Chaetomium albiziae M. Mehrabi-Koushki & A. Safi, 2023

Mehrabi-Koushki, Mehdi & Safi, Atena, 2023, Chaetomium albiziae, a new endophytic species from Albizia lebbeck in Iran, Phytotaxa 591 (2), pp. 137-146 : 140-142

Chaetomium albiziae M. Mehrabi-Koushki & A. Safi , sp. nov. ( Fig. 1 )

MycoBank: MB 841114

Holotype: IRAN, Khuzestan Province, Ahvaz, isolated from a living leaf of Albizia lebbeck (Fabaceae) , Oct. 2018, A. Safi (holotype, IRAN 18081F ; ex-type cultures, IRAN 4137C = SCUA-Saf-B10).

Etymology. Species epithet refers to the host genus Albizia from which the holotype was isolated.

Sexual morph: Hyphae hyaline to pale brown, septate, branched. Ascomata perithecioid, superficial, brown to dark brown in reflected light, globose to subglobose, (79–)118–170(–184) × (71–)100–145(–158) μm, 95 % confidence limits = 134–148.5 × 112.2–124.8 μm, (± SD = 141.3 ± 25.5 × 118.5 ± 22.1 μm, n = 50). Ascomatal wall brown, textura angularis in surface view. Terminal hairs seta-like, septate, unbranched, smooth, brown, tapering towards the tips, 2.5–3.8 μm diam near the base. Lateral hairs similar but more flexuous, narrower and shorter. Asci fasciculate, clavate, spore bearing part (20–)22.5–35(–38.75) × 7.5–16.5 μm, stalks 11.25–22.5 μm long, with 8 irregularly-arranged ascospores, evanescent. Ascospores brown to olivaceous brown, ellipsoidal to ovoid, aseptate, biapiculate, bilaterally flattened, with an apical germ pore, (7.5–)10–11.25(–12.5) × 7.5–10 μm, 95 % confidence limits = 10.4–10.9 × 8.1–8.6 μm, (± SD = 10.7 ± 0.8 × 8.3 ± 0.7 μm, n = 50). Asexual morph: not observed.

Culture characteristics—Colonies on OA reaching 60–66 mm after 4 d of incubation at 28 ± 0.5 °C, circular with regular margin, initially white, with age becoming creamy white or slightly pinkish, highly floccose; reverse pinkish white. Colonies on PDA reaching 40–45 mm d after 4 d of incubation at 28 ± 0.5 °C, circular with regular margin, initially pale buff with creamy margin, with age becoming buff with paler margin and sectors, floccose; reverse buff with paler sectors.

Additional materials examined. IRAN, Khuzestan Province; Karoon , isolated from a living leaf of A. lebbeck, Sep 2020 , A. Safi (SCUA-Saf-B10-2) .

Notes: In the phylogenetic tree, C. albiziae is closely related to C. cucumericola , but can be distinguished by single nucleotide polymorphism (SNP) analysis of three ITS, tub2 and rpb2 loci ( Fig. 2 ). This new species and the extype strain of C. cucumericola (CBS 378.71) showed 1 bp difference (0.2 %) across 496 nucleotides of the ITS region, 6 bp difference (1.1 %) across 547 nucleotides of the tub2 region, and 5 bp difference (1 %) across 481 nucleotides of the rpb2 region. Chaetomium cucumericola was established by Wang et al. (2016) to accommodate two sterile strains of the genus Chaetomium (CBS 378.71 and CBS 126777), which formed a well-supported clade within phylogenetic group III, including the related species C. olivaceum Cooke & Ellis , C. subglobosum Sergeeva , and C. undulatulum Asgari & Zare. C. albiziae can be distinguished from these three species by smaller ascomata ( C. olivaceum : 260–440 × 200–360 μm, C. subglobosum : 300–450 × 265–355 μm, C. undulatulum : 230–280 × 185–250 μm) ( Asgari & Zare 2011, Wang et al. 2016b).

Figures

FIGURE 1. Phylogenetic tree constructed from a maximum likelihood analysis based on the combined ITS, tub2 and rpb2 sequences of Chaetomium strains. The tree was rooted to Amesia atrobrunnea (CBS 144684). Bootstrap values obtained in maximum likelihood (ML) and maximum parsimony (MP) analyses equal or greater than 50% and Bayesian posterior probability values (BYPP) equal or greater than 0.95 are shown at the nodes, respectively.

FIGURE 2. Chaetomium albiziae (IRAN 4137C). a–b. Colony on OA (top and reverse). c–d. Colony on PDA (top and reverse). e. Immature Ascomata. f. Mature Ascomata. g. Asci. h. Ascospores. Scale bars: e = 105 μm; g = 200 μm; g–h = 20 μm.