CANOPY DENSITY MODIFICATION AND CROP CONTROL STRATEGIES ON 'MONTEPULCIANO' (VITIS VINIFERA L.)

Control of yield level and canopy density is considered crucial for attaining high quality grapes. This goal can be achieved combining severe winter pruning and summer pruning techniques, such as cluster thinning and leaf removal in fruiting zone around veraison, but new strategies have been recently investigated. Among them, shoot thinning and early defoliation (at flowering) of the basal part of the shoot deserve attention. To assess the effectiveness of these innovative strategies, a trial was conducted on 5-year-old ‘Montepulciano’ grapevines, 2.75×1.2 m spaced, vertically shoot positioned, cordon trained and spur pruned. Data were taken in 2009, in a medium-vigour vineyard established in Ancona area (lat.: 43°32’N; long.: 13°22’E), central Italy. Compared to the sole winter pruning (WP), shoot thinning at anthesis (ST) lowered the number of shoots/vine, thus reducing canopy density, but did not affect yield level and berry composition. Early defoliation (i.e., first six basal shoot leaves and laterals removal at anthesis) associated to ST resulted in a marked reduction of canopy density in the fruiting zone and, compared to WP, it lowered cluster compactness (-22%), increased must soluble solids (+9%) and grape phenolics (+26%), but strikingly decreased yield (-40%). Compared to WP, leaf removal just before veraison (i.e., removal of laterals of the first six shoot nodes), associated to ST did not affect yield quantity and quality, while cluster thinning at veraison, lowered the number of clusters/vine (-29%), with moderate effects on yield and grape composition. On the medium-vigorous vines of this trial, good crop levels (15.9 t/ha), adequate grape quality and low canopy management costs were assured by the sole winter pruning. Early defoliation markedly reduced yield (9.4 t/ha) but enhanced must soluble solids and grape phenolics, thus resulting a powerful canopy management technique to produce high quality grape for premium vines.