Paramicrosphaeropsis eriobotrium sp. nov. a New Agent of Loquat Canker in Iran

Loquat (<em>Eriobotrya japonica</em>) is a subtropical evergreen plant important in terms of both horticulture and green space in the urban environment. In recent years, symptoms of branch and trunk canker, dieback, and decline have been observed in the main cultivation areas of this tree in Iran. To study the etiology of loquat canker in Fars Province, branches and trunks of loquat trees with disease symptoms were sampled from 2018 to 2019. Several isolates of an unknown <em>Paramicrosphaeropsis</em> species (<em>Didymellaceae, Pleosporales, Dothidiomycetes</em>) were recovered from the trunks and branches of infected loquat trees. Phylogenetic analysis of the isolates based on a multi-gene phylogeny of the ribosomal internal transcribed spacer (ITS), partial beta-tubulin gene (<em>tub2</em>) and the second-largest subunit of RNA polymerase II (<em>rpb2</em>) loci revealed that the isolates belonged to a new taxon, <em>Paramicrosphaeropsis eriobotrium </em>sp<em>. </em>nov<em>. </em>Pathogenicity tests revealed that this species was able to cause canker, trunk flaking, dieback, decline, leaf yellowing, defoliation and growth reduction in loquat trees. A host range evaluation on the detached branches of some important horticultural trees occurring adjacent to the loquat tree orchards of Fars Province showed that this species might have a broader host range, as it was also able to infect almond and olive trees. <em><strong>Paramicrosphaeropsis eriobotrium </strong></em>B. Tavakolian &amp; Mostowf. <strong>sp. nov.</strong> <em>Conidiomata</em>: pycnidial, (242.4–1117.6) × (130.1–944.4) μm (av. 513.4±182.2 × 363.8±143.1 μm) globose to subglobose, mostly solitary, sometimes confluent, pale brown and semi-immersed. <em>Ostiole</em>: erumpent and somewhat papillate. <em>Pycnidial wall</em>: pseudoparenchymatous, multilayered, thin, of <em>textura angularis</em>, hyaline at the beginning, dark brown at maturity<em>.</em> <em>Chlamydospores</em>: in chains, (5.4–14.3) × (3.9–14.3) μm (av. 8.7±1.6 × 7±1.5 μm), brown, ellipsoidal to globose, smooth, thick-walled. <em>Conidiogenous cells</em>: (7.2–20.2) × (5.3–15.4) μm (av. 11.8±2.8 × 8.6±2.1 μm), hyaline, phialidic, smooth, subglobose, ampulliform or lageniform to doliiform. <em>Conidia</em>: (3.5–11.2) × (2.8–7.9) μm (av. 6.7±0.5 × 4.3±0.5 μm), solitary, variable in shape, ellipsoidal, subcylindrical, obpyriform, straight to slightly curved, aseptate, hyaline at the beginning and pale brown, yellowish brown or greenish brown with age. <em>Colonies</em> <em>on PDA</em>: reaching 6.9 mm after 14 d, aerial mycelium flat, white at the beginning and darkened over time, dark orange at the center, margin regular, some black pycnidia visible after 20-25 d; reverse white at the beginning and brown to dark brown with age. <em>Colonies on MEA</em>: reaching 6.8 mm after 14 d, aerial mycelium floccose, white at the beginning, brown with age, margin smooth, pycnidia visible after one mo if formed; reverse dark orange at the center and dark brown with age. <em>Colonies on OA</em>: 6.7 mm after 14 d, immersed mycelium flat, white and pale olivaceous at the beginning, dark olivaceous with age, forming growth circles and sector, margin wavy, pycnidia visible after 14-20 d at 25 °C, under fluorescent light (12 h light/12 h dark) like small black dots; reverse dark olivaceous. All isolates of this species had a minimum growth temperature of 5°C, an optimum of 25°C and a maximum of 30 °C on MEA in the darkness.