The soybean susceptible cultivar Sloan and resistant cultivar Williams82 as well as nonhost common bean Yidianhong of Phythophthora sojae were cultivated by the method of situ soil culture,the root exudates were collected and measured the chemoattration to Phytophthora sojae zoospores,including the capacity of attractting zoospores,the promotion on encystment and germination of P.sojae zoospores.The results showed that daidzein and genistein were included in the host and non-host root exudates with no significant differences on concentrations.The root exudates of nonhost common bean Yidianhong contained 18,Williams82 contained nine,and Sloan contained five kinds of test amino acids.For the shared amino acids in the three root exudates,the concentration in non-host common bean root exudate was significantly higher than that in the host root exudates,and the concentration in the resistant soybean was slightly higher than that in the susceptible soybean.The root exudate of non-host common bean Yidianhong contained four,Williams82 root exudate contained five,and Sloan root exudate contained four out of six kinds of test soluble sugars.Gal was only found in Williams82 root exudate,Mal was absent in all three root exudates.Each single components had significant chemoattraction to P.sojae zoospores.Except for a few components such as Pro and Phe that inhibited germination of the cysts,others had significant positive chemoattraction to encystment and germination.The effect of isoflavone mixture,amino acid mixture and soluble sugar mixture on the chemoattraction of zoospores significantly delined compared to that of the sum of each component,the mixture of 18 kinds of amino acids and that of six kinds of soluble sugar inhibited germination of P.sojae zoospores.The mixture of all test components at their relative in situ concentrations in the root exudates exhibited significant reduction compared to that of the sum of the role of each component,the extent of reduction from strong to weak was non-host common bean Yidianhong,resistant soybean Williams82 and susceptible soybean Sloan.%用原位土培法种植大豆疫霉感病品种Sloan、抗病品种Williams82及非寄主菜豆一点红,收集3个品种根分泌物,分别测定根分泌物中异黄酮、氨基酸和可溶性糖种类及含量,从3个方面(游动孢子趋化性、孢子成囊率及孢囊萌发率首次测定单一组分和混合组分在相对原位浓度下对大豆疫霉游动孢子趋化作用.结果表明,寄主大豆与非寄主菜豆根分泌物中均含异黄酮daidzein和genistein,但含量未达到显著性差异.非寄主菜豆根分泌物中含全部供试18种氨基酸、Williams82仅含9种,Sloan为5种,共有氨基酸中,非寄主菜豆根分泌物中浓度均显著高于寄主,抗病品种略高于感病品种.测定6种可溶性糖中,非寄主菜豆根分泌物中含4种,Williams82含5种,Sloan含4种,其中半乳糖(Gal)仅在Williams82中存在,麦芽糖(Mal)在3个品种根分泌物中均不存在.所有单一组分对大豆疫霉游动孢子均具显著促进作用,除少数组分如脯氨酸(Pro)、苯丙氨酸(Phe)对孢囊萌发有抑制作用外,其他组分均显著趋化游动孢子成囊及孢囊萌发.异黄酮混合液、氨基酸混合液和可溶性糖混合液对游动孢子3个生理指标影响较各组分作用之和均显著减效,18种氨基酸混合液和6种可溶性糖混合液对大豆疫霉游动孢子萌发由促进作用转为抑制作用.将试验组分按其在3个品种根分泌物中相对原位浓度混合后,对游动孢子3个生理指标表现显著促进或抑制作用,且作用显著低于其SUM值,表明3类物质混合后减效作用显著,减效程度由强到弱依次为非寄主菜豆一点红、抗病品种Williams82和感病品种Sloan.
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