Comparison of Morphological Indexes and the Pathogenicity of Bursaphelenchus xylophilus in Northern and Southern China
Round 1
Reviewer 1 Report
In the manuscript (forests-1002918), the authors obtained new data on the the plant-parasitic nematode or pine wood nematode (PWN) Bursaphelenchus xylophilus that is the causal pathogen of pine wilt disease (PWD). In their study, authors have compared morphological characteristics of 8 southern strains and 8 northern strains of B. xylophilus in China. In combination, they have compared the pathogenicity of these 16 strains on Pinus thunbergii and Pinus tabuliformis.
We raised some questions on the presentation of the results that have to be addressed before the manuscript can be considered for publication. A resubmitted manuscript should include a geographic map showing the sampling location of the strains belonging to this pathogenic nematode species.
Did the authors compare morphological characteristics of B. xylophilus between the mycetophagous and phytophagous phases? Please, include that information in the manuscript.
Moreover, did the authors utilize DNA-based analysis on the 16 B. xylophilus strains of the study to elucidate phylogenetic relationships within this Bursaphelenchus species? Can the 16 B. xylophilus strains still be divided into northern and southern types by means of a DNA-based analysis, as this is the best method to understand their phylogenetic relationships? Were the strains collected from the same locality (year) characterized by means of DNA-based analysis? For instance, are strains LN03 and LN04 from Dalian city, Liaoning Province (P. thunbergii) (2016), phylogenetically different strains? Is the phylogenetic position of LN03 similar to that of LN04? As another example, LN14 and LN16 from Fushun city, Liaoning Province (L. gmelinii) (2018): are they phylogenetically different strains? Please, include that information in the manuscript for further discussion.
The authors assert that all the 16 strains showed strong pathogenicity to P. thunbergii with a similar disease progression, and greater difference in pathogenicity on P. thunbergii among the southern strains than that of the northern strains. Please, adequately discuss the new pathogenicity data in your manuscript in relation to previous results.
Concerning the sentence: “The northern strains are most likely to be carried in the north by some of the southern strains that are more suitable for the northern climate and host.” The meaning of this sentence is not clear. The hypotheses must be appropriately identified as such.
Please, adequately explain how your research has showed important data on the cause of the outbreak of PWNs in northern China.
I hope this helps.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear authors, I was honoured to read your manuscript and write a review on it. I am always pleased with any other scientific work associated with PWD. I rate the chosen topic as very current. I found a few inconsistencies in the text that I pointed out. I've also added notes and comments to the text to help you edit the manuscript. For a better understanding of the methodology, it would be appropriate to include a scheme or photo of inoculation of experimental plants. Additionally, it would be appropriate to supplement the map with sampling points and isotherm marking. Thank you for your scientific work.
Comments for author File: 
Comments.pdf
Author Response
Responses to reviewer comments
Manuscript ID: forests-1002918
Title: Comparison of morphological indexes and the pathogenicity of Bursaphelenchus xylophilus in northern and southern China
Responses to reviewer comments
Manuscript ID: forests-1002918
Title: Comparison of morphological indexes and the pathogenicity of Bursaphelenchus xylophilus in northern and southern China
Comments:
Dear authors, I was honoured to read your manuscript and write a review on it. I am always pleased with any other scientific work associated with PWD. I rate the chosen topic as very current. I found a few inconsistencies in the text that I pointed out. I've also added notes and comments to the text to help you edit the manuscript. For a better understanding of the methodology, it would be appropriate to include a scheme or photo of inoculation of experimental plants. Additionally, it would be appropriate to supplement the map with sampling points and isotherm marking. Thank you for your scientific work.
Reply：Thanks for your suggestions. Photos of inoculation experiment and maps of sampling locations were added to the manuscript. For more details, please check the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Lines 37-40: Do you have any citations backing this statement up? If so, please include them.
I think the authors need to better present the Figure 1 caption.
Line 61: “found through inoculation experiments on 18 species of PWN populations that the pathogenicity of …….”
Species? Populations? This should be clarified.
Lines 293-307: These are awkwardly worded sentences.
Throughout the manuscript there are many grammatical errors that need to be addressed. Please, improve the manuscript by means of editing of English language and style. I would suggest that a native English speaker/writer read over the manuscript before resubmission.
