Coniothyrium yuccicola Chaiwan, Jayaward., Bulgakov & K.D. Hyde, sp . nov .

Index Fungorum number: IF 559467; MycoBank number; MB 5597647; Facesoffungi number: FoF 08170; Fig. 1

Etymology – Referring to the host Yucca

Holotype – MFLU 17–2529

Pathogenic on living leaves and peduncle stems of Yucca filamentosa. Asexual morph: Conidiomata 250–450 μm (x̅=329 μm, n=10) diam., superficial on or immersed in the host. Conidiophores not present. Conidiogenous cells lining entire cavity, hyaline, cylindrical, 8±15 (x̅=11.9 μm) 3±8 μm (x̅=5.1 μm), longer in culture than on host plants. Conidiogenesis holoblastic, proliferating percurrently. Conidia cylindrical, broadly rounded at apex, initially somewhat truncate at base, produced deep within the conidiogenous cells, secession rhexolytic, outer wall of conidiogenous cell often remaining on conidium, except at base, eventually disintegrating, olivaceous brown, 3-septate, lightly punctate, (2–)6.6–10. 5(–14)×(1–)2–5(–6) μm (x̅=7.3×3.6 μm, n=40) brown, smooth-walled or verruculose, aseptate, curved, both sides gradually tapering towards the round to slightly acute apex and truncate base, guttulate. Sexual morph: Not observed.

Material examined – Russia, Donetsk People’s Republic, Donetsk City, Donetsk Botanical Garden, flowerbed, on dying peduncle stem and live leaves of Yucca filamentosa L. (Asparagaceae), 20 May 2017, Timur S. Bulgakov, DNK108 (MFLU 17–2529, holotype); ex-type living culture MFLUCC 18–0456.

GenBank numbers – OM235094 (SSU); OM235097(LSU)

Notes – Coniothyrium yuccicola is an asexual morph. Based on our phylogenetic tree this species is closely related to C. concentricum (Fig. 2). Conidia of this species are brown aseptate, bacilliform, ellipsoid and often thick-walled (Fig. 1). Three Coniothyrium species are recorded on Yucca species (Farr and Rossman 2022): Coniothryrium bartholomaei from the USA (Oregon), C. herbarum from the USA (California),  and C. yuccae from Argentina. Coniothyrium bartholomaei was reported as a plant pathogen that caused leaf spots of Yucca in Oregon (USA) (Pscheidt and Ocamb 2018; Barr 1992). Coniothyrium herbarum is known from USA (California) on the leaves of several closely related plants: Dracaena indivisa, Sansevieria sp. and Yucca angustifolia (Cash 1952), however, this species is invalid. Coniothyrium yuccae was found on dead leaves of Yucca gloriosa in Argentina (Buenos-Aires) (Farr 1973). Phaeosphaeriopsis yuccae is another morphologically similar taxon described from living leaves of Yucca filamentosa from Russia, Rostov region, Botanical Garden of Southern Federal University (Tibpromma 2017).

Figure 1 – Coniothyrium yuccicola (MFLU 17–2529, holotype) a Specimen with conidiomata. b Black acervuli. c Brown setae. d Conidiophores with basal parts of setae. e Hyaline conidiogenous cells. f Conidiomata on PDA. g Hyaline conidia. h Germinating conidium. i Appressoria. j Reverse view of the colony. k Upper view of the colony. Scale bars: a=1000 μm, b=500 μm, c=20 μm, d=15 μm, e, f=10 μm

Figure 2 –  Phylogram generated from ML analysis based on combined LSU and SSU sequence data of selected taxa. The combined dataset comprises 41 strains with 1834 characters including gaps. The tree is rooted to Aposphaeria populina (CBS543.70) and Westerdykella capitulum (CBS 337.65). Maximum Likelihood bootstrap values≥65% and BYPP≥0.90 are displayed on the nodes, respectively. Newly introduced taxa are indicated in red. Ex-type and representative strains are in bold