Occurrence,Epidemic Regularity And Control Countermeasures Of Tobacco Wildfire Diseases In Chenzhou Area,Hunan Province

Tobacco wildfire disease is a bacterial disease caused by Pseudomonas syringae pv.tabaci which can endanger leaf,flower,capsule,seed and other parts of plant.It is a common bacterial disease in the major tobacco producing countries in the world,especially in USA and Germany,even is fatal.In recent years,the large-scale cultivation of flue-cured tobacco without the characteristics of resistance to wildfire disease,single plant variety and other reasons,making the tobacco wildfire disease has become increasingly serious and gradually become a major obstacle to the development of tobacco production in China.To clear the occurrence,epidemic regularity and effective control technology of tobacco wildfire diseases,we carried out the systematic studies of constructing the forecasting model,identifying the pathogen,screening the bio-control bacteria and medicament of tobacco wildfire disease in Hunan Guiyang tobacco area.The results are as follows:Constructing the prediction model of tobacco wildfire disease in tobacco-growing area of Guiyang,Chenzhou.To design such a model,we collected data for 40 wildfire disease indices via tobacco field surveys and data for 15 climate factors of Guiyang County in China from 2012 to 2016.Firstly,we built 10 modeling methods and found that SVR had better prediction ability to this given dataset.Secondly,we built the corresponding models using 15 climate features and an in-house WDEM method(the worst descriptor elimination multi-roundly),and the independent test results showed that the best SVR model had not only a higher predictive accuracy(2 extQ = 0.94)but also a better stability.Finally,we further evaluated the biological significance of their retained climate features and the single-factor effects of the best model according to the interpretability analysis,and our results indicated that 1)the three climate factors(minimum value of wind velocity,daily range of temperature and daily pressure)strongly affected the occurrence of wildfire disease;2)the ranges of relative humidity and sunshine hours were negatively correlated with the occurrence of wildfire disease,while daily mean vapour pressure was positively correlated with the occurrence of the disease.Our work enables a useful theoretical prediction for wildfire disease,especially in terms of climate-related predictions.Identifying initially the wildfire pathogens in Guiyang as Pseudomonas syringae pv.tabaci.By indoor separation and purification,the suspected pathogens were screened from the samples of tobacco area in Guiyang.16 S r DNA of the suspected pathogens were blasted in ribosome database,there were 5 strains shared more than 99% similarity with Pseudomonas syringae.The sample YH-1,YH-6 and YH-7 had the highest similarity with the sequence of tobacco wildfire disease strain,reaching 100%,and it was judged that these 5 sample was the pathogen of wildfire in Guiyang tobacco area of Chenzhou.Screening bio-control bacteria and medicament of the wildfire disease.The preliminary identification of the antagonism of the selected strains by paper disc method was carried out.The results showed that the 16CZ-11,16CZ-14 and 16CZ-25 from the stem and leaf of the healthy tobacco from the Wulong Village,Aoquan Town,Guiyang County,Chenzhou County,Hunan Province,all formed an inhibition zone on the culture dish.The diameter of the inhibition zone was 6.00 mm,5.50 mm and 7.25 mm,respectively.Compared with the other strains with inhibition zone,the antagonistic effect of 16CZ-25 was the most obvious,therefore and the effect of 16CZ-25 was the best;the homology of 16CZ-11 and Bacillus licheniformis reaches 100%,the homology of 16CZ14 and Stenotrophomonas maltophilia reaches 99%,and the homology of 16CZ-25 and Bacillus subtilis also reaches 99%.Experiment on prevention and cure of tobacco wildfire disease with different medicament was carried out.Results showed that mancozeb,carbendazim and Bacillus polymycoides had good control effect on tobacco wildfire disease,besides some medicament identified to control wildfire disease on the market.