Combining Ability and Heterosis of Algerian Saharan Maize Populations (Zea mays L.) for Tolerance to No-Nitrogen Fertilization and Drought

Round 1

Reviewer 1 Report

accept

Reviewer 2 Report

The paper has improved significantly and it is ready now for publication

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

The response of plants to low nitrogen and drought and the investigation for improving drought tolerance is a matter of intense ongoing discussion. Therefore, the studies related to the response of plants to nutrient and water stress in relation to their tolerance are an essential contribution. The manuscript reports field trials carried out to evaluate the response of Algerian maize populations to low nitrogen and drought stress. However, there are certain points that make it difficult to assess the validity of the hypothesis and presented data.

In abstract, the authors should provide more information about the methods followed to test the objectives of this study. For instance, they should give information about N levels and the stage at which drought stress was applied (were the plants exposed to less water from sowing?). Moreover, they should define abbreviations such as AOR and IGS at first mention.

In my opinion, it is not appropriate to mention no N application as low N treatment. Though, the N levels are low (110 ppm) in soil but it would have been more appropriate to test a maid range N treatment such as 60 kg/ha.

The main concern is that the reported results are based on speculations with no concrete evidence or data is provided related to the physiological or biochemical basis of better or worst performance of maize populations under low N and drought stress. 

I understand that the observed differences are significant but it feels that the results are speculated without any data associated with the observed differences,  

Tables 1-3 could be given as supplementary material.

I would suggest presenting the meteorological data in a figure. 

Reviewer 2 Report

This paper presents a work within a reseach line of maize breeding for local conditions. The stress component of the study is very interesting, as well as the genetic materials used. However, the  presentation is very confusing and it needs work to make the manuscript understandable. The abstract section is very well written, and the introduction is more or less correct, as well as the material and methods section. However, the results presented are too detailed and the discussion section only states similar or dissimilar results obtained by other authors, or previous results from the same authors.

The authors include early vigor, plant height, anthesis-silking interval (ASI) and yield in the studies. While all these variables are relevant and usually accounted for, they gave the same importance to all of them. The result is that yield results are not as visible as they should be, inside all the explanations about secondary traits. Early vigor, plant height and ASI should be used to explain variations in yield, instead of considering them as parallel variables with the same importance.

The results section is very difficult to follow, with all the concepts and variables mixed-up, and with very detailed explanation of all the numbers of very long tables. In my opinion Tables 4, 5 and 6 are too long, and they should be included as supplementary materials. Instead, abbreviated tables with the most important data about yield should be kept in the central part of the manuscript.

Minor aspects to be improved:

• Analysis of variance (Table 2 and 3): the table head should express what are the values in the table. Are they mean squares? F values? At the end of the table there is "df" and "MS" (a single value per variable) that should also be defined.
• As the experiment is a split-split-plot, the errors used in the analysis of variance to test the effect of water, nitrogen and cross should be specified in material and methods.
• From the reading I understood that the experiments were performed in a single location during two years. However, the authors use the expression "environment" in results and discussion section, which is not defined. I think that using "year", and "treatment" to define the water and nitrogen availability would be much better. The use of "environment" expression adds more confusion than clarification in this context.
• In line 85 "crossed in a diallel without" should be "crossed in a diallel mating design without"
• The expression "well water" should be changed by "well watered"
• In line 218 there is a sentence with the same meaning than the one in line 219. The first one should be eliminated.

In general, the experiment is interesting, the execution seems correct to me, but the results presentation and the discussion section need more work. The tables presented are fine as an exploratory analysis of every result, but they should be used as a previous step to prepare tables for a manuscript. The authors need to make a list of the most important results they want to explain, and prioritize the main results over the secondary ones. An extensive rewritting of results and discussion should be undergone before the manuscript is ok.