Impact of inoculum density of Fusarium oxysporum f. sp. zingiberi on symptomatic appearances and yield of ginger (Zingiber officinale Roscoe)

  1. Andrea Matthews
  2. Sharan P. T. Muthukumar
  3. Sharon Hamill
  4. Elizabeth A. B. Aitken
  5. Andrew Chen

Reviewed by

Read the full article See related articles

Discuss this preprint

Start a discussion What are Sciety discussions?

Listed in

This article is not in any list yet, why not save it to one of your lists.
Log in to save this article

Abstract

Ginger ( Zingiber officinale Roscoe) is an important horticultural crop valued for its medicinal and culinary properties. Fusarium yellows, caused by the ascomycete fungus Fusarium oxysporum f. sp. zingiberi ( Foz ), is a devastating soil-borne disease of ginger. It has curtailed ginger production in Australia and around the world, leading to significant economic losses. An integrated approach is required to manage soil-borne diseases such as those caused by Foz . However, little is known about the influence of Foz inoculum on disease severity. This study aimed to establish a minimum threshold level of spores per gram of soil required for plant infection and to develop and evaluate a pot inoculation method for screening large numbers of plants in a controlled environment. To achieve this, the dominant Australian ginger cultivar Canton was inoculated with 10 1 , 10 3 , 10 5 , 10 6 and 10 7 microconidia g −1 soil. The inoculum density was positively associated with leaf and stem yellows, and rhizome discolouration, and negatively associated with root length and rhizome weight. The lowest threshold required for plant infection was 10 1 microconidia g −1 soil, which may provide an important basis for outbreaks of Foz in the field. This finding adds significantly to our knowledge of the impact of soil health on ginger production, thereby contributing to the integrated management of Foz . When used at a high dose, this method can facilitate reliable and accurate screening of Foz -susceptible ginger genotypes in a controlled environment.

Article activity feed

  1. Version published to 10.1099/acmi.0.000605.v3 on Access Microbiology
  2. Access Microbiology

    Thank you for so thoroughly addressing the reviewers comments and giving a point by point rebuttal to each one to make my job easier. I am satisfied that each point raised by the reviewers has been addressed, including the addition of extra MLST data and photographs of the scoring system used for disease manifestation. Thank you to both reviewers for such thorough and constructive reviewers. They have certainly improved the manuscript.

  3. Version published to 10.1099/acmi.0.000605.v2 on Access Microbiology
  4. Access Microbiology

    Comments to Author

    This manuscript determines the infection threshold and dose-associated symptoms of Fusarium oxysporum f. sp. Zingiberi in the ginger cultivar "Canton", which is of importance in Australia. The research objectives are clearly stated, although to be completely met further cultivars would be included in the experimental design. Notwithstanding, the provided methods and results could be of help for applying in other cultivars. Methods are adequately described to reproduce the experiments once the minor suggestions below are implemented. Identification of Foz isolates by molecular methods would be required, at least to confirm the species. Statistical analysis was appropriate. In general, the article is well written and conclusions are sound by the presented results. Below, my suggestions for improvement of the manuscript are found: 1. Methodological rigour, reproducibility and availability of underlying data - In the abstract, authors declare that their research objectives were: i) "to establish a minimum threshold level of spores per gram of soil required for plant infection" (lines 36-37) ii) "to develop and evaluate a pot inoculation method for suitability in genetic studies on Foz resistance" (lines 37-38) In my opinion, i) has been met, but ii) was only partially covered by the experiment, since for that aim, different cultivars with variable resistance to Foz should be included and compared. - Line 83: authors state: "To study the efficacy of Foz infection, we performed a replicated experiment using five different concentrations of Foz microconidia", but indeed it is not indicated if the experiment was replicated and results reproducible. Please, add clarification. - Lines 96-98: authors state that "Formae specialis of these isolates were confirmed to be Fusarium oxysporum f. sp. zingiberi based on their ability to cause Fusarium yellows in ginger pot trials". Why didn't authors complement the identification with a more accurate method to determine whether those isolates are classified as F. oxysporum f. sp. Zingiberi, for example, using molecular markers? It would be required to identify molecularly the isolates at species level. - Lines 100-101: Could authors explain the reason why they mixed 4 four isolates for the inoculum? - Lines 104-105 and rest of manuscript: My suggestion is to use the unit microconidia/mL or microconidia/g of soil, instead of cfu/mL or cfu/g. For the second, it would be required having a probe that the microconidia had the ability to form colonies (for example, by plating diluted inoculum and counting colonies). Please, strict to this unit in the whole text. - Lines 116-120: Please, rewrite these sentences to clarify how soil inoculation was conducted. As it is explained, it seems that pots with soil were inoculated and then mixed with extra 400 g of soil. - Lines 120-122: Please, explain the reason why treatment 107 microconidia/g of soil only had three plants. - Please, clarify if plants were grouped as replicates. 2. Presentation of results - General: use of the term "correlation" (lines 41, 87, 88, 138, 156). Authors use the term "correlation" to reflect association of results and trends for different variables. However, I would suggest avoiding this term, since it could lead to the thought that statistical correlation analyses have been conducted, when it is not the case. Please, rephrase those sentences. - Line 141: Authors use the term "accelerated", when results do not reflect an earlier appearance of symptoms, but an exacerbation of those. Please, change "accelerated" by "exacerbated". - Line 162: The significant reduction in comparison to control is actually observed in 106 cfu/g of soil or higher. Please, correct it. - Figure 2: Please add in caption the number of plants for each treatment, as done in Table 1. 3. Literature analysis or discussion - Line 85: Please, add a reference. - Discussion: Much information about agricultural practises related to ginger are explained, but I miss further discussion on their relation with this study, its importance, and conclusions; mainly focused on the improvements on disease control and management of crop productivity. Also, it would be interesting to discuss limitations of the study, for example: plant variety selection, number of plants, isolate virulence, etc.

    Please rate the manuscript for methodological rigour

    Satisfactory

    Please rate the quality of the presentation and structure of the manuscript

    Good

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  5. Access Microbiology

    The majority of the points raised seem to be easy fixes, but I have selected major revisions as both reviewers highlight that the stated aims have not been fully met by the experimental set up, and this may require either a good rewrite or further experimental work (should the authors wish to go down that road). One point has also been raised about the identification of isolates as Fusarium oxysporum f. sp. zingiberi using disease manifestation rather than accurate molecular techniques, and I am concerned about how robust this method of identification is. Please respond to all reviewers comments below and revise the manuscript accordingly.

  6. Access Microbiology

    Comments to Author

    Lines 1-3: Lowest may refer that 10 cfu/gm soil be the least and there may be a need to run logistic or other growth models to showcase the clearcut point where the threshold is significant. Anything

    Please rate the manuscript for methodological rigour

    Very good

    Please rate the quality of the presentation and structure of the manuscript

    Good

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  7. Version published to 10.1099/acmi.0.000605.v1 on Access Microbiology