Biological Characteristics Of The Pathogen Of Trifolium Repens Powdery Mildew And Histological Analyses On Infected Leaves

Trifolium repens L.is a kind of important leguminous forage and turfgrass.With more and more clover used in greening,the planting area is also gradually expanded,and diseases and insect pests are also gradually aggravated,among which the most important disease is Erysiphe pisi DC.In this study,the biological characteristics of the pathogen of T.repens powdery mildew,the histological changes of the leaf of clover,and the selection of fungicides were studied after being invaded by powdery mildew in the leaves of T.repens.The research results are follows:(1)The results of spore morphological observation and molecular identification of powdery mildew pathogen showed that the main pathogen of T.repens powdery mildew is Erysiphe pisi DC.,which belongs to ascomycotina.(2)The results of biological characteristics test of pathogen of T.repens powdery mildew indicated that the optimal temperature is 25?.Light had no significant effect on the spore germination and germ tube growth.It could germination under full light,total darkness and 1/2 light,but ultraviolet light could promote the spore germination and significantly affected the germ tube growth.The optimum pH is 7 for spore germination.(3)The results of the determination of the conidia activity of the powdery mildew of T.repens showed that the conidia determined by I2-KI staining method had the highest viability,which was 54.75%,but the staining results were vague,followed by methylene blue staining and solid green staining,which were 52.69%and 46.60%,respectively.The TTC staining method has no effect on the conidia staining of powdery mildew,and the spores are not colored.(4)The histopathological study of the interaction between the spores of powdery mildew fungus and T.repens showed that the spores of powdery mildew fungus were inoculated in the leaves for 4 hours,and germinated at one end of the conidia to form the primary germ tube,which formed appressoria and began to invade the leaf epidermis after 10 hours.After 12 hours,the nascent mycelium was formed on the other side of the spore.After 24 hours,the primary hypha grew,and a sputum was formed at the tip of the appressoria to start acquiring nutrient in the host.After 48 hours the primary hypha produced on the host surface further branched to form a large number of secondary hyphae.After 4 days,a large number of hyphae were formed on the surface of the leaves,and conidiophore was formed and the whole infection cycle is completed.The primary conidia fall again on the leaf surface,ready to germinate,and begin the next infection cycle.At this time,powdery mildew fungus appeared initially in the leaves,and white hyphae could be observed on the leaf surface with eyes.After 7 days,a large number of hyphae formed,and powdery layers appeared in the leaves obviously.(5)The drug screening test showed that the 800 fold solution of diatomite powder had a significant inhibitory effect on the germination of powdery mildew spores,and the 500 fold solution of wood vinegar enzyme solution had a certain inhibitory effect on the growth of powdery spores.The research results showed that after different treatments,powdery mildew disease leaf number is reduced,the incidence and disease index decreased,after 600 fold wood vinegar enzyme solution processing control effects is more than 80%,diatomite powder 800 fold solution control effect is more than 90% after processing.