Diána Ágnes Nyitrainé Sárdy

To mitigate the potential drawbacks of late pruning, this study evaluated an alternative approach utilising the anatomical features of the umbrella trellis system, cane pruning, and apical dominance. Vine canes were tied at four distinct phenological stages: before budburst, at the 3-leaf, 5-leaf, and 7-leaf stages (BBCH 00, 13, 15, and 17, respectively). We hypothesised that exploiting apical dominance would allow distal buds to burst first; subsequent arching and tying of the cane would then trigger the burst of the remaining basal buds with a temporal delay. The effects of these treatments were evaluated based on leaf area index (LAI), canopy porosity and structure, fertility coefficients, and yield components, supplemented by must composition analysis at harvest and compared alongside a traditional late-pruned cordon-system evaluated under identical phenological timings. Our findings indicated that delayed tying treatments on umbrella-trained vines did not affect canopy structure, resulted in higher yields, greater average bunch weights, without inducing the negative side effects reported for late pruning cordon-trained vines. Regarding final must composition, the treatments produced minor and inconsistent variations, with no significant differences across most measured parameters at harvest.

Maintaining grape cultivation requires the continuous production of healthy propagating material and the control of economically important viruses. For more effective virus eradication, it is beneficial to try chemotherapeutic agents that have not yet been used on grapevine. We therefore tested two chemotherapeutic agents with different mechanisms of action (2-thiouracil and zidovudine) in addition to ribavirin, which is already used on grapevine. Viruses and viroids were identified in the mother plants of different grapevine cultivars by small RNA HTS (High-Throughput Sequencing), and RT-PCR verified the results. After chemotherapy, the regenerated plants were tested using RT-PCR and the efficacy of the three chemotherapeutic compounds was evaluated. Among the tested agents, ribavirin had the broadest elimination effect (the virus was not detectable by RT-PCR after 8 months) on most viruses. It proved to be particularly effective (the virus was not detectable by RT-PCR in most of the tested plants) against GFkV, GLRaV-4, GPGV and GRSPaV. The use of 2-thiouracil caused high phytotoxicity and was effective against GLRaV-4 among the viruses tested, having no effect on the other viruses. Zidovudine alone failed to eliminate any of the viruses we tested. 2-thiouracil, ribavirin and zidovudine were unable to eliminate HSVd and GYSVd-1 viroids.

The study compared the effects of conventional and vegan processing aids in the clarification of must, focusing on the phenolic and sensory characteristics of must and wine. The hypothesis was that plant protein could provide results similar to those of conventional aids containing proteins of animal origin, especially in aromatic grapes, where hyperoxidation is avoided. Conducted in 2024 in Etyek-Buda, Hungary, the initial trials subjected the Irsai Olivér grape must to gravity sedimentation with various agents. Vegan processing aids, notably the combination of pea protein and chitin-glucan, showed a gentle impact on the assimilable nitrogen content and a similar reduction in turbidity to those with animal proteins. Nitrogen flotation trials compared gelatin and the vegan alternative (a combination of pea protein and chitin–glucan) in Irsai Olivér and Chardonnay must clarification. The removal of phenolic substances was monitored using the Folin–Ciocalteu method, the acid butanol assay, and the vanillin assay. In addition, nitrogen levels were evaluated before and after the flotation experiments. The plant-based processing aid effectively improved the sensory quality of Irsai Olivér. However, the gelatin-treated Chardonnay was fresher and less bitter than the vegan option, which was less balanced and more bitter with weaker aroma and flavor.

