Cluster-Zone Leaf Removal and GA3 Application at Early Flowering Reduce Bunch Compactness and Yield per Vine in Vitis vinifera cv. Pinot Gris

Compact bunches have been often associated with higher susceptibility to Botrytis cinerea and therefore reduction in berry quality in grapevine. The objective of this study was to evaluate three management methods (early leaf removal, gibberellic acid, and their combination) for reducing bunch compactness in Vitis vinifera cv. Pinot gris trained in two different training systems with contrasting vigor (Guyot and pergola). Treatments were applied at BBCH 62 or BBCH 65 and yield components, total soluble solids, fruit set, and bunch compactness parameters were evaluated. Both treatments individually reduced berry number, mean bunches weight and bunches compactness as well as yield per vine when compared to control-untreated vines. However, no major differences were observed when both the treatments were applied in combination for Guyot or pergola although a higher reduction in yield was detected for Guyot and a significant increase in total soluble solids was observed in pergola. Our study suggests that intense leaf removal and gibberellic acid applied at early flowering can help reducing bunch compactness in Pinot gris and showing it in two training systems. In particular, leaf removal represents a valuable alternative to plant growth regulators (i.e., gibberellic acid) as applicable in organic viticulture.

Effect of Vine Length and Leaf Removal on Growth and Yield of Sweet Potato [Ipomoea batatas (L.)] in the Wet Middleveld of Eswatini

Sweet potato (Ipomoea batatas L.) is an economically important food crop in Eswatini. Since its introduction, numerous agronomic research activities were carried out in agricultural research centers, non-governmental organizations, and universities. However, information on the correct vine length for planting to improve sweet potato root yield in Eswatini is scanty. Therefore, this study aimed at helping farmers with the correct vine length to be used for improved growth and yield of sweet potatoes. A field experiment was conducted at the Luyengo campus, crop production farm during the 2019/2020 crops season. It was laid in a Randomized Complete Block Design (RCBD) in a factorial arrangement with three replicates. The treatments were vines planted with or without leaves and different vine lengths; 25 cm, 30 cm, and 35 cm. Kenya white variety was used. Data were collected on growth and yield parameters. Results showed that leaf removal yielded significantly (P<0.05) lower than non-leaf removal. This may be attributed to delayed photosynthetic activity in the former. The Vine length had no significant effect on yield. It is concluded that vines with leaves be used as planting material, and the length of vines to be used for planting should be 25 to 30 cm.

Vine architecture and production control measures to improve the quality of the wine from Shiraz variety (Vitis vinifera L.)

Aim of study: Ssix thinning treatments were studied to improve the chemical composition and quality of grapes of cv. ‘Shiraz’ under two vine architectures (vase and trellis). Area of study: Spain (from 2015 to 2016). Material and methods: The following thinning treatments were applied during four consecutive crop seasons: T0, control; T1, removal of 33% of the clusters (75 BBCH stage); T2, removal of 33% of the clusters (85 BBCH stage); T3, removal of the leaves at the base of the branches; T4, removal of the leaves at base of the branches together with removal of 33% of the clusters; T5, grouping of green branches; and T6, grouping of green branches and removal of 33% of the clusters. Main results: All the treatments increased the luminosity and degree of polymerization, improving the color intensity and stability in the wines. In the musts, the levels of phenolic compounds (from 48.0 and 46.7 mg L-1 in T0 trellis and vase, respectively, to 66.8 and 68.9 mg L-1 in T6 trellis and vase, respectively), anthocyanins and sugars (from 22.0 and 22.1 mg L-1 in T0 trellis and vase, respectively, to 24.3 mg L-1 in T6 trellis and vase), were considerably improved. Research highlights: Treatments T6 and T4 reported the best results. Branch grouping was more efficient than leaf removal regarding the contents of phenolic compounds. With respect to vine architecture, the results point out small differences, but we recommend the application of the treatments, mainly T4 and T6, under vase architecture. The season effect was mainly observed in the fourth year, probably due to the climatic conditions.

Optimum Management of Leaf Removal and Lateral Branch Fruit Set in Winter-Planted Cultivation of Paprika

This study was carried out to balance the production and consumption of assimilates according to crop conditions as a basis to reduce the waste of assimilation through leaf and fruit control. There were four treatments: one fruit and two leaves (F1L2); two fruits and two leaves (F2L2); two fruits and three leaves (F2L3); and two fruits and four leaves (F2L4). This study showed that, as the number of leaves increased in Periods 1 and 2, the stem diameter and average weight decreased, with F1L2 having the highest stem diameter and average weight, although its numbers of leaves and fruits were the fewest. In the summer, Period 3, F1L2 production was the lowest due to increased rates of flower drop and fruit drop. In Period 4, when ambient temperature and light levels were decreased, the number of fruits was increased. However, the production was decreased. F1L2 and F2L4 showed significant decreases in production. Although F1L2 showed the highest average weight, it had a low production due to a decrease in the number of fruits. F2L4 showed weak generative growth due to an imbalance in growth over the summer. After reaching the last stage of development, the number of leaves showed the highest average weight and production in F2L4.

