Plant and Soil

, Volume 322, Issue 1–2, pp 197–207 | Cite as

Characterization of bacterial endophytes of sweet potato plants

  • Zareen Khan
  • Sharon L. DotyEmail author
Regular Article


Endophytic bacteria associated with sweet potato plants (Ipomoea batatas (L.) Lam.) were isolated, identified and tested for their ability to fix nitrogen, produce indole acetic acid (IAA), and exhibit stress tolerance. Eleven different strains belonging to the genera, Enterobacter, Rahnella, Rhodanobacter, Pseudomonas, Stenotrophomonas, Xanthomonas and Phyllobacterium, were identified. Four strains were shown to produce IAA (a plant growth hormone) and one strain showed the ability to grow in nitrogen free medium and had the nitrogenase subunit gene, nifH. To determine if IAA production by the endophytes had any role in protecting the cells against adverse conditions, different stress tests were conducted. The IAA producer grew well in the presence of some antibiotics, UV and cold treatments but the response to pH, osmotic shock, thermal and oxidative treatments was the same for both the IAA producer and the no IAA producer. To determine if IAA produced by the strains was biologically relevant to plants, cuttings of poplar were inoculated with the highest IAA producing strain. The inoculated cuttings produced roots sooner and grew more rapidly than uninoculated cuttings. These studies indicate that endophytes of sweet potato plants are beneficial to plant growth.


Ipomoea batatas Sweet potato Plant-microbe interaction Indole acetic acid (IAA) Nitrogen fixation Stress Plant growth promotion 



We thank undergraduate student helper Amanda Thornton for helping with the isolation of endophytes and the United States Department of Agriculture (USDA) for funding this project (grant no: 58-3148-5159)


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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.College of Forest ResourcesUniversity of WashingtonSeattleUSA

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