Timing Of Defoliation Research Articles

Defoliation Timing of Fruit Cluster Leaves Influences Fruit Quality Attributes, Skin Coloration and Anthocyanin Contents in ‘Hongro’ Apples

Defoliation Timing of Fruit Cluster Leaves Influences Fruit Quality Attributes, Skin Coloration and Anthocyanin Contents in ‘Hongro’ Apples

Effects of Apical, Late-Season Leaf Removal on Vine Performance and Wine Properties in Sangiovese Grapevines (Vitis vinifera L.)

An urgent challenge posed by climate change in warm grapevine-growing areas is accelerated ripening, which leads to rapid sugar accumulation while phenolics and aroma traits lag behind. Techniques that enable selectively delaying the sugar accumulation process without affecting the accumulation of secondary metabolites are essential. This study aimed to evaluate the effects of apical-to-cluster defoliation, manually applied in 2019 at the onset of veraison (D1) or 20 days later (D2), which removed about 30–40% of the pending total leaf area without altering the cluster microclimate compared with a non-defoliated control (C). Ripening trends, vegetative growth, yield components, and the final grape and wine composition, as well as wine sensorial attributes, were assessed. Although both treatments significantly lowered the final leaf area-to-yield ratio (0.80–0.90 m2/kg) compared with the 1.35 m2/kg recorded in the C vines, only D1 reduced the final total soluble solids (TSS) at harvest (2 °Brix less than C). However, the total anthocyanins were similarly limited, and titratable acidity (TA) did not differ from the C vines. The D1 wine was deemed similar to that made from control plants. Conversely, D2 failed to delay ripening, yet the D2 wine was deemed superior in terms of olfactory intensity, body, fruitiness, balance, and overall preference. Although the study was conducted over a single season, the results are robust enough to conclude that the timing of defoliation—i.e., the level of TSS concurrently reached by the C treatment—is crucial to achieving specific effects. Early defoliation appears valid for postponing ripening into a cooler period, making it quite interesting in warm–hot areas with a very long growing season; a much later defoliation, likely due to the interaction between mean canopy age and more light filtering from above the cluster zone, can elevate the quality of and appreciation for the final wine.

Performance of Cocoa Graft Seedlings as a Result of Different Number of Lower Stem Leaves and Entry Defoliation Time

This research aims to see the effect of the number of leaves left on the rootstock and the best defoliation time to improve the performance of cacao shoot connection seedlings. The research was conducted in the experimental garden of Politeknik Pertanian Negeri Payakumbuh from March to July 2023. Cocoa clone ICS was used as rootstock and clone TSH as scion. The experimental design was 4x4 factorial with 3 replications, the environmental design was completely randomized design. Data were analyzed statistically using F test and DNMRT further test at 5% level. From the research and data processing, it was found that there is an interaction between the treatment of different number of rootstock leaves and different defoliation times on the performance of cocoa shoot grafting seedlings based on the variables of percentage of grafted seedlings, number of shoots, number of leaves, leaf area and weight of seedling scion. It can be concluded that defoliation of the rootstock six days before splicing with rootstock having four leaves produces the best performance of cacao shoot grafting seedlings

Monitoring of Cotton Boll Opening Rate Based on UAV Multispectral Data

Defoliation and accelerating ripening are important measures for cotton mechanization, and judging the time of defoliation and accelerating the ripening and harvest of cotton relies heavily on the boll opening rate, making it a crucial factor to consider. The traditional methods of cotton opening rate determination are time-consuming, labor-intensive, destructive, and not suitable for a wide range of applications. In this study, the relationship between the change rate of the vegetation index obtained by the unmanned aerial vehicle multi-spectrum and the ground boll opening rate was established to realize rapid non-destructive testing of the boll opening rate. The normalized difference vegetation index (NDVI) and green normalized difference vegetation index (GNDVI) had good prediction ability for the boll opening rate. NDVI in the training set had an R2 of 0.912 and rRMSE of 15.387%, and the validation set performance had an R2 of 0.929 and rRMSE of 13.414%. GNDVI in the training set had an R2 of 0.901 and rRMSE of 16.318%, and the validation set performance had an R2 of 0.909 and rRMSE of 15.225%. The accuracies of the models based on GNDVI and NDVI were within the acceptable range. In terms of predictive models, random forests achieve the highest accuracy in predictions. Accurately predicting the cotton boll opening rate can support decision-making for harvest and harvest aid spray timing, as well as provide technical support for crop growth monitoring and precision agriculture.

