Field Screening of Lentil (Lens culinaris) for High-Temperature Tolerance

Round 1

Reviewer 1 Report

This is a nicely written paper; however, more explanation is needed on certain points as outlined below:

Line 24: take out ‘ Taken together’ from the sentence.

Line 121: You already defined trial one (2014) and trial two (2015) here, however, you keep on repeating this throughout the document.  You can refer this either as trial one and two or 2014 trial and 2015 trial.

You have used different number of landraces and cultivars in both years. But you have not given explanation on why they were different. Also, I believe many of them were in common, but you have not said how many were common on both years. This information is needed.

Line 447: Should it be 5c instead of 5e?

Line 455: You mention 22 lentil genotypes were used in both years. This can’t be true as you used 81 in total (line 470).  Did you test 22 separately? There is no mention of it in the method section. If not tested separately, rephrase it differently.

 Line 478:  You mention in 2015, an additional 13 lines were identified. Does it include those identified in 2014? It is suggested that you should write whether those lines identified in 2014 were also identified in 2015. If not how many were in common at least and if the results were different on both years, this need to be explained with why they were so.

 Line 484-486: You noted the identification of only one high temperature tolerant variety in Australia. It would be good to describe/speculate why other varieties developed so far were not high temperature tolerant.

Line 497-498:  You again mention 22 genotypes tested across both years. This is not clear where did these lines come from. Were there only 22 lines common in both years from the entire set of germplasm? This part is poorly described and causing confusion. You would have tested at least 10-15 cultivars for which there would have been enough seed availability!

 Line 593: You identified 6 lentil genotypes that might have HT tolerance. Please list them as they are not too many for readers’ benefits. Also how do they differ from the so called 22 genotypes?

No comments

Author Response

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Reviewer 2 Report

This study seems to be an attempt to identify a method for field screening of lentil germplasm for tolerance to heat - both a technique and the stress indices that might be most useful. This was a 2-season study of 22 lentil lines plus a few extra lines in one or other year. The first year only had 2 replications. For a trait as influenced by the environment as yield this seems like insufficient data to identify significant consistent differences. To add stress of 2 different types (heat and lower light) compounds the environmental interaction with yield. Indeed, in the conclusion it was mentioned that the need to use a single row (rather than full yield plots) would suggest the need for additional replicates. I feel like there is insignificant replication to really draw any meaningful conclusions about any lines in particular. I wonder if less of an emphasis on the actual genotypes and their individual results is in order and the real story is in the pros and cons of this method and the the indices when trying to identify germplasm efficiently for further breeding efforts.

Some of the paragraphs had leaps in logic that I struggled with.

I have difficulty believing that dropping PAR by almost 40% is not having an impact on photosynthesis but if this is indeed the case (as gets cited in line 525) it is not not affecting other things. The fact that the phenology was delayed strongly suggests that yield will be affected too. So in fact two different stresses are being compared.

I like that the study was done under field conditions rather than trying to simulate HT in a controlled environment (artificial) and appreciate that however one tries to impose or mitigate the stress to have both a HT and 'normal' environment there will be risks. This is seen in the fact that the second year was more stressful in general so both treatments suffered. I feel the study needs additional seasons with the same set of genotypes to really get a handle on which are truly better performing. This is reinforced by the observation that STI and HTTI "had poor agreement across years" (line 512).

Specific comments:

The paragraph starting on line 319 does not seem to make sense to me. Perhaps it is the way it is worded but it seems to me the correlation being tested should be between the heat load and the index data not the grain yield directly.

line 343 - what are the units?

line 344/5 - why would you expect grain size to go up under stress?

Figure 3 - why bother with this figure and not just the one with the different indices? This one is clearly confounded by the genetic yield potential of the different genotypes so is difficult to interpret.

line 470 - only 22 genotypes were assessed over 2 years, not 81.

line 452 - hastened development relative to what? between the treatments? if so then you have heat and reduced PAR at play. If you mean relative to planting at the usual time for lentil then you have temperature and photoperiod at play - depending on the genotype some are more sensitive than others so the number 1199°C.d should be taken under advisement (see Wright et al. 2020. Plants, People, Planet). Also, long days and higher temperatures tend to reduce the differences in phenology among genotypes.

Be careful when suggesting that lines coming from hot places like Syria will be more heat tolerant. Your trials were grown in your summer and exposed to >30C, whereas lentils are more typically grown in those areas during their winter to escape such high temperatures.

Table A1 - dropping AGG from the names of the genotypes is not ideal - it leads to confusion in subsequent years when people lose the context of the table and add PI or IG to the names b/c they know it needs something but can't remember what. Which ones were tested in both years?

Tables A2 & 3 - for completeness, should also put the units for the data columns in at the top of each, not just in the table title.

Author Response

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Reviewer 3 Report

Comments to the Authors

The manuscript entitled “Field screening of lentil (Lens culinaris) for high temperature tolerance” explains the high temperature tolerance in the current era of climate change. The authors have evaluated set of diversely originated lentil accessions for high temperature and identified the best performing line(s) using stress indices including novel high temperature tolerance index. However, the following queries should be answered before acceptance of the manuscript.  

For field screening, the authors considered flowering stage/reproductive stage for high temperature tolerance. The title of the manuscript is very general. Accordingly, the suggested manuscript title is “Identification of best performing lentil (Lens culinaris) genotypes for reproductive stage high temperature tolerance based on stress indices”

The authors field evaluated 49 genotypes in 2014 and 54 genotypes in 2015. It is not clear why they have not evaluated all the 81 lines together during 2014 and 2015.

The genotypes names should be mentioned uniformly throughout the manuscript including tables and figures.

It is very much essential to mention the common genotypes best performing during both the seasons in the abstract.

The weather conditions during entire growth seasons during both the seasons should be provided as supplementary data and should be mentioned in the material and methods section.

While taking phenotypic data, the authors concentrated only on the yield trait along with biological yield. It is very much essential to have the yield component traits like plant height and 1000-seed weight. If the data available, should be provided.

It is not clear, how the authors have noted the phenotypic data on yield related traits.

The number of days required for flowering varied significantly among the genotypes, how the authors managed to impose the partial heat stress uniformly for all the genotypes?

 Minor editing of English language required.

Author Response

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