The Growth-Promoting Ability of Serratia liquefaciens UNJFSC 002, a Rhizobacterium Involved in Potato Production

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Need corrected part

1.The name of the bacteria on species level (S. liquefaciens) and Latin name of plant should be italicized, such as Line 20, Line 50, etc. , checked the whole manuscript; Unified the bacteria name of "Serratia liquefaciens",The full name is used for the first appearance, and the abbreviation can be used for the second time as "S. liquefaciens"

2. Line 50: No need to introduce Bacillus spp., focus on serratia spp. only.

3. Line 63-70, This paragraph  should be deleted, cause this manuscript study on S. liquefaciens only. It can be statement in discussion section to compared this two strains.

4. Line 158, where is "PSF" in Tbale 1? maybe it is "FDW". 

5.Line 224 The pictures of the test results are more persuasive than table only.

Question

1.Where is the method for  agronomic traits of plant ? 

2.In terms of the logic of the experimental design. First , author should identify whether this strains have capacity to promote plant growth (in vitro); second verify this capacity on plant if tested was positive (in vivo).

3. Where are the statements of significant difference between each data in these figures?( both in picture and notes of these figures)

Author Response

1.The name of the bacteria on species level (S. liquefaciens) and Latin name of plant should be italicized, such as Line 20, Line 50, etc., checked the whole manuscript; Unified the bacteria name of "Serratia liquefaciens", The full name is used for the first appearance, and the abbreviation can be used for the second time as "S. liquefaciens"

Thanks for the suggestions.
Names that were not in that format were changed to italics, and S. liquefaciens was changed too.

2. Line 50: No need to introduce Bacillus spp., focus on Serratia spp. only.

Bacillus thuringiensis was removed from the paragraph
3. Line 63-70, This paragraph should be deleted, cause this manuscript study on S.

liquefaciens only. It can be statement in discussion section to compared this two strains.

The paragraph you indicated was deleted and was included in Discussion section.

4. Line 158, where is "PSF" in Tbale 1? maybe it is "FDW".

Agreed. The acronym PSF was changed to DFW in the table

5. Line 224 The pictures of the test results are more persuasive than table only.

There are no good images of the tests, and as a Communication it seems to me that there is a limit to the number of images. Some photos have been included in the Supplementary Material section.

Question
1.Where is the method for agronomic traits of plant ?

Indeed, the experimental part on agronomic evaluation has been omitted, and section 2.5 has been included.

2.In terms of the logic of the experimental design. First , author should identify whether this strains have capacity to promote plant growth (in vitro); second verify this capacity on plant if tested was positive (in vivo).

Agreed. The order of the experimental design was changed, starting with the laboratory phase (in vitro) and then the greenhouse phase (in vivo).

3. Where are the statements of significant difference between each data in these figures?( both in picture and notes of these figures)

The following has been added in the notes and pictures to Figures 1-4: Error bars and significance letters have been added to the figures.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The application of PGPR strains in agriculture remains a key research focus. This study demonstrated that S. liquefaciens UNJFSC 002, a strain isolated and screened from the crop rhizosphere, exhibits significant potato growth-promoting effects, suggesting considerable potential for its use in future biofertilizer development. The research presented in this paper holds substantial applied value.

Q1: The inoculation concentration employed was 1 × 10⁷ CFU mL⁻¹. Please justify the rationale for selecting this specific concentration. Furthermore, clarification is required regarding whether the secondary metabolites produced by the strain when cultured in nutrient broth (used as the inoculum carrier) exert any effect on plants.

Q2: Please incorporate a section in the Discussion addressing/comparing the differential inoculation effects observed among distinct bacterial species. This addition would better highlight the comparative advantages of the strains investigated in this study.

Author Response

REVISOR 2

The application of PGPR strains in agriculture remains a key research focus. This study demonstrated that S. liquefaciens UNJFSC 002, a strain isolated and screened from the crop rhizosphere, exhibits significant potato growth-promoting effects, suggesting considerable potential for its use in future biofertilizer development. The research presented in this paper holds substantial applied value.

 

Thanks for the suggestions. The submitted manuscript is a communication that presents some findings and advances from the laboratory and greenhouse, which may be of interest to other researchers working on the inoculation of S. liquefaciens in potatoes.

