Induced Resistance In Eggplant Against Verticillium Wilt Disease By Exogenous Chemicals

The eggplant Verticillium Wilt caused by Verticillium dahliae Kleb was an important epidemic disease in recent years. Effects of 5 exogenous chemical compounds on induced resistance to Verticillium Wilt and physiological mechanism induced by Jinggangmycin A (JA) were studied systemically.The research gave the following results:Measurement of colony diameter and conidial germination of Verticillium dahliae showed that within certain concentrations these chemicals had no significant influence on growth of the pathogen.These inducer candidates were safe to eggplant.The induced resistance was detected after eggplant being treated with these inducers and challenge inoculated with Verticillium dahliae.Kesults showed that 5 chemicals were effective to induce resistance. Several of them greatly reduced the disease caused by Verticillium dahliae Kleb and could be good inducers. Among them, JA was the most effective and reduced disease severity, relative to controls, by up to 48.5% and the effects of Riboflavin, Vitamin K₃, were 27.0%, 22.3%, respectively.Furthermore, there were significantly different effects with different chemical compounds. Different chemical combinations could influence the significance of induced resistance. Moreover, growth stage of plant was another important factor for efficiency of induction. The induction resistance was more effective at seedling stage than at booting stage.Dose of inducer was significant for efficiency of induced resistance. Efficacy of JA increase with the applied concentration.And so was it with Riboflavin and Vitamin K₃ with certain concentrations, but the efficacy decreased with high doses. When the leaves were treated with 1.0mmol/L Riboflavin or 0.5 mmol/L Vitamin K₃ would also lead to reduce of disease severity, the effects were 26.9%, 25.3%, respectively.The optimum concentration of JA treatment to induce resistance of maize seedlings was 100μg/mL, which showed requirement of induction with high concentration of JA from Verticillium dahliae. The highest level of induced resistance was acquired when eggplant leaves were sprayed with 100μg/mL JA and inoculated with fungal spore suspension three days later. In JA-treated eggplant seedlings, induced resistance was demonstrated to be lasted for 10-15 days.Defence enzymes PPO, POD, PAL and CAT played important roles in induced resistance to Verticillium Wilt. Jinggangmycin A treatment dramatically increased relative activity of these enzymes. The activity of some of them increased transiently soon after induction, most of them only increased remarkably after challenge inoculation. The content of Malonaldehyde (MDA) was declined along with the day after treating with JA.Therefore, the remarkable increase of the enzyme in plants treated with JA and then inoculated with Verticillium dahliae, which evidently revealed that the decrease in disease severity following treatment with these agents was a result of resistance induction.Furthermore, when the lower three leaves were sprayed with 100μg/mL JA before challenge inoculation, activity of the defence enzymes was increased on the unspayed upper leaves. Results showed that resistance of eggplant by exogenous chemicals were typically a systemic acquired resistance (SAR) characterized by systemicity and durability.