两种十八碳二烯酸诱发水稻对稻瘟病的抗性及其防病作用

Effect of Two Octadecadienoic Acids on Rice Resistance to Blast at Seedling Stage

研究了（１１Ｓ，１２Ｓ，１３Ｓ）－１１，１２，１３－三羟基－（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病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叶期的水稻的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５ｄ接种稻瘟病菌，病情指数比对照降低６８．４％；用Ｂ处理后隔２ｄ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５μｇ／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，而后间隔５ｄ或１０ｄ后喷施１０μｇ／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％之间．

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 Magnaporthegrisea in vitro.Foliar application with either of these compounds at three-to-four-leaf stage of rice seedlings, fol.lowed 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 sμg/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 10μg / 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.