Influence of nitrogen on the activities of POD and SOD in rice seedlings and the incidence of rice blast disease.

In order to know biochemistry mechanism of resistance change to rice blast disease in rice varieties Teyou 627(R),DQibaoyou 527(MR) and Shanyou 63(S) after NH4HCO3 application,the activities of peroxidase(POD) and superoxide dismutase(SOD) in the seedlings of 3 rice varieties,the disease severity indices(DSI) of rice seedlings,leaves and neck blast with artificial inoculation were studied,the relationships of POD,SOD activities change and occurrence of rice seedling blast disease were also analyzed.The results showed that POD activities decreased,while SOD activities increased obviously with the increasing of nitrogen levels.It was also proved that higher level nitrogen application increased occurrence of rice seedlings and leaves blast,and the alteration extent of DSI and enzymes activities in Shanyou 63(S) were higher than that in Teyou 627(R) and DQibaoyou 527(MR).There was a significant negative relationship(r=-0.9513,-0.9726,-0.8487) between POD activities and DSI,and a significant positive relationship(r=0.9209,0.9649,0.9579) between SOD activities and DSI in the three varieties.The results also showed that nitrogen fertilizer might play an important role in regulating activities of defence enzymes in rice.