Multigene phylogeny and morphology reveals a new genus in the family Phaeosphaeriaceae associated with leaf spot disease on Fallopia convolvulus

Phaeosphaeriaceae is a species-rich family in the order Pleosporales (Dothideomycetes), encompassing species with diverse lifestyles viz., endophytic, epiphytic, lichenicolous, phytopathogenic, saprobic, and even human pathogenic. In a survey exploring the fungal species associated with leaf spot diseases of herbaceous plants in Giulan province, a coelomycetous fungus was recovered from Black Bindweed (Fallopia convolvulus (L.) Á.Löve). A subsequent phylogenetic study based on combined LSU, ITS and rpb2 sequence data placed these isolates within the family Phaeosphaeriaceae, distinct from presently known genera in the family. On sterile Urtica dioica stems on SNA, the new fungus produces pycnidial conidiomata up to 250 µm diam, black, erumpent, subglobose with central ostiole, exuding pale orange to creamy conidial mass, wall of 4–7 layers of brown textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells are phialidic, hyaline, smooth, aggregated, lining the inner cavity, ampulliform, 7–15 × 3–6 µm, with percurrent proliferation at apex. Conidia are hyaline, smooth, thin-walled, scolecosporous, subcylindrical, with obtuse apex and truncate to subtruncate base, 5–12-septate, (24–)32–45(–55) × (3–)4.5–6 µm. To our knowledge, the new genus is the first association of a fungus belonging to the family Phaeosphaeriaceae on the plant genus Fallopia. Current literature further demonstrate that a delimitation of taxa in coelomycetes based solely on morphological features is not feasible and emphasizes the necessity of combining multigene sequence data with morphology and ecology for accurate identification of the taxa in the coelomycetous fungi.

Key Words: Coelomycetes, new taxa, phylogeny.