连作大豆土壤病原菌的分离及其致病性的研究

Study on Isolation and Pathogenicity of Soil Pathogen in Continuous Cropping Systems of Soybean

在微生物３大类群中，细菌总数在整个大豆生育期内占绝对优势，重茬低于正茬，花期、结荚期尤为明显；放线菌数量总体变幅不大，花期、成熟期重茬高于正茬，而苗期则相反；真菌数量变化很大，重茬高于正茬，花期最为显著。在连作大豆根际土壤中，有益真菌减少，有害真菌增加。将真菌优势菌群中的尖镰孢菌、半裸镰孢菌和粉红粘帚菌回接大豆，均产生不同程度的致病性，导致大豆根腐病的发生，花期前后（３８～５０ｄ）病症明显。３菌株毒素粗提物对大豆毒害性试验结果表明：大豆发芽率显著降低，植株生长受阻。

The number of bacteria was dominant over other kinds of microorganisms in all growing stages of soybean in soil,the following soybean was less than that of soybean following other crops,especially in flowering and podding stage.The number of actinomycete doesnt changed evidently,and with soybean following soybean was higher than that of soybean following other crops in flowering and maturing stages,and was opposite in seeding stages.The number of fungi changed obviously,and in soybean following soybean was observed to be much more than that of soybean following other crops,especially in flowering stage.In rhizosphere soil of soybean following soybean,beneficial fungi decreased and pernicious fungi increased.The superior species of fungi, Fusarium oxysporum Schlecht, F.semitectum Berk.et Rav.and Gliocladium roseum (Link) Bain moculated into soybean could produce difference degree pathogenicity and led to soybean root rot,especially in flowering stage(3850 days).It has not been reported that F.semitectum Berk.et Rav.and G.roseum (link) Bain.may result in pathogenicity and soybean root rot.The toxicity experimental results on soybean by the unrefined extract of three fungi toxin manifest were the germination percentage of soybean decreased obviously,and the growth of soybean was hindered.