Effects of Combined Inoculation of Endophytic Fungi on the Growth and Nutrient Content of Tripterygium wilfordii

To investigate the effects of combined inoculation of endophytic fungi on the growth and nutrient content of host plants, four strains of endophytic fungi, Penicillium steckii NS6, Meyerozyma guilliermondii NS31, Hypocrea nigricans NS32 and Fusarium oxysporum NS33, were paired and inoculated into micropropagated Tripterygium wilfordii seedlings. Sterile PDA medium plugs were served as controls. The growth, chlorophyll content and nutrient content (C, N, P and K) of the micropropagated seedlings were measured. The results indicated that combined inoculation of endophytic fungi significantly enhanced the height of micropropagated seedlings. Specially, the height under NS6 + NS33 and NS6 + NS32 inoculation was 2.72 and 2.28 times greater than the control, respectively. Additionally, the root length and dry mass under NS6 + NS32 inoculation were significantly higher compared to the control. The dry mass under NS6 + NS33 inoculation was significantly higher compared to the control. The combined inoculation of NS6 + NS32 had synergistic effects on increasing the mass of the micropropagated seedlings, surpassing the effects of single inoculation. Furthermore, inoculation of NS6 + NS32 and NS6 + NS33 significantly elevated chlorophyll a, b, and a + b levels. The combined inoculation of each fungal strain increased the C and N content compared to the control. However, there was no significant effect on P and K levels. The influence of endophytic fungi on the growth and nutrient content of micropropagated T. wilfordii seedlings varied depending on the combination of fungal species. Notably, the combination of NS6 and NS32 strains exhibited enhanced growth promotion effects and showed potential for valuable applications.