Effect of Defoliation Time on Rye Yield and Its Quality under Dual-Purpose Cultivation for Roughage and Concentrate Production

A dual-purpose cultivation system allows cereals to produce both roughage and concentrate during one growing season. To establish a cultivation system for rye, the appropriate time for foliage mowing was determined to ensure a yield of nutrient-rich roughage from the first crop and abundant grain from the second crop. This is because the stage of growth at defoliation affects the yield and quality of both crops. The experimental rye line ‘4R-504’ was grown in two successive cropping seasons; 2019/2020 and 2020/2021. Foliage was mowed at three different growth stages: the booting stage (BT), the early-heading stage (EH), and the fully heading stage (FH). Along with the growth stage, the plants grew taller, and the highest dry matter yield in the first crop was observed in FH (757 g m−2), which was 1.5 times higher than that in BT (480 g m−2). Although the nutritional value was higher in plants harvested at an earlier growth stage, the EH and FH plants showed a higher dry matter yield, resulting in a higher production of metabolizable energy per area. Plants that had been mowed earlier regrew vigorously and produced an abundant amount of grains in the second crop. BT showed the highest grain yield of 239 g m−2, which corresponds to 60% of the yield from the unmowed control. FH produced grains of only 76 g m−2, which barely met the requirement of the dual-purpose cropping system. To enhance the nutritional yield of roughage, it is recommended to harvest the first crop at the early heading stage. Conversely, to achieve a higher grain yield, defoliation should be carried out during the booting stage.

Timing of defoliation affects anthocyanin and sugar decoupling in Grenache variety growing in warm seasons

Warming trends over the winegrowing regions lead to an advance of grapevine phenology, decreased yield and increased sugar content with a lower polyphenol content. We hypothesized that different leaf removal timings may counteract these effects. A two-year experiment was conducted in La Rioja (Spain) with Vitis vinifera L. cv. Grenache trained in an open-vase system. Trial consisted in a complete block design with two leaf removal treatments differing in the moment of manipulation: i) severe leaf removal treatment conducted after fruit set (ELR); and ii) severe leaf removal at veraison (LLR) compared to an untreated control (Control). Both leaf removal treatments tended to decrease sugar content with no effect on yield, these effects being highly affected by the year. Defoliation accounted for a decreased flavanol and stilbene contents in berries at harvest. An ELR increased anthocyanin and phenolic acid contents at harvest, while warming during 2022 accounted for decreased contents of all the monitored groups of flavonols. ELR was only effective for delaying ripening by means of impairing the sugar:anthocyanin decoupling during the 2021 growing season which was related to lower % of kaempferol. Altogether, results suggested that defoliation should still be applied under currently warming trends in some viticulture regions.

Effect of Intercropping Sunflower Cultivars and Defoliation Time on Sugar Beet Yield and Quality

Effect of Intercropping Sunflower Cultivars and Defoliation Time on Sugar Beet Yield and Quality

Improved statistical models for the relationship between riparian vegetation and river flow in arid environments: Implications for flow management

