Isolation and properties of soybean [ Glycine max (L.) Merr.] mutants that nodulate in the presence of high nitrate concentrations

Abstract

Soybean seeds [G. max (L.) Merr. cv. Bragg] were mutagenized with ethyl methanesulfonate. The M2 [2 generation] progeny (i.e., the 1st generation after mutagenesis) of these seeds were screened for increased nodulation under high nitrate culture conditions. Fifteen independent nitrate-tolerant symbiotic (nts) mutants were obtained from 2500 M2 families. In culture on sand with KNO3, nodule mass and nodule number in mutant lines were several-fold those of the wild type cultured under the same conditions. Inheritance of the nts character through to subsequent generations was observed in the 10 mutants tested. Mutant nts382 also nodulated more than the wild type in the absence of nitrate. Furthermore, nitrate stimulated growth in both the wild type and nts382, and these lines had similar nitrate reductase activity. The mutant nts382 is affected in a nodule-development regulatory gene and not in a gene related to nitrate assimilation.