Biological Characteristics Of Cercospora Piaropi WH9BR And BA-57 For Control Of Water Hyacinth

Water hyacinth is a common and serious environmental problem throughout the world. Currently, the use of pathogens to control Water Hyacinth gains much attention. The fungus Cercospora piaropi is a world-acknowledged potential mycoherbicide agent for controlling water hyacinth with its high security and efficiency. Two isolates, WH9BR and BA-57, were cultivated under different conditions to determine the optimum light, temperature, pH, carbon and nitrogen sources, culture media, moisture and nutrient media for their mycelial growth, sporulation and spore germination so as to optimize the cultivation methods.The results obtained are listed as follows. The spore germination rates of WH9BR and BA-57 were 37% and 36.67% after 24 hours respectively. The thermal death points of the spores of WH9BR and BA-57 were 57℃for 10 minutes and 55℃for 10 minutes respectively. The best cultural condition for mycelial growth and sporulation of WH9BR was 24h darkness while the optimum treatment of light for its spore germination was 24h illumination. The treatment of illumination had no significant effect on mycelial growth and sporulation of BA-57 while the best cultural condition for its spore germination was 24h darkness. The optimum temperatures for mycelial growth, sporulation and spore germination of WH9BR were 25℃, 25℃～30℃and 30℃respectively while the optimum temperature for mycelial growth, sporulation and spore germination of BA-57 was 30℃. At pH8.6 and 7.0, the best mycelial growth and spore germination of WH9BR were obtained respectively while the largest number of its spores was obtained at pH8.0～9.0. The optimum pH for mycelial growth, sporulation and spore germination of BA-57 were 7.6,10.0 and 9.0 respectively. The optimum culture media for mycelial growth of WH9BR were MMA and MSDA while the best culture medium for its sporulation was CDA. The optimum culture media for mycelial growth of BA-57 were PDAY, MMA and TWA while the best culture medium for its sporulation was PDAY. The optimum carbon source was mannitol for mycelial growth of WH9BR and BA-57 while glucose and sucrose were the best carbon sources for their sporulation. The optimum nitrogen source was urea for mycelial growth of WH9BR while NaNO3 was the optimum nitrogen source for its sporulation. As to BA-57, NaNO3 was optimum for both mycelial growth and sporulation. The highest spore germination rates of WH9BR and BA-57 were obtained when their spores were in drips. Cornmeal, peptone, glucose and sucrose could promote the spore germination of WH9BR while only peptone and cornmeal could promote the spore germination of BA-57.The results listed above can provide necessary references for the study of these two isolates'industrial production and the formulations concerned. Besides, the results also provide the basis for the further theoretical study and application of these two isolates.