Riparian vegetation (RV) provides critical ecosystem services but has been degraded worldwide due to river flow change. Quantitative relationships between RV and river flow are essential for understanding RV developments and managing flow to conserve RV. Based on the improved statistical model framework that incorporates previous RV conditions into explanatory variables to estimate later RV conditions, this study quantified the RV-flow relationships on the annual scale in the arid Ejina Delta through regression analysis coupled with the normalized difference vegetation index (NDVI) and hydrological data during 2002–2020. The median of NDVIs over the April–October growing season (SMN) was used to indicate annual vegetation conditions, and annual RV cover was derived using a dynamic SMN threshold (0.077–0.084) based on its better vegetation conditions than surrounding deserts. The water year was determined as September–August based on the defoliation time and lag time of the groundwater response to river flow. The results showed that (1) the RV cover approximately expanded from 1619 to 2914 km2, and the total SMN of RV cover increased from 3711 to 7880; (2) the spatial pattern of SMN declining away from rivers was well described by an exponential function with two physically meaningful parameters (R2 = 0.99); (3) the water-year runoff ranged from 4.0 × 108 to 10.6 × 108 m3 with an increasing trend; and (4) the annual RV condition, including both the total SMN and the spatial pattern of SMN, was well estimated by the multiple linear models incorporating a previous RV condition with a coefficient <1 and the subsequent water-year runoffs (R2 = 0.98). The results suggest that previous RV conditions are necessary to improve the rationality and performance of RV-flow relationship models, and in arid environments, annual RV conditions depend on the RV's degradation characteristics under zero flow conditions and the ecological benefit by river flow.

Grazing patterns, diet quality, and performance of cow-calf pairs using continuous or rotational grazing in the Texas panhandle USA

This study 1) measured diet quality and performance of cow-calf pairs; and 2) compared defoliation patterns and changes in standing crop of functional groups relative to the proximity of water over a grazing season under continuous (CG) or rotational (HSD) grazing at the same stocking rate and stocking intensity. Eighty lactating cow-calf pairs were weighed and assigned among shortgrass-dominated rangeland pastures (three replicates per treatment). Standing crop by species was measured at study initiation and completion. Frequency of grazed plants was measured along 0.39km point transects radiating from water troughs. Cow and calf weights and average daily gains were compared between treatments. Mean dietary CP was higher for CG cattle. Forage quality for major species (blue grama and gummy lovegrass) did not differ between treatments. Y-intercepts of regression lines predicting probability of defoliation differed between treatments following the 1st, 6th, and 7th 16-day intervals of the 112-day grazing study. Final standing biomass of gummy lovegrass was lower in HSD. Final cool-season annual grass biomass was lower in CG. HSD grazing can regulate the frequency and timing of defoliation, thereby changing relative proportions of plant species, inter-species competition and animal performance over time.

Low Temperature Inhibits the Defoliation Efficiency of Thidiazuron in Cotton by Regulating Plant Hormone Synthesis and the Signaling Pathway.

Thidiazuron (TDZ) is the main defoliant used in production to promote leaf abscission for machine-picked cotton. Under low temperatures, the defoliation rate of cotton treated with TDZ decreases and the time of defoliation is delayed, but there is little information about this mechanism. In this study, RNA-seq and physiological analysis are performed to reveal the transcriptome profiling and change in endogenous phytohormones upon TDZ treatment in abscission zones (AZs) under different temperatures (daily mean temperatures: 25 °C and 15 °C). Genes differentially expressed in AZs between TDZ treatment and control under different temperatures were subjected to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to compare the enriched GO terms and KEGG pathways between the two temperature conditions. The results show that, compared with the corresponding control group, TDZ induces many differentially expressed genes (DEGs) in AZs, and the results of the GO and KEGG analyses show that the plant hormone signaling transduction pathway is significantly regulated by TDZ. However, under low temperature, TDZ induced less DEGs, and the enriched GO terms and KEGG pathways were different with those under normal temperature condition. Many genes in the plant hormone signal transduction pathway could not be induced by TDZ under low temperature conditions. In particular, the upregulated ethylene-signaling genes and downregulated auxin-signaling genes in AZs treated with TDZ were significantly affected by low temperatures. Furthermore, the expression of ethylene and auxin synthesis genes and their content in AZs treated with TDZ were also regulated by low temperature conditions. The upregulated cell wall hydrolase genes induced by TDZ were inhibited by low temperatures. However, the inhibition of low temperature on genes in AZs treated with TDZ was relieved with the extension of the treatment time. Together, these results indicate that the responses of ethylene and auxin synthesis and the signaling pathway to TDZ are inhibited by low temperatures, which could not induce the expression of cell wall hydrolase genes, and then inhibit the separation of AZ cells and the abscission of cotton leaves. This result provides new insights into the mechanism of defoliation induced by TDZ under low temperature conditions.

