Genetic and Physiological Characterization of the Non-nodulating Mutant of Phaseolus vulgaris L. -NOD125

Abstract

The physiology and genetics of the ethyl methyl sulphonate-induced non-nodulating mutant of Phaseolus vulgaris L., NOD125, have been investigated. The mutant failed to nodulate with 21 Rhizobium strains which effectively nodulated the wild type genotype RIZ30. The non-nodulating character is specifically expressed in the root and cannot be transferred by grafting the mutant shoot on to the wild type root. Inheritance of the non-nodulating phenotype shows that it is controlled by a single recessive gene which we have named sym-I. The mutant has been backcrossed with the wild type as the recurrent parent in order to obtain a non-nodulating RIZ30 isoline. In a preliminary test, in the presence of high concentrations of potassium nitrate, non-nodulating BC₁F₃ lines had a better yield compared with the original mutant genotype, assimilating mineral nitrogen with high efficiency. Thus, one or two more backcross cycles should be sufficient to achieve suitable material for use as a non-fixing reference plant in bean genotype field trials for nitrogen fixation.

Phaseolus vulgaris, Rhizobium, mutant, backcross, wild type