Performance of Grain Yield For Some Wheat Genotypes Under Stress By Chemical Desiccation

Wheat is the major cereal crop in Egypt and all over the world. The increasing gap between production and consumption necessitates increasing wheat production in Egypt. The exponential increasing in the Egyptian population together with the limited agricultural area, do not meet the recent requirements. To overcome this problem, developing new wheat genotypes, which suited to be grown under new reclaimed (Toskhi, Sinai .... etc) became more necessary. Thus, improving drought tolerance of wheat genotypes has long been a major challen ge of most breeding programes because water deficit during some part of the growing period are common in new reclaimed area. Breeding of drought resistance by selecting solely for grain yield may not be successful. Several physiological criteria for selecting resistant genotypes have been proposed. So, plant breeders have measured selected physiological parameters like ; relative water content, transpiration rate, osmotic pressure, stomatal frequency, proline accumulation and chlorophyll content for purpose of identifying selection criteria which would be used to screen wheat genotypes for drought tolerance. Moreover, yield and yield artributs are meausred in the studied wheat genotypes. Field evaluation and selection for drought tolerance in wheat genotypes is difficult. This is due to the variation in rain, temperature and other growing conditions. Hence, the need for a more homogenous controlled stress environment for evaluating drought tolerance in wheat is necessary.