Thesis (Ph. D.)--University of Florida, 1985. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 137-150).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The Rhizobium-legume symbiosis is an opportunistic association between two symbiotic partners that results in the formation of the root nodule. The process depends on the expression of a number of plant and bacterial genes that are considered critical for the establishment and maintainance of the symbiotic state. The merits of a mutational approach to the analysis of symbiosis have been recognized for several years and transposon Tn5 mutagenesis of Rhizobium has led to the identification of several symbiotic genes. This study describes the use of Tn5 mutagenesis for the isolation of symbiotically defective mutants of Bradyrhizobium japonicum. Two classes, auxotrophic and cell surface-altered mutants defective in nodule formation, have been characterized. In B. japonicum USDA 122, histidine auxotrophs that are defective in nodulation have been studied. The mutagenized DNA region has been cloned and the wild-type DNA region isolated by hybridization and complementation. In B. japonicum 61A76, Tn5-induced cell surface-altered mutants have been isolated by selecting for bacteriophage resistance. Several parameters have been used to demonstrate alterations in cell surface components. It has been shown that the Tn5 insertion is not the primary cause of the mutation in two of the characterized mutants. Complementation tests have led to the isolation of a wild-type DNA-containing cosmid, pPS23A, that overcomes the symbiotic defect in one of the mutants. Analysis of the cell surface showed a partial restoration of surface components in the complemented mutant.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Universiẗat, Diss., 2002--Marburg.

No description available.

No description available.

Soybean [Glycine max (L.) Merr.] is a tropical to subtropical legume that requires root zone temperatures (RZTs) in the 25 to 30°C range for optimal symbiotic activity. The inability of soybean to adapt to cool soil conditions limits its development and yield in short season areas. In particular, nodulation and nitrogen fixation by this crop species is sensitive to cool RZTs. The isoflavone genistein, which is the most effective plant-to-bacterium signal in the soybean nitrogen fixation symbiosis, has been used to pretreat Bradyrhizobium japonicum inocula. This resulted in increased soybean nodulation and nitrogen fixation in several studies, indicating that genistein preincubated inocula could overcome low RZT inhibition of plant growth and yield. The effectiveness of isoflavones was found to vary among soybean cultivars. Some legume cultivars apparently supply limiting amounts of the flavonoids. The objective of this thesis was to determine how soybean cultivars of different maturity groups would respond to genistein incubation of B. japonicum prior to inoculation. Two field experiments were conducted in 1997 and 1998 involving eleven soybean cultivars of three maturity groups organized in a randomized complete block design. Cells of B. japonicum, treated with genistein or not, were applied onto seeds in the furrow at the time of planting. The results of this study indicated that genistein application increased nodule number and nodule dry matter per plant, increased plant nitrogen content, grain protein and grain yield of all cultivars. There was no interaction between maturity group and genistein application, and there was no correlation between maturity groups and increase in nodulation, total biomass, nitrogen content and yield due to genistein treatment. Thus, responses of soybean cultivars of different maturity groups to genistein treatment are not related to maturity and/or yield potential.

No description available.

No description available.