CORRELATI ON STUDY ON SOME HEAT TOLERANT TRAI TS OF SPRI NG WHEAT (TRITICUM AESTIVUM L.) UNDER LATE SOWI NG CONDI TI ONS

Twenty five spring wheat genotypes were evaluated in three replicated trials under optimum and late sowing conditions during 2009-10 at Regional Wheat Research Centre, BARI, Gazipur Bangladesh. Effects of heat tolerant traits on grain yield and their association were studied in late sowing environment. Biomass and grain filling rate were found positively correlated (0.652**) with each other and also with grain yield (0.919** and 0.800**). The significant positive correlation of ground coverage with grain yield (0.478*) suggests that higher ground coverage at early stage will lead to increase in yield. Chlorophyll content of flag leaf both at anthesis and 21 days after anthesis showed significant negative association with canopy temperature (-0.487* and -0.570**, respectively) and grain filling rate (-0.506** and -0.570**, respectively) while it was found positively correlated with grain filling duration (0.538** and 0.508**, respectively). The association of anthesis days with grain filling duration (0.501*) and grain filling rate such that the genotypes would show tolerance to high temperature if it had filled grain at higher rate in a shorter time. Spikes number m -2 had highly significant positive correlation with grain yield (0.721**). Highly significant negative association (-0.649**) between grains number per spike and 1000-grain weight indicates a competitive demand of both sinks for photosynthates from a common source. Significant negative correlation of heat stress susceptibility indices with days to anthesis, ground coverage, biomass and grain filling rate suggests that these parameters can be useful for discriminating genotypes that have lower susceptibility to heat stress condition. The significant negative association with grain yield also offers solo importance in differentiating heat tolerant genotypes.