Discovering Two New Viruses Infecting a Common Plant-Damaging Fungus

Jenn Hoskins
9th May, 2024

Discovering Two New Viruses Infecting a Common Plant-Damaging Fungus

Image Source: Natural Science News, 2024

Key Findings

  • Researchers in Pakistan found two new viruses that infect the grey mould fungus on strawberries
  • These viruses make the fungus less harmful, reducing its ability to cause disease
  • This discovery could lead to eco-friendly ways to protect crops without using chemical fungicides
Botrytis cinerea, the fungus responsible for the grey mould disease in strawberries, is a significant agricultural problem, causing losses during cultivation, storage, and transport. Despite various control methods, including fungicides, the disease remains a challenge for farmers. However, a recent study conducted by the National University of Sciences and Technology (NUST) in Pakistan has shed light on a promising biological approach to managing this pathogen[1]. The study focused on mycoviruses, which are viruses that infect fungi. Prior research has shown that mycoviruses can sometimes reduce the virulence of their fungal hosts—a phenomenon known as hypovirulence[2][3]. This characteristic has potential for biological control strategies, where a less harmful virus-infected fungus could be used to outcompete the more virulent, disease-causing forms. In the NUST study, researchers discovered two new fusariviruses, named Botrytis cinerea fusarivirus 9 (BcFV9) and Botrytis cinerea fusarivirus 3a (BcFV3a), within a Botrytis cinerea strain from Pakistani strawberry fields. These viruses have single-stranded RNA genomes, with two distinct open reading frames (ORFs). One ORF encodes a polyprotein that includes an RNA-dependent RNA polymerase (RdRP) domain and a helicase domain—both essential for the replication of the virus's RNA. The other ORF codes for a protein of unknown function. The discovery of these fusariviruses is particularly interesting given that they belong to the Fusariviridae family, a group with members previously identified in other phytopathogenic fungi[3]. Phylogenetic analysis, which helps scientists understand the evolutionary relationships between organisms, placed BcFV9 and BcFV3a in the genera Alphafusarivirus and Betafusarivirus, respectively. Researchers then transferred the mycoviruses to a compatible strain of B. cinerea to observe the effects. The presence of BcFV9 and BcFV3a in infected strains led to hypovirulence, meaning the fungus was less capable of causing disease. This was demonstrated by smaller lesion sizes on apples used in pathogenicity assays, compared to lesions caused by virus-free strains of the fungus. This research builds on previous studies that have characterized mycoviruses in other fungi[2][3]. For instance, the negative-stranded RNA virus SsNSRV-1 was found to infect the fungus Sclerotinia sclerotiorum and confer hypovirulence[2]. Similarly, Rosellinia necatrix fusarivirus 1 (RnFV1) was identified in the white root rot fungus, although it did not reduce the fungus's virulence[3]. The NUST study expands our understanding of the diversity of mycoviruses in B. cinerea and their potential for biological control. The findings offer a glimmer of hope for managing grey mould in strawberries and potentially other crops affected by B. cinerea. If these mycoviruses can be harnessed effectively, they could serve as an eco-friendly alternative to chemical fungicides, which are often costly and can have environmental drawbacks. In conclusion, the research from NUST provides valuable insights into the genetic makeup and functional roles of mycoviruses in B. cinerea. It also opens the door to further exploration of how these viruses can be used in agricultural settings to control fungal pathogens, thereby reducing crop losses and contributing to sustainable farming practices.

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References

Main Study

1) Characterization of two novel fusariviruses co-infecting a single isolate of phytopathogenic fungus Botrytis cinerea.

Published 8th May, 2024

https://doi.org/10.1007/s11262-024-02073-8

Related Studies

2) Fungal negative-stranded RNA virus that is related to bornaviruses and nyaviruses.

https://doi.org/10.1073/pnas.1401786111

3) A novel single-stranded RNA virus isolated from a phytopathogenic filamentous fungus, Rosellinia necatrix, with similarity to hypo-like viruses.

https://doi.org/10.3389/fmicb.2014.00360


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