Current Status and Future Prospects of Head Rice Yield

Round 1

Reviewer 1 Report

Seen in the attachment

Comments for author File: Comments.pdf

Author Response

Response to reviewer file

Reviewer 1

Reviewer 1: Change to upper font

Response by the authors: Thanks for your valuable comments, and authors accepted that

head rice yield was changed to ‘Head rice yield’.

Reviewer 1: As the study is focused on rice yield it is better to consider the weight of the grain(Test weight)

Response by the authors: The head rice yield (total amount of whole grain polished white rice of the paddy from which it is derived) is dependent on the grain shape. Grain shape is determined by the length and width of the grain and that determines the grain weight. Therefore, the authors included the QTL of length, width and weight.

In future research papers the authors are testing the effect of weight and related losses associated with any reductions in head rice yield (please stay tuned for coming updates of HRY).

Reviewer 1: change to upper case (Table 2)

Response by the authors: Thanks for your valuable comments the authors accepted that,

‘chromosome’ was changed to ‘Chromosome’.

Reviewer 1: Since the shape of the grain is not only the yielding character, it is better to consider other yield-attributing characters as well

Response by the authors: Thanks for your valuable comment. The authors agreed with the reviewer that grain shape (size and weight) is not only the contributing factor that affects the head rice yields. Therefore, the authors mentioned the other factors including pre-and-post harvest, grain molecular composition, the possible effect of solid and applied nitrogen, and factors beyond the physiological maturity that may affect the yields of head rice. Thus, the genetics of head rice yield was discussed because of the importance of several other traits that need to be included in future studies to map QTL and identify SNPs of head rice yield.

Reviewer 1: change to upper case (Table 3)

Response by the authors: Thanks for your valuable comments the authors accepted that,

‘chromosome’ was changed to ‘Chromosome’.

Reviewer 1: The factors can be better pointed by considering rice crop physiology responsible for chalkiness

Response by the authors: Thanks for your valuable comments the authors accepted that. The authors changed the paragraph into the points considering the rice crop physiology responsible for chalkiness.

Previous version:

Exactly why chalky grains develop has not been fully resolved, but it has been suggested that chalky grains are produced in response to high-temperature stress during grain-filling (Counce, et al., 2005, Lin et al., 2010, Zhou et al., 2015). However, other seasonal conditions such as wetting and drying cycles, are also associated with the development of chalky grains (Zhao and Fitzgerald 2013; Xu et al., 2015). Some studies suggest that loosely packed starch molecules cause chalkiness, possibly due to variations in amylose content (Lisle et al., 2000, Fu and Xue 2010, Wang et al., 2013), while other studies suggest that amylose and chalkiness are negatively correlated (Zhou et al., 2003, Zhou et al., 2015, Lin et al., 2016, Lin et al.,2017). Chalkiness is a highly undesirable trait that promotes grain cracking during milling and reduces head rice yields (Zhou et al., 2015). Environmental factors such as temperature, transpiration rate of canopy and evaporation rate contribute to developing chalkiness. Therefore, future studies are required to investigate which factors; environmental and genetics (in the context of Table 6), contribute to developing the chalky grains and finding the possible link between the rice grain molecular components and chalkiness.

Revised version:

Chalkiness is a highly undesirable trait that favours grain cracking during milling operations (dehusking and polishing), which ultimately reduces head rice yields (Zhou et al.,2015). The reason for the development of chalky grains has not been fully resolved yet (Jin et al., 2023). Therefore, the following points need to be considered where the effect of rice crop physiology coupled with high-temperature stress for chalkiness.

• High-temperature stress during grain-filling (Counce, et al., 2005, Lin et al., 2010, Zhou et al., 2015) was considered a major contributing factor to the development of chalky grains.
• However, other seasonal conditions such as wetting and drying cycles, are also associated with the development of chalky grains (Zhao and Fitzgerald 2013; Xu et al., 2015).
• Previous literature also suggested that loosely packed starch molecules cause chalkiness, possibly due to variations in amylose content (Lisle et al., 2000, Fu and Xue 2010, Wang et al., 2013),
• Other studies suggested that amylose and chalkiness are negatively correlated (Zhou et al.,2003, Zhou et al., 2015, Lin et al., 2016, Lin et al., 2017).
• Environmental factors such as temperature, transpiration rate of canopy and evaporation rate contribute to developing chalkiness. Therefore, future studies are required to investigate which factors; environmental and genetics (in the context of Table 6), contribute to developing the chalky grains and finding the possible link between the rice grain molecular components and chalkiness.

