Large-spored Alternaria pathogens in section Porri disentangled

Area of Science:

• Mycology
• Plant Pathology
• Molecular Phylogenetics

Background:

• The fungal genus Alternaria is ubiquitous and was recently divided into 24 sections.
• Alternaria section Porri is the largest, encompassing species with medium to large conidia and long beaks, including significant plant pathogens.
• Accurate species identification is crucial for understanding and managing plant diseases.

Purpose of the Study:

• To revise the taxonomy of Alternaria section Porri using multi-gene phylogenetics and morphological data.
• To clarify species boundaries and identify causal agents of economically important plant diseases.
• To describe new species and synonymize existing names within Alternaria section Porri.

Main Methods:

• Construction of a multi-gene phylogeny using ITS, GAPDH, RPB2, TEF1, and Alt a 1 gene regions.
• Supplementation of molecular data with morphological and cultural studies for species recognition.
• Comparative analysis of isolates causing specific plant diseases.

Main Results:

• Recognition of 63 species within Alternaria section Porri, including 10 newly described species.
• Synonymization of 27 previously recognized species names.
• Clarification of early blight pathogens on tomato (synonymized under A. linariae) and potato (A. protenta, A. solani, A. grandis).
• Confirmation of A. allii and A. porri causing onion purple blotch, with challenges in distinguishing them based on beak and branch numbers.
• Delineation of three species affecting Passifloraceae, reducing the previous count from four.
• Identification of three species affecting sweet potato, including two new species.
• Description of a new Alternaria section with two large-spored species possessing concatenate conidia.

Conclusions:

• The taxonomic revision of Alternaria section Porri provides a more robust species concept based on integrated data.
• Accurate identification of Alternaria species is essential for effective disease management strategies in agriculture.
• This study contributes significantly to the understanding of Alternaria diversity and its role as plant pathogens.