Climate change has a significant negative impact on agriculture and food production. This trend requires technological development and the adaptation of new technologies in both the grapevine production and winemaking sectors. High temperatures and heat accumulation during the growing season result in faster ripening and a higher sugar content, leading to a higher alcohol content during fermentation. The negative consequences are an imbalanced wine character and consumer reluctance, as lower alcoholic beverages are now in high demand. Over the last decade, several methods have been developed to handle this impact and reduce the alcohol content of wines. In this study, we used the MASTERMIND^® REMOVE membrane-based dealcoholization system to reduce the alcohol concentration in of Pinot gris wines from 12.02% v/v to 10.69% v/v and to investigate the effect on analytical parameters in three steps (0.5%, 1%, and 1.5% reductions) along the treatment. To evaluate the impact of the partial alcohol reduction and identify correlations between the wine chemical parameters, data were analyzed with ANOVA, PCA, multivariate linear regression and cluster analysis. The results showed that except for the extract, sugar content and proline content, the treatment had a significant effect on the chemical parameters. Both free and total SO₂ levels were significantly reduced as well as volatile acid, glycerol and succinic acid levels. It must be highlighted that some parameters were not differing significantly between the untreated and the final wine, while the change was statistically verified in the intermediate steps of the partial alcohol reduction. This was the case for example for n-Propanol, i-Amylalcohol, Acetaldehyde, and Ethyl acetate. The multivariate linear regression model explained 18.84% of the total variance, indicating a modest but meaningful relationship between the alcohol content and the investigated analytical parameters. Our results showed that even if the applied instrument significantly modified some of the wine chemical parameters, those changes would not influence significantly the wine sensory attributes.

In this study, the effect of different foliar applications on the grapevine (Vitis vinifera L. cv. Riesling) leaf morphology was investigated. Leaf chlorophyll content was measured with an Apogee MC100 portable chlorophyllmeter, leaf thickness was investigated with a thickness gauge while the light transmittance was evaluated with a smartphone application running on a Xiaomi Redmi Note 9. Results showed that foliar applications have a significant effect on the leaf morphological traits. According to the correlation analysis of pooled samples, there is no significant relation between the monitored parameters. Interestingly if samples are split according to the applied treatments, we found a correlation between the measured traits that highlight the impact of the foliar application on the morphological characteristics. Our present research demonstrates that smartphones can be effectively integrated into agricultural studies and provide data that can complement observations.

Protein-based clarification agents were tested to clarify Chardonnay grape musts during sedimentation. The experiments were conducted in the Etyek–Buda Wine Region in Northwest Hungary over four vintages between 2020 and 2023. The performance of the treatment agents was influenced by several factors, such as the composition of the grape must (the absolute concentration and the relative ratio of phenolic compounds) which varied with the vintage characteristics, the physiological and phenolic ripeness of the grapes, and the composition of the clarifying agents itself. Recent investigations show that fully ripe fruit juices can be clarified more effectively, and the effectiveness increases when different types of clarification agents are combined with the plant proteins, e.g., PVPP greatly facilitates the removal of phenolic compounds. The tested plant protein-based clarification agents did not influence the YAN source of the grape musts before fermentation. Our investigations proved an effective impact of these preparations even during the first steps of wine technology. Sensory properties and chemical stability are improved by decreasing the polyphenol content before fermentation, and, besides the good technological effects, wines treated with plant protein agents can be included in the vegan diet.

Leaf chlorophyll content is a key indicator of plant physiological status in viticulture; therefore, regular evaluation to obtain data for nutrient supply and canopy management is of vital importance. The measurement of pigmentation is most frequently carried out with hand-held instruments, destructive off-site spectrophotometry, or remote sensing. Moreover, smartphone-based applications also ensure a promising way to collect colorimetric information that could correlate with pigmentation. In this study, four grapevine genotypes were investigated using smartphone-based RGB (Red, Green, Blue) and CIE-L*a*b* colorimetry and a portable chlorophyll meter. The objective of this study was to evaluate the correlation between leaf chlorophyll concentration and RGB- or CIE-L*a*b*-based color indices. A further aim was to find an appropriate model for discriminating between the genotypes by leaf coloration. For these purposes, fully developed leaves of ‘Chardonnay’, ‘Sauvignon blanc’, and ‘Pinot noir’ clones 666 and 777 were investigated with the Color Grab smartphone application to obtain RGB and CIE-L*a*b* values. Using these color values, chroma, hue, and a further 31 color indices were calculated. Chlorophyll concentrations were determined using an Apogee MC100 device, and the values were correlated with color values and color indices. The results showed that the chlorophyll concentration and color indices significantly differed between the genotypes. According to the results, certain color indices show a different direction in their relationship with leaf pigmentation for different grapevine genotypes. The same index showed a positive correlation for the leaf chlorophyll concentration for one variety and a negative correlation for another, which raises the possibility that the relationship is genotype-specific and not uniform within species. In light of this result, further study of the species specificity of the commonly used vegetation indices is warranted. Support Vector Machine (SVM) analysis of the samples based on color properties showed a 71.63% classification accuracy, proving that coloration is an important ampelographic feature for the identification and assessment of true-to-typeness.

