Abstract
A field experiment was carried out to evaluate the effects of different nitrogen levels on four promising bread wheat genotypes. The experiment was conducted at the farm of Field Crops Dept., College of Agricultural Engineering Sciences, University of Duhok in winter season 2020-2021. The experimental units laid out in factorial experiment with (R.C.B.D) with three replicates. Four genotypes were used (Bora, Jehan-99, AApast-36 and AApast-26) and four levels of nitrogen (0,75,150 and 200kg ha-1). The result revealed that the growth parameters respond significantly to nitrogen fertilizer. Application of nitrogen levels in combination increase yield, gave the highest grain yield 219.1 (g) at 200kg ha-1 nitrogen, also the highest grain (231 g) was recorded from AApast-36 genotypes. Among the interaction of nitrogen levels and wheat genotypes produced the highest grain yield (266.6g) per plant at 200kg N ha-1 and Apast-36 genotypes. The Apast-36 genotype was superior in flag leaf area 48.14 cm2, Number of seed per plant 42.8, weight of seed spike 1.88g and 1000-seed weight (43.73 g). So that this genotype can be considered an advanced line and can be placed in a breeding program. Most of the studied traits are highly correlated with yield such as 1000-seed weight (0.91), spike length 0.52 and number of seeds per spike 0.45 and it can be said that these traits are the important effective components in seed yield.
