Integrating Heterosis for Root Architecture and Nitrogen Use Efficiency of Maize: A Comparison between Hybrids from Different Decades

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The research aims to compare heterotic effects for root architecture in the representatives of the old era (released before 1990s) and new era (released after 1990s) maize hybrids, and to estimate a relation between heterosis root traits with that for nitrogen use efficiency. The materials of the study included four model hybrids (two representatives of the old era breeding and two from the new era breeding), and their parental lines. The genotypes studied were used in experiments to identify changes in manifestation of economically valuable traits during heterotic hybrid breeding in maize.

In the experiments performed using a modified ‘Shovelomics’ method (Trachsel et al., 2011) under conditions with contrast nitrogen contents in the soil (0 and 150 kg N ha^-1), the parameters of individual components of root architecture structure were determined. The result of experiments indicated a steeper-denser-deeper dynamics of root architecture in the new era hybrids that enhanced pre-anthesis N uptake, positively affected post-anthesis N remobilization. With using the adequate statistical approaches, the impact of heterotic components (nitrogen internal efficiency, root architecture, nitrogen recovery) in to the heterosis for nitrogen use efficiency was determined for each group of genotypes, and the stronger heterosis for root architecture in the new era hybrids was proved.

The manuscript is appropriately structured, contains all required sections. The text is illustrated with 7 Figures and 5 Tables. The title corresponds to the content of the proposed article. 

Comments: 

Introduction: 

-                      A brief description of maize root system is necessary to better understand the details of phenotypic analysis of the root architecture.

-                      A brief review of the analogous published studies (heterosis for root architecture, heterosis for nitrogen utilization efficiency, comparison of old era and new era heterotic hybrids) performed on other crops would be useful.                

Materials and methods: 

-                      The methods are described fairly comprehensively. I only have some notes concerning the material examined (see below).

-                      As stated on the lines 109-112, “Taking the year of 2000 as the boundary, old era typical maize hybrids Zhongdan 2 (ZD2) and Danyu 13 (DY13) and new era typical maize hybrids Zhengdan 958 (ZD958) and Xianyu 335 (XY335) and their parental inbred lines with extension area of more than 111 5 million acre were selected as test materials (Table 1)”. However, as follows from the Table 1 (“Details of old and new era maize hybrids and parental inbred lines”), Zhengdan 958 was released in 1996. Please specify the years of release of the materials studied: the dates vary in different sources for Zhengdan 958 (1996 in the present study, 2000 in: T. Wang et al., Crop Science 2011). The same is for Xianyu 335.

-                      One of the parents for the old era hybrids is Mo17 whereas both parents for Zhengdan 958 and Xianyu 335 are diverse. Could that influence the parameters estimated for example, AH and MPH?

-                      It would be important to specify the CMS-Rf system used in producing the hybrids?

-                      Please indicate how many plants of each genotype have been studied in each experimental variant. 

Results: 

-                      I have no principal notes on the quality of the material presented. However, I recommend to expand and detail legends to the Figures 1-4, and 6. I also recommend careful text editing.

 

Discussion:

-                      The discussion is quite satisfactory. Again, the examples of other crop species (if exist) would be desirable.

-                      The Table 6 (referenced on the line 355) is absent in the text.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Evaluation of the manuscript – agronomy- 3128070-peer-review-v1

Integrating Heterosis for Root Architecture and Nitrogen Use Efficiency of Maize: A Comparison between Hybrids from Different Decade

Yuanyuan Li ^1,2,†, Lanfang Bai ^1,†, Shuli Wei ¹, Hao Wu ¹, Rongfa Li ¹, Yongqiang Wang ¹ and Zhigang Wang ^1,*

 

¹ College of Agronomy, Inner Mongolia Agricultural University, Hohhot 010019, Inner Mongolia, China; [email protected] (Y.L.); [email protected] (L.B.); [email protected] (S.W.); [email protected] (H.W.); [email protected] (R.L.); [email protected] (Y.W.); [email protected] (Z.W.)

² College of Grassland Science, Inner Mongolia Minzu University, Tongliao 028000, Inner Mongolia, China; [email protected] (Y.L.)

^* Correspondence: [email protected] (Z.W.)

^† Contributed equally to this work and are co-first authors.

 

I am sorry, for some inaccuracies, but I believed that the data was correctly collected and calculated with the help of calculation programs by the authors. Also, there were some lapses in methodology verification, so I revised the paper and will make some additions as per your suggestions to the manuscript – agronomy- 3128070-peer-review-v1: Integrating Heterosis for Root Architecture and Nitrogen Use Efficiency of Maize: A Comparison between Hybrids from Different Decade

1.What is the main question addressed by the research?

As we mentioned in the submitted assessment, the research carried out by the authors aims at improving heterosis in maize, so that the obtained maize hybrids show, compared to the parental lines, a high heterosis in the F1 generation in terms of the involvement of the root system in a better absorption of fertilizers. In this sense, a study was carried out on the architecture of the root system and experimental data were obtained that led to significant correlations between the way the root system develops on the soil profile and the nutrient assimilation capacity.

