Interactions Of Ryegrass,Neotyphodium Lolii And Several Plant Pathogenic Fungi

Interactions of perennial ryegrass (Lolium perenne), endophytes(Neotyphodiumlolii)and plant fungal pathogens is a research area with great impacts in both theoryand production. However, the area is less studied than other areas of endophyteresearch world wide. Therefore, a series of experiments were carried out in laboratory,glasshouse and field to compare the responses of endophyte infected plants (E+) andendophyte free plants (E-) of perennial ryegrass varieties to 10 fungal pathogensisolated from turf type ryegrass in Lanzhou. The pathogens used in the experimentswere Alternaria alternata,Bipolaris sorokiniana,Fusarium avenaceum,Curvularialunata,Ascochyta leptospora,Fusarium acuminatum,Fusarium chlamydosporum,Fusarium oxysporum,Fusarium solani and Gliocladium roseum. In addition, someprotective enzymes activity and alkaloids contents of E+ and E- plants were measuredand LpsA gene of the common strain - Lp19 and mutant strain -AR1 of Neotyphodiumlolii were sequenced to identify their gene difference. Hopefully, the researh findingscould provide a solid base for understanding molecular gene interaction betweenNeotyphodium lolii and perennial ryegrass under disease stress environments. Themain results are summarized as follows:1,The endophytes infection rates in commercial turf type perennial ryegrassvarieties were 0% to 78% in Lanzhou City. Higher viability of endophytes ingerminated seedlings were detected with the infection rates of 7% to 52%.Alternaria. alternata and Bipolaris sorokiniana are identified as the mainpathogens of perennial ryegrass locally.2,Ten pathogens were inoculated on detached leaves of E+ and E- plants ofperennial ryegrass for both cultivar Pinnacle and wild type which collected fromfield. All of the inoculated pathogens were able to cause lesions on detachedleaves regardless of endophyte status. Compared with E- leaves, the lesion numberof E+ leaves decreased by 13% to 89% and the lesion length of E+ leavesdecreased by 23.6% to 87.9% for inoculation with Alternaria alternata,Bipolaris sorokiniana, Fusarium avenaceum, Fusarium solani and Gliocladiumroseum. The spore concentrations developed on E+ leaves were only 2.8% to81.3% of E- leaves. The responses of symbiosis of Neotyphodium lolii andperennial ryegrass are changed with the genotypes of hosts and pathogens.3,The intact plants of both cultivar Pinnacle and wild type which collected from field were inoculated with Alternaria alternata, Bipolaris sorokiniana,Curvularia lunata and Fusarium avenaceum. Compared with E- plants ofPinnacle, the infected rate of E+ plants decreased by 44.8%-73.7% and the lesionlength of E+ plants decreased by 47.6%-88.9%; Compared with E- plants of wildtype, only the infected rate of E+ plants which inoculated with Curvularia lunataand Fusarium avenaceum decreased by 58.2% and 82.8%, respectively and onlythe lesion length of E+ plants which inoculated with Fusarium avenaceumdecreased by 40.6%. Compared with E- plants of Pinnacle, the growth rate, freshand dry weights of E+ plants increased by 5%—130%. While, compared with E-plants of wild type, only fresh and dry weights of E+ plants increased by 71%—239%. Compared with E- plants, the activities of superoxide dismutase (SOD) ofE+ plants for both cultivar Pinnacle and wild type increased by 44%—164%.While, compared with E- plants, the activities of peroxidase(POD)of E+ plantswhich inoculated with Alternaria alternata, Bipolaris sorokiniana and Fusariumavenaceum increased by 110%—363%.4,The intact plants of cultivar Pinnacle were inoculated with Alternaria alternataand Bipolaris sorokiniana and the activities of polyphenol oxidase(PPO),phenylalanine ammonialyase(PAL), alkaloids content and the effects of leavesextraction on spore germination were recorded with the development of disease.Compared with E- plants, the infected rates of E+ plants decreased by 31.6% and35.3% respectively and the lesion length decreased by 37.7% and 23.8%respectively. The enzyme activities of PPO and PAL for both E+ and E- plantsincreased with disease development and then decreased. Compared with E- plants,enzyme activities of E+ plants increased by 75% to 140%. While, the alkaloidscontents did not change with disease development. Compared with E- plants, thespore germination rate of Alternaria alternata and Bipolaris sorokiniana treatedwith the ethanol extraction of E+ leaves decreased by 2%-16% and 10%-19%,respectively.5,The LpsA gene from the ergovaline biosynthetic pathway of Neotyphodium lolii inAR1 and Lp19 were cloned and sequenced. The results showed that their sequencewere the same except for three base pairs which were different with genebanksequence AF368420 showed the conserved nature of the LpsA gene among theisolated of Neotyphodium lolii.