Abstract:

Histopathological changes of Cotinus coggygria inoculated with Verticillium dahliae were observed by using paraffin sections and optical microscope photography. The results showed that the different parts of C.coggygria had different infection levels, with leaves the highest (18.83%), and branches the lowest (6.72%). After inoculation, the hyphae initially invaded the elongation zone and mature zone of roots, and then appeared in the intercelluar space cortex parenchyma cells within 1-3 cm of the root tip, and further went into vessels of the roots, then reached leaves through the vessels of stems and branches finally. V. dahliae mainly occurred in vessels of xylem in the form of hyphae, however it did not appear continuously. In order to prevent expansion of the pathogen after infected, wall of the vessel was thickened, inner diameter of the vessel was decreased by accumulating jelly and tylosis generated in the xylem, or even the vessel was totally blocked. When the C. coggygria was infected, the vessel walls, parenchyma cells and cortical cells were thickened, the inclusions of pith, resin canals and secretory cells nearby increased, the jelly appeared in the parenchyma cells and wood rays. Although parts of vessels were blocked with hyphae, jelly and tylosis to different extent, most of the vessels were healthy and were able to function water transport normally. The partial block of vessels sometime caused plants wilt, but the plant managed to maintain almost normal activities.

Key words: Cotinus coggygria, Verticillium dahliae, Verticillim wilt, histopathology