| The hybrid Cymbidium with both bright colours of Cymbidium hybridum and elegant leaf and pleasant fragrance of Chinese Cymbidiums has high ornamental value and economic value. But in their process of commercialization, stem rot disease is increasing year by year, seriously restricting the development of hybrid Cymbidium industry. In order to control stem rot disease, in this research, Cymbidium 'Yunv' was employed to investigate the effects of silicon nutrition, biocontrol bacteria and pesticides on prevention and cure of stem rot disease. The main results were as follows.(1) Application of 1-2 mmol/L silicon fertilizer delayedtheoccurrence timeofstem rotdisease in ‘Yunv' for about two weeks, and effectively reduced the disease index. After infected by Fusarium oxysporum, silicon treatment obviously increased the SOD activity, POD activity, MDA and silicon contentin‘Yunv' pseudobulb.(2) The biocontrol bacteria G01 had an antagonistic effect on Fusarium oxysporum. Indoor and field pot experiment showed that the control effect of sterile extract was better than that of fermentation broth. The result identified by microstructure and culture characters, combinedwith molecular approach, proved that biocontrol bacterium G01 was Pseudomonas aeruginosa.According tothe result of single factor experiments, the optimal carbon source of Pseudomonas aeruginosawas sucrose, the concentration was 1%, the best nitrogen source was peptone, the concentration was 1.0%, the best inorganic salt was K2HPO4?3H2O, the concentration was 0.3%. The results of orthogonal test showed that suitable medium consisted of 1.0% sucrose, 1.5% peptone and0.2% K2HPO4?3H2O, the best p H value of medium was 8, culture temperature was 27?, and bottling amount was 100 m L liquid medium in 250 m L flask.(3) The biocontrol bacteria TSA had an antagonistic effect on Fusarium oxysporum. Indoor and field pot experiment showed that the control effect of sterile extract was better than that of fermentation broth. The appraisal result of the microstructure, culture characters and molecular methodindicated that the biocontrol bacterium TSA was Bacillus subtilis. On the basis of single factor experiments, the optimal carbon source of Bacillus subtiliswas glucose, the concentration was 1.0%, the best nitrogen source was yeast extract, the concentration was 2.0%, the best inorganic salt was K2HPO4?3H2O, the concentration was 0.4%. The results of orthogonal test showed that showed that suitable medium consisted of 1.0% glucose, 2.5% yeast extract and0.3% K2HPO4?3H2O, the properp H value of medium was 8, culture temperature was 30?,and bottling amount was 80 m L liquid medium in 250 m L flask.(4)Over 100 mg/L pesticide‘Fu xing', ‘Kai run' and ‘Mi xian an'completely inhibited the growth of hyphae of Fusarium oxysporum by indoor medium method, and the semi-lethal concentration was 9.40 mg/L, 8.94 mg/L and 0.628 mg/L, respectively. Indoor experiment indicated that application of pesticide ‘Fu xing', ‘Kai run' and ‘Mi xian an' after inoculation, the incidence rate of stem rot in Yunv' was 66.67%, 70.00% and 63.33%, respectively, while that of CKwas 80.00%, demonstrating that the prevention effect was not good, in contrast, application beforeinoculation,the incidence rate was 16.67% 20.00% and 16.67%, being significantly lower than thant of CK(80.00%).Field trials showed that the incidence rate of spraying three agrochemicals(1000?) was 11.80%, 15.28% and 9.72% respectively, the incidence rate of spraying ‘Mi xian an' was significantly lower than that of CK(18.75%), suggesting that the prevention effectof ‘Mi xian an' on stem rot was the best.Through the above research, the control effect of silicon nutrition, biocontrol bacteria, and pesticides on stem rot disease of ' Yunv' was preliminary verified. The control technical systemof stem rot disease in Cym.'Yunv' was established. This layed the foundation for the comprehensive prevention and control of stem rot disease in 'Yunv' potted flower production. |
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