. Introduction
Colletotrichum is traditionally recognized as an asexual genus of fungi, with a number of species linked to sexual morphs assigned to the Glomerella genus (Sordariomycetes, Glomerellaceae, Ascomycota). Over the years, Colletotrichum species were considered to be host specific, which led to the description of a large number of taxa (Cannon et al., 2012; Sharma & Shenoy, 2016). Species from this genus are economically one of the most important fungi, and cause anthracnose and other diseases in a wide range of plant species (Cai et al., 2009; Hyde et al., 2009; Sutton, 1980).
The comprehensive monographic study conducted by von Arx (1957) based on morphological characteristics with little emphasis placed on pathological features led to drastic reduction from approximately 750 to 11 species. Molecular studies of Colletotrichum species, which have become an integrated element in taxonomic research, have been developing intensively since the end of the twentieth century. The first applications of DNA sequence data to distinguish between species within this genus used the internal transcribed spacer (ITS1) region of nrDNA. Later, multilocus analyses became a common approach based on the use of ITS2 and large ribosomal subunit (LSU) as well as partial sequences of genes encoding, e.g., histone H3 (HIS), translation elongation factor 1 alpha (TEF-1α), tubulin beta chain (TUB), and actin (ACT) (Cannon et al., 2012). Scientists working on Colletotrichum do not agree on the taxonomic approach and characters that should be employed to identify and describe a new Colletotrichum species. Hence, a reliable secondary barcode marker is indispensable for the accurate identification of Colletotrichum species (Sharma & Shenoy, 2016).
Identification of Colletotrichum species based on morphology has always been problematic; therefore, the current progress in molecular phylogenetic methods facilitates identification of stable and well-separated clades within Colletotrichum. However, the taxonomy of this genus is still unsatisfactory and there is a need for a polyphasic approach for identification, which reflects the natural classification of species and subspecific taxa within the genus (Cai et al., 2009).
Berberis aquifolium (Berberidaceae) is a plant native to western North America. This species was introduced to Europe as an ornamental plant in the 1820s. At present, it grows in many parts of Europe (Sorokopudov et al., 2017). It was introduced in Poland in 1839, and the status of this species has changed from a crop plant to a locally established and invasive species (Tokarska-Guzik et al., 2012).
According to A preliminary checklist of micromycetes in Poland, 23 Colletotrichum species were reported in Poland up until 2008 (Mułenko et al., 2008), while 26 species are currently known (Farr & Rossman, 2020; Jayawardena et al., 2016; Okorski et al., 2018; Pszczółkowska et al., 2016, 2017). The present paper provides information about a new Colletotrichum species for Polish funga (C. japonicum on B. aquifolium); it also reports the second locality of the fungus in Europe and third worldwide.
. Material and Methods
The infected leaves of B. aquifolium were collected in the Botanical Garden of Maria Curie-Skłodowska University (UMCS) in Lublin in 2018. The material sample was stained with cotton blue in lactic acid and gently heated. Observations were made using an Olympus SZX10 stereoscopic microscope and an Olympus CX31 light microscope. Photographic documentation was taken with an Olympus XC50 microscope camera. Measurements were made at ×600 and/or ×300 magnifications. Structure size ranges were specified based on 10 measurements of acervuli, 15 setae, and 30 conidia. The publications mentioned in Table 1 were used for identification of the fungus. The name of the host plant and its synonym is accepted following The Plant List (http://www.theplantlist.org/). The examined specimen is deposited in the herbarium of Maria Curie-Skłodowska University in Lublin (LBL).
Table 1
Features of Colletotrichum species reported to be associated with Berberis aquifolium leaves.
| C. fioriniae (Marcelino & Gouli) Pennycook | C. japonicum (Hemmi)Bedlan | C. mahoniae Fabric. | C. nymphaeae (Pass.) Aa | |
|---|---|---|---|---|
| Leaf spots | Up to 10 mm | 1–5 mm | 1–1.5 mm | 0.5–5 mm |
| Irregularly circular | Mostly irregularly shaped | Rounded | Roundish | |
| Brown, with a margin, surrounded by a chloric halo | First greyish-brown, finally grey | Grey | Pale brownish, greyish-brown with a dark reddish-brown to purplish-brown margin, later dark brown to black | |
| Conidia | 9.9–14 × 3–4.3 µm* | 10.65–16.83 × 5.08–7.51 µm | 12–12.5 × 4.5–5 µm | 11.8–23 × 4.2–5.6 µm |
| Mostly ellipsoidal, short cylindrical or ovoid | Cylindrical | Ellipsoidal or cylindrical | ||
| Ends rounded | Hyaline, two-punctated or granulated | Rounded at the apex, attenuated, occasionally truncate at the base | ||
| Setae | No data | Very few | If present then occur abundantly, with swelled basis | Not formed |
| References | Garibaldi et al., 2020 | Bedlan, 2012 | Fabricatore, 1950 | van der Aa, 1978 |
. Results
Colletotrichum japonicum (Hemmi) Bedlan, J. Kulturpfl. 64(12): 478–481. 2012 (Figure 1)
Figure 1
Colletotrichum japonicum on Berberis aquifolium (LBL M–32789). (A) Leaf spots with visible acervuli. (B) Acervuli. (C) Acervulus with setae. (D) Conidia. Scale bars: (A) 15 mm; (B) 200 µ m; (C,D) 50 µ m. Structures in a microscopic preparation stained with cotton blue in lactic acid. Photographs: U. Świderska-Burek.
Leaf spots mostly elliptical, roundish, or irregular, 2–6 mm in diameter, greyish-brown to greyish with blackish-brown margin. Acervuli within the spots, epiphyllous, 112–300 × 90–180 µm, often with setae. Setae short, black-brown, straight or slightly curved, 40–55 × 3–3.5 µm. Conidia one-celled, hyaline, elliptical or ovoid, straight or slightly curved, rounded at the ends, 12.5–17 × 4.5–6.5 µm.
Specimen examined: On Berberis aquifolium Pursh (Berberidaceae). Poland: Lublin – Botanical Garden of the Maria Curie-Skłodowska University, September 25, 2018, leg. U. Świderska-Burek (LBL M–32789).
. Comments
The analyzed Polish sample exhibits the features of C. japonicum provided in the literature from Austria (Table 1), i.e., the only locality worldwide where the fungus has been noted on the same host (B. aquifolium) (Bedlan, 2012).
On B. aquifolium, three other Colletotrichum species have been reported to date. All of them, C. nymphaeae (Damm et al., 2012), C. mahoniae (Fabricatore, 1950), and C. fioriniae (Garibaldi et al., 2020), were reported from Italy. Additionally, two species were recorded on another host species from the Mahonia genus (currently assigned to the Berberis genus), i.e., M. bealei (Fortune) Pynaert: C. mahoniae from Georgia and C. gloeosporioides Penz. (probable host M. bealei incorrectly reported as M. healei) from China (Bedlan, 2012; Farr & Rossman, 2020).
