Sustainable Vineyard Management with On-Field UV-C Irradiation: Impacts of Supplementary Applications on Grape Composition and Secondary Metabolites

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

D’Onofrio et al. observed that UV-C treatment on growing grapes had a certain effect on the anthocyanin content of grape berries and a significant impact on grape secondary metabolites, providing insights into the improvement of grape quality. However, the following issues still require further revision and refinement:

1. The references are outdated. It is recommended that the authors incorporate the latest published literature to discuss this study more thoroughly.
2. The article contains a considerable amount of experimental data, but the summary of the content is insufficiently complete and detailed. It is suggested that the authors summarize all the contents of this study into a schematic diagram to facilitate better understanding and reading.
3. There are numerous typographical errors in the article. The author should carefully revise and proofread the text to enhance readability.
4. Gene names should be italicized, and protein names should not be italicized. Full names of gene names and professional terms should be provided upon their first occurrence in the text.
5. Data from two years were used in the article, but it is evident that some data show substantial variations between years. The author should explain the reasons for these differences and indicate their significance. If the differences in T1 are not significant, the reasons should also be explained.
6. In Figure 4, which measures flavonoid content in grape skins, the vertical axis should be clearly labeled. Additionally, the labeling of significant differences among different treatments should be further checked and reanalyzed.
7. There are many errors in the reference format. It is recommended that the authors carefully revise the references according to the journal's required format.

Author Response

Comment 1.   The references are outdated. It is recommended that the authors incorporate the latest published literature to discuss this study more thoroughly.

Response 1. We thank the reviewer for the comment. We have conducted an exhaustive review of the current literature specifically regarding UV-C on-field treatments on grapevine. To the best of our knowledge, the manuscript already includes all pertinent and most recent studies available in this niche area. As we aimed to maintain a focused discussion, we have omitted or barely used references that are not directly relevant to field UV-C applications on grapes. However, if the reviewer has specific recent publications in mind that we may have overlooked, we would be pleased to evaluate their inclusion.

 

Comment 2. The article contains a considerable amount of experimental data, but the summary of the content is insufficiently complete and detailed. It is suggested that the authors summarize all the contents of this study into a schematic diagram to facilitate better understanding and reading.

Response 2. Thank you for your suggestion, we have now included a new Table (Table 5) reporting the overall summary of the measurements/analysis carried out.

 

Comment 3. There are numerous typographical errors in the article. The author should carefully revise and proofread the text to enhance readability.

Response 3. Thank you for your suggestion, we have carefully revised the entire manuscript.

 

Comment 4. Gene names should be italicized, and protein names should not be italicized. Full names of gene names and professional terms should be provided upon their first occurrence in the text.

Response 4. Thank you, we have modified the text according to your suggestions.

 

Comment 5. Data from two years were used in the article, but it is evident that some data show substantial variations between years. The author should explain the reasons for these differences and indicate their significance. If the differences in T1 are not significant, the reasons should also be explained.

Response 5. In on-field experiments involving secondary metabolites like VOCs and phenolic compounds, it is expected that absolute concentrations will fluctuate between years due to varying climatic conditions. However, the overall patterns and treatment effects observed in our study remain remarkably consistent across both seasons. Our objective was to evaluate the specific impact of UV-C applications on grape metabolism, rather than to characterize inter-annual variability. We believe that the Results section already provides a detailed comparison, especially for secondary metabolites which are the core of the manuscript. Given the extensive volume of data generated by our analysis, we prioritized highlighting the most significant compounds and findings to ensure that the patterns remain clear and accessible to the reader.

 

Comment 6. In Figure 4, which measures flavonoid content in grape skins, the vertical axis should be clearly labeled. Additionally, the labeling of significant differences among different treatments should be further checked and reanalyzed.

Response 6. Figure 4 reports flavonol content (as specified in the caption) not the total flavonoids. While the vertical axis label—'ng g⁻¹ of berry FW'—is identical to the one used for anthocyanins in Figure 3, in our opinion it accurately represents the flavonol concentrations intended for this figure. To address the concerns regarding potential confusion, we have revised the figure caption to improve clarity. Regarding 'labeling of significant differences', if you are referring to the asterisks used to denote statistical significance, we have re-verified our data and can confirm that the analysis and its corresponding notation are correct.

 

Comment 7. There are many errors in the reference format. It is recommended that the authors carefully revise the references according to the journal's required format.

Response 7. Thanks for the comment, we have revised all the references according to the journal’s guidelines.

Reviewer 2 Report

Comments and Suggestions for Authors

The article explores the quality of wine grape fruits after UV-C treatment using methods such as GC-MS and HPLC. The article has certain significance, but there is still a small issue that needs to be revised.

（1）Line 13: "little information are available" should be changed to "little information is available" (information is an uncountable noun).

（2）Line 120: "DAA" should be spelled out in full upon its first mention in the text.

（3）Throughout the text: The term "UV-C" should be used consistently. Avoid the unhyphenated form "UVC", which is currently used interchangeably in the manuscript (e.g., in Figure 4).