Uji Ketepatan Waktu Defoliasi dan Aplikasi Penambahan Unsur Nitrogen terhadap Produksi Dan Mutu Benih Tetua Jantan Jagung Manis (Zea mays saccharata Sturt)

One of effort to fulfill national sweet corn demand independently is by manipulating the environment. This study aims to determine the effect of the time of defoliation and the time of nitrogen adding application toward production and quality of sweet corn male parent. The research was conducted on the Research and Development land of PT. Wira Agro Nusantara Sejahtera Kediri from October 2020 until February 2021. The research used factorial Randomized Complete Block Design (RCBD) method with 3 replications. The data will be analyzed using ANNOVA and continued with DMRT level of 5%. The first factor is the time of defoliation 68 days after planting, 75 days after planting and 82 days after planting. The second factor is the time of nitrogen application of 4 and 6 weeks after planting, 6 and 8 weeks after planting then 8 and 10 weeks after planting. The result showed that the time of defoliation and nitrogen application gave the significant effect for almost all parameters. The interaction between time of defoliation 68 days after planting and nitrogen application on 6 and 8 weeks after planting has significant effect on the parameters of seeds production per hectare 3,42 ton/ha and weight of 100 grains 12,47 gram.

The carbon budget of the managed grasslands of Great Britain – informed by earth observations

Abstract. Grasslands cover around two-thirds of the agricultural land area of Great Britain (GB) and are important reservoirs of organic carbon (C). Direct assessments of the C balance of grasslands require continuous monitoring of C pools and fluxes, which is only possible at a small number of experimental sites. By relying on our quantitative understanding of ecosystem C biogeochemistry we develop models of grassland C dynamics and use them to estimate grassland C balance at various scales. Model-based estimation of the C budget of individual fields and across large domains is made complex by the spatial and temporal variability in climate and soil conditions, as well as in livestock grazing, grass cutting and other management activities. In this context, earth observations (EOs) provide subfield-resolution proxy data on the state of grassland canopies, allowing us to infer information about vegetation management, to apply observational constraints to the simulated ecosystems and, thus, to mitigate the effects of model input data uncertainty. Here, we show the potential of model–data fusion (MDF) methods to provide robust analyses of C dynamics in managed grasslands across GB. We combine EO data and biogeochemical modelling by implementing a probabilistic MDF algorithm to (1) assimilate leaf area index (LAI) times series (Sentinel-2); (2) infer defoliation instances (grazing, cutting); and (3) simulate livestock grazing, grass cutting, and C allocation and C exchanges with the atmosphere. The algorithm uses the inferred information on grazing and cutting to drive the model's C removals-and-returns module, according to which ≈1/3 of C in grazed biomass returns to the soil as manure (other inputs of manure not considered) and C in cut grass is removed from the system (downstream C emissions not considered). Spatial information on soil C stocks is obtained from the SoilGrids dataset. The MDF algorithm was applied for 2017–2018 to generate probabilistic estimates of C pools and fluxes at 1855 fields sampled from across GB. The algorithm was able to effectively assimilate the Sentinel-2-based LAI time series (overlap = 80 %, RMSE = 1.1 m2 m−2, bias = 0.35 m2 m−2) and predict livestock densities per area that correspond with independent agricultural census-based data (r = 0.68, RMSE = 0.45 LU ha−1, bias = −0.06 LU ha−1). The mean total removed biomass across all simulated fields was 6 (±1.8) t DM ha−1 yr−1. The simulated grassland ecosystems were on average C sinks in 2017 and 2018; the net biome exchange (NBE) was -191±81 (2017) and -49±69 gC m−2 yr−1 (2018). Our results show that the 2018 European summer drought reduced the strength of C sinks in GB grasslands and led to a 9-fold increase in the number fields that were annual C sources (NBE &gt; 0) in 2018 (18 % of fields) compared to 2017 (2 % of fields). The field-scale analysis showed that management in the form of timing, intensity and type of defoliation were key determinants of the C balance of managed grasslands, with cut fields acting as weaker C sinks compared to grazed fields. Nevertheless, extreme weather, such as prolonged droughts, can convert grassland C sinks to sources.

