Abstract: 【Aim】 One pathogenic fungus named TF-2 was isolated and purified from naturally entomopathogen-infected Acyrthosiphon pisum. This study aims to determine the classification status of the strain and to provide fungal resources for biological control of A. pisum. 【Methods】 The pathogenetic strain TF-2 was isolated and purified by back infestation test. Spore suspensions of TF-2 strain at different concentrations were prepared under microscope, and its virulence to adult pea aphid was measured by dipping method and in vitro leaf feeding method. The morphological characteristics of TF-2 strain were observed by optical microscope. The rDNA-ITS sequence of TF-2 strain was amplified by PCR and sequenced, and the phylogenetic tree was constructed for molecular identification of TF-2 strain. 【Results】 The results of virulence test showed that TF-2 strain showed strong pathogenicity to A. pisum adults, causing 100% corrected mortality at 6 d after treatment at a concentration of 1×10⁷ conidia/mL spore suspension. The colony of TF-2 is round on PDA medium, white or light yellow felt-like, and the bottom of the colony is creamy. The results of optical microscope observation showed that the spore phialides of the strain are bottle-shaped, and there are 2-3 spore phialides singly or laterally grown on the hypha, (19-42) μm×(1.1-2.5) μm in size. The base is relatively thick and gradually taper to the tip, and the conidia are oval, (4.2-11.8) μm×(1.6-2.6) μm in size. Mycelium produces crystals as octahedra. The rDNA-ITS sequence of the strain TF-2 has 99% nucleotide identity with that of Lecanicillium longisporum (GenBank accession no.: KX426564) and shares the same branch of phylogenetic tree. 【Conclusion】 The strain TF-2 is determined as the pathogenic fungus L. longisporum with potential application value in biological control of A. pisum.

Key words: Acyrthosiphon pisum, Lecanicillium longisporum, entomopathogenic fungi, ITS sequence, virulence