Relationship between Endogenous Ethylene Production and Firmness during the Ripening and Cold Storage of Raspberry (Rubus idaeus ‘Heritage’) Fruit

Round 1

Reviewer 1 Report

The main aim of the paper is to investigate the Relationship of endogenous ethylene production and firmness during ripening and cold storage of raspberry ‘fruit. Raspberry has short shelf life due to rapid softening and therefore highly susceptible to damage during harvesting storage. So any effort regarding the improvement of postharvest life will be of great significance. The information provided in the paper is interesting and is helpful in understanding the ripening behavior of raspberry. The study investigates an interesting treatment to reduce loss of fruits in raspberry, but the treatment is just done one year and in one variety. The paper is well written and provides all the necessary relevant information and is worth publishing in the esteemed journal with following suggestions if possible.

1. Add second year data if possible which will provide more reliable results.
2. There are issues of language in the manuscript. If possible rectify it by a native English editor.
3. Add pictures of different stages if available.

Author Response

Reviewer 1

The main aim of the paper is to investigate the Relationship of endogenous ethylene production and firmness during ripening and cold storage of raspberry' fruit. Raspberry has short shelf life due to rapid softening and therefore highly susceptible to damage during harvesting storage. So any effort regarding the improvement of postharvest life will be of great significance. The information provided in the paper is interesting and is helpful in understanding the ripening behavior of raspberry. The study investigates an interesting treatment to reduce loss of fruits in raspberry, but the treatment is just done one year and in one variety. The paper is well written and provides all the necessary relevant information and is worth publishing in the esteemed journal with following suggestions if possible.

Add second year data if possible which will provide more reliable results.

Previously, we have published data on the quality of heritage raspberries in the same locality and the same variety (Fuentes et al., 2015; Monsalve et al., 2018; Bernales et al., 2019). Therefore, we improve the discussion of the results to point out this aspect. We are aware of the lack of another season for postharvest trials in two seasons. This year, we are setting up pre-harvest treatment trials with 1-MCP to have more accurate data on the effect of ethylene on raspberry ripening and its effect on firmness at harvest and during storage. Unfortunately, obtaining this data and processing, it will take longer.

There are issues of language in the manuscript. If possible rectify it by a native English editor.

These suggestions were considered, and the manuscript will be rectified by an English editor. However, this correction can't be included in this version, and it will be included in the final version of the manuscript.

Add pictures of different stages if available.

As the reviewer suggests, pictures of different stages were added (Figure 1)

The authors thank the Reviewer comments

Reviewer 2 Report

The research relates to a single raspberry cultivar ‘Heritage’

There are two components of research

– a developmental series using fruit harvested at different stages of development

            - the effect of MCP on fruit harvested immature when stored at 0 and 10°C

The introduction relies on the groups own papers (5, 6, 8) plus some others.  There are other papers on raspberry fruit ripening, ethylene and the drupelet and receptacle aspects not referenced.

A wider review of the literature may have influenced the approach taken.

The developmental series repeats previously published work of the last 30 years

Ethylene production of the drupelets and receptacle has been published previously

The response to MCP is newer.

The focus on ethylene does not seem to recognize the existing information on the variability in ethylene production that exists among raspberry cultivars. 

The MCP concentration used seems very high (is it not usually used in the ppb range?). How does this relate to other treatments?

The firmness technique should have some detail – quoting reference 12 is no help.  How ‘firmness’ is measured is important for raspberry as there are a range of fruit texture analyser methods used, each of which says something different about the fruit.

Why were the respiration measurements not made at the storage temperatures?  Bringing the fruit to 20°C adds another factor.

The boxplots should be defined.

In the results (and methods), the separation (or not) of LG fruit into drupelets and receptacle should be made clear.  And if it was not possible to separate (without too much damage) then how is there data in Figure 1?

In Figure 1 and others – the statistical comparison is among the 3 treatments and not just between control and 1-MCP treated fruit?

The T=0 points suggest that there was significant effect of 3 h at the storage temperatures?

This T=0 point includes treatment at 20°C for both storage temperatures and then respiration and ethylene measured at 20°C?

Any explanation for the seemingly anomalous respiratory data on day 2 and day 5 at 0°C? 

The data in the Appendix should be part of the main results.

Discussion is as if all raspberries are the same. The discussion can only be specific to ‘Heritage’ and should not be extrapolated to represent raspberry in general without a discussion of where ‘Heritage’ fits in relation to other raspberries.

The interpretation pays little attention to the fact that development and ripening in raspberry is a continual process rather having a discrete ripening as occurs in fruit such as apple or banana. The comment that ripening starts at W in the introduction is from their own previous papers (references 5, 6, 8).  

The data from the storage trial should be discussed in the context of what happens to a detached immature fruit – not a fully grown or fully developed fruit. What changes as the fruit ripen are dependent on being attached to the parent plant? Raspberry is well known for having to develop to almost full ripeness on the cane before harvest.  This is particularly relevant to TSS.

