Abstract:

The effect of different treating time with the pulsed magnetic field (PMF) on the growth and infestation of Botryosphaeria dothidea was studied under a condition of fixed pulse rise time 10 ms. The results showed that short PMF treatment was able to effectively inhibit growth and infestation Botryosphaeria dothidea, and the longer time the treatment , the stronger the inhibition. With pulse treatment for 45 min, colony was inhibited by 54.11% in 48 h, and the browning index of poplar callus inoculation after 72 h was only 26.89%; With pulse treatment for 60 min, the inhibitory effect was best, and the colony all was dead. The observations with SEM revealed that the colony had the characteristics of uneven thickness, the mycelium stuck together, the surface wrinkled, branch and parts of hyphae even dried out. Based on TEM, after pulse magnetic field treatment, the cell wall became significantly thinner and the inner parts disordered and degraded, moreover the cell structure was destroyed seriously and intracellular vacuoles increased. In the meantime, the poplar callus cells structure was influenced to different degrees by B. dothidea, including deformation and disintegration of cell wall, decomposition of the layer, fracture of plasma membrane, plasmolysis; Cell organelles decomposed and deposited near cell walls, degradation of intracellular hyphae and cavum. The pulsed magnetic field had a strong inhibitory effect on the growth and infestation of B. dothidea and could change the mycelium ultrastructure.

Key words: pulsed magnetic field, Botryosphaeria dothidea, pathogenicity, mycelium, cell Structure