Conidiobolus bifurcatus B. Huang & Y. Nie, 2020

Nie, Yong, Cai, Yue, Gao, Yang, Yu, De-Shui, Wang, Zi-Min, Liu, Xiao-Yong & Huang, Bo, 2020, Three new species of Conidiobolus sensu stricto from plant debris in eastern China, MycoKeys 73, pp. 133-149 : 133

Conidiobolus bifurcatus B. Huang & Y. Nie sp. nov. Figure 2

Typification.

China, Jiangsu: Nanjing, Laoshan National Forest Park, 32°6'7"N, 118°36'17"E, from plant debris, 1 Dec 2018, Y. Nie and Y. Gao (holotype HMAS 248359, ex-holotype culture CGMCC 3.15889 = RCEF 6551, GenBank: nucLSU = MN061285; TEF1 = MN061482; mtSSU = MN061288).

Etymology.

bifurcatus (Lat.), referring to secondary conidiophores often branched at the tip to form two short stipes, each bearing a secondary conidium.

Ecology and distribution.

Plant debris in Jiangsu Province, China.

Description.

Colonies on PDA at 21 °C for 3 d, opaque, white, reaching ca. 2 mm in diameter, with many small colonies around the periphery due to discharged conidia. Mycelia colourless, 8-11 μm wide, rarely branched and non-septate when young, often septate and distended to a width of 10-27 μm after 5 d. Primary conidiophores arising from the hyphal segments, colourless, 38-254 × 7.5-12 μm, unbranched and producing a single globose conidium, without widening upwards near the tip. Primary conidia forcibly discharged, globose to subglobose, 2-40 × 2-33 μm, with a papilla more or less tapering and pointed, 7-11 μm wide at the base, 3-12 μm long. Secondary conidiophores arising from the primary conidia, often branched almost at the tip, forming two short stipes each bearing a secondary conidium. Secondary conidia similar to, but smaller than the primary ones, mostly forcibly discharged, occasionally falling off and leaving a relic of the secondary conidiophores. On 2 % water agar, microconidia produced readily, globose to ellipsoidal, 7-12 × 6-9 μm. Zygospores homothallic, usually formed between adjacent segments of the same hypha after an incubation of 5-7 d at 21 °C on PDA, smooth, mostly globose, 25-40 μm in diameter, with a 1.5-3 μm thick wall.

Notes.

Conidiobolus bifurcatus sp. nov. is characterised by its secondary conidiophores, which are often bifurcated near the tip and bear a secondary conidium on each stipe. Morphologically, it is allied to Conidiobolus mycophilus Srin. & Thirum., which has smaller primary conidia ( Srinivasan and Thirumalachar 1965). It appears to be similar to C. incongruus Drechsler and C. mycophagus Srin. & Thirum. in the size of primary conidia and zygospores and the formation of microconidia, but different in its longer primary conidiophores ( Drechsler 1960; Srinivasan and Thirumalachar 1965). However, it is distantly related to these two species in the molecular phylogenetic tree. Instead, it is phylogenetically closely related to C. brefeldianus Couch (Figure 1 : MP 71/ML 89/BI 1.00), but morphologically distinct by its larger primary conidia and zygospores ( Couch 1939).

Figures

Figure 1. Phylogenetic tree of Conidiobolus s. s. reconstructed by maximum likelihood analyses of nucLSU, mtSSU and TEF 1 sequences, with six Conidiobolus s. l. species as outgroups. Three new species of Conidiobolus are shown in bold. Maximum parsimony bootstrap values (≥ 70 %) / Maximum likelihood bootstrap values (≥ 70 %) / Bayesian posterior probabilities (≥ 0.95) of each clade are indicated along branches. Scale bar indicates substitutions per site.

Figure 2. Conidiobolus bifurcatus sp. nov. a Colony on PDA after 3 d at 21 ° C b mycelium c septate mycelium and distended segments d, e primary conidiophores bearing primary conidia f, g primary conidia h, i a single secondary conidium produced from primary conidia j two secondary conidia arising from a branched conidiophore k secondary conidia falling from primary conidia l the relic of secondary conidiophores on secondary conidia (arrows) m microconidia arising from a conidium n, o globose microconidia p, q ellipsoidal microconidia r zygospores formed between adjacent segments of the same hypha s zygospores. Scale bars: 10 mm (a); 100 μm (b); 20 μm (c-s).