Primary Studies On Screening And Mechanism Of Chemical Resistance Inducer For Tobacco Black Shank

[ background] Phytophthora nicotianae var. breda de hann is one of main destructive diseases of tobacco, presently, which was aggravated, owing to the growing continuous cropping tobacco field acreage and increasing continuous cropping fixed number of years. People generally taked integrated pest control steps against this disease like resistant varieties, cultivation control and chemical pest control, etc. They obtained good results and problems simultaneity, especially 3"R" (resurgence, residue, resistance) problems caused by chemical pesticide. People are crying for choosing a new method, which has a broad spectrum of antibiotic activity, continuing effects and relative stability, nuisance -free, and that performance is convenience as fertilization, thus reduce economic losses greatly in safety and efficiency. With the gradual adoption of nuisance-free tobacco today, to achieve better controllability and preventability of pest control chemical inducers are used to develop the internal mechanism of plants. Because this method has many advantages, such as multiple and strong resistance, good sanitary, and so on, it is becoming one of the important methods of plant diseases control in modern times as well as the ideal methods of tobacco leaf diseases.[ Objects] Providing a foundation for developing mixture by elemental screening the stress resistance inducer. Offering a certain theory basis for development of inducer by physiological and biochemical analysis of tobacco and studying of induced resistance mechanism.[methods] Adopt phy3 disease strain of Phytophthora nicotianae var. Breda de Haan as inoculative bacterial strain. Use seedling stems were inoculated by mycelium as inoculative method. Use the culativar of Hongda with high susceptibility as testing material to screening inducer that were reported. Take method of bactericide virulence determination-method of growth speed to test chemical inducer has public nuisance or not. Choose orthogonal experiment to optimize IPT induced treatment conditions. Use physiologic and biochemical index to discuss induced resistance mechanism.[ Results]1, Virulence of disease germs of Phytophthora nicotianae var. Breda de Haanofphy3, phy6, phyl, phy4, phy2 and phy5 is 89.0%, 71.2%, 59.9%, 40.1%, 12.9%, 6.6% respectively, of which, the virulence of phy3 was strongest but phy5 weakest.2, There were three inoculative methods , suspend seeding stems were inoculated by zoosperm, suspend seeding stems were inoculated by mycelium and seeding stems were inoculated by mycelia. Inoculated with crocuses , which incidence of disease rate was separately as 80%, 70%, 100% . Inoculated to K.326 , which rate was separately as 60%, 50%-. 80%. Incidence of disease rate that seeding stems were inoculated by mycelia was the best , that suspend seeding stems were inoculated by mycelium was the worst.3, With presently preservation of 52 breed varieties of flue-cured tobacco, PVH01 was best against disease, 9601 of worst. Resistance of excellent the culativar of Hongda was only stronger than 9601.4, Preliminary screening 13 types of chemicals F, E, C, G, H, L> A, IPT, M, Q, R, S> T, with control efficiency to Phytophthora nicotianae var. Breda de Haan after seeding spraying. Treating inducer E with 200mg/L into application, control efficiency was high to 62.16%. Choosing M with 20.0mmol/L, IPT with 10.0mg/L,E with 25mg/L,Q with lOumol/L to application, the control efficency was respectively at 43.25%, 41.66%, 40.54%, 38.47%.5, The results of 8 kinds of chemicals pharmacodynamic test showed that 1.0 mmol/L chemicals H's inhibition rate was 47.02%;200 mg/L chemicals E's inhibition rate was 72.88%;50 mg/L, 200 mg/L and 500 mg/L chemicals T's inhibition rate was 30.41%,60.14% and 76.35% ; 1000 mg/L chemicals S's inhibition rate was 93.98%.This chemicals in its own concentration made little influence to growth of mycelia of Phytophthora nicotianae var. Breda de Haan. Chemical A,C,L , IPT played a only small part too even if in high concentration., Exclude chemical T, the others was stress resistance inducer without germicidal action.6, The best condition of IPT seeding spaying to the culativar of Hongda is...