（4）Line 319: The specific details of the "standard phytosanitary protocol" (types of agrochemicals, application frequency, timing) are not sufficiently detailed in the manuscript.

（5）Discussion Section: It is recommended to add a paragraph specifically discussing the seemingly contradictory phenomenon observed in 2022, where free VOCs decreased while glycosylated VOCs increased under UV-C treatment. This discussion should offer speculative explanations linked to the high-temperature and drought conditions prevalent in that particular growing season.

Author Response

Comment 1.   Line 13: "little information are available" should be changed to "little information is available" (information is an uncountable noun).

Response 1. Thank you for your suggestion, we changed it in the text.

 

Comment 2.   Line 120: "DAA" should be spelled out in full upon its first mention in the text.

Response 2.  We spelled DAA and all other acronyms which had the same issue.

 

Comment 3.   Throughout the text: The term "UV-C" should be used consistently. Avoid the unhyphenated form "UVC", which is currently used interchangeably in the manuscript (e.g., in Figure 4).

Response 3.  Done, thank you.

 

Comment 4.   Line 319: The specific details of the "standard phytosanitary protocol" (types of agrochemicals, application frequency, timing) are not sufficiently detailed in the manuscript.

Response 4.  At line 319 we reported the “standard UV-C protocol” which is the UV-C application protocol detailed in the Figure 5 without any agrochemicals applications. Now we have specified it in the text (now lines 345-346)

 

Comment 5.   Discussion Section: It is recommended to add a paragraph specifically discussing the seemingly contradictory phenomenon observed in 2022, where free VOCs decreased while glycosylated VOCs increased under UV-C treatment. This discussion should offer speculative explanations linked to the high-temperature and drought conditions prevalent in that particular growing season.

Response 5.  We appreciate this observation; indeed, this pattern was consistently observed throughout both years of the study. We have integrated the Discussion section with this aspect.

Reviewer 3 Report

Comments and Suggestions for Authors

> The title suggests a comparison between the use and non-use of UV-C; however, in the experiment both treatments received UV-C, differing only in the number of applications. The title could be improved by explicitly indicating the use of supplementary or late UV-C applications.

Line 93. Figure 1.

The figure integrates climate, phenology and time, providing useful environmental context for interannual comparison. However, it mainly describes climatic conditions rather than offering a quantitative assessment of the climatic effects on vine developmental rate. The inclusion of accumulated thermal time (e.g. growing degree days) would strengthen the evaluation of physiological equivalence between years and improve the reproducibility and biological interpretation of the treatments. Where available, complementary indicators related to water demand (e.g. precipitation distribution or relative humidity) could further help contextualise potential environmental stress.

Line 96. Table of vegetative-reproductive variables.

The presentation of vegetative and reproductive variables by year is clear. However, the absence of an analysis of the year effect or treatment x year interaction restricts inference to the specific conditions of each season.

Line 116. Figure 2.
The absence of an explicit definition of the temporal reference for the variable “days after” (DAA) hinders the physiological interpretation of gas exchange measurements and limits the reproducibility of temporal sampling. Furthermore, air temperature recorded by the weather station describes ambient conditions, whereas leaf temperature reflects the plant’s energy and transpirational balance; therefore, the two variables are not directly comparable and may differ without necessarily indicating treatment effects. Given that measurements were conducted within a limited time window and only in 2023, potential differences could emerge under conditions of higher transpirational demand or in seasons with different climatic contexts.

Lines 198 and 199 (Tables 3 and 4).

The characterization of volatile and glycosylated secondary metabolites is exhaustive and valuable; however, the simultaneous presentation of numerous individual compounds and chemical subgroups complicates the identification of patterns and the biological and oenological interpretation of the results. Additional synthesis (e.g. focusing on key compounds) would facilitate data interpretation and improve biological and oenological interpretation.

Line 317.

Meteorological data describe the environment but do not necessarily reflect the level of stress experienced by the plants. As the response to UV-C is modulated by temperature, humidity and plant water status, a more detailed description of soil moisture conditions and nutritional management, together with at least one indicator of plant stress, would allow a more robust physiological interpretation of the results.

Given the high sand content of the soil and the type of response variables evaluated (gas exchange and secondary metabolites), a qualitative description of nutritional management alone may not be sufficient to rule out confounding effects related to variation in plant nutritional or water status. Reporting fertilisation doses and at least one quantitative indicator of nutritional status (e.g. leaf analysis at a defined phenological stage) would strengthen the reproducibility and inferential validity of the study.

Line 409.

The conclusions appropriately reflect the changes observed in secondary metabolites; however, statements related to 'grape quality', 'wine colour stability' and 'aroma complexity' extend beyond the scope of the results, as no enological or sensory parameters were evaluated.   

 

Author Response

Comment 1.   The title suggests a comparison between the use and non-use of UV-C; however, in the experiment both treatments received UV-C, differing only in the number of applications. The title could be improved by explicitly indicating the use of supplementary or late UV-C applications.

Response 1.   We agree with your observation and have revised the title accordingly to better reflect the scope of our study.

 

Comment 2.   Line 93. Figure 1.

