Phyllosticta citrichinaensis
Phyllosticta citrichinaensis X.H. Wang, K.D. Hyde & H.Y. Li [as 'citrichinaensis'], Fungal Diversity Res. Ser. 52(1): 215 (2012)
MycoBank: MB 561072
Pycnidia 100–200×100–200 μm, niger, globosa vel subglobosa, interdum pyriformis, cum irregular hypha excrescente superficie in pycnidialia; ostiolo unico; Paries pycnidii capere plures stratosis, crassa ad 58 μm, interior layer constans cell tenuis layers. Cellulae conidiogenae 6– 12 (−15) × 2–5 μm, holoblasticae, phialidicae, breviter cylindricae, lageniformes, singulae, hyalina, tenui-muratas, laevia. Conidia (7–)8–12(−13) × 6–9 μm, elliptica vel ovoidea, utrinque rotundata, singulae, muratis-levi, strato mucoso circumdantia, (0.3–)0.5–1(−1.2) μm, ferens unus, hyalina, ramosa, flexibilis, apicalis (12–)14–26(−56) μm longa praedita. Spermatia hyalina, extremis tumidis bacilli, 7–9 × 1–2 μm.
Etymology. Named after the host, Citrus, and country from which it was isolated, China.
Pycnidia 100–200 × 100–200 μm, black, globose or subglobose, sometimes pyriform, with irregular hyphal outgrowths on the surface, with a single ostiole; pycnidial wall comprising several layers, up to 58 μm thick, inner layer consisting of thin cell layers. Conidiogenous cells 6–12(−15) × 2–5 μm, holoblastic, phialidic, short cylindrical, lageniform, unicellular, colourless, thin- walled, smooth. Conidia (7–)8–12(−13) × 6–9 μm, ellipsoid to ovoid, with rounded ends, unicellular, thin, smooth-walled, pomiform, colourless, enclosed in a thin mucilaginous sheath, (0.3–)0.5–1(−1.2) μm thick, and bearing a single, hyaline, unbranched, straight to flexible, attenuated, mucoid apical appendage, (12–)14–26(−56) μm long; mean conidium length /width ratio =1.39 : 1. Spermatia hyaline, bacilliform with ends swollen, 7–9 × 1–2 μm. Ascomata 100–300 × 100–200 μm, subglobose to pyriform, often irregularly in shape, with short irregular hyphal outgrowths on the surface, colorless inner layer, outer wall consisting of several layers, 20–47 μm thick. Asci 42–81 × 10–14 μm, 8- spored, subclavate to cylindrical, wall thickened and bitunicate. Ascospores (13–)14–20 (−21)× (6–)7–8(−9) μm, biseriate, hyaline, unicellular, multiguttulate, fusiform to ellipsoid, wider at the mid region; both ends rounded with gelatinous caps.
Specimens examined China, Guangdong Province, Meiz- hou, on leaf of Citrus maxima as brown spot, May 2010, X. H. Wang (ZJU 201006, holotype), culture ex-type, ZJUCC201085 = CGMCC3.14302 = CBS130529; China, Guangdong Province, Meizhou, on leaf of C. maxima as brown spot, May 2010, X.H. Wang, ZJUCC201086 = CGMCC3.14303 = CBS 129763; China, Shaanxi Province, Chenggu, on leaf of C. reticulata as red-brown protuberant freckle, May 2010, X.H. Wang, ZJUCC2010100 = CBS 129764.
Cultural characteristics On PDA, surface olivaceous greenish, with multiple annular ridges on the surface, with entire edge, brown at margin; underneath olivaceous-black with obvious annular ridges. On CMA, surface light chocolate, with annular ridges on surface, deep clefted and radial at the edge of colonies, olivaceous-green at margin; underneath olivaceous-black to olivaceous-grey and obvious annular ridges. On OA, regular, surface olivaceous-grey, with entire edge, olivaceous-black at margin; underneath olivaceous-grey to olivaceous-black, aerial mycelium sparse, lacking yellow pigment in the medium. On MEA, irregular, surface olivaceous greenish, with multiple annular ridges on surface, with lobed edge; underneath olivaceous-black to olivaceous-grey.
Temperature requirements After 14 d in a 12/12 h photoperiod, maximum growth diameter was achieved at 24°C on PDA (49 mm), the growth rate was 3.8 ± 0.34 mm per day; a weak growth was observed at 4°C or 34°C, and no growth at 37°C. PDA was the optimum medium for growth of Phyllosticta citrichinaensis, followed by MEA (44 mm, 14 d).
Biochemical characteristics: Three representative isolates (CBS129763, CBS129764 and CBS130529) of P. citrichinaensis obtained from citrus were tested for their ability to utilize sucrose, fructose, galactose, mannitol, sorbitol, glucose or maltose (1% w/v) as a sole carbon source. As comparing to the other Phyllosticta species from Citrus, P. citrichinaensis showed very weak growth on the media with these carbon sources, with maltose being the best.
Notes: Phyllosticta citrichinaensis differs from the other four Phyllosticta species associated with citrus in its morphological and cultural characteristics. Its conidia are smaller and rounder. The mucoid sheath of P. citrichinaensis is thinner than that of P. capitalensis and P. citribraziliensis, but similar to that of P. citricarpa and P. citriasiana. The conidial appendages of P. citrichinaensis are longer than those of the four other Phyllosticta species. Phyllosticta citrichinaensis. has larger ascospores as compared to P. citricarpa and P. capitalensis. In culture, P. citrichinaensis can be distinguished from P. citricarpa, P. citriasiana and P. capitalensis by producing colonies with multiple annular ridges on PDA, cornmeal agar (CMA), and malt extract agar (MEA), and not producing yellow pigment in OA.
Fig. 1 Morphology of Phyllosticta citrichinaensis (CGMCC 3.14302, culture ex-type). a–b Pycnidia forming on PNA; c Conidiogenous cells giving rise to solitary conidia; d and e Conidia with mucoid sheath and apical mucilaginous appendage; f Spermatial state; g and h Immature asci and mature asci with 8 ascospores; i Ascospores. Scale bars =5 μm