Biostimulants could play an important role in agriculture particularly for increasing N fertilizer use efficiency that is essential for maintaining both yield and grain quality in bread wheat, which is a major global crop. In the present study, we examined the effects of mixing urea–ammonium–nitrate fertilizer (UAN) or urea with five new biostimulants containing Glutacetine® or its derivative formulations (VNT1, 2, 3, and 4) on the physiological responses, agronomic traits, and grain quality of winter wheat. A first experiment under greenhouse conditions showed that VNT1, VNT3, and VNT4 significantly increased the seed yield and grain numbers per ear. VNT4 also enhanced total plant nitrogen (N) and total grain N, which induced a higher N Harvest Index (NHI). The higher post-heading N uptake (for VNT1 and VNT4) and the acceleration of senescence speed with all formulations enabled better nutrient remobilization efficiency, especially in terms of N mobilization from roots and straw toward the grain with VNT4. The grain ionome was changed by the formulations with the bioavailability of iron improved with the addition of VNT4, and the phytate concentrations in flour were reduced by VNT1 and VNT4. A second experiment in three contrasting field trials confirmed that VNT4 increased seed yield and N use efficiency. Our investigation reveals the important role of these new formulations in achieving significant increases in seed yield and grain quality.

Wheat is one of the most important cereals for human nutrition, but nitrogen (N) losses during its cultivation cause economic problems and environmental risks. In order to improve N use efficiency (NUE), biostimulants are increasingly used. The present study aimed to evaluate the effects of Glutacetine^®, a biostimulant sprayed at 5 L ha⁻¹ in combination with fertilizers (urea or urea ammonium nitrate (UAN)), on N-related traits, grain yield components, and the grain quality of winter bread wheat grown at three field sites in Normandy (France). Glutacetine^® improved grain yield via a significant increase in the grain number per spike and per m², which also enhanced the thousand grain weight, especially with urea. The total N in grains and the NUE tended to increase in response to Glutacetine^®, irrespective of the site or the form of N fertilizer. Depending on the site, spraying Glutacetine^® can also induce changes in the grain ionome (analyzed by X-ray fluorescence), with a reduction in P content observed (site 2 under urea nutrition) or an increase in Mn content (site 3 under UAN nutrition). These results provide a roadmap for utilizing Glutacetine^® biostimulant to enhance wheat production and flour quality in a temperate climate.

Optimizing nitrogen use efficiency (NUE) could mitigate the adverse effects of nitrogen (N) fertilizers by limiting their environmental risks and raising agronomic performance. We studied the effects of VNT4, a derived formulation of Glutacetine^® biostimulant, mixed with urea-ammonium-nitrate solution (UAN) on the growth, N-related traits and agronomic performance of winter wheat (Triticum aestivum L.). The experiment was performed under six contrasting field conditions over two years in Normandy (France), including a site where ¹⁵N labelling was undertaken. Taking into account all the sites, we report that VNT4 significantly improved grain yield (+359 kg ha⁻¹), total grain N and NUE. VNT4 application improved growth during tillering and stem elongation (+10.7%), and N and ¹⁵N uptake between tillering and maturity (+7.3% N and +16.9% ¹⁵N) leading to a higher N accumulation at maturity (+9.3% N). This N mainly originated from fertilizer (+19.4% ¹⁵N) and was assimilated after the flag leaf stage in particular (+47.6% ¹⁵N). These effects could be related to maintenance of physiological functions of flag leaves as suggested by the enhancement of their nutrient status (especially S, Zn and Mo). The adoption of VNT4 as a UAN additive is an efficient agronomic practice to enhance wheat productivity under an oceanic temperate climate.

La France est le premier producteur européen de blé tendre (Triticum aestivum L.), une céréale majeure pour la filière semences et les secteurs agro-alimentaire et industriel. Cependant, il reste des marges d’amélioration du bilan agro-environnemental de cette culture céréalière vis-à-vis de ses besoins en azote (N) pour optimiser les rendements de manière durable et sans altérer la qualité de la farine conduisant par exemple à des intolérances au gluten. Dans ce contexte, ces travaux de thèse ont consisté (i) à étudier les effets d’un apport de formulations innovantes d’engrais azotés combinés à des biostimulants sur l’efficience d’usage de l’azote (EUA), le rendement et la qualité grainière (notamment le ionome et le protéome) sur le blé tendre en conditions contrôlées et de plein champ et (ii) à calibrer plusieurs outils de diagnostic (SPAD, XRF et NIRS) qui évaluent l’impact des biostimulants sur le statut nutritionnel de la culture et des traits de qualité de la graine.Cette étude a mis en évidence l’effet bénéfique des biostimulants à base de Glutacétine® sur l’EUA, le rendement et ses composantes notamment le nombre de grains grâce à une meilleure fertilité des épis. L’optimisation de l’EUA a permis d’accroitre l’azote total dans les grains en serre et au champ notamment pour VNT4 et la Glutacétine®. La qualité grainière a aussi été fortement modifiée par les formulations testées notamment avec la baisse de la teneur en phytates, des changements au niveau du ionome (Mn, Mo, B et Se) et du protéome (protéines impliquées dans la régulation de la synthèse des protéines, la réponse aux stress biotiques et abiotiques, les fonctions de stockage et les processus de germination). D’un point de vue agro-économique, VNT4 et la Glutacétine® ont permis de générer des revenus complémentaires et sur le plan agro-environnemental, VNT4 a évité la fuite de 55 unités d’azote au champ. En parallèle, les calibrations d’outils de diagnostic portables utilisables au champ ont permis de déterminer les teneurs en éléments des feuilles (N), de la farine (N, P, K, Mg, S, Ca, Fe, Zn et Mn) et des pailles (P, K, Mg, S, Ca, Fe, Mn et Ni). Plus particulièrement, le développement de la technologie NIRS portable a permis d’établir les équations de prédiction du rendement, du PS, du PMG et de la teneur en N du grain à partir de spectres de réflectance obtenus sur les feuilles drapeaux au stade floraison.