Stroma-bearing endophyte and its potential horizontal transmission ability in Achnatherum sibiricum

Abstract

Stromata occasionally are observed in Achnatherum sibiricum distributed in northern China. However, endophyte species that form stromata on that host have not been studied. Here we identified the first Epichloë sp. endophyte in stroma-bearing A. sibiricum. Isolated colonies of this Epichloë sp. were smoother and more compact than previously described for Epichloë gansuensis and also had longer phialides and faster growth in culture. However, phylogenetic relationships based on intron sequences of genes encoding β-tubulin (tubB) and translation elongation factor 1-α (tefA) grouped all isolates from the stromata in a clade with a close relationship to E. gansuensis. We identified the new isolates as E. gansuensis. The analysis of the stromata revealed no perithecium or ascospores during morphological and paraffin section observation. Furthermore, the ability of conidia formed on stromata to germinate and initiate infection of new seedlings was tested. After 3 mo 20% endophyte-free seedlings became infected by E. gansuensis, whereas the control group showed no endophyte infection. The results indicated the potential of cultures from conidia to mediate horizontal transmission.

• Epichloë
• phylogenetic
• stroma
• tefA
• tubB

Acknowledgments

We thank Professor Christopher L. Schardl (Department of Plant Pathology, University of Kentucky) and the anonymous reviewers for their valuable comments and advice on this manuscript. We thank Sha Jiang, Nianxi Zhao and Guangshuang Shen (College of Life Sciences, Nankai University) for their help with the preparation of the paraffin sections. We thank Mariusz Tadych (Department of Plant Biology and Pathology, Rutgers University), Qiang Xie and Yanhui Wang (Department of Zoology and Developmental Biology, Nankai University, China) for their great help with the phylogenetic analyses. This research was financially supported by the National Natural Science Foundation ( 31270463) of China and Doctoral Program Foundation of Institutions of Higher Education ( 20130031110023) of China. We greatly appreciate the support of National Hulunber Grassland Ecosystem Observation and Research Station for their invaluable assistance on this experiment.