Impact of Irrigation and Artificial Pollination on Macadamia: Fruit Set and Yield

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The present study, "Impact of Irrigation and Artificial Pollination on Macadamia: Fruit Set and Yield," is a valuable contribution that addresses a highly relevant agronomic topic. The objectives are clear, the design is consistent, and the results are consistent with the objectives.

Some points could be improved to make the manuscript more attractive:

The abstract lacks quantitative values; adding numerical values ​​such as yield and fruit set percentages would make the abstract more attractive. It is also somewhat long, so it is recommended to summarize it.

The introduction is well developed and could be improved with the context of similar studies in other nut crops such as almonds or hazelnuts, where the interactions between irrigation and pollination have also been explored.

Section 2.2 presents a correct experimental design appropriate for the objectives, but the statistical description is limited, and the design, although valid, is not statistically very robust due to the low number of replications and the lack of detail regarding the analyses. Therefore, this section should be strengthened with greater detail.

Furthermore, the use of letter comparisons (Duncan's test) is only generally mentioned, but the structure of the full analysis is not described.

Nor is the software used for the statistical analysis mentioned.

Justify the sample size. If n=3 trees/treatment, include a brief justification (logistical limitations for evergreen trees) or at least discuss the sensitivity (minimum detectable effect with α=0.05).

Figure 1a is not visible to the naked eye, so you should consider displaying them separately for better visualization.

The conclusions are well supported by the results and highlight the synergistic effect of irrigation and artificial pollination. It would be more relevant if the potential economic implications of adopting this practice were analyzed, which, ultimately, is what the research seeks: its feasibility.

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Article review

Title: Impact of Irrigation and Artificial Pollination on Macadamia: Fruit Set and Yield

Overall, this article is well-structured, methodically sounds, and provides valuable insights on improving macadamia yield through integrated irrigation and pollination management. The experimental rigor, comprehensive physiological analyses, and clear data presentation are strengths. The study also identifies directions for further research such as expanding paternal cultivar diversity and extending treatment periods into fruit development stages.

This detailed critique highlights the articleʼs strong experimental design, relevant scientific contributions, and clear writing foundation, while pinpointing areas where clarity, accessibility, and presentation could be enhanced to maximize impact and readership.

Title and abstract

The title accurately reflects the study's focus on how irrigation and artificial pollination affect Macadamia fruit set and yield. The abstract effectively summarizes the study’s objective, methods, and key findings, highlighting the significance of combining irrigation with artificial pollination to improve pollen viability, fruit set, and overall yield in Macadamia cultivation. The abstract provides clear keywords, aiding in indexing and search ability.

• While clear and descriptive, the abstract could better highlight the study's novelty and limitations for a more balanced overview.
• The abstract does not explicitly mention the study’s sample size, which is important for assessing robustness.

1. Introduction:

The introduction presents a well-contextualized background, describing Macadamia’s origin, challenges with flower and fruit abscission, and the importance of water and pollination on yield. It cites existing literature on drought effects and pollination importance, noting a research gap in studying their combined effects. The rationale for selecting cultivar 'A16' in Yunnan Province is well-presented, grounding the study in a relevant agricultural context.

• The introduction extensively reviews relevant literature but lacks a critical discussion of conflicting findings or gaps beyond the focus on irrigation and pollination synergy.
• There is limited mention of potential limitations or alternative hypotheses that might influence fruit set and yield, such as pest impacts or soil nutrition, which might contextualize broader yield variability.

2. Materials and Methods

Experimental Materials and Design

The study uses uniform, 11-year-old 'A16' Macadamia trees, detailing key growth parameters to ensure sample consistency. The two-factor experimental design distinguishes natural vs. artificial pollination and irrigation vs. drought treatments clearly, with replication detail.

• The study uses a relatively small sample size of 12 trees, which may limit the statistical power and generalizability of the findings.
• The experimental design involved only one maternal (‘A16ʼ) and one paternal (‘951ʼ) cultivar. This narrow genetic base restricts the applicability of findings to other Macadamia varieties with different compatibility or stress responses.
• Artificial pollination was conducted in a very specific time window (24-26 hours after floret opening, 9:00 to 11:00 AM) , which may not capture the full range of natural pollination timing and effectiveness.

 

Pollination and Irrigation Treatments

The use of a compatible paternal cultivar ('951') and the methodology of pollen application are rigorously described. Drought conditions are simulated by rain exclusion, and irrigation frequency and moisture targets specified, supporting reproducibility.

Sampling and Measurements

Systematic sampling at multiple developmental stages for racemes and leaves is described, ensuring thorough temporal data collection. Physiology assays of pollen viability, protein, sugar, antioxidant enzymes LSOD, POD, CATM, and oxidative damage LMDA) are well-detailed with references to established protocols.

• Sampling focused primarily on the 2nd to 3rd most recent leaves and mid-canopy racemes, which may not represent tree-wide variability.
• The study duration spanned just a single season (January to August 2024), limiting insights into inter-annual variability or longer-term effects.
• Stress induced by drought was simulated by plastic film to block rainfall, which may not fully replicate natural field drought conditions, including soil moisture gradients or microclimate changes.

 

Fruit Setting and Yield Metrics

Definitions and formulas for important economic traits like fruit setting rate, abscission rate, yield increase, and kernel yield are articulated clearly.

