| Tobacco wildfire is one of important bacterial diseases in tobacco,which is a major leaf disease of tobacco.This disease with a worldwide distribution,having fulminant prevalence,disseminated by airflow and wind-blown rain,which has been aggravated year on year.However,there are few studies on the effects of tobacco wildfire disease on the yield and output value of tobacco and the quality of tobacco leaves,and the damage of tobacco yield and quality can not be evaluated according to the occurrence degree of tobacco wildfire.The prevention and treatment of tobacco wildfire are mainly chemical agents so far,however,its side effect include pesticide residue,anti-drug and environmental pollution could not have been neglected.This paper studies the effects of tobacco wildfire disease on yield and chemical composition of tobacco and evaluates the effects of two microbial agents on the indoor and field control of tobacco wildfire disease.The inhibitory effects of two microbial agents on Pseudomonas syringae pv.tabaci were studied and the effects of two microbial agents on the defense enzyme activity of tobacco were researched.The main results are as follows:1.The effects of different disease grades on tobacco yield and chemical composition of tobacco leaves.By measuring the yield,output value and the main chemical components of 0,1,3,5,7 and 9 grade tobacco wildfire disease leaves.The results showed that when tobacco wildfire disease were 1,3,5,7,9 grade,the lower leaf yield loss rate were 3.00%,7.93%,10.49%,13.78% and 17.87%,respectively;the y i e l d l o s s r a t e o f m i d d l e l e a v e s w e r e 1.6 0 %,1 0.8 8 %,1 2.4 7 %,15.12% and 20.49%,respectively;the yield loss rate of upper leaves were 4.7%,10.43%,12.36%,16.53%and 18.51%,respectively.When the disease grade was 5,theyield loss rate of the lower leaves,middle leaves and upper leaves was about 50.95%,41.73% and 47.01%,respectively.The determination results of chemical composition of tobacco leaves showed that total alkaloids content,total nitrogen content,K content of disease leaves were increased with the increase of the wildfire level rise,However,the content of reducing sugar and total sugar showed the opposite trend.The occurrence of wild fire disease has a great influence on the chemical composition of tobacco leaves and the chemical composition of tobacco leaves is poorly coordinated.2.Bacillus subtilis and Paenibacillus polymyxa have significant inhibitory effects on Pseudomonas syringae pv.tabaci.The inhibitory effect of Bacillus subtilis and Paenibacillus polymyxa on Pseudomonas syringae pv.tabaci was determined by filter paper method.When treated with the low-recommended concentrations of streptomycin sulfate(0.18g/L),Bacillus subtilis(10 billion cfu/L)and Paenibacillus polymyxa(5 billion cfu/L),their antibacterial circle diameter was 21.5 mm,21.2 mm,21.4 mm,their inhibitory effects were 72.13%,71.64% and 71.91%,respectively.There was no significant difference among the treatments.When treated with the high-recommended concentrations of streptomycin sulfate(0.36g/L),Bacillus subtilis(20 billion cfu/L)and Paenibacillus polymyxa(10 billion cfu/L),their antibacterial circle diameter was 23.3 mm,23.5 mm,22.1 mm,their inhibitory effects were 74.23%,74.41% and 72.87%,respectively.There was no significant difference among the treatments.The antibacterial effect of Bacillus subtilis and Paenibacillus polymyxa were close to the effect of streptomycin sulfate on Pseudomonas syringae pv.tabaci.3.Bacillus subtilis and Paenibacillus polymyxs can improve the activity of tobacco defense enzymes,and the disease control effect is better.Bacillus subtilis and inoculation+Bacillus subtilis could increase the activity of tobacco PAL activity.The PPO activity of Bacillus,inoculation+Bacillus subtilis and inoculation+Paenibacillus polymyxa treatments was significantly increased for 1-11 days after treatment,the CAT activity was significantly higher than that of the control for 3 days.The CAT activity of inoculation+Bacillus subtilis and inoculation+Paenibacillus polymyxa treatments was significantly higher than that of control at 7-11 days.Compared with the control,the POD activity respectively were increased 0.55 times,0.60 times,1.21 times,1.21 times and 1.08 times.The results of indoor disease control test revealed the treatment effect of streptomycin sulfate,Bacillus subtilis and Bacillus polymyxa on wildfire disease respectively were 62.85%,64.24%,59.67% and the prevention effect respectively were 68.08%,65.88%,57.12% at 21 days after treatment.The two antagonistic microbial agents can significantly improve tobacco defense enzyme activity and improve tobacco disease resistance.4.Field application effect of Bacillus subtilis and Bacillus polymyxa.7 days after the fourth treatment,streptomycin sulfate,Bacillus subtilis,Bacillus polymyxa treatment control effeciency on tobacco wildfire disease were 71.07%,73.58%,67.49%.Compared with the control,yield of Bacillus subtilis,streptomycin and Paenibacillus polymyxa treatments respectively increased 15.85%,9.70%,7.80% and output value increased 22.55%,11.93%,11.17%,respectively.The chemical composition of tobacco leaves treated with Bacillus subtilis has the best coordination.Either concerned about tobacco yield or the quality of tobacco leaf,the endanger of tobacco wildfire disease should not be ignored.Through the expriments including antibacterial experiment,defense enzyme activity test,indoor control effect experiment,field control effect experiment,the results showed that the two kinds of antagonistic microbial agents(Bacillus subtilis and Bacillus polymyxa)on wildfire control effect is effective.Therefore,Bacillus subtilis and Bacillus polymyxa can be used in the control of tobacco wildfire disease on flue-cured tobacco production. |
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