Dothiorella macadamiae X. Zhang & N. Suwannar., 2025

Dothiorella macadamiae X. Zhang & N. Suwannar. View in CoL sp. nov.

Figs 3 View Figure 3 , 4 View Figure 4

Etymology.

“ macadamiae ” refers to the host plant genus Macadamia.

Holotype.

CMUB 40066.

Description.

Saprobic on dead twigs of Macadamia sp. Sexual morph: Ascomata 80–120 × 160–220 µm (x ̄ = 100 × 193 µm, n = 10), immersed, visible as dark dots on the host surface, under to clypeus, solitary, uni-loculate, ampulliform, papillate, without ostiole. Peridium 50–190 µm wide (x ̄ = 95 µm, n = 25), comprising three section layers, the inner section layer composed of hyaline cells of textura angularis, the outer section layer with brown to dark brown cells of textura angularis, and the outermost layer of cells surrounding the ascomata is composed of brown cells of textura prismatica. Hamathecium 4.5–8.5 µm wide (x ̄ = 6.5 μm, n = 30), comprising cylindrical, hyaline, septate, cellular pseudoparaphyses. Asci 110–235 × 23–38 µm (x ̄ = 173 × 32 µm, n = 30), 6–8 - spored, bitunicate, clavate to broadly fusoid-ellipsoid, with furcated pedicel, apically rounded, with a well-developed ocular chamber. Ascospores (27 –) 30–37 (– 40) × 14–19 µm (x ̄ = 33 × 17 µm, n = 55), overlapping, uniseriate, oval to ellipsoid, hyaline to yellowish brown, aseptate when young, becoming brown to dark brown, 1 - or 2 - septate at maturity, slightly constricted at the septum, smooth-walled, granular, with mucilaginous polar appendages at one or both ends. Asexual morph: Conidiomata pycnidial produced on PDA within seven weeks, solitary or aggregated, superficial, brown, hairy, globose to subglobose, covered with hyphal hairs, unilocular. Conidiophores reduce to conidiogenous cells. Conidiogenous cells holoblastic, discrete, cylindrical, hyaline, smooth-walled, proliferating percurrently. Conidia 19–26.5 × 10–13.5 µm (x ̄ = 22.6 × 11.2 µm, n = 50), hyaline and aseptate when immature, brown to dark brown and one-septate when mature, oblong to ovoid, granular, one end obtuse to slightly rounded ends, one cell slightly wider or same width. Chlamydospores hyaline to brown, branched, with thickened, septate, brown to dark brown at the septa.

Culture characteristics.

Ascospores germinating on PDA within 24 h at 28 ° C, colony on PDA reaching 9 cm diam. after two weeks at 28 ° C, rough surface, hairy, cottony, and pale olivaceous grey from above, and grey to black in reverse.

Material examined.

Thailand • Chiang Mai Province, Doi Saket District , 18°52'43"N, 99°13'15"E, 384 m elevation, on a dead branch of Macadamia sp. , 24 November 2023, Xian Zhang, TCMM 25, CMUB 40066 , holotype; ex-type living culture, SDBR-CMU 512 , other living culture SDBR-CMU 513 GoogleMaps .

GenBank number.

SDBR-CMU 512 = ITS: PQ 699724, tef 1 - α: PQ 758592, TUB 2: PQ 736693; SDBR-CMU 513 = ITS: PQ 699725, tef 1 - α: PQ 758593, TUB 2: PQ 736694.

Notes.

In the phylogenetic analyses, our isolate D. macadamiae forms an independent branch sister to D. albiziae and D. thailandica with 57 % ML and 1.00 PP support (Fig. 1 View Figure 1 ). Based on the BLASTn results of ITS sequences of our strain (SDBR-CMU 512, ex-type), it is 99.64 % similar to D. oblonga (CBS 121765); the tef 1 - α result is similar to D. dulcispinae (CMW: 36462) with 90.11 %, and the TUB 2 result matched with D. albiziae ( MFLU 22-0093 ) with 98.83 % similarity. Our isolates of D. macadamiae formed an independent branch sister to D. albiziae and D. thailandica with the ML bootstrap support of 57 % (Fig. 1 View Figure 1 ). We carried out the PHI test to confirm the novelty of our new taxon and found no significant recombination event between our strain and the closely related taxa (Φw = 0.902) (Fig. 2 View Figure 2 ). Also, our species (SDBR-CMU 512) was compared in ITS, tef 1 - α, and TUB 2 with D. albiziae ( MFLUCC 22-0057 ) and D. thailandica ( MFLUCC 11-0438 ) (Table 2 View Table 2 ) and found that the tef 1 - α gene shows more than 20 bp difference. Morphologically, D. macadamiae differs from D. albiziae by having a bigger (19–26.5 × 10–13.5 µm vs. 14–18 × 6–8 μm) and one cell slightly wider or the same width conidia; they share similar conidia, being oblong to ovoid ( Rathnayaka et al. 2022). Dothiorella macadamiae is distinguished from D. thailandica by having bigger (19–26.5 × 10–13.5 µm vs. 15–20 × 6.5–8 μm), granular, oblong to ovoid conidia but having similar hyaline conidiogenous cells ( Liu et al. 2012). Dothiorella albiziae and D. thailandica have been recorded from their asexual morph. Therefore, we could not compare the sexual morphological characteristics of D. macadamiae with those of the two species. We introduce D. macadamiae as a new species based on morphology, nucleotide comparisons, and phylogenetic analyses.