Boeremia albae

Boeremia albae D. Gomdola & Jayaward., sp. nov.

Index Fungorum number: IF 900760; Facesoffungi number: FoF 14377

Etymology: Referring to the host, Morus alba, from which the fungus was isolated.

Diagnosis: Conidial shape variable, and sometimes elongated when compared to other Boeremia species. They form conidial anastomosis tubes in culture.

Associated with leaf spots of Morus alba (Moraceae). Leaf spots circular, dark brown. Sexual morph: Not observed. Asexual morph: Pycnidia forming on PDA, 0.5–1 mm diam., semi-immersed in culture, solitary, globose to subglobose or irregular. Conidiophores reduced to conidiogenous cells. Conidiogenous cells phialidic, hyaline, ampulliform to doliiform, 5.5–7.5 × 2.5–3 μm (x̄ = 6.5 × 2.7 μm, n = 5). Conidia 3.5–11 × 1.5–3.7 μm (x̄ = 5.4 × 2.6 μm, n = 75), hyaline, guttulate, mostly aseptate (occasionally 1-euseptate), smooth-walled, cylindrical or ellipsoidal, sometimes elongated, apex and base broadly obtuse, rarely tapering towards the base. Conidial anastomosis tubes 0.8–1.2 μm diam. (x̄ = 0.95 μm, n = 5), hyaline, smooth-walled. Chlamydospores 5.5–12 × 5.5–8.5 μm (x̄ = 8.7 × 6.3 μm, n = 10), hyaline, globose to subglobose, ellipsoidal or obovoid, smooth-walled, formed terminally or intercalary in chains of two to five.

Culture characteristics: Colonies on PDA reaching approximately 40 mm diam. after 7 days incubation at 25 ◦C, irregular, mycelium flat or effuse with an entire margin, surface smooth, floccose, with fimbriate margins, top and reverse of colony after 7 days greyish white; after 28 days of incubation olivaceous brown to black.

Distribution: Thailand (this study).

Specimen examined: THAILAND, CHIANG MAI: Doi Inthanon National Park, Highland Fisheries Unit, on leaves of Morus alba (Moraceae), 18 Oct 2021, D. Gomdola DGM2-L8B (holotype MFLU 23–0264; isotype BBH 50461). Ex-type living culture MFLUCC 23–0088. GenBank: ITS = OR346922; 28S = OR346889; ACT1 = PP155396; TBB1 = PP729346; RPB2 = OR520271; TEF1 = OR574848.

Additional specimens examined: THAILAND, CHIANG MAI: Doi Inthanon National Park, Highland Fisheries Unit, on leaves of Morus alba (Moraceae), 18 Oct 2021, D. Gomdola DGM2-L6B (MFLU 23–0265). Living culture MFLUCC 23–0089. GenBank: ITS = OR346924; 28S = OR346891; ACT1 = PP155398; TBB1 = PP150336; RPB2 = OR582406; TEF1 = OR574849; DGM2-L7B (MFLU 23–0266; BBH 50462). Living culture MFLUCC 23–0090. GenBank: ITS = OR346923; 28S = OR346890; ACT1 = PP155397; TBB1 = PP150337; RPB2 = OR520272; TEF1 = OR582384.

Notes: The isolates MFLUCC 23–0088, MFLUCC 23–0089 and MFLUCC 23–0090 grouped in a separate subclade with 90 % ML, 73 % MP and 0.91 PP support. This subclade is sister to B. maritima (MFLUCC 18–0411 and MFLUCC 23–0087) with 0.91 PP (Fig. 2). In comparison of the intra-species genetic distance between the three strains of the new species, B. albae, no difference was observed in ITS (508 nucleotides), 28S (860 nucleotides), ACT1 (224 nucleotides), RPB2 (950 nucleotides) and TEF1 (288 nucleotides) matrices, but 1.5 % differences were observed in TBB1 (284 nucleotides).

Comparing the inter-species genetic distance between our new species (MFLUCC 23–0088) and the ex-type of B. maritima (MFLUCC 18–0411), no difference was observed in ITS and 28S, but their inter-species genetic distance accounted for a difference of 2.6 % in TBB1. However, we were unable to compare the genetic distance in ACT1, RPB2 and TEF1 regions with the ex-type of B. maritima as it lacks sequence data for these genes. Nonetheless, when comparing the inter-species genetic distance of the new species (B. albae, MFLUCC 23–0088) and our strain of B. maritima (MFLUCC 23–0087), which has sequence data for all six gene regions, 0.9 %, 2.1 % and 4.3 % differences were observed in ACT1, RPB2 and TEF1 regions, respectively.

The conidiogenous cells of B. albae are up to 7.5 μm long while those of B. maritima are up to 5.5 μm. The conidia of B. albae exhibit variable shapes when compared with B. maritima. The conidia of B. albae are ellipsoidal or obovoid, sometimes elongated while those of B. maritima are ellipsoidal to oblong. Conidia of B. albae can be both slightly longer or shorter (3.5–11 μm) than those of B. maritima (6–10.3 μm). Conidial anastomosis tubes were occasionally observed in B. albae but not in B. maritima. The culture characteristics of B. albae and our strain of B. maritima also vary (Fig. 1).

Following the phylogenetic and morphological species concepts for species recognition documented in Chethana et al. (2021), Jayawardena et al. (2021) and Pem et al. (2021), we establish B. albae as a novel taxon. It is morphologically and phylogenetically distinct from other Boeremia species.