 

Q1: The inoculation concentration employed was 1 × 10⁷ CFU mL⁻¹. Please justify the rationale for selecting this specific concentration. Furthermore, clarification is required regarding whether the secondary metabolites produced by the strain when cultured in nutrient broth (used as the inoculum carrier) exert any effect on plants.

 

There are references to concentrations between 1 × 107 and 1 × 108 CFU mL (Palacio-Rodríguez et al., 2022; Tsegaye et al., 2022; Macías-Holguín et al., 2023). This topic is addressed in the revised Discussion. Regarding the production of secondary metabolites by the bacteria, this objective was not considered in the focus of the work.

http://dx.doi.org/10.57188/manglar.2023.017. 

https://doi.org/10.29312/remexca.v13i28.3278 

https://doi.org/10.3389/fmicb.2022.896770 

 

Q2: Please incorporate a section in the Discussion addressing/comparing the differential inoculation effects observed among distinct bacterial species. This addition would better highlight the comparative advantages of the strains investigated in this study.

 

References on the observed inoculation effects of other bacterial species (Bacillus sp., among others) have been incorporated in the Discussion section.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents a study on Serratia liquefaciens UNJFSC 002 and its potential to promote potato growth. The topic is interesting; however, the manuscript itself requires substantial revisions.

General Comments

The title does not reflect the content of the manuscript — the study presents only the strain's ability to promote potato growth, not its characterization. Also, the term “production” in the title may be misleading. I recommend revising it to emphasize “growth promotion” or “cultivation” of potato plants.

The manuscript currently lacks balance: the majority of the experimental data concerns plant response to inoculation, but these results receive only minimal discussion, limited to a single sentence in the Discussion section, while the bacterial component, based on general, non-quantitative or previously published observations, is highlighted.

Methodology needs clarification regarding how the experiments were performed.

I would present the Results in a different order – start with the selected bacterial traits, then proceed to the plant-based experiments.

The Discussion does not engage with the authors’ own data. As it stands, one could simply change the strain name and cite other publications, and the text would fit any article on any bacterium. It would be better in the Discussion to highlight the advantages of this strain, explain what makes it unique or superior, and why it would be particularly useful in potato cultivation.

Abstract

1. The abstract lacks a clearly defined objective. It repeats some information multiple times. For example, auxins and nitrogen fixation are mentioned four times: implying that genes might be investigated, then that this trait will be measured, then twice reporting that the strain produced auxins. The abstract should be more concise, include concrete numerical data on plant growth promotion, and end with a concluding sentence.

2. The first sentence is unclear — what does it mean that Serratia “could harbor multiple genes”? Since the study does not include a genome analysis, I suggest focusing on the strain’s biochemical capabilities, or stating why new PGPR strains are being sought or why potatoes were chosen as the test plant.

3. The strain name Serratia liquefaciens should always be italicized throughout the manuscript.

4. Terms like in vitro should also be italicized.

Introduction

5. First sentence: Not all plant growth‑promoting bacteria (PGPB) are rhizobacteria, which are root-associated microorganisms.

6. The statement that rhizobacteria enhance the availability of plant-synthesized phytohormones is ambiguous and should be clarified or rephrased.

7. The Introduction needs rewriting. The second sentence describes plant‑growth mechanisms, then lines 43 and 47 repeat the same content. The sentence on heavy metal accumulation is unnecessary in a study on edible crops. Similarly, the note on larval mortality — if the authors intend to use it for insect biocontrol, this needs to be expanded in the Discussion.

8. Genomic content (e.g., genome size, pseudogene count) of other strain is not relevant to this study unless comparative genomics is performed. Consider instead citing recent genome-based studies on Serratia liquefaciens (e.g., Aloo et al., 2024, Microbiology Resource Announcements 10.1128/mra.00772‑24) and focusing on relevant PGP traits.

9. It would also be worthwhile to note any potential environmental risks, since many Serratia strains are pathogenic.

10. It’s also missing an explanation for why the authors chose three bacterial traits (auxins, phosphorus and nitrogen fixation) among many PGP characteristics.

