Researches On The Relationship Between Root Exudates Of Different Flue-cured Tobacco Varieties And Resistant Of Black Shank Disease(Phytophora Parasitica Var. Nicotiana)

In this study, two different varieties of tobacco resistant to tobacco black shank (No.3, Xiaohuangjin1025) and their grafted varieties was used as test material. The difference of different tobacco varieties of root exudates component and its correlation with the resistance of varieties was studied by water immersion and training method, GCMS and so on, and the floristic differentiation of microbial population and number of different tobacco rhizosphere was also studied by metagenomic sequencing, OTU taxonomy statistics and so on, in order to make clear the happening mechanism of tobacco black shank, enrich the research of tobacco black shank resistant mechanism, and provide the necessary theoretical basis for the development of disease biology control. The main results are as follows:(1) Through the identification of resistance of different tobacco black shank, high disease resistance and high susceptible varieties (No.3and Xiaohuangjin1025)were selected, and the effect of grafting between different resistant varieties on the resistance of tobacco black shank disease through soil was discussed. The results showed that grafting can change the resistance of tobacco varieties, and the trend depends on the resistance of grafted top spike, and resistance of stocks is still the determinants of the grafting varieties resistance.(2) By the root-dipping method, tobacco root exudates were collected, and specific compositions and their difference of root exudates of different tobacco varieties were analyzed by GC-MS. The contact between tobacco varieties resistance difference and root exudates component difference was explored, and the mechanism of tobacco resistance was illustrated from root secondary metabolism. The results showed that the tobacco root exudates mainly composed of long chain aliphatic hydrocarbons, benzene,esters, acids and a small amount of phenols. The detection component and content of root exudates were different for different tobacco varieties. There were many Eugenol, ester, and acid material in resistant varieties, while in root exudates of susceptible varieties, there were many4-tert-butylphenoll and2,4-di-tert-butylphenol. This shows, the difference of varieties resistance may have an important connection with difference of analyzed secretions.(3) There are differences between the effect of root exudates of different resistant varieties on tobacco on the growth of Phytophthora nicotianae pathogens. Adding root exudates of resistant varieties can restrain the growth of Phytophthora nicotianae mycelium to some extent, whereas the root exudates of susceptible varieties promoted or partly promoted the mycelium growth; the addition of root exudates of susceptible varieties had significantly promoting effect on the formation of pathogen sporangium and releasing of zoospore release, but the addition of root exudates of resistant varieties had few promoting even inhibition effect on formation quantity of pathogen sporangium.(4) There were differences between the effect of exogenous simulating allelopathy materials of different types and concentration on the growth of Phytophthora nicotianae. With the increasing of phthalate concentration, its effect on the growth of mycelium changed from promoting to restraining, and the promoting effect increased first and then decreased; while with the increasing of concentration of Myristic acid, palmitic acid and lauric acid, their restraining effect decreased first and then increased. The restraining effect of2,6-di-tert-butylphenol strengthened with the increasing of its concentration, and decreased after reaching the concentration of0.1mmol·L-1;while at a low concentration, p-hydroxybenzoic acid showed a promoting effect, but the promoting effect changed into a restraining effect and the restraining effect strengthened with the increasing of its concentration. The function of important root exudates components during its interaction with Phytophthora nicotianae pathogens was clear, and mechanisms of resistance was revealed.(5) By454macro genome sequencing method, the diversity of rhizosphere microbial community structure of different tobacco varieties was analyzed. The results showed that the number and diversity of rhizosphere bacteria and actinomycetes were positively correlated with tobacco resistance, while the number and diversity of fungi was negative correlation with tobacco resistance. There were significant differences of microbial composition at the class level with the changing of crop resistance, and the relationship between disease resistance of crop and Rhizosphere microorganisms was explored from the microorganism floristic differentiation standpoint.