Paraconiothyrium ajrekarii S. Rana & S.K. Singh, sp. nov.

Index Fungorum number: IF557844; MycoBank number: MB557844; Facesoffungi number: FoF 08020; Fig. 1

Etymology – Named after Late Professor S.L. Ajrekar, who was a distinguished mycologist and plant pathologist of India.

Holotype – AMH 10218

Color Codes Follow – Methuen Handbook of Colour (Kornerup and Wanscher 1978).

From leaf phylloplane of Mangifera indica L. (Anacardiaceae). Sexual morph Undetermined. Asexual morph Hyphae 1–4 μm (x̅=3 μm, n=15), hyaline to light olivaceous, smooth-walled. Chlamydospores 6–23.5×6–10.5 μm (x̅=10.5×8 μm, n=15), solitary or in chains, globose to sub globose, wall thickened and darkened, sub hyaline to light olivaceous to dark brown. Conidiomata up to 500×300 μm diam., pycnidial, deeply seated, produced in groups, globose to sub globose to oval, dark brown, sometimes with elongated ostiolar neck (up to 245× 84 μm). Peridium up to 33 μm, multi-layered, textura angularis, delicate, pale brown. Conidiophores reduced to conidiogenous cells, variable in shape and size. Conidiogenous cells 7.5–21 × 3–8.5 μm (x̅= 12 × 5 μm, n = 15), short, phialidic, with a collarette, flask-shaped, elongated, ampuliform with swollen basal cell, smooth walled, hyaline. Conidia 3–6×1–4 μm (x̅=5×3 μm, n=30), subhyaline, light olivaceous to olivaceous brown, oval to broadly fusoid, rarely angular, aseptate, wall smooth, thickened and darkened.

Culture characteristics – Colonies on PDA reaching 34 mm diam. after 2 weeks, at 25 °C; floccose, circular, umbonate with smooth margins; sulcate on both sides; front colour pinkish white (7A2) to chalky white (7A1), reverse grayish brown at center, light yellow (4A4) towards margin. Colonies on V8 juice agar reaching 46 mm after 2 weeks, at 25 °C; circular, flat, slightly floccose, margin smooth and regular; front colour yellowish white (4A2), reverse grayish yellow (golden wheat) (4B5) and sulcate. Colonies on oat meal agar reaching 61 mm after 2 weeks, at 25 °C; circular, floccose, umbonate, sulcate, margins smooth; front colour orange white (6A2) to white (1A1), reverse light yellow (4A4) and sulcate. Colonies on PCA reaching 57 mm after 2 weeks, at 25 °C; circular, floccose, slightly raised, margins smooth, regular; front colour pale orange (5A3) to dull green (25E3), periphery beige (4C3), reverse dark green (28F6) to light yellow (4A4). Colonies on Czapek Dox agar (CDA) reaching 61 mm after 2 weeks at 25 °C; circular, slightly floccose, velvety, sulcate, margins smooth and regular; colour from front orange grey (5B2) in centre and reddish blond (5C3) towards periphery, reverse brownish orange (5C3) in centre and periphery, beaver (5F4) in middle, sulcate. Colonies on MEA reaching 53 mm after 2 weeks at 25 °C; circular, slightly floccose, margins smooth, regular; front colour white (1A1) in centre and dark blonde (5D4) towards periphery, reverse chocolate brown (6F3) in centre and clay (5D5) towards margins.

Material examined – INDIA, Himachal Pradesh, Kangra, Baijnath, Simbal, from leaf phylloplane of Magnifera indica L. (Anacardiaceae), 10 May 2019, S. Rana (AMH 10218, holotype), ex-type living culture, NFCCI 4810.

GenBank numbers  – β-tubulin = MT394161, ITS=MT372906, LSU=MT372905.

Notes – This current taxon is placed in Paraconiothyrium based on pycnidial conidiomata, phialidic conidiogenous cells producing aseptate, thick and smooth-walled, light olivaceous  to olivaceous brown conidia (Verkley et al. 2004). Paraconiothyrium ajrekarii differs from other known species based on its phylogenetic as well as morphological analyses (Fig. 1). The combined β-tubulin, ITS and LSU phylogeny indicates that Paraconiothyrium ajrekarii forms a sister taxon with P. archidendri and P. magnoliae. Paraconiothyrium ajrekarii differs from P. archidendri based on its combination of characters such as dimensions of conidiomata and conidiogenous cells (Verkley et al. 2014). Paraconiothyrium ajrekarii has somewhat slender conidia in comparison to P. archidendri (Table 2). Conidiogenous cells in P. ajrekarii has collarette, flask shaped with swollen basal cells as against blastic to annellidic in P. archidendri. However, Paraconiothyrium ajrekarii is an asexual morph and hence cannot be compared with morphological characters of P. magnoliae as it is reported to have only a sexual morph (Ariyawansa et al. 2014b). However, Paraconiothyrium ajrekarii is an asexual morph and cannot be compared with P. magnoliae reported to have only a sexual morph (Ariyawansa et al. 2014b). A megablast search using the ITS sequence data of P. ajrekarii revealed closest affinities with members of Paraconiothyrium, i.e. Paraconiothyrium archidendri CBS 168.77 (similarity=552/571 bp, 96.67%) and P. magnoliae MFLUCC 10-0278 (similarity=496/517 bp, 95.94%). In the phylogenetic analysis based on combined β-tubulin, LSU and ITS sequence data, Paraconiothyrium ajrekarii forms a distinct linage from P. archidendri with 75% MLBS, 0.90 BYPP support (Fig. 2). Thus, we illustrated and described as a novel species.

Figure 1 –  Paraconiothyrium ajrekarii (AMH 10218, holotype). a–c Colonies from surface on various media after 2 weeks; a MEA, b V8 juice agar, c Czapek Dox agar. d Conidiomata. e, f Enlarged view of conidiomata. g, h Conidiogenous cells showing distinct collarette rings. i, j Condiogenous cells bearing developing conidia. k Chlamydospores. l Conidia. Scale bars: d–f=100 µm, g–l=10 µm

Figure 2 – Molecular phylogenetic analysis by maximum-likelihood (ML) method based on combined β-tubulin, LSU and ITS sequence data. Statistical supports are indicated next to each node, non-parametric maximum likelihood ultrafast-bootstrap (UFBS) values and SH-aLRT obtained from 1000 replicates using IQ-TREE and the TIM3+F+I+G4 model. Bootstrap values for maximum likelihood (MLBS) equal to or greater than 50% are labeled on the nodes. Twenty-one strains are included in the combined analyses which comprise 2393 sites of which 2089 were found to be conserved, 286 were the variable sites and included nearly 178 parsimony-informative sites. The optimized log-likelihood values of − 5846.542 is presented. Estimated base frequencies are as follows: A=0.300, C=0.183, G=0.205, T=0.312; substitution rates AC=2.10979, AG=3.70012, AT=1.00000, CG=2.10979, CT=8.84516, GT=1.00000; gamma distribution shape parameter α=0.559. New sequence data of Paraconiothyrium ajrekarii (AMH 10,218; NFCCI 4810) is highlighted in blue bold and all sequences from type specimen is in bold

Figure 3 – Morpho-taxonomic comparison of Paraconiothyrium ajrekarii sp. nov. with closest taxa