Precipitation before Flowering Determined Effectiveness of Leaf Removal Timing and Irrigation on Wine Composition of Merlot Grapevine

Grapevine productivity, and berry and wine flavonoid concentration, depend on the interactions of cultivar, environment, and applied cultural practices. We characterized the effects that mechanical leaf removal and irrigation treatments had on the flavonoid concentration of ‘Merlot’ (Vitis vinifera, L.) grape berries and wines in a hot climate over two growing seasons with contrasting precipitation patterns. Leaves were removed by machine, either at prebloom (PBLR), or at post-fruit-set (PFLR), or not removed (control) and irrigation was either applied as sustained deficit irrigation (SDI) at 0.8 of crop evapotranspiration (ETc) from budbreak to fruit set, or regulated deficit irrigation (RDI) at 0.8 ETc from bud break to fruit set, 0.5 ETc from fruit set to veraison, and 0.8 ETc from veraison to harvest, of ETc In 2014, PFLR reduced the leaf area index (LAI) compared to control. The RDI decreased season-long leaf water potential (ΨInt) compared to SDI. However, in 2015, none of the treatments affected LAI or ΨInt. In 2014, berry flavonoid concentrations were reduced by PBLR as well as SDI. SDI increased the flavonoid concentrations in wine, and PFLR increased some wine flavonols in one season. No factor affected the concentrations of wine proanthocyanidins or mean degree of polymerization. Thus, mechanical PFLR and RDI may increase berry flavonoid accumulation without yield reduction, in red wine grapes cultivars grown in hot climates when precipitation after bud break is lacking. However, spring precipitation may influence the effectiveness of these practices as evidenced by this work in a changing climate.

The Effect of Cutting and Waterlogging on Plant-Related CO2 and N2O Fluxes Associated with the Invasive N-Fixing Species Gunnera tinctoria

The overall impact that plant invasions have on greenhouse gas emissions (GHG) by plant-mediated effects and how these interact with environmental and management factors is largely unknown. To address this, we report on the effects of leaf removal and waterlogging, either singularly or in combination, on the fluxes of CO2 and N2O associated with the invasive species Gunnera tinctoria. Both the removal of leaves with and without flooding resulted in higher CO2 emissions due to reductions in photosynthesis. Whilst waterlogging alone was also associated with a reduction in photosynthesis, this was slower than the effect of leaf removal. Significant N2O emissions were associated with intact plants, which increased immediately after leaf removal, or seven days after waterlogging with or without leaf removal. We found positive correlations between CO2 and N2O emissions and petiole and rhizome areas, indicating a size-dependent effect. Our results demonstrate that intact plants of G. tinctoria are a source of N2O emissions, which is enhanced, albeit transiently, by the removal of leaves. Consequently, management interventions on invasive plant populations that involve the removal of above-ground material, or waterlogging, would not only reduce CO2 uptake, but would further compromise the ecosystem GHG balance through enhanced N2O emissions.

‘Frontenac’ Grape Response to Canopy Management in North Dakota

Experiments were conducted in 2013 and 2014 to evaluate the effects of training system and leaf removal treatments on yield and quality for ‘Frontenac’, an interspecific hybrid wine grape, at a research vineyard located near Absaraka, North Dakota. The experiment was structured as a randomized complete block design with a split-plot arrangement including four training system treatments (Geneva Double Curtain (GDC), High Cordon (HC), Vertical Shoot Positioned (VSP), Four-Arm Kniffin (4AK)), and four-leaf removal timing treatments (bloom, post-bloom, veraison, and a control, no removal) with eight replicates. In 2013, 1428 growing degree days (GDDs) accumulated in the 155 days between frost events. In 2014, 1156 GDDs accumulated in the 121 days between frost events, 272 GDDs less than the year prior. Even with the large GDD differences between years, there was no significant interaction between trellis type and leaf removal, and the main factor of leaf removal did not influence any of the fruit variables where data were collected. Combined data analysis showed no significant differences in fruit juice total soluble solids (TSS) or titratable acidity (TA). The fruit juice pH in 2013 was greater when grapes were grown in the VSP system compared to grapes grown in the other trellis systems. In 2014, live nodes and total shoots were greater for grapes grown on GDC and 4AK systems compared to grapes grown on the HC and VSP systems. Additionally, in 2014, grapes grown on the GDC system had a greater cluster number and yield when compared to grapes grown on the 4AK or VSP systems. These findings suggest that ‘Frontenac’ fruit TSS accumulation and TA were not affected by leaf removal or trellis system in North Dakota vineyards and that yield gains may be reached due to the training system without negatively affecting fruit quality.