Metarhizium synnematis Z.Q. Liang, H.L. Chu, & T.C. Wen, 2016

Chu, Hua-Li, Chen, Wan-Hao, Wen, Ting-Chi, Liang, Zong-Qi, Zheng, Fu-Chong, Liang, Jian-Dong & Han, Yan-Feng, 2016, Delimitation of a novel member of genus Metarhizium (Clavicipitaceae) by phylogenetic and network analysis, Phytotaxa 288 (1), pp. 51-60 : 55

Metarhizium synnematis Z.Q. Liang, H.L. Chu, & T.C. Wen , sp. nov. ( Fig. 3 )

MycoBank: MB808755, Facesoffungi number: FoF 02252.

Type: — CHINA. Guizhou Province: Guiyang City, Xiaochehe Forest Wetland Park, on a cocoon of an unidentified species of Lepidoptera, 12 July 2013, Zong-Qi Laing XCH.L12 (GZUHXCHL 12 Holotype!).

Host a 30 × 20 mm Lepidopteran cocoon. Asexual morph: Synnemata slender, cylindrical, light brown, upper part pale green, 5–10 mm long and 0.05–0.1 mm wide. Phialides cylindrical to sub-clavate, 5.4–8.6 μm long and 1.1 μm wide with a short neck, most phialides produced either as lateral cells or as terminal cells of short, lateral branches of outer hyphae along the upper part of the synnemata, eventually covering the surface of the synnemata in a hymenium-like manner. Conidia ellipsoidal to cylindrical or sub-clavate, slightly acute at each end, 2.2–4.3 × 1.1 μm, coated with a thin sticky substance, and aggregating into sticky masses. Sexual morph: Undetermined.

Etymology: —Refers to the Akanthomyces -like synnemata.

Distribution: —Known only from China.

Host: —On a Lepidopteran cocoon.

Notes: Metarhizium synnematis is morphologically similar to M.flavoviride in both phialides and conidia.However, M. flavoviride does not produce synnemata, and forms larger phialides (7.2–9.6 × 2.5–3.1 μm), as well as larger conidia (4.5–7 × 2–3 μm), as compared both phialides (5.4–8.6 × 1.1 μm) and conidia (2.2–4.3 × 1.1 μm) of M. synnematis ( Table 1). It differs from related Metarhizium species mainly by its small, ellipsoidal to cylindrical or sub-clavate conidia, which are coated with a thin sticky substance and are aggregate into sticky masses. The phylogenetic tree and network based on the maximum likelihood, mini-spanning and neighbor net method also revealed M. synnematis to be a new taxon of the genus Metarhizium ( Fig. 3 ).

Metarhizium synnematis can form determinate Akanthomyces -like synnemata ( Seifert 1985). This characteristic is indicative of an Akanthomyces sp. ( Mains 1950, Samson & Evans 1974). However, the phialides of GZUHXCH12 were clearly cylindrical to subclavate with a short neck ( Fig. 1 , 4 –6), and conidia were coated with mucus and aggregated into sticky masses. These characteristics clearly showed that the specimen belongs to the genus Metarhizium ( Tulloch 1976) . It could be distinguished from other species of Metarhizium by its slender synnemata (length: width = 50– 100:1) and smaller conidia (2.2–4.3 × 1.1 μm; Table 1). Based on the morphological criterion, the specimen could be regarded as an intermediate between Metarhizium and Akanthomyces .

Figures

FIGURE 1. Phylogenetic relationship between Metarhizium synnematis GZUHXCHL12 and its allies based on ITS-5.8S rDNA sequence data. Bootstrap values (1,000 replicates) are indicated above the nodes.

FIGURE 3. Metarhizium synnematis (holotype) A. Synnema on a lepidopteran cocoon. B. Upper part of a synnema. C. Phialides covering the surface of the synnema in a hymenium with conidia aggregating in sticky masses. D. Phialides. E. Conidia. Scale bars: A = 10 mm, B = 100 μm, C–E = 10 μm.

FIGURE 4. Reconstruction of Neighbor-Net network of Metarhizium synnematis and Metarhizium sp.