Towards a Sustainable Agriculture: Strategies Involving Phytoprotectants against Salt Stress

Round 1

Reviewer 1 Report

Acosta-Motos et al., 2019 is a review article focused on Phytoprotectants, their mechanism of action in alleviating salt stress and their effect on crop yield and quality. In this review Phytoprotectants have been divided into categories based on microbial origin, nitrogen containing, antioxidative metabolism and plant hormones related and each category has been discussed in detail with examples. Overall, existing knowledge on phytoprotectants for salt stress has been provided by the authors.  

Morphogenetic and other growth effects due to high accumulation of phytoprotectants either due to exogenic applications or expression of transgenes is not discussed well for each category.  Although this review is about salt tolerance, what are some of the negative effects due to these phytoprotectants also have to be discussed in this context. For example, are there any negative effects on plant growth due to high accumulation of melatonin in plants beside salt tolerance??

 

Line# 41: Abbreviations: Include dS m^-1 (deciSeimens per meter)

Line#150, 181, 192: Sentences need correction

Line#190: What are the antogonistic compounds? Mention some of the soluble and volatile compounds that these bacteria produce by giving examples.

Line#234: What genes in specific here? SOS1? transgenic plants expressing NhaA and ProBA from the bacteria mentioned? Please clarify. Expand the specific gene examples:  NhaA, Na+/H+ antiporter gene and ProBA, Proline biosynthesis gene - give references

 

A table summarizing the phytoprotectant, mode of action, dosage, physiological effects in terms of salt stress as well as other effects - positive/ negative side effects could be helpful for the readers.

 

This manuscript requires revision for grammatical errors in English and multiple comments have been indicated in the attached pdf document to correct some of such errors.

Comments for author File: Comments.pdf

Author Response

REVIEWER 1

“Acosta-Motos et al., 2019 is a review article focused on Phytoprotectants, their mechanism of action in alleviating salt stress and their effect on crop yield and quality. In this review, phytoprotectants have been divided into categories based on microbial origin, nitrogen containing, antioxidative metabolism and plant hormones related and each category has been discussed in detail with examples. Overall, existing knowledge on phytoprotectants for salt stress has been provided by the authors.

Morphogenetic and other growth effects due to high accumulation of phytoprotectants either due to exogenic applications or expression of transgenes is not discussed well for each category.  Although this review is about salt tolerance, what are some of the negative effects due to these phytoprotectants also have to be discussed in this context. For example, are there any negative effects on plant growth due to high accumulation of melatonin in plants beside salt tolerance??”

 

Authors: We thank Reviewer 1 for the overall evaluation provided. The focus of the review was to give an overview on the beneficial roles of different phytoprotectans in improving the resistance of plants to saline stress. In order to avoid an excessive extension of the manuscript, the given information regarding negative effects of phytoprotectants is scarce. In this sense, in general, the application of phytoprotectants to the concentrations reported in the literature as alleviators of salt stress has positive effects on plant growth. However, in a few cases, negative effects have been reported, as for the role of SA in the response of pea plants to NaCl stress [ref 275] and for melatonin promoting leaf Cl^- in the absence of NaCl-stress. Moreover, in response to the Reviewer 1, examples of negative effects have been included for proline in tomato [155] and rice [154,156] subjected to salt stress (lines 292-298). On the other hand, negative effects on melatonin under different abiotic stresses (out of the scope of this review) can be also found; for example, under Cu toxicity conditions, low melatonin concentrations (10 µM) improved germination and seedling growth, whereas higher levels (100 µM) had adverse effects in both processes (Posmyk et al. J. Pineal Res. 2008, 45, 24–31).

In addition, a comprehensive Table 1 showing the literature collected in this review concerning exogenous application of phytoprotectants has been included at the end of the manuscript. In this Table, numerous phenotype effects in response to phytoprotectants applications are showed, as well as application mode, dose and main physiological processes affected.

 

Reviewer 1. “Line# 41: Abbreviations: Include dS m^-1 (deciSeimens per meter)”

 

Authors: dS; deciSiemens abbreviation has been included in the abbreviations section. Authors have not added “m^-1” because is a widely used and known measure in the scientific world.

 

Reviewer 1. “Line#150, 181, 192: Sentences need correction”

Authors:

All sentences have been improved and added to the manuscript as follows:

 

Lines 162-164: “In addition to high levels of Na⁺ and Cl^-, and depending on its source and treatment, reclaimed wastewater may contain high levels of beneficial elements such as P, K+, Ca²⁺ and Mg²⁺, which can alter AMF function”

Lines 189-20: These sentences been rewritten.

