AUTHOR=Yu Xuejian , Yang Jinshui , Wang Entao , Li Baozhen , Yuan Hongli 

TITLE=Effects of growth stage and fulvic acid on the diversity and dynamics of endophytic bacterial community in Stevia rebaudiana Bertoni leaves

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00867

DOI=10.3389/fmicb.2015.00867

ISSN=1664-302X

ABSTRACT=<p>The aim of this study was to learn the interactions among the endophytic bacteria, the plant growth, the foliar spray of fulvic acid, and the accumulation of steviol glycosides in the leaves of <italic>Stevia rebaudiana</italic>. Metagenomic DNA was extracted from the <italic>Stevia</italic> leaves at different growth stages with or without the fulvic acid treatment; and the diversity of endophytic bacteria in <italic>Stevia</italic> leaves was estimated by pyrosequencing of 16S rRNA genes. As results, Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were found to be the dominant phyla despite the growth stages and fulvic acid application. <italic>Stevia</italic> growth stages strongly regulated composition of endophytic community. The genera <italic>Agrobacterium</italic> (12.3%) and <italic>Erwinia</italic> (7.2%) dominated in seedling stage were apparently declined in the vegetable and initial flowering stages, while <italic>Sphingomonas</italic> and <italic>Methylobacterium</italic> increased in mature leaves at harvest time, which showed that the mature leaves of <italic>Stevia</italic> preferred to accumulate some certain endophytic bacteria. <italic>Sphingomonas</italic> and <italic>Methylobacterium</italic> constituted an important part of the core endophytic community and were positively correlated with the stevioside content and <italic>UGT74G1</italic> gene expression, respectively; while <italic>Erwinia, Agrobacterium</italic>, and <italic>Bacillus</italic> were negatively correlated with the stevioside accumulation. Fulvic acid treatment accelerated the variation of endophytes along the growth stages and increased the steviol glycosides content. This is the first study to reveal the community composition of endophytic bacteria in the <italic>Stevia</italic> leaves, to evidence the strong effects of growth stage and fulvic acid application on the endophytes of <italic>Stevia</italic>, and to demonstrate the correlation between the endophytic bacteria and the steviol glycosides accumulation.</p>