Genetic Potential of New Maize Inbred Lines in Single-Cross Hybrid Combinations under Low-Nitrogen Stress and Optimal Conditions

Round 1

Reviewer 1 Report

Congratulations to the authors for the manuscript. Reading was enjoyable and it sparked my interest. Below are some suggestions to the authors.

1 - The meaning of the acronym GEI in line 72 is missing (Genotype-environment interaction)

2 - Question? -> The heterotic groups are based on what?  What is the origin of the new inbred lines? This information is important.

3 - In models (1) and (2) -> Remove the underlines and edit the indices to be subscripted.

4 - I don't know the output of GenStat software, only ASReml also from VSNi. Were the means, SCA and GCA estimated via restricted maximum likelihood?

5 -  Table 6 -> The unit of measurement is missing; use the same code for lines and crosses i.e. "P2 x P1" instead "2 x 1", and "G1" instead "1".

6 - Line 201 -> The best three specific combiners for grain yield (GY) performance under optimal management conditions were genotypes: G12 and G11. (You have to include G35 or replace for two)

7 - Lines 206 to 208 -> Repeated information.

8 - The Figure 1 would be more friendly to the readers if the environments (low and optimal N) were differentiated by color or letter. 

9 - My suggestion is: Remove the Figure 2 and improve the Figure 1 (with detail of each N level). On the other hand, if you are looking to relate performance in low and high N (only two columns), I suggest graphs with two axes (High N and Low N), with quadrants defined by the environment average, separating responsive, non-responsive, efficient and inefficient (these are ideas, not requirements on my part).

All the best!

Author Response

1 - The meaning of the acronym GEI in line 72 is missing (Genotype-environment interaction)

-The meaning of the acronym GEI ‘Genotype-environment interaction’ added

2 - Question? -> The heterotic groups are based on what?  What is the origin of the new inbred lines? This information is important.

-Information on heterotic groups was added under section 2.1 in the materials and methods

3 - In models (1) and (2) -> Remove the underlines and edit the indices to be subscripted.

-The requested changes were effected

4 - I don't know the output of GenStat software, only ASReml also from VSNi. Were the means, SCA and GCA estimated via restricted maximum likelihood?

- SCA and GCA were estimated following the  Griffing’s [15], Method 4, Model 1 analysis procedures in the CIMMYT AGD-R 4.0 software.  

5 -  Table 6 -> The unit of measurement is missing; use the same code for lines and crosses i.e. "P2 x P1" instead "2 x 1", and "G1" instead "1".

-corrections suggested effected

6 - Line 201 -> The best three specific combiners for grain yield (GY) performance under optimal management conditions were genotypes: G12 and G11. (You have to include G35 or replace for two)

-G35 included as suggested by the reviewer

7 - Lines 206 to 208 -> Repeated information.

-Repeated information was deleted

8 - The Figure 1 would be more friendly to the readers if the environments (low and optimal N) were differentiated by color or letter.

-While we appreciate suggestions by the reviewer, unfortunately the Genstat software in-which we created the figure, does not allow us to differentiate the colors.

9 - My suggestion is: Remove the Figure 2 and improve the Figure 1 (with detail of each N level). On the other hand, if you are looking to relate performance in low and high N (only two columns), I suggest graphs with two axes (High N and Low N), with quadrants defined by the environment average, separating responsive, non-responsive, efficient and inefficient (these are ideas, not requirements on my part).

-We appreciate the suggestion by the reviewer, but Figure 1 and 2 are serving two different purposes. In Figure 1, the target is to identify genotypes stables across all the eight locations used in the study, whereas in Figure 2, the target is to identify genotypes specifically adapted either under optimal conditions or low nitrogen environments.

Reviewer 2 Report

1. It will be perfect if the relevant literatures of the last three years are provided.

2. In the "2.3. Management" of "2. Materials and Methods" , it is necessary to describe the low nitrogen stress and optimum conditions in detail. 

3. In the Table 5, I only see the data of one year, and the author needs to explain the reason.

4. Table 6 provides only one year's data, and lack of units of the grain yield. 

5. Please review English and check the structure of format presentation for Agronomy.

Author Response

Reviewer 1

1 - The meaning of the acronym GEI in line 72 is missing (Genotype-environment interaction)

-The meaning of the acronym GEI ‘Genotype-environment interaction’ added

2 - Question? -> The heterotic groups are based on what?  What is the origin of the new inbred lines? This information is important.

-Information on heterotic groups was added under section 2.1 in the materials and methods

3 - In models (1) and (2) -> Remove the underlines and edit the indices to be subscripted.

-The requested changes were effected

4 - I don't know the output of GenStat software, only ASReml also from VSNi. Were the means, SCA and GCA estimated via restricted maximum likelihood?

- SCA and GCA were estimated following the  Griffing’s [15], Method 4, Model 1 analysis procedures in the CIMMYT AGD-R 4.0 software.  

5 -  Table 6 -> The unit of measurement is missing; use the same code for lines and crosses i.e. "P2 x P1" instead "2 x 1", and "G1" instead "1".

-corrections suggested effected

6 - Line 201 -> The best three specific combiners for grain yield (GY) performance under optimal management conditions were genotypes: G12 and G11. (You have to include G35 or replace for two)

-G35 included as suggested by the reviewer

7 - Lines 206 to 208 -> Repeated information.

-Repeated information was deleted

8 - The Figure 1 would be more friendly to the readers if the environments (low and optimal N) were differentiated by color or letter.

-While we appreciate suggestions by the reviewer, unfortunately the Genstat software in-which we created the figure, does not allow us to differentiate the colors.

9 - My suggestion is: Remove the Figure 2 and improve the Figure 1 (with detail of each N level). On the other hand, if you are looking to relate performance in low and high N (only two columns), I suggest graphs with two axes (High N and Low N), with quadrants defined by the environment average, separating responsive, non-responsive, efficient and inefficient (these are ideas, not requirements on my part).

-We appreciate the suggestion by the reviewer, but Figure 1 and 2 are serving two different purposes. In Figure 1, the target is to identify genotypes stables across all the eight locations used in the study, whereas in Figure 2, the target is to identify genotypes specifically adapted either under optimal conditions or low nitrogen environments.

Reviewer 2

1. It will be perfect if the relevant literatures of the last three years are provided.

-we appreciate the comment by the reviewer. We tried to the best of our abilities to include most of the references that we saw to be relevant in this study.

2. In the "2.3. Management" of "2. Materials and Methods" , it is necessary to describe the low nitrogen stress and optimum conditions in detail.

-we have to the best of abilities, added flesh under section 2.3 as suggested by the reviewer.

3. In the Table 5, I only see the data of one year, and the author needs to explain the reason.

-the study fell within the CIMMYT stage 3 maize trials, were the selected few lines tested in this study were advanced to stage 4, the regional trials, now across many locations in southern Africa. Already, inbred lines used in this study were previously tested in stage 1 and 2 trials. This study was key to make key selections of inbred lines that will be advanced to stage 4 trials.

4. Table 6 provides only one year's data, and lack of units of the grain yield.

-the study fell within the CIMMYT stage 3 maize trials, were the selected few lines tested in this study were advanced to stage 4, the regional trials, now across many locations in southern Africa. Already, inbred lines used in this study were previously tested in stage 1 and 2 trials.

-We have added units of measurement as suggested by the reviewer.

5. Please review English and check the structure of format presentation for Agronomy.

-We have reviewed English and adjusted the format of the manuscript as per Agronomy requirements.