Lines 212-214: “On the other hand, the direct growth promotion occurs by increased nutrient availability (by nitrogen fixing or solubilization of P and K+, among other nutrients), altered phytohormone and enzymatic production [97-99] and modulated osmotic balance [100,101].”

 

Reviewer 1. Line#190: “What are the antogonistic compounds? Mention some of the soluble and volatile compounds that these bacteria produce by giving examples.”

 

Authors: We thank the Reviewer for the observation provided. In response to this, the following text has been introduced:

Lines 209-212: “This may include the production of antibiotics [86,87], lysing enzymes as proteases, cellulases, glucanases, chitinases, lactonases [88-90], siderophores to chelate iron [91,92] or other toxic compounds as cyanide [93,94], as well as volatiles compounds such as dimethyl disulfide and 2-methylpentanoate [95,96]. ”

 

Reviewer 1. Line#234: “What genes in specific here? SOS1? transgenic plants expressing NhaA and ProBA from the bacteria mentioned? Please clarify. Expand the specific gene examples:  NhaA, Na+/H+ antiporter gene and ProBA, Proline biosynthesis gene - give references”

 

Authors: In response to the reviewer, the paragraph has been extended, and new references included, as follows:

Lines 254-261: “Regarding the molecular aspects of PGPR action, the expression of novel plant genes such as SOS1, which codifies for a plasma membrane Na+/H+ antiporter [138], was found to be promoted in PGPR-applied wheat shoots and roots, resulting in improved salt stress resistance [139]. Moreover, the use of genes from halo-tolerant PGPR may confer salt tolerance to transgenic plants; for example, expression of Bacillus subtilis proline biosynthesis (ProBA) gene conferred salt tolerance in transgenic Arabidopsis through increased proline production [140]. Likewise, halotolerant properties of PGPR such as Enterobacter ludwigii and other enterobacters rely on the role of Na+/H+ antiporters such as NhaA.”

 

Reviewer 1. “A table summarizing the phytoprotectant, mode of action, dosage, physiological effects in terms of salt stress as well as other effects - positive/ negative side effects could be helpful for the readers.”

 

Authors: Following the recommendations of the Reviewer 1, and as indicated above, such (extense) table has been added dealing with the different types of phytoprotectans studied, agent / treatment applied, the plant species used and the positive effects that these phytoprotectans produce on plants. As stated above, little attention has been given to the negative effects of phytoprotectants. However, specific few examples are found along the main text.

 

Reviewer 1. “This manuscript requires revision for grammatical errors in English and multiple comments have been indicated in the attached pdf document to correct some of such errors.”

 

Authors: We thank the Reviewer 1 for their improvements in language and for the typos found, and indicate that all suggestions and comments marked on the PDF have been conducted Overall, and together with changes suggested by the other two reviewers, a substantial number of paragraphs and phrases has been rewritten. In general, special care has been taken regarding grammar to avoid mistakes.

Reviewer 2 Report

In the Review, the Authors present a possibility of using various phytoprotectans in ensuring salinity tolerance. Since the part of the title involves "agriculture" term all references should include the agricultural plants. For this reason, I suggest eliminating, for instance references related to Salix sp., Betula sp. and some ornamental and rare plants.  I would leave the halophyte only since they are the masters of salinity accommodation and adaptation. In the Introduction briefly explain to the reader the classification of plants according to salinity tolerance. Say that most crops are glycophytes but between them, the differences also exist. Give the examples of most tolerant crops and sensitive.

In spite of the interesting title, in my opinion, the Abstract is not attractive and persuasive enough. I suggest to the Authors to be more precise and to avoid the generalization. Figure 1 is well presented and describes the topic. However, there are some parts of the Review that are really hard to follow. For instance, the beginning of the Introduction is confusing.

The special comments are pointed out in the text.

Comments for author File: Comments.pdf

Author Response

REVIEWER 2

“In the Review, the Authors present a possibility of using various phytoprotectans in ensuring salinity tolerance. Since the part of the title involves "agriculture" term all references should include the agricultural plants. For this reason, I suggest eliminating, for instance references related to Salix sp., Betula sp. and some ornamental and rare plants.  I would leave the halophyte only since they are the masters of salinity accommodation and adaptation.”

