大豆根系分泌物中氨基酸对根腐病菌生长的影响

采用砂培和室内模拟方法，研究了两个抗病性不同的大豆品种水溶性根系分泌物中氨基酸组分随作物生长的变化；同时检测了培养基中添加大豆根系分泌物和纯品氨基酸对大豆根腐病菌菌落生长的影响。结果表明，添加大豆苗期和花荚期根分泌物均显著促进尖镰孢菌菌丝生长，添加成熟期根分泌物显著促进腐皮镰孢菌菌丝生长。易感根腐病大豆品种合丰25号花荚期以后根分泌物中氨基酸种类多于抗根腐病大豆品种绥农10号。感病大豆品种根系分泌的氨基酸总量随生育时期增加，在鼓粒期达到最高；抗病大豆品种根系分泌的氨基酸总量在花荚期最高。感病大豆品种根系分泌的主要氨基酸为精氨酸，抗病大豆品种根系分泌的氨基酸主要为天冬氨酸。氨基酸纯品培养中，添加精氨酸和酪氨酸处理的尖镰孢菌菌落直径显著高于不加氨基酸的对照菌落直径；添加丝氨酸和天冬氨酸的处理菌落直径则显著低于对照处理。同时，添加天冬氨酸的培养基上腐皮镰孢菌菌落直径显著低于不加氨基酸的对照。可见，不同大豆品种根系分泌物中氨基酸组分对病原菌生长起着一定的作用，其表现的作用受根际氨基酸种类和氨基酸浓度影响较大，对于不同病原菌的作用存在差异。

Effect of amino acids from soybean root exudates on hyphal growth of pathogenic fungi of soybean root rot

Root exudates of two soybean (Glycine max L. Merr.) cultivars, Hefeng 25 (HF25) and Suinong 10 (SN10), which were susceptible and resistant to soybean root rot, respectively, and grown in quartz sand, were collected with distilled water. The effects of the root exudates on hyphal growth of pathogenic fungi, Fusarium oxysporum Schlecht.(F. ox. Schlecht.) and Fusarium solani (Mart.) Sacc.[F. so. (Mart.) Sacc.], were tested. The results showed that soybean root exudates from both seedling and flowering stages stimulated hyphal growth of F. ox. Schlecht. Root exudates from maturing plants stimulated the growth of F. so. (Mart.) Sacc. There were 16 amino acids detected from HF25 root exudates, while 14 from SN10 root exudates. HF25 roots exudated more types and higher total concentrations of amino acids than SN10. The major amino acids in root exudates of HF25 and SN10 were arginine and aspartic acid, respectively. Bioassay demonstrated that arginine and tyrosine significantly stimulated hyphal growth of F. ox. Schlecht., but serine and aspartic acid inhibited its growth. Aspartic acid inhibited hyphal growth of F. so. (Mart.) Sacc. These results suggested that amino acids in soybean root exudates played significant role on hyphal growth of pathogenic fungi of root rot, and the effects varied with soybean cultivars, possibly related to types and concentrations of amino acids in their root exudates, as well as species of pathogenic fungi.