The high number of grapevine (Vitis vinifera L.) cultivars grown world-wide are described and identified according to detailed morphological and morphometric descriptor lists. The grapevine leaf is of utmost importance in characterization, despite its traits being very sensitive to environmental factors. In this study, the effect of irrigation/drought stress on the individual leaf morphology and morphometry of the ‘Hárslevelű’ grapevine (Vitis vinifera L.) cultivar was examined. To verify the effect of the applied irrigation methods (drip and subsoil irrigation) on the plant’s water status, water potential measurements were carried out during the 2022 season. The effect of the applied treatments on the vegetative growth was evaluated according to point quadrat and a multichannel LiDAR analysis in order to describe the width of the canopy area, row volume, and area coverage index. The individual leaf morphology was assessed via traditional morphometry and colorimetry. Our results showed that rainfed plants had a significantly lower stem ψ compared to the drip- and subsoil-irrigated plants at all examined dates. The point quadrat results indicate that the leaf layer number was significantly (p < 0.05) influenced by the position, while the treatment showed no effect on the leaf layer number. The leaf colorimetry showed a difference among the samples, as significant alterations were found in 28 out of the 32 examined color properties. Within the traditional morphometric analysis, 54 traits were evaluated, and 14 of the traits were significantly altered due to the different water management systems.

As the sensitivity of perennial crops to climate change becomes more pronounced, clonal selection, which is already very time-consuming for grapevine, may take even longer, while its importance is increasing. In the case of indigenous grapevine varieties, the purpose of clonal selection is twofold: to mitigate problems of cultivation and at the same time, to preserve the varietal character. The cultivation technique issue of ‘Kéknyelű’ is the low fertility (functionally female-flowered variety), and as for ‘Juhfark’ it is the significant susceptibility to grey rot. Based on daily meteorological data of 11 years, the years were classified into 3 groups and harvest data were analyzed within each group. Significant difference in yield was found between clone B.2. and the base ‘Kéknyelű’. Both clones of ‘Kéknyelű’ matured with significantly lower pH compared to the base variety. Given the acidic character of ‘Kéknyelű’ wine and the predicted rise in must °Brix and pH as a result of climate change, these differences may be useful in the future. Botrytis infection only showed statistically significant differences between year groups for ‘Juhfark’. It is intriguing that in most years, the rate of grey rot infection was lower in both clones compared to the base variety, especially in year groups 1 and 3 when the overall rate of Botrytis infection was quite low.

Spectral investigation of the canopy has an increasing importance in precision viticulture to monitor the effect of biotic and abiotic stress factors. In this study, RGB (color model, red, green, blue)-based vegetation indices were evaluated to find a correlation with grapevine leaf chlorophyll concentration. ‘Hárslevelű’ (Vitis vinifera L.) leaf samples were obtained from a commercial vineyard and digitalized. The chlorophyll concentration of the samples was determined with a portable chlorophyll meter. Image processing and color analyses were performed to determine the RGB average values of the digitized samples. According to the RGB values, 31 vegetation indices were calculated and evaluated with a correlation test and multivariate regression. The Pearson correlation between the chlorophyll concentration and most of the indices was significant (p < 0.01), with some exceptions. The same results were obtained with the Spearman correlation as the relationship had high significance (p < 0.01) for most of the indices. The highest Pearson correlation was obtained with the index PCA2 (Principal Component Analysis 2), while Spearman correlation was the highest for RMB (difference between red and blue) and GMB (difference between green and blue). The multivariate regression model also showed a high correlation with the pigmentation. We consider that our results would be applicable in the future to receive information about the canopy physiological status monitored with on-the-go sensors.