Is the Nectar Sugar Content the Key to Improving Onion and Bunching Onion Seed Yield?

Round 1

Reviewer 1 Report (Previous Reviewer 4)

Dear Authors,

I re-reviewed the manuscript titled "Is the nectar sugar content the key to improve onion and bunching onion seed yield?" by Verónica C. Soto, Roxana E. González, Cristian A. Caselles and Claudio R. Galmarini.

After a thorough analysis of the content of the manuscript, I see that the Authors have properly addressed the vast majority of my earlier comments. However, I still consider the list of cited publications a bit short, but I also realize that the research presented in this manuscript is niche. In addition, I still see a lot of technical problems in the manuscript, but these will certainly be removed during the further stages of preparing the manuscript for printing.

I hereby recommend this manuscript for publication in the journal Horticulturae.

Author Response

We sincerely thank you for your time and consideration. We have accepted your suggestions and introduced the changes in the new version of the manuscript. As you mentioned this research is a niche so that there are few studies in this field, and some references have more than 10 years old, however we have added 2 more cites to the manuscript, one of them from 2022.

Reviewer 2 Report (Previous Reviewer 2)

Should the authors upload the revision as I previously concerned one by one, it will make me clear why the authors did not change. One of my concers is why do the authors use hybrid for bunching onion and male sterile line for onion? You should clearly stated that the interspecific line Allium fistulosum x Allium cepa is bunching onion. What is fertile line for onion? I think there is no comparability between a hybrid and a system including male sterile and fertile. Further, the fertile line is a maintainer or restorer for this male sterile line? The authors stated that “the 4:1 ratio of sterile/fertile plants was used, which is typical in onion commercial seed production”, however, is there any factors such as genotype and different growth ration affected seed yield? If the authors use different system, especailly when they use MSL, the yield is also affected the compatability with different genotypes.

Author Response

We have included some of the requested information in the new version of the manuscript. 
One of my concerns is why do the authors use hybrid for bunching onion and male sterile line for onion? Almost two thirds of the onion cultivars of the most important seed companies' catalogs belong to the hybrid category. Hybrid cultivars predominate because of increased yield and uniformity. Emasculation on a large scale is not practical. Thus, production of hybrid-onion seed is based on systems of cytoplasmic-genic male sterility (CMS). Two main sources of CMS have been geneti¬cally characterized, identified as S and T. Type S is the most used due to the usual occurrence of the recessive allele in Ms. To obtain these seeds, it is necessary to cross a sterile male line (MSL) with a fertile one. Male-sterile plants developed from this original plant produced normal flowers except that the pollen did not develop into a viable stage (Havey, 1999. J. Amer. Soc. Hort. Sci. 124(6):626-629). Onion male sterility is of cytoplasmic and genetic origin. The inheritance is conditioned by a single recessive nuclear gene ms/ms, and a cytoplasmic factor, where one cytoplasm is considered normal (N) and the other sterile (S). To be male sterile, the onion plant must have the genetic and cytoplasmic condition Sms/ms. (Sidhu et al., 2004, doi: 10.1300/J153v06n02_12). On the other hand, in USA and Latin-American countries the production technology of bunching onion is similar to the one used in Europe, although, it is mostly base on an interspecific hybrid between Allium fistulosum and Allium cepa (Padula, et al. 2022, doi:10.3390/plants11030343). We consider that the strength of our research is that was carried out in commercial fields, in different locations and during different productive seasons. Thus, using the genotypes that are available for producer makes our research more applicable.  

You should clearly state that the interspecific line Allium fistulosum x Allium cepa is bunching onion. We have clarified in the manuscript that bunching onion is interspecific line Allium fistulosum x Allium cepa. 

What is fertile line for onion? I think there is no comparability between a hybrid and a system including male sterile and fertile. Further, the fertile line is a maintainer or restorer for this male sterile line? Three inbred lines are required to produce F1 seed; the male-sterile line (A), the maintainer line (B), necessary for the perpetuation of the male-sterile line and a third consanguineous line, not related to the previous ones (C) that has good combining capacity with line A and is male-fertile. Crossing AxC originates the hybrid seed or F1 while crossing AxB is used to multiply line A. In commercial fields for seed production, A and C are planted and their crossing is important for the reproductive success of the plants.

