Abstract: Two kinds of oxygenated unsaturated fatty acids, i.e. 11(S),12(S),13(S)trihydroxy(9Z,15Z)-octadecadienoic acid and 11(R)-hydroxy-12(S), 13(S)-epoxy-(9Z, 15Z)-octadecadienoic acid were synthesized and tested on their biological activities in the resistance of rice seedlings to blast disease. Both compounds had weak suppression on the mycelial growth but apparent inhibition on the conidia germination of Magnaporthe grisea in vitro. Foliar application with either of these compounds at three-to-four-leaf stage of rice seedlings, followed in 2 or 5 days by inoculation with the compatible strain markedly reduced the disease severity. For the best expression of the induced resistance, the lag between induction and challenge inoculation for the hydroxy C18fatty acid was 5 days but for the epoxy C18 fatty acid was 2 days. The effective concentration of either of the chemicals for foliar application was 5 μg/mL, resulting in over 50% reduction in the disease seventy. Preinoculation of the pathogen followed in 5 or 10 days by foliar spraying of either compound at 5 or 10 μg / mL also suppressed the disease with significantly reduced lesion numbers and size. It appears that treatment with these unsaturated fatty acids before or after infection may enhance the rice resistance to blast disease.

Key words: Induced resistance, Magnaporthe grisea, Octadecadienoic acid

摘要： 研究了（１１Ｓ，１２Ｓ，１３Ｓ）－１１，１２，１３－三羟基０（９Ｚ，１５Ｚ）－十八碳二烯酸（Ａ）和（１１Ｒ）－羟基－１２（Ｓ），１３（Ｓ）－环氧－（９Ｚ，１５Ｚ）－十八碳二烯酸（Ｂ）的生物学活性。体外测试结果表明，这两种十八碳二烯酸对稻瘟菌菌丝生长只有轻微的抑制作用，而对分生孢子萌发则表现了较强的抑制作用，３－４叶期的水稻幼苗经这两种十八碳二烯酸诱发处理后均获得了对稻瘟病的抗性，减轻了稻瘟病的病情。用A处理后隔5 d接种稻瘟病菌，病情指数比对照降低64.8%；用B处理后隔2 d接种病菌，病情指数比对照降低69.8%。两种十八碳二烯酸均以5 μg/mL浓度诱发处理时，使水稻植株获得最大的诱导抗性。由A和B激发产生的诱导抗性对稻瘟病的防治效果均大于50%。先接种稻瘟病菌以诱发发病，而后隔5 d或10 d后喷施10 μg/mL的A或B水溶液，均可减轻稻瘟病的病情，其防治效果在44％－55％。

关键词: 诱导, 稻瘟病, 十八碳二烯酸, 水稻