EFFECTS OF SYSTEMIC FUNGICIDE METALAXYL ON THE DEVELOPMENT OF DOWNY MILDEW IN SUNFLOWER
内吸杀菌剂甲霜灵对向日葵霜霉菌发育的影响

Effects of systemic fungicide metalaxyl on the development of downy mildew in infected sunflower leaves were examined with electron microscopy. The obsetvation showed that the fungicide caused a series of changes in the pathogen. The vacuoles and electon - dense bodies increased in hyphae, and some of mitochondria in hyphae swelled and became malformed. The cell walls of some hyphae were markedly thichened, and extremely thickened wall constituted false septa. Some irregular protrusions were observed on the hyphae. The exhaustorial matrixes were found to be enlarged and contain numerous electrondense material. Some of haustoria did not normally expand and became malformed. It was evident that the cytological changes described above led to the necrosis of hyphal cells and haustoria, which inhibited the further development of the pathogen.