Genotypic variation in nitrogen use efficiency trait in 35 cucumber inbred lines

Nitrogen is an essential nutrient for plant growth and yield, however excess nitrogen fertilizer application can lead to detrimental environmental impacts. Identifying cucumber genotypes with high nitrogen use efficiency (NUE) could facilitate sustainable crop production through optimized nitrogen management. This study was conducted in March 2021 at the research greenhouse of Department of Horticultural Sciences, University of Guilan, Iran. The objective of this study was to assess growth, yield components, nitrogen accumulation, NUE, and nitrate reductase activity in 60 cucumber genotypes under sufficient (NS) and deficient (ND) nitrogen conditions. Nitrogen deficiency caused reductions in growth and yield across all genotypes, although the severity varied. Nitrogen content was higher in all plant organs under NS compared to ND. NUE and its components nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency (NUtE) were significantly higher under ND versus NS. Line 57 exhibited the best NUE and yield under both NS and ND, and could be considered a nitrogen-efficient genotype. Based on NUE performance, lines were categorized as efficient, semi-efficient, low-efficient, and inefficient. Nitrate reductase activity was higher in leaves versus roots, and positively correlated with NUE, suggesting a relationship between enzyme activity and nitrogen uptake efficiency in roots. This study demonstrates genotype-specific responses to nitrogen availability in cucumber. The identification of genotypes efficient in NUE, such as line 57, can inform breeding efforts to improve nitrogen responsiveness. Characterizing nitrogen responsiveness across genotypes also allows for optimized, genotype-specific nitrogen management recommendations to be made, facilitating sustainable crop production.