Methods

Section 2.1: Was the growth medium for potatoes sterile, or did it contain indigenous soil microbiota?

Section 2.2: The experimental design (lines 97–100) is unclear and must be clarified.

Section 2.3:

The timeline for bacterial preparation is inconsistent. The authors state that bacteria were grown on TSA for 24h before plant inoculation. When and how were they cultured in liquid medium? How did they measure cell count or biomass?

Details about control plants are absent. Were they treated similarly (e.g., dipped in broth)? How many days did the experiment last?

Clarify the plant parameters assessed, justify differences in measurement between cultivars (Tables 3 vs. 4), and explain how those parameters were quantified (e.g., measuring scales or instruments used).

Section 2.4:

How was phosphate solubilization measured? Phrases like “the reading was observed” are not sufficient. Can the authors provide photos in the Supplementary? Under what conditions was this ability tested? What was the inoculum concentration, and how many biological and technical replicates were used?

For IAA production – similar questions as above, plus: did the Authors use only supernatant or the entire culture? How was the color change intensity assessed?

For nitrogen fixation – similar questions as above, plus: if a visual method was used, was a reference strain included as a positive/negative control?

Section 2.5: There’s an inconsistency: Section 2.5 mentions 20 replicates, but Section 2.3 mentions 30 tubers.

 Results

Section 3.1.1:

Please clarify whether NPK fertilizer was applied only to control plants. If so, add this information on Figures e.g. control (+NPK).

Indicate the number of replicates below all tables and figures.

Table 3 and 4. Remove redundant mention of bacterial inoculum concentration (already described in Methods). The duration experiment (30 or 120 days) should be part of the table. Which potato cultivar do the data represent – is it the average of all cultivars?

Do Figures 1 and 2 display data from Table 3? The figures lack polish: adjust axis scaling to minimize unused space, and the sample order (treated vs control) is inconsistent. Add statistical significance indicators. Consider presenting both figures side-by-side to conserve space. Why were only TWP and TD chosen for the Figure representation?

It would be helpful if the Authors add some comparative photos/images of control vs inoculated plants as supplementary materials.

When discussing results per cultivar, indicate which differences are statistically significant.

Section 3.1.2: Suggestions are similar to those for Section 3.1.1.

Section 3.3: For a single bacterial strain, it would be better to use photos of the assays rather than a table where the only result is “+”.

Discussion

Lines 227–231: Quantitative comparisons with data from publication [20] would strengthen the interpretation.

Clarify whether the same strain (UNJFSC 002) was used in references [21] and [22].

Line 239: Use the correct abbreviation “IAA” instead of “AIA.”

Line 247: I disagree with the statement that ' The present work confirms through in vivo and in vitro tests that this strain has potential for biofertilization, growth regulation and biodefense’ – The Authors did not assess biocontrol activity.

Please strengthen the discussion with a clearer focus on findings.

Comments on the Quality of English Language

The language needs significant improvement – at times, it is difficult to follow the authors’ line of reasoning.

Author Response

REVISOR 3

 

The manuscript presents a study on Serratia liquefaciens UNJFSC 002 and its potential to promote potato growth. The topic is interesting; however, the manuscript itself requires substantial revisions.

 

Thanks for the suggestions. The submitted manuscript is a communication that presents some findings and advances from the laboratory and greenhouse, which may be of interest to other researchers working on S. liquefaciens in potatoes. The research group is preparing another manuscript on the genomic analysis of the strain S. liquefaciens UNJFSC 002.

General Comments

 

• The title does not reflect the content of the manuscript — the study presents only the strain's ability to promote potato growth, not its characterization. Also, the term “production” in the title may be misleading. I recommend revising it to emphasize “growth promotion” or “cultivation” of potato plants.

 

Agreed. The title was corrected to: Growth-promoting ability of Serratia liquefaciens UNJFSC 002, a rhizobacterium involved in potato production.

• The manuscript currently lacks balance: the majority of the experimental data concerns plant response to inoculation, but these results receive only minimal discussion, limited to a single sentence in the Discussion section, while the bacterial component, based on general, non-quantitative or previously published observations, is highlighted.

 

Agreed. The Discussion has been enhanced to incorporate the greenhouse experimental data.

