Dothiorella chiangmaiensis Rathnayaka & K.D. Hyde, sp. nov.

MycoBank number: MB; Index Fungorum number: IF; Facesoffungi number: FoF 12894; Figure 2.

Etymology: The epithet chiangmaiensis refers to Chiang Mai Province, where the fungus was collected

Holotype: MFLU***

Saprobic on dead branches of Tamarindus indica. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 445–500 μm high × 460–500 μm diam. (x̄ = 485 × 475 μm, n = 10), pycnidial, solitary, formed in uniloculate stromata, immersed, becoming erumpent at maturity, globose to sub globose, ostiolate. Ostiole 50–85 μm diam., central, papillate. Conidiomata wall 33–83 μm diam., composed of two layers, outer layer composed of thick-walled, dark brown to brown cells of textura angularis, inner layer composed of thin-walled, pale brown to hyaline cells of textura angularis. Conidiophores usually reduced to conidiogenous cells. Conidiogenous cells 6–12 μm × 5–9 μm (x̄ = 9.5 × 7 μm, n = 20), holoblastic, lining the pycnidial cavity, hyaline, cylindrical, discrete, determinate, smooth-walled.  Conidia 30–40 μm ×12–17 μm (x̄ = 36 × 15 μm, n = 20, l/w = 2.4), ellipsoid, straight or slightly curved, rounded at both ends, initially hyaline and aseptate becoming dark brown and 1-septate often while attached to conidiogenous cell, slightly constricted at the septum, guttulate.

Culture characteristics: Conidia germinating on PDA within 24 h. Germ tubes produced at one side of the conidia. Colonies on PDA reaching 1.5–2.5 cm diam. after 6 days at 25 °C, colonies circular in shape, medium dense, flat or effuse, slightly raised, fluffy to fairly fluffy, aerial, black to grey colour in the upper side and black colour in the lower side.

Material examined: Thailand, Chiang Mai, Mushroom Research Centre (MRC), on dead branches of Tamarindus indica (Fabaceae), 10 September 2020, Pahoua Pasouvang, (MFLU ****, holotype), ex-type living culture MFLUCC****.

Note: Dothiorella chiangmaiensis fits within the generic concept of Dothiorella in having 1-septate, brown conidia attached to the conidiogenous cells (Phillips et al. 2005, Dissanayake et al. 2016). Based on the multi-gene phylogeny (ITS, tef1-α and β-tub), our novel taxon formed a distant lineage basal to Dothiorella species in the group A, i.e., Dothiorella acericola, D. alpina, D. citricola, D. magnoliae, D. mangifericola, D. plurivora, D. viticola and D. yunnana with 70% ML and 0.93 BYPP support (Figure 1). Detailed morphological comparison and base pair differences between species in group A and D. chiangmaiensis are provided in Tables 2 and 3, respectively.

Table 2. Synopsis of morphological characters of asexual morphs among the Dothiorella chiangmaiensis and species in group A.

Species Conidia   References
Size

(μm)

 Average

(μm)

 Ratio (L/W)        
Dothiorella acericola 17–22(–23) × 7–10(–13) 20.8 × 9.2 2.2 dark brown, slightly constricted at the septum, smooth-walled Phookamsak et al. (2019)
D. alpina 22–25(–28) × 10–12(–13) 24.4 × 11.1 2.19 brown to dark brown, not constricted at the septum, smooth-walled Hyde et al. (2020)
D. chiangmaiensis 30–40 ×12–17 36 × 15 2.4 dark brown, slightly constricted at the septum, guttulate This study
D. citricola (23.7–)24 – 27(– 28) × (9.5 –)10 –12(–14.1) 25.8 ± 1.1 × 12.2 ± 1.3 2.1 ± 0.2 brown, occasionally slightly constricted at the septum,  externally smooth, internally finely verruculose Abdollahzadeh et al. (2014)
D. magnoliae (16.00–) 20.63–22.50

(–31.35) × (8.14–) 10.87–12.03(–15.55)

 21.56 × 11.45 1.88 brown, always deeply constricted at the septum, externally smooth, internally finely verruculose You et al. (2017)
D. mangifericola (14.4–)17–22(–22.5) × (6.3–)8–10(–11) 19 ± 1.6 × 9 ± 0.9 2.1 ± 0.2 brown, occasionally slightly constricted at the septum, externally smooth, internally finely verruculose Abdollahzadeh et al. (2014)
D. plurivora (18–)20–25(–27) ×

(8.9–)10–13(–14.4)

 22.5 ± 1.7 × 11 ± 1.1 2.1 ± 0.2 brown, occasionally slightly constricted at the septum, externally smooth, internally finely verruculose Abdollahzadeh et al. (2014)
D. viticola (16–)20.2–20.6(–26) ×  (7–)9.2– 9.4(–12) 20.4 ± 0.1 × 9.3 ±

0.1

 2.2 ± 0.02 brown, occasionally slightly constricted at the septum, externally smooth, internally finely verruculose Luque et al. (2005)
D. yunnana (18.4–)19.6–21(–22.2) × (8.1–)8.6–9.2(–9.6) 20.3 ± 1.5 × 8.9 ± 0.9 2.3 ± 0.2 brown, occasionally slightly constricted at the septum, externally smooth Zhang et al. (2016)

Table 3. Base pair comparison of Dothiorella chiangmaiensis (MFLUCC****) and species in group A (without gaps).

Species Strain no. ITS tef1-α
Dothiorella acericola KUMCC 18-0137 2.5% (12/472 bp) 20.1% (34/169 bp)
D. alpina CGMCC 3.18001 3.4% (15/447 bp) 18.7% (40/213 bp)
D. citricola ICMP16828 2.3% (11/472 bp) 17.7%  (37/208 bp)
D. magnoliae CFCC 51563 2.8% (12/436 bp) 17.6% (37/210 bp)
D. mangifericola CBS 121760 2.5% (12/472 bp) 22.4%  (40/178 bp)
D. plurivora IRAN1557C 2.5% (12/472 bp) 18.4%  (39/211 bp)
D. viticola WA10NO01 2.5% (12/472 bp) 20.2% (39/193 bp)
D. yunnana CGMCC 3.1800 2.6% (12/460 bp) 17.6% (37/210 bp)

Among the D. chiangmaiensis and group A species, only D. chiangmaiensis has guttulate conidia. Compared to other species in group A, our novel taxon has the highest L/W ratio (2.4) (Table 2). Therefore, our novel taxon is distinguished from species in group A by having the largest conidia with guttules. Based on distinct morphology and phylogenetic evidence, we introduced D. chiangmaiensis as a new species in Dothiorella.