Screening of Some Syrian Wheat Varieties under Water Stress Conditions in Laboratory and Assessment Their Physiological, Biochemical and Grain Yield Differences in the Field.

This research work was carried out in the laboratory of Field Crops Research and laboratory of Biotechnology and Abu-Jarash Farm at Damascus University during the growing season 2009/2010, with the aim to explore the genetic variability of the response of ten wheat varieties to osmotic stress at seedling stage, as an effective and quick screening technique at laboratory level and their response to water stress under field conditions. In the laboratory experiment the response of investigated varieties have been evaluated to osmotic stress, to isolate the tolerant varieties from the sensitive ones at seedling stage by using the osmotic induction response technique (OIRT), in addition to study the importance of step-wise transfer in giving the induced seedling with sub-lethal level of stress greater ability to tolerate the lethal levels of stress itself. There was a genetic variability in the response of the investigated varieties to osmotic stress. It was noticed based on the roots and seedlings length and the percentage reduction of them, that the variety Bohooth 9 can be classified as a highly tolerant to osmotic stress due to its lower reduction in roots and seedlings length, while the varieties Cham 3, Hourani, Bohooth 8 and Bohooth 6 can be classified as moderately tolerant to osmotic stress, and the varieties Cham 10 as sensitive to osmotic stress. The results also showed that the average length of roots and seedlings was significantly higher in the omotically-induced seedlings and the decline in their growth was significantly lower compared with the non-induced seedlings, indicating the importance of increasing the efficiency of the seedlings to tolerate the lethal levels of the osmotic stress. With respect to field experiment at whole plant level, it was noticed significant genetic variability in the response of the studied wheat varieties to water stress applied only during the critical period of plant life cycle (flowering stage). It was noticed that the average leaf area index was significantly higher in the varieties Bohooth 9 and Cham1 (4.16, 3.62, respectively). while the average quantity of wax deposited on the leaves was significantly higher in the varieties Bohooth 6 and Cham 7 (0.779, 0.612 mg.cm-2, respectively). Among varieties which achieved the lowest percentage of solutes leakage was Doma 1 (ACSAD1105) (30.92%), while the variety Hourani has recorded significantly higher percentage of solutes leakage (76.01%). It was noticed that the amount of proline accumulated was significantly higher in the variety Bohooth6 (19.96 mg.g-1), followed by the variety Bohooth 9 (18.92 mg/g), while the minimum proline content was noticed in Doma 1 (13.91 mg / g). Statistical analysis results showed that the variety Bohooth 9 has achieved significantly the highest grain yield (289.17 g . m-2) followed with Cham1 (250.07 g . m-2) without significant differences compared by the other varieties, while the variety Hourani recorded significantly the least value of grain yield (204.02 gm-2). the variety Cham 7 has achieved significantly the highest biological yield (776.03 g . m-2) compared by the other varieties, while the variety Cham 10 recorded significantly the least value of biological yield (661.81 g . m-2).