Wheat cultivars differ in their response to nitrogen (N) fertilizer, both in terms of its uptake and utilization. Characterizing this variation is an important step in improving the N use efficiency (NUE) of future cultivars while maximizing production (yield) potential. In this study, we compared the agronomic performance of 48 diverse wheat cultivars released between 1936 and 2016 at low and high N input levels in field conditions to assess the relationship between NUE and its components. Agronomic trait values were significantly lower in the low N treatment, and the cultivars tested showed a significant variation for all traits (apart from the N remobilization efficiency), indicating that response is genotype-dependent, although significant genotype × environment effects were also observed. Overall, we show a varietal improvement in NUE over time of 0.33 and 0.30% year^–1 at low and high N, respectively, and propose that this is driven predominantly by varietal selection for increased yield. More complete understanding of the components of these improvements will inform future targeted breeding and selection strategies to support a reduction in fertilizer use while maintaining productivity.

An increased awareness of environmental protection and sustainable production raise the necessity of incorporating the selection of low nitrogen-tolerant winter wheat cultivars for high yield and quality in the breeding process. This selection can be assisted by using stress screening indices. Our study aimed to evaluate and compare a number of stress screening indices and to determine and select the most nitrogen deficiency-tolerant winter wheat cultivars for further breeding. The experiment included forty-eight winter wheat cultivars from eight different countries that were grown for two consecutive years at three different locations under low-nitrogen (LN) and high-nitrogen (HN) conditions. The results emphasized the importance of applying the appropriate stress screening indices in evaluating and selecting nitrogen deficiency-tolerant wheat cultivars. The promising stress screening indices were the mean productivity index (MP), geometric mean productivity index (GMP), harmonic mean index (HM), stress tolerance index (STI) and yield index (YI). They identified cultivars Sofru, BC Opsesija and MV-Nemere as the most tolerant cultivars to LN conditions for grain yield. The same indices classified U-1, OS-Olimpija, Forcali, Viktoria and BC Tena cultivars as the most tolerant to LN conditions for the grain protein content. Using the tolerance index (TOL), yield stability index (YSI) and relative stress index (RSI), the Katarina and Ficko cultivars were denoted as LN-tolerant cultivars in terms of the grain yield and Isengrain, Tosunbey, Vulkan and BC Darija in terms of the grain protein content.

Drought stress during germination and early seedling growth can impair soybean performance, while silicon nanoparticle (SiNP) seed priming may modulate early stress responses. This study aimed to evaluate the effects of SiNP seed priming on the germination, early seedling growth, and biochemical responses of 11 soybean (Glycine max (L.) Merr.) genotypes under non-stressed conditions and two levels of PEG-induced drought stress (5% and 10% PEG 6000), and to assess how these responses varied with stress intensity and genotype. Seeds were untreated, hydroprimed, or primed with SiO₂ nanoparticles at 500 or 1000 mg L⁻¹. Across genotypes and stress levels, priming generally increased germination energy and total germination and reduced non-germinated seeds, with similar improvements observed following hydropriming and SiNP priming, whereas normal seedling development was not consistently improved. Increasing stress strongly inhibited shoot elongation and seedling fresh mass, whereas root growth was comparatively maintained. SiNP priming generally resulted in higher seedling fresh mass, with SiNPs 500 producing higher values than the untreated control in most genotypes under mild stress and all genotypes under severe stress. SiNP priming also increased proline accumulation and total amylolytic activity, with SiNPs 1000 showing the highest values under mild and severe stress. Overall, SiNP seed priming most consistently improved soybean germination under PEG-induced drought stress, whereas its effects on early seedling growth and biochemical responses varied with nanoparticle concentration, genotype, and stress intensity.