Studies On Resistance To Powder Mildew And Signal Transduction Pathway Of Muskmelon Induced By BTH

Northwest region is the mainly area for growing muskmelon in China,but the production of muskmelon was badly decreased by diseases in recent years,and the metheds of resistance to disease have many shortages.Researchers found that induced resistance to disease was a more healthy and safer way, but about its mechanism to resistant to diseases had a few researches.Thus,it is useful to study the physiological mechanism of resistance to disease and signal transaction pathway.In this paper, two different melon(Kalakesai and Tam Dew) were treated by 0.35 mmol·L-1 BTH at 5-leaf stage, inoculated with Sphaerotheca fuliginea seven days after spraying with BTH, at the same time,the Kalakesai and Tam Dew calli were cultured on MS medium contained 5 mmol·L-1coffeic acid (CA)and/ or 10 mmol·L-1 CoCl2 (25±2℃), while BTH were sprayed to the calli.the ROS production and resistance enzymes were studied.The results showed that the activities of POD,PPO,PAL,the production rate of O2.-,the content of H2O2 and the activities of SOD were increased by BTH treatment and inoculated with Sphaerotheca fuliginea ,but the activities of CAT were decreased, not only for treated leaves, but also for induced leaves. So we can say maybe BTH had effects of resisting mildew powder by increasing resistance enzymes and reactive oxygen species (ROS), and had effects of systemic induction to them.For different varieties, the increasing of PPO of Tam Dew was earlier (or stronger)than Kalakesai,and the increasing of PAL had no differences between the two varieties,but for response time,Tam Dew was earlier than Kalakesai.For the production rate of O2.-, the content of H2O2,the activities of SOD and CAT,the effects of BTH to Tam Dew were all stronger than to Kalakesai.The results for signal transaction pathway showed that there were different pathways of signal transduction in induced different resistance enzymes,ET plays a main role in POD and PPO activities induced by BTH , while on PAL there exists another pathway.The effects of BTH on O2.-,H2O2 and CAT may be through the signal transduction of SA, and on SOD may be through both SA and ET signal transduction.