Phyllosticta ovalina H.X. Wu & C.L. Gong.

Gong, Cui-Ling, Wu, Hai-Xia, Li, Jin-Chen & Song, Jia-Yu, 2024, Morphological and multi-gene phylogenetic analyses of two new species of Phyllosticta (Phyllostictaceae, Botryosphaeriales) from Southwestern China, Phytotaxa 653 (1), pp. 20-36 : 29

Phyllosticta ovalina H.X. Wu & C.L. Gong. sp. nov. Fig. 3

Fungal Names: FN 571912

Etymology— ovalina = oval, in reference to its oval ascospores.

Holotype — IFRD 9478

Saprobic on leaf litter. Sexual morph: Black ascomata observed on leaf surface.Ascomata125–215 μm (x = 164 μm, n = 20), semi-buried, globose, black, carbonaceous, uneven surface, raised centre, irregularly rounded, domed above the leaf surface, releasing ascospores at maturity by dehiscence and forming a central ostiole. Peridium thin, composed of brown to dark brown cells of textura angularis. Asci 45–110 × 10–20 μm (x = 68 × 16 μm, n= 20), 8-spored, bitunicate, clavate to broadly ellipsoid, with a broad, gradually tapering, obtuse apex, with an apical ring and a chamber diameter of 2.2 μm. Ascospores 15–20 × 5–10 μm (x = 17 × 8 um, n= 20), biseriate, ovoid to ellipsoid, obtusely rounded at both ends, widest at the apex and slightly narrower at the base, with a large central guttle, a few ascospores with slightly appendage at the apex or base, and generally without appendage at both ends. Asexual morph: Not observed.

Material examined— CHINA. Yunnan Province: MouDing County, HuaFoShan National Nature Reserve, on dead leaves of an unidentified plant, 25°18'N – 25°31'N, 101°25'E – 101°42'E, 2360 m elev., October 2021, H.X. Wu, J.C. L & J.Y. Song ( IFRD 9478, holotype).

Notes: In the phylogenetic tree P. ovalina is placed in the P. cruenta species complex ( Fig. 1 ), which contains 21 species ( Table 1 ), with only two sexual stage species, P. abieticola , and P. rubella being reported ( Wikee et al. 2013b). P. ovalina differs significantly from these two sexual stage species in morphological characters. The ascospores of P. abieticola are multiguttulate, widest at the centre, limoniform with obtuse ends. Ascospores of P. rubella are limoniform, widest in the upper third, whereas ascospores of P. ovalina are ovoid and widest at the apex ( Table 2 ).

The morphological distinctions were further corroborated by the phylogenetic analysis, indicating that P. ovalina does not cluster with these two sexual species ( Fig. 1 ). The phylogenetic analyses reveal a close relationship between P. ovalina and P. hubeiensis ( Fig. 1 ), yet P. ovalina forms a distinct branch with strong support (100%/1.00, BS/ BYPP). Furthermore, NCBI blast results of the ITS sequences of P. ovalina (holotype) also support our findings. P. ovalina exhibits only 95.37% sequence identity with P. hubeiensis (query cover = 35%), which does not align with it being a sexual stage of P. hubeiensis . Both P. ovalina and P. abieticola share only 85.10% sequence identity (query cover = 36%), while P. foliorum demonstrates only 86.29% (query cover = 36%) and 85.95% (query cover = 36%) with P. podocarpicola ( Table 3 ). Consequently, P. ovalina is classified as a new species within the genus Phyllosticta .

Figures

FIGURE 1. Phylogram of Phyllosticta resulting from a maximum likelihood analysis based on a combined matrix of ITS, LSU and TEF1 loci. The tree is artificially rooted to B. obtusa (CMW 8232). ML bootstrap values (left, ML-BS ≥ 50%) and Bayesian posterior probabilities (right, BYPP ≥ 0.9) are given at the nodes. New species of this study are indicated using red font and their associated support is bolded.

FIGURE 3. Phyllosticta ovalina (IFRD 9478, holotype). a. Microfungi on leaf litter. b–c. Ascomata on leaf surface. d–e. Vertical section of ascomata. f–i. Asci. j–n. Ascospores (i in cotton blue). Scale bars: b = 500 μm, c = 100 μm, d = 50 μm, f–i = 20 μm, j–n = 10 μm.