Alternaria alternata as endophyte and pathogen

Alternaria alternata is a common species of fungus frequently isolated from plants as both an endophyte and a pathogen. Although the current definition of A. alternate rests on a foundation of morphological, genetic and genomic analyses, doubts persist regarding the scope of A. alternata within the genus due to the varied symbiotic interactions and wide host range observed in these fungi. These doubts may be due in large part to the history of unstable taxonomy in Alternaria, based on limited morphological characters for species delimitation and host specificity associated with toxins encoded by genes carried on conditionally dispensable chromosomes. This review explores the history of Alternaria taxonomy, focusing in particular on the use of nutritional mode and host associations in species delimitation, with the goal of evaluating A. alternata as it currently stands based on taxonomic best practice. Given the recombination detected among isolates of A. alternata, different symbiotic associations in this species should not be considered phylogenetically informative.

Automated summary

Alternaria alternata is a common fungus species that can be found both as an endophyte and a pathogen in plants. However, doubts remain about the scope of A. alternata within the genus due to its varied symbiotic interactions and wide host range. The unstable taxonomy history of Alternaria and the reliance on limited morphological characters and host specificity associated with toxins have contributed to these doubts.