Elevated Temperatures Negatively Affect Olive Productive Cycle and Oil Quality
Round 1
Reviewer 1 Report
Review manuscript agronomy-1305997
The authors present a review of the latest published results in relation to the effect of high temperatures on the cultivation and development of the olive tree, as well as on the quality of the oils obtained. In my opinion, the section dedicated to oil quality needs a significant improvement.
Comments:
There is a very recent review also published in Agronomy “Mediterranean olive groves under climate change: a review of the future impact and adaptation strategies” by Fraga et al. 2021 (https://doi.org/10.3390/agronomy11010056) whose content could overlap with this manuscript. Authors should check it and include it in the reference list.
In my opinion, the effect of high temperatures on the main olive pest (Verticillium, anthracnose, Bactrocera oleae…) should at least be mentioned in the manuscript. Some information on this topic should be included in sections 2.2 or 2.3.
Lines 261-269 References at the end of the paragraph should be disagreggated and incorporated at specific points in the paragraph.
Line 321 Temperature is undoubtedly an important factor that affects the composition of FA and TAG. But these factors are not the main ones in terms of the quality of olive oil. Indeed, the IOOC establishes a range of oleic, linoleic and linolenic acids in genuine olive oils, but in terms of evaluating the quality of the oil, a significant number of physicochemical and sensory parameters must be considered. https://www.internationaloliveoil.org/wp-content/uploads/2021/07/COI-T15-NC3-REV-16-2021-_ENG.pdf
In this sense, some phrases such as:
Line 324: "The quality of OO is mainly determined by the concentration of the monounsaturated fatty acid, oleic acid ..."
Line 335: “oil quality defined by oleic acid content….
should be rewritten as they are not accurate. It is the free acidity, expressed in% of oleic acid, which has a clear impact on the quality of olive oil. However, there are many different parameters involved in OO that should at least be mentioned in this section. Special attention should be paid to those related to the organoleptic quality of the oil, phenolic and volatile compounds that are critical in the sensory evaluation of oils, which is essential for their classification.
Line 325-329 The sentence is meaningless. Write again.
Line 369 “Oil grown in extreme heat conditions…. Replace with “The oils obtained from olives grown in…”
The early harvesting of olives is an increasingly widespread trend in Mediterranean countries that aims to increase the quality of the oils by using less mature fruits. However, early harvesting, in these countries that have very warm autumns, means harvesting and processing at higher temperatures and this can have clear effects on the quality of the oil. There are numerous publications on the influence of the internal temperature of the fruits at the time of processing and the temperatures maintained during the milling and malaxation steps on OO quality. Authors must include a comment about it.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript entitled “Elevated temperatures negatively affect olive oil production and quality” is well written and very actual and relevant. It focuses on the effects of temperature on olive oil production and quality. Approaching the subject by showing how elevated temperatures can compromise the reproductive phase of olive. The differences between the effects of the temperature in the different olive development phases (winter vs spring vs summer) considering the global climate change that we are facing. As well as the olive oil production and oil quality in these scenarios. The manuscript also presents a brief section of strategies to improve tolerance to high temperature on olive crops. However, the manuscript should be improved to publish.
I would suggest changing ‘climate changes’ by climate change on line 14 (page 1) and line 411 (page 9).
On the manuscript the symbol for Celsius degrees (°C) should be the same in the whole manuscript. Please check it on line 42 (page 1); line 47 (page 2); lines 103, 105, 107, 108, 109, 110, 111, 113, 115, 116, 118, 123 and 124 (page 3); lines 166, 171 and 176 (page 4); 181, 194, 195, 202, 205 and 206 (page 5); lines 248, 251, 252, 270, 271 and 280 (page 6); lines 329, 330 and 334 (page 7); lines 409 and 416 (page 9). Also, in some cases, after the number there is a space and in others there is not. Please make sure that is uniform.
Regarding Figure 1, a. and c. please change the equation to the form of y= mx+b, instead of ‘43.946x – 0.0264y =’ (a.) and ‘136.23x – 0.0794y =’. Also, please choose one form for presenting each graphic, a., b. and c. or A, B, C. The information is repeated.
‘Mango’ and ‘Litchi’ should be written with lowercase letters (line 53, page 2). And ‘Peach’ too (line 114, page 3).
If possible, provide a reference for the sentence: ‘If olive trees are exposed to naturally warm winters (tropics) or artificially warm winters (heated growth rooms), they will not form flowers.’. Line 54 and 55, page 2.
Line 142, page 4: ‘meteorlogical’ instead of meteorological.
Line 157, page 4: ‘Cuevas & Polito, [19]’, the comma should be after the reference number.
Line 177, page 4: please provide a space between ‘inhibitedfruit’.
