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Abstract
In Egypt, barley (Hordeum vulgare) is mainly grown in the rainfall areas of < 200 mm of the northwest coast and northern Sinai peninsula and gives an average grain yield ranging from 2.58 to 4.58 ard./fad. under such natural drought conditions. Plant breeders should develop more drought tolerant varieties of barley than the existing ones to increase their productivity under the rainfed areas in Egypt. To start an efficient breeding program for developing drought tolerant varieties of barley, information are needed to identify the proper parents for such program and to determine type of gene action controlling the inheritance of grain yield and important attributes under water deficit conditions.
The objectives of the present investigation were to: (i) determine the effect of drought stress on some important characters of 6 barley genotypes and their diallel F1 crosses, (ii) estimate the combining ability variances and effects, and heterosis for the studied traits under drought stress and non-stress conditions and (iii) identify the best genotypes for potential usefulness in the barley breeding programs for improving drought tolerance.
Six genetically diverse genotypes of barley were used as parents for making all possible F1 crosses (excluding reciprocals) in 1999/2000 growing season, at Giza Res. Sta. of the ARC. In 2000/2001 growing season, the parents (6) and the F1’s (15) were sown at the same Res Sta. at Giza in three evaluation experiments; the lit under full irrigation (three irrigations), the 2nd under moderate drought stress (only two irrigations) and the 3rd under severe stress (only one irrigation at planting time). The randomized complete block design with 3 replications was used for each experiment. Eight traits were recorded, viz days to 50% flowering, plant height, flag leaf area, spikes/plant, 100-grain weight, grain yield/plant, biological yield and harvest index.