| Banana is one of the most important commercial crops in tropical and subtropical areas. The latest statistics from FAO showed that there were127banana planting countries around the world and total output was106.542million tons. The harvest area increased from4.246million hectares in2000to5.158million hectares in2011and the growth rate reached21.0%. As global banana planting area increased dramatically, banana fusarium wilt exploded which caused by Fusarium oxysporum invasion and threatened the banana industry development seriously. Dwarf banana is a hybrids cultivated variety of Musa which has many excellent characters in the fruit quality and plant adaptability to the environment. But its disease resistance against banana fusarium wilt is poor and the ideal method of prevention and cure has not been found.In order to seek effective methods to control dwarf banana fusarium wilt, provide the theory and lay the foundation for bio-control agentia for dwarf banana fusarium wilt, taking "Chinese Dwarf banana NO.1" seedlings as experimental material and dwarf banana wilt disease biological control as the goal, study the pathogenic characteristics of pathogenic bacteria to dwarf banana seedling by experiment of using F. oxysporum Race1to invade potted seeds in vitro. At the same time, taking F. oxysporum Race1as indicator bacteria, high efficient antagonistic bacteria to banana wilt disease which isolated from cake fertilizer and then fermented secondarily with rape seed cake was used to study the prevention and control effect to dwarf banana fusarium wilt. The results following:1. The ability of dwarf banana seedlings against banana fusarium wilt was poor. It was infected rapidly when invaded banana fusarium wilt.102cfu·g-1(soil) Pathogen concentration was the "threshold" that dwarf banana seedling got disease. When the concentration of pathogenic bacteria in the soil was below this threshold, dwarf banana seedlings would not be infected. When the external environment was consistent, it was more serious with the concentration of pathogenic bacteria increasing in the soil. When the concentration of pathogenic bacteria was104 il), dwarf banana seedlings got disease on the11th day and the disease index reached100%after45days. When the concentration of pathogenic bacteria was105cfu·g-1(soil), there was no significant difference with above treatments.2.238strains were isolated from cake fertilizer fermented liquid which containing rich organic matter and crude protein.29strains were screened eventually which had good inhibitory effect to banana fusarium wilt and their inhibitory rate reached42.0%-87.2%. Clustering analysis showed that27of them belonged to Bacillus, one belonged to Lactobacillus strains Lactobacillus and the others belonged to Serratia.3. Strain2-L-24and1-G2-03were identified and their antibacterial activity was studied further. The inhibition rate of these two strains to the growth of mycelial of banana F. oxysporum Race1reached87.2%and81.6%respectively. Both of them had inhibition effect on a variety of plant pathogenic fungi with wide antimicrobial properties. Strain2-L-24was finally identified to be methyl nutritional bacillus and strain LP-03was plant lactobacillus. The optimal growth temperature of the strain2-L-24was30℃, the best pH was7.0. And the optimal growth temperature of the strain LP-03was37℃, the best pH was7.0.4. Strain BM-24induced by Rifampicin and got mutant strain BM-24Rif with400μg·mL-1rifampicin concentration can be effectively tracked and recovered.5. Fermentation liquid of strain BM-24Rif fermented secondarily with rape seed cake, rape seed cake fermentation liquid and the BM-24Rif LB fermentation liquid all had prevention and control effect against banana fusarium wilt pathogen, among of which the former has most significant effect. At the end of the experiment, disease index of three treatments declined to82、64and49respectively compared with CK. The fresh weight of airpart was increased81.19g,60.60g,59.3g respectively. The activity of SOD、POD、CAT and the Chlorophyll content were significantly improved. The root RC was lower than CK2.6. Concentration of pathogen bacteria in the banana rhizosphere soil and non-rhizosphere soil declined significantly after different fermentation liquid treated when the experiments finished on51th d, the amount of pathogen bacteria in the rhizosphere soil of CK2was in the order of magnitudes of105cfu·-1(soil). Compare with this data, it declined to the order of magnitudes of103cfu·g-1(soil) after using fermentation liquid of strain BM-24Rif fermented secondarily with rape seed cake and rapeseed cake fermentation liquid. The antagonistic bacteria fermentation liquid treatment reduced to104cfu·g-1(soil) order of magnitudes.7. BM-24Rif can effectively colonize in rhizosphere soil of dwarf banana. Concentration of strain BM-24Rif reached maximum value after fermentation liquid of strain BM-24Rif fermented secondarily with rape seed cake and and the strain BM-24Rif LB fermentation liquid treatment on15th～20th d. and then began to decline on35th and25th respectively. Rape seed cake fermentation liquid can significantly improved the effect of the colonization of strain BM-24Rif. |
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