Morpho-Phenological Traits as an Index of Screening Wheat Genotypes for Thermotolerance

Field and laboratory experiments were carried out at Punjab Agricultural University, Ludhiana to screen suitable parameters for thermotolerance in wheat cultivars. Four wheat cultivars namely PBW-502, PBW-343, WH-542 and PBW-509 were sown at six dates at weekly interval starting from 30^th October to 4^th December. The growing degree days were accumulated more under 30^th October sowing (1815.82) than 4^th December (1502.89). The path coefficient analysis revealed that the direct effect of grain weight (P₅₇= 0.3815) followed by number of spikes m⁻² (P₂₇= 0.3483) on yield was more as compared to number of grains spike⁻¹ (P₄₇= 0.0744). These results showed that thermal use efficiency, grain filling period, spikes m⁻², grain-spike weight ratio, test weight can be used as an index for screening thermotolerance in wheat cultivars.