Phyllachora yuanjiangensis H.X. Wu & J.C. Li., 2023

Li, Jin-Chen, Wu, Hai-Xia & Song, Jia-Yu, 2023, Two new Phyllachora species in Southwest China, Phytotaxa 578 (3), pp. 275-285 : 282-283

Phyllachora yuanjiangensis H.X. Wu & J.C. Li. sp. nov. Fig. 3

MycoBank: 845540

Etymology— Epithet derived from the type locality.

Holotype — IFRD9466

Parasitic on leaves and stems of Arundinella setosa (Poaceae) . Sexual morph: Stromata 360–750 × 105–195 μm (x = 570 × 147.5 μm, n = 10), fusiform or cymbiform, domed above the leaf surface, amphigenous, scattered, sometimes gregarious, like black nevus, black and carbonaceous. Section of stroma 190–340 μm high, multilocular, peridium, composed of brown to dark brown cells of textura angularis. Paraphyses 2–3 μm wide, numerous, persistent, filiform, unbranched, aseptate, many guttules, slightly longer than asci. Asci 71–112 × 11–22 μm (x = 84.6 × 13.2 μm, n = 20), thin-walled, 8-spored, persistent, cylindrical to clavate, apex obtuse, with pedicel. Ascospores 15–21 × 7–9 μm (x = 17.9 × 8.3 μm, n = 20), 1-seriate, tear-shaped, rounded at the apex, tapered at the base, hyaline, aseptate, verrucous, with guttules and a mucilaginous sheath. Asexual morph: Not observed.

Material examined— CHINA. Yunnan Province: Yuanjiang County, on stems and leaves of Arundinella setosa , 101.47°E, 23.27°N, 1532.65 m, 27 November 2021, H . X. Wu & J. C . Li. IFRD9466 , holotype . GenBank accession numbers: LSU: OP359417 ; ITS: OP359399 ; SSU: OP359400

Note: In the phylogenetic tree ( Fig. 1 ), P. yuanjiangensis is closely related to P. arundinellae and P. xinpingensis . P. yuanjiangensis and P. arundinellae both occur on Arundinella sp. Morphologically, the asci and ascospores of P. yuanjiangensis are longer and wider than those of P. arundinellae (asci 71–112 × 11–22 μm vs 70–100 × 7–10 μm, ascospores 15–21 × 7–9 μm vs 10–18 × 5–8.5 μm). The ascospores of P. yuanjiangensis are tear-shaped, rounded at the apex, tapered at the base, while P. arundinellae is narrowly oval to ovoid. Differences in morphological characteristics and their hosts are also supported by the phylogenetic tree. Four Phyllachora species have been recorded on Arundinella spp. , namely P. arundinellae , P. graminicola , P. graminis , and P. shiraiana . P. yuanjiangensis can be distinguished from these species by the shape of its ascospores. The closest hits using LSU and ITS sequences had the highest similarity to P. arundinellae isolate MHYAU:108 (GenBank LSU: MG269815 , identities = 809/899 (90%); ITS: MG269761 , identities = 440/534 (82%)) and P. graminis MM-166 (GenBank ITS: KX451869 , identities = 317/556 (57%)).

P. yuanjiangensis had the highest similarity to P. xinpingensis IFRD 9465 (GenBank LSU: OP359416 , identities = 885/899 (98%); ITS: OP359399 , identities = 496/519 (96%)) but these two species can be distinguished by the host plants and asci length. A synopsis of P. yuanjiangensis and other Phyllachora species recorded from Arundinella spp. is provided ( Table 2).

Figures

FIGURE 1. Maximum likelihood phylogenetic tree based on three nuclear markers (LSU, ITS, SSU). Support values are ML bootstrap values based on 1000 replicates and posterior probabilities from a Bayesian analysis. Bootstrap values of ML BP> 50% are shown on the left, while values of Bayesian PP> 0.50 are shown on the right. Newly introduced species are in bold and red, followed by the host of the species behind its strain number.

FIGURE 3. Phyllachora yuanjiangensis (IFRD9466, holotype). a. Black spots on Arundinella setosa (Poaceae). b, c. Stromata. d. Vertical section of ascomata. e. Paraphyses. f–i. Asci (i in cotton blue). j–m. Ascospores (l in cotton blue, m with gelatinous sheath in ink). Scale bars: c = 200 μm, d = 100 μm, e–j = 20 μm, k–m = 10 μm.