Research Note A Method for the Positive Selection of Spontaneous Rhizobium Mutants Showing Transcriptional Activation of Nodulation Genes in the Absence of nod-Inducers. Jose Maria Vinardell. Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla. Apdo. 1095. 41080-Sevilla, Spain. Ana Maria Buendia-Claveria, and Jose Enrique Ruiz-Sainz. Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla. Apdo. 1095. 41080-Sevilla, Spain.. MPMI 6:782-785. Accepted 25 August 1993. Copyright 1993 The American Phytopathological Society.

A plasmid (pMUS248) containing a promoterless tetracycline resistance gene under the control of the Rhizobium leguminosarum bv. viciae nodA gene was constructed. Selection of tetracycline resistance in the absence of naringenin allowed the selection of spontaneous Rhizobium mutants showing transcriptional activation of nodulation genes in the absence of nod-inducers. These mutants were effective on Glycine max.