| As an fungal endoparasites of soybean cyst nematode(SCN)juvenile,Hirsutella minnesotensis was a potential biological control agent.To discuss the mechanism of Hirsutella minnesotensis on SCN,the effect of Hirsutella minnesotensis1-10 metabolites at the original and different dilute solution on the egg hatching,the activity of second stage juveniles(J2) and the attraction of J2 to soybean root diffusate or soybean root on agar plate were investigated in laboratory;the effects of different H.minnesotensis isolates and different fungal inoculation on both population and distribution of SCN and growth of soybean was evaluated in greenhouse experiments.It was deduced that the original and different dilute solution of 1-10 metabolites could significantly restrain the egg hatching and the activity of J2.The egg hatching suppression rate of the metabolites at the original was the highest to100%compared with the control;5×,10×, 20×and 50×metabolites on the suppression rate of the egg hatching were 45.2%,26.6%, 21.7%and 17.7%.The effect of the 1-10 metabolites at the original,5×,10×,20×and 50×on the mortality of J2 were 91%,75%,50%,36%and 31%after 24 hours.The difference between these treatments and water control were significant,which proved that the mortalities of the 1-10 had a high insecticidal activity of J2.As the time went to 48 hours,the mortalities of the 1-10 original metabolites on J2 was100%and the mortalities killed J2 significantly and consumingly.The results showed that J2 moved slowly towards 1-10 metabolites and were repelled by 1-10 metabolites,according the lowest distribution rates of J2 on 0～1cm area and the highest distribution rates of J2 on 2～3cm area nearby filter paper strips.In these same areas,it showed that J2 were quickly attracted toward to the root diffusate according the complete opposite distribution rates to the anterior one.Further more,J2 were significantly lower in the 0～1cm area and higher in the 2～3cm area treated by mixture of root diffusate and 1-10 metabolites than the sterile water(P＜0.05),so J2 were repelled obviously by the mixture.The same result was obtained by using soybean roots or the roots dipped with 1-10 metabolites(P＜0.05).It is deduced that 1-10 metabolites can reduce the tendency of soybean cyst nematode toward soybean roots.In greenhouse experiments,200cm~3 autoclaved soil(per pot) was added 0.4g of fungal fresh mycelium against soybean cyst nematode 9,000 eggs/300cm~3 soil.35 days after fungal inoculation,there were significant growth effects on soybean by both of H.minnesotensis isolate 1-10 and isolate HLJ07-21-3 as compared with soil-only control.The plant fresh weight of shoots and roots were both increased,and the plant fresh weight increase rats were 30.98%, 27.66%,respectively.The treatment inoculation with SCN and fungi as compared with SCN-only control reduced nematode population,especially the number of eggs,and it significantly affected the nematode distribution,especially the number of females on the root and cysts in the soil.Compared with HLJ07-21-3,1-10 significantly affected the nematode population, decreased the number of nematode in the pot by 43.6%as compared with SCN-only control.In greenhouse experiments,the inoculation of H.minnesotensis isolate 1-10 were 0.2,0.4 or 0.8g of fungi fresh mycelium,and the investigation was 35 days after fungal inoculation. There were significant growth effects on soybean by three inoculation of H.minnesotensis isolate 1-10 as compared with soil-only control,for the plant fresh weight increase rats were 21.12%,29.20%and 27.27%,respectively,and for the significant increase of the height of plant(P＜0.05).Only the treatment inoculation with SCN and 0.8g of fungi significantly increased the growth of soybean(P＜0.05),and its plant fresh weight increase rat was 19.65% compared with SCN-only control.As compared with SCN-only control,the treatments inoculation with 0.2,0.4 or 0.8g fungi reduced nematode population,especially the number of eggs,and they significantly affected the nematode distribution,especially the number of females on the root and cysts in the soil.The three different inoculation of 1-10 significantly decreased the the number of nematode in the pot by 30.2%,40.9%and 39.2%as compared with SCN-only control,meanwhile.0.4g fungi had the most significant effect on the nematode population.
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