The Application Technique Of Antagonistic Strains Against Tobacco Wilt And Black Shank

Soil borne pathogens often cause devastating diseases in tobacco production.Tobacco bacterial wilt and tobacco black shank are the most serious diseases in China.At present there are not effective bactericide or fungicide and good application technique for the two diseases controlling.The reasons of the pessimistic situation about diseases controlling included two sides:1) lagged study on bactericide exploiture directly leads to lack of agent for disease controlling.In addition,the excessive application of chemical pesticides not only produces pesticide-resistant pathogens,but also it brings environmental contamination even threaten to the health of human beings;2) the research on the technology of bactericide application to the disease control shows much unsubstantial.Moreover,the biological functions of antagonistic bacteria ought to rely on the synergism between two or more bacteria so as to play a better role.Therefore,this study of different combination and mixed in different proportion,was designed to filter out stable and effective combination,and then applying the combination for control trials in greenhouse which using different methods for tobacco diseases to find an effective method of application,and using this method to trials,to finally obtain the effective combination and effective control technology to control tobacco bacterial wilt and tobacco black shank,preparing for the further field experiment in the future.The detailed experimental results were as follows.1.Jointed restraining effect of different antagonistic strains on controlling tobacco bacterial wilt and black shankThe better biocontrol strains preserved in the laboratory were firstly screened to be used in next experiment.The results of pot culture experiment with different strains mixed in different proportions controlling tobacco bacterial wilt in greenhouse showed that:P-70-3 had the best control effect at 30 days after inoculating pathogen;the biocontrol effect was 81.96%.Through the pre-observation, it was found that the disease time of this processing was the latest.Therefore,the strain of P-70-3 was further used in the next tests.Similarly,the results of the ratio of different combinations of antagonistic strains against tobacco black shank in greenhouse showed that:comparison of the antagonistic effect of different volume ratio with the same concentration of P-70-3 and P-3-1's mixed-zymolysis,the combination v/v=4:1 of these two bacteria showed the best controlling effect at 25 days after inoculating pathogens,the seedlings were still alive,while tobacco plants in other treatments appeared diseased.2.The results of antagonistic bacteria in different application methods on tobacco bacterial wilt and black shank in greenhouse.Seven methods were adopted in antagonistic bacterial inoculation,including dipping root, soaking root,soaking seed,filling root,filling with dipping root,soaking root with filling root,and soaking seed with filling root.The results of controlling tobacco bacterial wilt in greenhouse showed that,the relative control effect of two ways combining were higher than one way obviously. At the same time,the relative effect of dipping root with filling root was higher than others after Ralstonia solanacerum were inoculated 25 days.Its relative effect reached 63.9%,which was higher than other methods clearly.There were six methods,such as root dip,root-soaking,seed soak,root irrigation,root-soaking and root irrigation,seed soak and root irrigation,in the greenhouse disease controlling experimentation of tobacco black shank.The experimental results showed that:in the early,the relative effect of various application methods was not significant difference.In the late,the relative effect of root-soaking with root irrigation was the highest(53.33%),which was significantly higher than that of other methods by a single application.But there was not significant difference between root soaking with root irrigation and seed soaking with root irrigation.In various management ways of the single application,the relative effect of root dip and root irrigation are both 30.00%,which were more effective than root-soaking or root-soaking.But significant differences were not found among them.3.The plot trial results of the antagonistic bacteria against tobacco bacterial wilt and black shankIn order to approach to natural conditions,the bacteria application technology was researched through designing diseased plots and controlled plots in the trial. The results of tobacco bacterial wilt in the plot trial showed that:treatment 1(to spray P-70-3 of the fermentation bacteria to stem one week before transplantation,to dip the root once at the time for transplanting,to irrigate the root once at seven days later,to irrigate the root once at another seven days later again);disposal 5(the root irrigation was conducted with the mix of salicylic acid and P-70-3 fermentation bacteria with the volume ratio of 1:1 ten days after them transplanted to the plots,and spray all the foliage to be wetness with a total three times for irrigation with spraying at every seven days.The best effect of irrigation fermentation bacteria showed at five days after the application for three times,the relative control effect was 48.91%and 49.27%respectively,at 35 days after inoculating pathogen.The trial results of black shank's tobacco showed that:treatment 2(to spray P-70-3 and P-3-1 of the fermentation bacteria to stem one week before transplantation,and to dip the root for one time when transplanting,then to irrigate the root one time seven days later,to irrigate the root for three times another seven days later again);treatment five(to irrigate P-70-3 and P-3-1 with the volume ratio of 1:1 ten days after transplanting them to the plots,and inoculated the pathogen five days later,irrigated metalaxyl-mancozeb three days later),it was found after inoculation of bacteria suspension 40 days,the relative controlling effect of these two treatments reached 85.98%and 88.89%,respectively.The results showed the control effect of irrigating root with antagonistic bacteria for more times was always higher than that of irrigating root for less times in the plot trial.