 

Authors: We thank the Reviewer for the comment and fully agree that the manuscript is focused on agricultural plants. The references to Salix sp. and Betula sp. have been removed. However, we consider appropriate to leave the references to some ornamental plants which, despite of their null interest in agriculture, contribute to have a more comprehensive knowledge on the use and effects of the different phytoprotectants. On the other hand, in the Table 1 included at the end of the review in response to another Reviewer, only species of agronomic interest are included.

.

Reviewer 2. “In the Introduction briefly explain to the reader the classification of plants according to salinity tolerance. Say that most crops are glycophytes but between them, the differences also exist. Give the examples of most tolerant crops and sensitive.”

 

Authors: Following the recommendations of the Reviewer 2, a brief classification of the plants according to their resistance to salinity and with specific examples of each group has been included as follows:

Lines 68-78: “Halophytes (1% of the world’s flora) are plants able to survive and reproduce in saline environments of 200 mM NaCl or more. Relevant examples include Salicornia sp, Alterniflora Spartina, Anemopsis californica and Atriplex sp., among others. Facultative halophytes occur on slightly saline soils, and include many species of Poaceae, Cyperaceae, Juncaceae; Glaux maritima, Plantago maritima, Aster tripolium and Chenopodium quinoa. The major group of plants are glycophytes or halophobic, which represent 98–99 % of the world’s flora. Within them, the vast majority are non-resistance to salt and and therefore unable to successfully grow in saline soils. However, a small number of glycophytes (facultative glycophytes or indifferent to salt) may develop some resistance to salt and show higher levels of sodium in their tissues. As representative examples of this latter group there are ecotypes of Festuca rubra, Agrostis stolonifera, Phragmites communis, species or subsoecies of Puccinellia, Lotus, Atriplex hastata, Vigna unguiculata and sugar beet [14,15].”

 

Reviewer 2. “In spite of the interesting title, in my opinion, the Abstract is not attractive and persuasive enough. I suggest to the Authors to be more precise and to avoid the generalization. “

 

Authors: Abstract has been modified to make it more engaging and concrete about the Review content.

 

Reviewer 2. “Figure 1 is well presented and describes the topic.”

 

Authors: We thank the reviewer for the evaluation provided. In addition, as stated above, a comprehensive Table showing the literature collected in this Review concerning exogenous application of phytoprotectants to plants of agronomic interest has been included.

 

Reviewer 2. “However, there are some parts of the Review that are really hard to follow. For instance, the beginning of the Introduction is confusing.

 

Authors: The authors would like to thank the Reviewer 2 for their comments to the Introduction section and consider that they served to improve the section. As highlighted in yellow in the Manuscript file, substantial changes have been introduced.

 

Reviewer 2. “The special comments are pointed out in the text.”

Authors: We thank the Reviewer for the suggestions provided. All changes have been conducted (and highlighted in yellow), with the exception of the comment regarding abbreviations in the main text. In this case, the instructions indicated by the journal in the author's guideline were used as criteria, where it reads that “Abbreviations should be defined in parentheses the first time they appear in the abstract, main text, and in figure or table captions and used consistently thereafter.”

 

Reviewer 3 Report

This review paper contains plenty of information on different phytoprotectents and how they alleviate salt stress; however, those facts are widely available as research and review papers. One unique section listed as ‘applicability’ in figure 1 was interesting and relatively novel, but information on that section was lacking in the review paper. Although the importance of content presides over sentence structure, poor sentence structure in this paper hinders understanding of the provided information. Words are misused, there are numerous spelling errors and content is not organized.

When writing a review paper on such topic the authors should list the effect and explain mechanism that produce those effects in a clear way or vice versa i.e., explain the mechanism and then the consequences of those mechanism on plants. Here in this paper, although information are available, they not organized. For e.g. ‘More comprehensive knowledge related to PGPR and plant interaction in different agro-ecosystems is required in order to get major benefices in agricultural exploitations’ on line 212 feels like author is ending topic on PGPR but then in next paragraph start same topic again.

 

31

You have stated ‘However, the information about the molecular mechanisms involved on mode of action of phytoprotectants is scarce’ this is untrue; there are plenty of research and review papers on the topic. Even your references include numerous such papers. Please change or remove the sentence.

