Regulation of mineral elements in Hordeum brevisubulatum by Epichloë bromicola under Cd stress.

In this study, wild barley (Hordeum brevisubulatum) infected (E+) and uninfected (E-) by Epichloë bromicola were used for hydroponic experiments during the seedling stage. Various attributes, such as the effect of fungal endophyte on the growth and development of wild barley, the absorption of cadmium (Cd) and mineral elements (Ca, Mg, Fe, Mn, Cu, Zn), subcellular distribution, and chemical forms were investigated under CdCl₂ stress. The results showed that the fungal endophy significantly reduced the Ca content and percentage of plant roots under Cd stress. The Fe and Mn content of roots, the mineral element content of soluble fractions, and the stems in the pectin acid or protein-chelated state increased significantly in response to fungal endophy. Epichloë endophyte helped Cd²⁺ to enter into plants; and reduced the positive correlation of Ca-Fe and Ca-Mn in roots. In addition, it also decreased the correlation of soluble components Cd-Cu, Cd-Ca, Cd-Mg in roots, and the negative correlation between pectin acid or protein-chelated Cd in stems and mineral elements, to increase the absorbance of host for mineral elements. In conclusion, fungal endophy regulated the concentration and distribution of mineral elements, while storing more Cd²⁺ to resist the damage caused by Cd stress. The study could provide a ground for revealing the Cd tolerance mechanism of endophytic fungal symbionts.