Host Range And Pathological Characteristics Of Cercospora Piaropi For Water Hycinth Biocontrol

Water hyacinth, originated from South America, was introduced in China as livestock feeds in 1960th. It is listed as one of the world's most malignant weeds because of its fast growth, excess reproduction and severe ecology destroy and economic loss. In the integrated management system of water hyacinth, pathogens are put more and more importance on by scientists. We successfully introduced Cercospora piaropi, a pathogenetic fungal strain from University of Florida. In this thesis we mainly do research on its host range and pathological characteristics.We determined the pathogenic effect of temperature, inoculation concentration and moisture time to the water hyacinth; determined the pathogenic effect of the fungus to the water hyacinth under the optimized condition; made preliminary evaluation about its fungicidal toxin's pathogenic effect and applied it to 20 crops and 46 field weeds normal in Shanghai to determine its pathogenic effect. Moreover, we screened and separated out Alternaria WH56 and Cercosporella TF10 from water hyacinth of Zhejiang province. We preliminary determined the biological characteristics of TF10 and then made researches about the integrated pathogenic effect about fungal strains BA57, WH56 and TF10.The results obtained are listed as follows. It will take 6 weeks for original leave of water hyacinth from infected to dead by C. piaropi. The optimized inoculation concentration of C. piaropi to water hyacinth is 105cfu/ml, the best moisture time is 24h. 30℃is the best temperature for pathogenic effect of C. piaropi to original leave of water hyacinth from 20℃, 25℃and 30℃. We only found pathogenic effect of C. piaropi to water hyacinth and Sheathed Monochoria among all the crops and weeds we tested. The original, 10-1 and 10-2 time concentration of C. piaropi toxin have distinct pathogenic effect to leave after inoculating for 3 days. BA57 has the best pathogenic effect among all the three pathogenic fungi BA57, TF10 and WH56, and the combination of WH56 + TF10 + BA57 has better pathogenic effect than all the other possible combinations. TF10 gets the best mycelium growth under all-day illumination and the optimum temperature is 25℃, the optimum growth pH is 6.0 and culture media MSDA, MDYEA, PDAY and PDA are all optimum for mycelium growth of TF10.All the results above provided essential evidence for the exploitation of C. piaropi as feasible fungus mycoherbicide and for the security of its using in Shanghai area.