 

However, review on using phytoprotectants to alleviate salt stress primarily by explaining dose selection, time of application, crop types, crop growth stage, economics, or production process is scarce. It would be very informative if you review focused on those topics.

 

54

‘subjected exposed’ written at once, you should either go with subjected or exposed

 

56

What type of consequences? And why reality, was it not considered reality? Worldwide is written incorrectly. Please consider rewriting ‘The FAO stressed in a recent report that climate change impacts on agriculture and the consequences for food security are a reality worlwide’

 

59

Remove ‘tend to’

Enhance is a positive word replace it with word like ‘cause’

What does ‘that’ mean? Is it Salinization? State in the sentence

 

61

‘On one hand, reclaimed wastewater supplies an important amount of beneficial nutrients, which can improve soil fertility. However, this type of water can result in serious problems associated to salinity and high boron concentrations’ poor sentence structure please rewrite sentence. What kind of wastewater or does all wastewater increase soil salinity and boron concentration?

Also, this sentence should be supported by research on multiple crops not just on lemon.

 

65

Changing ‘ca.’ to approximately may be reader friendly

 

66

Why is world scale used with link and out of format?

 

67

‘causing generating’ same comment as line 54

 

71

What physiological processes? State

 

74

What physiological and biochemical mechanisms?

In the introduction section. Explain all the physiological and biochemical processes cause by salinity that you will be addressing in the below sections.

In the respective phytoprotectants sections, focus on how those processes are modified by phytoprotectants to alleviate salt stress

 

86

Why are some world written in different font size and embedded link (such mycorrhizal)? Please provide reason.

Change ‘for’ to ‘which increases’ or something similar.

 

89

Crops plants includes all plants, rewrite the sentences.

 

96

What kind of toxic effect?

 

99

‘According to the literature concerning mycorrhizal application, physiological, biochemical, and molecular studies show that AMF help to reduce the negative impact of salinity.’ Poor sentence structure.

 

140

Remove ‘shrub’

 

145

‘produced’ doesn’t make sense select different work or change sentences.

 

149

‘reclaimed wastewater’ As your review focuses on sustainability and the use of wastewater define what kind of waste water (municipal or agricultural or something else)?

 

150

‘use to content’ is unclear.

 

151

[50] is not proper list author name (e.g. Abc et. al., (2012) reported that …… ), follow same rule for all others

 

153

‘to  the same’ remove unnecessary space after to

 

156

Correct appliying to applying.

 

162

‘At the molecular level, the elucidation of the mechanisms implicated in AMF symbiosis under salt stress has advanced over the past decade’ Just for my understanding can you list some advancement in molecular level that you have listed in manuscript those were not known on past decade?

 

163

Why ‘overall’ consider removing it.

 

167

‘The current trend towards the use of biological products, such as mycorrhizal inoculation, is helping to increase the efficiency of intensive agriculture. Nowadays, the combination of AMF inoculation and controlled deficit irrigation in drought or salinity conditions are increasingly applied in arid and semi-arid areas’. These sentences need citation.

 

172 to 174

What kind of competition may occur? list some

How may AMF work under different soil conditions?

How should the use of AMF be modified depending type and duration of stress?

These facts will be valuable to anyone willing to use AMF.

 

174

Add space ‘present in’

 

174

You state ‘the biochemical and molecular basis of most of described effects remain unknown.’ And previously you had stated ‘molecular mechanisms implicated in AMF symbiosis under salt stress has advanced’ is it not contradicting. Your review in this section need to be clear on what is known and what are unknown.

 

184

Change ‘refer’ to referred

 

189

Improper use of semicolon. Either describe both effect on one single sentence or change semicolon to full stop.

 

190 to 195

Very unclear need to rewrite.

 

199

‘As a consequence’ is not proper change the sentence.

 

200

How is use of PGPR reducing use of pesticide and chemical fertilizer? Explain and cite.

 

228

When using PGPR to alleviate salt stress, what are important considerations? Like what dose, application time, application duration, crop type and others? List those in this section.

Also, list considerations for using other phytoprotectants in other sections as well.

 

254

Same comment as line 151

 

302

‘under salt stress’ written twice remove one. Change ‘relation’ to comparison.

 

321

Just saying ‘have demonstrated its role in seed germination, plant growth, organogenesis, and leaf and fruit senescence.’ is not sufficient. Explain how melatonin achieved that.

