Efficiency of assimilates and nitrogen remobilization in lines and cultivars of grain sorghum under drought stress conditioný.

The efficiency of assimilates and nitrogen remobilization in lines and cultivars of grain sorghum under drought stress condition studied in four locations (Mashhad, Neyshabour ,Esfahan and Birjand ) during 2011and 2012 cropping seasons. Statistical designe was split plot based on RCBD with three replications. Treaments were: Normal Irrigation and limited irrigation( just vegetative period) in main plots and a factorial combination of N( 0 and 200 kg N ha-1) and five sorghum cultivars and lines ( Sepideh, MGS5, MGS2, KGS29 and KGS34) in subplots.The results of combined analysis of variance for each location showed that effect of year on grain yield was significant in Esfahan and Naishabour and grain yied in second year was higher in all locations except in Birjand. The effect of moisture status on grain yield was significant (p0.01) only in Esfahan and yield decreased under stress condition .The effect of genotype on grain yield was significant (p0.01) only in Esfahan and MGS5 genotype had the heigest yield in all locations. Grain yield increased significantly by using nitrogen fertilizer in Mashhad and Neyshabour.In drought condition, parameters related to remobilization including Assimilate Remobilization Dry Matter(ARDM), Remobilization Efficiency(REE) and Remobilization Percent(REP) was icreased in all locations but was significant only in Esfahan . MGS5 and MGS2 promissing lines showed the highest grain yield and remobilization parameters respectively. Number and weight of kernels in panicle and ARDM increased by applying of nitrogen. Interaction effect of moisture status and genotype was not significant in the most locations and years but under drought stress condition relied to assimilate storage in stems and leaves befor reproductive stage was higher in all genotypes. Nitrogený Ã genotype Interaction was not significant on parameters related to remobilization parameters related to remobilization but response of genotypes to nitrogen consumption was different based on the year and location and genotypes showed considerable genetic variation for these parameters.