Please, include more information for the strains collected from the same locality (year). For instance, are strains LN03 and LN04 from Dalian city, Liaoning Province (P. thunbergii) (2016), different strains? Are LN14 and LN16 from Fushun city, Liaoning Province (L. gmelinii) (2018) different strains?
This seems like necessary information in my mind.
Please, adequately explain how your research has showed important data on the cause of the outbreak of PWNs in northern China.
Author Response
Responses to reviewer comments
Manuscript ID: forests-1002918
Title: Comparison of morphological indexes and the pathogenicity of Bursaphelenchus xylophilus in northern and southern China
Authors: Qing-Qing Kong, Xiao-Lei Ding, Yi-Fan Chen, Jian-Ren Ye *
The authors would like to thank the Editors and Reviewers for their constructive comments and suggestions to improve the quality of the paper. We have tried our best to revise our manuscript according to the comments and the comments have been answered point-by-point. In the revised manuscript, the places where have been modified will highlight by using the track changes mode in MS Word. Comments are listed below in bold font and our responses in regular blue.
Responses to Reviewer1:
Comments to the Author
- a) We raised some questions on the presentation of the results that have to be addressed before the manuscript can be considered for publication. A resubmitted manuscript should include a geographic map showing the sampling location of the strains belonging to this pathogenic nematode species.
Response: Map had been added.
- b) Did the authors compare morphological characteristics of xylophilusbetween the mycetophagous and phytophagous phases? Please, include that information in the manuscript.
Response:In this study, I did not compare the morphological characteristics of B. xylophilus between the mycetophagous and phytophagous phases, because the strains used in this experiment were all cultured by Botrytis cinerea. In addition, my focus is more on the morphological differences between the 16 strains, rather than the morphological differences under different feeding conditions.
- c) Moreover, did the authors utilize DNA-based analysis on the 16 xylophilus strains of the study to elucidate phylogenetic relationships within this Bursaphelenchus species?Can the 16 B. xylophilus strains still be divided into northern and southern types by means of a DNA-based analysis, as this is the best method to understand their phylogenetic relationships? Were the strains collected from the same locality (year) characterized by means of DNA-based analysis? For instance, are strains LN03 and LN04 from Dalian city, Liaoning Province (P. thunbergii) (2016), phylogenetically different strains? Is the phylogenetic position of LN03 similar to that of LN04? As another example, LN14 and LN16 from Fushun city, Liaoning Province (L. gmelinii) (2018): are they phylogenetically different strains? Please, include that information in the manuscript for further discussion.
Response: Thank you very much for your valuable comments. It is a very scientific method to use DNA analysis to cluster analysis of 16 strains. In this experiment, the geographical origin is mainly used as the division to compare the morphological characteristics. Because according to previous studies, we speculate that different environmental conditions, such as host species, and environmental temperature have certain effects on the pine wood nematode. In recent years, the occurrence and development trend of pine wood nematode disease in China has gradually developed from the south to the north, crossing the warning line with an average annual temperature of 10℃ to reach middle-temperate regions such as Liaoning Province. Therefore, this study closely follows this trend and aims to explore Whether the morphological and pathogenicity of the strains from the south to the north have changed. Of course, it is more accurate and scientific to use DNA analysis to determine the phylogenetic relationships. If we want to obtain a more reliable result through DNA cluster analysis, we need a large number of strains to analyze, which is still difficult for us and we will consider continuing to collect strains for DNA analysis in future experiments.
- d) The authors assert that all the 16 strains showed strong pathogenicity to thunbergii with a similar disease progression, and greater difference in pathogenicity on P. thunbergii among the southern strains than that of the northern strains. Please, adequately discuss the new pathogenicity data in your manuscript in relation to previous results.
Response: Thank you for your advice,related content has been added in the last paragraph of the discussion.
- e) Concerning the sentence: “The northern strains are most likely to be carried in the north by some of the southern strains that are more suitable for the northern climate and host.” The meaning of this sentence is not clear. The hypotheses must be appropriately identified as such.
Response: Appropriate explanation has been added to the conclusion to make this hypothesis more reasonable and fluent.
- f) Please, adequately explain how your research has showed important data on the cause of the outbreak of PWNs in northern China.
Response: The outbreak of PWN in northern China has been a trend in recent years, and specific data have been reflected in the investigation and research on this disease in recent years. The purpose of my research is to provide further evidence to explain the cause of the outbreak of PWD in northern China. The introduction and discussion in the manuscript have been supplemented.