 

 

• Methodology needs clarification regarding how the experiments were performed.

 

Section 2.5 has been added to the Methodology section, which had been omitted from the manuscript.

• I would present the Results in a different order – start with the selected bacterial traits, then proceed to the plant-based experiments.

 

Agreed. The order of the experimental design was changed, starting with the laboratory phase (in vitro) and then the greenhouse phase (in vivo).

The Discussion does not engage with the authors’ own data. As it stands, one could simply change the strain name and cite other publications, and the text would fit any article on any bacterium. It would be better in the Discussion to highlight the advantages of this strain, explain what makes it unique or superior, and why it would be particularly useful in potato cultivation.

Agreed. The data from the research have been incorporated into the discussion, and the effect of inoculation has been quantitatively indicated.

 

Abstract

Resumen

1. 1. The abstract lacks a clearly defined objective. It repeats some information multiple times. For example, auxins and nitrogen fixation are mentioned four times: implying that genes might be investigated, then that this trait will be measured, then twice reporting that the strain produced auxins. The abstract should be more concise, include concrete numerical data on plant growth promotion, and end with a concluding sentence.

 

Agreed. The comments made to the summary have been corrected.

 

2. The first sentence is unclear — what does it mean that Serratia “could harbor multiple genes”? Since the study does not include a genome analysis, I suggest focusing on the strain’s biochemical capabilities, or stating why new PGPR strains are being sought or why potatoes were chosen as the test plant.

 

Agreed. The text was corrected. 

 

3. 3. The strain name Serratia liquefaciens should always be italicized throughout the manuscript.

 

Agreed. Names that were not in that format were changed to italics, and S. liquefaciens was changed too.

4. 4. Terms like in vitro should also be italicized.

 

Accordingly, the terms in vivo and in vitro, in italics, have been redacted.

Introduction

 

5. 5. First sentence: Not all plant growth‑promoting bacteria (PGPB) are rhizobacteria, which are root-associated microorganisms.

The reviewer is correct, but in this case, S. liquefaciens UNJFSC 002 was isolated from the rhizosphere of a potato crop.

6. The statement that rhizobacteria enhance the availability of plant-synthesized phytohormones is ambiguous and should be clarified or rephrased.

 

This is a cite from the references consulted [2] and the authors of the article agree with it.

 

7. The Introduction needs rewriting. The second sentence describes plant‑growth mechanisms, then lines 43 and 47 repeat the same content. The sentence on heavy metal accumulation is unnecessary in a study on edible crops. Similarly, the note on larval mortality — if the authors intend to use it for insect biocontrol, this needs to be expanded in the Discussion.

 

Agreed. The Introduction was reworded to avoid redundancy in the wording. What this part of the Introduction seeks to establish is that S. liquefaciens has been studied in various aspects related to biotic and abiotic stresses.

 

8. Genomic content (e.g., genome size, pseudogene count) of other strain is not relevant to this study unless comparative genomics is performed. Consider instead citing recent genome-based studies on Serratia liquefaciens (e.g., Aloo et al., 2024, Microbiology Resource Announcements 10.1128/mra.00772‑24) and focusing on relevant PGP traits.

 

Agreed. The publication by Klein et al. (2025) was reviewed and was included in the discussion since the suggested publication by Aloo et al. (2024) was not found. Note that we cited Aloo et al. (2021).  Also, the publication of Rodriguez-Grados et al. (2024) was included. 

9. 9. It would also be worthwhile to note any potential environmental risks, since many Serratia strains are pathogenic.

 

According to the available information, the strains with potential environmental risks to human health are mainly from S. marcescens; to the best of our knowledge, they have not been identified in S. liquefaciens (see Reference 27).

 

10. 10. It’s also missing an explanation for why the authors chose three bacterial traits (auxins, phosphorus and nitrogen fixation) among many PGP characteristics.

 

These three characteristics (biological N fixation, P solubilization and auxin production) were chosen because of their importance in plant nutrition and plant growth regulation. There are certainly other characteristics of PGPs (e.g., those related to plant health) that have not been taken into account, but the present work is a communication that exposes some findings that could be of interest to other colleagues working complementarily in this field of research.

