Benzothiadiazole-induced Resistance In Wheat Against Blμmeria Graminis F.sp.tritici

Powdery mildew is one of the most primary disease in wheat cultivation in China. Powdery mildew has developed seriously with the change of agriculture farming system from the late 70s of the last century. Powdery mildew has been a seriously disastrous disease in agriculture production. In 1990, the area infected by powdery mildew is 1.83 fold of the area infected by yellow rust and the losses caused by powdery mildew exceeded the losses caused by yellow rust. So strengthen control for powder mildew is very important. Some elicitors stimulate plants and then cause the defense system of plant, which can results in resistance to subsequent infection, this is induced resistance. For its advantage, such as safety, broad spectrum disease control, it has been paid attention for a long time.In the research, we study the resistance of wheat against powdery mildew induced by BTH and we study the resistance mechanism too. We found BTH can induce obvious resistance in wheat against powder mildew.Spraying on the wheat with BTH at different concentration, can induce obvious system resistance to wheat powdery mildew. But 0.3mmol/L is the most effective induce density, the induced resistance can be transmitted. We also found the shortest interval between BTH and inoculation is one day, then the best interval between BTH and inoculation for wheat seedling is six day. The endurance of induce resistance is more than eighty days. Histopathology research indicates that, though BTH can decrease the penetration efficacy and development of powdery mildew, suppression of germination was not observed. Spraying on the diseased wheat with BTH, we did not find the pathogen was effected directly . It shows that BTH and its metabolites have no immediate activity against pathogens and are in accordance with criterion of chemical elicitor. The fact also indicates that the decrease in disease index caused by BTH is due to the increase of resistance in wheat itself.The activity of PAL, PPO, chitinase and β-1,3-glucanase all increased to different extant after treatment of BTH. The activity of PAL increased the most quickly, it reached higher only one day after BTH treatment. The activity of PPO had been increased after BTH treatment and reached the maximum one day after inoculation. The change tendency of the activity of chitinase is almost the same as that of β-1,3-glucanase.Both chitinase and β-1,3-glucanase activity reached a plateau six days after BTH treatment, and reached the maximum two days after inoculation. The research indicated that the activity of PAL, PPO, chitinase and β-1,3-glucanase were in significant relation with the induced resistance.