Selection And Mechanism Of Plant Defense Activtor Inducing Tobacco Against Tobacco Black Shank

Seven chemicals were used to control tobacco black shank and tobacco mosaic, and their effects were evaluated; the best one was selected and its effect to Phytophthora parasitica Var nicotianae was studied.In order to testify the result, a systemic experiment was conducted. In addition to these, the interaction between PDJ and other chemicals was studied and the primary studies on the mechanism of PDJ inducing the resistance of tobacco were also undertaken.The results of seed soaking and seedling spraying showed that all of these seven chemicals could induce the resistance of tobacco to black shank, but their effects were different. The effect of PDJ was the best among them, which could reach above 60% when tobacco seedling was sprayed with 100 mg/L PDJ. And the effect was higher when the tobacco seeds were soaked with 100mg/L PDJ,which could reach 70.83%.As for tobacco mosaic, these seven chemicals didn't have notable effects. Although PDJ had higher effect than the others, its effect was not prominent. We studied the effect of PDJ on Phytophthora parasitica Var nicotianae, including on the development of mycelium, the producing of sporangium, the releasing of swarm spore and the germination of dormant spore. It showed that PDJ had little influences on the four life processes. Therefore we draw the conclusion that PDJ could induce tobacco's resistance to black shank.In order to testify the conclusion, we conducted a systemicexperiment, that is to say, we treated the lower leaf with PDJ and inoculated the upper leaves. It showed that 100 mg/L PDJ and 200 mg/L PDJ could significantly reduce the diameter of lesions, and the suppressions of the lesion diameter on the fourth leaf were 65.38% and 57.69% respectively. As for the fifth leaf and the sixth leaf, the suppressions of 100mg/L and 200 mg/L PDJ were both about 60%.Basing on this results, we concluded that PDJ could induce the resistance of tobacco, and this resistance was systemic.The results of different inoculation time showed that PDJ had the best effect to black shank when we inoculated tobacco three days after PDJ-treatment. And the effect reduced gradually and it could last about 15 days.The joint effects of PDJ with other six chemicals were almost additive; expect that PDJ incorporating with ABA showed a little synergistic effect.PDJ treatment could increase the activities of peroxidase (POD) and phenylalanine ammonialyase (PAL), and it had little influence on catalase (CAT).But the POD and PAL activities pinnacle of root were later than that of leaves. Inoculation also could induce the activities of POD,PAL and CAT, but this trends were different between PDJ treatment and CK(water treatment).The activities of POD,PAL and CAT in PDJ-treatment-and-inoculation tobacco were higher and could last more days.The result of SDS-PAGE analysis showed that PDJ could induce some pathogenesis-related proteins,among them Rf＝0.11,0.28 and 0.57 proteins had a higher expression quantities. Inoculation also could induce PRP, but the concentration of PRP bands are different.All these five protein bands had a higher expression quantities in PDJ-treating tobaccos than in water－treating tobaccos.The study on the influence of PDJ to osmotin and CDPK2 genes showed that PDJ could induce the expression of osmotin gene, and it had no influence on CDPK2.Inoculation also could induce osmotin expression, but in PDJ-treating tobacco osmotin genes could express more days.