The authors should carefully address the terms ‘variety’ and ‘cultivar’. It could cause some confusion as stated in the manuscript. In some cases, authors choose to use the term cultivar and, in other cases, variety as the same concept. It should be carefully verified in which cases to use one term or the other. Also, it should be coherent in all the manuscript the use of the terms. For instance, (…) ‘as well as in ʽLeccinoʼ, ʽLevantinkaʼ, and ʽPendolinoʼ varieties [30].’ (line 190, page 5) and ‘Fertilization competence of four pollen donor cultivars (ʽLeccinoʼ, ʽLevantinkaʼ, ʽOblicaʼ,‘ (…) (line 191, page 5).
Line 194, page 5: please remove de space between rates and the dot.
Lines 219 – 230, page 5: I suggest providing an image of the sigmoid growth curve.
Lines 325-329, page 7: The phrase ‘In general, olive oil chemical composition comprises of oleic acid, residing The chemical composition of olive oil is composed mainly of oleic acid which comprises up to 83% of the total, with residual amounts of palmitic acid (C16:0; 7.5–20%), linoleic acid (C18:2; 3.5−21%), stearic acid (C18:0), and linolenic acid (C18:3) [60,61].’ is confusing. Please clarify.
Line 329, page 7: please remove the dash in ‘0.7%/ ̊C−1’ or the superscript ‘−1’.
Line 330, page 7: please add a space ‘16 to32 ̊C’.
Lines 333 and 334, page 7: Please add a comma between period and temperatures or clarify the sentence. It was not very clear.
Line 358, page 8: please add commas between ‘in olive fruit’.
Line 368, page 8: please add the abbreviation ‘IOC’ in brackets after ‘International Olive Council’.
Line 381, page 8: please change ‘characterised’ by characterized.
Line 413, page 9: please remove ‘with’.
Figure 3: can you provide an image with a larger font size? The image letters are tiny.
Please write species name in italics: ‘Litchi chinensis’ (line 482, page 11); ‘Olea europaea’ (line 486, page 11; lines 521 and 539, page 12; lines 547, 550, 553, 587 and 590, page 13; lines 605, 608, 611, 622, 632, 644 and 647, page 14; and line 653, page 15).
Please provide, if possible, the DOI for the references: 3, 7, 38, 39, 42, 43, 49, 52, 55, 57, 59 and 60.
Author Response
See attached file
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript “Elevated temperatures negatively affect olive oil production and quality”
focuses on a very current and extremely important issue that affects the olive oil sector, in terms of the quantity of olive oil production as well as its quality.
however, some weaknesses were found. first of all is the title, it's not appropriate. The article focuses on the effect of high temperatures on the entire reproductive cycle and not just on the synthesis of olive oil and its quality as a title at first glance makes us think.
Specific comments to the manuscript:
Line 30 and line 261: ….The fruits accumulate oil from June to November: I think is more correct to say that: fruits accumulate oil after pit hardening phase, by in large , from July to November (see the works of Lopez-Bernal et al. 2021 doi.org/10.1016/j.eja.2020.126206)
line 261 : the same comments as line 30. “Oil accumulation in olive fruits is known to begin in June and to last until mid- October. It then slows down during November – December”. This sentence needs a reference. see the works of Lopez-Bernal et al. 2021 doi.org/10.1016/j.eja.2020.126206)
Lines 40-43: “When temperature elevation was calculated for the different seasons ( win-40 ter defined as Dec-Jan, Mar-Apr as spring, and Jul-Aug as summer) a linear trend of al-41 most 2 °C increase was demonstrated for summer, and 0.5 °C increase for winter and spring, over the last 20 years
(Figure 1)” Authors refer to maximum, minimum or mean temperature? Please clarify.
In figure 1 linear equation in figure A and C for minimum temperature is not correct.
Line 43-44: the objective must be clear defined. What is the main goal of this paper? Study the effect of temperature elevation on each phenological phase of olive vegetative and reproductive cycle?
Line 142: meteorlogical, rewrite as meteorological
Line 248: 25 °C was defined as the ambient temperature optimal for olive fruit production of the ‘Arauco’ cultivar [51]. Is it a mean temperature? Rewrite as: For the ‘Arauco’ cultivar, 25 °C was defined as the ambient temperature optimal for olive fruit production.
Lines 264-269: “During this period, the drupe passes through four developmental stages: 0-2 weeks after flowering (WAF) is characterised by ovary growth through cell division. From 2-6 WAF the drupe grows by cell expansion. At 6–16 WAF, cells continue to expand as lipids are stored in oil bodies in the mesocarpal cells. 16–20 WAF is the last stage when epicarp colouration begins and the fruit peel begins to turn purple due to intense anthocyanin deposition in the cell vacuoles. At harvest, oil droplets occupy about 80% of the cell volume [42,50,52-54]”. I don´t agree with authors, especially with this statement: From 2-6 WAF the drupe grows by cell expansion. The initial growth is mainly due to cell division.
