The Mechanism And Effect Of Polaramycin On Magnaporthe Grisea

Rice blast, caused by Magnaporthe grisea, is an important disease in temperate flooded and tropical upland (rainfed) rice cropping systems. Polaramycin A and B are a new group of polyol macrolide antibiotics which includes 36 loops. They have broad spectrum antimicrobe activity, and can effectively inhibit yeast, fungi and bacterium. The main purposes of this study include searching an effective biopesticide to control rice blast and evaluating the effect of Polaramycin against blast. The relationship among rice, Polaramycin and Magnaporthe grisea was investigated. The mechanism of PAL on the induction of resistance to rice blast was explored.The primary results are listed as follows:1. Intensive inhibitory effect of polaramycin on spore germination and mycelium growth of M grisea was detected in vitro when its concentrations were 5 g/ml and 10 g/ml. The inhibitory rate was 95.63% and 99.02% respectively. However, even if the concentrations of Polaramycin increased 10 times to 50 g/ml and 100 g/ml in vivo, it didn't show any effect on rice blast. In a word, the effect of polarmycin on plant disease were very different in vitro and in vivo2. The spores of M. grisea could germinate on rice and other plant, such as the lamina of cucumber and some grass. The signal factors which induce germination of M grisea spores were very common on the laminae of plant. The spores of M. grisea were inclined to germinate in acid conditions. Glucose couldn't stimulate germination of M. grisea spores. The preliminary study of relationship among rice, polaramycin and M.grisea., hydrophile substances and hydrophobe substances isolated from rice leaf couldn't stimulate germination of spores. Furthermore, some rice leaves were grinded, and lixiviation substances were collected. But they hadn't effect on germination of spores. We can't find active substances in M. grisea spores germination liquid which affected the germination of spores, and no gas were found from rice leaves which stimulate germination of spores.3. The effect of polaramycin to induce PAL activity in rice was studied. When polaramycin liquid was sprayed to rice plants, the PAL content of rice plants increased rapidly in the first 12h. The results showed that PAL was induced by polaramycin. However, when rice plants were treated with 50ug/ml and 100 g/ml polaramycin, the PAL content of rice descended quickly in 24h, which were lower than CK. Therefore, when polaramycin liquid was sprayed to rice plants, it induced substances which had the effect to restrain or decompose PAL.