GENES-CONTROLLING NODULATION IN SOYBEAN - RJ5 AND RJ6

A number of genes have been identified that affect root nodule formati on in soybean [Glycine mar (L.) Merr.] when inoculated with Bradyrhizo bium japonicum (Kirchner) Buchanan. The non-nodulating mutant, NN5, us ed in this study was isolated from N-nitroso-N-methylurea mutagenized 'Williams' seed. The objectives of this study were to determine the nu mber of genes responsible for non-nodulation in NN5 and the relationsh ip between the genes in NN5 and the other known non-nodulation genes. From this study it was found that nonnodulation genes in NN5 were not allelic to the rj1 gene. One of the genes responsible for non-nodulati on in NN5 was allelic to the previously identified, but unnamed single recessive gene found in nod139, a non-nodulating mutant of 'Bragg'. A second recessive gene controlling non-nodulation was identified in NN 5 when crosses were made with 'Harosoy 63'. Harosoy 63 was shown to co ntain a non-allelic dominant gene that conditions nodulation when in c ombination with the gene found in nod139 and NN5. The gene symbol Rj5 is given to this new nodulation gene found in Harosoy 63, and the symb ol rj6 is given to the allelic gene conditioning non-nodulation in nod 139 and NN5. Several other cultivars, Williams, Williams 82, Chapman, Resnik, and Chamberlain, do not contain the dominant gene Rj5.