The authors stated that “the 4:1 ratio of sterile/fertile plants was used, which is typical in onion commercial seed production”, however, is there any factors such as genotype and different growth ration affected seed yield? If the authors use different system, especially when they use MSL, the yield is also affected the compatibility with different genotypes. The field disposition of the fertile and sterile lines has been the subject of several studies, being 3:1 and 4:1 the distributions that are generally used between MSL and the OP line in commercial crops. The distribution of pollen in the field follows a logarithmic relationship with respect to the distance from the fertile plants; therefore at a distance of 2.1 m its quantity decreases by half compared to 30 cm. Seed companies prove this distribution before releasing the materials to the growers. Companies use male lines that have the best compatibility with each female line and it depends on the genotype of the used materials. 

Reviewer 3 Report (Previous Reviewer 1)

Dear authors,

You have corrected all technical errors, but not the essence. Based on the problem of the work, the introduction, the design of the experiment, the results, the conclusion and the cited literature were correctly written. All this is well presented based on the results of the work. But, the paper still does not have enough research and results, it does not have enough volume and depth, to be published in a journal with a large IF. For that reason, I still consider that this paper should be sent to some journal with a weaker IF, it's not for publication in Hotriculturae. 

Best regards

Author Response

We have accepted the reviewers´ suggestions and introduced the changes in the new versions of the manuscript. We consider that the modifications introduced have resulted in a better presentation and we hope the new version can be considered for publication in Horticulturae.

Round 2

Reviewer 2 Report (Previous Reviewer 2)

Thank you for your effort to repsonse my  questions. However, I am wondering that the authors may not canth my meaning. You don't need to explain some comceptions about male steril system because I am a breeder as well. My question is bunching onion is a hybrid line while onion was a male sterile line regardless a corresponding fertile line was planted for onion. But you did not say the fertilize is a maintainer or restorer? Are they will affect nectar sugar content? But I still insist my opinion that it is not suitable for the comparison between a hybrid and a male sterile system.

Author Response

We apologize for not understanding what the reviewer meant to say. The fertile line is a restorer. We think that this issue does not affect nectar sugar content. Our previous works show that nectar is highly related to the genotype and the environmental conditions, that is why in this work we studied the same line through different seasons and locations. However, we have continued studying other lines apart from the ones shown in the manuscript and the results are consistent with the results obtained in this manuscript. We consider that the strength of our research is that we have used the lines that these days are available for producers, making our research more relevant and applicable.  Nevertheless is a good point the reviewer´s opinion.

Reviewer 3 Report (Previous Reviewer 1)

Dear Authors,

I think that the paper has improved in quality, with the corrections made, so I suggest that it be accepted for publication in Horticulturae.

Best regards

Author Response

We sincerely thank you for your time and consideration and your suggestions.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Dear Authors,

Your manuscript is original and has practical significance, more for agricultural activities than for horticultural ones, so I think that the paper was more suitable for Agronomy journal.

Corrections and suggestions would be as follows:

- line 32-33 and 91: Species names are not written in italic.

- line 124-125: It was not explained how the seed yield was calculated. If it is only based on weight measurement, then it is not enough, since seed yield is a complex quantity. If the yield is calculated on the basis of a formula, then it is necessary to state it or cite the appropriate reference.

- Figure 1 is poor resolution.

- line 181-183: Confirmation of this sentence does not exist in the Results, so, it is needs to explain how you came to these conclusions.

- line 228-230: For this claim a reference is required.

- Almost all results do not show statistical significance.

Best regards

Reviewer 2 Report

Improve seed yield both for onion and bunching onion is of importance for seed producer. There are many factors affect seed production including the nectar sugar content in plant species. The authors compared the sugar profile in the onion and bunching onion nectar. They found significant difference of sugar profile between two plant species. Further, the fructose content is significantly associated with seed yield while no significant correlations were found between seed yield and other climatic factors. They also noted that different growth location can also affect seed yield of onion and bunching onion. The finding is interesting and useful for seed producers. However, I do not recommend this manuscript for publication at current stage. My main concerns as listed below.

1. In ABSTRACT section, there is too many research background, please use concise mode. Furthermore, the main result should be presented critical data supporting mode.

2. In INTRODUTION section, the logical is very poor for why do you want to study? How about the research background with relationship between nectar sugar profile and seed yield in other plant species. Furthermore, I think that the link between them should not be direct because the successful pollination will be affected by insects such as bee and other media such as wind. The hypothesis is also not clear. I advise the authors to re-structure this part.

