Significant Yield Increase in Phaseolus vulgaris Obtained by Inoculation with a Trifolitoxin-producing, Hup⁺ Strain of Rhizobium leguminosarum bv. phaseoli

Abstract

The construction of a stably maintained, broad host range plasmid (pHUTFXPAR) carrying genes that enhance nodulation competitiveness through trifolitoxin production and efficient nitrogen fixation by oxidation of the H2 evolved from nitrogenase was reported by Kent et al. (7). Here the field testing of the efficacy of this construct is reported. pHUTFXPAR was inserted into Rhizobium leguminosarum bv. phaseoli 127K105a by conjugation. Three field experiments were conducted to test the ability of pHUTFXPAR to enhance the grain yield response provided by 127K105a on Phaseolus vulgaris. In 2000, the first trial was conducted at a University of Wisconsin field site in Madison. The second and third trials were performed at two Madison locations in 2002. All field experiments were conducted with 12 replicates of three treatments including uninoculated and inoculation with either 127K105a or 127K105a(pHUTFXPAR). The pooled dry seed weight from both years and both locations show significant 12 and 14% yield increases from the plants inoculated with 127K105a(pHUTFXPAR) compared to the uninoculated and the 127K105a treatments, respectively.