Variation in Tuber Dry Matter Content and Starch Pasting Properties of White Guinea Yam (Dioscorea rotundata) Genotypes Grown in Three Agroecologies of NIGERIA

Round 1

Reviewer 1 Report

The article agronomy-1363168 is clearly written and it describes high quality research on Dioscorea rotundata. Yam is an important crop plant in West Africa and the fact that its average yield has decreased over the last 30 years while its area of cultivation grew dramatically, is affecting negatively food and ecosystem safety in the region. The described study may be of use for yam breeders and through genetic improvement bring better yields in the future. While the authors focused on comparison of 20 yam genotypes grown in three environments in regard to their tuber dry matter content and starch properties, two essential traits are missing in the analyses: tuber yield and starch yield. A post-hoc analysis showing the significance of the differences between tested genotypes in different measured parameters should also be added.

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Reviewer 2 Report

Manuscript Number: agronomy-1363168

Title: Variation in tuber dry matter content and starch pasting properties of white Guinea yam (Dioscorea rotundata) genotypes grown in three agroecologies of Nigeria

Description: The authors evaluated the effects of 18 genotypes (G), three different growing locations (L) in Nigeria, and the G×L interaction on the quality of white Guinea yam (Dioscorea rotundata Poir.). The tubers' quality was determined gravimetrically (Tuber dry matter). Then, starch was isolated from tubers, and Rapid ViscoAnalyzer was used to obtain the pasting properties of starch. Two white yam landraces were used as controls. Different statistical analyses were carried out to choose the best genotypes for breeding purposes. The research is novel and very likely to have a significant impact in this field of knowledge. The statistical analysis is a significant strength of the manuscript; however, the methodology section's description could be improved. To better understand the manuscript, it is necessary to clear the discussions of certain parts of the writing. Below are some areas for improvement. 

Major Comments

1. The pasting properties parameters of starch represent the gelatinization and reordering of amylose and amylopectin leached out of the granule during a thermal event, in the presence of an excess of water, to form a paste. These parameters can be influenced by factors like the plant source (variety); starch purity, granule size and shape, amylose, proteins, lipids, and fiber contents; amylopectin's chain length distribution, the interaction between the components present in the starch. Etc. (1). the above information is used to establish the following questions:
   • In the material section, the authors mentioned during the yam starch isolation procedure that they used only a sieve with a mesh size of 125 um. Nevertheless, Yam starch has been reported to have medium-size granules, approximately 40-55 um (2). thought this mesh not only was starch sieved, but small protein and/ or fiber molecules formed during wet grinding could be dragged to the recipient's bottom by starch granules that have a higher weight, and since no additional washing procedure was performed after the supernatant was discharged. For example, resuspension of sedimented particles in new distilled or purified water. Therefore, could it be possible that the starch samples contain soluble fiber or protein from yam tuber?
   • In the starch isolation procedure, it is established that tap water was used for the wet grinding; how is the water hardness in the laboratory where the isolation of starch was carried out? Could it be possible that some traces of soluble salt from the tap water were kept in the starch after the isolation procedure?

2.- The introduction section mentioned a popular dish prepared with yam ( pounded yam), prepared with the complete tuber. Why did the authors choose to investigate the pasting properties on starch instead of flours?

3.- The introduction could be improved if some information about why it is essential to determine the dry matter of tuber for the breeding of yams tubers. Besides, some information about the statistical analysis used in the breeding of crops could be added.

4.- In Table 1, the soil attributes are declared; why are these techniques not mentioned in the material section?

5.- Instead of using the location names: Abuja, Ibadan, and Ubiaja. Could it be possible to use a nomenclature that could be easier associated with the agroecology parameters, for example: for Ubija use Rain Forest (RF), for Ibadan Forest-Savanna Transition (FST), and Abuja just Southern Guinea Savanna (SGS). 

6.- Could the authors explain how quality parameters found in the best yam genotypes can be used in different food or technological applications?

Reference

1.- https://doi.org/10.1016/j.lwt.2021.111843

2.- https://doi.org/10.1016/j.anres.2018.05.011

Minor Comments

In line 49, chance for

In line 64, add a hyphen between high-temperature

In line 80, change for

In line 84, , rephrase it for. <Therefore, it is important>

In line 88, delete comma: when, and how,

In line 108, add the word soil next to Abuja:

In line 171, delete the word gel, RVA analysis uses as the lowest temperature 50 °C, in this temperature starch only can exist as a paste. 

In line 189, which are the genetic parameter used?

In lines, 190-191, change the word for

In lines 316-317, The sentence , the idea is unclear: what are the specific atmospheric composition and which are the rice functions? 

In line 266: there was no mention the Tukey's HSD test in the data analysis.

Author Response

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Reviewer 3 Report

The article "Variation in tuber dry matter content and starch pasting properties of white Guinea yam (Dioscorea rotundata) genotypes  grown in three agroecologies of Nigeria" is well written and the data obtained in the study can be useful for the goals described in the introduction. The statistical analyses is well performed and results are clearly presented. Some minor modifications are reported in the file.

Comments for author File: Comments.pdf

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Round 2

Reviewer 2 Report

Manuscript Number: agronomy-1363168

Title: Variation in tuber dry matter content and starch pasting properties of white Guinea yam (Dioscorea rotundata) genotypes grown in three agroecologies of Nigeria

The authors attended to most of the comments made during the first revision. However, there is only one statement that needs to be clarified.

In line 199, authors stated

while in lines 444-446, authors stated 

Both sentences are contradictory, but the first statement is correct (line 199). 

It is generally accepted that the increase in viscosity observed during heating starch in water in a Rapid Visco-Analyzer (RVA) is mainly contributed by the swollen granules and the breakdown of gelatinized starch granules causes the breakdown of viscosity. Therefore, differences in the breakdown viscosity are related to the rigidity/fragility of the swollen granules. (1)

According to the literature, different factors can affect breakdown viscosity; for example, the amylose-lipid complexes in normal starches, such as normal maize, normal rice, wheat, and barley, caused an increase in pasting temperature and increased resistance to shear-thinning of starch pastes. With a minor breakdown in viscosity, it is plausible that the very long branch-chains of amylopectin mimic amylose to form helical complexes with lipids and intertwine with other branch chains to hold the integrity of starch granules during heating and shearing (2)

Reference

1.- https://doi.org/10.1006/jcrs.2001.0374.

2.- https://doi.org/10.1094/CCHEM.1999.76.5.629

If cassava starch has a bigger value for breakdown viscosity, then cassava starch is more resistant to heating and shearing than TDr1100837. Please explain thismm

Author Response

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