Methods

 

Section 2.1: Was the growth medium for potatoes sterile, or did it contain indigenous soil microbiota?

 

The substrate for culture was commercially available, unsterilized. The characteristics of this medium can be seen in Appendix 1.

Section 2.2: The experimental design (lines 97–100) is unclear and must be clarified.

 

The experimental design in the greenhouse was completely randomized with 20 replications for each treatment and variety. It was added in section 2.6 that separate experiments were developed for potato varieties for direct consumption and for processing.

Section 2.3:

The timeline for bacterial preparation is inconsistent. The authors state that bacteria were grown on TSA for 24h before plant inoculation. When and how were they cultured in liquid medium? How did they measure cell count or biomass?

 

In section 2.1 Preparation of the bacterial inoculum, bacterial preparation is described. The bacterial colony density was counted with a Tecnal model CP600 digital colony counter.

Details about control plants are absent. Were they treated similarly (e.g., dipped in broth)? How many days did the experiment last?

 

Control plants were immersed in distilled water for 5 minutes. The experiment lasted 120 days from tuber planting.

 

Clarify the plant parameters assessed, justify differences in measurement between cultivars (Tables 3 vs. 4), and explain how those parameters were quantified (e.g., measuring scales or instruments used).

 

Section 2.5 shows the parameters evaluated in the measurements, which were made separately in potato varieties for direct consumption and frying, due to the different characteristics of each varietal group.

Section 2.4:

 

How was phosphate solubilization measured? Phrases like “the reading was observed” are not sufficient. Can the authors provide photos in the Supplementary? Under what conditions was this ability tested? What was the inoculum concentration, and how many biological and technical replicates were used?

 

Some photos have been included in the Supplementary Material section. Unfortunately, the photos do not have good resolution.

For IAA production – similar questions as above, plus: did the Authors use only supernatant or the entire culture? How was the color change intensity assessed?

 

The whole culture was used, absorbance was evaluated at 540 nm with a standard sample in a spectrophotometer (SmartDrop). Some photos of this topic have been included in the Supplementary Material section.

 

 

For nitrogen fixation – similar questions as above, plus: if a visual method was used, was a reference strain included as a positive/negative control?

 

We did not use a positive control; only a negative control was used, which was the uninoculated sample.

Section 2.5: There’s an inconsistency: Section 2.5 mentions 20 replicates, but Section 2.3 mentions 30 tubers.

 

The text has been corrected, and the correct number is 20.

 Results

 

Section 3.1.1:

Please clarify whether NPK fertilizer was applied only to control plants. If so, add this information on Figures e.g. control (+NPK).

 

NPK fertilizer was applied only to control plants. 

 

Indicate the number of replicates below all tables and figures.

 

Accordingly, the number of replicates was placed in tables and figures.

 

Table 3 and 4. Remove redundant mention of bacterial inoculum concentration (already described in Methods). The duration experiment (30 or 120 days) should be part of the table. Which potato cultivar do the data represent – is it the average of all cultivars?

 

Agreed. The observations mentioned by the reviewer have been corrected. The requests for tables 3 and 4 have been included. The data represent the average of the potato varieties.

 

Do Figures 1 and 2 display data from Table 3? The figures lack polish: adjust axis scaling to minimize unused space, and the sample order (treated vs control) is inconsistent. Add statistical significance indicators. Consider presenting both figures side-by-side to conserve space. Why were only TWP and TD chosen for the Figure representation?

 

Figures 1 and 2 show the inoculation responses for each variety. Table 3 represents the average performance of the varieties for inoculation. Error bars and significance letters have been added to the figures. The variables TWP and TD were considered to be the ones that showed the effect of inoculation on potato varieties more clearly.

It would be helpful if the Authors add some comparative photos/images of control vs inoculated plants as supplementary materials.

 

Photographs of inoculated plants of potato varieties for processing and direct consumption have been incorporated as supplementary material.

When discussing results per cultivar, indicate which differences are statistically significant.

 

The discussion has been improved by indicating the significant differences between treatments (control vs. inoculated) of the variables studied.

 

Section 3.1.2: Suggestions are similar to those for Section 3.1.1.

 

Se han considerado tales sugerencias en el texto.

