Xylaria sridharii Sharath. & Mahadevak., 2023

Sharathchandra, Kodandoor, Mahadevakumar, Shivannegowda, Nuthan, Bettadapura R. & Satish, Shreedharamurthy, 2023, Xylaria sridharii sp. nov. - a new species of Xylariaceae from India, Phytotaxa 625 (2), pp. 180-190 : 183-187

Xylaria sridharii Sharath. & Mahadevak. sp. nov. FIGURE 1 & 2

MycoBank no.: MB847121

Type: INDIA, Karnataka, Mangalore, Konaje , Mangalore on the leaflet of Coconut ( Cocos nucifera ), May 5, 2019, Holotype: NFCCI-5117 , Ex-type UOM2022-18

Etymology: sridharii (Lat.) : referred to Prof. Kandikere R. Sridhar, an eminent mycologist from India for his outstanding contribution to the field of mycology in India spanning over four decades.

GenBank Accession ITS: OQ146975 , LSU: OQ1469977 , tub2: OQ176250

Saprobic on dead leaflets of Cocos nucifera ( Arecaceae ). Sexual morph: Stromata upright or prostrate, unbranched or sometimes branched, 1.2–2.3 mm diam., 1–2 mm thick, texture soft, externally black, internally white and smooth, but sometimes verrucose because of the perithecial mounds, terminate with round globose, sometimes elongated fertile head measured 4–6 mm diam and terminated with a thin filiform appendage (6–8 mm in length) at the apex. The stromata showed multiple branching (2–4, but rarely recorded up to 6) at the apex and each branch produced a fertile part that ended with a thin filiform appendage. The perithecia are prominent or embedded, 0.4–0.6 mm diam.; ostioles are slightly papillate or inconspicuous. Stipes are thin and hirsute, up to 6 cm long. The entire stromata are covered with hair. Asci eight-spored, cylindrical, long stipitate, 138–210 × 9.5–12.3 µm, the spore-bearing part 90–140 µm long. Ascospores brown to dark brown, unicellular, ellipsoid, (14–)16.2–19(–22.7) × 5.4–8.2 µm, smooth, no germ slit, with broadly or narrowly rounded ends, each bearing a round hyaline non-cellular appendage. Asexual morph: undetermined.

Cultural Characteristics: Colonies growing on PDA, reaching 80 mm diam. in 2 weeks at room temperature, whitish, cottony, zonate, with diffuse margins. Reverse slightly yellow coloured.

Notes —Based on a megablast search of NCBI’s GenBank nucleotide database, the closest hit using the ITS sequence of KRS70 had the highest similarity to Xylaria sp. ZS-2021d (isolate 67, GenBank MZ648847, Identities = 505/518 (97.49%), 4 gaps (0%)), Xylaria sp. ZS-2021d (isolate 9, GenBank MZ648845, Identities = 505/518 (97.49%), 4 gaps (0%)), Xylaria sp. ZS-2021d (isolate 66, GenBank MZ648846, Identities = 503/518 (97.10%), 6 gaps (1%)), Sordariomycetes sp. (isolate WF147, GenBank HQ130703, Identities = 512/542 (94.46%), 6 gaps (1%)), Xylaria palmicola (isolate 604, GenBank GU322436, Identities = 512/548 (93.43%), 11 gaps (2%) and Xylaria psidii (strain 2508, GenBank FJ037730, Identities = 506/540 (93.70%), 10 gaps (1%)) respectively. Similarly, the closest hit using LSU region sequences of KRS70 had the highest similarity to Xylaria sp. ZS-2021d (isolate 135, GenBank MZ703211, Identities = 869/878 (98.97%), 1 gap (0%), Xylaria oxyacanthae (isolate 132, GenBank MZ703200, Identities = 867/878 (98.75%), 2 gaps (0%)), Xylaria oxyacanthae (isolate 130, GenBank MZ703199, Identities = 866/878 (98.63%), 3 gaps (0%)), Xylaria sp. ZS-2021c (isolate 138, GenBank MZ270312, Identities = 857/866 (98.96%), 1 gap (0%)), and Hypocopra rostrata (strain NRRL 66178, GenBank KM067909, Identities = 865/878 (98.52%), 3 gaps (0%). The closest hit using tub2 gene sequences of KRS70 had the highest similarity to Xylaria sp. ZS-2021d (voucher FCATAS869, GenBank MZ695773, Identities = 346/359 (96.38%), 2 gaps (0%)), Xylaria sp. (7 HMH- 2010g, GenBank GQ495928, Identities = 331/360 (91.94%), 3 gaps (0%)), Xylaria sp. ZS-2021d (voucher FCATAS871, GenBank MZ695774, Identities = 327/359 (91.09%), 1 gap (0%)), Xylaria palmicola (voucher 604 (PDD)), GQ495929, Identities = 331/364 (90.93%), 8 gaps (2%)), and Xylaria oxyacanthae (voucher FCATAS906, GenBank MZ695790, Identities = 303/359 (84.4%), 7 gaps (1%) respectively.

nBLAST analysis of the ITS sequence and tub2 gene sequence showed close similarity with X. ellisii and X. rohrensis , but phylogenetic analysis placed them distantly from X. sridharii . The tree topologies of the single and combined matrices were similar. A phylogenetic tree constructed based on ITS revealed a close relationship with X. palmicola and a combined sequence data set (ITS- tub2) showed a close relationship with X. oxycanthae ( FIGURE 3 ). Xylaria sridharii is phylogenetically related to Xylaria reevesiae , X. palmicola and X. oxyacanthae . Morphologically, X. fissilis is having blackish-brown, linear spikes, two inches high, four to five millimeters wide, stout, tuberous and transversely wrinkled, obtuse, often halved in a longitudinal furrow ( Cesati 1879). Further, X. palmicola and X. oxycanthae which are closely related to X. sridharii are known to associated with dicot seeds and can be differentiated morphologically based on ascospores dimensions viz., X. palmicola ascospores measured (13.5–)14.5–16.5(–18.5) × (6–)6.5–7.5(–8.5) µm and X. oxycanthae ascospores measured (9.5–)10–11.5(–12) × (4–)4.5–5.5(–6) µm ( Ma et al. 2022). X. sridharii is distinguished by the presence of the hirsute stromata, which shows multiple branching (2–4, but rarely recorded up to 6) at the apex, and each branch produces a fertile part, which in turn ends with a thin filiform appendage. Therefore, X. sridharii is distinct from all three Xylaria species in its stromata structures confirming that it is a new species.

Figures

FIGURE 1. Location from where the holotype specimen was collected (Konaje); B–E—Xylaria sridharii developed on the lamina of Coconut leaflet; F—cross-section of stromata (basal bulbous region showing the arrangement of perithecia); G–I—Pure culture of X. sridharii (NFCCI 5117) on PDA medium (12 days old; G & H front view; I reverse view).

FIGURE 2. A–B—Stromata with the branched structure without a hair-like appendage at the apical tip; C–D—cross-section of stromata showing the perithecia with ascocarp and ascospores; E—young immature ascocarp with ascospores; F & G—matured ascocarp with ascospores of Xylaria sridharii (Scale:A & B—100 µm; C–E—50 µm; F & G—20 µm).

FIGURE 3. ML tree with 1000 bootstrap values based on analysis of a combined dataset of ITS & TUB2 for the species of Xylaria constructed using the Tamura 3-parameter method in MEGAX. Bootstrap support values ≥ 50 % are at the nodes. Poronia pileiformis WSP 88113001 was used as an outgroup. The phylogenetic position of Xylaria sridharii is indicated in red font.