Allophoma yuccae A. Ahmadpour, Z. Heidarian, Z. Alavi, F. Alavi & Y. Ghosta, sp. nov.

Index Fungorum number: IF 900340; MycoBank number: MB 900340; Facesoffungi number: FoF 14169; Fig. 1

Etymology – based on the host plant genus, Yucca.

Pathogenic on the leaf spots of Yucca gigantean Lem. Lesions up to 10–15 mm diam., spread on the upper surface, scattered, distinct, irregular, brown to dark brown. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata (100–)130–250 × (100–)120–240 μm, pycnidial, semi-immersed to immersed, mostly solitary, rarely aggregated, scattered, globose to subglobose, pale brown to brown, thin-walled, glabrous, ostiolate, papillate. Papilla 1(–2), elongate, short, open with wide ostiole. Pycnidial wall 10–35 μm thick, pseudoparenchymatous, 3–5 layered, composed of oblong to isodiametric cells, pale brown. Conidiogenous cells 4–6(–8)×4–8 μm, phialidic, hyaline, smooth, globose to ampulliform. Conidia 4–7 × 2–3 μm (x=4.5×2.5 μm, n=50), ellipsoidal to oblong, occasionally ovoid, with rounded ends, hyaline, smooth and thin-walled, aseptate, with 1–3-polar guttules.

Culture characteristics – Colonies on PDA reaching 60–67 mm diam. after 7 days at 25 °C, smooth margin, sparse aerial mycelia, floccose, olivaceous green at the center, white at the margin; reverse white to pale brown. Colonies on MEA reaching 55–60 mm diam. after 7 days at 25 °C, filiform margin, sparse aerial mycelia, floccose, surface white to pale brown; reverse white, pale brown at the center. Colonies on OA reaching 55–60 mm diam. after 7 days at 25 °C, smooth margin, surface white to pale olivaceous, floccose aerial mycelia, abundant production of pycnidia, conidial matrix visible; reverse buff, with pale olivaceous near the center. Colonies on CMA reaching 50–56 mm diam. after 7 days, smooth margin, sparse aerial mycelia, white to pale olivaceous; reverse with pale olivaceous near the center. NaOH test negative.

Material examined – Iran, West Azarbaijan Province, Miyandoab City, on leaves of Yucca gigantean (Asparagaceae), 20 September 2021, A. Ahmadpour, (IRAN 18108F, holotype), ex-type culture, IRAN 4238C; ibid. East Azarbaijan Province, Maraghe City, on Y. gigantean, 30 September 2021, A. Ahmadpour, living culture, FCCUU 1901.

GenBank numbers – ITS: OP805927, OP805928, rpb2: OP838915, OP838916, β-tubulin: OP838917, OP838918.

Notes – Our collection is phylogenetically closely related to Allophoma hayatii (CBS 142859 and CBS 142860) with statistical support BI=0.96 and ML=95% (Fig. 2). A comparison of nucleotide differences in ITS, rpb2 and β-tubulin indicates that our isolate (IRAN 4238C) differs from A. hayatii (CBS 142859) by 1.03% in ITS and 1.91% in rpb2 while β-tubulin sequences are identical. Morphologically, our collection differs from A. hayatii by pycnidia with single ostiole, aseptate conidia and absence of chlamydospores formation while A. hayatii has 1–3-ostiole per pycnidium, 1-septate conidia and chlamydospores formation (Babaahmadi et al. 2018). Furthermore, the shape and size of pycnidia and conidia of our collection are similar to A. labilis and however, differs from A. labilis by NaOH test (reddishbrown discoloration in A. labilis and negative in our collection) (Boerma et al. 2004). A comparison of nucleotide difference in ITS, rpb2 and β-tubulin loci of our collection and A. labilis shows 0.83% in rpb2, 2.8% in β-tubulin and no difference in ITS. Therefore, we introduce our collection as A. yuccae. 

Figure 1 – Allophoma yuccae (IRAN 4238C, holotype). a Host plant. b–d Symptoms on leaves. e Colony on PDA after 7 days (front and revers). f Colony on MEA after 7 days (front and revers). g Colony on OA after 7 days (front and revers). h Colony on CMA after 7 days (front and revers). i–j Pycnidia producing on OA. k–l Pycnidia producing on PDA. m–o Pycnidia. p–r Conidiogenous cells. s Conidia. Scale bars: m–o=50 μm, p–s=10 μm

Figure 2 – Phylogenetic tree inferred from Bayesian Inference (BI) of combined dataset of ITS, rpb2 and β-tubulin of Allophoma species. Twenty two strains are included in the combined analyses which comprise a total of 1384 characters (ITS=455 bp, rpb2=596 bp and β-tubulin=333 bp) and inferred substitution models were K80+I (ITS), SYM+G (rpb2), and GTR+G (β-tubulin). Bootstrap support obtained in a complementary Maximum Likelihood (ML) analysis with RAxML using 1000 replicates. The Bayesian posterior probabilities (BI)>0.50 and Maximum Likelihood bootstrap support (ML) values>50% are given at the nodes (BI/ML). The tree was rooted to Stagonosporopsis loticola (CBS 562.81) and newly identified strains are in blue bold and ex-type strains are in bold. The scale bar indicates the number of nucleotide substitutions