Identification And Biological Characteristics Of A Pathogene Causing A Leaf Spot On Osmanthus Fragrans

Through the study on Osmanthus fragrans leaf spot, nurseries to ascertain thetaxonomic status and biological characteristics of the pathogenic, inorder o lay thefoundation for the prevention of osmanthus leaf spot. The results of the studies are asfollows:Three predominant strains obtained by separating and purifying the pathogen, thatis strain I, strain II and strain III. According to the Koch’s Rule, strain III is presumedpathogenic strains. Based on its symptoms, morphology and ITS sequence analysis todetermine that strains III is Botryospaeria dothidea, and it’s anamorph is Fusicoccumaeculi Corda.The biological characteristics results of B. dothidea show that, The optimumCarbon source is maltose, followed by lactose. The optimum Nitrogen source is(NH4)2SO4, followed by C5H9NO4. The pathogen fungus can grow at15℃~35℃, andthe optimum temperature is25℃. The optimum illumination for fungus is16h lightand8h dark. The optimum growth pH is4, and the range of pH is4~10, the weaklyacidic conditions are beneficial for the growth of pathogenic fungi.Indoor antifungal test shows that,10%difenoconazole WG has strong inhibitioneffect on the fungus growth, EC50is0.6839μg/mL, followed by the400g/L flusilazoleEC and250g/L tebuconazole EW, Relatively speaking,75%chlorothalonil WP has theworst inhibition effect, EC50was57.0078μg/mL.This study is based on morphology, by ITS sequence analysis to determine thatOsmanthus fragrans leaf spot pathogenic is B. dothidea. Through the biologicalcharacteristics research, defined the optimum growth conditions for the pathogenic andeffective antiseptic for prevention,To lay the foundation for ascertain the occurrenceand development of the osmanthus leaf spot and its disease prevention. This has animportant meaning to improve the osmanthus industry’s ornamental value and diseasecontrol, will also play a positive guiding role in the production practice.