A histological study of the invasive and developmental processes of the aphid pathogenErynia neoaphidis(Zygomycotina: Entomophthorales) in the pea aphidAcyrthosiphon pisum

摘要

On landing on the surface of an aphid host, the primary conidium ofErynia neoaphidisproduced either a secondary conidium, a germ tube, or an appressorium. Appressoria were usually globose or clavate and each produced a single penetration peg. A circular bore hole marked the penetration site. Once the fungus had breached the cuticle, it formed protoplasts that failed to elicit an obvious immune response and multiplied rapidly in the haemocoel and in tissues. When the body of the host was occluded (about 3 days after penetration at 20 deg;C), the protoplasts regenerated a wall and differentiated into rhizoids, which were confined to the midventral region of the dead insect, pseudocystidia, and conidiophores. The rhizoids terminated in a digitate holdfast that adhered firmly to the plant cuticle but did not penetrate it. Conidiophores appeared to break out through the host cuticle using a combination of enzymatic and mechanical means.Key words:Erynia neoaphidis, Entomophthorales, infection, development, aphid.