Reviewer 1: Better to address the consequences of moisture stress as well

Response by the authors: Thanks for your valuable comments the authors accepted that. The authors changed the paragraph and addressed the consequences of moisture stress as well.

Previous paragraph

Soil moisture during grain-filling stages in rice (Miah et al., 1996, Yang et al., 2000) and wheat (Yang et al., 2000) may affect the remobilisation of pre-stored carbon and nitrogen assimilates from source (vegetative parts) to sink (grain). Agronomic practices, such as post-anthesis soil drying, may lead to increase carbon partitioning to grains by regulating key plant hormones such as abscisic acid, cytokinins in leaves (Yang et al., 2000, Yang, Zhang et al.,2001, Yang, Zhang et al., 2002, Yang et al., 2003, Yang and Zhang 2006, Zhang et al., 2012) and trans-zeatin-type cytokinins in the roots (Zhang et al., 2010).  Soil drying practice during grain-filling may also upregulate the starch branching and debranching enzymes (SuSase, AGPase, SSS, GBSS, SBE) and genes (SuS2, SuS3, SuS4, AGPS2b, AGPL1, AGPL2, SSSIIb, SSSIIc, GBSSI, GBSSII, SBEI, and SBEIIb (Wang et al., 2015). It is therefore possible that post anthesis soil drying may influence head rice yields by altering carbon partitioning to grains.

Revised version:

Soil moisture showed a considerable effect in altering the grain yield across the cereal crops following grain-filling stages in rice (Miah et al., 1996, Yang et al., 2000) and wheat (Yang et al., 2000). Soil moisture level might affect the source-to-sink relationships where the remobilisation of pre-stored carbon and nitrogen assimilates either increased or decreased from the source (vegetative parts) to the ink (grain) under the soil moisture stress. However, agronomic practices, such as post-anthesis (50% days after flowering) soil drying, do have the potential to increase the amount of carbon partitioning from the flag leaf to grains by regulating key plant hormones such as abscisic acid, cytokinins in leaves (Yang et al., 2000, Yang, Zhang et al., 2001, Yang, Zhang et al., 2002, Yang et al., 2003, Yang and Zhang 2006, Zhang et al., 2012) and trans-zeatin-type cytokinins in the roots (Zhang et al., 2010).  Grain-filling period proved to be the dominant factor that influences head rice yields (Ali et al., 2019b), therefore, soil drying practice during mid and late grain-filling periods upregulated the starch branching and debranching enzymes (SuSase, AGPase, SSS, GBSS, SBE) and genes (SuS2, SuS3, SuS4, AGPS2b, AGPL1, AGPL2, SSSIIb, SSSIIc, GBSSI, GBSSII, SBEI, and SBEIIb (Wang et al., 2015). There is a possibility to investigate the effect of post-anthesis soil drying during the grain filling periods (mid-and-late grain filling) that influence head rice yields by altering carbon partitioning from the flag leaf to developing grains.

Reviewer 1: Preferred to address the role of nitrogen uptake with grain yield and quality.

Response by the authors: Thanks for your valuable comments the authors accepted that. The authors changed the paragraph and addressed the consequences of moisture stress as well.

Previous paragraph:

Nitrogen uptake through the roots and translocation from the shoots to vegetative parts and developing grains determine grain yield and protein contents in the edible grain. Previous literature demonstrated nitrogen fertilizer application typically leads to increasing grain protein content, albeit this is not always the case, and substantial genotype x environmental interactions were observed (Nangju and De Datta 1970, Seetanun and De Datta 1973, Atilio J and Causin 1996, Perez et al., 1996, Leesawatwong et al., 2005, Yang et al., 2013, Arnold et al., 2015, Bryant et al., 2015, Grigg et al., 2015). Also, the remobilization mechanism that demonstrates the partitioning of sources between the flag leaf and developing has been less well studied in retrospect and the importance of nitrogen in terms of rice grain cracking cannot be neglected but has not been extensively studied. However, previously published literature reported nitrogen fertilizer application helped to increase the amount and density of seed storage proteins in the rice grain, and mitigate the risk of chalkiness and grain cracking during milling operations (Perez et al., 1996, Leesawatwong et al., 2005, Grigg et al., 2015)

Revised paragraph:

Nitrogen plays a key role in determining grain yield and protein contents (Grigg et al.,2015). Nitrogen fertilizer application typically leads to increasing grain protein content, albeit this is not always the case, and substantial genotype ´ environment interactions were observed (Nangju and De Datta 1970, Seetanun and De Datta 1973, Atilio J and Causin 1996, Perez et al., 1996, Leesawatwong et al., 2005, Yang et al., 2013, Arnold et al., 2015, Bryant et al.,2015, Grigg et al., 2015). The importance of nitrogen fertilizer application across various growth stages of rice plants (ranging from vegetative growth phases to gametogenesis and grain filling periods) in terms of rice grain cracking has not been extensively studied. However, some field studies reported nitrogen fertilizer application before flowering increased the amount and density of seed storage proteins, and reduced chalkiness, which coincided with reducing grain cracking during milling operations (Perez et al., 1996, Leesawatwong et al.,2005, Grigg et al., 2015)

Reviewer 1: Rice physiology can be accounted in the study for better understanding the heat stress effect on rice

Response by the authors: Thanks for your valuable comments the authors accepted that. The authors changed the paragraph and addressed the consequences of moisture stress as well.

Previous paragraph:

Head rice yield is affected by many factors, including temperature, nitrogen fertiliser application, harvest moisture, storage conditions and paddy moisture contents before milling operations. Among these factors, the temperature is critical because of the predicted changes in day and night-time temperatures expected to arise due to climate change. The association between high temperature and chalkiness, and potential links between chalkiness and grain breakage, suggest that high-temperature stress may increase grain breakage during milling operations. Therefore, future studies are warranted to investigate the potential impact of high day and night temperatures during grain-filling periods. Moreover, applying advanced statistical models such as metaGWAS and CGM-WGP will be required to accelerate the genetic development of head rice yield.

Revised paragraph:

Several factors potentially affect the yields of head rice, including day-nighttime temperatures, nitrogen fertilizer applications across various growth stages including vegetative, reproductive, and grain-filling periods, harvest moisture contents, paddy storage conditions and paddy moisture contents before milling operations. Among these factors, the temperature is critical because of the predicted changes in day and night-time temperatures expected to arise due to climate change. However, the study of rice crop physiology needs to be accounted for a better understanding of the heat stress that affects rice plant yield in terms of grain yields and head rice yields. Moreover, the measure of association is required between high temperature and chalkiness across the different genetic backgrounds including japonica, temperate japonica, indica, aus, aromatic, and wild types) to develop potential links between chalkiness and grain breakage following milling operations (dehusking and polishing operations). Moreover, applying advanced statistical models such as metaGWAS and CGM-WGP will be required to accelerate the genetic development of head rice yield.

Author Response File: Author Response.docx

Reviewer 2 Report

“Current status and future prospects of head rice yield in a warming world”.

This is an interesting topic, but the purpose of this review is not well supported by the whole manuscript. If the authors remain the original topic, I would like to suggest a major revision. Here are the detailed comments:

1.     Line number will help reviewers to give detailed comments, please add line number in the manuscript

2.     The introduction, the author establishes the research background of global warming with a focus on heat stress, but little mention is made of the impact of warming on HRY in this part.

3.     Figures, all figures in this manuscript are cited from other sources, is this permittable by the journals?

4.     Table 2, the first column maybe more useful for other scientists and readers by listing rice cultivars (japonica, indica, hybrid etc.) instead of “crop”

5.     Conclusion and outlooks should be stated as 3, so the structure of this manuscript should be clearer

Author Response

Reviewer 2

Comments and Suggestions for Authors

“Current status and future prospects of head rice yield in a warming world”.

This is an interesting topic, but the purpose of this review is not well supported by the whole manuscript. If the authors remain on the original topic, I would like to suggest a major revision. Here are the detailed comments:

1. Line number will help reviewers to give detailed comments, please add line number in the manuscript

Response by the authors: Thanks for your valuable comments; the authors added the line numbers.

2. The introduction, the author establishes the research background of global warming with a focus on heat stress, but little mention is made of the impact of warming on HRY in this part.

Response by the authors: Thanks for your valuable comments the authors have changed the title of the manuscript.

Previous topic:

Current Status and Future Prospects of Head Rice Yield in a warming world

New Topic:

Current Status and Future Prospects of Head Rice Yield

3. Figures, all figures in this manuscript are cited from other sources, is this permittable by the journals?

Response by the authors: The authors provided the copyrights (-of all figures used in the current review paper) to the editor of the journal when the original manuscript was submitted.