 

322

Add citation and change ‘It also acts enhancing’ change to ‘it also enhance’

 

327

Remove ‘from tryptophan’

 

440

You report ‘Salicylic acid (SA) is a phenolic plant hormone widely distributed in plants, playing an important role in the regulation of different physiological processes such as seed germination, vegetative growth, photosynthesis, respiration, thermogenesis, flower formation, fruit yield, seed production and senescence’ based on reference 226. When I went through the reference I did not find what you reported can you specify the paragraph/s where I can find those information? 

 

445

‘In general, SA-treated plants showed lower NaCl-induced symptoms and higher growth rate, chlorophyll contents, and photosynthetic capacity, as well as enhanced antioxidant capacity in relation to non-treated plants.’ What plants? Citations? If you are making an statement based on what you researched or read you should write show instead of showed. If it is showed then you should report where or who showed.

 

625

Why is the font change done?

Author Response

REVIEWER 3

Principio del formulario

This review paper contains plenty of information on different phytoprotectents and how they alleviate salt stress; however, those facts are widely available as research and review papers. One unique section listed as ‘applicability’ in figure 1 was interesting and relatively novel, but information on that section was lacking in the review paper.

 

Authors: We thank the Reviewer for the evaluation provided. We are aware of the existing number of reviews dealing with phytoprotectants against abiotic stress. However, we do consider that un updated Review regarding the effect of different phytoprotectants in response to salt stress is pertinent. Some other works focus on a specific type of phytoprotectants, whereas herein we attempt to present an overview of the field. In this overview, we present an innovative Figure 1 in which common aspects of phytoprotectants mode of action are presented. Moreover, as in other fields, knowledge on phytoprotectants is advancing quickly. In this regard, over 60% of references included in this Review correspond to studies from the last decade (2010-19), out of which over 40 publications correspond to the last two years. In addition, to make more useful and relevant the manuscript in connection with the “applicability” mentioned by the Reviewer, a comprehensive Table has been included, in which the information collected in this review concerning exogenous application of phytoprotectants to plants of agronomic interest has been listed. Herein, the application and dose and beneficial effect in plants in terms of phenotype and physiological changes, which can be helpful for researcher in different fields.

 

Reviewer 3. “Although the importance of content presides over sentence structure, poor sentence structure in this paper hinders understanding of the provided information. Words are misused, there are numerous spelling errors and content is not organized. When writing a review paper on such topic the authors should list the effect and explain mechanism that produce those effects in a clear way or vice versa i.e., explain the mechanism and then the consequences of those mechanism on plants. Here in this paper, although information are available, they not organized. For e.g. ‘More comprehensive knowledge related to PGPR and plant interaction in different agro-ecosystems is required in order to get major benefices in agricultural exploitations’ on line 212 feels like author is ending topic on PGPR but then in next paragraph start same topic again.”

 

Authors: We thank the Reviewer for noticing those mistakes and lack of consistency. After a substantial rewriting of part of the manuscript (including reorganization of some paragraphs) and careful revision, we do thin that the Review is significantly improved. Main changes to the manuscript are highlighted in yellow in the file.

 

Reviewer 3. 31. “You have stated ‘However, the information about the molecular mechanisms involved on mode of action of phytoprotectants is scarce’ this is untrue; there are plenty of research and review papers on the topic. Even your references include numerous such papers. Please change or remove the sentence.”

 

Authors: The sentence has been removed. As the Reviewer indicates, there are numerous reports on that topic, the references for which are indeed reflected in the Review.

 

Reviewer 3. “However, review on using phytoprotectants to alleviate salt stress primarily by explaining dose selection, time of application, crop types, crop growth stage, economics, or production process is scarce. It would be very informative if you review focused on those topics.”

 

Authors: We appreciate these observations by the Reviewer. In this regard, the Table 1 was included as stated above, where agent, plant species and growth stage, application form and dose are specified where relevant. In fact, since such information is relevant, we wanted to highlight them in Figure 1.

 

Reviewer 3. “54 ‘subjected exposed’ written at once, you should either go with subjected or exposed”

 

Authors: In response to the Reviewer’s comment, this point has been corrected.

 

Reviewer 3. “56 What type of consequences? And why reality, was it not considered reality? Worldwide is written incorrectly. Please consider rewriting ‘The FAO stressed in a recent report that climate change impacts on agriculture and the consequences for food security are a reality worlwide’”

 

Authors: As the Reviewer suggested, the sentence has been rewritten as follows:

Lines 54-55: “In a recent report, the FAO highlighted the necessity of strategies towards the impacts of climate change on agriculture and food security worldwide [2]”.

