Assessment of Genetic Diversity of Bread Wheat Genotypes for Drought Tolerance Using Canopy Reflectance-Based Phenotyping and SSR Marker-Based Genotyping

Round 1

Reviewer 1 Report

The authors propose a manuscript titled “Assessment of Genetic Diversity of Bread Wheat Genotypes for Drought Tolerance Using Canopy Reflectance-Based Phenotyping And SSR Marker-Based Genotyping”

The article is original, well structured and written. In particular, this study takes into consideration on genetic diversity of bread wheat genotypes using canopy reflectance-based vegetation indices (VIs) and simple sequence repeat (SSR)-maker based genotyping for drought-tolerance. Fifty-six wheat genotypes were assessed using phenotypic traits (combination of VIs and yield traits) and thirty SSR markers Data of phenotypic traits were averaged over two growing seasons under irrigated and drought-stressed field conditions. Also phenotypic traits based hierarchical clustering of wheat genotypes unveiled three clusters differing in tolerance to drought. Finally, wheat genotypes from all phenotypic clusters were distributed throughout all SSR-based clusters, indicating that genetically heterogeneous genotypes were allocated to different drought-tolerant groups. The aim of the study is based genotyping might be an effective technique to assess genetic diversity to improve drought tolerance of bread wheat genotypes. Very interesting data and approch that I share  which I would summarize as "a return to the past with a modern approach".

I read the work carefully in a critical way, and suggested in detail some concepts only in order to further improve the good work done. In particular, some concepts need to be referenced, indicating point by point where is necessary.

1. Introduction

Well done, the concept are correct but in some case need to complete with literature data because they are not a study result or authors considerations.

·        Lines 51-56. “The introduction of new wheat genotypes with greater yield potential and enhanced drought tolerance is the most acceptable strategy for improving wheat production [choose reference]. Drought-tolerant genotypes are often chosen for economic features based on the presence of genetic variation in the genetic pool [choose reference]. Genetic diversity facilitates the identification of tolerant genotypes as parental lines in the breeding programs to develop superior progenies for selection [5], without excluding starting from species of the genus Aegilops L., the wild ancestor of cultivated wheat [Perrino et al. 2014];

·        Lines 59-61. There are several phenotypic tools for measuring genetic diversity; among them, crop ideotypes, phenology, and yield attributes are extensively used because of their reliability in measuring genetic variation within a gene pool [choose reference];

·        Line 60. Ideotypes? What means? Maybe ecotypes. Please clarify

·        Line 61. ….in measuring genetic variation within a gene pool. True, is the concept of Harlan and de Wet 1971? If yes please consider this work in the text an also in the reference

 

References to be added:

ü Perrino, E.V.; Wagensommer, R.P.; Medagli, P. The genus Aegilops L. (Poaceae) in Italy: taxonomy, geographical distribution, ecology, vulnerability and conservation. Systematics and Biodiversity 12 (3): 331-349. Doi: 10.1080/14772000.2014.909543

 

2. Materials and Methods

In general well done, the figure 1 and the table are clear.

·        Line 118. The field laboratory of Bangabandhu Sheikh Mujibur Rahman Agricultural University have the comnparable environmental conditions to the fields in nature? if yes, please clarify better this point.

 

3. Results and 4. Discussion

Well done, the text and the figures are clear. No suggestions.

 

5. Conclusions

·        Please spend two more words on future research in the field

 

References

·        Please give DOI when is available

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

A total of 56 wheat genotypes were used to investigate canopy reflectance-based vegetation indices over two growing seasons under irrigated and drought-stressed field conditions and genotyped using 30 simple sequence repeat markers. This article reported some interesting results. However, it should be improved before acceptance. Comments are listed as follows:

1. A total of 30 SSR markers were used for genotyping 56 wheat. Five did not produce any bands, so only 25 were used for further analysis. These 25 markers were located on 18 of 21 chromosomes, indicating only 1-2 markers each. More markers should be used for wheat, a large genome (~14.5-Gb) species. For each chromosome, it should be more than ten polymorphic SSR markers. Or a higher number of markers should be used, such as single nucleotide polymorphisms, diversity array technology, et al. Besides, markers should be filtered based on missing data, heterozygosis rate, and minor allele frequency.

2. This study used 56 wheat genotypes for drought tolerance using canopy reflectance-based phenotyping. However, which genotypes were the most tolerant to drought? I suggested it should be evaluated using the comprehensive evaluation method of weight.

3. In the section “Association among phenotypic traits”, the relationship between phenotypic traits was determined. Phenotype data were collected in two water conditions, but the results showed only one result without any explanation?

