Genotypic Variability in Growth and Leaf-Level Physiological Performance of Highly Improved Genotypes of Pinus radiata D. Don Across Different Sites in Central Chile
, Marco Yáñez 2, Carlos Magni 3, Eduardo MartÃnez-Herrera 3, Karen Peña-Rojas 4, Sergio Donoso 4, Marcos Carrasco-Benavides 5 and Samuel Ortega-Farias 6
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript by Espinoza et al. is devoted to analysis of genotypic variability in growth and leaf-level photosynthetic and transpiration parameters in various genotypes of Pinus radiata D. The work seems to be interesting; however, I have some comments and questions.
Main point:
- Author analyzed stability of top and bottom families to analyze relation of this stability to improving genotypes. However, authors do not seem to analyze standard deviations (SDs) or coefficient variations (Cvs) of different genotypes. Were SDs or Cvs lower in bottom families? Were SDs or Cvs of photosynthetic and transpiration parameters correlated with growth parameters? The last question is especially important because if increasing/decreasing stability of physiological parameters can modify plant growth under different environmental conditions, these correlations should be observed.
Specific points:
- Introduction: I suppose that background and importance of the investigations should be described in more details. E.g., it is interesting: What were relations between variations in physiological characteristics and productivity in other trees?
- Section 2.2: What type of illumination was used? Was it narrow- or broadband source? Was blue, red, white or other light used? It should be described.
- Equation (1) should be described in more details, and references should be added.
- Section “Differences in gas exchange and Chl a fluorescence” (3.2?): Average values of Asat, gs, E, etc., and their SD/SE seem to be absent in the section. I suppose these parameters should be shown.
Author Response
Rewiewer1:
Author analyzed stability of top and bottom families to analyze relation of this stability to improving genotypes. However, authors do not seem to analyze standard deviations (SDs) or coefficient variations (Cvs) of different genotypes. Were SDs or Cvs lower in bottom families? Were SDs or Cvs of photosynthetic and transpiration parameters correlated with growth parameters? The last question is especially important because if increasing/decreasing stability of physiological parameters can modify plant growth under different environmental conditions, these correlations should be observed.
Answer: Thanks for the comment. In this new version we provide coefficients of variation for top and bottom families both in growth (Lines 190 to 194) and gas exchange parameters (Lines 215 to 217). We have also provided a new Table 4 (Line 234) for these traits. CVs for top and bottom families were similar and high (i.e., CVs > 30%), thus it was corroborated the lack of relationship and low correlation coefficient initially reported in Figure 4.
Introduction: I suppose that background and importance of the investigations should be described in more details. E.g., it is interesting: What were relations between variations in physiological characteristics and productivity in other trees?
Answer: We added some studies in forests species for the relations between physiological traits and productivity (Lines 57-63). The references have been provided accordingly (Lines 384 to 390).
Section 2.2: What type of illumination was used? Was it narrow- or broadband source? Was blue, red, white or other light used? It should be described.
Answer: Thanks for the comment. We usually do not report this type of information, but as suggested, technical information for this point is provided in Lines 131-132.
Equation (1) should be described in more details, and references should be added.
Answer: We appreciate this comment by the reviewer. Respectfully we believe that the description of fixed and random factors, and the hierarchical design of families nested within the ranking is well explained. Similarly, the assumption that the errors are independent and identically normally distributed with mean 0 and variance (Line 177 and Line 180) and the justification for considering families a fixed factor (Lines 180 to183), are both clear.
Section “Differences in gas exchange and Chl a fluorescence” (3.2?): Average values of Asat, gs, E, etc., and their SD/SE seem to be absent in the section. I suppose these parameters should be shown.
Answer: We added a new figure 2 (Line 230) containing this information. The numeration of figures was modified accordingly.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript deals with an important theme in forestry and plant physiology, mainly regarding the breeding of Pinus radiata in the background of climate change. The study examines key queries regarding genotypic variability in growth and physiological characters, and its results add to the understanding of advanced breeding programs. The experimental design, utilizing 30 full-sib families across three sites, provides a robust dataset. The inclusion of chlorophyll a fluorescence (OJIP-test parameters) adds a valuable dimension to the physiological assessment.