3. In MATEIRALS AND METHODS section, why do the authors use hybrid for bunching onion and male sterile line for onion? You should clearly stated that the interspecific line Allium fistulosum x Allium cepa is bunching onion. What is fertile line for onion? I think there is no comparability between a hybrid and a system including male sterile and fertile. Further, the fertile line is a maintainer or restorer for this male sterile line? The authors stated that “the 4:1 ratio of sterile/fertile plants was used, which is typical in onion commercial seed production”, however, is there any factors such as genotype and different growth ration affected seed yield?

4. In RESULT section, why do you combined the correlation analysis between sugar profile and seed yield for bunching onion and onion?

5. In DISCUSSION section, L239, since the authors claimed that “the flowering cycle of bunching onion is about 20 days earlier than onion” is an advantage for bunching onion, why the flowering time was the same (L99)?

6. Other places should be noted. For example, L68 Allium fistulosum x Allium cepa is in italic but L91 was not. Line 95, 96, the expression of 20 bulbs m-1 should be in superscript for the unit. In Figure 2, there are no bars for SD.

Reviewer 3 Report

In the present manuscript, the authors attempted to conduct research and analysis on "Is the nectar sugar content the key to improve onion and bunching onion seed yield?" However, just measuring onion yields and sugar composition in two regions is far from telling the story. Environmental factors have a strong influence on plant growth, development, and yield, and the authors only showed maximum and minimum temperatures (ºC), maximum and minimum relative humidity (%), wind speed (m/s) during crop season for the different locations and productive seasons, and attempted to show that environmental factors correlate with sugar content are particularly far-fetched.

 

If the impact of environmental factors on yield is to be highlighted, then the different environmental factor variables should be controlled.

 

If the effect of sugar composition on yield is to be emphasized, then the sugar content of onions at different times of growth should be continuously observed. Also, onions should be planted under controlled environmental conditions.

 

 

Overall, the current research content does not confirm the essence of the topic. In fact, gene expression and metabolic component detection related to sugar synthesis are also helpful in this study. 

Reviewer 4 Report

Dear Authors,

I was curious to review a manuscript entitled: "Is the nectar sugar content the key to improve onion and bunching onion seed yield?" by Verónica C. Soto, Roxana E. González, Cristian A. Caselles and Claudio R. Galmarini.

The aim of the research presented in this manuscript was "to determine the differences in nectar sugar composition and sugar concentration between onion and bunching onion lines and the relationship of these sugars with seed yield."

Undoubtedly, the research presented in this manuscript is innovative and deserves to be published. Before that, the manuscript requires a number of clarifications and additions. My comments are below:

1) Abstract: Lines 15-16 are unnecessary here, please move to the Introduction section. Instead, please add an outline of your research hypothesis in the Abstract.

2) Keywords: please enter in alphabetical order. "Seed yield" is already in the title of the manuscript, so it can be removed from the "Keywords" section.

3) Introduction: the purpose of the research has been well presented, but please formulate a clear research hypothesis.

4) Materials and Methods:

a) Line 91 - "Allium fistulosum x Allium cepa" please write in italics.

b) Lines 95-96 - what does "m-1" mean?

c) Lines 91-100 - please specify the type of soil in both locations and specify the physicochemical properties of the soil in detail. Please provide the start dates of field trials and harvest. Please also provide details on fertilization of onion plants. What was the design of the field experiment, how many repetitions were there, how many plants were there in the repetition?

d) Line 107 - nectar from "50 umbels per plot" was tested, but were one or more umbels from the plant considered?

e) Lines 120-125 - how was the yield measured? k/ha?

5) Results:

a) Table 1 - shouldn't there be dots instead of commas in the last column?

b) Table 2 - Lines 156-157 - instead of (Max of Temp), (Min of Temp), (ΔT), (Max of HR) and (Min of HR) it should be (Tmax), (Tmin), ( RH max), (RH min), and (Delta T). Please make similar changes in Table 3.

c) Table 3 - Line 186 - under the table is: "*, **, *** significant at P ≤ 0.05, 0.01, and 0.001 respectively" - and in the table there is only **, therefore * and *** are unnecessary. Additionally, please check if * = 0.005 and ** = 0.001 ??? This is probably an error.

6) I have the impression that the list of publications cited in the manuscript is too poor.

7) Please adapt the entire manuscript to the requirements of the template used in the journal Horticulturae.

To sum up, the results presented in the manuscript are interesting and deserve to be published, provided that the Authors respond to the above comments beforehand.