Association of canopy temperature depression with yield of durum wheat genotypes under supplementary irrigated and rainfed conditions

Abstract

The objectives of this study were to evaluate the ability of five selection indices to assess drought tolerance of durum wheat genotypes under a variety of environmental conditions and the relationships of canopy temperature depression (CTD) with drought indices. Eight durum wheat genotypes were planted in the rainfed and supplementary irrigation conditions for two years (2007-2009). Five drought tolerance indices including stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL), mean productivity (MP) and geometric mean productivity (GMP) were calculated. Canopy temperature depression (CTD) was used to estimate crop yield and to rank genotypes. CTD was measured at three stages, from the emergence of fifty percent of inflorescence (Zadoks Growth Scale54) to watery ripe stage (ZGS71). The results showed that the average values of CTD in durum wheat genotypes changed from 3.3 to 5.7°C at the ZGS69 stage. Genotypes in this stage (ZGS69) had highly significant differences and average of CTD showed that durum wheat canopy was the largest value in all ZGSs under both conditions. The significant and positive correlation of YP, MP, GMP, SSI, STI and CTD showed that these indices were more effective in identifying high yield genotypes under both conditions. Results also showed that CTD has played an important role to search physiological basis of grain yield of wheat, and can be successfully used as a selection criterion in breeding programs.