Accumulation of Photosynthesis Assimilates in Grains of the Recombinant Inbred Lines Population of Bread Wheat Derived from Cross Between Azar 2 and 87Zhong 291 under Drought Conditions

In order to study drought tolerance in bread wheat, 142 recombinant inbred lines in F8 generation, derived from a cross between Azar 2 (winter type) and 87Zhong 291 (facultative type) was used. Experiment was conducted in a randomized block design with three replications under drought stress and supplementary irrigation during 2006-07 cropping season, at Maragheh Experimental Station of the Dryland Agricultural Research Institute. Analysis of variance revealed significant differences among genotypes for different agronomical and physiological traits in two experimental conditions. Average of grain yield under drought and irrigated conditions were 928 and 2547 kgha-1, respectively. Under drought and irrigated conditions, grain yields ranged from 272 to 1935 kgha-1 and 1086 to 3805.4 kgha-1, respectively. Accumulation of photosynthesis assimilates in grains were 10.64, 24.89, 52.61 and 11.86 percent in the first, second, third and fourth weeks after anthesis, respectively, under drought condition. More than 88 percent of photosynthesis assimilates, accumulated in the third week after anthesis. Correlation coefficients of grain weight with grain filling rate in the first and second weeks after anthesis were r=0.76** and r=0.048* respectively. In most of the lines, total photosynthesis assimilate accumulation finished in the third week after anthesis. The results indicated that traits such as date to heading, date to anthesis, 1000 kernel weight and grain filling relative were important selection criteria for drought tolerance in wheat breeding programs.