A. Sanjari Pireivatlou - Agricultural Research Station of Ardabil, P. O. Box: ۳۵۱۵۶-۵۴۵, Ardabil, Islamic Republic of Iran.
A. Yazdansepas - Seed and Plant Improvement Institute, Karaj, Islamic Republic of Iran.

The responses of yield and yield components of ۲۴ advanced bread wheat genotypes to pre- and post-anthesis drought stress conditions were studied at Ardabil Agricultural Re-search Station during the ۱۹۹۷-۲۰۰۰ cropping seasons. Results showed that genotypes produced significantly lower spikes No./m۲, seeds No./spike and grain yield under pre- than in post-anthesis drought stress conditions. However, an average of ۱,۰۰۰ kernel weight of genotypes under pre-anthesis was higher than under non-stress and post-anthesis drought stress conditions. Selection based on TOL and SSI identified the drought tolerant genotypes with low grain yield. However, selection based on MP, GMP and STI identified drought tolerant genotypes with a high yield. Genotypes No. ۱۳, ۱۴ and ۲۱ were determined as desirable genotypes based on their high grain yield under non-stress, pre-anthesis and post-anthesis drought stress conditions. The interaction effect of genotype x year was significant for membrane stability and membrane damage, however, the interac-tion effect of genotypes stages of measurement (booting and heading) were not signifi-cant. On the basis of these results, genotypes No. ۱۳, ۱۴ and ۲۱ with low membrane dam-age were also identified as drought tolerant genotypes. It can be concluded that the labo-ratory test can be an useful tool in a breeding program for improving drought tolerance in wheat.

Bread wheat, Drought Stress, Grain yield