Influence of Low-N Stress, Genotype and Their Interaction on Grain Yield and Quality Traits of F1 and F2 Diallel Crosses of Wheat (Triticum AestivumL)

Developing high yielding varieties of bread wheat under low soil-N conditions is an important goal for plant breeder in order to overcome the negative impacts of using high rates of N fertilizers. This will lead to a significant reduction in nitrogen fertilizer use. The objective of this investigation was to study the effects of low-N environment (E), genotype (G) and G x E interaction on grain yield and quality traits of wheat F 1 and F 2 diallel crosses and their contrasting parents in N use efficiency. Genetic materials were evaluated at two seasons (2007/2008 and 2008/2009) in a split-plot design with lattice arrangement, using three replications. Main plots were assigned to N levels (0 and 75 kg N/fed), while sup-plots were devoted to genotypes. Data were analyzed across the two seasons. Low-N caused significant reductions in all studied grain yield components and grain protein content (GPC) in parents, F 1 's and F 2 's. The lowest reduction occurred in harvest index (HI), while spikes/plant (SPP) showed the greatest reduction, indicating that SPP is the most determinant component of GYPP. The first three parents L25, L26 and L27 showed significantly higher means than the second three parents Gem7, Gem 9 and Gz168 for most studied grain yield components and GPC trait. The F 1 and F 2 crosses involving one or more of the first three parents showed higher values of one or more of grain yield component traits than crosses that involved parents of the second group. In general, F 1 crosses showed higher means for all studied grain yield and quality traits than their parents. The rank of crosses in F 1 and F 2 generation for most studied traits was changed from one environment (N-level) to another, indicating a significant G x N interaction. Some F 2 -progenies under N-limited environment exhibited higher values of GYPP and HI, suggesting transgressive effects in these characteristics, and that selection practiced in such F 2 populations could be effective in developing low-N tolerant genotypes.