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Occurrence of B acillus amyloliquefaciens as a systemic endophyte of vanilla orchids
Author(s) -
White James F.,
Torres Mónica S.,
Sullivan Raymond F.,
Jabbour Rabih E.,
Chen Qiang,
Tadych Mariusz,
Irizarry Ivelisse,
Bergen Marshall S.,
HavkinFrenkel Daphna,
Belanger Faith C.
Publication year - 2014
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.22410
Subject(s) - endophyte , bacillus amyloliquefaciens , biology , shoot , botany , symbiosis , seedling , bacteria , genetics
We report the occurrence of Bacillus amyloliquefaciens in vanilla orchids ( Vanilla phaeantha ) and cultivated hybrid vanilla ( V. planifolia × V. pompona ) as a systemic bacterial endophyte. We determined with light microscopy and isolations that tissues of V. phaeantha and the cultivated hybrid were infected by a bacterial endophyte and that shoot meristems and stomatal areas of stems and leaves were densely colonized. We identified the endophyte as B. amyloliquefaciens using DNA sequence data. Since additional endophyte‐free plants and seed of this orchid were not available, additional studies were performed on surrogate hosts Amaranthus caudatus , Ipomoea tricolor , and I. purpurea . Plants of A. caudatus inoculated with B. amyloliquefaciens demonstrated intracellular colonization of guard cells and other epidermal cells, confirming the pattern observed in the orchids. Isolations and histological studies suggest that the bacterium may penetrate deeply into developing plant tissues in shoot meristems, forming endospores in maturing tissues. B. amyloliquefaciens produced fungal inhibitors in culture. In controlled experiments using morning glory seedlings we showed that the bacterium promoted seedling growth and reduced seedling necrosis due to pathogens. We detected the gene for phosphopantetheinyl transferase ( sfp ), an enzyme in the pathway for production of antifungal lipopeptides, and purified the lipopeptide “surfactin” from cultures of the bacterium. We hypothesize that B. amyloliquefaciens is a robust endophyte and defensive mutualist of vanilla orchids. Whether the symbiosis between this bacterium and its hosts can be managed to protect vanilla crops from diseases is a question that should be evaluated in future research. Microsc. Res. Tech. 77:874–885, 2014 . © 2014 Wiley Periodicals, Inc.