Epichlo(?) Bromicola Effects Of Endophytic Fungi On Growth And Ion Balance Of Hordeum Bogdanii Under Alkaline Stress

The use of fungi for salinization improvement can increase the absorption of mineral nutrients by plants,improve the salt tolerance of plants,and promote plant growth.This study used Hordeum bogdanii as the experimental material to establish populations of H.bogdanii(E+)with endophytic fungi and H.bogdanii(E-)without endophytic fungi.To study the colony morphology and growth characteristics of Epichloe bromicola endophytic fungi under mixed alkali concentrations of 50 mmol/L and 100 mmol/L(Na2CO3:NaHCO3=1:1),as well as the effects of endophytic fungi under alkali stress on the tissue structure,ion balance,the expression of the Na+/H+antiporters gene NHX1,and the activity of the vacuolar membrane H+-ATPase enzyme in host H.bogdanii,To explore the mechanism of tissue structure and ion balance of endophytic fungi in alkaline tolerance of host H.bogdanii,and to provide technical support and theoretical basis for better utilization of endophytic fungi in saline land improvement.The main results are as follows:1.Under the conditions of PDA culture medium with different alkali concentrations,the growth rate of endophytic fungi continuously decreases with the increase of alkali concentration,and inhibits the growth metabolism of endophytic fungi,mainly manifested by the absence of yellow secretion.After alkali stress treatment,the length of the conidia and stem of endophytic fungi decreases with the increase of alkali concentration.2.Effects of endophytic fungi on the microstructure of host barley under alkali stress.Endophytic fungi slowed down the shrinkage and rupture of root epidermis of host H.bogdanii,and increased the area of root vascular bundle,vessel diameter,epidermal thickness and endodermis thickness.Under alkaline stress,the invasion of endophytic fungi increased the diameter of the air cavity and the thickness of the epidermis in the stem of H.bogdanii.Alkali stress reduced the vascular bundle area and vessel diameter of leaves,increased the area of vesicular cells,and increased the vascular bundle area,vessel diameter,and vesicular cell area of E+plants under the same treatment conditions.This indicates that the infection of endophytic fungi promotes the absorption of water and inorganic salts by the host H.bogdanii under alkaline stress,increases cell protection,reduces water loss,and improves plant aeration.3.Endophytic fungi increased the tiller number,plant height,biomass of host plants,and increased the absorption of K+and Na+ by host plants.When there is no alkali stress,endophytic fungi reduce the Clcontent in the host H.bogdanii,and E+ is significantly lower than E-.Alkali stress reduced the SO42 content in the aboveground and root systems of H.bogdanii,but compared to E-,endophytic fungi increased the SO42-content in the host H.bogdanii.Endophytic fungi and alkali stress did not significantly affect the NO3-content in the roots of the plant,but significantly affected the NO3-content in the underground part of the plant.When treated with 100 mmol/L,the NO3-content of E+ was significantly higher than that of E-.Analysis shows that endophytic fungi can stabilize ion balance in host plants and alleviate damage caused by alkali stress by regulating the content of anions and cations in host H.bogdanii.4.The vacuolar membrane Na+/H+ reverse transporter gene(HbNHX1)was cloned from H.bogdanii using Nested PCR technology.The gene has a total length of 1708 bp,a CDS length of 1617 bp,and encodes 538 amino acids;The encoded protein has a molecular weight of 59.28 kD and an isoelectric point(PI)of 7.68;Predicting the conserved protein domain,it was found that the protein has 13 transmembrane structural regions;The similarity with the wild barley NHX1 gene(AB089197.1)is the highest,reaching 96.29%.Fluorescence quantitative PCR results showed that E.bromicola endophytic fungi up-regulated the expression of HbNHX1 gene in host barley under alkaline stress.By measuring the activity of vacuolar membrane H+-ATPase,it was found that the H+-ATPase activity of E+ H.bogdanii was higher than that of E-,indicating that endophytic fungi were involved in the regulation of vacuolar membrane H+-ATPase activity to enhance the Na+/H+exchange capacity in the vacuolar membrane.