Landscape Epidemiology of Xylella fastidiosa in the Balearic Islands

Round 1

Reviewer 1 Report

This perspective paper reports a comprehensive overview on one of the most complex scenarios regarding Xylella in Europe. The paper correlates field evidences with innovative molecular tools for the investigations of the host-patogen interactions, making appropriate reference to the knowledge on this pathogen in other environments (i.e. in American countries). Given the lack of therapeutic formulations against this bacterium, I found very interesting the description of the influence of the climate and management of the crops as factors determining the severities of the Xylella-induced diseases. As indicated above, I recommend to have the whole text revised by a native English speaker.  

Author Response

Thanks for your comments. We have revised the whole text and edited the English language mistakes. 

Reviewer 2 Report

The manuscript presents a large study of Xf emergence and spread in Balearic Islands. The study is extremely important and current given the seriousness of the damage that this pathogen is producing in the productivity of various plant species. The goal of understanding how the various Xf strains spread across the various islands and their ability to infect different species was largely achieved by the authors. The information presented may be indispensable for targeted pathogen control actions.

Author Response

Thanks for your comments. We have revised the whole text and edited the English language mistakes. 

Reviewer 3 Report

I think this is a very valuable review for all pathologists interested in pathogen invasions.   Most of my detailed comments are slight changes to the English, but some need a little change or addition to allow the reader to understand the data, or avoid ambiguity.

22 "disjunct" or "disjoint"not "disjunctive"
23 "hold" not "concentrate"
77-92  We need to be told what the criteria were for testing a plant and whether (for example) sampling was clustered in any way around evidently diseased plants.
106-113 and generally.  Don't introduce unnecessary abbreviations  - the complicate reading considerably and in the electronic world we are not short of paper!  I don't think HKG is justified;  I am doubtful about MLST and I'm not sure why you don't follow the conventional way of abbreviating species names, though I don't think that is a problem in reading.
129 "hosts" not "host"
Table 1 It is vital to add the number of samples examined to this table. Listing positives only gives no indication of prevalence.  It would be extremely useful to show how many were symptomatic.
145 "in" not "if"
152  No need for "Indeed"
153  Do we really need HPD instead of "highest posterior density"?
162  Why do you consider stabilising selection (which is used in the general genetics literature to mean a disavantage to recombinant or out-of-range phenotypes)?  Why could it not just be that new recombinants are rare because they are novel?  Do you have citeable evidence for stabilising selection?  You imply in the next sentence that there is no barrier to generating new genotyes, possibly with new phenotypes.
169  I think you mean "little genetic polymorphism within the Mallorcan population" rather than " a slight differentiaotion from".
190, 193  Check journal policy on citing "unpublished" without a clue as to stage and place of publication, or even the full name of the first authors.  These are important and useful results, but without more detail as to where to follow up they are not really usable for future work.
200 "factor" or "factors2
196-200  This would bear a little more discussion, as geographic distance is almost irrelevant here since insect transmission is quite local.  Do the vectors fly over water?   I suspect infrequently.   So what matters is the extent of ornamental or commercial planting and it would be interesting to show visitor numbers or amounts of new building or establishments of almond orchards - you could refer forward to the information on loss of almond orchards
Fig 2.The legend refers to several outbreaks which no longer exist.  These nonetheless need to be shown somehow (?by small open circles or an initial letter).  Why is no establishment indicated in the balearics? The evidence presented earlier suggests the outbreaks are "established"
216 "exposes" not "expose"
222 "means" not "mean"
223-225  See earlier comment.  Some description of the economies of the islands and the links between them would be useful - perhaps a map?
235"evolved" rather than "derived"?
238 I think maybe "terrible" or "very severe" rather than "notorious" (=famous for a bad reason, which requires further evidence)
248 "has" not "have"
273 "raised" might be better than "important"
280  Fair enough to put this in, but a sentence explaining why this seems likely would be helpful
281-282  Is there any indication of the effect on yield?
284 "with respect to"
295 "justify" rather than "draw"
316-318.  This need to be established.  There is no necessary connection between vector numbers and vector transmission, especially if numbers are high because of abundant weed cover;  bare ground may encourage vectors to move further.  Your next sentence actually says this, but it is confusing to have asserted the influence of populations positively.
379-381.  Surely this only holds if the Q. ilex sampled were adjacent to orchards.  Was this true for the specific oak trees sampled?
Fig 5.  What are the little coloured squares in B?  In A, some detail of what the horizontal scale represents is needed - and a representation where line-length was proportional to phylogenetic distance (or even age) would be helpful.
416  What is the evidence for water-borne transmision?  No citation is given and it seems a bit surprising for such a specialised bacterium
423  "Planktonic" seems a surprising word to use of a comensual endophyte.  Is that conventional?
429-430 What is the implication  intended here?  Won't lower temperatures reduce vector movement and activity and phenology of the insects and hosts? Please explain.

