Abstract
Most of investigations showed that nitrogen fertilizers gave substantial rapeseed yield increases even in diverse and contradicting conditions but in a few studies were focused on nitrogen deficiency stress effects. Some of important seed yield stress indices based on application and non application of nitrogen (N+ and N0) was studied using six spring rapeseed varieties and their 15 F2 progenies. Significant mean squares of genotypes effects were observed for potential yield (Yp), stress yield (Ys), mean productivity (MP), geometric mean productivity (GMP), tolerance index (TOL), stress tolerance index (STI) and stress susceptibility index (SSI), indicating significant genetic differences of the genotypes for the stress indices. The genotypes including PF7045/91 and RGS003 had the high mean values of MP and GMP and STI, therefore considered as high potential parents in both nitrogen application conditions. On the basis of low mean value of TOL and SSI indices, PF7045/91 and 19H were considered as tolerant to nitrogen deficiency stress. Most of the crosses with high mean values of MP, GMP and STI had at least one parent with high mean values of these stress indices. Significant positive correlation of Yp and Ys with MP, GMP and STI, indicating selection based on these stress indices will increase the Yp and Ys of the genotypes. Heterozygosity had important role for stability of traits in different conditions, therefore in compare to parents their F2 progenies had low mean values of SSI and TOL indices