Phaeoacremonium chiangmaiense X. Zhang & N. Suwannar., 2025

Phaeoacremonium chiangmaiense X. Zhang & N. Suwannar. sp. nov.

Fig. 6 View Figure 6

Etymology.

“ chiangmaiense ” refers to the location “ Chiang Mai, ” from where the holotype was collected.

Holotype.

CMUB 40065.

Description.

Saprobic on dead twigs of Macadamia sp. Sexual morph: Ascomata 80–165 × 115–170 µm (x ̄ = 136 × 146 µm, n = 20), immersed, solitary, globose to subglobose, dark brown to black, glabrous, ostiole with a long neck, neck straight or flexuous. Perithecial necks 75–160 µm high × 15–35 µm diam. (x ̄ = 119 × 25 µm, n = 20), cylindrical, periphysate, ostiolar canals sulcate. Peridium 18–40 µm wide (x ̄ = 29.4 µm, n = 25), comprising two section layers, the inner section layer composed of hyaline cells of textura prismatica, the outer section layer comprising brown to dark brown cells of textura prismatica. Hamathecium 3.5–5.5 µm wide (x ̄ = 4.6 μm, n = 50), comprising cylindrical, hyaline, septate paraphyses, slightly inflated between the septa near their base and slightly contracted at the septa, longer than the asci. Asci 17–27 × 4–6 µm (x ̄ = 20 × 5 µm, n = 50), 8 - spored, arising in acropetal succession, unitunicate, apedicellate, cylindrical to clavate, apically rounded to truncate. Ascogenous hyphae hyaline, smooth-walled, septate, simple, 4–5 µm (x ̄ = 4.7 μm, n = 10) at the base. Ascospores 4–7 × 1.2–2.5 µm (x ̄ = 5.5 × 2 µm, n = 35), overlapping, hyaline, oblong to allantoid, aseptate, smooth-walled, rounded, and small guttules at both ends. Asexual morph: Undetermined.

Culture characteristics.

Ascospores germinating on PDA within 24 h at 28 ° C, colony on PDA reaching 3 cm diam. after two weeks, culture from above flat, smooth surface, entire edges, white-yellow, low convex at the middle, forming tufts on the surface, wrinkled, reverse white to light reddish-brown from the edge to the center, wrinkled.

Material examined.

Thailand • Chiang Mai Province, 18°52'43"N, 99°13'15"E, 384 m elevation, on a dead branch of Macadamia sp. , 24 November 2023, Xian Zhang, TCMM 19, CMUB 40065 holotype; ex-type living culture, SDBR-CMU 510 , other living culture SDBR-CMU 511 GoogleMaps .

GenBank number.

SDBR-CMU 510 = ITS: PQ 699720, TUB 2: PQ 736689, ACT: PQ 736691, tef 1 - α: PQ 724483, LSU: PQ 699722; SDBR-CMU 511 = ITS: PQ 699721, TUB 2: PQ 736690, ACT: PQ 736692, tef 1 - α: PQ 724484, LSU: PQ 699723.

Notes.

The phylogenetic analyses showed that our isolates of Phaeoacremonium chiangmaiense formed an independent lineage that is basal to three species of Phaeoacremonium ( P. iranianum (CBS 101357, CBS 117114), P. minimum (CBS 246.91, CBS 100397), and P. tuscanum (CBS 123033 )) with 87 % ML and 1.00 PP support (Fig. 5 View Figure 5 ). Phaeoacremonium chiangmaiense (SDBR-CMU 510, ex-type) was compared in ITS, TUB 2, ACT, tef 1 - α, and LSU loci with P. iranianum (CBS 101357), P. minimum (CBS 246.91), and P. tuscanum (CBS 123033) based on nucleotides. The comparison results show that the TUB 2, tef 1 - α, and ACT gene regions exhibit more than 10 % differences (Table 3 View Table 3 ). Based on morphology, P. iranianum , P. minimum , and P. tuscanum were only recorded from asexual morphs, while P. chiangmaiense is recorded from the sexual morph; therefore, comparing these four species morphologically was not possible. Only 13 species of Phaeoacremonium were recorded from sexual morph ( Hausner et al. 1992; Mostert et al. 2006; Hu et al. 2012; Huang et al. 2018; Calabon et al. 2021; Phukhamsakda et al. 2022). Phaeoacremonium chiangmaiense is similar to other Phaeoacremonium species by having black ascomata, with asci arising in acropetal succession, hyaline ascogenous hyphae, and allantoid, reniform ascospores ( Gramaje et al. 2015; Calabon et al. 2021; Phukhamsakda et al. 2022; Senanayake et al. 2023). Phaeoacremonium chiangmaiense can be distinguished from other Phaeoacremonium species by its lack of branched hamathecium, overlapping and oblong ascospores ( Gramaje et al. 2015; Phukhamsakda et al. 2022; Senanayake et al. 2023). Thus, we introduce P. chiangmaiense as a new species based on morphology phylogenetic analysis results.