2. What parts do you consider original or relevant for the field? What specific gap in the field does the paper address?

The scientific novelty consists in research on the relationship that exists between the architecture of the root system and the efficiency of nitrogen use, the objective being to create hybrids of corn with a certain architecture of the root system (rougher and deeper), which leads to an increase in the efficiency of the use of fertilizers , which ultimately leads to the reduction of applied nitrogen doses.

3. What does it add to the subject area compared with other published material?

Previous research has highlighted the vigor of corn hybrids in the F1 generation by studying the intensity of the heterosis phenomenon on the aerial part of the plant and less on the underground part, which has a significant role in the absorption of nutrients and water from the soil. The study brings added value by the fact that it is possible to obtain corn hybrids that show a greater efficiency in the use of nitrogen from the fertilizer to obtain grain production so as to increase the yield of corn grains obtained per kilogram of nitrogen applied and implicitly to be able to reduce applied nitrogen doses, a very important technological link in the context of the current energy crisis and the promotion of a healthy environment (reducing soil pollution with nitrates).

4. What specific improvements should the authors consider regarding the methodology? What further controls should be considered?

Compared to the initial evaluation, I also return with some critical observations on the work methodology:

• From the data presented, it follows that there are no variants with N0, because in the paper, on lines 116-117, it is shown that initially a common agricultural fund of: 105 kg ha-1 P2O5, 41 kg ha-1 N and 45 kg was administered ha-1 K2O. Therefore, the doses of 0-150 kg N, specified as experimental variants, are only those applied in vegetation at the V6 stage, but the corn plant had available for nutrition a total of applied nitrogen, of: 41-191 kg ha- 1. Therefore certain calculations involving nitrogen efficiency should be reported at these doses: N41-N191.

 Please check and rectify !!!

• It is not necessary to specify the period of application of herbicides and insecticides (it is not relevant in the present work). If, however, you mention the technological links of weed or pest control, the names of the species controlled and the active substance of the applied products should be mentioned.

5. Please describe how the conclusions are or are not consistent with the evidence and arguments presented. Please also indicate if all main questions posed were addressed and by which specific experiments.

Please correlate the conclusions with the experimental data presented !!

The first sentence from the conclusions: "Maize hybrids exhibit a steeper-denser-deeper root architecture over time in increased NIE and NUE", does not correlate with the data in tables 2 and 4, from which it follows that at a greater angle of root formation, correspond to higher values ​​of NIE and NUE.

6. Are the references appropriate?

The cited references are relevant to the topic addressed in this paper, being generally research in the field of corn plant improvement, and also in the field of plant nutrition management. Regarding the link between heterosis in maize and the assimilation of nitrogen from the soil, the cited references present the vigor of the aerial part and the correlation of the degree of development of the plant in the extraction of nitrogen from the soil and its storage in the obtained production. The cited researches are starting points in establishing the relationship between the heterosis of the root architecture and the assimilation level of nitrogen.

7. Please include any additional comments on the tables and figures and quality of the data.

In table 4, which of the columns represent: Nuptfert and Nuptunfert, which were used in the calculation formulas for NRE and NIE ???

I checked the calculation of NRE and NIE, taking into account the difference „Plant N (kg ha^-1)”, on N150 and N0 and the figures are different. Please recalculate!

 If I'm wrong, I'm sorry!

 

Final decision on publication of material!!

 

After the additional evaluation, I agree with the publication of the work, but only after the rectification of inconsistencies and a better explanation of the work methodology.

 

01.08.2024

REVIEWER_1

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The researchers investigated the heterosis of maize root architecture and nitrogen use efficiency among hybrids developed from different eras. The manuscript needs a minor revision and can be accepted after addressing my below comments.

Title:

·       The title can cover the major topics of the study.

Abstract:

·       The abstract was well written. The justification, key findings, implications, and outcomes were comprehensively presented in a good flow.

Keywords:

·       Considering adding a few more keywords related to the study but were not mentioned in the title of the manuscript yet.

Introduction:

·       Please expand this section by providing information whether improving the belowground biomass like root attributes would negatively affect the aboveground biomass and final grain yield or not.

·       The rhizosphere of maize is mainly concentrated on the topsoil (0-30 cm), while authors suggest that a deeper root system is better. Please clarify.

Methods:

·       No grain yield measurement? The final grain yield is important to validate the hypothesis whether enhanced root system and NUE could support assimilation and final yield, or vice versa.

Results:

·       This section needs to confirm whether higher heterosis of new hybrids as compared to the old one was merely due to superior hybrid performance alone or coupled with low line per se of their corresponding parents? Since high heterosis sometime reflects the poor performance of line per se rather than better hybrid performance.

Discussions:

·       The last paragraph is repetition from the result part, and it is difficult to understand. Considering rewriting that part to be clearer and more understandable.

·       Add more sub-section/paragraph of the discussion by providing the limitation of the study and suggestions for future research.

Conclusion:

·       Conclusion can address all research objectives mentioned in the manuscript.

References

·       All citations are listed in the references, update, and relevant to the research topic.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Minor editing of English language is required.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf