Effects Of Early Defoliation Research Articles

Effects of early defoliation on the skin phenolic composition of ‘Tempranillo’ grapevines

Effects of early defoliation on the skin phenolic composition of ‘Tempranillo’ grapevines

Effect of Early Defoliation on Fruit Yield, Reserve Accumulations and Flower Bud Formation in ‘Sinano Sweet’ Apple Trees

Effect of Early Defoliation on Fruit Yield, Reserve Accumulations and Flower Bud Formation in ‘Sinano Sweet’ Apple Trees

Influence of early leaf removal on autochthonous and international grapevines in Sicily

Early leaf removal is an innovative viticultural practice for regulating yield components and improving grape quality. Direct sunlight interception by fruit has been associated with improved fruit quality and is generally desirable to some degree in most vineyards. The effects of early defoliation on four indigenous and international grapevines in Sicily were monitored. The experiment was conducted in a commercial Vitis vinifera L. vineyard located in the Ragusa district of Sicily over two consecutive years (2010 and 2011). The grapevines studied were Frappato, Nero d’Avola, Syrah and Cabernet Sauvignon grafted onto 140 Ru. rootstock. The treatments consisted of a control (no leaf removal) and of their removal from the cordon up to the leaf of the last cluster per shoot. Leaf removal at the earlier stages of cluster development appears to be an effective strategy in order to obtain smaller clusters and, therefore, control the vine crop load when coupled with other agronomic strategies.

Effects of Early Defoliation on Yield, Fruit Composition, and Harvest Season Cluster Rot Complex of Grapevines

Viticulture in Michigan is limited by a cool and humid climate and as a result, there is a problem of harvest season cluster rot, especially in cultivars with compact cluster morphology. Economically important wine grape varieties in eastern North America possess varying susceptibility to harvest season cluster rot. Some important cultivars that are susceptible are Pinot gris, Pinot noir, Riesling (Vitis vinifera L.) as well as Seyval and Vignoles (French–American hybrids or interspecific hybrid cultivars). A common characteristic of these cultivars is the compactness of the berries held on the cluster rachis. The aim of this work was to determine whether a quantified amount of leaf removal or a temporary reduction in carbon assimilation at the beginning of bloom would reduce fruit set and cluster compactness. Vines subjected to removal of four or six basal leaves had an average fruit set reduction of ≈45% from a non-treated control. Cluster weight and berries per cluster were similarly reduced with a greater effect on the basal than the apical cluster of the shoot. Reduced fruit set was associated with a reduction in cluster compactness and harvest season rot. This was also reflected in yield and basic fruit chemistry parameters associated with the importance of basal leaves to the developing cluster. Multiple applications of stylet oil at different time intervals resulted in significant reduction in net photosynthesis (Pn). A single application had no significant impact on Pn, whereas multiple applications reduced leaf assimilation rates. However, this reduction in Pn did not reduce fruit set or improve cluster compactness. There was a strong negative effect of early leaf removal in Year 1 on vine performance in Year 2; this carryover effect increased shootless nodes per vine, reduced the number of clusters per shoot and per vine, and dramatically reduced fruit set and consequently yield per vine.

Effects of Early Defoliation on Shoot Photosynthesis, Yield Components, and Grape Composition

