Study On Induced Resistance Of Tobacco Against Alternaria Alternata By Chinese Herbal Extract

Tobacco resistance against Alternaria alternata was tested after Chinese hebals extrct treatment.We established a procedure to study the potential biochemical mechanism during Chinese hebals extrct treatment tobacco against Alternaria sp.Both indoor and outdoor experiments were performed in my study and we got the following conclusions:1.Different concentrations of six Kinds from Chinese herbal extracts were applied for indoor bacteriostatic test.By measuring the rate of pathogen mycelial growth,the results show that: In the range of 10-160,there were no inhibitory effects on the growth of Alternaria sp.in the extracts of six Chinese herbal medicines,including rhubarb,galangal,clove,kudzu,angelica and rhizoma curculiginis.Therefore,it is considered that these six extracts have no significant reducetion against this disease,Aftrer treatment of tobacco plant leaves by extracts,the disease index decreased and induction effect increased.This showed that Chinese herbal medicine induced tobacco diseaseresistance.2.In the range of 10-160,Rhubarb and Angelica rhizome could induce tobacco to produce a certain degree of disease.And the resistance of tobacco plants was inducer dosage dependent.The results showed that the most obvious effect was diluted 40 times rhubarb extract and 20 times angelica extract,the effect was 49.93% and 47.61% respectively.3.Using diluted 40 times rhubarb extract and 20 times angelica extractatomize tobacco in adultplant stage.The tobacco plants were inoculated at 1d,3d,5d,7d,9d,11 d and 13 d respectively.After fifteen days investigate the incidence of the situation.The results of the investigation showed that the tobacco showed a certain resistance effect,the best effect was on the 5th day to the 7th day,and the disease resistance was at least 13 days.After the determination rhubarb,The best effect was 51.64% on the 5th day,Angelica sinensis was 48.74% lower than that of rhubarb,which may be related to the active substance in the extract.And after testing,rhubarb and Angelica treatment induced tobacco resistance to brown spot disease is systematic.4.The activity of POD,PPO and PAL in tobacco plants was significantly higher than that in tobacco plants treated with rhubarb and angelica,and the activity of these plants was closely related to the expression of resistance to disease.Effects of ahubarb and angelica on the biochemical mechanism of tobacco resistance to disease resistance.5.The results of field experiment showed that rhubarb and angelica rhizome extract could induce tobacco resistance to brown spot disease,the effect respectively is 43.29% and 44.66%.