 

Reviewer 3. “59 Remove ‘tend to’. Enhance is a positive word replace it with word like ‘cause’. What does ‘that’ mean? Is it Salinization? State in the sentence”

 

Authors: The minor changes have been conducted.

 

Reviewer 3 “61 On one hand, reclaimed wastewater supplies an important amount of beneficial nutrients, which can improve soil fertility. However, this type of water can result in serious problems associated to salinity and high boron concentrations’ poor sentence structure please rewrite sentence. What kind of wastewater or does all wastewater increase soil salinity and boron concentration?

Also, this sentence should be supported by research on multiple crops not just on lemon.”

 

Authors: The sentence has been rewritten and extended, the type of water has been specified and seven new references have been added.

 

Reviewer 3. “65 Changing ‘ca.’ to approximately may be reader friendly”

 

Authors: Change has been done.

 

Reviewer 3. “66 Why is world scale used with link and out of format?

 

Authors: We have no explanation for this minor mistake, but it has been corrected.

 

Reviewer 3. “67 ‘causing generating’ same comment as line 54”

 

Authors: We thank the Reviewer one more time for the detected typos. It has been amended.

 

Reviewer 3. “71 What physiological processes? State”

 

Authors: As the Reviewer suggested, the physiological processes have been included as follows:

Lines 82-84: “…as a lower energy production through photophosphorilization and phosphorylation in the respiratory chain, and an affected assimilation of nitrogen and protein synthesis,…”

 

Reviewer 3. “74 What physiological and biochemical mechanisms? In the introduction section. Explain all the physiological and biochemical processes cause by salinity that you will be addressing in the below sections. In the respective phytoprotectants sections, focus on how those processes are modified by phytoprotectants to alleviate salt stress”

 

Authors: These physiological and biochemical processes are specified in the Introduction section.

 

Reviewer 3. “86 Why are some world written in different font size and embedded link (such mycorrhizal)? Please provide reason.”

 

Authors: As stated above, we do not find a reason for this particular problem with the format.

 

Reviewer 3. “Change ‘for’ to ‘which increases’ or something similar.

 

Authors: In response to the Reviewer, this has been corrected.

 

Reviewer 3. “89 Crops plants includes all plants, rewrite the sentences.”

 

Authors: In response to the Reviewer, the sentences have been rewritten.

 

Reviewer 3. “96 What kind of toxic effect?”

 

Authors: In response to the reviewer, the phrase has been changed to include “…specific ion toxicity”.

 

Reviewer 3. “99 ‘According to the literature concerning mycorrhizal application, physiological, biochemical, and molecular studies show that AMF help to reduce the negative impact of salinity.’ Poor sentence structure.”

 

Authors: The phrase has been deleted, since it results redundant with a sentence placed immediately before.

Reviewer 3. “140 Remove ‘shrub’”

 

Authors: In response to the Reviewer, the word shrub has been removed.

 

Reviewer 3. “145 ‘produced’ doesn’t make sense select different work or change sentences.”

 

Authors:  Sentence has been changed according to Reviewer’s comment.

.

Reviewer 3. “149 ‘reclaimed wastewater’ As your review focuses on sustainability and the use of wastewater define what kind of waste water (municipal or agricultural or something else)?”

 

Authors: The type of reclaimed wastewater used is municipal wastewater. It has been added.

 

Reviewer 3. “150 ‘use to content’ is unclear.

 

Authors: The whole sentence from lines 161 to 163 has been rewritten for a better understanding.

 

Reviewer 3. “151 [50] is not proper list author name (e.g. Abc et. al., (2012) reported that …… ), follow same rule for all others

 

Authors: The correct reference format has been introduced where the comment applies.

 

Reviewer 3. “153 ‘to  the same’ remove unnecessary space after to”… “156 Correct appliying to applying.”

 

 Authors: Typos corrected.

 

162

Reviewer 3. “162 ‘At the molecular level, the elucidation of the mechanisms implicated in AMF symbiosis under salt stress has advanced over the past decade’ Just for my understanding can you list some advancement in molecular level that you have listed in manuscript those were not known on past decade?

