The surface and internal structure difference of yellow and black dormant chlamydospores of Ustilaginoidea virens on mid-and late-season rice were examined by scanning electron microscopy(SEM) and transmission electron microscopy(TEM).SEM revealed that the spherical yellow and black chlamydospores had prominent spines,with the diameters from 3 to 6 μm and 4 to 6 μm,respectively.The spines were 200-700 nm and 400-1 100 nm long in yellow and black chlamydospores,respectively.Variance analysis showed that there was no difference in diameter of the yellow chlamydospores but significant difference among the black ones collected from both rice cropping types.Similarly,there was no difference in length of the spines on the same color chlamydospores but extremely different between the yellow and black chlamydospores collected from the two cropping types.TEM revealed that the cell wall of both color chlamydospores were composed of two layers,the thick endosporium and thin exosporium,and the thickness of the former layer of the black chlamydospores was nearly two times as that of the yellow ones.The organelles in yellow chlamydospores such as the nucleus were obviously visible,but invisible in black ones.The cytoplasm of black chlamydospores was occupied by a big lipid globule.This study suggests that the formation of dormant chlamydospores of U.virens is related with the structural changes in the cell.