Effect of Defoliation Age on The Production and Energy Value of Indian Bluegrass (Bothriochloa pertusa)

The purpose of this experiment was to evaluate the herbage production and energy value of Suket putihan grass (Bothriochloa pertusa) harvested at different ages. The experiment was carried out following a completely randomize design with 3 treatments and 3 replications. The treatments consisted of different defoliation ages of Suket putihan grass (Bothriochloa pertusa), i.e. respectively at 40 days (BP40), 60 days (BP60), 80 days (BP80). The observed variables included the dry matter (DM) production, stem leaf ratio, In vitro digestibillity and energy value. Result showed that the defoliaton age had a significant effect (P&lt;0.05) on dry matter production, stem leaf ratio, dry matter digestibillity and had a very significant effect (P&lt;0.01) on the organic matter digestibillity and energy value of Suket putihan grass (Bothriochloa pertusa). The DM production of Suket Putihan grass (Bothriochloa pertusa) increased with increasing defoliation age, while its In vitro digestibility and energy value decreased due to the high stem to leaf ratio and increased harvesting time. In conclusion, the best defoliation time for B. pertusa is between 40 and 60 days after planting.

Effect of Severities and Timing of Defoliation on Root Yield and Quality of Sugar Beet (Beta vulgaris L.) at Alkadarou

A field experiment was conducted in winter for two successive seasons (2015-2016 and 2016-2017) at College of Agriculture Farm, University of Bahri, Sudan to investigate the effect of severities and timing of defoliation on root yield and quality of sugar beet (Beta vulgaris L.). The experimental design was Randomized Complete Block / factorial with four replicates. Three defoliation severities 0% (control) ,50%, and 100% were applied which referred to as S0, S1, and S2 respectively and four dates of defoliation 7weeks after sowing , 10weeks after sowing , 13weeks after sowing , and 16 weeks after sowing (WAS) which referred to as T1 , T2 , T3 , and T4 respectively. Results showed that 100 % defoliation decreased significantly Brix%, Pol. %, root yield t/ha, and white sugar t/ha in both seasons when compared to control. Results revealed that different treatments of defoliation time, in first season, had no significant differences on Pol. %, root yield t/ha, and white sugar t/ha; and significant differences only on Brix. % . In second season Pol. % and root yield t/ha were not significant whereas Brix. % and white sugar t/ha were significantly decreased as affected by different treatments of defoliation time. Generally, 100% defoliation at 13 WAS gave the lowest records of studied parameters in both seasons.

Cluster Thinning Improves Aroma Complexity of White Maraština (Vitis vinifera L.) Wines Compared to Defoliation under Mediterranean Climate

Defoliation and cluster thinning are useful canopy management techniques to modulate grapevine carbon distribution and microclimate. Both techniques are directed to achieve the proper balance between fruit and foliage, and to maximize production of well-ripened fruits and quality wines. We performed five canopy treatments on Maraština grapevine grown at a commercial vineyard in the Vrgorac Valley region of Croatia: three different times of basal defoliation, cluster thinning at the veraison, and an untreated control. The effects of the canopy changes on the chemical composition of grapes and wines were studied. The treatments had variable impacts on yield components and basic wine composition. Volatile aroma compounds in produced wines were analyzed using gas chromatography–mass spectrometry coupled with a mass-selective detector. The concentrations of 70 of the 96 individual volatile compounds were significantly influenced by the canopy technique used. The concentrations of 58 of these compounds were different according the timing of defoliation. Cluster thinning at an intensity of 35% produced wines with more terpenes, esters, higher alcohols, other alcohols, volatile phenolic compounds, lactones, and other compounds than other treatments. Among terpenes, cluster thinning increased terpinen-4-ol, linalool, trans-β-farnesen, and geraniol. Odor activity value analysis revealed 16 volatile compounds that contributed to the aroma of cluster-thinned wines.

