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Abstract
Nitrogen (N) is one of the major inputs in wheat production systems. Low-N availability in soils in Egypt is an important yield- limiting factor frequently found in farmers{u2019} fields. A set of promising lines and commercial varieties of wheat with obvious diversity in low-N tolerance were used in present study as parents of diallel crosses in F1 and F2 generations to study the inheritance of adaptive traits to low-N stress. selection was also practiced in F2 populations of the diallel crosses in order to develop tolerant genotypes to low-N. The F1 and F2 crosses were made in 2005/2006 and 2006/2007 seasons, respectively. selection was done in 2006/2007 season and evaluation of F1’s, F2’s and F3 selected families was done in 2007/2008 and 2008/2009 at Noubarya Res. Sta. of A.R.C., Egypt. A split plot design in lattice arrangement with 3 replications was used, where main plots were devoted to N levels (low; 0 kg N/fed and high; 75 kg N/fed) and sub-plots to wheat genotypes. Fourteen agronomic, yield and nitrogen use efficiency traits were measured and analysed under low (LN) and high (HN) nitrogen environments. Combined date across the two seasons were presented and discussed. Low-N caused a significant reduction in grain yield components and grain protein content (GPC), but caused a significant increase in NUE components. Both parents and crosses (F1’s and F2’s) exhibited great variability in most studied traits under LN and HN. The parents L26 and L27, F₁’s No. 6 and 7 and F₂’s No. 1 and 12 were N-efficient at LN and N-responsive at HN; they could be considered useful germplasm in future breeding program