The figure integrates climate, phenology and time, providing useful environmental context for interannual comparison. However, it mainly describes climatic conditions rather than offering a quantitative assessment of the climatic effects on vine developmental rate. The inclusion of accumulated thermal time (e.g. growing degree days) would strengthen the evaluation of physiological equivalence between years and improve the reproducibility and biological interpretation of the treatments. Where available, complementary indicators related to water demand (e.g. precipitation distribution or relative humidity) could further help contextualise potential environmental stress.

Response 2.  Thank you, we agree that a quantitative climatic assessment is essential for a thorough interannual comparison. Accordingly, we have replaced the previous figure with a new Figure 1 (line 91) that includes GDD to offer a more robust framework for evaluating physiological development across both seasons.

 

Comment 3.   Line 96. Table of vegetative-reproductive variables.

The presentation of vegetative and reproductive variables by year is clear. However, the absence of an analysis of the year effect or treatment x year interaction restricts inference to the specific conditions of each season.

Response 3.  We decided to analyse each year independently to maintain consistency with the statistical approach applied to all other parameters presented in the manuscript. Our primary objective was to emphasize the specific impact of the UV-C treatment rather than to characterize the 'Year' effect or climate-treatment interactions. It is well-established in viticultural research that inter-annual variability is a natural and expected occurrence in field experiments due to fluctuating climatic conditions, and we believe that a factorial design would add complexity that might obscure the primary treatment trends, which were consistent across both seasons.

 

Comment 4.   Line 116. Figure 2.

The absence of an explicit definition of the temporal reference for the variable “days after” (DAA) hinders the physiological interpretation of gas exchange measurements and limits the reproducibility of temporal sampling. Furthermore, air temperature recorded by the weather station describes ambient conditions, whereas leaf temperature reflects the plant’s energy and transpirational balance; therefore, the two variables are not directly comparable and may differ without necessarily indicating treatment effects. Given that measurements were conducted within a limited time window and only in 2023, potential differences could emerge under conditions of higher transpirational demand or in seasons with different climatic contexts.

Response 4.  Thank you for your comments, we have updated the figure 2 caption (line 118) to explicitly define DAA as 'days after anthesis' clarifying the temporal reference. The analysis of the leaf-to-air temperature differential is a well-established proxy in plant physiology as a non-invasive indicator of plant water status and energy balance, reflecting how the leaf modulates its temperature relative to the environment via latent heat loss. While we acknowledge that these measurements represent a specific window in 2023 and valid for our specific conditions, the lack of significant treatment effects suggests that the UV-C doses used did not impair the leaf’s thermoregulatory capacity under the conditions tested.

 

Comment 5.   Lines 198 and 199 (Tables 3 and 4).

The characterization of volatile and glycosylated secondary metabolites is exhaustive and valuable; however, the simultaneous presentation of numerous individual compounds and chemical subgroups complicates the identification of patterns and the biological and oenological interpretation of the results. Additional synthesis (e.g. focusing on key compounds) would facilitate data interpretation and improve biological and oenological interpretation.

Response 5.  We appreciate your recognition and we acknowledge the complexity of managing such an extensive dataset; however, the tables were designed to include summary values for major chemical classes, providing an immediate overview of the primary treatment effects. Both the Results and Discussion sections are also focused on the compounds and subgroups most critical to berry quality, allowing the reader to navigate the data by focusing on key markers of interest.

 

Comment 6.   Line 317.

Meteorological data describe the environment but do not necessarily reflect the level of stress experienced by the plants. As the response to UV-C is modulated by temperature, humidity and plant water status, a more detailed description of soil moisture conditions and nutritional management, together with at least one indicator of plant stress, would allow a more robust physiological interpretation of the results.

Given the high sand content of the soil and the type of response variables evaluated (gas exchange and secondary metabolites), a qualitative description of nutritional management alone may not be sufficient to rule out confounding effects related to variation in plant nutritional or water status. Reporting fertilisation doses and at least one quantitative indicator of nutritional status (e.g. leaf analysis at a defined phenological stage) would strengthen the reproducibility and inferential validity of the study.

Response 6.  According to your comment, to provide a more robust interpretation, we have integrated midday stem water potential values measured at veraison into Table 1 (line 95). Additionally, we have expanded the Materials and Methods section to include specific details regarding the fertilization doses and nutritional management of the vineyard, while we do not have leaf ionomic analysis data available.

 

Comment 7.   Line 409.

The conclusions appropriately reflect the changes observed in secondary metabolites; however, statements related to 'grape quality', 'wine colour stability' and 'aroma complexity' extend beyond the scope of the results, as no enological or sensory parameters were evaluated.  

Response 7.  Thank you, in response to your comment, we have refined the Conclusions (line 441) to mitigate some sentences. However, since the primary objective of our research was to evaluate the impact of UV-C on secondary metabolites—the core components of grape quality and in turn, of wine quality—we feel it is necessary to highlight these potential implications, considering that in our opinion the Conclusion section has to present these points as logical perspectives for further research.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The author has made detailed revisions based on the proposed questions, and I agree to accept and publish them.

Reviewer 3 Report

Comments and Suggestions for Authors

No comment.

Comments for author File: Comments.pdf