| The cabbage is widely cultivated around the world. Cabbage is an important cruciferous vegetable crop in China, is one of the most important vegetables crops.The brassica clubroot is a kind of worldwide disease which is caused by Plasmodiophora brassicae Woron and is an important root disease of cruciferous plants. It mainly harms cruciferous vegetables such as Chinese cabbage and mustard. The spores of Brassica clubroot resistance is strong, long service life, once the soil was polluted, it will no longer be suitable for cultivating cruciferae. The yield decreased after infection, and this will result in huge economic losses.In recent years, the use of exogenous substances can induce the fruit and vegetable produce systemic acquired resistance to prevent the fruit and vegetable diseases. Salicylic acid is a kind of small molecular phenolic compounds and has been widely used in disease resistance and stress resistance of plants in the last century, and has significant relieving effect. Rapid activation of various defense responses in processing plants after Benzothiadiazole, and inducing signal processing plant disease substance, the activation was conducted by other parts of the resistance mechanism.In this study, Two exogenous substances (SA and BTH) were wtreated with different concentrations on two Cabbage cultivars o, selected the best induction effects of clubroot resistance in the seedling stage; Through two different concentrations of exogenous substances after treatment, the cabbage seedlings were measured two days for a related physiological indexes, and then discussed the induction mechanism of induced resistance agent. The results are as follows: 1. Influence to clubroot incidence and disease index for diffent SA concentrations in two cabbage cultivarsDifferent concentrations of salicylic acid induced different cabbage,and with the increasing of concentration,disease index will be decreased, and induction improve controlling effect, but the induced effect declined after reaching a certain concentration. SA of different concentration induced diffent resistance effect in different cabbage seedling.For the Jingfeng and Xiyuan,it is the incidence of two-leaf>one-leaf>four-leaf, and the incidence rate of Xiyua is less than Jingfeng, this showed that the best inoculation period is two-leaf. The concentration of SA was 0.5mM, in the two cultivars at two-leaf is to the best induced effect, induced resistance index were 59.6% and 64.2%. But the concentration of 1mM in treatment of cabbage seedling damaged leaves,and resulted in some dry yellow leaves, and some leaves had withered, and produced toxic effects.2.Influence to clubroot incidence and disease index for diffent BTH concentrations in two cabbage cultivarsafter inoculation, two cabbage varieties showed different degrees of the disease, the change laws of the disease index is not the same. Different concentrations of BTH on cabbage caused different induction effect, with the increase of concentration, the disease index decreased, Induced resistance effect was different in different cabbage seedling. For the Jingfeng and Xiyuan it is the incidence of two-leaf>one-leaf≈=>four-leaf, and the incidence rate of Xiyua is less than Jingfeng, this showed that the best inoculation period is two-leaf period. Compared with the other two seedling, the best concentration inducing resistance is 0.5mM, but the induced effect of 0.1mM and 1mM concentration are nearly same in the one leaf and four leaf stage. Treatment oflmMBTH concentration do not caused dry yellow of cabbage leaves.3. Influence to related enzyme of defense responses for different salicylic acid (SA) and benzothiadiazole (BTH) concentration treatment in two cabbage varietiesThrough the research and analysis, in the two leaf stage of cabbage seedlings after inoculation, the protective enzyme activity induced was significantly higher than that of control, while the oxidation products of MD A membrane and osmolyte content of Pro were lower than that of the control. Compared with the control treatment,0.5mmol/L SA and 0.5mmol/LBTH can effectively improve the cabbage seedlings SOD and POD activity, CAT activity, PAL activity, APX activity and soluble protein content increased significantly and maintained at a high level.The results of the study show that,0.5mmol/L SA and BTH in two-leaf period of cabbage seedlings, can make the osmoregulation ability to enhance, increase the activity of antioxidant enzymes and antioxidant content, and enhance the ability of cells to scavenge active oxygen, so as to reduce the active oxygen damage to the cells, improve plant resistance to clubroot. |
