Characterization of a Spontaneous Phaseolus Vulgaris Mutant with the Ability to Selectively Restrict Nodulation
A spontaneous Phaseolus vulgaris mutant was isolated that selectively restricts nodulation. This recessive mutation exhibits a phenotype that has never been seen before with beans and is a perfect tool to study the symbiotic relationship and the associated signaling molecules between legumes and Rhizobia. The goal of this dissertation was to characterize the mutant bean’s morphology and nodulation capacity. Rhizobial screening was done to examine how many different strains of Rhizobia were able to nodulate the mutant bean. The bean was examined for phenotypic characteristics and then examined for how the mutation was affecting nodulation. This was done by using green fluorescently labeled bacteria to visualize steps in the nodulation process and by chemical isolation and characterization of the signals involved in forming the symbiosis. This research also examined the overall competitiveness of strains with the ability to nodulate the mutant bean. A final experiment used Tn5 mutagenesis of USDA 2669 to determine if any novel signaling molecules were present in the excluded strain. It was determined that the mutant P. vulgaris had no deleterious phenotypic characteristics and that three strains of Rhizobia, USDA 9017, USDA 9032 and USDA 9041, had the ability to nodulate the mutant. It was also demonstrated that the mutation blocked nodulation before the formation of infection threads and therefore was affecting the plant's perception of the bacterial signal.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:phaseolus vulgaris rhizobia symbiosis nitrogen fixation
Date of Publication:01/01/2006