Microclimatic modifications induced by trellis systems lyre and vertical trellis: effects on grape sanitary quality

Abstract

Plant architecture modifies microclimate – air relative humidity (RH%) and temperature (T°C)- in clusters area, which influences incidence of fungal rots. This work studies changes in T and HR% due to plant architecture in cv. Tannat vineyards and its impact on clusters health. The trial was carried on in 2008 at a commercial vineyard in Uruguay. Two plant architectures were considered: Lyre (L) and Vertical trellis (VT). At veraison, the relative position of aerial plant organs and percentage of exposed clusters were observed by PointQuadrat method. RH(%) and T(°C) were recorded during ripening period. In both L and VT plant architectures, dataloggers for cluster interior T monitoring were installed. Hours with different RH% levels inside canopy were quantified. To evaluate rots incidence, percentage of infected clusters per plant was determined using a visual criterion; clusters showing at least 10% of berries affected by characteristic mycelia were discarded. Plant architecture modified leaf layer number (LLN) (3.9 and 8.7 for L and VT respectively), canopy density and therefore cluster exposure and position. During the day, the lowest T and thus the lowest vapour removal around the leaves could increase RH% within VT dense canopies. Open L canopies were well ventilated and favoured both water vapour dissipation and T increase; this possibly increased vapour pressure deficit. In this experiment, rot incidence was markedly higher in VT (64%) respect to L (17%) because of a reduced cluster exposure (that lowered T) and a higher HR% at the canopy interior. This led to a longer wetness period which favoured the fungal infection. VT had a higher LLN and clusters were located in the lower centre of the canopy, resulting in a lower percentage of exposed clusters (15%) respect to L (60%). Higher cluster exposure to sunlight in L increased T and reduced levels of HR% at clusters. The highest canopy density of VT maintained HR% significantly higher, increasing fungal rots incidence.