Response of selected Genotypes of Sunflower under Different Nitrogen Levels

Abstract A field experiment was conducted to improve the nitrogen tolerance characteristics of Sunflower using the 8 genotypes selected from Shamus and Local varieties and sown in split-plot design(RCBD) with three nitrogen fertilization levels (50, 100, 200) N kg/hectare at the university of Baghdad 2022-2023. Results showed that there were significant differences between nitrogen fertilizers quantities and the genotypes and the (SHD-selected) gave the highest peroxidase (POD) activity (34.23 and 16.73 U/mg)for all seasons spring and fall. While, the SHC-variety gave the lowest value of peroxidase (POD) activity about (11.94 and 9.80 U/mg) under for all season spring and fall respectively. The nitrogen fertilizers caused increasing in superoxide dismutase (SOD) activity, whereas. The LD-selected gave the highest average of catalase (CAT) under three nitrogen fertilizer levels (3.67, 7.03 and 10.67 U/mg), but the LD-selected genotype, which showed activity of catalase (CAT) About (4.80, 5.17 and 18.01U/mg), under nitrogen levels at the spring and fall seasons respectively. In addition to, the LF-selected gave the highest average of peroxidase (POD) activity (7.75,20.40 and 21.40) to spring season and (24.58, 30,10 and 32.30) to fall season respectively. There are significant between nitrogen levels and genotypes in the LF-selected on chlorophyll content (518.57 and 640.01 mg/m 2 ), for two season respectively. We conclude that the increasing of N-levels caused increasing of anti-oxidant enzymes activity and less Reactive oxygen species (ROS) and enhance of the productivity because of N-molecule entire in synthesis of Amino acid and protein of the cells.