Effects Of Salicylic Acid,space Mutation And Epichlo? Endophyte On Stress Resistance Of Lolium Perenne

Perennial ryegrass（Lolium perenne）is an excellent forage and turfgrass.The endophytic fungus of grasses forms a symbiosis with the host.In order to improve the resistance of L.perenne,our present study intended to carry out research from the selection of reasonable management measures and the selection of resistant plants.Using L.perenne infected by endophytic fungus（E+）and non-endophytic fungi（E-）as material,firstly,the drought resistance of perennial ryegrass E+and E-plants after treatment with different concentrations of salicylic acid in greenhouse conditions to determine whether spraying the appropriate concentration of hormones can improve plant stress resistance.After space mutation of some perennial ryegrass E+and E-seeds,based on field phenotypic traits,preliminary selection of excellent mutant single plants and evaluation of stress resistance were carried out to select germplasm resources with strong stress resistance for selection.To lay the foundation for breeding new drought-resistant perennial ryegrass varieties suitable for arid regions in the northwest.The main results were:（1）Four different concentrations of salicylic acid（0 mmol/L,0.25 mmol/L,0.5 mmol/L and0.75 mmol/L）were used to treat perennial ryegrass E+and E-plants,respectively,and then treated with normal water（control）and no water（drought）for 15 days.It was found that the relative water content,chlorophyll content,peroxidase activity,superoxide dismutase activity and other physiological indexes of some E+and E-plants increased first and then decreased with the concentration of salicylic acid under the control and drought conditions,which indicated that salicylic acid had an impact on the physiological and biochemical characteristics of the host,and the effects of different concentrations were not the same;When there was no salicylic acid treatment,the Endophytic fungi significantly increased the relative water content,chlorophyll content,peroxidase activity and soluble sugar content of the host leaves under drought stress（P<0.05）,indicating that the endophytic fungi improved the drought resistance of the host perennial ryegrass under drought stress.when spraying a certain concentration of salicylic acid,Endophytic fungi only significantly（P<0.05）reduced the MDA content and increased the peroxidase activity of the plants,which indicated that the interaction of salicylic acid and endophytic fungi on the host plants was not significant under drought conditions.（2）E+and E-seeds of L.perenne were subjected to space mutation to observe their field phenotypic characteristics.The results indicated that the germination rate and the survival number of adult plants after germination of the mutant E+seeds were higher than those of the unmutated E+seeds,and the survival rate of the mutant E-plants was greater than that of the non-mutated E-plants.And in the second year after planting,the coefficients of variation of the plant height and tiller of the mutagenized E+plants were larger than those of the unmutated E+plants;the coefficients of variation of the tiller and crown width of the mutagenized E-plants were larger than those of the unmutated E-plants;the number of spikelets and spike length of the mutant E-plants were larger than their control.21 strains of E+and 18 strains of E-excellent variation were screened out.（3）The seeds of the excellent mutant plants were collected and treated with drought（15%of saturated soil water content）,salt（250mmol NaCl solution）,drought and salt（250mmol NaCl solution was poured first,and drought was carried out three days later）in greenhouse,the plants without any NaCl and being watered were used as control.The results showed that the three treatments inhibited the growth of perennial ryegrass significantly（P<0.05）.The plant height,tiller and biomass of some plants were decreased significantly（P<0.05）.The contents of Indoleacetic acid（IAA）,Cytokinin（CTK）,Salicylic acid（SA）,Gibberellic acid（GA）,C,P,K⁺,Ca²⁺in some perennial ryegrass plants were decreased significantly（P<0.05）.The content of Na⁺and Abscisic acid（ABA）in some plants were increased.Under the control and three stress treatments,endophytic fungi and air mutation had significant effects on plant growth,such as drought and salt treatment,endophytic fungi were significant（P<0.05）.The plant height,tiller and aboveground biomass were increased.The space mutation was significant（P<0.05）.The plant height and tiller of E+perennial ryegrass were increased.Endophytic fungi and aerial mutagenesis also had significant effects on the contents of endogenous hormones,nutrients and ions.For example,under the control and three kinds of stress treatments,endophytic fungi were significant（P<0.05）.The content of IAA,N and Ca²⁺were increased significantly（P<0.05）;CTK,Na⁺and K⁺content of the above ground part of the mutant were decreased significantly（P<0.05）.The content of ABA and underground P in non mutagenic plants were increased significantly（P<0.05）.The CTK and underground parts of non mutagenic plants were reduced Na⁺content.Under the control and three stress treatments,the IAA and N contents of E+plants were significant（P<0.05）.The Na+content increased significantly（P<0.05）.The content of IAA and Ca²⁺in the underground part of E-plant were significant（P<0.05）.The content of Na⁺in the underground part decreased significantly（P<0.05）.The results showed that endophytic fungi promoted the rational distribution of endogenous hormones,ion content and nutrient elements in the host plant,while the endogenous hormones,ion content and nutrient elements in the plant mutated by space flight were also affected,so as to promote the growth of the host plant and ultimately improve the drought and salt tolerance of the host plant.The resistance of the mutant plants screened by space mutation was enhanced,and the endophytic fungi further enhanced this advantage,which laid the foundation for the next step of breeding new varieties of drought resistant of perennial ryegrass,while the effect of salicylic acid on the Endophyte Symbiont plants of ryegrass was not obvious.Therefore,it is of great significance to develop high quality and stress resistant ryegrass Endophyte Symbiont breeding by"space mutation+endophyte".