Speakers
Occurrence of Bacillus amyloliquefaciens as a Systemic Endophyte of Vanilla Orchids
James F. White, Jr.
Department of Plant Biology and Pathology,
Rutgers University,
New Brunswick, New Jersey, USA.
We report the occurrence of Bacillus amyloliquefaciens in vanilla orchids (Vanilla phaeantha) and cultivated hybrid vanilla (V. planifolia x V. pompona) as a systemic bacterial endophyte. We determined with light microscopy and isolations into culture 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. We demonstrated that B. amyloliquefaciens produced fungal inhibitors in culture. Whether the symbiosis between this bacterium and its vanilla hosts can be managed to protect vanilla crops from diseases is a question that should be evaluated in future research.
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James F. White, Jr., is Professor of Plant Pathology. Dr. White obtained the M.S. in Mycology and Plant Pathology from Auburn University, Alabama, and the Ph.D. in Mycology from the University of Texas, Austin in 1987. Dr. White specializes in symbiosis research, particularly endophytic microbes. He is the author of more than 180 articles, and author and editor of reference books on the biology, taxonomy, and phylogeny of fungal endophytes, including Biotechnology of Acremonium Endophytes of Grasses (1994), Microbial Endophytes (2000), The Clavicipitalean Fungi (2004), The Fungal Community: Its Organization and Role in the Ecosystem (2005), and Defensive Mutualism in Microbial Symbiosis (2009). He and students in his lab are exploring diversity of endophytic microbes and the various impacts that they have on host plants.