Principles And Practice Of Arbuscular Mycorrhzial Networks In Preventing Soil Contamination By Phytophthora Capsici Leonian

Soil biological pollution and prevention has become the research frontier of agricultural environmental engineering since biological pollution could cause soil environmental quality deterioration and related production damage.Pepper Phytophthora blight,which is caused by Phytophthora capsica,has been considered one of the most devastating soil-borne diseases.Arbuscular mycorrhizal（AM）fungi to help inhibiting soilborne diseases.But,little researchs have looked at the variation of soil indigenous AM fungi and their contribution to preventing Phytophthora blight.In this study,agroecological engineering was used to study the prevention and control effect of AM fungi on Phytophthora capsici under different fertilization amounts and intercropping conditions,it is important to make it an eco-friendly measure to deal with the proliferation of harmful microorganisms in soil and make the agricultural environment sustainable development.The general conclusions are as follow:Firstly,along with soil P.capsica contamination and pepper Phytophthora blight intensification,soil p H and organic C and concentrations decreased,while the content of soil acid phosphatase and available phosphorus were significantly increased.The p H was between 4.40 and 5.50 when pepper Phytophthora blight intensification.Organic carbon content decreased by 33.33%,total nitrogen decreased by 35%,acid phosphatase activity increased by 14%,and available phosphorus content increased by 65%.That also has adverse effects on the growth of AM fungal.Compared with healthy plants,the number of AM fungal decreased 3000 copies g^-1,and mycorrhizal consolidation rates decreased 40%,and the community structure has changed,Shannon index decreased by 20%,the observed OTU index decreased by 37.5%,and the ACE index decreased by about 60%.Redundancy analysis showed that the wilt severity negatively correlated with mycorrhizal consolidation.Secondly,0.015 kg of Phytophthora capsici were seeded in sterilized soil of every pot resulted in severe pepper blight,and the inoculation of AM fungi could significantly reduce the number of Phytophthora capsici in the soil by 47%and the epidemic index ofcapsici by 35%.Intercropping maize significantly increased the infection rate of AM fungi in the root system of pepper by 50%,further reduced the number of Phytophthora capsici in the soil to 70%and the epidemic index of pepper by 50%,and significantly increased the yield of pepper fruit by 35%.The results showed that the AM fungal network formed by intercropping maize had significant prevention and control effects on soil Phytophthora capsici pollution and the occurrence of pepper blight.Thirdly,in the field experiment of maize intercropping with different fertilizer rates and different distances,it showed that intercropping with maize significantly improve AM fungal consolidation rate up to 31%,and the treatments with same ridge width（Ridge width 1.2m）had higher rates than the treatment with same row width（Ridge width 1.65 m）up to 21%,and can significantly reduce the wilt severity 37%.It showed that the community structure of AM fungi not changed with the disease,so the field intercropping maize mainly by increasing mycorrhizal consolidation rate to play a role of disease suppression.Compared with the common ridge width treatment,the mycorrhizal consolidation rate of maize and pepper root system was further increased by 22%by increasing the amount of fertilizer applied(1.33 times of the normal fertilizer amount,the normal fertilizer amount was:720kg ha^-1 compound fertilizer,5730 kg ha^-1 organic fertilizer).Although it has no significant effect on the pepper epidemic index,it can be significantly improved 20%higher pepper yield.The results showed that the effects of AM fungi on Phytophthora capsici pollution and pepper disease prevention and control as well as yield increase could be better utilized in the treatment of ridge width intercropping with fertilizer.To sum up,soil P.capsica contamination is harmful to AM fungal diversity and the colonization activity,while intercropping with maize could prevent soil P.capsica contamination and pepper Phytophthora blight via forming mycorrhizal networks.Besides,the intercropping treatment with the same ridge width but higher fertilization is an efficiently potential measure to activate soil indigenous AM fungi to prevent P.capsica contamination infield practice.