Discussion relies a lot on strawberry on the basis of it being non-climacteric

The conclusion could have been written before doing any of this work.

The written English requires an editor to correct.

Author Response

Reviewer 2

The research relates to a single raspberry cultivar 'Heritage'

There are two components of research

– a developmental series using fruit harvested at different stages of development

            - the effect of MCP on fruit harvested immature when stored at 0 and 10°C

The Introduction relies on the groups own papers (5, 6, 8) plus some others. There are other papers on raspberry fruit ripening, ethylene and the drupelet and receptacle aspects not referenced.

A wider review of the literature may have influenced the approach taken.

As the reviewer suggests, other papers were included as references to improve the Introduction and discussion.

The developmental series repeats previously published work of the last 30 years

Ethylene production of the drupelets and receptacle has been published previously

The response to MCP is newer.

The focus on ethylene does not seem to recognize the existing information on the variability in ethylene production that exists among raspberry cultivars.

As the reviewer suggests, the ethylene production of the drupelets and receptacles has been published previously. However, it was necessary to describe changes during the maturation to be able to relate the ripening with what was observed during the postharvest trials.

The MCP concentration used seems very high (is it not usually used in the ppb range?). How does this relate to other treatments?

As the reviewer suggests, this mistake was reviewed with the staff, and the units were corrected to ppb.

The firmness technique should have some detail – quoting reference 12 is no help. How 'firmness' is measured is important for raspberry as there are a range of fruit texture analyser methods used, each of which says something different about the fruit.

These suggestions were considered, and more details were included.

Why were the respiration measurements not made at the storage temperatures? Bringing the fruit to 20°C adds another factor.

The inclusion of evaluations in chamber exit conditions and after x days at 20 degrees Celsius seeks to simulate the shelf behaviour of the fruit. Respiration measurements seek to detect changes in tissue metabolism during the chamber situation and in the usual condition of exposure to consumption. However, the respiratory rate presents values that could be measured at storage temperature. In order to be able to measure the production of the respiratory rate and of the vegetable hormone ethylene in refrigerated conditions, in preliminary tests, both were evaluated without obtaining detectable levels; thus, for both parameters, reflections of the metabolism of the fruit and response to stress, possible modifications were considered in shelf-life conditions, in concordance with other studies in this non-climacteric fruit (see Contreras et al., 2021).

The boxplots should be defined.

The boxplots were described.

In the results (and methods), the separation (or not) of LG fruit into drupelets and receptacle should be made clear. And if it was not possible to separate (without too much damage) then how is there data in Figure 1?

This mistake was bettered in Fig 2 of the revision version of the manuscript.

In Figure 1 and others – the statistical comparison is among the 3 treatments and not just between control and 1-MCP treated fruit?

This mistake was corrected.

The T=0 points suggest that there was significant effect of 3 h at the storage temperatures?

Yes, we observed differences after 3 h of storage.

This T=0 point includes treatment at 20°C for both storage temperatures and then respiration and ethylene measured at 20°C?

Yes, t0 include treatment at 20°C, storage at 0 or 10°C and measure at 20°C.

Any explanation for the seemingly anomalous respiratory data on day 2 and day 5 at 0°C?

The anomaly may be the effect of a change at the metabolic level. However, this season, when carrying out a 1-MCP assay on the field, we want to store at least two ripening stages to see if this anomaly is maintained or if it is an effect of the type of assay.

The data in the Appendix should be part of the main results.

As the reviewer suggested, this data was included in the main results (Figure 11).

Discussion is as if all raspberries are the same. The discussion can only be specific to 'Heritage' and should not be extrapolated to represent raspberry in general without a discussion of where 'Heritage' fits in relation to other raspberries.

As the reviewer suggested, the discussion was improved and centred in "Heritage cultivar", and information from other cultivars was added to enhance the discussion.

The interpretation pays little attention to the fact that development and ripening in raspberry is a continual process rather having a discrete ripening as occurs in fruit such as apple or banana. The comment that ripening starts at W in the Introduction is from their own previous papers (references 5, 6, 8). 

Papers of other authors were included in this sentence. At white stage, the increase of soluble solids, the red colour begins to show, and a decrease in the fruit's acidity has been described in Raspberry Heritage (Perkins-Veazie and Nonnecke, 1992). Also, the white stage has been described as the first stage of maturity in the three new Chilean raspberry cultivars: Santa Catalina, Santa Clara and Santa Teresa ripening [Contreras et al., 2021].

On the other hand, to evaluate raspberry ripening as a continuous process, a non-destructive technology would be required, e.g. NIR and ethylene determination chambers in the plant. As long as we do not have this technology in place, the 1-MCP trials in the field are the closest alternative we have to date.