 

 

Author Response

I think this is a very valuable review for all pathologists interested in pathogen invasions.   Most of my detailed comments are slight changes to the English, but some need a little change or addition to allow the reader to understand the data, or avoid ambiguity.

R: Thanks for your valuable comments. Please see our responses to each of your comments below

22 "disjunct" or "disjoint" not "disjunctive"

R: We have changed it to distant

23 "hold" not "concentrate"

R: Corrected

77-92  We need to be told what the criteria were for testing a plant and whether (for example) sampling was clustered in any way around evidently diseased plants.

R: Describe in detail how the sampling was performed with more than 13000 plants is quite difficult. We have tried to explain better the sampling strategy in this way:

Between November 2016 and December 2020, a total of 13,610 plant samples were analyzed at the Official Laboratory of Plant Health Service of the Balearic Islands (LOSVIB). Samples were received from three main sources: (i) official monitoring as a consequence of the application of the Commission Implementing Decision (EU) 2015/789 and Commission Implementing Regulation (EU) 2020/1201, applying random sampling to prospecting grids; (ii) within the context of several research projects (see funding projects); and (iii) from cooperatives, farmers and agricultural extension services. The first group of samples included symptomatic and asymptomatic plants, whereas the second and third group of samples were all symptomatic.

106-113 and generally.  Don't introduce unnecessary abbreviations  - the complicate reading considerably and in the electronic world we are not short of paper!  I don't think HKG is justified; I am doubtful about MLST and I'm not sure why you don't follow the conventional way of abbreviating species names, though I don't think that is a problem in reading.

We left MLST since it is referred several times in the text.

We have removed HKG abbreviation.

129 "hosts" not "host"

R: Changed

Table 1 It is vital to add the number of samples examined to this table. Listing positives only gives no indication of prevalence.  It would be extremely useful to show how many were symptomatic.

R: We have added the total number of simples analyzed. It is not possible to trace back how many of those were symptomatic.

145 "in" not "if"

R: corrected

152  No need for "Indeed"

R: Removed

153  Do we really need HPD instead of "highest posterior density"?

1. removed

162  Why do you consider stabilising selection (which is used in the general genetics literature to mean a disavantage to recombinant or out-of-range phenotypes)?  Why could it not just be that new recombinants are rare because they are novel?  Do you have citeable evidence for stabilising selection?  You imply in the next sentence that there is no barrier to generating new genotyes, possibly with new phenotypes.

R: thank you for the comments. We realize that the sentence was not clear. We have reworded it to clarify this:

Among the genomes of Majorcan Xf isolates, almost all the genetic recombination detected between the fastidiosa and multiplex subspecies precede their introduction onto the island [12]. This could suggest that the ancestral population had already undergone stabilizing selection, likely as an adaptation to the almond trees in California and thus it would be unlikely the emergence of new genotypes with different virulence or host ranges in Mallorca. However, we do see a notable risk of disruptive selection if the ST80 strain of subsp. pauca comes into contact with the other subspecies. New recombinants with unpredictable host ranges and virulence could be generated. ….

