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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #404803
Research Project: Disease Management and Improved Detection Systems for Control of Pathogens of Vegetables and Strawberries

Location: Crop Improvement and Protection Research

Title: Exaggerated plurivory of Macrophomina phaseolina: Accounting for the large host range claim and the shifting of scientific language

Author
item PENNERMAN, KAYLA - Oak Ridge Institute For Science And Education (ORISE)
item DILLA-ERMITA, JADE - University Of California
item Henry, Peter

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2023
Publication Date: 1/1/2024
Citation: Pennerman, K.K., Dilla-Ermita, C.J., Henry, P.M. 2024. Exaggerated plurivory of Macrophomina phaseolina: Accounting for the large host range claim and the shifting of scientific language. Phytopathology. 114(1):119-125. https://doi.org/10.1094/PHYTO-05-23-0154-R.
DOI: https://doi.org/10.1094/PHYTO-05-23-0154-R

Interpretive Summary: The ‘host range’ of a plant pathogen is the list of known plants upon which it can cause disease. An accurate understanding of the host range is essential for all plant pathogens, as it informs models for dispersal and disease management. Macrophomina phaseolina is a fungal plant pathogen that has a broad host range, meaning it can cause disease on many plant species. Many publications state that its host range encompasses more than 500 plant species, but we could not find any citation that supported this claim. In an analysis of all available peer-reviewed publications, we found this claim of 500 hosts was created without any citation. Pre-1970 host range claims were based on a different standard for establishing pathogenicity than is currently accepted. At present we found support for M. phaseolina being a pathogen of 100 hosts and a suspected opportunistic parasite of many others. This work will help future researchers identify plant species that are known to be susceptible to M. phaseolina.

Technical Abstract: Macrophomina phaseolina is a plant pathogenic fungus that is frequently described as having a broad host range encompassing more than 500 species. We noticed that citations provided in support of this statement do not actually demonstrate such a broad host range. To elucidate the true, documented host range of this fungus, we initiated a literature meta-analysis of 889 publications on M. phaseolina since 1913. We discovered the first host range summaries did not require Koch’s postulates or other experimental demonstrations of pathogenicity. Most of the available early host claims were based on tenuous associations between the fungus and symptoms, sometimes without reporting isolation or morphological examination in vitro. These statements apparently led to a pattern of increasingly exaggerated host range claims without support from a primary reference, until the claim that M. phaseolina has 500 hosts became common in the mid 2000s. At present, the scientific community typically requires Koch’s postulates to characterize pathogenicity on a new host. Among all the available literature, we only discovered primary experimental evidence for M. phaseolina’s pathogenicity on 100 hosts; 75 hosts confirmed by Koch’s postulates and 25 hosts with all steps from Koch’s postulates except recovery of the pathogen from symptomatic tissues. This study demonstrates how scientific concepts can change over time and necessitate changes to historic axioms. We propose that the hyperbole surrounding M. phaseolina’s host range has obscured an accurate depiction of its biology.