Given the practical implications for tree improvement and forest management, the manuscript has the potential for publication.
Even though the study is well-designed, there are numerous areas which need to be addressed before the manuscript is considered for acceptance which are outlined below.
Clearly state the most important outcomes from the physiological perspective. Instead of leading with the lack of family x site interaction for all parameters, perhaps highlight the observed family differences in chlorophyll fluorescence variables earlier, as this seems to be a main positive outcome.
The values given in the abstract for HT, DBH, VOL, Asat, gs, E, and iWUE are means of ranges and do not immediately express the importance of the outcomes (e.g., which families or sites displayed these ranges). Concisely describe the importance of the PIABS and Fv/Fm outcomes more obviously.
Even though the introduction sets the stage well, think about more clearly mentioning the gap this study addresses beyond “no studies have been conducted to investigate if highly improved genotypes exhibit uniformity in physiological performance across different sites.” Perhaps highlight the significance of understanding the physiological basis of growth stability in advanced breeding lines, especially under future climate scenarios.
Make sure all tables and figures are plainly referenced and integrated into the text. Provide clearer legends for Figure 1, 2 and 3. For Figure 3, it would be beneficial to explain what the “ns” (non-significant) specifies directly in the figure caption for readers less familiar with statistical notation, or remove it from the figure.
While providing variations, be more precise. For instance, in spite of “Differences in gas exchange and Chl a fluorescence,” openly mention what differences were found and among which factors (site vs. family).
Provided that chlorophyll fluorescence variables displayed family-level variation, this section needs to be lingering. Deliberate in more detail the implications of the observed variation in PIABS and Fv/Fm for selection and breeding, perhaps linking it more strongly to stress tolerance or resource use efficiency.
Although the outcomes show physiological uniformity for some characters, deliberate the implications of this in greater detail. Could it mean that these specific characters are no longer under strong selection pressure in highly improved genotypes? Or that the environmental conditions during assessment were not adequately stressful to stimulate variation?
If the authors want to retain the hypothesis about leaf area, they should recognize its hypothetical nature more clearly or propose it as a future research direction. Providing the calculation for crown width without directly measured leaf area might raise queries about its direct applicability.
Restate the practical implications of the outcomes for breeding programs in Pinus radiata, particularly regarding water-limited environments.
The manuscript concludes that “Needle gas exchange traits are not a promising tool for screening superior performance in advanced breeding genotypes.” Although this is a direct deduction from their data, ponder if this declaration is too absolute. Could there be precise circumstances or developmental stages where these characters would be more variable or informative?
In summary, the manuscript offers some important facts and deals with a significant research query. The manuscript should be with cautious amendments, chiefly in strengthening the interpretation of physiological outcomes, refining the discussion, and making minor English language enhancements.
Comments on the Quality of English LanguageThe English language quality is generally good and the manuscript is readable. However, there are a few minor instances where refinement would ameliorate clarity and flow.
Some sentences need to be more concise.
Ensure consistent use of italics for species names (e.g., Pinus radiata). This appears to be generally good, but a final check is always useful.
Author Response
Reviewer 2:
Clearly state the most important outcomes from the physiological perspective. Instead of leading with the lack of family x site interaction for all parameters, perhaps highlight the observed family differences in chlorophyll fluorescence variables earlier, as this seems to be a main positive outcome. The values given in the abstract for HT, DBH, VOL, Asat, gs, E, and iWUE are means of ranges and do not immediately express the importance of the outcomes (e.g., which families or sites displayed these ranges). Concisely describe the importance of the PIABS and Fv/Fm outcomes more obviously.
Answer: As suggested, we rearranged results for the Abstract section and provided average values for growth and gas exchange in top-15 and bottom-15 families (Lines 29 to 40). Additionally, we added a new paragraph highlighting the importance of parameter PIABS (Lines 42-44).
Even though the introduction sets the stage well, think about more clearly mentioning the gap this study addresses beyond “no studies have been conducted to investigate if highly improved genotypes exhibit uniformity in physiological performance across different sites.” Perhaps highlight the significance of understanding the physiological basis of growth stability in advanced breeding lines, especially under future climate scenarios.