 

Authors: This review has not focused on studies at the molecular level but they have been more numerous in the last decade. Some related to membrane-level transport have been included in the text as follows:

“Recent studies revealed the molecular mechanisms of high K+:Na+ ratio in mycorrhizal plants, which are based on induced expression of genes involved in K+ acquisition and Na+ extrusion to the soil [62-64]. For example, in Oryza sativa, up-regulation of OsNHX3 (sodium/hydrogen exchanger) by AMF allow the compartmentalization of Na+ into the vacuole [63]. In black locust, AMF induced the expression of genes encoding for membrane transport proteins and aquaporins (SOS1, HKT1, NHX1, and SKOR), which contribute maintaining ion homeostasis [64]”

 

Other examples of advances not included in the Review are:

 

- An improvement of gas exchange in AMF plants have been explained recently by the regulation of glycine betaine, among others. This osmlolyte stabilizes PSII pigment-protein complexes as well as protect Rubisco and rubisco activase, which are responsible for fixing CO₂ (Talaat and Shawky, 2014; Borde et al, 2017; Xu et al 2018).

- There is evidence that AMF colonization also influences the concentration and profile of organic acids and polyamines in plants (Sheng et al., 2011; Evelin et al., 2013; Talaat and Shawky, 2013), which are related with certain nutrient availability and retention of ion homeostasis.

-Improved nitrate uptake in plants has been also attributed to the maintenance of membrane stability and the increase of Nitrate Reductase activity by AMF (Talaat and Shawky, 2014).

 

Reviewer 3. “163 Why ‘overall’ consider removing it.

 

Authors:  In response to the Reviewer’s comment, the word has been removed.

 

Reviewer 3. “167 ‘The current trend towards the use of biological products, such as mycorrhizal inoculation, is helping to increase the efficiency of intensive agriculture. Nowadays, the combination of AMF inoculation and controlled deficit irrigation in drought or salinity conditions are increasingly applied in arid and semi-arid areas’. These sentences need citation.”

 

Authors: In response to the Reviewer’s comment, (five) new references have been included.

 

Reviewer 3. “172 to 174 What kind of competition may occur? list some. How may AMF work under different soil conditions? How should the use of AMF be modified depending type and duration of stress? These facts will be valuable to anyone willing to use AMF.”

 

Authors: The paragraph has been subjected to extensive changes addressing the questions proposed.

 

Reviewer 3. “174 Add space ‘present in’”

 

Authors:  In response to the Reviewer’s comment, the space has been added.

 

Reviewer 3. “174 You state ‘the biochemical and molecular basis of most of described effects remain unknown.’ And previously you had stated ‘molecular mechanisms implicated in AMF symbiosis under salt stress has advanced’ is it not contradicting. Your review in this section need to be clear on what is known and what are unknown.”

 

Authors: Several molecular and biochemical mechanisms have been partially or totally understood in the recent years, but there is still much more to explain. In response to the Reviewer’s comment, the sentence has been rewritten. Some aspects that should be addressed in the future at molecular level have been added.

 

Reviewer 3. “184 Change ‘refer’ to referred”

 

Authors: In response to the Reviewer’s comment, the change has been made.

 

189

Reviewer 3. “189 Improper use of semicolon. Either describe both effect on one single sentence or change semicolon to full stop.”

 

Authors: In response to the reviewer’s comment, a full stop has been introduced.

 

190 to 195

Reviewer 3. “190 to 195 Very unclear need to rewrite.”

 

Authors: In response to the Reviewer’s comment, it has been rewritten as follows:

“The indirect stimulation of plant growth occurs by competing against plant pathogen, by means of antagonistic compounds produced by the PGPR or by induced resistance to pathogens in the plants [80,81,82-85] .This may include the production of antibiotics [86,87], lysing enzymes as proteases, cellulases, glucanases, chitinases, lactonases [88-90], siderophores to chelate iron [91,92] or other toxic compounds as cyanide [93,94], as well as volatiles compounds such as dimethyl disulfide and 2-methylpentanoate [95,96]. On the other hand, the direct growth promotion occurs by increased nutrient availability (by nitrogen fixing or solubilization of P and K+, among other nutrients), altered phytohormone and enzymatic production [97-99] and modulated osmotic balance [100,101].”

 

Reviewer 3. “199 ‘As a consequence’ is not proper change the sentence.”

 

Authors: As the Reviewer suggested, it has been for “In agreement with….”.

 

200

Reviewer 3. “200 How is use of PGPR reducing use of pesticide and chemical fertilizer? Explain and cite.”

