Nitrogen dynamics and fertilisation use efficiency: carry-over effect of crop limitation

Background and Aims Knowing the impact of cultural practices on nitrogen (N) dynamics in perennial crops is critical to promote N use efficiency. This study focused on the impact of crop regulation on the plant N dynamics, on the fruit N composition, and on the N fertilisation use efficiency. Methods and Results A large crop load gradient was set in a homogeneous plot of the grape cultivar Chasselas. Fertilisation in the form of 15N-labelled foliar urea allowed the measurement of N uptake and partitioning among plant fractions. Dry mass, carbon, and N dynamics were assessed over two consecutive seasons. Crop regulation did not affect grape N concentration at harvest. Both N uptake and root N mobilisation were reduced in response to crop regulation. Fertilisation efficiency was higher under high-yield conditions in terms of N uptake and grape N accumulation. The carry-over effects of crop regulation in the following year were highlighted. Conclusions Crop regulation strongly affects the overall plant N cycle, that is, uptake, distribution and release. Crop regulation improves must sugar concentration at harvest, while N concentration remained unchanged. The efficiency of N fertilisation varies greatly with crop load, which limits the interest of fertilisation under low-yield conditions. Significance of the Study These results contribute to the development of accurate nutrition models and sustainable cultural practices

Influence de couverts végétaux sut la qualité des raisins et des vins de Chasselas

Un essai de comparaison de couvertures végétales permanentes des inter-rangs a été mené de 2019 à 2021 au domaine expérimental d’Agroscope à Changins-Nyon (Vaud). Ont été comparés, à un témoin en non culture (sol nu), des couverts herbacés naturels ou semés, afin d’étudier leurs effets sur le comportement agronomique de la vigne et la qualité des raisins et des vins de Chasselas. En l’absence de contrainte hydrique, l’enherbement naturel ou semé de l’interligne n’a pas exercé d’influence prépondérante sur les composantes du rendement comme la fertilité des bourgeons, le poids des grappes et des baies, ni sur la vigueur des sarments par rapport au désherbage chimique du sol. La composition des baies (teneur en sucres, pH, acidité totale, acide tartrique et malique) à la vendange a été identique quel que soit l’entretien du sol. L’enherbement naturel et l’engazonnement de l’interligne avec des semis de couverts végétaux a entrainé une diminution de la teneur en azote assimilable des raisins par rapport à la non culture (sol nu). La teneur en NH 3 et en acides aminés primaires (a-aminés) des baies a été plus faible dans les variantes enherbées. A la dégustation, les vins issus des variantes enherbées ont présenté un bouquet plus discret et des notes d’amertume légèrement plus élevées que les vins issus de vignes conduites en non culture au sol. Les différences se sont essentiellement manifestées en 2 e et 3 e année d’expérimentation

Impact of crop load on nitrogen uptake and reserve mobilisation in Vitis vinifera

Nitrogen deficit affects both crop production and composition, particularly in crops requiring an optimal fruit N content for aroma development. The adaptation of cultural practices to improve N use efficiency (NUE) (i.e. N uptake, assimilation and partitioning) is a priority for the sustainable production of high-quality crops. A trial was set on potted grapevines (Vitis vinifera L. cv. Chasselas) to investigate the potential of crop limitation (via bunch thinning) to control plant NUE and ultimately fruit N composition at harvest. A large crop load gradient was imposed by bunch thinning (0.5-2.5 kg m(-2)) and N traceability in the plant was realised with an isotope-labelling method (10 atom % N-15 foliar urea). The results indicate that the mobilisation of root reserves plays a major role in the balance of fruit N content. Fertiliser N uptake and assimilation appeared to be strongly stimulated by high-yielding conditions. Fertilisation largely contributed to fulfilling the high fruit N demand while limiting the mobilisation of root reserves under high yield conditions. Plants were able to modulate root N reserve mobilisation and fertiliser N uptake in function of the crop load, thus maintaining a uniform N concentration in fruits. However, the fruit free amino N profile was modified, which potentially altered the fruit aromas. These findings highlight the great capacity of plants to adapt their N metabolism to constraints, crop thinning in this case. This confirms the possibility of monitoring NUE by adapting cultural practices

Corrigendum to: Impact of crop load on nitrogen uptake and reserve mobilisation in Vitis vinifera

