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International audience; Durum wheat culture requires a high fertilization rate to achieve sufficient protein concentration for semolina and pasta quality, contributing to losses through atmosphere and water. Optimizing plant capacity to use N could help improve its agroenvironmental balance Our objective was to study the impact of the marine extract DPI4913 and the fungal extract AF086 on growth, N absorption and fluxes in durum wheat.Three experiments were conducted in France: under standard N 25 fertilization in a first field (Carbonne, 43.333328 N, 1.33333 E), under varying N supply in a second field (Mervilla, 43.503451 N, 1.472316 E) and under varying water conditions in greenhouse (Toulouse, 43.527272 N, 1.501492 E). Various 15N labelling experiments were performed at flag leaf fully emerged stage to follow N fluxes until maturity. In Carbonne, 15NO3- and 15NH4+ were injected in the soil to investigate the effect of biostimulants on allocation to grains of soil mineral N. In greenhouse, some plants were 15NH4+ labelled on the flag-leaf to follow N remobilization. For other plants, flag-leaf was removed at flag-leaf fully emerged stage to characterize flag-leaf implication in N translocation to grains. Flag leaf senescence was studied estimating leaf chlorophyll concentration with the SPAD-502 meter. Under standard N conditions, biostimulants increased mean grain yield in the field (+1.8 % for DPI4913 and 4.0 % for AF086 in Carbonne; +5.5 % for DPI4913 and +3.9 % for AF086 in Mervilla; not significant). In greenhouse, under water standard conditions, biostimulants increased grain yield (+19.7% for DPI4913, +19.3 % for AF086), total N in plant and in ear (respectively +28.9 % and +44.6 % for DPI4913, +23.3 % and +32.7 % for AF086) and proportion of N in the ear (68.7 % for CONTROL, 77.1 % for DPI4913, 74.2 % for AF086). Biostimulants had no effect under N and water stress conditions. In the field, DPI4913 increased soil mineral N accumulated in grains at maturity (15N labelling). In greenhouse, flag leaf N was very mobile (15N resorption of 98.2 %). Biostimulants increased the proportion of 15N applied to the flag leaf recovered in grains (40.9 % for Control, 52.5 % for DPI4913, 47.2 % for AF086, p-value=0.09) and accelerated leaf senescence (SPAD-measurements). Flag leaf key-role in grain filling processes was revealed by the fact that flag leaf ablation decreased N amount in grains more than flag leaf N content at the time of ablation (respectively - 5.9 mg and - 2.7 mg). The increase in N remobilization from flag leaf represented 4.3 % of the supplementary amount of N found in grains for plants treated with DPI4913 and 0.6 % with AF086. Biostimulants mainly increased mineral N root uptake rather than remobilization. In conclusion, it is suggested that DPI4913 and to a lesser extent AF086 – which promote plant growth, N uptake and remobilization – could be used in standard N and water conditions to optimize durum wheat N fertilization.

Le blé dur est caractérisé par une forte demande en azote pour atteindre le niveau de protéines requis pour la transformation en pâtes et semoules de qualité, ce qui contribue à un niveau de fertilisation azoté élevé et à des pertes d'azote par lixiviation ou volatilisation. L'optimisation de l'efficience d'utilisation de l'azote par la plante par apport de biostimulants pourrait constituer une alternative d'amélioration de la production de blé dur et du bilan agro-environnemental de la culture. Les actions bénéfiques des biostimulants à base d'extraits d'algues, d'acides aminés ou de protéines extraites de champignons ont été décrites sur l'augmentation de production de biomasse des plantes, le rendement, l'absorption d'azote et la résistance aux stress abiotiques. Bien que ces effets aient été décrits pour diverses cultures, peu d'études ont été réalisées sur le blé dur, et encore moins sur les flux d'azote dans la plante et le contenu protéique du grain. Dans ce travail, le biostimulant d'origine algale DPI4913 contenant un mélange d'acides aminés et le biostimulant d'origine fongique AF086 ont été testés en application foliaire sur blé dur au champ et en serre. L'étude de leurs effets sur le rendement en grains et la biomasse produite, à trois stades d'application en conditions de contraintes hydrique ou azotée, a permis de déterminer les conditions d'application optimales de ces produits : au stade deux noeuds en conditions d'irrigation