Alternaria alternata as endophyte and pathogen

Area of Science:

• Mycology
• Plant Pathology
• Taxonomy

Background:

• Alternaria alternata is a ubiquitous fungus with diverse plant interactions, acting as both endophyte and pathogen.
• Current species definitions rely on morphology, genetics, and genomics, yet taxonomic ambiguity persists.
• Instable taxonomy in the Alternaria genus, limited morphological characters, and host-specific toxins contribute to taxonomic uncertainty.

Purpose of the Study:

• To review the history of Alternaria taxonomy, focusing on species delimitation methods.
• To evaluate the current taxonomic standing of Alternaria alternata based on best practices.
• To assess the phylogenetic significance of symbiotic associations in A. alternata.

Main Methods:

• Historical review of Alternaria taxonomy.
• Analysis of species delimitation criteria, including nutritional modes and host associations.
• Evaluation of genetic data, particularly recombination patterns.

Main Results:

• The historical taxonomy of Alternaria has been unstable, often relying on limited characters.
• Host associations and nutritional modes have been inconsistently applied in species delimitation.
• Recombination detected within A. alternata indicates that symbiotic associations are not phylogenetically informative.

Conclusions:

• The broad scope of Alternaria alternata is challenged by its varied symbiotic interactions and wide host range.
• Taxonomic best practices require a re-evaluation of A. alternata's species concept.
• Symbiotic associations within A. alternata should not be used for phylogenetic species delimitation due to detected recombination.