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Background and aims: Low nutrient soil is a major limiting factor for normal growth and high yield of plants. Epichloë endophyte infection has been shown to increase host growth, nutrient uptake and balance. This study was done to determine the impact of Epichloë endophyte on growth, survival and elemental nutrient content of perennial ryegrass (Lolium perenne) under low fertility conditions. Methods: endophyte-infected and endophyte-free plants of L. perenne were grown without fertilization in a greenhouse environment. Plant survival rate, dry weight of leaves and roots, root metabolic activity and nutrient element (C, N, P, Na, K, Ca, Mg, Cu, Fe, Zn, Mn) contents were determined after 0 d, 45 d, 90 d, 135 d and 180 d. Results: The presence of Epichloë endophyte relieved the withering and yellowing of plants in the short term (0 to 90 d). The possible mechanisms by which E. festucae var. lolii infection enhances survival of plants includes improved root growth and metabolic activity (i.e., cellular metabolism), increased biomass production, and increased concentration of many nutrient elements in leaves and roots. The endophyte had positive direct and indirect effects on plants in multiple ways, including: increased organic carbon, total nitrogen, total phosphorus and Mn content in leaves, increased K content in leaves and roots, and improved root growth and activity. Conclusions: The presence of endophyte E. festucae var. lolii played a key role in improving the survival of L. perenne plants by increasing root growth and metabolic activity, promoting plant biomass and altering nutrient content. [ABSTRACT FROM AUTHOR]

Background and aims: In many grasslands under grazing pressure, unpalatable plants have become abundant and these areas are refuges for plant diversity. We hypothesize that unpalatable plants may also serve as refuges for soil microbes. Methods: We tested this hypothesis by investigating soil fungal diversity and community composition, soil properties, and plant parameters in areas dominated by the unpalatable drunken horse grass (Achnatherum inebrians), and areas without this toxic grass, in three types of natural rangelands in northern China. Results: Our results showed that the areas dominated by A. inebrians had a higher fungal diversity, higher microbial biomass, higher abundance of plant pathogens in soil, and higher plant biomass than areas that did not contain A. inebrians. Soil fungal community composition was positively correlated with plant community composition across the three study sites. Fungal diversity and microbial biomass were positively correlated with higher plant biomass. Abundance of soil plant pathogens was positively correlated with coverage of A. inebrians. Conclusions: The results indicated that plant community composition significantly correlated with soil fungal community composition, and refuge effects of A. inebrians drive higher fungal diversity, microbial biomass and abundance of plant pathogens in the soil. Increased abundance of A. inebrians potentially has considerable effects on the soil fungal community in grasslands. [ABSTRACT FROM AUTHOR]

Colonization by foliar fungal endophytes can assist host plants in the acquisition of soil nutrients, however understanding of the effects of Epichloë endophytes on soil nutrient dynamics and their consequences for nitrogen cycling remains fragmentary. Here, we studied the microbial functional genes involved in the soil nitrogen cycle and soil nutrient dynamics along a nitrogen gradient in rhizosphere soil of ryegrass infected by the endophyte Epichloë festucae var. lolii. High-throughput sequencing was used to determine the community of microbial functional genes. Plant nutrients and soil N 2 O flux were measured. The endophyte presence reduced the plant nutrient traits (shoot organic carbon, total nitrogen and total phosphorus, and root total phosphorus) under low nitrogen, while it increased the soil nutrient accumulation and altered the microbial environment. Plants with fungal endophyte showed higher community diversity in the AOB -amoA gene (ammonia-oxidation bacteria), had lower absolute and relative abundances in the nirK gene (nitrite reduction bacteria), and improved relative abundances and community diversity of the nosZ (nitrous oxide reduction bacteria). The nifH gene (N 2 fixing bacteria) showed higher absolute and relative abundances, and diversity in rhizosphere soil of endophyte-infected plants. Changes in plant and soil traits mediated by endophyte infection were closely related to N 2 O fluxes and nifH gene abundance. The changes in CO 2 flux by changing in soil microbial biomass nitrogen mediated by shoot biomass (induced by endophyte infection), which further altered the soil pH and NO 3 − content and lead to an increased in NH 4 + accumulation. The current study demonstrated that the possible mechanism for endophyte-mediated nutrient uptake might promote the NH 4 + accumulation through nitrogen mineralization and NO 3 − isomerization rather than enhancing in the nitrogen fixation process and inhibiting the denitrification process in N limited samples. By underlining the importance of endophyte infection for nutrient accumulation in plant and soil and biomass, these findings suggested that nutrient availability could initiate endophyte infection effects to mitigate the damage of low N stress for the host. • Nutrient availability mitigates low N stress by initiating endophyte effects. • Increased in soil microbial biomass carbon and nitrogen by endophyte infection. • Endophyte-infected plant reduced nitrous oxide (N 2 O) flux and increased CO 2 flux. • Endophyte-mediated nutrient uptake associated with soil NO 3 − dissimilation. [ABSTRACT FROM AUTHOR]