Biology, Physiology And Anti-fungal Activities Characteristics Of Neotyphodium Lolii Of Ryegrass

Perennial ryegrass(Lolium perenne),as an important forage and turf grass in China,plays an important role in grassland livestock production and landscape lawn establishment.It is well known that grass endophyte enhances biotic and abiotic stresses tolerance of the host plants.In this study,four perennial ryegrass varieties from the United States were used to determine the interactions of perennial ryegrass, endophyte and pathogenic fungi.The perennial ryegrass were Accent,Medary, Pinnacle and Fairway;The endophytic fungi was detected and separated from perennial ryegrasses;The four plant pathogens were Alternaria alternata,Bipolaris sorokiniana,Curvularia lunata and Drechslera sp.The growth of endophytic fungi on the five different medium,under five different pH,at the seven different temperatures, in the nine carbon levels and in the nine nitrogen levels were observed.Interaction between endophytic fungi and the pathogenic fungi were determined under in vitro incubation of perennial ryegrass,effect of secondary metabolites of endophytic fungi on the growth of four plant pathogenic fungi,and the effect of endophytic fungi on physiology of perennial ryegrass by inoculating of Bipolaris sorokiniana were also studied.The results were summarized as the follows:1.The endophytic fungi were detected from seeds of four perennial ryegrass varieties.The detected rate of Accent,Medary,Pinnacle and Fairway were 37.8%, 39.2%,51.2%and 52.6%,respectively.Four strains endophytic fungi included twenty endophytic fungi were isolated from E+ leaf sheath in the four perennial ryegrass varieties.All fungi belong to Neotyphodium according to their morphological character.N-ast,N-mdl,N-tp and N-qd were selected from each strains were used for the following experiments.2.The optimum growth conditions for N-ast,N-mdl,N-tp and N-qd were on the medium of oat agar,at the pH of 7～9 and at 25℃.Cellulase was the most easily used carbon by N-ast,N-mdl,N-tp and N-qd;Tryptone,casein peptone,proline and peptone were the most easily used nitrogen by N-ast,N-mdl,N-tp and N-qd.3.In the dual-culture test,the growth of the four pathogenic fungi were inhibited by endophytic fungi at different extent,of which N-ast and N-qd had stronger inhibit activity than others.The inhibition of N-ast to B.sorokiniana and C.lunata were 46.24%and 45.50%,respectively;The inhibition of N-qd to A.alternate, Drechslera sp.were 44.67%and 46.62%,respectively.4.Secondary metabolites of N-ast,N-mdl,N-tp and N-qd obviously inhibited the four pathogenic fungi colonies growth and spores germination,.N-qd had the strongest inhibit activity.The inhibition rate of N-qd on colonies growth of A. alternate,B.sorokiniana,C.lunata and Drechslera sp.were 17.79%,57.20%, 33.79%and 41.52%,respectively;The inhibition of N-qd on spores germination of the four pathogenic fungi were 78.82%,86.67%,85.54%and81.03% respectively.5.Neotyphodium reduced malonaldehyde content,however,enhanced free praline content,hydrogen peroxidase and phenylalnine ammonialyase activity of the perennial ryegrass when inoculated with B.sorokiniana.Malonaldehyde content of Pinnacle was 60%lower in E+ leaves than in E—leaves.Free praline content of Accent was 69%higher in E+ leaves than in E—leaves Hydrogen peroxidase activity of Pinnacle was 25%higher in E+leaves than in E—leaves Phenylalnine ammonialyase activity of Fariway in E+ leaves was 31%higher than in E—leaves.