4. Population structure should analyze K=3 when Delta K of K=3 was also close to K=7. The population structure and cluster analysis both used allelic data. The results should be compared and explained.

Line 149, Figure S1 didn’t present？

Line 233, no ‘*’ was in the figure; it should be removed from the figure legend.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper investigated the genetic diversity of bread wheat genotypes using a combined strategy of reflectance-based indirect phenotyping with SSR based genotyping for drought-tolerance. The results are interesting and would contribute to assess genetic diversity for drought tolerance improvement in bread wheat. After reviewing this paper, I think the paper could be accepted by the Journal 'sustainability' after revisions. There are some suggestions or questions as below:

1: Did the previous studies use the crop canopy for genotyping? If yes, please indicate the effectiveness. If not, please explain more on why you choose this the crop canopy for genotyping in bread wheat.

2: Please introduce the background of the materials used in the paper, why you used those materials, are they representative？Because the phenotyping results highly depend on the research materials.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 4 Report

Revision of the --Manuscript Draft-- Manuscript Number: sustainability-1770452

Title: Assessment of genetic diversity of bread wheat genotypes for drought tolerance using canopy reflectance-based phenotyping and SSR marker-based genotyping

Type: Article

This is a manuscript within the scope of the journal "Sustainability (ISSN 2071-1050) ". It is relevant as study suggesting that combining reflectance-based indirect phenotyping with SSR-based genotyping might be an effective technique to assess genetic diversity to improve drought tolerance of bread wheat genotypes.

The manuscript is presented in a well-structured manner. However, the Abstract should be about 200 words maximum. The actual ms has 275 words.

From my point of view, the content succinctly described and contextualized with respect to previous and present theoretical background and applied research on the topic. However, in the Introduction section the authors do not mention all references relevant to the research. In the LNs 98-100 is mentioned the use of high-throughput-origin indirect phenotypic data along with the SSR markers to explore wheat genetic diversity is scanty. I suggest adding at least the papers:

Moraga, F.; Alcaíno, M.; Matus, I.; Castillo, D.; del Pozo, A. Leaf and Canopy Traits Associated with Stay-Green Expression Are Closely Related to Yield Components of Wheat Genotypes with Contrasting Tolerance to Water Stress. Plants 2022, 11, 292. https://doi.org/10.3390/plants11030292

Pandey, A.; Khobra, R.; Mamrutha, H.M.; Wadhwa, Z.; Krishnappa, G.; Singh, G.; Singh, G.P. Elucidating the Drought Responsiveness in Wheat Genotypes. Sustainability 2022, 14, 3957. https://doi.org/10.3390/su14073957

The research design, questions, hypotheses and methods are clearly stated. Moreover, the arguments and discussion of findings are coherent, balanced and compelling.

I suggest the authors for improving the ms to take care with the not appropriate use of Abbreviations for the whole document. LNs 105, 115, 127, 128, 177, 219, 220, 225-227, 229, 230, 269, 271-274, 281, 283, 285, 333, 345, 346, 348, 350, 352, 371, 411, 420-422.

The conclusions is thoroughly supported by the results presented in the ms.

The ms is not adequately referenced. See LNs 188, 203, 315, 354, 398, 455, 472. Moreover, according to Reference List and Citations Style Guide for MDPI Journals: For documents co-authored by a large number of persons (more than 10 authors), you can either cite all authors, or cite the first ten authors, then add a semicolon and add ‘et al.’ at the end.

I suggest the authors to write DOI numbers (Digital Object Identifier) because they are not mandatory but highly encouraged.

More aspects are mentioned in the revised document.

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Accept！

Author Response

We are really grateful to you for your comments and suggestions to improve the manuscript, and to get the present version that is publishable in the journal Sustainability. Many thanks for endorsing the manuscript for publication in the journal.

Reviewer 4 Report

Dear Authors,

I accurately revised the new version of your manuscript entitled: Assessment of genetic diversity of bread wheat genotypes for drought tolerance using canopy reflectance-based phenotyping and SSR marker-based genotyping.

I believe it has been sufficiently improved to warrant publication in Sustainability (ISSN 2071-1050).

However, it needs to be accepted after minor revision because:

. In Figure 6, LN 320, it is confusing for me. In the first version of the manuscript the authors mentioned Nei et al. (1983). In the actual Reference list it belongs to number [44].

. I suggest the authors replace the items in LNs 363-365.

. In LN 397, it is confusing for the readers. Does it refer to Nei et al. (1983)? I suggest the authors briefly explain this aspect in the body text.

. In Figure 8, LN 410, it is confusing again for me. In the first version of the manuscript the authors mentioned Nei et al. (1983). In the actual Reference list it belongs to number [44].

That's all for the moment.

With regards

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.pdf