 

Section 3.3: For a single bacterial strain, it would be better to use photos of the assays rather than a table where the only result is “+”.

 

The photographs are low resolution, but some of them are being included.

Discussion

 

Lines 227–231: Quantitative comparisons with data from publication [20] would strengthen the interpretation.

Resp:

The comparisons in this reference have been added to the discussion section.

Clarify whether the same strain (UNJFSC 002) was used in references [21] and [22].

In both references, other Serratia strains were used. The discussion was partially corrected by indicating that both references were other strains of Serratia spp.

Line 239: Use the correct abbreviation “IAA” instead of “AIA.”

 

Corrected the abbreviation IAA.

 

Line 247: I disagree with the statement that ' The present work confirms through in vivo and in vitro tests that this strain has potential for biofertilization, growth regulation and biodefense’ – The Authors did not assess biocontrol activity.

 

Correct. The word biodefense was removed from that statement.

 

Please strengthen the discussion with a clearer focus on findings.

 

The Discussion section has been improved with new citations and references.

 

Comments on the Quality of English Language

The language needs significant improvement – at times, it is difficult to follow the authors’ line of reasoning.

 

The comprehensibility of the manuscript has been improved, with a new revision of the English language.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors 1、All figures in this manuscript need to be redrawn to improve their aesthetics. 2、The dosage of bacterial strains in the experimental content is too single, which leads to obvious limitations. 3、Original data and photos need to be provided to reflect the completeness of the study. 4、The conclusions need to be rewritten. All revised parts in the manuscript should be marked in red, and strikethrough should not be used.

Author Response

1.、All figures in this manuscript need to be redrawn to improve their aesthetics.

Figures 1, 2, 3 and 4 have been modified to improve aesthetics by removing the error bars since another reviewer stated that the statistical significance letters should be included.

2、The dosage of bacterial strains in the experimental content is too single, which leads to obvious limitations. 

The applied dose of inoculum 1 x 107 is found in references 14, 20, 34. Likewise, to ensure the presence of sufficient inoculum of the bacterium in the plants, a second inoculation at the same dose was carried out at the potato flowering stage.

3、Original data and photos need to be provided to reflect the completeness of the study. 

A Supplementary File has been included with photographs of the inoculated and control plants in the greenhouse, as well as photos of the laboratory phase.

4、The conclusions need to be rewritten. All revised parts in the manuscript should be marked in red, and strikethrough should not be used.

Thanks for the suggestion. The conclusions of the paper have been modified, indicating the most important findings. All modified sections of the manuscript are highlighted in red.

Thanks for the revision to improve the manuscript.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you to the authors for implementing the suggested revisions.

The methodological section of the manuscript has been improved.

However, two technical issues still require clarification:

1) I agree that the bacterial count can be determined using a colony counter (e.g. Tecnal) . However, this is only possible several hours after the bacteria have been plated on agar. My question was: how did the Authors determine the bacterial concentration at the very moment when the potato tubers were immersed in the broth?

2) It would also be advisable to include in the methodology that the potato cultures were inoculated with the bacteria twice: first, by surface application to the tubers, and a second time after 45 days of the experiment. In this context, I have a further questions:

• how exactly was the second inoculation of the pots conducted?
• how many bacterial cells were introduced into the pots during this second inoculation?
• on what basis did the authors determine that a second inoculation was necessary?
• the captions under the tables mention that the potatoes were inoculated with the bacteria at the time of planting; however, it should specify that the inoculation was performed twice

 

Others suggestions:

Line 86 The isolates were cultured in the nutrient broth and incubated in the NBRIP medium for 5 days.

Since the study investigated only one factor (bacterial inoculation), the use of the term "significant interaction" throughout the Results section is not appropriate. This expression implies the presence of interactions between at least two factors influencing plant growth, which is not the case in this study.

Lines 259-262 ”Other authors [20] found that bacteria isolated from compost teas (Serratia spp.) are nitrogen fixers, phosphate solubilizers and producers of phytohormones IAA and siderophores, which would explain their beneficial effect on potato growth and yield. “ This statement should be moved and combined with information from the paragraph lines 271-278. First, provide information about the ability of bacteria to produce IAA and others, then summarize that it could influence the growth and development of the potato.

