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The impact of tissue type, growth stage and fertilizers on the community structure of cultured bacterial wheat endophytes in the Broadbalk experiment
R. R. ROBINSON (1), B. A. Fraaije (1), I. M. Clark (1), R. W. Jackson (2), P. R. Hirsch (1), T. H. Mauchline (1). (1) Rothamsted Research, Harpenden, United Kingdom; (2) University of Reading, Reading, United Kingdom

Endophytes play an important role in plant growth promotion, bio-fertilization and pathogen control. We investigated the effects of tissue type, growth stage and soil fertilizers on the bacterial endophyte community of winter wheat (<i>Triticum aestivum cv </i>Hereward). Culturable endophytes were isolated from roots and leaves across six fertilizer treatments, at two developmental stages, GS 37 and 83. In total 804 strains were grouped into 29 operational taxonomic units using RFLP. Endophyte abundance was higher in roots than leaves and tissue type affected relative phylum abundance (p < 0.05). Proteobacteria dominated in the roots whereas Firmicutes and Actinobacteria dominated in the leaves. Growth stage was found to affect the endophyte community structure at the genus level. Higher abundance of endophytes was found in the treatment without fertilizer, a trend not found for soil bacterial abundances. Fertilizer treatment had no effect on phylum distribution in the roots but there were distinctions at the genus level. In the roots at GS 37 <i>Plantibacter</i> and <i>Curtobacterium</i> were linked with treatment 144 kg N ha-1 yr-1, whereas <i>Arthrobacter</i> and <i>Agromyces</i> showed strong associations with treatment 288 kg N ha-1 yr-1. These distinctions between treatments for the endophytic community did not reflect those observed in the underlying soil bacterial community, indicating that plant growth stage is a main driver of endophytic bacterial community structure in wheat.

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