Answer: We appreciate this comment by the reviewer. As suggested, we added a new paragraph at the end of the Introduction highlighting the importance of this point (Lines 84 to 87).
Make sure all tables and figures are plainly referenced and integrated into the text. Provide clearer legends for Figure 1, 2 and 3. For Figure 3, it would be beneficial to explain what the “ns” (non-significant) specifies directly in the figure caption for readers less familiar with statistical notation, or remove it from the figure.
Answer: We double-checked that Tables 1, 2, and 3 were clearly called in the body of the text. In this new version we added a new Table 4 properly called in the body of the text. In the caption of Figure 4 (ex - Figure 3), we explained the meaning of n.s. in the inset equations (Lines 252 to 253).
While providing variations, be more precise. For instance, in spite of “Differences in gas exchange and Chl a fluorescence,” openly mention what differences were found and among which factors (site vs. family).
Answer: The title for section 3.2 was changed from ‘Differences in gas exchange and Chl a fluorescence’ to ‘Differences in gas exchange and Chl a fluorescence for genotypes across sites’ (L206). We believe that in Lines 210 to 215 it can be seen what differences were found (i.e., E, Fv/Fm, PIABS, ψEo, and ΔVIP) and among which factors (families and sites). Similarly, in Table 3 it can be seen that no family x site interaction was observed.
Provided that chlorophyll fluorescence variables displayed family-level variation, this section needs to be lingering. Deliberate in more detail the implications of the observed variation in PIABS and Fv/Fm for selection and breeding, perhaps linking it more strongly to stress tolerance or resource use efficiency.
Answer: At the end of the Discussion section, we discuss this topic and the implications for selection of superior genotypes (L328-341).
Although the outcomes show physiological uniformity for some characters, deliberate the implications of this in greater detail. Could it mean that these specific characters are no longer under strong selection pressure in highly improved genotypes? Or that the environmental conditions during assessment were not adequately stressful to stimulate variation?
Answer: We appreciate this comment. However, we respectfully consider that the topic of selective pressure lies beyond the scope of our study. In general, traits with high heritability may become fixed after several generations of recurrent selection. In our case, we do not have heritability estimates, as obtaining them requires extensive and costly breeding trials involving hundreds or even thousands of individuals. Moreover, the genotypes included in our study are currently in the third cycle of crossing, which we believe is still too early for any particular trait to be considered fixed. In the case of the environmental conditions, they were stressful because we measured gas exchange and Chl a fluorescence in the hottest months of summer in the Southern Hemisphere (Line 128).
If the authors want to retain the hypothesis about leaf area, they should recognize its hypothetical nature more clearly or propose it as a future research direction. Providing the calculation for crown width without directly measured leaf area might raise queries about its direct applicability.
Answer: We agree with the reviewer in this point and we early recognized its limitation and the need of further research. In Line 305 we added a short sentence.
Restate the practical implications of the outcomes for breeding programs in Pinus radiata, particularly regarding water-limited environments.
Answer: This topic is discussed in Lines L328-341. The references have been provided accordingly (Lines 493 to 495).
The manuscript concludes that “Needle gas exchange traits are not a promising tool for screening superior performance in advanced breeding genotypes.” Although this is a direct deduction from their data, ponder if this declaration is too absolute. Could there be precise circumstances or developmental stages where these characters would be more variable or informative?
Answer: We agree with the reviewer that this is not and absolute declaration. We pondered this sentence and slightly change its redaction to make it applicable to our genotypes (Lines 312-313 and Line 347).
Comments on the Quality of English Language
The English language quality is generally good and the manuscript is readable. However, there are a few minor instances where refinement would ameliorate clarity and flow.
Answer: We double-checked English Language.
Ensure consistent use of italics for species names (e.g., Pinus radiata). This appears to be generally good, but a final check is always useful.
Answer: We double-checked consistent use of italics in scientific name of trees and changed accordingly (e.g., Line 200).
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAuthors completely considered my comments. I suppose that this interesting work can be accepted.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe revised manuscript underwent further rigorous review, with critical evaluation of prior revisions. The authors addressed previous concerns comprehensively and provided well-supported responses to reviewer queries. These revisions significantly improved the manuscript. Only minor grammatical errors remain, which can be corrected during final proofreading if accepted.
