Transpiration Responses of Herbicide-Resistant and -Susceptible Palmer Amaranth (Amaranthus palmeri (S.) Wats.) to Progressively Drying Soil

Round 1

Reviewer 1 Report

Review opinions for the manuscript titled by “Transpiration responses of herbicide-resistant and -susceptible  Palmer amaranth [Amaranthus palmeri (S.) Wats.] to progres-sively drying soil”

 

Evaluating the performance of herbicide-resistant and susceptible weed ecotypes to progressive drought can provide insights into whether resistance trait(s) increased or reduced the fitness of a resistant population, which will provide foundation for weed management in the drought condition. In the present study, the authors conducted two kinds of experiment in the greenhouse to evaluate drought tolerance differences between Palmer amaranth accessions resistant to S-metolachlor or glyphosate and their susceptible counterparts. Their results showed that there existed differences between S-metolachlor-resistant and -susceptible accessions in the threshold FTSW (fraction of transpiration soil water), however, no difference between glyphosate-resistant and - susceptible accessions.

• Some keywords may be deleted, such as metabolic resistance; stomatal closure. I think these traits (associated with these key words) did not measure in the experiments.
• Materials and Methods

        P4L147, what is your replications?

• Other minor error:

          P5L103, please insert a space between the ‘100seeds’.

 

Author Response

Please see attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

General comments:

The Authors presented a manuscript entitled “Transpiration responses of herbicide-resistant and -susceptible Palmer amaranth [Amaranthus palmeri (S.) Wats.] to progressively drying soil", submitted to Agriculture, MDPI.

Two experiments were conducted in the greenhouse at the Milo J. Shult Agricultural Research & Extension Center, University of Arkansas (US), to assess the performance of herbicide-resistant and susceptible weed ecotypes to drought events. Furthermore, it was evaluated if resistance trait(s) increased or reduced the fitness of a resistant population. In detail, daily transpiration rate and daily water content were measured and converted to normalised transpiration ratio (NRT), and fraction of transpirable soil water (FTSW), respectively. The relationship between NTR and FTSW was quantified using a two-segment linear regression analysis, and the threshold value (break-point) was estimated for susceptible and resistant populations. 

Overall, I found the manuscript interesting, clear, and in line with the Journal requirements. The only weakness is in the presentation of the Introduction. I would have appreciated a presentation focusing on herbicide-resistant and susceptible weed ecotypes to drought, rather than the effect on corn and soybean yield. This would have also contributed to better present and articulate the hypothesis of the research, and not only in the last short paragraph before the objective, although it is a style choice! All the other sections of the paper are well prepared.

Specific comments:

Lines 65-68 The Authors described how “Plant transpiration in response to a drying soil has been well characterized by previous research and reported to display two phases: (1) the initial plateau where transpiration is optimal and (2) a linear decline in response to a drying soil.” Maybe Figure 2 and Figure 3 might be represented transposing the origin of the axis to the right side? In this way it is possible to represent a plateau and decreasing curve as described in M&M.

Author Response

Please see the attached Response to Reviewer 2

Author Response File: Author Response.docx

Reviewer 3 Report

In manuscript agriculture-1583777, Kouame et al. carried out an interesting comparative study between susceptible and resistant populations (with known resistance mechanisms) to S-metolachlor and/or glyphosate based on transpiration rates subjected to hydric stress, with the aim of identifying possible competitive differences for future global warming scenarios. The experiments are simple but they yielded relevant results. The manuscript is generally well written and intellectually well argued; however, various typos can be found throughout the manuscript. I have some review comments to improve the quality and readability of the paper. The minor corrections are listed below:

L16: herbicide resistance traits ......... fitness cost of resistant weed populations.

L26-32: add more relevant results to the abstract. what were the FTSW breakpoints for the glyphosate R and S populations?. In addition, the main conclusion of the study must be added to the abstract - these results suggest that S-metolachlor-resistant and glyphosate-resistant Palmer amaranth populations will not be at a competitive disadvantage compared to susceptible biotypes

L40: update the information for the most recent period, as 2018-2020

L73: start a new paragraph from this line (add it to L78-85).

L85:  start a new paragraph from this line - Weeds harboring resistance mechanisms may impart ……..

L103: 100 seeds

L138-140 and L304: Why didn't you use populations collected within the same area or with high genetic proximity?

Figure1: add legends within the figure to differentiate the populations

L156: describe the composition of the nutrient solution

L154-170: It is not clear which were the water stress regimes evaluated: 20, 40, 50, 80%?

L205-215: Are 7 references really necessary to describe statistical methods? select only the most representative reference in each case

L219-220: present the results in the order they were described in the methodology, i.e., start by presenting the results for glyphosate or reverse the order of the methodology

L221-222: bold? Why?

Figure 2 and 3: the subfigures are unnecessarily large (size does not make your results more relevant). to be able to observe differences it is necessary to reduce the percentage of zoom visualization. I suggest they be reduced to the ideal size for a double column publication.

L230, 262: italics for A. palmeri

L244-47, 284, 293, 300, 303, : check that the S for S-metolachlor is italicized throughout the manuscript

L282-283: same comment as for L219-220

L293: check for double spaces here and throughout the manuscript

L327: EPSPS does not have a role in mitigating drought stress in A. palmeri (it is important to specify the species, because the penalty fitness is variable for each weed)

L331: italic for Lolium rigidum

L340-350: It would be important to highlight that the results suggest that the R a S-metolachlor populations may even become more competitive than the S populations.

Author Response

Please see attached Response to Reviewer 3

Author Response File: Author Response.docx