Identification Of Antagonistic Bacteria Against Alternaria Spp., The Causal Agent Of Jujube Shrinking Fruit Disease, And The Study Of Effect On Disease Resistance

Jujube fruit disease is one of the most serious diseases of different places in China, in which it restricts the health growth and economic development of jujube. Based on the advance of quickly controlling disease, chemical control method is as the main measures; but its side effects are significant:poor taste, pesticide residues and serious environmental pollution. This paper employed Alternaria tenuissima MY5 as pathogens to examine the two strains of antagonism bacteria STO-12 and STO-45. Additonnaly, using STO-12 and STO-45 to control commen plant desease was done. To fully understand the biological characteristics of antagonistic microorganisms and clarify its antibacterial material is the key to develop biological pesticide. The bacteria were identified based on morphological, physiological and biochemical features, and a phylogenetic analysis was conducted on an alignment of 16S rRNA sequences. Examining the fermentation filtrate, the inhibitory action of antibacterial activity and antibacterial efficiency were done. Further study on of inhibitive substance of the fermentation filtrate and analyzes the structure of lipopeptide was examed.1. Two strains of bacteria, STO-12 and STO-45, that were isolated and screened from the soil exhibited excellent inhibition against the fungal pathogen. In addition, they also showed observably inhibition against other phytopathogen, such as A. alternata, Botryosphaeria dothidea, Phoma glomerata, Colletotrichum gloeosporioides, Cytospora sacculus, Cytospora leucostoma, Cytospora mali, Fusarium oxysporum and Fusarium solani.2. Based on molecular, morphological, physiological and biochemical features, the two strains were identified as Bacillus subtilis. However, the two strains differed in the production of a pigment that was shorter in length in STO-12 than in STO-45.3. The fermentation filtrate, the supernatant and the cell-free filtrate of both strains exhibited excellent inhibition against the strain MY5 with a dual culture assay. The strain of STO-45 was easy to spread and rich in cellulose enzyme activity and surface activity. Further effects of the cell-free filtrate of STO-45 on the pathogen included inhibition of germ tube and hyphal growth, and abnormally swollen or degraded hyphae and germ tubes.4. The protein compounds in liquid of strain STO-45 have significant inhibiting effect to W and MY5. The crude proteins have the average bacteriostatic rate at 82.2% and 89.95% after managing for senven day and there was also high inhibiting effect after 30 day.5. The lipopenic of strain STO-45 has also significant inhibiting effect to W and MY5. After 7 day, the average bacteriostatic rate was at 99% and 90.05%. It was also keeping perfect inhibiting effect to W and MY5 after 30 day.We proposed that the lipopeptide’surfactin C17:0’ of the strain STO-45 was suspected as new carbon chain isomer lipopeptide.