stages is one of the main wheat yield limiting factors under rainfed conditions of Pakistan. A field experiment was carried out to evaluate physio-agronomic traits of different wheat genotypes for better yield and heat tolerance under rainfed conditions. Variable growing conditions during grain filling period were created by sowing crop on normal (November 15) and late sowing dates (December 15). Crop planted on normal sowing date had significant affect (p 0.05) and produced 29% higher grain yield as compared to late planting. Significant variation (p 0.05) was also noticed among genotypes in terms of physiological and agronomic traits under both under both normal and late sowing dates, as advance line NR-397 and NARC-09 produced significantly higher (p 0.05) grain yields as compared to NR-400 and NR-379. Higher grain yields of these two cultivars were associated with their more number of days to maturity, higher spikes m^2 and heavier grains as compared to other two genotypes. At the same time, grain yields of wheat genotypes showed a strong correlation to their leaf chlorophyll (+0.98) and canopy temperature (-0.99) measurements. Higher grain yields of NR-397 and NARC-09 were directly correlated to their better leaf chlorophyll retention and maintenance of low canopy temperature during grain filling periods.