Metarhizium multisynnematum Y. Yang, K.D. Hyde & Y.P. Xiao, 2025

Yang, Yu, Xiao, Yuan-Pin, Hyde, Kevin D., Jayawardena, Ruvishika S., Lu, Yong-Zhong, Mapook, Ausana, Nilthong, Somrudee, Al-Otibi, Fatimah, Xie, Shu-Qiong & Li, Xiang-Dong, 2025, Discovery of a new species and a new geographical record of Metarhizium (Clavicipitaceae, Hypocreales) from China, Phytotaxa 683 (2), pp. 91-105 : 98-99

Metarhizium multisynnematum Y. Yang, K.D. Hyde & Y.P. Xiao sp. nov.

Index Fungorum number: IF902882, Facesoffungi number: FoF 16769

Etymology: The new species is named after its multiply branched synnemata.

Asexual morph : Metarhizium -like. Primary s ynnemata 1.6–2 cm long, 0.2–0.4 mm wide, arising from the insect head, solitary, or several, stipitate, multiply branched, reddish to light grey, not smooth, secondary synnemata observed, without an enlarged globose fertile head on the tip. Secondary synnemata 2–7 mm long, 0.1–0.2 mm wide, laterally scattered along the primary synnemata, unbranched, light grey, cylindrical. Phialide 7–12 × 1.5–3.2 µm (= 9.5 × 4.3 µm, n = 30), solitary, smooth-walled, cylindrical to clavate, with a distinct neck. Conidia 2.5–3.8 × 1.3–2.2 µm (= 3.2 × 1.7 µm, n = 50; L/W ratio is 1.14–2.92), ellipsoidal, 1-celled, hyaline. Sexual morph : Not observed.

Cultural characteristics: Colonies on PDA grow slowly, reaching 2 cm in diameter after 20 days at 25 ℃, brown, covered with irregular, dense bulges with white margins. Synnemata are produced after 35 days, with the reverse side showing a sulphur-like yellow. Conidiophores arising from synnemata, smooth-walled. Phialides 9.2–12.5 × 1.6–3.4 μm (= 10.8 × 2.5 µm, n = 30), smooth-walled, cylindrical, with a distinct neck. Conidia 2.5–3.8 × 1.2–2.8 μm (= 3.2 × 2 µm, n = 50; L/W ratio is 0.89–3.17), ellipsoidal, hyaline, smooth-walled.

Material examined: CHINA, Guizhou Province, Qiannan City , alt. 1051 m, 107.607 E, 26.965 N, 24 June 2023, collected by Yu Yang, ZJS2361 (HKAS 132148, holotype), ZJS2361J (GZCC 24-0206, ex-type living culture) ; CHINA, Guizhou Province, Guiyang City , alt. 1264 m, 106.773 E, 26.903 N, 31 May 2023, collected by Yu Yang, XW 2348 (HKAS 132273, paratype), XW2348J (GZCC 24-0196, ex-paratype living culture) .

Known distribution:— Guizhou, China

Known hosts:—Cocoons of Lepidoptera buried in the soil.

Notes: Phylogenetic analysis based on the combined dataset of SSU, LSU, ITS, tef-1α, rpb1, and rpb2 genes revealed that our collection (HKAS 132148) form a distinct branch and is sister to the clade containing Metarhizium phuwiangense and M. reniome ( FIGURE 1 ). Morphologically, Metarhizium multisynnematum differs from M. phuwiangense and M. reniome by parasitizing lepidopteran larvae within cocoons, having reddish stipes, and producing multi-branched synnemata, features also observed in culture. While both M. minus and M. dendrolimatilis produce synnemata in culture, M. multisynnematum is distinguishable by its cylindrical to clavate phialides and its distinct host ( Rombach et al. 1986; Chen et al. 2017). Based on phylogenetic and morphological evidence, M. multisynnematum was introduced as a novel species.

Metarhizium phasmatodeae Thanakitpipattana, Tasanathai, Mongkolsamrit, Khonsanit, Lamlertthon & Luangsa-ard, Persoonia 44: 151 (2020)

Index Fungorum number: IF 830170

Host: Found on stick insects (Phasmatodea) in the leaf litter on the forest floor, the host's body is covered with green colonies.

Asexual morph : Metarhizium -like. White mycelia and green powdery conidia were observed on the host. Phialides 7.5–13 × 2.5–4.5 μm (= 10.3 × 3.5 µm, n = 30), smooth-walled, cylindrical. Conidia 5.5–8 × 2.1–3.1 μm (= 6.7 × 2.6 µm, n = 50; L/W ratio is 1.77–3.81), hyaline, smooth-walled, cylindrical to oblong-elliptical. Sexual morph : Not observed.

Cultural characteristics: Colonies on PDA grow rapidly, reaching 2.5 cm in diameter after 7 days at 25 ℃, flat and closely appressed to the agar surface, initially white and turning yellowish to olive green, with white margins. The colonies become powdery during sporulation, which begins 5 days after inoculation, with the reverse side showing a sulphur yellow color. Conidiophores arise from aerial mycelia and are erect and smooth-walled. Phialides 8.5–12.5 × 2.8–4.4 μm (= 10.5 × 3.6 µm, n = 30), smooth-walled, cylindrical. Conidia 5.8–8.2 × 2.2–3.6 μm (= 7 × 2.9 µm, n = 50; L/W ratio is 1.61–3.73), smooth-walled, hyaline, cylindrical with rounded or semi-papillate apices.

Material examined:— CHINA, Anhui Province, Huangshan City, alt. 164 m, 118.608 E, 29.879 N, 6 July 2023, collected by Yu Yang, SX23161 (HKAS 132219), SX23161J (GZCC 24-0177, living culture).

Known distribution:— China, Thailand

Known hosts:—Stick insects (Phasmatodea)

Notes: Morphologically, our new collection (HKAS 132219) is almost identical to M. phasmatodeae , with the primary difference being the size of the conidia. The collection exhibits smaller conidia compared to the holotype of M. phasmatodeae , originally reported from Thailand (5.5–8 × 2.1–3.1 μm vs. (6–)7–8.5(–10) × 2–3 µm; L/W ratio is 1.77–3.81 vs. 2.00–5.00) ( Thanakitpipattana et al. 2020). In our phylogenetic analysis, the new collection is clustered within the M. anisopliae species complex, forming a sister group to M. phasmatodeae (BBH 32532) ( FIGURE 1 ). The sequence data comparison of SSU, LSU, ITS, tef-1α, rpb1, and rpb2 between the new collection (HKAS 132219) and M. phasmatodeae (BBH 32532) showed no significant genetic differences ( Thanakitpipattana et al. 2020). Thus, the new collections were identified as M. phasmatodeae , making the first report of this species from China.

Figures

FIGURE 1. Phylogenetic tree from RAxML analysis based on combined SSU, LSU, ITS, tef-1α, rpb1, and rpb2 sequence data. The values at the nodes represent ML bootstrap proportions (ML-BP ≥ 75%) before the backslash and BI posterior probabilities (BI-PP ≥ 0.90) after the backslash. Type strains are marked with a ‘T’. The newly generated sequences are in red bold.