Culture Characteristics And Resistance To Metal Ions Of Epichlo? Endophyte Of Festuca Sinensis

Festuca sinensis is perennial grasses of the genus Festuca,which has strong stress tolerance and high adaptability.Endophytic fungi is symbiotic with Festuca sinensis.In the present study,five Epichlo?endophyte strains?strain ID 1,2,41D,57D,111D?were isolated from different F.sinensis ecotypes.For these five strains,the antioxidant capacities and enzyme activities in PDB and the growth characteristics on medium with different additives and different heavy metals stress were measured.Meanwhile,in order to investigate endophyte effects on F.sinensis abiotic stress tolerance,the growth performance and physiology of Epichlo?infected?E+?and uninfected?E-?plants of two ecotypes F.sinensis under heavy metal conditions were also studied.The main results are as follows:?1?The total antioxidant capacity,the scavenging ability of superoxide anion radicals and hydroxyl radicals of five strains were significantly different?P<0.05?,and 111D fermentation extract was the strongest?P<0.05?.For all these five strains,the scavenging ability of superoxide anion radicals were higher than that of hydroxyl radicals?P<0.05?.These five strains have different enzyme activities.Strain 1 can produce all the tested four enzymes including protease,chitinase,cellulase and glucanase,and strain 2 and 41D can produce protease and chitinase,57D can produce chitinase and glucanase,and 111D only produces glucanase.?2?These five strains have significantly different growth rate?P<0.05?on all of the tested medium including control,addition of vitamins?VB₁,VB₅,VB₉?and plant growth regulators?IAA,GA₃,KT-30?.In most cases,the growth rates of strain 1 were the fastest?P<0.05?,and those of 57D were the slowest?P<0.05?.Except with the growth rates of 57D on VB₁ medium,the growth rates of these five strains significantly increased with the increase of the concentration of VB₁ and VB₅?P<0.05?.The growth rates of 1,41D,57D and 111D significantly increased with the increase of VB₉ concentration?P<0.05?,however,the growth rates of strain 2 had no significant changes.The growth rates of these five strains increased on the medium with IAA and GA₃,however,the promotion effects were inconsistent at different concentrations.The low concentration?5-10 mg/L?of KT-30 significantly promoted the growth of five strains,and the high concentration?20-40 mg/L?of KT-30 significantly inhibited the growth of five strains?P<0.05?.These results indicated that the appropriate concentration of additives could promote the growth of five strains in F.sinensis.?3?The metal ions of Na⁺,Cd²⁺,Zn²⁺and Cr⁶⁺all inhibited the growth of these five strains and the inhibition effects increased with the increase of concentration.Cd²⁺?25-200 mg/L?had the strongest inhibition effects,and Cd²⁺at 25 mg/L completely inhibited the growth of strain 2.Cd²⁺at 200 mg/L completely inhibited the growth of all strains except 111D?P<0.05?.Zn²⁺?250-750mg/L?and Na⁺?0.2-0.6 mmol/L?had the stronger inhibition effects,the growth rates of these five strains significantly decreased with the increase of concentration?P<0.05?.Cr⁶⁺?100-300 mg/L?had weak inhibition effects,and the growth rates of these five strains were significantly higher than those of these five strain with other ion treatments?P<0.05?.Under Na⁺stress,strain 41D grew fastest and had the strongest resistance?P<0.05?;under Cd²⁺,Zn²⁺and Cr⁶⁺stress,strain111D grew fastest and had the strongest resistance?P<0.05?.?4?Epichlo?had effects on plant growth including plant height,tiller and biomass,and physiology including the contents of heavy metal,endogenous hormones and alkaloids of two ecotypes of F.sinensis under the treatment with Cd²⁺?100 mg/L?and Zn²⁺?500 mg/L?.The Epichlo?significantly increased the plant height,tiller number and biomass accumulation of two ecotypes of F.sinensis under heavy metal treatment?P<0.05?.Epichlo?significantly reduced the accumulation of heavy metals in above parts whereas increased the accumulation in root of two ecotypes of F.sinensis?P<0.05?.Epichlo?significantly increased the content of growth hormones such as IAA and GA₃,whereas reduced ABA of two ecotypes of F.sinensis under heavy metal treatment?P<0.05?.Zn²⁺treatment had no significant effect on alkaloid contents of F.sinensis,however,Cd²⁺treatment only had significant effect on lolitrem B content?P<0.05?.These results indicated that Epichlo?can help host tolerant to stress by regulating the physiological and biochemical response of F.sinensis under heavy metal conditions.The growth of two ecotypes of F.sinensis were different.The height of ecotype 111 under control and heavy metal treatment was significantly higher than ecotype 41?P<0.05?.In summary,the present study analysis the physiological characteristics and the effects of different conditions on the growth of five endophyte strains isoloated from F.sinensis,and the optimal exogenous additives concentration were selected to promote the growth of endophytes and strains with strong metal ions tolerance were screened.Meanwhile,the greenhouse study suggested that Epichlo?improved the heavy metal tolerance of F.sinensis.These results laied a foundation for further screening high-quality germplasm resources of F.sinensis.