Table of Contents
The Virome of a Genus: A Look at Known Alternaria Mycoviruses
Last Updated: July 29, 2025
Author Bio: This research summary is based on the doctoral thesis of Wajeeha Shamsi, a researcher from the Atta-ur-Rahman School of Applied Biosciences at the National University of Sciences & Technology (NUST), Islamabad. Her work focuses on the identification and characterization of novel mycoviruses from environmental sources.
Introduction
The genus Alternaria is one of the most common and widespread groups of fungi in the world. Its members are found in soil, on plants, and even in the air we breathe. While many are harmless saprophytes, several species are notorious plant pathogens, causing diseases like leaf spots and blights on a wide range of crops. Just like their hosts, Alternaria mycoviruses are proving to be a diverse and fascinating group. The study of the Alternaria virome—the collection of all viruses that infect this fungal genus—is a rapidly developing field. Based on the detailed literature review in Wajeeha Shamsi’s 2020 thesis, this article provides a comprehensive overview of the known mycoviruses that call Alternaria home.
The First Discoveries: Unidentified dsRNAs
The story of Alternaria mycoviruses begins in 1988. Researchers studying toxin production in Alternaria alternata noticed something unusual: the presence of unidentified double-stranded RNA (dsRNA) elements in their samples. They found that out of 12 isolates of A. alternata, seven of them harbored dsRNAs ranging in size from 1.0 to 8.0 kbp. In the same year, other scientists reported seeing virus-like particles (VLPs) in tentoxin-producing strains of A. alternata.
These early discoveries were the first clues that this common fungus was a host to its own unique set of viruses. While the viruses were not yet characterized or named, the presence of dsRNA provided the tell-tale signature of a mycoviral infection.
A Growing Catalog of Alternaria Mycoviruses
As of the 2020 thesis, the known Alternaria mycoviruses belong to the following families:
Since those initial findings, the list of identified Alternaria mycoviruses has grown significantly. The identified members of the Alternaria virome to date belong to a wide array of recognized and proposed virus families, showcasing the incredible diversity within just one fungal genus.
- Partitiviridae
- Endornaviridae
- Chrysoviridae
- Totiviridae
- Narnaviridae
- Hypoviridae
- The proposed families Fusariviridae and Alternaviridae
- Botybirnaviridae
- Several unclassified viruses
Let’s look at a few key examples that highlight this diversity.
Notable Examples of Alternaria Mycoviruses
1. Alternaria alternatavirus 1 (AaV1): The First Characterized Virus
Years after the initial dsRNA discoveries, the first fully characterized virus from this genus was identified in 2009. Alternaria alternatavirus 1, found in A. alternata, was a tetra-segmented (four-part) dsRNA virus. It was reported to alter the host’s phenotype by impairing the growth of its colonies. This virus is now part of the proposed family Alternaviridae.
2. Alternaria brassicicola endornavirus 1 (AbEV1): An Endornaviridae Member
Identified in 2015, this mycovirus was found in A. brassicicola. It is a member of the family Endornaviridae, a group of viruses that are notable for their lack of a true capsid and for being transmitted only through cell division and spores.
3. Alternaria alternata chrysovirus 1 (AaCV1): A Virus with Dual Effects
This member of the family Chrysoviridae was identified in a strain of A. alternata that produces a host-specific toxin. This virus exhibits two distinct effects: it is ‘hypovirulent’ to the fungus, slowing its growth, but at the same time, it furnishes the fungus with ‘hypervirulence’ against its plant host, likely due to increased toxin production. This fascinating duality showcases the complex three-way interaction between virus, fungus, and plant.
4. A New Lineage of Partitiviridae: Alternaria alternata partitivirus 1 (AtPV1)
Identified in 2018, AtPV1 represents a new lineage related to the genus Gammapartitivirus. The family Partitiviridae is known for its bi-segmented dsRNA genomes, and the discovery of this novel lineage within Alternaria further underscores the genetic diversity of its virome.
5. Hypovirulence-Inducing Hypoviruses: Alternaria alternata hypovirus 1 (AaHV1)
The family Hypoviridae is famous for containing viruses that reduce the virulence of their fungal hosts. The recent identification of AaHV1 in A. alternata in 2019 was a significant finding. The discovery of hypovirulence-inducing Alternaria mycoviruses opens up exciting possibilities for using them as potential biocontrol agents against pathogenic Alternaria species.
Conclusion
The study of Alternaria mycoviruses has come a long way from the initial reports of unidentified dsRNA bands. The Alternaria virome is now known to be a rich and diverse collection of viruses from at least nine different families, each with its own unique genomic structure and biological effects. From the complex, dual-acting chrysoviruses to the promising hypovirulence-inducing hypoviruses, the viruses that infect this common fungal genus are a microcosm of the broader world of mycoviruses. Their continued study is sure to reveal even more about the intricate and often-hidden interactions that shape our microbial world.
Source & Citations
- Thesis Title: Molecular and Biological Characterization of Mycovirus Identified from Environmental Fungal Isolates
- Researcher: Wajeeha Shamsi
- Guide (Supervisor): Dr. Muhammad Faraz Bhatti
- University: Atta-ur-Rahman School of Applied Biosciences, National University of Sciences & Technology (NUST), Islamabad, Pakistan
- Year of Compilation: 2020
- Excerpt Page Numbers: 11, 12, 13 (PDF pages 46, 47, 48)
Disclaimer: Some sentences have been lightly edited for SEO and readability. For the full, original research, please refer to the complete thesis PDF linked in the section above.
Join the Discussion!
Given the diverse effects of different Alternaria mycoviruses, what do you think is the most promising avenue for future research in this area? Share your thoughts in the comments!
Discover more from Professor Of Zoology
Subscribe to get the latest posts sent to your email.
