Effects Of Interaction Between Jasmonic Acid And Endophytic Fungi On Wild Barley Under Salt Stress

Wild barley(Hordeum brevisubulatum)is a perennial quality fograse grass of Gramineae family.It is widely distributed in saline meadows in northern China,has tolerances of salt and alkali,drought,and strong adaptability to the environment.In this study,endophyte-infected(E+)and endophyte-free(E-)seeds and seedlings of wild barley were used for determining the germination index of E+ and E-barley seeds under salt stress after soaked in different concentrations of jasmonic acid(JA).To explore the effect of interaction between different concentrations of JA and endophytic fungi on seed germination under salt stress.Different concentrations of JA treatments were used,growth indexes,physiological and biochemical indexes,and content of alkaloid of wild barley were measured under salt stress.The purpose was to elucidate the interaction of JA and endophytic fungi on wild barley and provide scientific basis for exploring the mechanism how endophytic fungi increased the salt tolerance,and to breed salt-tolerant varietiy.The main findings of this study were as follows:1.Seed germination was conducted on filter paper,treated with different concentrations of JA(0 ?mol/L,0.01 ?mol/L,0.1 ?mol/L,1 ?mol/L,10 ?mol/L)under salt stress(0 and 200 mmol/L).It was found that the germination index,germination rate,root length,shoot length,and water content of seedling increased and then decreased with the increasing of JA concentration.The above indexes of E+ seeds were significantly higher than those of E-(P<0.05)under various concentrations of JA treatments.While the concentration of JA was 0.1 ?mol/L,germination index,germination rate,root length,shoot length and seedling water content of wild barley seeds were significantly higher than those of other treatments(P<0.05),which indicated that 0.1 ?mol/L was the most suitable JA concentration for seed germination of wild barley under salt stress.2.Seedling established in pot,it was found that it had a ?duality? effect on the growth of wild barley.Under salt stress(0,200 and 400 mmol/L)and JA treatment(0 ?mol/L,0.01 ?mol/L,0.1 ?mol/L,1 ?mol/L,10 ?mol/L),JA concentration of 0.01-1 ?mol/L showed a promoting effect,but inhibited in 10 ?mol/L.The interaction between a certain concentration of JA and endophytic fungi could significantly increase the plant height of wild barley(P<0.05),but had no significant effect on their tiller number(P>0.05).3.At the same conditions with above mentioned,it was found that 0.01-1 ?mol/L JA increased chlorophyll content,photosynthetic rate,transpiration rate,stomatal conductance,proline content,peroxidase activity and superoxide dismutase activity,but reduced malondialdehyde content compared with the controls.The interaction between a certain concentration of JA and endophytic fungi significantly increased photosynthetic rate,transpiration rate,stomatal conductance,peroxidase activity and superoxide dismutase activity(P<0.05).In addition,10 ?mol/L JA treatment could significantly reduce the total C content of E-barley under 400 mmol/L salt stress(P<0.05),however,there were no significant effects on total N and total P content of wild barley(P>0.05).4.Regarding the contents of alkaloids in symbiont of endophytic fungi and wild barley under treatmens of JA(0 ?mol/L,0.01 ?mol/L,0.1 ?mol/L,1 ?mol/L,10 ?mol/L)and salt stress(0,200 and 400 mmol/L),it was found that the interaction between JA and endophytic fungi could significantly increase the accumulation of peramine and lolitrem B in the symbiont(P<0.05),but had no significant effect on the accumulation of ergot alkaloids(P>0.05).The optimal JA concentration for peramine accumulation is 0.01 ?mol/L.