Physiological and Yield Measurements

• While comprehensive, the biochemical assays relied on a limited number of replicates (usually n=3), which might not capture natural biological variation.
• The analysis did not include direct measurements of other possibly influential factors such as nutrient status, pest/disease pressure, or soil physical properties.
• Yield increases were measured per plant but the plot or orchard scale implications were not elaborated upon, restricting practical extrapolation.

3. Results

Morphological Effects and Physiological Effects

Presentation of data on pollen germination rates, raceme length, and shoot internode length under different treatments shows quantitative improvements with irrigation and artificial pollination. Morphological data are supported by microscopic imagery and statistics, demonstrating treatment impact. The article details changes in osmolytes, antioxidant enzyme activities, proline accumulation, and oxidative stress markers, showing distinct responses in racemes and leaves depending on treatments. Data indicate drought increases oxidative stress enzymes and MDA, whereas irrigation maintains higher protein and sugar content in racemes.

• The results show significant trends mostly under artificial experimental conditions, but the ecological validity remains uncertain due to the controlled pollination and irrigation regimes.
• Leaf physiological traits showed inconsistent changes across treatments, suggesting complex underlying interactions which were not fully explored or explained.
• No significant changes were found in flower number per raceme or many fruit quality parameters, indicating the treatments’ effects may be limited to quantity rather than quality, which may affect economic value but was insufficiently discussed.

 

Fruit Set and Yield Performance

There are significant increases in fruit set with both irrigation and artificial pollination, especially combined. Yield and fruit count improvements are quantified precisely, with combined irrigation and artificial pollination achieving the highest increases (77% yield increase). The temporal dynamics of fruit set rate decline and stabilization are clearly illustrated.

• Despite significant increases in fruit set and yield from combined treatments, the lack of significant differences in some treatments (e.g., between irrigation and drought + artificial pollination) suggests variability that may undermine the predictability of the interventions.
• Fruit abscission rates did not significantly differ among treatments, which is a critical factor affecting final yield but was not deeply analyzed.

Economic Fruit Traits

Fruit transverse diameter improves with irrigation + artificial pollination, but other fruit quality traits show no significant differences. This distinction suggests morphological traits may be more genetically controlled or less sensitive to the treatments during early fruit development.

4. Discussions

The discussion emphasizes the detrimental effects of drought stress on Macadamia reproductive success and how artificial pollination partially mitigates this. It highlights the synergy between irrigation and pollination in improving physiological and yield parameters. The paper thoughtfully addresses discrepancies in osmolyte responses between racemes and leaves and relates enzyme activities to stress severity. The authors caution on using single paternal cultivars and limited treatment windows as potential limits to observed fruit quality differences.

• The discussion provides extensive explanation but could better address why certain expected effects (such as improved fruit quality or more consistent leaf physiological responses) were absent.
• There is limited critique of the studyʼs constraints, such as genotype limitation or possible artificial conditions influencing results.
• Alternative explanations for observed effects, such as influence from other environmental stressors or biotic factors, receive minimal attention.
• The biological mechanisms discussed focus on osmotic regulation and antioxidant responses but do not address other possible physiological or molecular pathways potentially involved in fruit set and stress responses.

5. Conclusions

The conclusions synthesize findings well, establishing stage-specific local management recommendations to boost fruit retention. The recommendation for combined irrigation and artificial pollination as best practice is clearly supported by the data. Quantitative improvements in pollen viability, shoot growth, fruit set, and yield are succinctly summarized, providing actionable insights for Macadamia growers.

• Conclusions emphasize the benefits of combined irrigation and artificial pollination but may overstate efficacy given the limited genetic diversity and short duration of the study.
• The recommendation to apply treatments during the first six weeks post-fruit set is sound but would benefit from additional longitudinal validation.
• Potential economic or practical limitations of applying artificial pollination at scale were not considered.

6. References

Contains relevant and recent citations covering macadamia biology, irrigation, pollination, drought stress, and physiological assays.

Overall Assessment

This article is a comprehensive, well-structured scientific study combining physiological, morphological, and yield data to elucidate how irrigation and artificial pollination interact to enhance Macadamia production. Methodologies are detailed and rigorous, supporting reproducibility. Results are clearly presented and statistically validated. Discussion thoughtfully integrates findings with existing literature and biological theory. The article provides valuable practical recommendations for improving Macadamia yields, especially in drought-prone regions.

Overall Weaknesses

• Limited genetic scope: Only a single maternal and paternal cultivar was tested, limiting broad application.
• Small sample size and replication: Twelve trees and limited biological replicates may reduce statistical robustness.
• Short study duration: One growing season reduces insight into year-to-year variability.
• Artificial conditions: Use of rain exclusion and controlled pollination may not fully represent field conditions.
• Inconsistent physiological findings: Some leaf responses were inconsistent and not fully explained.
• Fruit quality impact unclear: No significant changes in key fruit quality traits, potentially limiting commercial relevance.
• Limited exploration of yield determinants: Other factors affecting yield were not addressed, possibly confounding results.
• Scalability and economic aspects: The practical feasibility of artificial pollination in large scale commercial settings was not discussed.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I hope that the comments provided have contributed to improving the quality of the article. I would like to express my best wishes for your future academic and professional achievements.