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) office 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 resuits also showed that nitrogen fertilizer might play an important role in regulating activities of dofence enzymes in rice.%为明确氮肥处理下3个不同抗性水平的水稻品种特优627(抗)、D奇宝优527(中抗)和汕优63(感)的抗瘟性变化及其生化机制,使用不同剂量碳酸氢铵(纯氮17.1%)作为水稻苗期氮肥不同处理水平,测定了3个品种水稻苗的过氧化物酶(POD)和超氧化物歧化酶(SOD)活性及温室人工接菌条件下的苗瘟、叶瘟和穗瘟病情指数,并分析了酶活性变化与水稻植株抗稻瘟病的相互关系.结果表明:苗期增施氮肥后,3个品种水稻苗的POD活性明显下降,SOD活性明显增强.水稻植株受稻瘟病菌侵染后,苗期增施氮肥显著增加了3个品种水稻苗瘟和叶瘟病的发生,且感病品种汕优63的SOD、POD活性和病情指数变异幅度显著大于抗病和中抗品种.3个品种水稻苗POD活性与苗瘟病指呈负相关,相关系数为-0.9513、-0.9726和-0.8487;而SOD活性与苗瘟病指呈正相关,相关系数为0.9209、0.9649和0.9579,说明氮肥对水稻保护酶活性具有调节作用.
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