Identification Of The Pathogens Of Banana Sheath Rot Disease And Screening Of Antagonistic Bacteria

The identification of the pathogen of banana sheath rot disease, the endophytic bacteria in mangrovs( Acrostichum aureurm,Aegiceras corniculatum,Acanthus ilicifolius and Kandelia candel ) and the screening of antagonistic bacteria against the pathogen were studied in this paper.It was proved that the pathogen of the banana sheath rot disease in Xuwen and Suixi of Guangdong province was a bacterium by tested of Koch's postulates. Based on the morphological and biochemical characteristics and 16SrDNA analysis, the pathogen isolated from the banana sheath rot was identified as Pantoea agglomerans. It is the first report that Pantoea agglomerans could cause the disease of banana sheath rot.The numbers of the cultivable and non-culturable endophytic bacteria of Acrostichum aureurm,Aegiceras corniculatum,Acanthus ilicifolius and Kandelia candel were tested by fluorescence microscopy with acridine orange dye and spread plate method. The results showed that the amount of the endophytic bacteria were differences both in mangroves and the parts of the same mangrove species. From the different parts of the same mangrove species, the amount of nonculturable endophytic bacteria in Acrostichum aureurm was [AVG 8.97×107cfu/g(FW), most in leves], and the amount of cultivable was[AVG 1.88×103cfu/g(FW), most in roots]; the amount of nonculturable in Aegiceras corniculatum was[AVG 5.37×107 cfu/g(FW), most in stems], and the amount of cultivable was[AVG 2.92×103 cfu/g(FW), most in leaves]; the amount of nonculturable in Acanthus ilicifolius was[AVG 8.52×107cfu/g(FW), most in roots], and the amount of cultivable was[AVG 3.29×107cfu/g(FW), most in roots]; the amount of nonculturable in Kandelia candel was[AVG 11.17×103cfu/g(FW), most in leaves], and the amount of cultivable was [AVG 3.94×103cfu/g(FW), most in roots]. From the same parts of the different mangrove species, the amount of noncul -turable endophytic bacteria in roots was[AVG 8.85×107cfu/g(FW), most in Acrostichum aureurm], and the amount of cultivable was[AVG 3.7×103cfu/g(FW), most in Kandelia candel];the amount of nonculturable endophytic bacteria in leaves was [AVG 7.25×107cfu/g(FW), most in Kandelia candel], and the amount of cultivable was [AVG 2.58×103cfu/g(FW), most in Acrostichum aureurm] ; the amount of nonculturable endophytic bacteria in stems was [AVG 9.31×107cfu/g(FW), most in Kandelia candel], and the amount of cultivable was[AVG 2.75×103cfu/g(FW), most in Acrostichum aureurm].And it was found that the time-varying volatility of cultivable and nonculturable endophytic bacteria in different parts of the same mangrove trees was different from that in the same part of different mangrove trees.The proportion of cultivable endophytic bacteria in the endophytic bacteria was different in the same part of each mangrove species: Acrostichum aureurm [root 0.039‰, stem 0.031‰, leaf 0.012‰], Aegiceras corniculatum [root 0.073‰, stem 0.174‰, leaf 0.133‰], Acanthus ilicifolius [root 0.320‰, stem 0.087‰, leaf 0.115‰], Kande -lia candel [root 0.235‰, stem 0.104‰, leaf 0.039‰]. That meant only a little part of endophytic bacteria could be cultured and most of them could not yet be cultured.Among all of 24 endophytic bacteria isolated from mangroves, 12 strains were found to have the antibacterial activities against Pantoea agglomerans by the tests of confront culture, and the strain Aec23 from Kandelia candel was the best antibacterial activity. According to the traditional morphological, physiological and biochemical characteristics, and 16Sr DNA analysis, strain Aec23 was identified as Bacillus amyloliquefaciens. The antibacterial substances of the strain Aec23 was preliminary studied in this paper.