Epicoccum indicum S. Rajwar & Raghv. Singh, sp. nov.

Index Fungorum number: IF 900238; Mycobank number: MB 900238; Facesoffungi number: FoF 16038; Fig. 1

Etymology – indicum, refers to India, the country where the fungus was discovered.

Holotype – AMH 10466

Associated with diseased inflorescence of Chrysopogon zizanioides. Sexual morph: Not observed. Asexual morph: Conidiomata or conidiomata-like structure absent. Symptoms develop on inflorescence, brown to dark blackish brown, later on covering the entire inflorescence surface. Colonies brown to dark blackish brown, velvety. Mycelium 2–3.5 µm wide (x̅=2.5 μm, n=20), external, septate, hyaline to light olivaceous brown, sometimes loosely arranged to form prosenchymatous-like structures, 12–20 µm wide (x̅= 15 μm, n = 20). Stromata absent. Conidiophores 7–42×1.5–4.5 µm (x̅=19.5×3 μm, n=20), macronematous, mononematous, later on develop as a lateral branch of superficial hyphae, initially unbranched, later on highly branched, claviform, erect to procumbent, hyaline to light olivaceous brown, smooth to slightly rough, thin-walled to thick-walled, 0–5-euseptate. Conidiogenous cell indeterminate. Conidia 10–20×7–17 µm (x=15.5×12.5 µm, n=40), formed singly, dry, light olivaceous brown to mid brown, variable in shape, mostly oval to elliptical, rarely globose to sub globose, sometimes irregular, 1-many celled, constricted at septa, slightly roughened at maturity, thick-walled, 0.5–2 µm (x=1.2 µm, n=20).

Culture characteristics – Conidia germinating on PDA within 24 h. Colonies cottony, pinkish white, lower surface off pale brown to blackish brown, form reddish pigments, reaching 20–25 mm diam. in 7 days at 25±5 °C. Mycelia are superficial, effuse and radially striate with regular edges. Sporulation was not observed after 30 days under 25±5 °C.

Material examined – India, Uttar Pradesh, Varanasi, Botanical Garden of Banaras Hindu University, living inflorescence of Chrysopogon zizanioides (L.) Roberty (Poaceae), 10 October 2021, Raghvendra Singh, (AMH 10466, holotype; MHBHU 66, isotype), ex-type NFCCI 5322.

GenBank numbers – ITS: ON627840, LSU: OP850270, rpb2: OP946257 

Notes – Epicoccum andropogonis (Ces.) Schol-Schwarz was described (Schol-Schwarz 1959) on infected grasses with ergot. In 2019, Vu et al. (2019) assigned CBS 195.55 and CBS 193.55 as E. andropogonis which was collected from South Africa. Similarly, Hatami Rad et al. (2019) assigned IRAN 3738C as E. andropogonis collected from Iran, based on ITS-rDNA sequence data that clustered closer to CBS 195.55 and CBS 193.55. Detailed morphological description for IRAN 3738C was provided only from ex-type culture (Hatami et al. 2019). In the phylogenetic analysis of the present study, we observed that CBS 195.55 and CBS 193.55 (assigned for E. andropogonis) are clustered together with Epicoccum indicum (NFCCI 5322) and the morphological characters of NFCCI 5322 are different from E. andropogonis (Ellis 1971). In E. andropogonis well-developed sporodochia bearing densely aggregated conidiophores are found which are lacking in Epicoccum indicum. In Epicoccum indicum conidiophores are mononematous and later on develop as a lateral branch of superficial hyphae, initially unbranched, later on highly branched. Moreover, E. indicum is reported on new host. Since all these strains (CBS 195.55, CBS 193.55 and IRAN 3738C), along with our newly collected strain NFCCI 5322 clustered together with 98% ML bootstrap support and 1.00 BYPP values, we identified these strains as a sister lineage of E. dendrobii (Fig. 2). Since, the microphotographs and dimensions of conidia from the extype culture of IRAN 3738C fit into the frame of E. indicum, therefore, it is worthwhile to recombine E. andropogonis assigned for CBS 195.55, CBS 193.55 and IRAN 3738C under E. indicum and we choose Epicoccum indicum as none of these strains not fitting in the morphological frame of E. andropogonis. Epicoccum indicum also differs from closely related E. dendrobii as later form well-developed sporodochia bearing densely aggregated conidiophores and conidia are smaller (11–19 μm) and have basal cells (Chen et al. 2017).

Figure 1 – Epicoccum indicum (AMH 10466, holotype). a Host plant in its natural habitat, b Symptoms on inflorescence, c Appearance of superficial hyphae bearing conidiophores and conidia on host surface, d Germination of conidia on PDA, e, f Reverse and front view of colony on PDA after 7 days (NFCCI 5322, ex-type), g–n Superficial hyphae bearing conidiophores and conidia, o–u conidia. Scale Bars: e, f=10 mm, g–u=10 μm

Figure 2 – Phylogram generated from maximum likelihood analysis based on a three-locus dataset (LSU, ITS and RPB2) representing Epicoccum indicum (NFCCI 5322) and related species. The scale bar indicates 0.08 changes. The tree is rooted in Neocucurbitaria aquatica (CBS 297.74). Species sampling was based on Hou et al. (2020). One hundred-eleven sequences are included in the analysis which comprises 1850 characters after alignment. ML analysis was performed using a GTR model of site substitution, including GAMMA+P-Invar model of rate heterogeneity and a proportion of invariant sites. Bayesian inference was implemented with the GTR+I+G model. The best RAxML tree with a final likelihood value of−9265.764120 is presented. Estimated base frequencies were as follows: A=0.243820, C=0.240756, G=0.279920, T=0.235504; substitution rates: AC=1.874052, AG=6.412815, AT=2.187577, CG=1.253908, CT=17.584563, GT=1.000000; gamma distribution shape parameter α=0.138623. Bootstrap support values obtained in a complementary Maximum Likelihood analysis (MLBS, right) with RAxML using 1000 pseudoreplicates are provided after the BYPP values (left). Bootstrap support values for ML equal to or greater than 70% and BYPP equal to or greater than 0.95 are given above the nodes. For each terminal, the species name and the voucher/herbarium code are indicated, and new isolate is in blue

Figure 2 – (continued)