Nitrogen deficit affects both crop production and composition, particularly in crops requiring an optimal fruit N content for aroma development. The adaptation of cultural practices to improve N use efficiency (NUE) (i.e. N uptake, assimilation and partitioning) is a priority for the sustainable production of high-quality crops. A trial was set on potted grapevines (Vitis vinifera L. cv. Chasselas) to investigate the potential of crop limitation (via bunch thinning) to control plant NUE and ultimately fruit N composition at harvest. A large crop load gradient was imposed by bunch thinning (0.5-2.5 kg m(-2)) and N traceability in the plant was realised with an isotope-labelling method (10 atom % N-15 foliar urea). The results indicate that the mobilisation of root reserves plays a major role in the balance of fruit N content. Fertiliser N uptake and assimilation appeared to be strongly stimulated by high-yielding conditions. Fertilisation largely contributed to fulfilling the high fruit N demand while limiting the mobilisation of root reserves under high yield conditions. Plants were able to modulate root N reserve mobilisation and fertiliser N uptake in function of the crop load, thus maintaining a uniform N concentration in fruits. However, the fruit free amino N profile was modified, which potentially altered the fruit aromas. These findings highlight the great capacity of plants to adapt their N metabolism to constraints, crop thinning in this case. This confirms the possibility of monitoring NUE by adapting cultural practices

Leaf-to-fruit ratio affects the impact of foliar-applied nitrogen on N accumulation in the grape must

Aims: Agroscope investigated the impact of the leaf-to-fruit ratio on nitrogen (N) partitioning in grapevine following a foliar urea application with the aim of increasing the yeast assimilable nitrogen (YAN) concentration in the must. Methods and results: Foliar urea was applied to field-grown Vitis vinifera L. cv. Chasselas grapevines as part of a split-plot trial with two variable parameters: canopy height (90 or 150 cm) and fruit load (5 or 10 clusters per vine). Foliar application of 20 kg/ha of 15N-labelled urea (10 atom% 15N) was performed at veraison. The isotope labelling method allowed to observe foliar-N partitioning in the plant at harvest. The leaf-to-fruit ratio varied between 0.4 and 1.6 m2/kg, and strongly impacted the N partitioning in the grapevines. Total N and foliar-N partitioning was mainly affected by the variation of canopy height. The YAN concentration varied from 143 to 230 mg/L (+60 %) depending on the leaf area. An oversized canopy (+31 %DW) induced a decrease in the total N concentration of all organs (-17 %), and a decrease in YAN quantity in the must in particular (-53 %). A negative correlation between the N concentration and the carbon isotope discrimination (CID) could be pointed out in a condition of no water restriction (e.g., R2 = 0.65 in the must). Conclusion: An excessive leaf area can induce YAN deficiency in the must. Thus, a balanced leaf-to-fruit ratio – between 1 and 1.2 m2/kg – should be maintained to guarantee grape maturity, YAN accumulation in the must and N recovery in the reserve organs. Significance and impact of the study: The results of this study encourage further research to understand the role of other physiological parameters that affect N partitioning in the grapevine – YAN accumulation in the must in particular – and add new perspectives for N management practices in the vineyard

Programme de collaboration franco-suisse pour la création de nouvelles variétés de vigne durablement résistantes au mildiou et à l'oïdium

Une alternative aux traitements phytosanitaires pour lutter contre le mildiou et l'oïdium de la vigne est le développement de variétés résistantes. Leur création doit intégrer non seulement le niveau de résistance mais également sa durabilité, ainsi que les performances agronomiques notamment la productivité et la composition des baies qui doit convenir à la production de vins de haute qualité. L'Inra (France) a engagé le programme de sélection ResDur, basé sur le pyramidage des facteurs de résistance, en 2000. Il a conduit à l'inscription au catalogue français d'une première série de variétés à résistance polygénique – Artaban, Floreal, Vidoc, Voltis – en 2018. Agroscope (Suisse) a démarré la création de variétés résistantes en 1996, en mobilisant les résistances portées par des variétés allemandes, principalement Bronner. Un premier aboutissement a été l'homologation en Suisse de Divico et Divona, respectivement en 2013 et 2018. En 2009 l'Inra et Agroscope ont démarré un programme de sélection commun, visant à combiner les facteurs de résistance aux maladies présents de manière complémentaire dans leurs lignées respectives. Les croisements réalisés ont généré, après sélection assistée par marqueurs, 400 descendants porteurs des facteurs de résistanceRpv1, Rpv10 et/ou Rpv3 ; Run1, Ren3 et/ou Ren3.2. Leur phénotypage agronomique et œnologique est réalisé dans le cadre d'un réseau d'essais situés dans les deux Instituts à Colmar (FR) et à Pully (CH). Les premières observations pluriannuelles, portant sur 80 descendants, ont permis d'étudier leur stabilité phénotypique pour les caractères de résistance, les traits culturaux et la qualité des vins. A l'issue de cette étape, quinze variétés candidates ont été sélectionnées et installées en essais d'évaluation de leur valeur agronomique, technologique et environnementale (VATE) en Valais (CH), ainsi que dans trois régions françaises (Champagne, Val de Loire, Vallée du Rhône). L'inscription au catalogue des premières co-obtentions Inra/Agroscope est prévue à l'horizon 2024–2025

