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This article in CS

  1. Vol. 29 No. 6, p. 1347-1350
    Received: Jan 18, 1989

    * Corresponding author(s):
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Genetic Allelism of Nodulation Response Genes Rjl, Rj2, and Rj4 in Soybean

  1. T. E. Devine  and
  2. J. J. O'Neill
  1. Plant Molecular Genetics Lab., Plant Sciences Inst., USDA-ARS, Beltsville Agric. Res. Center-West, Beltsville, MD 20705



Several qualitatively inherited genes (Rj1, Rj2, and Rj4) controlling nodulation response have been reported in soybean, Glycine max (L.) Merr. This study was undertaken to determine whether these alleles were located at distinct genetic loci, or whether one or more were located at the same locus. The F3 progeny from crosses of genetic stocks of each allele were evaluated for nodulation response. The responses due to the Rjl allele were evaluated in the field. The responses due to the Rj2 allele and the Rj4 allele were evaluated in sterile vermiculite in growth trays following controlled inoculation with bradyrhizobial strain USDA 7 or USDA 61, respectively. The F3 seed lots were subdivided to permit assay for more than one allele. Genotypes of F2 plants were rationalized from F3 progeny. Allelism tests established that the Rjl, Rfl and Rj4 alleles were distinct in their segregation and must be located at three distinct genetic loci. The Rjl gene has been located 40 ± 2 centimorgans from the F gene. Both Rj2 and Rj4 were found to segregate independently of the F locus, confirming that they are not at the Rjl locus. Therefore, soybean breeders have the option of constructing soybean genotypes containing all or any combination of these alleles if desired.

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