Genotype Variations in Water Use Efficiency Correspond with Photosynthetic Traits in Tempranillo Grapevine Clones

Round 1

Reviewer 1 Report

The manuscript is interesting and reports about a subject of increasing interest. The obtained results have considerable physiological significance in relation to the relation between WUE and gm.

Line 20. “Irrigation waste” might not be best terminology. What about water drainage?

L 22 acrony Vcmax is probably not needed

L 25. Replace “water use efficiency” with WUE. Once an acronym has been defined should be used.

In the material and methods section is not clear how many vine replicates per genotype were used.

Was substrate water content determined during the course of the experiment. This could be an interesting feature to be introduced in order to characterize the sbustrate water deficit imposed.

Why data reported in Figure 2 are reported in a Figure? I believe it could be better to report them in a Table with a statistical comparison among genotypes.

L 351 insert a space between “loss” and [52]

In the Discussion nothing is said about the grape composition of the different clones. I am aware that this study is not focused on determine the clone-to-clone variations in grape composition, but this is an important parameter to consider and should be at least discussed.

Author Response

Thanks a lot for your time and for your accurate comments that help to improve this manuscript. Find attached corrections.

Author Response File: Author Response.docx

Reviewer 2 Report

Genotype variations in water use efficiency correspond with photosynthetic traits in Tempranillo grapevine clones

By :Ignacio Tortosa, José Mariano Escalona, Ismael Opazo, Cyril Douthe, Hipólito Medrano

 Review for Agronomy

General comments

            This work investigates WUE and photosynthetic traits in Tempranillo clones under well watered and water deficit, in controlled conditions. The topic is of major importance, because in a context of climate change the use of drought resistant plant material is a key adaptation to increasingly dry conditions in the mediterrenean area. The use of drought resistant plant material should be preferred over the implementation of irrigation, which is an unsustainable practice in areas where water ressources are increasingly scarce. I’m familier with the work of this team and appreciate their efforts to investigate WUE in both controlled conditions and field conditions. As they have shown previously, measurements in controlled conditions do not always yield similar results compared to measurements carried out in field conditions. The ultimate goal is to understand the behaviour of plants is field conditions, close to production conditions. However, better insight in specific physiological traits can be obtained in controlled conditions. The authors of this study have chosen to adress key physiological mechanismes under drought conditions. To do so, sophisticated measurements needed to be implemented. These are time consuming and because all measurements need to be carried out in a short time window on the same day, only a limited number of genotypes (6) and replicates (5) could be addressed. This is the main limitation of the study. For most traits measured, differences recorded among genotypes were not significant. Fortunately, difference were significant for three major physiological traits : V_cmax, g_m (mesophyll conductance) and R (respiration). The correlation presented in Figure 3 is an important finding of this study and shows the importance of g_m in drought tolerance mechanisms in grapevine. Another important finding is the role of R, highlighted by the fact that genotype 1048 had a high R, which probably explains its high WUE and high aerial biomass production under MWS. These findings need to be confirmed in studies with more genotypes and more replicates, but their importance justifies the publication of this paper.

            A shortcoming of this work is that root biomass was not measured. In pot studies it is perfectly doable to assess root biomass and it is so much better to have « the whole picture ». I strongly recommend the team to assess root biomass in future pot studies.

            LER under MWS was highest in RJ43 and lowest in 326. At the same time, RJ43 faced the lowest water deficit (ψ_stem = -1.12) and 326 the highest (ψ_stem = -1.39). Hence, differences in LER may not be genotype related, but just the result of a lack of controll in MWS conditions. This point needs to be discussed.

            The paper is concise, well written and easy to read. The use of references is appropriate and it is apprecited that many references concern other crops, which shows that the authors have a broad view on the topic they adress.

            I recommend publication of this paper with minor revision.

Specific comments

Page 1, line 45            There are many more than 1,500 registered varieties (probably 6-7,000),  please use a more recent reference than Galet 2000.

Page 2, line 47            Replace « wasted » by « used »

Page 2, line 47            Replace « wheras » by « where »

Page 2, line 62            Replace « cultivars » by « clones »

Page 2, line 72            g_m

Page 2, line 79            A_N/C_i

Page 4, line 155          R²

Page 6 , line 224         In y axis of Figure 2 replace « bunches weight » by « bunch weight »

Page 7, line 254          μmol

Page 9, line 308          « …significant differences in biomass production were observed between the genotypes… ». I do not see where these results are presented, I only see non-significant differences in g dry weight. L^-1 in table 5.

Page 10, line365         you mean « …relationship between WUE_i and g_m/g_s » ?

Page 12, line 428        van Leeuwen….

Pahe 12, line 432        OENO One

Author Response

Thanks a lot for your time and for your accurate comments that help to improve this manuscript. Find corrections attached.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors, 

thank you for the interesting and well-written article. The topic is very important and such research is not easy, especially phenotyping, there is a bottleneck of accurate methods, however final outcomes and results are objectively described, comparable with previous studies and conclusions were reasonably made. 

Please find some comments in the pdf attachment of the article.

Wish you all the very best, 

Kind regards, 

Rewiever

Comments for author File: Comments.pdf

Author Response

Thank you very much for your time and comments. We try to add all your suggestions in the final draft.
Sincerely