Year-Long Assessment of Soil Nematode Diversity and Root Inhibition-Indicator Nematode Genera in Rice Fields

Round 1

Reviewer 1 Report

The paper purports to be an original article on the soil nematode communities in rice fields. This article is a manuscript that summarizes on the current state of understanding on the soil nematode diversity and root inhibition-indicator nematode genera in rice fields in India. This review article is within the scope of this journal “Biology” as it compiles information on the abundance, frequency, density and diversity of nematodes of the topsoil of the rice fields in three seasons of a year. The theme of this article is interesting, and potentially relevant within this research field. The introduction, materials and methods, results, discussion and conclusion sections are appropriate (however some sections could be improve) and also they have well-thought-out structure. In addition, this paper is well organized, and clearly written in scientific English.

I have the following comments and edits:

P1-L39. Incongruous data “…genera like Rhabdolaimus, Diplogaster, and Rhabditis…”. Rhabdolaimus is not in the list Table 2 (Table 2. The prominence and relative prominence values of the identified soil nematode genera with respective c-p values in the different seasons of the rice fields).

P1-L41. In my opinion, you could add some keywords such as soil nematode community and/or paddy.

P2-53-58. Part of this first paragraph in the introduction section is not clear. These sentences should be checked and rewrote “The significant economically important …….M. graminicola can cause severe loss to the rice fields [5, 8]”.

P2-54. For the first mention of a species in a scientific paper, the authorities are generally given in full. The authority given is the person who published the name. Please check all text.

P4-99. Section: Study sites and sampling methods. In my opinion, you could include information on what were the crops for the last years in the study area.

P5-139. Section: Nematode extraction from the soil samples ”.. with mesh sieve of 833, 74, and 43 μm aperture…”. Why did you use a sieve 43 μm aperture?. EPPO recommend using a sieve with 38 um of aperture by detecting of Meloidogyne spp (Bulletin OEPP/EPPO Bulletin (2013) 43 (3), 471–495).

P5-148. Section: Nematode extraction from the root samples. You must include information on the g of root used.

P5-154. Section: Identification of nematode genera. You must include information on the keys or pictures used to identify at the genus level.  

P6-206. Part of this first sentence in the result section is not clear “…The variation of soil (pH, moisture, nitrogen, and carbon content of the soil) and nematode diversity (density, frequency, and abundance of soil nematodes) measures …”.

P8. Figure 3. To replace “number of nematodes/50 ml of suspension” by “number of nematodes/200 g of soil”

P8. Figure 4. To replace “number of nematodes/50 ml of suspension” by “number of nematodes/200 g of soil”

P11. Table 2. To add unit of the relative prominence values.

P14. Figure 8. To replace figure 8d and 8e. Figure 8d: Symptoms are not clearly visible. Figure 8e: “and (e) Lesion formation by root-nematodes”. Who cause these symptoms in the root?.

P14. Table 3. To add unit if it is needed.

P16-394. Section Discussion. To check relevant bibliography references on this topic and add in the discussion. For example: Daniil I. Korobushkin, Konstantin O. Butenko, Konstantin B. Gongalsky, Ruslan A. Saifutdinov, Andrey S. Zaitsev, Soil nematode communities in temperate rice-growing systems, European Journal of Soil Biology, Volume 93, 2019, 103099, ISSN 1164-5563.

P16-394. To check this information. “The three nematode infections (root-knot, cyst, and lesion formation).” Who cause these symptoms “lesion formation“ in the root?. Please, to add reference bibliography.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Biology – 1952229-peer-review-v1

Year-Long Assessment of Soil Nematode Diversity and Root

Inhibition-Indicator Nematode Genera in Rice Fields

The manuscript shows the results of a study on the assessment of plant-parasitic and free-living nematodes in soils cultivated with rice during three seasons, and tries to correlate populational fluctuations with soil factors along with seasons year around.

In my view, although the study brings contributions to agriculture, a few points of the work deserve critical attention.

The text, tables and figures are mostly clear and properly presented.

