The effects of Epichloë endophytes on the growth and competitiveness of Achnatherum sibiricum are mediated by soil microbe diversity

Abstract

Abstract Many grasses are infected by systemic fungal endophytes that occur in aboveground plant tissues. Both aboveground endophytic fungi and belowground soil microbes can influence plant growth, but studies on their simultaneous effects on plant growth and competitiveness are limited. This study aims to investigate whether the role of aboveground endophytic fungi in the growth and competitive ability of the host grasses was influenced by soil microbes. In this study, we used Epichloë endophyte-infected and endophyte-free Achnatherum sibiricum as plant materials. A wet sieving method was adopted to obtain microbial inocula with different diversities (com, combined microbe fraction, high diversity; sm, small microbe fraction, low diversity). A three-factor randomized block design was used. The first factor was the endophyte infection status of A. sibiricum. The second factor was the microbial composition of the soil inocula. The third factor was the planting type. Growth and competitive characters were measured after 16 weeks. The results showed that a soil microbe inoculation was detrimental to the growth of A. sibiricum. Epichloë endophytes significantly mitigated the inhibitory effect of soil microbes on A. sibiricum planted alone. When A. sibiricum was planted with Stipa grandis, there was a significant interaction between Epichloë endophytes and soil microbes on the interspecific competition of A. sibiricum. When inoculated with small microbial community fraction, Epichloë endophytes significantly improved the interspecific competitive ability of host plants. When inoculated with combined microbial community fraction, however, Epichloë endophytes had no significant effect on host competition. The results showed that the interaction between Epichloë endophytes and soil microbes contributed more to the interspecific competitive ability than either Epichloë endophytes or soil microbes alone.