The data from the storage trial should be discussed in the context of what happens to a detached immature fruit – not a fully grown or fully developed fruit. What changes as the fruit ripen are dependent on being attached to the parent plant? Raspberry is well known for having to develop to almost full ripeness on the cane before harvest. This is particularly relevant to TSS.

This year we are setting up pre-harvest treatment trials with 1-MCP to have more accurate data on the effect of ethylene on raspberry ripening and its effect on firmness at harvest and during storage. Unfortunately, obtaining this data and processing, it will take longer.

Discussion relies a lot on strawberry on the basis of it being non-climacteric

As mentioned earlier, the discussion was improved with additional papers.

The conclusion could have been written before doing any of this work.

The conclusion was improved.

The written English requires an editor to correct.

These suggestions were considered, and the manuscript will be rectified by an English editor. However, this correction can't be included in this version; it will be included in the final version of the manuscript.

The authors thank the Reviewer comments

Reviewer 3 Report

The manuscript entitled “Relationship of endogenous ethylene production and firmness during ripening and cold storage of raspberry (Rubus idaeus “Heritage”) fruits” evidence observations and acknowledgement about the fruits ripening based on postharvest treatment and storage conditions. These are important to understand the fruits ripening evolution and choose the proper conditions to extend the shelf-life of fruits. Below, the authors can see my comments and my questions to improve and enhance the quality of manuscript.

Why did not the authors mention the values of total soluble solids and titratable acidity between the three treatments studied? The addition of this information will enrich the abstract section.

Also, in the Introduction, the objectives should be more descriptive, for example, in the Line 63 the authors mentioned the quality parameter…and what the quality parameters were performed? And what temperature?

Regarding the conclusion, the authors should add the main results obtained with this study, for example, the storage temperature had some effect on fruits ripening and ethylene production, pH and TSS changes?

Author Response

Reviewer 3

The manuscript entitled "Relationship of endogenous ethylene production and firmness during ripening and cold storage of raspberry (Rubus idaeus "Heritage") fruits" evidence observations and acknowledgement about the fruits ripening based on postharvest treatment and storage conditions. These are important to understand the fruits ripening evolution and choose the proper conditions to extend the shelf-life of fruits. Below, the authors can see my comments and my questions to improve and enhance the quality of manuscript.

Why did not the authors mention the values of total soluble solids and titratable acidity between the three treatments studied? The addition of this information will enrich the abstract section.

As the reviewer suggested, this information was included in the main results (Figure 11).

Also, in the Introduction, the objectives should be more descriptive, for example, in the Line 63 the authors mentioned the quality parameter…and what the quality parameters were performed? And what temperature?

These suggestions were considered, and the Introduction was improved.

Regarding the conclusion, the authors should add the main results obtained with this study, for example, the storage temperature had some effect on fruits ripening and ethylene production, pH and TSS changes?

These suggestions were considered, and the conclusion was improved.

The authors thank the Reviewer comments

Reviewer 4 Report

Dear Editor, in the manuscript Horticulturae-1569764 authors evaluated the relationship between endogenous ethylene production and firmness during ripening and cold storage of raspberry fruit. Fruit were treated with ethylene (1000 ppm) and ethylene perception inhibitor 1-methyl cyclopropene (1-MCP, 1600 ppm) and physiological and quality parameters were evaluated during ripening at 10 and 0 ºC. In general, the manuscript provides some interesting results, showing that ethylene production in whole fruit was negatively correlated to firmness loss during storage at 10 ºC but not at 2 ºC. Thus, it could be suitable for publication in Horticulturae, although the following minor comments should be considered:

- Line 25: Considerer changing “in vitro” assays to storage at 10 and 0 ºC, here and along the whole manuscript.

-Line 95: Should it be cannot instead of can?

- Line 228: Without differences among treatments?

- Line 336: Check this sentence because metabolic activity was also maintained at 0ºC and ethylene production was even higher at 0 than at 10 ºC.

Author Response

Reviewer 4

Dear Editor, in the manuscript Horticulturae-1569764 authors evaluated the relationship between endogenous ethylene production and firmness during ripening and cold storage of raspberry fruit. Fruit were treated with ethylene (1000 ppm) and ethylene perception inhibitor 1-methyl cyclopropene (1-MCP, 1600 ppm) and physiological and quality parameters were evaluated during ripening at 10 and 0 ºC. In general, the manuscript provides some interesting results, showing that ethylene production in whole fruit was negatively correlated to firmness loss during storage at 10 ºC but not at 2 ºC. Thus, it could be suitable for publication in Horticulturae, although the following minor comments should be considered:

- Line 25: Considerer changing "in vitro" assays to storage at 10 and 0 ºC, here and along the whole manuscript.

-Line 95: Should it be cannot instead of can?

- Line 228: Without differences among treatments?

- Line 336: Check this sentence because metabolic activity was also maintained at 0ºC and

As the reviewer suggested, all suggestions were included in the new version of the manuscript.

The authors thank the Reviewer comments