Phytopythium nanjingense Jia J. Chen & X.B. Zheng, 2019

Chen, Jia-Jia, Feng, Hui, Wang, Yuan-Chao & Zheng, Xiao-Bo, 2019, Phytopythium nanjingense sp. nov. (Pythiaceae, Peronosporales) from southern China based on morphological and molecular characters, Phytotaxa 403 (3), pp. 239-247 : 242-244

Phytopythium nanjingense Jia J. Chen & X.B. Zheng , sp. nov. ( Figs. 2–3 )

MycoBank no.: MB 822140

Pp. nanjingens e differs from congenerics in its aquatic habit, heterothallic sexuality, ellipsoid, but mostly obpyriform to ovoid-obpyriform shape, internally or internally nested proliferating sporangia with conspicuous apical papillae, smooth oogonia, hypogynous antheridia, filamentous antheridial cells, and plerotic or nearly plerotic and thin-walled oospores (0.5–1.6 μm).

Type.— CHINA. Jiangsu Prov.: Nanjing, Zixiahu Park, alt. 45 m, 118.839°E, 32.061°N, from lake water, 1 November 2016, Chen 218 (holotype NJAU, isotypes BJFC, JAFLA). The isolate was also maintained in freeze-dried cultures.

Known distribution—A rare species spread in subtropical regions of China.

Etymology.— Nanjingense (Lat.): referring to the location in China where the holotype was isolated.

Colonies submerged, with rosette pattern on 10% V8A ( Fig. 2 ). Average growth rates 4 mm day−1 at 15°C, 7 mm day−1 at 20°C, 10 mm day−1 at 25°C, 11 mm day−1 at 30°C, 3 mm day−1 at 35°C, but when returned to room temperature both of them started to grow again. Cardinal temperatures: minimum 11°C, optimum 30°C, maximum 38°C. Main hyphae hyaline, aseptate, up to 5.0 μm wide ( Fig. 3a ). No hyphal swellings. Sporangia ellipsoid, mostly obpyriform to ovoid-obpyriform ( Fig. 3 b-d), terminal with conspicuous apical papillae and internal or internal nested proliferation ( Fig. 3 e-f), 21–35 × 15–25 (mean 27.5 × 21.5) μm in diameter. Heterothallic; oogonia globose, smooth, terminal, 17.5–30 (mean 25.5) μm in diameter. Antheridia hypogynous, one to three per oogonium ( Fig. 3 g-j); antheridial stalks unbranched; antheridial cells filamentous. Oospores plerotic or nearly plerotic, globose, 15–27.5 (mean 22.5) μm in diameter, hyaline. Oospore wall 0.5–1.6 (mean 1.1) μm thick.

Additional specimens examined. — CHINA. Jiangsu Prov.: Nanjing, Zixiahu Park , alt. 45 m, 118.838°E, 32.062°N, from lake water, 1 November 2016, Chen 216 (paratypes, NJAU, BJFC, JAFLA) ; the Sun Yat-sen Mausoleum , alt. 125 m, 118.854°E, 32.056°N, from lake water, 18 September 2016, Chen 172 (paratypes, NJAU, JAFLA). The isolates were also maintained in freeze-dried cultures .

Figures

FIGURE 2. Colony of Phytopythium nanjingense (Chen 218) on 10% V8A at 25°C after five days incubation.

FIGURE 3. Asexual and sexual reproductive bodies of Phytopythium nanjingense (Chen 218). a: Mycelium. b: Ovoid-obpyriform sporangium with conspicuous apical papillae. c: Ellipsoid sporangium with conspicuous apical papillae. d: Obpyriform sporangium. e: Internally nested proliferation. f: Internal proliferation. g-h: Globose, smooth and terminal oogonia. i: Clustering of several filamentous antheridial cells around the oogonium. j: Plerotic oospore. Scale bars: 10 μm.