Simple Summary

Page 1

Lines 19 and 21 – Please correct ... plant-parasite nematodes …to: plant-parasitic nematodes

INTRODUCTION

Page 3

Line 61 – Please correct ... tropic levels …to: trophic levels

Line 71 – Please consider replacing nematodes love soil with slightly acidic pH… to: nematodes prefer soil with slightly acidic pH…

Line 93 – Please replace …soil characters …to: … soil characteristics…

MATERIALS AND METHODS

Page 4

Line 103 – Please complete if latitude North or South and longitude East or West.

Page 5

Line 140 –  There is problem with sample measurement that reflects to the whole nematode count. Since each sample has a different water content, the best choice is to measure soil sample as volume (milliliter (ml) or cubic centimeter (cc)), unless if moisture correction is applied to each sample, therefore, the result could be given as number of nematodes per gram of soil, or per 100 g of soil.  I do not agree with the way in which the results were given as number of nematodes per 50 ml of suspension, regardless the volume of soil. As it was done, soil samples collected in the same place had different volume for each season, since soil moisture may be different for the same soil in different seasons.

Lines 190/191 – The following sentence is out of context, since in the paragraph there is no formula with the variable “N”…. The N denotes the number of samples in which the genus was present……

RESULTS

Page 9Ditl

Figure 5 –  In the graphic legend, please correct  Longidorous to Longidorus

Line 271 – please correct  Longidorous to Longidorus

Pages 10/11

Figure 6 –  In the graphic legend, please correct  Longidorous to Longidorus

Line 288  and in Table 2 the nematodes in the genus Ditylenchus is placed among plant-parasitic nematodes. Unless the specimens were identified as belonging to plant-parasitic species as D. dipsaci and D. angustus, otherwise the majority Ditylenchus specimens recovered from soil are fungal feeders, therefore I strongly recommend to change Ditylenchus status from plant-parasite to fungivores. It implies in redoing most the analyses.  

Page 11

Table 2 – please correct  Longidorous to Longidorus

Table 2 – So far as I know, nematodes belonging to the genus Panagrolaimus are bacterial feeders (Yeates et al., 1993). Therefore, I strongly recommend moving from predatory to bacteriovores. It also implies in redoing the analyses.

Page 13

Line 326 – Please correct …. whereas Xiphinema (0.58) have the least. To: whereas Xiphinema (0.58) has the least.

Figure 8–  I strongly recommend  to replace Figures 8d and 8e, since the arrows did no point correctly to a cyst, nor to root lesion, respectively.

Table 3 – table heading – I suggest changing … plant-parasite nematode…. To : plant-parasitic nematode….

Lines 349/350 and last row of Table 4 – It seams there is a misunderstanding in the calculation of ppi (plant parasite index). PPI must be higher or equal 2, since there is no plant-parasitic nematodes with c-p value below 2. For ppi calculation, consider only the plant-parasitic nematode in the sample. For example, if there are a total of 100 nematodes in the sample, but only 10 plant parasites, consider these 10 nematodes as 100%, and forget the 90 free-living. Therefore, I strongly recommend redoing the analyses in the correct way.

DISCUSSION

Page 14

Line 379 – The decrease in nematode populations during summer… It needs an explanation which nematode trophic groups decreased in summer. Looking at figure 3b, only free-living decreased during summer.

Lines 381/382 – Please correct: …. PPNs constituted the highest genera and abundance… to: …PPNs constituted the highest genera in abundance…

Page 15

Line 386– Please correct ….Longidorous to: ….Longidorus…

Lines 392/393 – please change … because of their persistence … to:  … due to their persistence….

Lines 399-401 The following comment seams to be speculative, since toot inhibitions was not evaluated in this study: …. These results suggest that the frequency and density of Hirschmanniella, Meloidogyne, and Heterodera will function as the best indicators for nematode inhibition rate in the rice roots….

Lines 413-415 – As previously recommended, a correct calculation of ppi, may bring different results.

Lines 420/421 – Please change … which is because of the dominance of bacterial feeders. To: … which is due to the dominance of bacterial feeders.

Author Response

Please see the attachment

Author Response File: Author Response.docx