The effect of 19 years of restoration managements on forage quality and herbage‐soil relationships within improved upland grassland

AbstractRestoration managements based on extensification strategies are commonly used to improve biodiversity on formerly improved grasslands. In this study the long‐term effects of six different restoration management regimes (extensive sheep grazing only, hay cutting only, hay cutting followed by aftermath extensive grazing; each with and without lime application) on forage quality, and soil/herbage/sward characteristics relationships were determined and compared with a conventionally fertilized, limed and extensively grazed control.Restoration managements incorporating cutting resulted in higher forage quality than forage from grazed‐only treatments; the latter featuring only a few forb species and large proportion of ungrazed matured grasses plus dead biomass. Concentrations of crude protein, neutral detergent fibre and K in the herbage were negatively correlated with cover of forbs and total number of plant species, whereas in vitro organic matter digestibility, and concentrations of water‐soluble carbohydrates, Ca, Mg, and Na were correlated positively. In contrast, concentrations of Ca, Mg, and Na were negatively correlated with the total cover of graminoids and dry matter standing biomass. Regardless of management treatment the forage was generally suitable only for sheep or beef cattle feeding. A positive relationship between P and K concentration in the soil and in the herbage was recorded. No effect of previous liming on forage quality was found. Overall, this study found introducing long‐term restoration managements to support biodiversity by postponing the timing of the first defoliation by cutting to mid growing season did not deteriorate forage quality in comparison with continual extensive sheep grazing in improved upland grassland.

Grazing and defoliation timing effects in Great Plains ponderosa pine woodland following a large summer wildfire

There remains a high level of ambiguity around post-fire grazing management. The Lodgepole Complex fire burned 109,346 ha in east-central Montana in July 2017, including areas previously burned in 2003 by the Bureau of Land Management for fuels mitigation. We hypothesized that herbaceous productivity and species composition in ponderosa pine woodlands are resistant to moderate grazing and timing of defoliation the first growing season after fire. Eight exclosures (25 × 15 m) were built, 4 on reburned area and 4 on wildfire area. To determine grazing effects, a 15 × 10 m sampling area in each exclosure was paired with a grazed section outside the exclosure. Additionally, four 5x10-m plots were established within each exclosure and were mowed to 10 cm in June, July, August, or not mowed to determine seasonal defoliation effects. Differences between grazed and nongrazed sites in 2019 were limited. There was a trend for less old dead biomass in grazed than nongrazed treatments. Species richness was greater on grazed sites than nongrazed or reburn sites. Native species richness was greater on grazed sites than nongrazed sites and reburn sites had an intermediate level of native species richness. Standing crop was reduced by defoliation, with current year and perennial grass biomass being unaffected. The reduction in standing crop was driven by less old dead biomass on defoliated plots. June defoliation reduced C3 grasses and increased C4 grasses, and June and July defoliation each reduced annual grasses. Simpson’s and native Simpson’s diversity were greater on defoliated plots. Results indicate ponderosa pine woodland is resilient to moderate post-fire grazing.

The effect of defoliation on the 3-isobutyl-2-methoxypyrazine biosynthesis in wine grapes

Field studies were conducted on Vitis vinifera cv. ‘Cabernet Sauvignon’ to evaluate the effects of the defoliation time (pre- and post-flowering and veraison) and severity on the 3-isobutyl-2-methoxypyrazine (IBMP) concentration and expression levels of the key related genes in grape berries. The IBMP concentration in the grapes decreased significantly at harvest after all the defoliation treatments. The earlier and heavier the defoliation treatment, the lower the IBMP concentration. The relative expression level of VvOMT3 in the berry skin was closely positively correlated with the IBMP accumulation in all the treatments. Early defoliation coupled with a 1-week delay in the harvest time may be an effective management strategy to control the IBMP concentration in grapes.