4. Table 2, the first column maybe more useful for other scientists and readers by listing rice cultivars (japonica, indica, hybrid etc.) instead of “crop”

Response by the authors: Thanks for your valuable comments. The previously published literature as mentioned in Table 2 did not clearly state the genetic background (japonica, indica, aus, aromatic etc) of the rice genotypes. Therefore, the authors have included the general terminology ‘Rice’ to avoid any confusion for the reader and the rice community.

5. Conclusion and outlooks should be stated as 3, so the structure of this manuscript should be clearer

Response by the authors: Thanks for your valuable comments the authors have changed the conclusion section to number (3). The authors also rephrased the conclusion section as suggested.

Previous paragraph

Head rice yield is affected by many factors, including temperature, nitrogen fertiliser application, harvest moisture, storage conditions and paddy moisture contents before milling operations. Among these factors, the temperature is critical because of the predicted changes in day and night-time temperatures expected to arise due to climate change. The association between high temperature and chalkiness, and potential links between chalkiness and grain breakage, suggest that high-temperature stress may increase grain breakage during milling operations. Therefore, future studies are warranted to investigate the potential impact of high day and night temperatures during grain-filling periods. Moreover, applying advanced statistical models such as metaGWAS and CGM-WGP will be required to accelerate the genetic development of head rice yield.

Revised paragraph:

Several factors potentially affect the yields of head rice, including day-nighttime temperatures, nitrogen fertilizer applications across various growth stages including vegetative, reproductive, and grain-filling periods, harvest moisture contents, paddy storage conditions and paddy moisture contents before milling operations. Among these factors, the temperature is critical because of the predicted changes in day and night-time temperatures expected to arise due to climate change. However, the study of rice crop physiology needs to be accounted for a better understanding of the heat stress that affects rice plant yield in terms of grain yields and head rice yields. Moreover, the measure of association is required between high temperature and chalkiness across the different genetic backgrounds including japonica, temperate japonica, indica, aus, aromatic, and wild types) to develop potential links between chalkiness and grain breakage following milling operations (dehusking and polishing operations). Moreover, applying advanced statistical models such as metaGWAS and CGM-WGP will be required to accelerate the genetic development of head rice yield.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Prof. Dr. Editor of Agriculture  Journal,

I write you regarding Manuscript Number: agriculture-2262927 entitled "Current Status and Future Prospects of Head Rice Yield in a Warming World " which was submitted to the Agriculture journal.

In this manuscript, the authors reviewed the Current Status and Future Prospects of Head Rice Yield in a Warming World. The manuscript is suitable for publication in Agriculture.

I have gone through this work. My decision is accepted with minor revisions for this work. The reason for that is as follows:

The manuscript deals with the Current Status and Future Prospects of Head Rice Yield in a Warming World.

First: Title: It should change to the following:

1)      Current Status and Future Prospects of Head Rice Yield in Warming World 

Second Abstract, keywords and Introduction:

2) has some minor corrections as in the attached file.

References

Please remove the repeated references. It has some minor corrections as in the attached file.

Thank you for suggesting me as a reviewer for this paper.

with best regards

Comments for author File: Comments.pdf

Author Response

Please see the attached file

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Since the revised version improved the manuscript and most of the comments were answered, I would like to suggest that the editors accept this manuscript with minor revisions.

In the abstract, global warming and heat stress were clarified as study backgrounds, while no related information (other studies on the impacts of warming on HRY) was stated in the introduction. 

Author Response

In the abstract, global warming and heat stress were clarified as study backgrounds. In contrast, no related information (other studies on the impacts of warming on HRY) was stated in the introduction. 

Author's Response: Thanks for your valuable comment. The authors have stated the impact of heat stress on HRY in the Introduction section 

Previous paragraph:

Other factors include grain moisture during harvesting and drying [14], and methods used to dry down the grain/paddy (hot air or infrared drying) [15,16,17] have a critical impact on head rice yield [14]. In addition, seasonal conditions have been linked to higher grain breakage during milling [18,19,20]. High day/night temperatures, especially during gametogenesis and early anthesis, result in substantial grain yield losses [9]. Moreover, heat stress during early and late grain filling periods affects the grain yields and milling outturn [14]. Grain breakage during milling is higher in immature grains [21], and it is, therefore, likely that seasonal conditions affect the uniformity of grain-filling or reduce the number of immature grains at harvest will increase head rice yields.