Inoculation of Barley (Hordeum vulgare) with the Endophyte Epichloë bromicola Affects Plant Growth, and the Microbial Community in Roots and Rhizosphere Soil.

Zhenjiang Chen,Taixiang Chen,James F White,Kamran Malik,Zhengfeng Wang,Chunjie Li,Jing Liu

doi:10.3390/jof8020172

Abstract

Hordeum vulgare is an important source of feed and forage for livestock, and of food and drink for humans, but its utilization rate is lower than that of other cereal crops, thus it is crucial to improve barley agronomic traits and production. Epichloë bromicola is an endophyte that was isolated from wild barley (Hordeum brevisubulatum). Previous studies have found that Epichloë can indirectly influence the growth of host plants by affecting soil chemical characteristics, the microbial community, and by producing a range of secondary metabolites. However, underlying effects of Epichloë on the abundance and diversity of soil and root microbes have not been well-studied. In addition, there is a question regarding the relationship between endophyte-produced alkaloids and effects on the root and rhizosphere microbial communities. The objective of this study was to investigate changes in agronomic traits, nutritional properties, peramine, soil chemical and microbial community in the fourth generation of new barley symbionts EI (E. bromicola-infection) and EF (E. bromicola-free) in LQ+4 and LZ+4. We understand the plant height and biomass of EI in LZ+4 were significantly higher than those of EF. The HPLC analysis showed that the peramine content of EI in LQ+4 and LZ+4 was 0.085 and 0.1 mg/g, respectively. We compared the bacterial and fungal communities by analyzing the 16s rRNA (for bacteria) and ITS rDNA regions (for fungi). Our data revealed that the composition of fungal communities in rhizosphere soil of LZ+4 EI are higher than EF. In addition, the diversity and richness of fungal communities in root and rhizosphere soil of LQ+4 EI and LZ+4 EI are significantly higher than EF. Rhizosphere soil microbial community composition was higher than that in roots in LQ+4 and LZ+4. Peramine was significantly and positively correlated with the richness of the soil fungal community. Moreover, the principal component analysis (PCoA) results indicated that E. bromicola significantly influenced the community composition of root and rhizosphere soil microbes in both LQ+4 and LZ+4. Our results illustrate that E. bromicola can influence barley growth, peramine production and microbial communities associated with barley.

Highlights

Epichloë are common and diverse microorganisms which systemically colonize the intercellular spaces of leaf primordia, leaf sheaths and blades of tillers, and the inflorescence tissues of reproductive tillers [1]
The endophyte-infection of tall fescue increased the operational taxonomic units (OTUs) of beneficial bacteria Proteobacteria and Acidobacteria [10], but it decreased the abundances of Gram-positive bacteria, arbuscular mycorrhizae [11], or showed no change in the community composition [12]
The present study showed that the diversity and richness of the rhizosphere soil fungal and bacterial communities are significantly higher than those within the root-associated fungal and bacterial community, as observed by other studies which showed that the diversity and richness of the rhizosphere soil AM fungal community are significantly higher than those within the root-associated AM fungal community in Achnatherum inebrians [66], grassland [70] and maize [71]

Summary

Introduction

Epichloë are common and diverse microorganisms which systemically colonize the intercellular spaces of leaf primordia, leaf sheaths and blades of tillers, and the inflorescence tissues of reproductive tillers [1]. Host plants inhabited by Epichloë are unique models for studying the potential relationship between aboveground and underground microbial communities [10]. Other studies report that endophyte-infection of tall fescue have lower soil microbial activity [13]. Epichloë may provide a competitive advantage for hosts by affecting soil microbial processes and soil microbial communities [14]. Some studies showed that alkaloids, as secondary metabolites of the host, may affect the host microbial community [17,18], other researchers oppose this view [19,20]. There are few studies that evaluate whether peramine produced by Epichloë may affect the microbial communities in roots or soils

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