Once again I don´t agree with this statement “At 6–16 WAF, cells continue to expand as lipids are stored in oil bodies in the mesocarpal cells.” Oil biosynthesis begin after pit hardening period, authors forget pit formation phase. Authors Please revise the literature and rewrite the text from line 264 to 269.
Line 271: “An increase of 7˚C above the control had a permanent negative…” what is the control?
Line 274. “Elevated temperatures promote vegetative growth but negatively affect oil production”. What do the authors mean by high temperatures? What is the threshold? vegetative growth is impaired at temperatures above 28oC. Please clarify this idea.
Line 288: “Thermal amplitude was found to have in inverse association with oil accumulation, but a positive curvilinear…” authors should clarify the idea, they are low or high thermal amplitudes?
Line 290-300: “Oil quality, which can be measured by high oleic acid (C18:1) 290 levels and/or low linoleic acid (C18:2) levels, showed a positive correlation with oleic acid levels and negative association with linoleic acid levels. In other words, high temperature amplitude had a positive effect on oil quality [51]. No significant association with mean maximum temperature was found which is a crucial point in defining the relevant temperature correlated with those changes. Minimum temperature, on the other hand, had a strong negative effect on oil quality [51], suggesting that attainment of high quality oil requires somewhat elevated threshold temperatures. These results [51] suggest that recording spells of high temperatures alone does not reflect the complex conditions affecting fruit yield, oil content and oil quality in olives. Minimum temperatures and thermal amplitude must also be considered.” This text should be moved to the section 3.2. Olive oil quality under warmer summers as brief introduction
3.2. Olive oil quality under warmer summers: this section is very confusing, the ideas are jumbled and often repeated. Must be rewritten in its entirety. first they must define which are the main chemical compounds that contribute to the quality of the oil and only then explore the influence of the oil temperature
Line 323: “… of fruit colour change, i.e., July and August [60].” Authors should check de literature revised. September and October temperatures are most important than July and August temperatures
Line 325 to 326 “In general, olive oil chemical composition comprises of oleic acid, residing The chemical composition of olive oil is composed…”the text is confusing, please rewrite
Lines 330 to 332: “High temperatures during oil accumulation negatively affected olive oil yield and quality in warm regions, particularly if the high-temperature event occurs early in fruit development process [29,30].” This text should be moved to the section 3.1. Oil accumulation under warmer summers. Authors must explain the reason for this observation. Moreover, “ early in fruit development process” means fruit division?
Line 344 to 349: “It is recognized that excess irrigation during fruit development results in lower phenolic concentrations, possibly due to changes in the biosynthetic and catabolic polyphenol pathways in the olive fruit [66-70]. In this respect also, a genotype variability was noted. For example, the ’Souri’ variety showed no significant decrease in polyphenol level under high temperature conditions, thus suggesting that some cultivars may be relatively more tolerant to high temperatures [50].” Is out of the scope of the paper. This manuscript focus on the effect of elevated temperatures on oil quality. Irrigation and water availability are others factors sometimes associated to elevated temperatures. To clarify the effect of water deficit in phenolic compounds see for example the work of Machado et al. 2013 (doi.org/10.1016/j.foodres.2012.12.056)
Line 401: Complimentary, the correct is Complementary
Author Response
See attached file
Author Response File: Author Response.docx
Reviewer 4 Report
In this review article, the authors reviewed how elevated temperatures negatively affect olive oil production and quality. Overall, the authors prepared a nice and attractive review while addressing several questions with vital examples. However, there are several long paragraphs without providing related citations. Some of the main comments are:
- Please add the abstract in the main manuscript file.
- Line 12-22, the first 3 lines need a suitable reference. However, the other sentences should be transferred end of the introduction to highlight the importance and objectives of the review.
- Line 31-43, there are no supporting references. Every powerful statement deserved to have a strong reference.
- Figure 1, please provide the source of this information.
- In the introduction, please define the threshold temperature for olive production. How temperature variation affects olive physiological, biochemical, and molecular mechanisms, briefly.
- Line 63-72, every solid statement needs supportive references. Would you please not leave long paragraphs without adding citations? The authors can repeat the same citation several times, wherever it is needed.
- Section 2.1, please divide the text into short paragraphs according to the content for more clarity. Do not mix different themes in a long paragraph. Thus, please divide them into different short paragraphs.
- There are several long paragraphs without any citations. Please carefully check the entire text and add supporting references wherever needed.
- Section 4 is quite superficial. The authors need to provide some more evidence made over the past few years. As I can see, there are several important studies performed using different omics platforms for olive crop/oil improvement.
Author Response
See attached file
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
I´m satisfied with the corretions.
Reviewer 4 Report
The authors have responded satisfactorily to my comments, and now the manuscript can be accepted in its revised form.
Congratulations!
Line 17, the scientific name should be in italic.
