Genetic Gains from Selection for Drought Tolerance during Three Breeding Periods in Extra-Early Maturing Maize Hybrids under Drought and Rainfed Environments
Round 1
Reviewer 1 Report
Dear Authors,
The manuscript captured valuable research with valuable findings. Writing on such an applied breeding topic is challenging. I have made some comments throughout the text. Please go through the comments, and address them. Reduce some text from result section, only narrate the most critical results pertinent to the objectives. In estimating heritability, you can consider variance due to genotype by environment interaction. You can consider shifting some Figures and Tables to the supplementary section.
I wish you good luck.
Comments for author File: 
Comments.pdf
Author Response
Reviewer 1
General minor revision comment 1:
Check for extra spaces in between words/phrases that are unnecessary throughout the manuscript.
Response:
All the extra spaces between words/phrases throughout the manuscript have been checked and corrected accordingly.
General minor revision comment 2:
Make sure to define all acronyms when first used in the manuscript text, including in the Figures and Tables.
Response:
All acronyms have been defined upon first mention in all aspects of the manuscript.
General minor revision comment 3:
Figure 3A, the list of the hybrids ID used in the study needs to be fixed as the spacing is off resulting to Line #35 missing.
Response:
The list of hybrid ID in Figure 3A has been revised to make all entry names including hybrid #35 visible.
Specific comments
Comment:
Pg. 1, line 26: remove – in “recom-mended”
Response:
“ – ” in recommended has been removed.
Comment:
Pg. 3, Line 112: I believe “onward match…” should be “onward march…”; needs to be confirmed.
Response:
Yes, it was a spelling mistake and that “onward match” has been corrected as “onward march” as suggested.
Comment:
Pg. 4, Line 161: fix the formatting of the phrase “…periods in the IITA-MIP from 2008 to 2010…” it has spacing issues and missing parenthesis, label period 1 so it will be consistent with the rest of the other periods.
Response:
The placement of parenthesis in line #161 has been corrected. “Period 1” has been included appropriately in consistence with the other periods.
Comment:
Pg. 8, Lines 281-283: suggest to show the actual formula of how to obtain genetic gain as it will be easier to visualize and compute for; similar to how heritability estimates was presented. This is also important as the genetic gain is one of the basis of this study
Response:
From this method, genetic gain per year is obtained by dividing the b value (linear regression coefficient) as the numerator by the intercept as the denominator and multiplied by 100. This relationship has been Illustrated as in the manuscript as follows;
gg yr-1 x 100
where gg yr-1 = genetic gain per year, and b value = linear regression coefficient.
Comment:
Pg. 9, Line 320-324: please revise the sentence “All measure traits…moisture was limited” as it is a confusing sentence.
Response:
The sentence is incomplete and has been deleted to avoid confusion. The idea meant in that sentence under well-watered condition has been indicated in line #334 of the manuscript.
Comment:
Pg. 9, Line 325: what does Grain yield under ons mean?
Response:
The sentence had typo error. This has been corrected as “Grain yield and other traits under well-watered conditions recorded repeatability estimates higher than 0.5 except for percent stalk lodging and ASI” in the manuscript.
Comment:
Pg. 17, Line 446-448: fix the sentence construction of the sentence “These results…genetic gains from selection” because it is confusing to the readers.
Response:
The sentence has been recast to improve clarity as follows;
“These results suggested that more environments are necessary to extensively evaluate a set of hybrids to accelerate genetic gains from selection”.
Comment:
Pg. 18, Line 473-476: suggest to reformat or split the first sentence of the paragraph because it is a compound sentence and is very confusing.
Response:
The sentence has been split into three sentences to improve clarity as indicated below;
Sentence 1: Grain yield of hybrids (period 1 to 3) under drought was regressed on the yields under rainfed conditions.
Sentence 2: The analysis revealed high grain yielding ability for the period 3 hybrids compared to those of periods 1 and 2.
Sentence 3: This elucidated the magnitude of progress made in the period 3 hybrids as far as high yield was concerned.
Reviewer 2 Report
Review Notes
General comments:
The authors were able to address their major objectives in this study. They presented results in a manner that a reader outside the scope of their scientific audience may be able to understand. Although their results might be considered to not be as novel outside the scope of their study, I believe it is important and novel in their target audience who are maize breeders developing new cultivars in Sub-Saharan Africa. Their results also have an impact in the farmers that are growing the maize that ultimately affects consumers.
The overall tone and grammar of the manuscript is acceptable, but there are parts that can still be improved. For example, editing compound sentences so it can be easily understood by readers.
