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Expression of a Serratia marcescens Chitinase Gene in Sinorhizobium fredii USDA191 and Sinorhizobium meliloti RCR2011 Impedes Soybean and Alfalfa Nodulation

August 1999 , Volume 12 , Number  8
Pages  748 - 751

Hari B. Krishnan , Kil Yong Kim , and Ammulu Hari Krishnan

Department of Plant Pathology, University of Missouri, Columbia 65211, U.S.A.

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Accepted 28 April 1999.

A gene encoding chitinase from Serratia marcescens BJL200 was cloned into a broad-host-range vector (pRK415) and mobilized into Sinorhizobium fredii USDA191. Chitinolytic activity was detected in S. fredii USDA191 transconjugants that carried the S. marcescens chiB gene. Chitinase-producing S. fredii USDA191 formed nodules on soybean cultivar McCall. However, there was a delay in nodule formation and a marked decrease in the total number of nodules formed by the chitinase-producing S. fredii in comparison with the wild-type strain. Expression of chitinase in S. meliloti RCR2011 also impeded alfalfa nodulation. Thin-layer chromatography of 14C-labeled Nod factors from chitinase-producing S. fredii USDA191 revealed hydrolysis of lipochitooligosaccharides.

© 1999 The American Phytopathological Society