Line 274 -not  PGP but PGPB or PGPB

Answer to my former question about the Introduction and first sentence. In my humble opinion, if Authors want to use the abbreviation PGPR, they should clearly state that they mention bacteria associated with roots and soil near plant roots. Not all bacteria that promote plant growth are rhizobacteria.

Although the graphs appear too large in my opinion (axis titles should be enlarged, while the overall graph size could be reduced), I will not object if the other reviewers find them acceptable.

Comments on the Quality of English Language

English needs further improvement – below the Authors can find some chosen suggestions

Line 98 “After this period, nitrogen fixation activity was evaluated in vitro through visual inspection, grading the intensity of the cream to yellow color change” (intensity of the color change from cream to yellow)

Line 108 “Two types of potato varieties cultivated in Peru were used in the greenhouse experiments: commercial varieties intended for direct consumption (Table 1) and processing varieties intended for frying (Table 2), to obtain information on the growth-promoting effect of the bacterial strain S. liquefaciens UNJFSC 002 on potato varieties cultivated in Peru.

Line 130 screen house/// greenhouse

Lines 174-179, require substantial language revision, as the current phrasing makes it difficult to determine which factor affected which parameter, e.g. “the inoculation in the Perricholi variety was greater than in the Única and Canchan varieties” – it suggests that more bacteria were used for inoculation of Perricholi than other varieties of potatoes. A similar suggestion can be found e.g. in lines 246-247 “In commercial potato varieties, the increase of inoculation with S. liquefaciens UNJFSC 002 concerning the control”.

Lines 256-259: The sentences “The concentration used for bacterial inocula of S. liquefaciens UNJFSC 002 1x107 CFU mL was similar in the mentioned work, which had a significantly higher effect on the number and weight of potato tubers. This would indicate that at this level, inoculation of seed potato tubers could improve tuber yield.” need rewriting – which mentioned work? Higher from what and in which work the results were better (yours or any of those mentioned earlier)? The Authors should remember that they used solution of bacteria in a concentration of 1x107, but they used it twice, not once (at the beginning and after 45 days), and we still don’t know how many bacteria were inoculated into pots after 45 days.

Authors often use term “inoculating S. liquefaciens UNJFSC 002 in potato plants.” It should be: of potato tubers/soil or potato plants inoculated with S...

Author Response

Thank you to the authors for implementing the suggested revisions.

Your suggestions improved the manuscript. Thanks.

The methodological section of the manuscript has been improved.

However, two technical issues still require clarification:

1) I agree that the bacterial count can be determined using a colony counter (e.g. Tecnal). However, this is only possible several hours after the bacteria have been plated on agar. My question was: how did the Authors determine the bacterial concentration at the very moment when the potato tubers were immersed in the broth?

The concentration of the bacteria was determined 24 hours after seeding in the culture medium. The final concentration was assumed to be the same, since the tubers were immersed in the inoculum source shortly after counting in the colony counter. Therefore, to ensure the presence of sufficient inoculum on the potato plants, a second inoculation was performed 45 days after planting, as described in the Methodology.

2) It would also be advisable to include in the methodology that the potato cultures were inoculated with the bacteria twice: first, by surface application to the tubers, and a second time after 45 days of the experiment. In this context, I have a further questions:

• how exactly was the second inoculation of the pots conducted?
• The second inoculation was carried out 45 days after planting, using the same concentration of inoculum previously prepared for this purpose. In this case, the application was made at the base of the growing plants, then more commercial substrate was added to each plant, until almost completing the contents of the pots.
•  
• how many bacterial cells were introduced into the pots during this second inoculation?
• The same initial concentration. For this purpose, a new inoculum was prepared again, and the colonies were counted 24 hours after seeding in the culture medium.
•  
• on what basis did the authors determine that a second inoculation was necessary?
• In some references (18, 34), a similar number of inoculations were performed on tomato and potato, respectively. There are other references that study this aspect of inoculation, but there is no absolute consensus on it.
•  
• the captions under the tables mention that the potatoes were inoculated with the bacteria at the time of planting; however, it should specify that the inoculation was performed twice.
• Agreed. This was added to the tables, specifying that two inoculations were performed in the greenhouse growing period.
•  

 

Other suggestions:

Line 86 The isolates were cultured in the nutrient broth and incubated in the NBRIP medium for 5 days.

