Potential Bioinoculants for Sustainable Agriculture Prospected from Ferruginous Caves of the Iron Quadrangle/Brazil

Round 1

Reviewer 1 Report

This seems to be well-conducted research and to have clear, repeatable results.  The scientific content contributes to the space in which it develops. The work was provided with a sufficient level of scientific novelty. The abstract must include a key message which authors wish to convey to the audience or a statement which they argue.
Introduction:  The hypothesis part has some limits. How exactly do authors recommend their results? Include the missing information (research gaps and the significance of your research comparing with similar research groups). Why it is required to run just such research, what are the alternatives? 
The introduction provides a good understanding of the subject and its importance, with a significant quantity of information. Theoretical and practical reasons for the experiments are very reasonable.

The authors carried out a systematic investigation aimed to prospect new potential bio-inoculants from ferruginous caves of the Brazilian Iron Quadrangle. Bacteria from seven caves and one can soil sample were evaluated for the bio-controller activity of the phytopathogens.  Bacterial isolates were active in nitrogen fixation, solubilization of phosphate, in production of hydrolytic enzymes and have been acted simultaneously as biocontrollers and PGPBs. They could be important candidates for future investigations in crop science and in the search for sustainable agriculture. The analytical work of the authors is perfect, very well illustrated.

I have no critical comments. Paper is complex and innovative. The structure of the paper is logical and the results are well reproduced. The introduction and discussion are well organized. The results reported have not been published elsewhere. Conclusions are presented in an appropriate fashion and are supported by the data.

The idea that Cs-Se NPs can be considered as a potential plant-growth-promoting and stress protecting agent with new outlooks for
applying in the agricultural sector is innovative. 

Chances of improvement are still there.  I suggest read/use the following papers to improve discussion:DOI: 10.1042/BCJ20190606; 
doi: 10.3390/microorganisms8081237;  https://doi.org/10.3390/foods9121780; doi: 10.1016/j.aaspro.2015.08.085; doi:https://doi.org/10.1111/1751-7915.13290; DOI: 10.1080/713851125;  DOI: 10.1007/s00114-005-0060-3; DOI: 10.1016/j.resmic.2008.10.002
The manuscript can be useful for future applied research. 
I think the overall concept is interesting and potentially important. I recommend to ACCEPT the paper for publication with minor revision.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

The study search for potential bioinoculants from ferruginous caves of the Brazilian Iron Quadrangle. This is an interesting work, where culturable bacteria were screened to determine their potential as biocontrollers and PGPBs. The topic is of interest and highly relevant, it is well written and clearly presented. My only concern is regarding the methods applied to evaluate phosphorus solubilization and nitrogen fixation, since these methods give only presumptive results. The use of tricalcium phosphate as a sole source to evaluate the presence of phosphate solubilizing bacteria is a methodological mistake (see Biology and Fertility of Soils 2013, 49: 465-479). In the literature of in vitro screening, it is common to use triphosphate calcium as the substrate, although it has very little to do with reality because strains capable of degrading it are not necessarily phosphate solubilizers that promote plant growth. To establish the capacity of phosphorus solubilization by a strain, a test with a harder-to-dissolve compound, such as Fe-P or Al-P is needed. On the other hand, N fixation should be verified by an analytical method such as acetylene reduction. If it is not possible to explore these methods, at least a clarification regarding the limitations of the methods applied should be included in the discussion.

Other minor comments:

 

Line 563: change diatrophic to diazotrophic

 

Lines 568-570: According to the statement in lines 564-568 just three of the evaluated activities gave positive results for the bacterial isolates, please replace four by three in the sentence.

 

Line 585: Which hypothesis? No hypothesis has been raised in the manuscript. The statement must be reworded to clarify.

The reference list must be edited, making sure that all Latin names are in italics.

 

Author Response

Please see the attachment

Author Response File: Author Response.docx