The experiment progressed to evaluate the effects of time nitrogen fertilizer application on the senescence of durum wheat and its association with grain yield and its components. The experimental treatments, set up in a split-plot design, used five durum wheat cultivars (Adnham, Grecale, Duma, Sardar, Svevo) as the main plots, and the time nitrogen fertilizer application (100% tillering, 100% stem elongation, and 50% tillering + 50% stem elongation stages) under two locations in Northern Iraqi conditions. The results of this study indicated that late senescence cultivars (Grecale and Svevo) produced the highest flowering date (123.89 and 123.61 days), number of spikes/m2 (267.2 and 265.6 spikes), number of grains/10 spikes (330.5 and 323.6 grains), grain yield g/m2 (532.2 and 511.6 g), and harvest index% (38.72% and 39.86%). Moreover, the time of nitrogen fertilizer application at the tillering stage (early application) influenced most of the studied traits. Finally, extending photosynthesis capacity during the grain-filling phases by delaying the rate of senescence could be a better approach to improving the grain yield of wheat cultivars.
Durum wheat (Triticum durum desf.), cultivars, senescence rate (SR), time nitrogen fertilizer application (TNFA), grain yield (GY)
Leaf senescence is a developmental process controlled by genetic and environmental factors, such as the dose and time of nitrogen fertilizer application. Together, stay-green and earlysenescence traits can be good strategies to improve the wheat grain yield. The stay-green trait can maintain the uptake and remobilize the nutrients, while the early senescence can avoid the stress conditions during grain-filling stages in wheat crops.