169  I think you mean "little genetic polymorphism within the Mallorcan population" rather than " a slight differentiation from".

R: We have rephrased it to clarify. Thanks for pointing this.

190, 193  Check journal policy on citing "unpublished" without a clue as to stage and place of publication, or even the full name of the first authors.  These are important and useful results, but without more detail as to where to follow up they are not really usable for future work.

R: We have included the authors performing the reserach cited. The manuscript is not published yet.

200 "factor" or "factors2
R: corrected

196-200  This would bear a little more discussion, as geographic distance is almost irrelevant here since insect transmission is quite local.  Do the vectors fly over water?   I suspect infrequently.   So what matters is the extent of ornamental or commercial planting and it would be interesting to show visitor numbers or amounts of new building or establishments of almond orchards - you could refer forward to the information on loss of almond orchards.

Reply: We agree with the reviewer. The sentence was not clear we have changed the sentence as follows:

Yet, surprisingly ST80 remains only known only in Ibiza. The distribution of Xf among the islands indicates a strong geographic barrier imposed by the sea, irrespective of the distance between islands. For example, the small island of Formentera only 3.6 km from Ibiza is still free of Xf, whereas the ST81 of subsp. multiplex was introduced into Menorca from Mallorca [15] which is 63 Km away. This points out that the likelihood of establishment of an introduction is an odd stochastic event conditioned by factors more related to human activity than natural dispersal. This agree with the known short-distance dispersal of P. spumarius.

Fig 2.The legend refers to several outbreaks which no longer exist.  These nonetheless need to be shown somehow (?by small open circles or an initial letter).  Why is no establishment indicated in the balearics? The evidence presented earlier suggests the outbreaks are "established"

Reply: We have modified the legend and the Figure.

216 "exposes" not "expose"
R: corrected

222 "means" not "mean"
R: corrected

223-225  See earlier comment.  Some description of the economies of the islands and the links between them would be useful - perhaps a map?
R. We think that te clarification made in te paragraph of above is enough.

235"evolved" rather than "derived"?
R: corrected

238 I think maybe "terrible" or "very severe" rather than "notorious" (=famous for a bad reason, which requires further evidence)
R: corrected

248 "has" not "have"
R: corrected

273 "raised" might be better than "important"
R: corrected

280  Fair enough to put this in, but a sentence explaining why this seems likely would be helpful.

Reply: included.

281-282  Is there any indication of the effect on yield?
R: Sorry we have no data on this.

284 "with respect to"
R: corrected

295 "justify" rather than "draw"
R: corrected

316-318.  This need to be established.  There is no necessary connection between vector numbers and vector transmission, especially if numbers are high because of abundant weed cover;  bare ground may encourage vectors to move further.  Your next sentence actually says this, but it is confusing to have asserted the influence of populations positively.

Reply: We agree with this comment. We have rephrased the text. 

379-381.  Surely this only holds if the Q. ilex sampled were adjacent to orchards.  Was this true for the specific oak trees sampled?

R: we have rephrased this. The Q. ilex were indeed adjacent in several locations.

Fig 5.  What are the little coloured squares in B?  In A, some detail of what the horizontal scale represents is needed - and a representation where line-length was proportional to phylogenetic distance (or even age) would be helpful.

Reply; We have modified the figure accordingly.

416  What is the evidence for water-borne transmision?  No citation is given and it seems a bit surprising for such a specialised bacterium

Reply: we realized the sentence was a little confusing. We have changed it.

423  "Planktonic" seems a surprising word to use of a comensual endophyte.  Is that conventional?

Reply: we include this term to emphasize the idea that drift with water movement. We now include ‘planktonic’.

429-430 What is the implication intended here?  Won't lower temperatures reduce vector movement and activity and phenology of the insects and hosts? Please explain.

Reply: We agree this sentence was not clear because was not finished and we have rephrased it.