Calophoma

Fungalpedia – Note 127 Calophoma

Calophoma Qian Chen & L. Cai

Citation when using this entry: Aumentado et al. in prep – Fungalpedia, plant pathogens. Mycosphere.

Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig *.

Ascomycota, Pezizomycotina, Dothideomycetes, Pleosporomycetidae, Pleosporales, Didymellaceae

Calophoma was established by Chen et al. (2015) with Calophoma clematidina as its type species. Species belonging to this genus are characterized by pycnidial conidiomata which can be subglobose to irregular, and they may be found on the agar surface or immersed. These conidiomata can occur as solitary entities or may be confluent. Conidiomata are ostiolate, but in older cultures, they may have an elongated neck. Micropycnidia are also present. The pycnidial wall is pseudoparenchymatous and consists of 2–6 layers, with the outer wall being pigmented. The conidiogenous cells are phialidic, hyaline, smooth, and vary in shape from globose to flask-shaped, ampulliform, or doliiform. The conidia vary both size and shape, including subglobose, subcylindrical, ellipsoidal, and somewhat obclavate-fusiform. They can be hyaline or slightly brown, with smooth and thin walls. The conidia are aseptate, but occasionally, large 1-septate conidia may be present, which can be eguttulate or guttulate. Chlamydospores are only observed in one species. They may be uni- or multicellular, with unicellular intercalary forms that are guttulate and have thick walls. Additionally, there are multicellular irregular dictyo/phragmosporous chlamydospores that appear somewhat botryoid. These forms may occur in combination with unicellular chlamydospores (Chen et al. 2015).

Calophoma (Ca) was emended by Chen et al. (2015) to accommodate five species namely Ca. aquilegiicola (Phoma aquilegiicola), Ca. clematidina (Phoma clematidina), Ca. clematidis-rectae (Phoma clematidis-rectae), Ca. complanata (Phoma complanata), Ca. glaucii (Phoma glaucii), Ca. vodakii (syn. D. vodakii) and an unidentified species (CBS 186.55), previously belonging to Phoma with subglobose, subcylindrical, ellipsoidal, slightly obclavate-fusiform conidia and highly supported phylogenetic placement establishing the genus. There are 14 recognized species based on morpho-molecular sequence data based on recommended genetic markers, internal transcribed spacer (ITS) region, 28S ribosomal RNA gene (LSU), β-tubulin (β-tub), and RNA polymerase II second largest subunit (rpb2) (Maharachchikumbura et al. 2021, Hou et al. 2020, Crous et al. 2019, Hyde et al. 2019, 2020, Tibpromma et al. 2017, Chen et al. 2015).

As a pathogen, Calophoma incites several symptoms such as leaf spots, and wilting of leaves, stems, or even the entire plant. Additionally, it causes internal blackening and girdling of the stem, often near the soil level, as well as root rot (van de Graaf 1999a, 1999b, van de Graaf 1998). Calophoma affects mostly weed species, is frequently regarded as a weed pathogen, and is used as a biocontrol agent against obnoxious/ invasive weed species (Sokornova et al. 2023, Smith & Cole 1991). Pathogenicity assays were conducted on plant species including various Clematis spp. (Špetík et al. 2023, Golzar et al. 2011, Woudenberg et al. 2009, van de Graaf 2001), Falcaria vulgaris (Karimzadeh et al. 2020), Pastinaca sativa (Sultana et al. 2021), Aegopodium podagraria (Hou et al. 2020), and Heracleum sosnowskyi (Sokornova et al. 2023, Gasich et al. 2013) which severity reached from 40% to 70% necrotic area (Gasich et a. 2018). Calophoma complanata was reported to not only induce necrotic symptoms on the leaves and stems of Archangelica officinalis but also hinder the germination of schizocarps and prompt germ necrosis (Machowicz-Stefaniak et al. 2014).