Effects of Epichlo endophytes of Achnatherum sibiricum on spore germination of arbuscular mycorrhizal fungi.

Endophytic fungi and arbuscular mycorrhizal (AM) fungi are important components of grassland ecosystem. Endophytes can reduce colonization rates of their host plants by AM fungi. In this study, Achnatherum sibiricum, infected by Epichlo sibiricum (Es) or E. gansuensis (Eg), was adopted as experimental material. The effect of Epichlo endophyte culture filtrate, root exudates and aqueous extracts from the leaves (including fresh and dead leaves) on the spore germination rates of AM fungi (Glomus mosseae and Glomus etunicatum) were evaluated. The results showed that culture filtration of Epichlo endophyte significantly inhibited the germination rate of AM fungi spores. Root exudates of infected plants only significantly inhibited the germination of G. etunicatum spores, and such effect was not related to the endophytic species. The leaf aqueous extracts had no significant effect on the germination rate of G. mosseae spores. Only the aqueous extract of Es-infected dead leaves significantly reduced the spore germination rate of G. etunicatum. In natural ecosystem, Epichlo endophytes are normally internally hosted in plants, which may affect the spore germination of AM fungi by affecting the root exudates of the host plants.

[Effects of methyl jasmonate treatments and endophyte infection on growth of Achnatherum sibiricum].

We used Achnatherum sibiricum, a native grass as test material and application of methyl jasmonate (MJ) to simulate herbivory, and compared the growth and physiological characters of endophyte-infected (EI) and endophyte-free (EF) plants. The results showed that MJ treatment significantly decreased the shoot growth, but significantly increased the concentrations of defensive substances such as total phenolic and lignin, and decreased the size of aphid population. Endophyte infection significantly increased the tiller number, total phenolic and lignin contents in the shoot. As for shoot biomass and total phenolic in the root, they were affected by MJ treatment. Without MJ treatment, no significant differences were found in shoot biomass or root phenolic content whether the plants were infected by endophyte or not. With MJ treatment, the shoot biomass was significantly lower and the shoot phenolic content was significantly higher in EI plants than in EF plants. Endophyte infection significantly increased resistance of the host plant to aphids, and the beneficial effect was enhanced by MJ treatments, after three applications with MJ, there were no aphids on EI plants. Overall, endophyte infection could alter the allocation pattern of the host plant between growth and defense, and MJ treatments further strengthened the defensive ability of the host plant at the cost of growth.

Diversity and taxonomy of endophytes from Leymus chinensis in the Inner Mongolia steppe of China.

Epichloë species and their anamorphic relatives in genus Neotyphodium are fungal symbionts of grasses ubiquitously existing in temperate regions all over the world. To date, 13 Epichloë species and 22 Neotyphodium species have been formally described, based on morphological characters and phylogenetic analyses. Leymus chinensis (Poaceae) is a dominant grass native to the Inner Mongolia steppe of China. Previously, it was reported to harbor endophytes, but little was known about these endophytes. To investigate their diversity and taxonomy, 96 fungal isolates were obtained from three field populations of L. chinensis. The isolates were classified into three morphotypes based on morphological characters and phylogenetic analyses of sequences of genes for ß-tubulin (tubB), translation elongation factor 1-α (tefA), and actin (actG). The dominant morphotype, morphotype I, was identified as a choke disease endophyte, Epichloë bromicola. This broadened the host range and phylogenetic definition of E. bromicola.

Taxonomy, diversity and origins of symbiotic endophytes of Achnatherum sibiricum in the Inner Mongolia Steppe of China.

We sampled five Achnatherum sibiricum populations and documented the distribution and abundance of endophytes. In total, 438 fungal isolates were obtained. They were classified into 11 morphotypes based on growth rate and morphological characters including colonial morphology, the production of conidiogenous cells, conidial size and dimension on potato dextrose agar medium. Both tub2 and actG sequences identified only a single product in all representative isolates from three dominant morphotypes. All sequences fell in the same main clade, including Neotyphodium gansuense and Neotyphodium gansuense var. inebrians from another Achnatherum species in North China, Achnatherum inebrians, and Neotyphodium guerinii from European grasses Melica ciliate and Melica transsilvanica. Based on both morphological and phylogenetic analyses, isolates in morphotype I were described as representing a novel Neotyphodium species, Neotyphodium sibiricum sp. nov. Isolates in both morphotype II and III were identified as representing N. gansuense. Both tub2 and actG sequences suggested that N. sibiricum and N. guerinii were probably derived from a common Epichloë ancestor.

Influence of nitrogen fertilizer and endophyte infection on ecophysiological parameters and mineral element content of perennial ryegrass.

An experiment was designed to determine the effect of the fungal endophyte Neotyphodium lolii on the growth, physiological parameters and mineral element content of perennial ryegrass (Lolium perennel L.), when growing at two N supply levels. Endophyte infection had a significant positive effect on both shoot and root growth of ryegrass, but this difference was only significant in the high N supply treatment. At high N supply, endophyte-infected (EI) plants accumulated more soluble sugar in the sheath and the root than endophyte-free (EF) plants. Endophyte infection affected mineral element concentrations in the root more than in the shoot. We found a significant effect of endophyte infection on B, Mn and Mg in the root, but significant effect was only found on B in the shoot. EI plants tended to accumulate less B in the shoot at both N levels, but accumulated more B, Mn and Mg in the root at low N levels. The difference of growth parameters in different periods was significant. The content of soluble sugar and crude protein in the sheath were also dependent on the growth stages of both EI and EF plants.

Genetic diversity and population differentiation of the dominant species Stipa krylovii in the Inner Mongolia Steppe.

Random amplified polymorphic DNA was used to assess the level of genetic diversity and genetic structure of Stipa krylovii (Gramineae), an important dominant species in the northern grasslands of China. Genetic diversity was low within S. krylovii populations, and diversity at the population level was associated with precipitation and cumulative temperature variations. There was much genetic differentiation among populations and among habitats as well. A Mantel test indicated no significant correlation between genetic distance and geographic distance of populations. A nonmetric multidimensional scaling analysis revealed some spatial relationships among the 90 individuals in a two-dimensional plot. Habitat fragmentation and degradation throughout the geographic range of S. krylovii could account for the low genetic diversity and high genetic differentiation of the species. Such information will be useful for conservation managers trying to plan an effective strategy to protect this important species.