Figure 2. Pathogenic infection in soybean stems infected with Phialophora gregata.

Pathogenic infection by wild-type isolates of types A and B of Phialophora gregata as observed 8 weeks post inoculation in cross sections of stems from a susceptible soybean cultivar (Corsoy 79). (A) No infection was observed in the non-inoculated control. (B) Inoculated with Type B. (C), A necrotic vessel with no fungal structures seen inside. (D), A vessel heavily colonized by P. gregata. (E)A vessel with evidence of sporulation (arrow). (F), Hyphae of P. gregata growing between vessels, possibly via pit pairs. (G), A longitudinal section of the xylem infected by P. gregata. (H and I), P. gregata beginning to colonize the parenchyma cells that compose the pith of the stem. Images A–G and I are 200x magnification, H 400x magnification.