Soil Type and Zinc Doses in Agronomic Biofortification of Lettuce Genotypes

Round 1

Reviewer 1 Report

The manuscript quality improved with the introduced changes. However, I still feel that the results presented are of little meaning considering the amount of data already published on this particular topic.

Author Response

Dear Reviewer:

We appreciate the contributions done, certainly will help to improve our work. The modifications were made and the manuscript was checked by a native English editing service.

Best regards.

Reviewer 2 Report

Review comments for the manuscript titled “Soil type and zinc doses in agronomic biofortification of lettuce genotypes”

1. The paper presents an interesting topic to address the genotypes- soil types interaction for assessment of Zn agronomic biofortification in lettuce cultivation. The topic is suitable for the journal “Agronomy”. I think the findings in this study have something new; however, the authors did not give enough information to support lettuce is a potential candidate to be as a Zn biofortified crop for the populations of developing countries. Give more information about the populations who are closely related to the low dietary Zn intakes should daily consume how many lettuces to improve Zn nutrition. I suggest the authors should strengthen the motivation for the selection of the three types of lettuce.

2. The details about fertilization levels and Zn treatments were shown by using a concentration unit mg dm-3. This would mislead the readers. Please change to use the unit as mg/kg soil. Additionally, one-pot contains 5 dm-3 soil. Please change it by ? kg soil.

3. Figure 1 shows the reduction trends of dry weight by an increase of Zn application rate higher than 15 mg/L. Simultaneously, in Fig. 2 the plant Zn concentrations are about 40 mg/kg. According to the ref. [19], the lettuce growing with 10 mg/kg could accumulate Zn in plant up to 185 mg/kg without reduction of growth. Why? Please add more discussion in the revision.

4. The description from lines 219-225 for the results is not clear and not easy to understand. Please give some background about RDA in the section of “Introduction” to strengthen the motivation.

5. line 113: Change line to type “3. Results”.

6. line 232: Change line to type “5. Conclusions”.

Author Response

Dear Reviewer:

We appreciate the contributions done to improve our work. The modifications suggested were attended and the manuscript was checked by a native English editing service. Concerning to the unit used in our work (mg dm-3), the Figures 1 and 2 were modified according to requested.

Best regards.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

I think this study is solid study with good design that would benefit from more detail and more context.

Introduction

The first paragraph contain many assertions that need citations to back them up. It is misdiagnosing the actual causes of food insecurity, as well as making sweeping generalisations about the motivations behind agricultural development. It also is not needed to move forward the central thesis that human zinc deficiencies are a problem.

Line 37 needs a citation and more detail than "problems". Citations 6 and 7 are being misused by the authors. Zinc deficiency is primarily attributed to poor diets - which can be argued is a result of poverty. furthermore, reference 6 is from a study with wheat, while this is a study with lettuce.

Line 46:  Is "It ..." referring to agronomic biofortification? Lines 47 - 48 could use more information on under what conditions fertilizer increased plant Zn concentrations. The sentence on lines 49-51 is overly vague, but perhaps not needed at all. It is already widely documented that Zn is an important micronutrient to plants. However, you have not demonstrated what levels are considered deficient, what is an optimum range to see fertilizer response or what Zn levels are reasonable to expect from lettuce.  Lettuce is not considered an ideal crop to relieve zinc deficiencies, so I'm unclear why there is a focus on biofortifying zinc content in lettuce.

Why were the experimental levels chosen (the lettuce cultivars, soil types and the Zn fertilizer levels)?

Materials and methods

The term "CWa" needs more context - what is this classification from and what does it mean?

Where was the soil collected from? (also, where is the Federal University of Lavras located?). What was the size of the sieve? What was the pH of the soil after liming?

How big were the pots?

I can't evaluate references 16 and 17 since they appear to be in Portuguese. I don't know what the journal policy regarding non-English references, but there are English language methods for soil analytical procedures.

You probably specify that NIST is a U.S. agency. What standard reference materials were used? Were there technical reps for the extraction and AAS analysis? Can you provide more information regarding the quality control protocols?

The statistical methods could use more details - an equation of the model would work, or a very explicit statement of how each independent variable is treated (fixed or random, linear, polynomial) and what interactions were included. Also, what analytical software was used?

I strongly recommend against the use of custom acronyms ("SDA", "QA") - it's often unneeded (QA is not used again) and it is confusing for the reader.

Results

line 116: "ratify" and "differentiated" are odd word choices in the context they are being used

Figure 3: image is low resolution, so it is difficult fully discern what
is going on

Discussion

This section should be used to (1) explain results, (2) compare study results to other previous research in the area subject matter, and (3) relate the results to the ideas laid out in the introduction. The first purpose was met. The second and third were not.

line 127: should clarify it is lettuce genotypes

line 155-156: this sentence does not make sense

A scientifically convincing argument regarding the contribution of Zn biofortified lettuce to Zn uptake was asserted, but not supported with numerical evidence.

Lines 173-175 Wordy and difficult to understand. This also contains odd word choices for the context, such as "determinant".

Overall, we really don't know anything about Zn bioavailability in this plant or how this might contribute to lettuce yields. The study documented a change in single plant biomass in an artificial environment. Many studies have demonstrated that a controlled greenhouse study is not predictive of crop field performance.

Reviewer 2 Report

General comment:

The present work (agronomy-616857) evaluates the influence of Zn fertilization on Zn content and biomass production of three lettuce genotypes grown in two different soils. In general, the manuscript is well written. The problem is that this work is not novel at all. There are several papers on this subject and the obtained results were in good agreement with what is already known – the soil and the genotype have a major influence in the accumulation of minerals in plants. Therefore, I don’t think this work meets the technical and scientific criteria of Agronomy.

Specific Comments:

(L.60) This is the first time the acronym RYL is written. Add the full name.

(L.61-62) See my previous comment. Add the full name of SDM and dRL

(L.70) “…there was a constant decrease with Zn applications”. For both? If yes, say it clearly in the text

(L.72) “quadratic increases”? What does this really mean? Replace this by a simpler language so that everyone can understand.  

(L.78) See my previous comment. Replace this by another expression.

(L.79) What is the opposite of a "quadratic increase"? Change this so that one can easily understand what the authors are trying to say.

(L.81) Include between parentheses the genotype to which the authors are referring to.  

(L.71) See my previous comments on this “quadratic increase”

(L.97) Add the mean Zn concentration of grand rapids leaves between parentheses. In addition, is this difference statistically significant?

(L.98) Add the mean Zn concentration of delicia leaves between parentheses

(L.101) Add "respectively".

(L.129) Remove “RYL”

(L.138) I have many doubts about this statement. Plants do know what they absorb and how much. There is a great body of literature that explains the mechanisms involved in minerals uptake and translocation, including the details on the different metal transporters. Based on this, how can this statement be true?

(L.141) “As the shoots of lettuce are consumed…” Confusing sentence. Rewrite this.  

(L.149) Rewrite this. The name of the author must be written where reference 18 is placed.

(L.170) How were these values calculated? Explain

 (L.173) This information is known for many years. This has no novelty.  

(L.182) Is higher than 22 ºC? This is very imprecise. Replace this by mean values or a range.

(L.189) Isn't this "mineralogical analysis" something that can be included in the group of "chemical and physical soil analysis", that is written in the same sentence?

(L.214) Remove “biofortification”

(L.215) “tubers”? Correct this

(L.216) provide the model of the used equipment

 (L.217) Which SRMs were used? The authors must add this information.

 (L.224-227) This paragraph should be in another subsection entitled "Statistical analysis". Change accordingly