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Nitrogen Fixation in Wheat Provided by Klebsiella pneumoniae 342

October 2004 , Volume 17 , Number  10
Pages  1,078 - 1,085

A. Leonardo Iniguez , 1 Yuemei Dong , 1 and Eric W. Triplett 2

1University of Wisconsin-Madison, Department of Agronomy, 1575 Linden Drive, Madison 53706 U.S.A.; 2University of Florida, Department of Microbiology and Cell Science, P.O. Box 110700, Gainesville 32611-0700 U.S.A.

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Accepted 8 June 2004.

In this report, all of the criteria necessary for the demonstration of nitrogen fixation in wheat (Triticum aestivum L.), the world's most important crop, are shown upon inoculation with a nitrogen-fixing bacterium, Klebsiella pneumoniae 342 (Kp342). Kp342 relieved nitrogen (N) deficiency symptoms and increased total N and N concentration in the plant. Nitrogen fixation was confirmed by 15N isotope dilution in the plant tissue and in a plant product, chlorophyll. All of these observations were in contrast to uninoculated plants, plants inoculated with a nitrogen-fixing mutant of Kp342, and plants inoculated with dead Kp342 cells. Nitrogenase reductase was produced by Kp342 in the intercellular space of the root cortex. Wild-type Kp342 and the nifH mutant colonized the interior of wheat roots in equal numbers on a fresh weight basis. The nitrogen fixation phenotype described here was specific to cv. Trenton. Inoculation of cvs. Russ or Stoa with Kp342 resulted in no relief of nitrogen deficiency symptoms.

Additional keywords: diazotrophic endophyte, endophytic colonization.

© 2004 The American Phytopathological Society