PENGARUH PEMUPUKAN LEWAT DAUN DAN WAKTU DEFOLIASI PADA PERTUMBUHAN DAN HASIL JAGUNG (Zea mays L.) VARIETAS NASA 29

This study aims to determine the effect of foliar fertilization and corn leaf trimming (defoliation) on the growth and yield of hybrid corn NASA 29. This research was conducted at the Samboja Experimental Garden, Bukit Raya Village, Kec. Samboja, Kutai Kartanegara, East Kalimantan, in April-July 2020. The planting material used was the NASA 29 hybrid corn variety, KNO3 fertilizer, Gandasil D fertilizer, MKP fertilizer. This study used a factorial randomized block design (3 X 3) with 3 (three) replications. The first factor was the type of fertilizer that was applied through the leaves (foliar) which consisted of 3 levels, namely P1 (fertilizer gandasil), P2 (fertilizer MKP), and P3 (fertilizer Rosasol) with a dose of 10 grams/liter each given at the age of 65 DAS. The second factor was defoliation time which consisted of 3 levels, namely D1 (75 days after planting), D2 (defoliation at 82 days after planting), and D3 (defoliation at 90 days after planting). The observed data were analyzed by means of the analysis of variance with the F test at α 5%. if there is a significant difference, it is followed by the Honestly Significant Difference (HSD) test at α 5%. The results showed that the treatment of the type of fertilizer through the leaves and defoliation along with the interactions had no significant effect on the variables of plant height, ear length, and ear diameter, while the treatment of fertilizers by leaf and defoliation and their interactions had no significant effect on the variables of plant height, stem diameter. ear length and ear diameter. P3 fertilizer treatment and defoliation at the age of 82 days after planting (D2) gave the best results on the variable ear weight and dry seed weight.

Influence of Different Defoliation Timings on Quality and Phenolic Composition of the Wines Produced from the Serbian Autochthonous Variety Prokupac (Vitis vinifera L.)

The variety Prokupac is the dominant variety in the vineyards of Southern Serbia, which produces quality wines of characteristic and unique tastes. In the agroecological conditions of the Prokuplje vine district, the influence of manual defoliation on the phenolic profile of the wine produced from the variety Prokupac was examined. Four experimental treatments with different timings of manual defoliation were applied: early defoliation—treatment I, early defoliation—treatment II, late defoliation—treatment III and the control. The phenolic profile of the wine was determined for the three treatments of defoliation and the control treatment. Additionally, a multivariate analysis was applied on the obtained results, together with already published data (grape seeds and skins phenolic profiles). Identification and quantification of the phenolic compounds was performed using ultra-high-performance liquid chromatography (UHPLC) with an ultraviolet multi-diode detector (DAD) and mass detector with three analyzers—triple quadrupole (QQQ). Based on the obtained results, it was determined that there are significant differences between the experimental treatments in the content of individual polyphenols, total polyphenols and the antioxidant capacity. Twenty (20) phenolic compounds were identified in the wine samples of the experimental treatments. Defoliation significantly affected the variations of the contents of phenolic acids and flavonoids. In treatment III, the highest content of gallic acid was obtained, while the treatments with early defoliation did not differ in relation to the control sample. Early defoliation in treatments I and II had an effect on the phenolic composition of the wine by favoring the accumulation of flavonol, while the content of hydroxycinnamic acid and total anthocyanins (TAC) was higher in treatment III. The TAC increases with later defoliation. The wines obtained by the defoliation treatments did not show higher antioxidant activity compared to the control sample. A principal component analysis resulted in clustering of the samples based on the phenolic components characteristic for each group of samples.