Revisions:
General minor revision comment 1: Check for extra spaces in between words/phrases that are unnecessary throughout the manuscript.
General minor revision comment 2: Make sure to define all acronyms when first used in the manuscript text, including in the Figures and Tables.
General minor revision comment 3: Figure 3A, the list of the hybrids ID used in the study needs to be fixed as the spacing is off resulting to Line #35 missing.
Specific minor revisions
Pg. 1, Line 26: remove – in “recom-mended”.
Pg. 3, Line 112: I believe “onward match…” should be “onward march…”; needs to be confirmed.
Pg. 4, Line 161: fix the formatting of the phrase “…periods in the IITA-MIP from 2008 to 2010…” it has spacing issues and missing parenthesis, label period 1 so it will be consistent with the rest of the other periods.
Pg. 8, Lines 281-283: suggest to show the actual formula of how to obtain genetic gain as it will be easier to visualize and compute for; similar to how heritability estimates was presented. This is also important as the genetic gain is one of the basis of this study
Pg. 9, Line 320-324: please revise the sentence “All measure traits…moisture was limited” as it is a confusing sentence.
Pg. 9, Line 325: what does Grain yield under ons mean?
Pg. 17, Line 446-448: fix the sentence construction of the sentence “These results…genetic gains from selection” because it is confusing to the readers.
Pg. 18, Line 473-476: suggest to reformat or split the first sentence of the paragraph because it is a compound sentence and is very confusing.
Author Response
Reviewer 2
Comment:
Line #4; Should not have hyphen in between, please remove ‘ – ’
Response:
It was a typo error. Hyphen has been removed.
Comment:
Line #20; Remove hyphen from ‘linear’.
Response:
It was a typo error. Hyphen has been removed.
Comment:
Line #26: Remove hyphen from ‘recommended’
Response:
It was a typo error. Hyphen has been removed.
Comment:
Line #40; Insert ‘obtain’
Response:
‘obtain’ has been inserted
Comment:
Line #68; Excellent statement, please provide reference/s.
Response:
Reference, Badu-Apraku & Fakorede, 2017, has been included in the statement.
Comment:
Line #153; Is it sixty hybrids or subset of hybrids developed in certain periods?
Response:
Yes, they were sixty hybrids with subsets developed in the three breeding periods, 2008 – 2010, 2011 – 2013, and 2014 – 2016). This has been clarified in the sentence.
Comment:
Line #165; Too long Table for the main text, summarize the Table in the text, and put the Table in the supplementary section.
Response:
The content of the Table is very important in the manuscript and that putting it in a supplementary Table will not be appropriate. The Table should therefore be formatted to fit into the final version of the manuscript.
Comment:
Line #224; Clearly specify what is 10 and 6, is that row or col?
Response:
It is an incomplete block design with 10 entries in 6 blocks. This has been clarified in the text.
Comment:
Line #271; Use updated reference.
Response:
The latest version of SAS is SAS 9.4 which is found in SAS Institute 2012 release. It is therefore, appropriate to use this reference.
Comment:
Need some clarification here, mean of 60 hybrids or hybrids developed in a particular year to regress on years or regress on periods?
Response:
The means of the sixty hybrids developed in the three breeding periods were regressed on the periods (years within which the hybrids were developed). This has been clarified in the text.
Comment:
Line #286: keep H2 italic.
Response:
H2 has been italicized appropriately.
Comment:
Line 289; You can add GE term in the denominator as you have multi-environment data.
Response: The formular has been modified to reflect the genotype x environment (GE) factor as follows;
This has been included in the statistical analysis as suggested.
Comment:
Line #350; Table 3 can be in the supplementary section.
Response:
Table 3 is very relevant in the main text and should therefore be maintained.
Comment:
Line #352; Please make it self-explanatory, you can elabore WW, DS in the footnote well- watered or drought stress or so.
Response:
Footnotes have been included in Table 4 to explain WW and DS as well-watered and drought stress respectively, R2 = coefficient of determination, a = intercept, and b = linear regression coefficient.
Comment:
Line #356; ha-1 please put it as superscript
Response:
ha-1 has been modified as superscript accordingly.
Comment:
Line #407; Make Table 5 self-explanatory; what the top diagonal and bottom diagonal values referring in the Table?
Response:
Top and bottom diagonal values are referring to the correlation coefficients among the traits. The asterisks (* or **) are indicating significance at 0.05 or 0.01 probability levels. This clarification has been included in the Table.
Comment:
Line #436; Detailed discussion.
Response:
Comment appreciated by authors.
Comment:
Line 552; Nice conclusion.
Response:
Comment appreciated by authors.
