| The investigation for mangrove plant diseases of Leizhou Peninsula were conducted and the pathogens caused mangrove plant diseases newly discovered and happening widely were isolated and identified. Moreover, the biological characteristics of the pathogen which caused red spot disease of Aegiceras corniculatum which was prevalent and serious disease were studied in this paper.⑴ From 2013 to 2015, there were 20 varieties of mangrove plant diseases were found in Leizhou Peninsula, including Donghai, Techeng island, Gaoqiao and Xuwen. The red leaf spot of Aegiceras corniculatum, sooty mold of Aegiceras corniculatum, black stem of Avicennia marina, black spot disease of Avicennia marina, gray leaf spot of Avicennia marina, brown spot of Bruguiera gymnorrhiza and black spot disease of Acanthus ilicifolius were severely serious and frequently occurring diseases. Among all the mangrove plant diseases, the red spot leaf of Aegiceras corniculatum was the most common disease and it happened in all survey areas(including Dongzhai Harbour, Hainan and Futian District, Shenzhen). It was the most serious in Xuwen and Gaoqiao, ect. The incidence rate of the ill leaf generally was 30%~50%, and it reached more than 75% in some survey areas. There were 12~15 scabs in each ill leaf, and some were above 30.Furthermore, sooty mold of Aegiceras corniculatum occured commonly in Gaoqiao dstrict but the lighter at Dongzhai harbor. In 2013, the investigation found that black stem caused lots of Avicennia marina withered or died. The black spot disease of Acanthus ilicifolius occurred commonly in the Futian district, Shenzhen and the brown spot of Bruguiera gymnorrhiza was the most serious disease in Guanhai Changlang and Techeng Island. The red leaf spot(Aegiceras corniculatum) and the black spot(Avicennia marina, Acanthus ilicifolius) were first reported in china and abroad.⑵ By the method of pathogen-containing tissue isolation, six kinds of pathogens caused mangrove plant diseases included red leaf spot of Aegiceras corniculatum, black stem of Avicennia marina, black spot disease of Avicennia marina, gray leaf spot of Avicennia marina, black spot disease of Acanthus ilicifolius and brown spot of Bruguiera gymnorrhiza had been isolated and identified as Pestalotiopsis clavispora, Fusariumequiseti, Stemphylium lycopersici, Alternaria tenuissima, Fusarium solani and Alternaria alternate respectively on morphology and molecular biological characteristic.⑶ The results on the biological characteristics of strains THS3 isolated from the red leaf spot of Aegiceras corniculatum showed that the optimum grown was PDA. The strains THS3 could grow between 10℃ and 32℃ with optimum of 25℃ ~ 28℃. The strains couldn’t grow in below 5℃ or over 35℃. The temperature for sporulation was between10℃ and 32℃ with optimum of 30℃. The strains THS3 could grow and sporulate between pH 3.0~10.0, Partial acidic condition is good for mycelial growth but in neutral or mild alkali conditions benefited sporulation with optimum of pH7.5. The effects of light on strains mycelial growth and sporulation was different. Light could suppress mycelial growth but promote conidial formation and it was contrary in dark condition. The effects of Aegiceras corniculatum leaf extract on strains mycelial growth, sporulation and spore germination showed that low concentration leaf extract( < 1.67 %) could promote the strains mycelial growth, sporulation and spore germination. Besides that, the leaf extract of Avicennia marina and Sonneratia caseolaris also could promote the strains mycelial growth, sporulation and spore germination. And the leaf extract of Excoecaria agallocha and Kandelia candel could promote the strains mycelial growth and spore germination, but suppress sporulation. |
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