Variation for Staygreen Trait and its Association with Canopy Temperature Depression and Yield Traits Under Terminal Heat Stress in Wheat

Abstract

Nine hundred and sixty three wheat advanced lines from various sources, including Indian and CIMMYT germplasm, were screened for the presence or absence of staygreen (SG) trait during two cycles, 2003–05. Staygreen was evaluated based on visual scoring (0–9 scale) and a new parameter, Leaf Area under Decline (LAUD). Approximately 5.5% of the lines were found to show staygreen character, 10.6% were moderately staygreen, and the remaining showed some or no expression of this trait. From this germplasm, one hundred lines were selected with the objective to find the effect of staygreen on yield and yield traits. These lines were sown under three different sowing dates (timely, late and very late) for three consecutive years to find the association between staygreen trait and heat tolerance. Canopy Temperature Depression (CTD), used as selection criteria for heat tolerance, was recorded at 12h, 14h and 16h at 7days interval, on bright sunny days. Correlation study showed that LAUD and CTD were strongly correlated (r=0.90) . LAUD was also found to be significantly associated with yield traits like grain filling duration (GFD) (r=0.83) , grain yield (r=0.89) , biomass (r=0.84) , but its association with test weight was non-significant. CTD also displayed significant correlation with yield traits like GFD (r=0.78) , grain yield (r=0.84) and biomass (r=0.81) . There was significant association between grain yield, biomass, and GFD under all the sowing dates but the association between CTD, LAUD and test weight was significant only under very late sown conditions. Genotype x Year interaction was found to be non-significant for LAUD and CTD. Genotype x Year x Sowing date was non-significant for LAUD but significant for CTD. T-test done to compare SG and non-SG genotypes was found to be significant for all the traits for both the years and under all sowing dates, except for test weight, under timely sown condition. This investigation revealed that substantial variation exists for SG trait in wheat and there is significant difference between SG and non-SG genotypes for CTD. Hence, SG trait along with CTD can be used as effective selection criteria for tolerance to heat stress