1. The text was corrected.

Since the study investigated only one factor (bacterial inoculation), the use of the term "significant interaction" throughout the Results section is not appropriate. This expression implies the presence of interactions between at least two factors influencing plant growth, which is not the case in this study.

1. The text was corrected.

Lines 259-262 ”Other authors [20] found that bacteria isolated from compost teas (Serratia spp.) are nitrogen fixers, phosphate solubilizers and producers of phytohormones IAA and siderophores, which would explain their beneficial effect on potato growth and yield. “ This statement should be moved and combined with information from the paragraph lines 271-278. First, provide information about the ability of bacteria to produce IAA and others, then summarize that it could influence the growth and development of the potato.

Line 274 -not  PGP but PGPB or PGPB

Indeed, the correction has been implemented.

Answer to my former question about the Introduction and first sentence. In my humble opinion, if Authors want to use the abbreviation PGPR, they should clearly state that they mention bacteria associated with roots and soil near plant roots. Not all bacteria that promote plant growth are rhizobacteria.

Agreed. The term PGPB has been incorporated.

Although the graphs appear too large in my opinion (axis titles should be enlarged, while the overall graph size could be reduced), I will not object if the other reviewers find them acceptable.

Agreed. The graphics have been corrected to improve their visibility.

Comments on the Quality of English Language

English needs further improvement – below, the Authors can find some chosen suggestions

The comments below have been incorporated into the manuscript to improve the English translation:

Line 98 “After this period, nitrogen fixation activity was evaluated in vitro through visual inspection, grading the intensity of the cream to yellow color change” (intensity of the color change from cream to yellow)

Line 108 “Two types of potato varieties cultivated in Peru were used in the greenhouse experiments: commercial varieties intended for direct consumption (Table 1) and processing varieties intended for frying (Table 2), to obtain information on the growth-promoting effect of the bacterial strain S. liquefaciens UNJFSC 002 on potato varieties cultivated in Peru.

Line 130 screen house/// greenhouse

Yes, the corrections has been made.

Lines 174-179, require substantial language revision, as the current phrasing makes it difficult to determine which factor affected which parameter, e.g. “the inoculation in the Perricholi variety was greater than in the Única and Canchan varieties” – it suggests that more bacteria were used for inoculation of Perricholi than other varieties of potatoes. A similar suggestion can be found e.g. in lines 246-247 “In commercial potato varieties, the increase of inoculation with S. liquefaciens UNJFSC 002 concerning the control”.

Lines 256-259: The sentences “The concentration used for bacterial inocula of S. liquefaciens UNJFSC 002 1x107 CFU mL was similar in the mentioned work, which had a significantly higher effect on the number and weight of potato tubers. This would indicate that at this level, inoculation of seed potato tubers could improve tuber yield.” need rewriting – which mentioned work?

References [14, 20, 34] were added to the manuscript.

 Higher from what and in which work the results were better (yours or any of those mentioned earlier)? 

The text was modified: The concentration used for bacterial inocula of S. liquefaciens UNJFSC 002 1x107 CFU mL was similar in previous works [14, 20, 34], which had a significantly higher effect on the number and weight of potato tubers concerning control plants

The Authors should remember that they used solution of bacteria in a concentration of 1x107, but they used it twice, not once (at the beginning and after 45 days), and we still don’t know how many bacteria were inoculated into pots after 45 days.

It is difficult to accurately determine the final concentration of inoculum on the plants, but we have an approximation with the colony count. The reason for the second inoculation at 45 days was precisely to try to ensure the presence of sufficient inoculum on the plants.

Authors often use the term “inoculating S. liquefaciens UNJFSC 002 in potato plants.” It should be: of potato tubers/soil or potato plants inoculated with S…

1. The text was corrected. 

Thanks for the revision.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

It is suggested to replace the line chart with a bar chart because the X-axis has only two coordinate points (treated and control).

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you to the Authors for their responses. The paper has been appropriately improved and can be published in the present form.