The effectiveness of early leaf removal on high-yielding cultivars Sangiovese and Trebbiano (<i>Vitis vinifera</i> L.) was investigated as a tool for reducing crop potential and for inducing looser clusters that are less susceptible to rot. Fruit set, cluster weight, berry number per cluster, berry size, and cluster compactness were reduced by all defoliation treatments as compared to non-defoliated shoots. Physiological assessment performed in a one-year study on Sangiovese indicated that prebloom removal of the six basal leaves elicited no difference between treatments in mean seasonal assimilation (A) per shoot (2.91 μmol s⁻¹ for control against 2.81 μmol s⁻¹ for the defoliated), a fact due to the offsetting action of more vigorous lateral shoot formation and higher A rates for both main and lateral leaves after veraison in the defoliated shoots. Grape composition was improved by defoliation (higher Brix in both cultivars and higher anthocyanins and phenolics in Sangiovese) as a result of more assimilates being available per unit of cropping and smaller berries characterized by an increased skin-to-pulp ratio. The three-year-study on Trebbiano also showed no carryover effects of defoliation on the following year’s bud differentiation and very few year x treatment interactions, suggesting the prevailing effects of leaf removal over variability because of climate. Overall, early defoliation may be an excellent tool for yield control, replacing time-consuming manual cluster thinning. A time-consistent response suggests that this practice may also improve grape composition.

Flower bud abscission in apricot: Competition between vegetative and flower buds, and effects of early defoliation and high pre-blossom temperatures

SummaryFlower bud abscission is an important factor in apricot (Prunus armeniaca L.) yield reduction reaching 80% or more in several cultivars like ‘Guillermo’. In this work we studied competition between vegetative and flower buds, and the effect of early defoliation (relative to canopy development), and the high pre-blossom temperatures (increasing by bagging the maximum sunny day temperatures by 6–7°C), on flower bud abscission in apricot ‘Guillermo’. Flower bud abscission appear to be due mainly to the internal balance and competition between vegetative and flower buds. Results showed an influence of the removal of vegetative buds on the reduction of the number of flower buds abscised. High pre-blossom temperatures in winter, during the period of rapid floral development, appear to be the other important factor increasing flower bud abscission. Finally, damage to the canopy in autumn, or early defoliation, had no important influence on flower bud abscission, although a higher percentage of buds abscinded was observed in defoliated branches.

Effects of early defoliation on the seedling growth of subterranean clover

Two experiments were conducted in an open-sided glass shelter at Perth during winter. Subterranean clover (Trifolium subterraneum, L.) seedlings were grown in shallow seed boxes at low plant densities, 2 4 and 2 0 plants/dm2. The effects of a single defoliation involving mainly the removal of cotyledons only, on shoot growth and leaf production were measured at harvest, c. 5 weeks after sowing. Total shoot dry weights were reduced by 15-30% when 40-60% of the leaf area was removed by single defoliations from days 7 to 19 after planting. However, the growth was reduced by almost 70% when both cotyledons were removed (days 7 to 9) before emergence of the unifoliate leaf, i.e. when all of the leaf area was removed. In general, the relative reduction in growth largely depended on the percentage of leaf area removed, rather than on time of removal. Defoliation also reduced the size of trifoliate leaves, and total numbers of trifoliate leaves at harvest. There was a linear relationship between total leaf numbers and shoot dry weights. In the field, these findings are probably of more relevance in terms of insect damage, especially from redlegged earth mites, than for grazing by sheep.

Effect of Early Defoliation on Maize Growth and Yield: an Eleven‐year Perspective

We previously reported that grain yield of the maize (Zea mays L.) hybrid ‘Trojan TXS 85’ was increased following 100% defoliation at the five‐leaf stage. The objective of this study was to extend those observations and to examine the relationship between early defoliation, soil‐water use, and yield. Eight additional years of defoliation trials (plants 100% defoliated at the five‐leaf stage) were conducted in the field with Trojan TXS 85. The soils at the two experimental sites are a Webster clay loam (Typic Haplaquoll) and a Nicollet clay loam (Aquic Hapludoll). Defoliation decreased grain yield 3 of the 8 additional yr, and had a nonsignificant (negative) effect the remaining 5 yr. Positive yield response to defoliation was associated with low yields and with low end‐of‐season available soil water. It thus appears that an early reduction in vegetative growth of maize might help avoid drought stress in regions where late‐season water stress is common. Early defoliation does not appear to be a practical management approach in high‐yielding environments, such as the upper Midwest, where soil‐water deficits are infrequent and unpredictable.