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La synthèse de phytoalexines stilbéniques est un des mécanismes de défense de la vigne contre les pathogènes fongiques. Actuellement, il n’existe que peu d’informations sur le rôle de ces molécules dans la défense de la vigne contre l’oïdium (Erysiphe necator). L’analyse et la quantification des stilbènes dans des disques foliaires infectés, provenant de cépages sensibles (Vitis vinifera cv. Chasselas) à très résistants (IRAC 2292, Vitis candicans), ont été confrontées au développement du pathogène. Les résultats montrent que les quantités mesurées de stilbènes, notamment de viniférines, reportées aux sites d’infection, permettent de discriminer les cépages sensibles des résistants. En effet, les plus hautes concentrations en viniférines ont été mesurées chez les cépages résistants deux jours déjà après l’inoculation et correspondent à une inhibition du développement d’E.necator. L’analyse des stilbènes aux sites d’infection et l’accumulation de viniférines en tant que mécanisme de défense de la vigne sont discutées dans l’optique de développer des marqueurs fiables de résistance contre l’oïdium, pour la sélection précoce des semis issus des programmes de sélection d’ACW.

Keywords: powdery mildew, Erysiphe necator, grape, defence mechanisms, stilbens, appressorium, breeding, resistant cultivars.

E-Mail: sylvain.schnee@agroscope.admin.ch

Adress: Agora

L’effet de différentes techniques de limitation de la récolte – par suppression manuelle de grappes entières ou de demi-grappes, ou chimique, en utilisant différentes doses de gibbérelline (GA3) – a été testé durant quatre ans sur une parcelle de Pinot noir clone RAC 12 au domaine expérimental d’Agroscope Changins-Wädenswil ACW à Nyon (VD). L’application de 10 à 100 ppm de GA3 pendant la floraison et la section des grappes par la moitié ont permis de réduire significativement l’attaque de botrytis et de pourriture acétique sur les raisins. L’effet a été meilleur que l’application de deux botryticides spécifiques à la fermeture de la grappe et au début de la véraison. L’utilisation de GA3 a provoqué un peu de coulure et du millerandage, surtout avec les doses les plus élevées (50 et 100 ppm). Dans cet essai, l’utilisation de GA3 n’a pas provoqué de diminution sensible de la fertilité des bourgeons l’année suivante. Une baisse de rendement n’a été enregistrée qu’avec les doses les plus élevées. L’expression végétative de la vigne, la composition des moûts et des vins ainsi que leur qualité organoleptique ont été peu affectées par l’éclaircissage.

Keywords: grapevine, gibberellins, GA3, hand-thinning, chemical thinning, sour rot, grey rot, Botrytis cinerea, clusters morphology, must and wine quality, yield regulation.

E-Mail: jean-laurent.spring@agroscope.admin.ch

Adress: Agroscope, 1009 Pully

Irrigation experiments conducted in Leytron (Wallis, Switzerland) on the red wine rootstocks Pinot noir, Gamay, Diolinoir and red Humagne led to confirmation of the highly positive effect of moderate water stress on grape ripening and wine quality. A gradual and moderate restriction in water supply at the time of fruit ripening resulted in a slowing down of plant growth and favoured the accumulation of sugar in berries. The resulting wines had a deeper colour, were richer in phenol compounds and preferred by wine tasters. Under conditions of greater and longer water stress, these advantages tended to be cancelled out. A close relationship was established between the theoretical water deficit and water stress levels measured in the vineyards, which could be exploited as a tool to decide if an irrigation is required.

Keywords: irrigation, water stress, plant behaviour, wine quality.

E-Mail: jean-laurent.spring@agroscope.admin.ch

Adress: Agroscope, 1009 Pully

Monilinia fructicola (anamorph Monilia fructicola) is a particularly aggressive species of Monilia attacking flowers, twigs as well as fruits. In some regions of USA the fungus undergoes sexual reproduction. For this reason, the pathogen could develop faster fungicide resistances than M. fructigena and M. laxa, for which the sexual cycle seams to be marginal. In Europe, this fungus is considered a quarantine organism. In former ACW studies, the pathogen was found on imported stone fruits, but never in Swiss orchards. The M. fructicola monitoring presented in this paper aimed to verify if the pathogen meanwhile established in Swiss orchards. In total 222 apricots fromWalliser orchards have been molecularly tested. Most of the samples were infected either with M. fructigena or M. laxa, but 10 samples (4.5%) were infected with M. fructicola, all originating from the same orchard. To confirm this discovery, different tests proposed by the European and Mediterranean Plant Protection Organization (EPPO) have been performed. All the tests confirmed that M. fructicola has been found for the first time in a Swiss orchard.

Keywords: quarantine organism, brown rot, EPPO, Monilinia fructicola, Switzerland.

E-Mail: andrea.patocchi@agroscope.admin.ch

Adress: Agroscope, 8820 Wädenswil

Four training systems (free multiple leader, V-trellised multiple leader, Y-trellised and Solaxe) were compared with the apricot varieties Bergarouge and Harostar during nine years. The influence of increased planting density and tree height limitation on tree growth and productivity, sensitivity to canker due to Eutypa lata and Cytospora ssp. as well as on fruit size were analyzed and discussed. Planting density did not improve performance, neither in early bearing phase, nor during mature tree phase. Tree growth and habitus as well as training according to tree formation influenced canker development due to Eutypa lata and Cytospora ssp. Harostar presented more severe symptoms than Bergarouge. Both intensive systems (Y-trellised and Solaxe) showed a stronger weakening in response to severe pruning. In extreme cases, this also contributed to fruit size decrease. Actual available rootstocks are too vigourous for planting densities higher than 500 trees/ha, except for particular cases.

Keywords: apricot, tree training, intensive orchard, tree height, canker disease, Eutypa lata.

E-Mail: philippe.monney@agroscope.admin.ch

Adress: Agroscope, 1964 Conthey

Apple texture is one of the most important quality parameters that influence the consumer acceptability of this fruit. Fruit juiciness is one of the textural attributes that is synonymous of apple freshness for the consumers. The sensory analysis is the only way to measure this parameter objectively in relation to the consumer perception. This study proposes a new instrumental method to measure fruit juiciness in a simple and reliable way. This method seems very interesting as the instrumentally measured juiciness is significantly correlated to the sensory score analysed by an expert apple panel.

Keywords: apple, quality, juiciness, sensory analysis, objective measures.

E-Mail: e.mehinagic@groupe-esa.com

Adress: Agora