 

Authors: As the Reviewer suggested, the following lines have been added to the manuscript:

“Likewise, PGPR have also been applied to reduce the use of chemical fertilizers and pesticides, as a consequence of the more efficient nutrient uptake and the plant protection conferred by PGPR [108,109]. This results in improved economic viability, soil fertility, and environmental sustainability [110-112].”

 

Reviewer 3. “228 When using PGPR to alleviate salt stress, what are important considerations? Like what dose, application time, application duration, crop type and others? List those in this section.

Also, list considerations for using other phytoprotectants in other sections as well.”

 

Authors: In the Table 1 mentioned above, these aspects have been considered. In addition, the following lines have been introduced in the PGPR section:

Line 248: “In the last decades, a large number of studies have demonstrated beneficial PGPR effects in both laboratory and greenhouse studies. However, fewer studies conducted field trials, and more comprehensive knowledge related to PGPR and plant interaction in different agro-ecosystems is required The beneficial effects of PGPR are modulated by diverse growth habitats, native microbial communities and environmental conditions. For example, weather fluctuations influence the effectiveness of PGPR [137], which has to be considered in field experiments and in PGPR applications in agriculture”.

 

Reviewer 3. “254 Same comment as line 151”

 

Authors: The correction has been done.

 

Reviewer 3. “302 ‘under salt stress’ written twice remove one. Change ‘relation’ to comparison.

 

Authors: The minor changes have been done.

 

Reviewer 3. “321 Just saying ‘have demonstrated its role in seed germination, plant growth, organogenesis, and leaf and fruit senescence.’ is not sufficient. Explain how melatonin achieved that.”

 

Authors: In response to the Reviewer’s comment, the following lines have been introduced:

“All these functions might be mediated by the effect of melatonin up-regulated genes related to a multitude of cellular functions, including primary metabolism, redox processes, lipid and carbohydrate metabolism, cell cycle, DNA replication, photosynthesis, and senescence-associated genes, among others [204,205]. “

 

Reviewer 3. “322 Add citation and change ‘It also acts enhancing’ change to ‘it also enhance’”

 

Authors: Both changes have been made.

 

Reviewer 3. “327 Remove ‘from tryptophan’”

 

Authors:  In response to the Reviewer’s comments, “from tryptophan” has been removed.

 

Reviewer 3. “440 You report ‘Salicylic acid (SA) is a phenolic plant hormone widely distributed in plants, playing an important role in the regulation of different physiological processes such as seed germination, vegetative growth, photosynthesis, respiration, thermogenesis, flower formation, fruit yield, seed production and senescence’ based on reference 226. When I went through the reference I did not find what you reported can you specify the paragraph/s where I can find that information?”

 

Authors: We are very sorry for this mistake. In this case, we had confusion with the bibliographic reference for this paragraph. The correct reference to which we wanted to refer the information in the cited paragraph is now ref 275.

 

Reviewer 3. “445 ‘In general, SA-treated plants showed lower NaCl-induced symptoms and higher growth rate, chlorophyll contents, and photosynthetic capacity, as well as enhanced antioxidant capacity in relation to non-treated plants.’ What plants? Citations? If you are making an statement based on what you researched or read you should write show instead of showed. If it is showed then you should report where or who showed.

 

Authors: We are again sorry for our mistake by not including the appropriate references. In this case, the corresponding references were in the Reference list, but not in the main text (references 276-284).

 

Reviewer 3. “625 Why is the font change done?”

 

Authors: We do not know why, but the mistake is corrected.

 

Round 2

Reviewer 3 Report

Line 72 change ‘Poaceae, Cyperaceae, Juncaceae; Glaux maritima, Plantago maritima, Aster tripolium and Chenopodium quinoa’ to ‘Poaceae, Cyperaceae, Juncaceae families such as Glaux maritima, Plantago maritima, Aster tripolium and Chenopodium quinoa.’

Line 102 change ‘vegetable species’ to plants.

Line 107 Remove ‘|’

Line 193 change salinity to saline

Line 194 change ‘other species’ to ‘compared to other AMF’.

Line 199 you have incorrect citation type here-correct it.

Line 216 and line 280 have different citation styles, follow journal guidelines for both and check the manuscript for other similar errors.

 

I could not find table 1, only figure 1 was added as a supplemental file. Please provide table 1 for review