Calonectria potisiana Melo & R.F. Alfenas, sp. nov.
Index Fungorum number: IF 901065; Mycobank number: MB 901065; Facesoffungi number: FoF 14769; Fig. 1
Etymology – “Potis” reference to the name of an extinct indigenous tribe that inhabited the banks of the Poti River, Teresina, Brazil, the geographic region where the fungus was collected.
Holotype – VIC 4741
Associated with Strutanthus sp., necrotic leaf spots. Sexual morph: Protoperithecia 48–45 µm, globose to oval, superficial distribution in the culture medium, orange. Fertile perithecia 160–420 µm, pear-shaped, orangered, turning red-brown with time. Asci 45–98 × 8–22 µm (x̅= 38–88 × 8–18 μm, n = 20), 8 ascospores, clavate. Ascospores 39–42×5–7 µm (x̅=38–41×4–7 μm: n=20), hyaline, guttulate, fusoides, with 1–3-septate, with constriction in the septum, Asexual morph: Produced on 18 days old MEA culture, Conidiophores 65–112×3–4 µm, consist of a stipe with a penicillate arrangement, 1-septate, hyaline. Phialides 22–43 × 2–4 µm (x̅=20–38 × 1,8–3,8 μm n=10), branched hyaline, 3–4 per branch. Macroconidia 45–52 × 3–5 µm (x̅=42–48 × 2,6–4,8 µm. n=20), cylindrical, hyaline, rounded at both ends, 3- septate. Stipe 85–132 × 2–4 µm (x̅: 82–128 × 1,6–3,5. n:10), hyaline, septate, terminal naviculata vesicles, Chlamydospores 25–38 µm globose, solitary or in short chains with thick walls,
Culture characteristics – Fast growing on MEA medium, growth rate 32 mm/day, mycelium white, brown at the centre, aerial, cottony to flaky, reverse umber. Abundant production of spores on aerial mycelium, especially in the centre of the culture.
Material examined – Brazil, State of Piauí, Teresina, Campus of the Federal University of Piauí, Center for Agricultural Sciences, Agricultural Sciences, on necrotic leaf spots of Struanthus sp., (Loranthaceae), April 20, 2018, M.P. Melo, original code (VIC 4741 holotype), ex-type, COUFPI 186.
GenBank numbers – COUFPI 186: tef1-α= OR500380, cal = OR500371, his = OR500374, tub2 = OR500377, COUFPI 196: tef1-α = OR500381, cal = OR500372, his = OR500375, tub2 = OR500378, COUFPI 299: tef1-α = OR500379, cal = OR500370, his = OR500373, tub2=OR500376.
Notes – Calonectria potisiana, is a fungus associated with necrotic leaf spots in Struanthus sp., with spores in the center of the lesions. In the phylogenetic analysis, using the tef1-α, tub2, his, and cmdA sequences, C. potisiana is placed in the C. naviculata complex, with 100% ML bootstrap and 1.00 BYPP supports, having C. multiphialidica as a sister clade, (Fig. 2). When cultivated in carrot agar culture medium, C. potisiana produces a high number of perithecia, resulting in fertile ascospores. Calonectria potisiana can be differentiated from the species of the C. naviculata complex by its 3-septate macroconidia and producing perithecia and fertile ascospores. Due to the number of morphological markers for accurate differentiation of the species in the C. naviculata complex, multigene phylogenetic analysis of the tef1-α, tub2, his, and cmdA genomic regions is necessary for correct species delimitation (Liu etal. 2020). Most species of the C. naviculata complex are saprophytic, living on soil and litter (Alfenas et al. 2015). Recently, new species of Calonectria have been described in Brazil (Sanchez-Gonzalez et al. 2022). Here we introduce C. potisiana as a new species associated with leaf spots on Strunthus sp., showing that tropical regions have a high diversity of Calonectria species.
Figure 1 – Calonectria potisiana (COUFPI 186, ex-type). a Leaf spots on Strunthus sp. b Frontal view of the culture. c reverse view of the culture. d Protoperithecia. e cirri (red arrow). f Perithecia. g Asci with ascospores. h Ascospores. i Macroconidia. j Branched phialides. h Stipe with the presence of vesicula. Scale Bars: d, e, f: 2 µm; g, h, i: 10 µm. j, k: 20 µm
Figure 2 – Bayesian phylogenetic tree of Calonectria. The tree was built using concatenated sequences of the genes cal, his, tef-1α and tub2. Bayesian posterior probability values≥0.90 are indicated above the nodes. The sequences generated in this study are highlighted in bold. This tree is rooted with Calonectria pteridis