Analysis Of The Relationship Between AMF Community And Resistance To Corn Sheath Blight In Typical Karst Regions

Sheath Blight is a devastating soil-borne fungi disease that is widespread and difficult to control.The pathogen is Rhizoctonia solani.The traditional methods of using chemical pesticides seriously affect the sustainability of the soil environment,and it is urgent to develop ecologically friendly biological control methods.Many studies have shown that the application of Arbuscular Mycorrhizal Fungi(AMF)to biological control has great potential,but the relationship between AMF and sheath blight in corn field has not been reported.In this study,maize sheath blight and AMF in Guangxi karst area were used as research objects,and field investigations(maize incidence and disease index)and indoor analysis(AMF community composition,mycorrhizal infestation index,leaf defense enzyme activity)were carried out in three growth stages of maize(seedling stage,tasseling stage,and filling stage).To exploring the distribution pattern of rhizosphere AMF in karst maize farmland and crop metabolic response of AMF against fungal diseases;analysis the relationship between incidence and disease index,AMF root infection,and the host plant defense enzyme activity under the actual farmland environment.In order to provide a theoretical basis for the prevention and control of corn sheath blight by AMF in karst area.The main results are as follows:The incidence of sheath blight in karst corn farmland is high.The incidence rate is between 50% and 85%,and the disease index range is 14-36.There is no significant correlation between the incidence rate and the disease index.The composition and abundance of AMF community in farmland soils in karst area were significantly different in growth stages of maize.Glomus is the dominant species of soil AMF,followed by Claroideoglomus,which showed significant differences between the seedling stage,the tasseling stage and the filling stage.The AMF abundance of farmland is high and the relative abundance of some dominant species is significantly different at each growth stage:one species during seedling stage and tasseling stage(OTU36,Glomus Glo5 VTX00069);two species during seedling and grain filling(OTU36;OTU32,Glomus Alguacil12 a Glo G15 VTX00063);and one species during tasseling and grouting(OTU51,Glomus sp.VTX00092).AMF diversity is most abundant in maize seedlings(R=58.8±2.17),there was a significant difference between the seedling stage and the filling stage(P=0.001),and the tasseling stage and the filling stage(P=0.002).During the growth of the corn,The activities of phenylalanine ammonialyase(PAL),peroxidase(POD),Chitinase and ?-1,3-glucanase in the growth of maize showed an increasing trend,which was significantly higher than that during the filling stage,or the tasseling stage was significantly higher than the seedling stage,or the tasseling stage and the filling stage were significantly higher than the seedling stage.Under the influence of competition position,the mycorrhizal infestation intensity and relative mycorrhizal intensity showed a decreasing trend with the growth cycle of maize,but there was a negative correlation between the mycorrhizal infection level and the corn sheath blight disease index in each plot during the filling stage,but there was a negative correlation between the level of mycorrhizal infection and the disease index of corn sheath blight during the filling stage,that means,the higher the mycorrhizal infection level,the lower the disease index of the field sheath blight.In addition,RDA analysis showed that Glomus was positively correlated with the activities of four defense enzymes.In the dominant species,Claroideoglomus ORVIN GLO4 VTX00278 significantly negatively affected the expression of four defense enzyme activities(P=0.03).There is no significant difference in AMF diversity between karst health and susceptible corn plots,but AMF community composition and structure were significantly different.At the genus level,Glomus and Archaeospora are more closely arranged with the healthy plot.At the dominant species level,Claroideoglomus ORVIN GLO4 VTX00278 and Glomus sp.VTX00222,Glomus sp.VTX00125,Glomus MO-G44 VTX00410 are associated with susceptible areas,while Glomus sp.VTX00067,Glomus sp.VTX00092,Glomus Kluber12 OTU18 VTX00310 are more relevant to healthy plots.In conclusion,it is feasible to construct a rich AMF community in maize rhizosphere soil to control corn sheath blight in karst area,but revealing the relationship between AMF and soil pathogens and rhizosphere microorganisms should be the focus of future research.