Abstract: To evaluate yield, yield components and water use efficiency of bread wheat in water stress conditions and spraying of dessicant, a field experiment was carried out in 2006-2007 and 2007-2008. Main plots were assigned to two levels of water stress treatments; D1: optimum irrigation and D2: cessation of watering from anthesis to maturity stages. Sub plots were assigned to eight bread wheat genotypes; and assimilates limitations with two levels: P1: no source limitation and P2: inhibition of current photosynthesis were in sub-sub plots. Grain yield, biological yield, harvest index, the number of grains per spike, thousand grain weight and water use efficiency were significantly influenced by irrigation treatments and source limitation. Grain Yield (GY) significantly decreased by 35 and 68% under water deficiency and postanthesis photosynthetic inhibition, respectively; compared with control. Water use efficiency was higher for well-watered compared with postanthesis drought stress conditions. WUEgrain decrease due to water deficit was attributed to grain yield reduction. Under water stress, current photosynthetic inhibition reduced grain yield by 62%, but under well-watered condition; it significantly decreased grain yield by 71%, that indicate the source is limititing factor under different irrigation regimes. Considering that C-81-10, 9103 and 9116 genotypes showed the highest grain yield, potential for reserves and remobilizations of assimilates under different irrigation conditions; thus, these genotypes could be introduced as promising in breeding programs for arid and semi-arid regions.

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