Figure 3
Transmission electron micrographs of P. betae sporosorus, resting spores, zoosporangia, and zoospores. (A) Micrograph shows sporosorus contains a cluster of 14 resting spores. (B, C) Micrographs show resting spores with different staining intensities. Arrows in b point to gold particles detecting viral replicase. Pb1, Pb2, Pb3, Pb4, Pb5 indicate the layers of the cell wall. The nucleus (n), storage bodies (sb), and matrix (m) are indicated. c, sample treated with buffer shows no gold particles. (D, E, F) Zoosporangium and zoospores (z) from virus infected plants. (D, E) Arrows point to gaps in the zoosporangial wall (zw). Individual zoospores (z) are identified. (F) Micrograph of zoospores show the nucleus (n), storage bodies (sb), vacuoles/vesicles (v), flagella (fl). Arrows point to various irregularly shaped vesicles. Some seem to extrude into the exterior of the zoospore. (G, H, I) Zoospornagium and zoospores in virus-free plants. In comparing (F) and (H), the healthy zoospores are highly vacuolated. Bars in A, B, C, F, H, I, represent 1 μm. Bars in D, E, G, represent 10 μm.