Effect of Late Planting Heat Stress on Yield, Yield Components and Tolerance Indices in Barley (Hordeum vulgare L.)

The effect of late planting heat stress on yield and yield components was studied in 11 barley lines from ICARDA and one cultivar from Iran (Izeh) during two years (2005-2007) in Gachsaran Dry-land Agricultural Research Station. Each line was planted in a 6-rowed plot at two dates: normal planting (middle of November) and late planting (end of December) with three replications using a randomized complete block design. Results showed that heat stress (late planting) significantly decreased the number of spikes per unit area, grains per spike, thousand-grain weight and grain yield by 25.2%, 6.3%, 3.6% and 34.8%, respectively, while grain filling period did not show a significant reduction under heat stress. The number of days to heading showed the highest correlation with yield (-0.65). Mean product (MP), geometric mean productivity (GMP) and stress tolerance index (STI) were the best tolerance indices showing the highest correlation with grain yield under both normal and heat stress conditions. Based on two years data of STI, GMP, MP and yield, line 6 turned to be the most tolerant line and could be recommended for cultivation in tropical areas of Iran.