Effects Of Phouphorus,Claroideoglomus Etunicatum And Grass Endophyte On Perennial Ryegrass Leaf Spot Disease Caused By Bipolaris Zeae

Arbuscular mycorrhizal(AM)fungi and grass endophyte(Epichlo?)are widely existed in grassland agro-ecosystem,and both of them can establish symbiotic relationships with Lolium perenne,promoting plant nutrient absorption,regulating plant growth and enhancing resistance to pathogen.Phosphorus is an essential element in plant growth and metabolism,which can affect plant growth and microbial action.In this study,three pot experiments were established in a greenhouse used perennial ryegrass seeds infected with grass endophyte(E+)and without grass endophyte(E-).1).To investigate the effects of arbuscular mycorrhizal fungi(Claroideoglomus etunicatum)and grass endophyte on the growth of perennial ryegrass under different phosphorus levels(0,10,20,30 mg/kg).Determining an optimal phosphorus level.2).Effects of inoculation and non-inoculation of AM fungi and grass endophyte on Bipolaris zeae in perennial ryegrass without phosphorus addition.3).On the basis of the above studies,investigating the effects of optimal phosphorus level on AM fungi-grass endophyte-Bipolaris zeae.In order to provide theoretical support for the efficient use of symbiotic microorganisms,promoting grass growth and improving grass disease resistance.The main results were as follows:(1)Under four phouphorus levels,the total biomass,nutrient content,net photosynthetic rate,transpiration rate,stomatal conductance and phosphatase activity of perennial ryegrass with 20 mg/kg(P20)treatment were better than that of other phosphorus levels.The inhibitory effect of AM fungi on plant growth was relieved by phosphorus addition.Grass endophyte increased biomass and nutrient contents of perennial ryegrass and had interactions with AM fungi,inhibiting the infection of AM fungi.(2)The pathogen could infect perennial ryegrass effectively,forming typical leaf spot symptoms and reducing plant biomass.AM fungi and grass endophyte increased the activities of?-1,3-glucan,PAL,chitin,FA and lignin,alleviating the negative effects of pathogen on plant growth,and decreasing the incidence of leaf spots by 6.27%-57.46%.The AM colonization wasnot significantly affected by pathogen(P>0.05).The influence of grass endophyte on the AM colonization varied with different treatment conditions.Grass endophyte inhibited the infection of AM fungi and AM colonization decreased by 28.27% without inoculation of pathogen.While the AM colonization increased by 85.21% when combined with pathogen.It showed that in the presence of pathogen,grass endophyte changed its interaction strategy with AM fungi,that is,to resist the infection of pathogen preferentially.(3)Phosphorus changed plant-microorganism and microorganism-microorganism interactions.However,there was no significant effect on the incidence of perennial ryegrass and the activities of PAL,chitin,JA and lignin(P>0.05).Compared without phosphorus addition(P0),P20 decreased the inhibitory effects of AM fungi on the growth of perennial ryegrass and the promoting effects of grass endophyte.Grass endophyte reduced AM colonization by 8.41% in the absence of pathogen under P0,while increased 8.57% when inoculated with pathogen.The AM colonization of P20 level was opposite to P0.The results showed that phosphorus addition changed the interaction strategy of grass endophyte-pathogen-AM fungi also.