Screening of bread wheat cultivars (Triticum aestivum L.) to water deficit stress under field conditions

Field trial was conducted during the growing season of 2011-2012 at the Research Field, Department of Biology, College of Science, Baghdad University to test the performance of wheat cv Rabyaa, Latifiya, Al-Iraq, Tummose 2, Abu-Graib 3, IPA 99 and Sham 6 grown under different soil water deficit stresses. Several agronomic and physiological traits and yield and yield components of the test cultivars were determined. The experiment was conducted in split plot design with five replications for each treatment. The cultivars were kept in the sub plot while water stress treatment was assigned as main plot. Water stress was applied by irrigated the plots to the soil field capacity (FC) then withheld next irrigation until the soil moisture of the respective plots depleted to 50 (control), 25 and 15% of FC. Results indicated that the water deficit stress significantly reduced biological yield, grain yield and yield components, plant height and number of tillers. Also, drought significantly reduced leaf area and chlorophyll content and increased proline accumulation of the all test cultivars. In most cases, the reduction increased with the increased water stress. The results also showed significant differences among the test cultivars in most of the aforementioned parameters. Under higher drought stress, cultivars Rabyaa, Latifiya and Abu-Graib 3 were superior in grain and biological yields and most of yield components (number of spikes/m2, number of grains/spike and 1000-grain weight) compared to other cultivars including Sham 6 and IPA 99 which recorded lower values of these traits. Subsequent analyses revealed the drought tolerant cultivars (Rabyaa, Latifiya and Abu-Graib 3) showed increased with high significant in grain and biological yields, yield components, plant height, number of tiller, leaf area, accumulation of proline and total chlorophyll content than non-tolerant cultivars (Sham 6 and IPA 99). This suggests that the these characters are useful criteria that may be used for screening wheat genotypes for drought tolerance