The influence of water stress on plant hydraulics, gas exchange, berry composition and quality of Pinot Noir wines in Switzerland

Aims : The aims of this study were to investigate the physiological behavior (plant hydraulics, gas exchange) of the cultivar Pinot Noir in the field under progressively increasing conditions of water stress and analyze the effects of drought on grape and wine quality. Methods and results : Grapevines of the variety Vitis vinifera L. cv. Pinot Noir (clone 9-18, grafted onto 5BB) were subjected to different water regimes (irrigation treatments) over the growing season. Physiological indicators were used to monitor plant water status (leaf and stem water potentials and relative carbon isotope composition (d13C) in must sugars). Leaf gas exchange (net photosynthesis A and transpiration E), leaf stomatal conductance (gs), specific hydraulic conductivity in petioles (Kpetiole), yield components, berry composition at harvest, and organoleptic quality of wines were analyzed over a 7-year period, between 2009 and 2015, under relatively dry conditions in the canton of Wallis, Switzerland. A progressively increasing water deficit, observed throughout the season, reduced the leaf gas exchange (A and E) and gs in non-irrigated vines. The intrinsic water use efficiency (WUEi, A/gs) increased during the growing season and was greater in water-stressed vines than in well-watered vines (irrigated vines). This rise in WUEi was correlated with an increase in d13C in must sugars at harvest. Drought led to decreases in Kpetiole, E and sap flow in stems. A decrease in vine plant vigor was observed in vines that had been subjected to water deficits year after year. Moderate water stress during ripening favored sugar accumulation in berries and caused a reduction in total acidic and malic contents in must and available nitrogen content (YAN). Wines produced from water-stressed vines had a deeper color and were richer in anthocyanins and phenol compounds compared with wines from well-watered vines with no water stress. The vine water status greatly influenced the organoleptic quality of the resulting wines. Wines made from non-irrigated vines with a water deficit presented more structure and higher-quality tannins. They were also judged to be more full-bodied and with blended tannins than those made from irrigated vines. Conclusions : Grape ripening and resulting Pinot Noir wines were found to be largely dependent on the water supply conditions of the vines during the growing season, which influenced gas exchange and plant hydraulics. Significance and impact of the study : Plant water status constitutes a key factor in leaf gas exchange, canopy water use efficiency, berry composition and wine quality

The impact of plant water status on the gas exchange, berry composition and wine quality of Chasselas grapes in Switzerland

Aims: The aim of this research was to study the physiological and agronomical behaviors (leaf gas exchange, plant vigor, mineral supply, and yield components) of the Chasselas grapevine subjected to different water regimes during the growing season. The resulting grape and wine qualities were also determined. Methods and results: Adult vines of Vitis vinifera L. cv. Chasselas (clone 14/33-4, grafted onto 5BB) were subjected to different water regimes (various levels of irrigation) during the growing season. Physiological indicators were used to monitor the plant water status [the predawn leaf (. Leaf photosynthesis (A) and transpiration (E), stomatal conductance (gs), vulnerability to cavitation, yield parameters, berry composition at harvest, and organoleptic quality of wines were analyzed over a period of eight consecutive years between 2009 and 2016, under the relatively dry conditions of the Canton of Wallis, Switzerland. In non-irrigated vines, the progressively increasing water deficit observed over the season reduced the leaf gas exchange (A and E) and gs. The intrinsic water use efficiency (WUEi, A/gs) increased over the season and was greater in vines that had suffered water restriction than in irrigated vines. The rise in WUEi was correlated with an increase in d13C in the must sugars at harvest. Vulnerability to cavitation (embolism phenomenon) increased with increasing water deficit in the non-irrigated vines with covered soils. A decrease in plant vigor was observed in the vines that had been subjected to water restrictions over multiple years. Moderate water stress during fruit ripening was favorable for sugar accumulation in berries and lowered the contents of total and malic acidity in the musts and the content of available nitrogen (YAN). Overall, the organoleptic characteristics and quality of Chasselas wines were little influenced by the vine water regimes, with the exception of the hot, dry season in 2009 (and, to a lesser degree, in 2011). In those years, the quality of the wines from the irrigated vines, which had not suffered any water stress, received a better appreciation. Bitterness was generally greater in samples from the non-irrigated vineyards that had suffered from drought than in samples from the irrigated vines. No significant differences in the aroma and wine structure were measured during the study period, regardless of the vine irrigation status. Conclusions: The physiological behavior (gas exchange, plant vigor, and mineral supplies) and grape ripening in Chasselas vines were largely dependent on the water supply conditions in the vineyard during the growing season. Significance and impact of the study: Vine water status is a key factor in leaf gas exchange, canopy water use efficiency, berry composition and, lastly, wine quality