Phaeoisaria synnematicus P.N. Singh & S.K. Singh sp. nov.

Index Fungorum number: IF 830711; MycoBank number: MB 830711; Facesoffungi number: FoF 06138; Fig. 1

Etymology – specific epithet ‘synnematicus’ refers to the formation of synnemata.

Holotype – AMH 10055

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

Saprobic on dead bark of Azadirachta indica Juss., in a terrestrial habitat. Sexual morph Undetermined. Asexual morph Vegetative hyphae septate, branched, smooth-walled, subhyaline to light olivaceous, up to 2.35 μm wide. Chlamydospores 8.5–25.5 × 6–10.5 μm, produced abundantly from submerged and superficial mycelium, intercalary, lateral to terminal, globose, sub-globose, clavate to ampulliform, solitary to catenate, dark brown, smooth walled, wall thickened and darkened, sessile, persistent to caducous, aseptate (rarely with one or two septa). Synnemata up to 960 μm long and 12–30 μm diam., synnematal, erect, rigid, dark brown to olivaceous brown, composed of compact parallel appressed conidiophores, cylindrical to clavate. Conidiogenous cells 1.5–18×0.5–2 μm, polyblastic, integrated, acropleurogenous, terminal or intercalary, sympodial, cylindrical to denticulate, hyaline, smooth walled, denticles simple to rarely branched, hyaline, up to 2 μm long and 1 μm wide. Secession schizolytic. Conidiophores 1.5–960 μm long, 1–3.5 μm wide, macronematous to semi-macronematous, highly geniculate, dark brown to olivaceous brown, synnematous, simple to dichotomously branched, emerging out at the apex and along the sides of the upper half or two thirds of each synnema, dark brown at the base, brown to pale brown towards the apex. Sometimes conidiophores reduced to a single conidiogenous cell, arising from aerial hyphae. Conidia 4–11 × 2–5 μm (x̅=6 × 2.5 μm, n=30), dimorphic, clavate to ellipsoidal, cylindrical to falcate, base narrowly truncate, tip obtuse, variable in size, sometimes constricted near septa, 1–2-guttulate, hyaline, aseptate to one septate, smooth-walled.

Culture characteristics – on MGYP (Malt Extract Glucose Yeast Peptone agar), slow growing, floccose, pale yellow (4A3), 37×37 diam. in 37 days at 25 °C, periphery light grey, floccose (1C1), margin regular, reverse dark brown (7F-4). Hyphae septate, unbranched to branched, smooth walled subhyaline to light olivaceous, 1.8–2.3 μm wide.

Material examined – INDIA, Maharashtra, Pune District, dead bark of Azadirachta indica (Meliaceae), 4 June 2017, P.N. Singh, AMH 10055 (holotype), ex-type living culture, NFCCI 4479.

GenBank Numbers – ITS=MK391494, LSU=MK391492.

Notes – The present taxon was isolated in pure culture from dead bark of Azadirchta indica. The overall morphological and cultural characteristics are distinct from other species in the genus. Though in having prominent synnemata the morphological characters are comparable with some species, like Phaeoisaria clematidis (Hughes 1958) and P. aquatica (Luo et al. 2018). The new species is different in having smaller synnemata (399–960× 12–30 μm) as against to larger (1000–1500×20–80 μm) in P. clematidis. Conidia in present taxon are significantly larger (4–11 × 2–5 μm) as compared to smaller conidia in P. annesophiae (4.5–9 × 2–3.5 μm) (Crous et al. 2017), P. clematidis (4–10×1.5–2.5 μm), P. aquatica (6.5–7.5 μm long) and P. guttulata (3.5–5.5×2.5–4.8 μm) (Hyde et al. 2018a). Our new taxon is distinct from P. annesophieae (Crous et al. 2017) in the presence of synnemata, which is absent in the latter taxon. Similarly, the new taxon is also different from P. guttulata (Hyde et al. 2018a) in having larger synnemata (480–700×2–5 vs. 399–960×12.35–30 μm) and conidia (3.5–5.5×2.5–4.8 vs. 4–11×2–5 μm). As such, in overall morphological features, the present taxon is distinct from allied taxa.

Figure 1 – Phaeoisaria synnematicus (AMH 10055, holotype). a Substrate (Bark of Azadirchta indica). b Colony morphology (front view). c Reverse view of colony. d, e Stereoscopic view of synnemata (in culture). f Numerous synnemata (slide culture microscopic view). g Synnema showing splaying conidiophores. h Numerous simple to catenate chlamydospores. i Persistent lateral to terminal produced sub-globose chlamydospores. j Enlarged view of conidiophores showing acropleurogenous conidiogenous cells and conidia. k Enlarged microscopic view of fusoid to clavate conidia and hyphae. l Curved and cylindrical guttulate conidia produced from small conidiophores. Scale bars: g–l=20 μm

Figure 2 – Maximum likelihood phylogenetic tree based on a combined LSU, ITS, SSU and RPB2 sequence data of genera in Pleurotheciaceae. Conioscypha peruviana CBS 137657 and C. pleiomorpha FMR 13,134 were selected as the outgroup taxa. Bootstrap support values for maximum likelihood (MLBS, left) equal to or greater than 70% is given above the nodes. Bayesian posterior probabilities (BYPP, right) equal to or greater than 95% are given above the nodes. Ex-type strains are in bold and newly generated sequences are in blue