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Soybean Genetics Newsletter

Abstract

We are especially concerned with the genetic factors controlling symbiotic nitrogen fixation in soybeans. Four classical Mendelian factors have been identified in the macrosymbiont which regulate nodulation response (Vest et al., 1972). These are: Rj1, which in homozygous recessive condition produces a non-nodulating phenotype with a broad spectrum of Rhizobium strains (Williams and Lynch, 1954); Rj2, a dominant factor conditioning an ineffective response with strains of the Cl and 122 serogroups (Caldwell, 1966); Rj3, a factor conditioning an ineffective response with strain 33 (Vest, 1970); and Rj4, also a dominant factor, conditioning an ineffective response with strain 61 (Vest and Caldwell, 1972).

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