A Weak Allele of FASCIATED EAR 2 (FEA2) Increases Maize Kernel Row Number (KRN) and Yield in Elite Maize Hybrids

Round 1

Reviewer 1 Report

This study using a reported QTL Fea2, generated the diverse backcross and selection lines, detected the affection of week allele for breeding. Here still have several questions:

1. LVN10 as the variety with hybrid, commercialized, more demanded variety in Vietnam, this is OK, but how about this variety agronomic trait, such as KRN, PH, EH, KRP, etc? how about compare with other 4 recurrent parents? I think explain this in discussion part is better.
2. Figure 3d, the bands of left group looks like contain more hybrid type (below), and the hybrid type band showed same size and type, I think here should explain the product size and mark the marker size, Or that is impurities?
3. Why here no method mentions about generated process of LVN10 fea2-/-.
4. In this study, only generation of backcross 3 is available, how to confirm the genome background trend to RP?
5. Please care the detail error, such as: Table1, “Kernel row rumber”, etc.

Author Response

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Reviewer 2 Report

Comments and suggestions for the authors:

Trung et al. 2020 introgressed a weak allele of FASCIATED EAR 2, fea2-1328, into the maternal and paternal parents of two Vietnamese elite maize hybrids, with the idea to increase kernel row number and thus total yield. The introgression increased the kernel row number in any background but total seed yield was unaffected. Trung et al. suspected the photosynthetic capacity of the inbreds to be of limiting nature and therefore crossed the parents of the elite hybrid LVN10, both homozygous for the fea2-1328 allele. In the resulting vigorous F1 hybrids (LVN10 – fea2) the KRN was significantly increased, which led to a significant increase in total seed yield by up to 28%.

This study is of importance to the scientific and breeding community. The logic behind the experiment is straightforward and supports the conclusion. The yield trials were performed at different locations and in different seasons and years, which is a powerful point to support the role of the fea2 allele in yield increase. 

Major suggestions:

1. The chapter 3.1 requires more details and statistics to provide the reader with enough evidence. The authors cite Fig. 2 (L. 170) to support their claim, that the mutation in ML10/W22 & BVS36/W22 is recessive and in BL10/W22 & MVS36/W22 semi-dominant, but the legend of Fig.2 clearly states that the number of plants indicated did not reflect the segregation ratio. As a reader, I cannot infer the determination of the degree of zygosity, but have to believe the authors that their random selection was actually random. The number of plants used for measurements differ between genotypes, BL10/W22 seems to be underrepresented. I would suggest providing information about the segregation ratio and also performing simple statistics like a Chi-square test to support any conclusion drawn. The chapter would benefit from more explanation regarding those points.
2. Table 1 is referred to in chapter 3.3 and in chapter 3.4, which makes Table 1 hard to understand while reading the manuscript in chronological order. I suggest splitting Table 1 into two independent tables.
3. Chapter 3.4 describes the most important finding of this manuscript and deserves a little more details. I suggest repeating (I know authors described it in M&M) in one or two sentences how the LVN10-fea2 hybrids were generated. Furthermore there is a discrepancy between Figure 5 and Table 1. Hybrid yield in Ha Noi Spring 20 was significantly increased by 27% in Figure 5, but no significance was indicated in Table 1 with a ratio of 1.27, which likely is just an error.

Smaller suggestions:

2. 106, this is an explanation of the plant material, which could be moved to the preceding chapter 2.1 L. 98
3. 97 & L. 186 both refer to the abbreviation “IL”, but with two different meanings, isogenic line and introgression line. The difference should be clearly pointed out and the abbreviation needs to be unique throughout the manuscript.
4. 179 “dominant” can be dropped
5. 187 & L. 212, please drop the “quite”. Plants were either homogeneous or they were not.
6. 212 & L. 221 & L. 231, please drop “some”, it is not required.
7. 227 Authors claim that KRN was significantly increased in every IL, but it was not in BVS36-IL2 (Table 1)
8. 244 Authors claim that the yield of BVS36-IL1 is significantly increased but their claim is not supported by Table 1 as there is no significance indicated.

Author Response

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Reviewer 3 Report

Dear authors here are listed my specific comments, which can serve you to improve your manuscript

Line 42: it is not only a food crop

Line 45: 1138 million is 1.14 billion?

Line 50: reword “in2creased”

Line 56: use one decimal number

Line 57: tons/ha should be ”t ha^-1”

Line 102: provide GPS coordinates

Introduction lacks information about maize breeding

Paragraph 111-129: present each equation as separate, and provide an explanation about it.

All tables must be self-explanatory. They need to stand alone. Borders are not well presented

Besides Table 1 results are presented well.

Discussion has only 8 references cited in the last paragraph. The authors should do more effort to connect their research with published literature. 

Author Response

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Round 2

Reviewer 2 Report

The authors have taken all of my suggestions into account in a satisfactory manner.

Reviewer 3 Report

N/A