Study On Isolation, Identification And Biological Characteristics Of A Pathogenic Strain Cercosporasp.FJ24 Against Water Hyacinth

Spread of Water Hyacinth (Eichhornia crassipes) caused serious environmental problems in lots of countries and regions. The importance of controlling it was recognized throughout the world. Currently, controlling Water Hyacinth with pathogens gained more and more attention. A strain FJ24, with high pathogenicity against Water Hyacinth was isolated from heavily diseased Water Hyacinth collected from Fujian province. On the basis of determining the pathogenicity of FJ24 against Water Hyacinth, biological characteristics of the strain were studied. Using morphological identification , the strain was preliminarily considered as Cercospora.The strain was further analysed at the molecular level. Four representative sequences of Cercospora sp.FJ24 including the ITS region,EF-1 region,β-Tub region and His-H3 region were sequenced and blasted with other signed Cercospora species on Genbank. Phylogenetic dendrogram were constructed to analyse the taxonomic position of Cercospora sp.FJ24.The results were as follows: The diseaed ratings of Cercospora sp.FJ24 reached 100% in 7 days; the diseased indexes were 23.33%,44.17%,78.33%,92.50% and 100% after 3 days ,7 days, 14 days, 21 days and 28 days respectively.Colony of Cercospora sp.FJ24 on PDA culture was hoar and its edge was light red, growing in cluster. Hypha almost invaded into the culture with clear edge. Conidiophores of Cercospora sp.FJ24 borne singly or in fascicles of 2 to 12, were light brown, septate, width regular, straight or lightly curved and no branched , measuring 63.4 to 247.6μm long and 2.5 to 5.5μm wide. Conidia developed singly , colourless or light brown with many transverse, measured 56.0 to 312.2μm long and 2.0 to 7.8μm wide. Preliminarily identify it as Cercospora.The colony of Cercospora sp.FJ24 grew best on PDA under the dark treatment of alternation illumination and darkness while the colony growed better on PDA under all darkness. The optimum temperature for colony longtime growth was found to be 30℃. The best colony growth was obtained at the condition of neutral pH or alkalescence. The fitting carbon and nitrogen source were amylum and ammonium acetate respectively. Cercospora sp.FJ24 presented varying morphological characteristics on different media tested, and the colonies grew best on MMA, PDAY and MSDA.Four phylogenetic trees were generated from the aligned ITS region,EF-1 region,β-Tub region and His-H3 region sequences. The treeing analyses showed that Cercospora sp.FJ24 presented highly homologous with many kinds of pathogenic strain in Cercospora piaropi. And the sequence similarities were above 99%.Biological characteristics of Cercospora sp.FJ24 and phylogenetic tree analyses indicated that Cercospora sp.FJ24 could be basically identified as Cercospora piaropi.The results listed above indicated that Cercospora sp.FJ24, isolated from this study, possessed the great potential to be developed into the fungal herbicide against Water Hyacinth. This research had positive significances for the biological control of exotic plants.