Resolving the polyphyletic nature of Pyricularia (Pyriculariaceae)

Area of Science:

• Mycology and Plant Pathology
• Molecular Systematics
• Fungal Taxonomy

Background:

• Species of Pyricularia cause significant grass diseases, including rice blast disease (Pyricularia oryzae) and foliar diseases in wheat and millet.
• Existing classifications of Magnaporthe-like fungi were challenged by differing spore morphologies and recent reallocations (e.g., Magnaporthe salvinii to Nakataea).
• The need for a robust taxonomic framework for Pyricularia and related genera was evident, as traditional criteria like host range and conidium morphology proved insufficient.

Purpose of the Study:

• To clarify the phylogenetic relationships among Pyricularia and Magnaporthe-like species using multi-gene DNA sequence data.
• To establish a more accurate taxonomic classification for these economically important fungal pathogens.
• To re-evaluate generic and species concepts within the Pyriculariaceae family.

Main Methods:

• Phylogenetic analysis was conducted using partial DNA sequences from multiple genes (LSU, ITS, RPB1, actin, calmodulin).
• Isolates were selected to represent a wide range of host plants and morphological types.
• Morphological characteristics of conidia and conidiophores were documented and compared with phylogenetic data.

Main Results:

• Species of Pyricularia sensu stricto form a monophyletic clade, defining the new family Pyriculariaceae, sister to the novel Ophioceraceae.
• These families are distinct from the Magnaporthaceae, which includes Magnaporthiopsis and Nakataea.
• The study identified 10 new genera and seven new species, proposing a revised classification based on integrated morphological and phylogenetic evidence. Host range and conidium morphology were found to be unreliable taxonomic markers alone.

Conclusions:

• The phylogenetic framework supports the establishment of Pyriculariaceae and Ophioceraceae, resolving taxonomic ambiguities in Magnaporthe-like fungi.
• Conidium morphology and host range are insufficient for generic-level classification, emphasizing the importance of molecular data.
• The research provides a revised taxonomic understanding of Pyricularia and related genera, including the description of novel taxa.