Evaluation of physiological screening techniques for drought-resistant breeding of durum wheat genotypes in Iran

Abstract

This paper summarizes the results of a project aimed to evaluate the use of physiological traits (such as canopy temperature and chlorophyll content) in determining drought tolerance of durum wheat genotypes under a variety of environmental conditions. Six durum wheat genotypes were planted in rainfed and supplementary irrigation conditions in Gachsaran of Iran for two years (2007 to 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) and chlorophyll content (CHL) was used to estimate crop yield and to rank genotypes. CTD and CHL were measured at three stages from emergence of 50% of inflorescence (Zadoks Growth Scale54) to watery ripe stage (ZGS71). Genotypes G5 (OUASERL-1) and G6 (Stj//Bcr/LKS41CD94) were superior genotypes for both environments with high PC1 and low PC2 in biplot analysis. The results of genotypes CTD in ZGS69 stage and CHL in grain filling stage had high significant differences. The significant and positive correlation of MP, SSI, STI, CHL and CTD showed that these indices were more effective in identifying high yielding genotypes under both conditions and the result showed that CTD and CHL played important roles to search for the physiological basis of grain yield of wheat and CTD and CHL can successfully be used as a selection criterions in breeding programs. Key words: Canopy temperature, chlorophyll content, drought stress, durum wheat.