et de fertilisation non limitantes. L'analyse du contenu en azote de la plante à maturité a montré une augmentation de la quantité d'azote prélevé par les plantes traitées et de l'allocation de l'azote vers l'épi, au détriment des autres compartiments. Le suivi des flux d'azote dans la plante par marquage foliaire (15NH4+) ou racinaire (15NO3- et 15NH4+) a montré des tendances pour les deux biostimulants à améliorer le prélèvement d'azote minéral racinaire ou foliaire, et sa migration vers le grain. L'apport combiné de biostimulants et d'un fertilisant azoté foliaire contenant de l'urée marquée a permis de mettre en évidence un effet positif des biostimulants sur la migration d'azote issu du fertilisant vers le grain, mais pas sur l'absorption foliaire du fertilisant. Les effets de DPI4913 et AF086 sur le rendement en grains et l'allocation de l'azote vers le grain se traduisent par une augmentation de la quantité en protéines du grain, sans effet sur la teneur en protéines. A cette augmentation de la quantité de protéines dans le grain s'ajoute une modification de la composition en protéines. Les plus fortes variations constatées concernent l'expression de protéines impliquées dans la dureté du grain, dans le stockage avec une forte surexpression de la gamma-gliadine, dans les processus de régulation avec la surexpression de protéines impliquées dans la régulation de la transcription, et dans la réponse aux stress avec la surexpression de protéines impliquées dans la réponse aux stress biotiques et abiotiques.

Durum wheat culture requires a high fertilization rate to achieve sufficient protein concentration for semolina and pasta quality, contributing to losses through atmosphere and water. Optimizing plant capacity to use N could help improve its agroenvironmental balance Our objective was to study the impact of the marine extract DPI4913 and the fungal extract AF086 on growth, N absorption and fluxes in durum wheat.Three experiments were conducted in France: under standard N 25 fertilization in a first field (Carbonne, 43.333328 N, 1.33333 E), under varying N supply in a second field (Mervilla, 43.503451 N, 1.472316 E) and under varying water conditions in greenhouse (Toulouse, 43.527272 N, 1.501492 E). Various 15N labelling experiments were performed at flag leaf fully emerged stage to follow N fluxes until maturity. In Carbonne, 15NO3- and 15NH4+ were injected in the soil to investigate the effect of biostimulants on allocation to grains of soil mineral N. In greenhouse, some plants were 15NH4+ labelled on the flag-leaf to follow N remobilization. For other plants, flag-leaf was removed at flag-leaf fully emerged stage to characterize flag-leaf implication in N translocation to grains. Flag leaf senescence was studied estimating leaf chlorophyll concentration with the SPAD-502 meter. Under standard N conditions, biostimulants increased mean grain yield in the field (+1.8 % for DPI4913 and 4.0 % for AF086 in Carbonne; +5.5 % for DPI4913 and +3.9 % for AF086 in Mervilla; not significant). In greenhouse, under water standard conditions, biostimulants increased grain yield (+19.7% for DPI4913, +19.3 % for AF086), total N in plant and in ear (respectively +28.9 % and +44.6 % for DPI4913, +23.3 % and +32.7 % for AF086) and proportion of N in the ear (68.7 % for CONTROL, 77.1 % for DPI4913, 74.2 % for AF086). Biostimulants had no effect under N and water stress conditions. In the field, DPI4913 increased soil mineral N accumulated in grains at maturity (15N labelling). In greenhouse, flag leaf N was very mobile (15N resorption of 98.2 %). Biostimulants increased the proportion of 15N applied to the flag leaf recovered in grains (40.9 % for Control, 52.5 % for DPI4913, 47.2 % for AF086, p-value=0.09) and accelerated leaf senescence (SPAD-measurements). Flag leaf key-role in grain filling processes was revealed by the fact that flag leaf ablation decreased N amount in grains more than flag leaf N content at the time of ablation (respectively - 5.9 mg and - 2.7 mg). The increase in N remobilization from flag leaf represented 4.3 % of the supplementary amount of N found in grains for plants treated with DPI4913 and 0.6 % with AF086. Biostimulants mainly increased mineral N root uptake rather than remobilization. In conclusion, it is suggested that DPI4913 and to a lesser extent AF086 – which promote plant growth, N uptake and remobilization – could be used in standard N and water conditions to optimize durum wheat N fertilization.