Plant Growth Promoting Rhizobacteria and Soybean [Glycine max(L.) Merr.] Nodulation and Nitrogen Fixation at Suboptimal Root Zone Temperatures
Abstract
Co-inoculation of plant growth promoting rhizobacteria (PGPR) with Bradyrhizobium has been shown to increase legume nodulation and nitrogen fixation at optimal soil temperatures. Nine rhizobacteria co-inoculated with Bradyrhizobium japonicum 532C were tested for their ability to reduce the negative effects of low root zone temperature (RZT) on soybean [ Glycine max (L.) Merr.] nodulation and nitrogen fixation. Three RZTs were tested: 25 (optimal), 17.5 (somewhat inhibitory), and 15°C (very inhibitory). At each temperature some PGPR strains increased the number of nodules formed and the amount of fixed nitrogen when co-inoculated with B. japonicum, but the stimulatory strains varied with temperatures. The strains that were most stimulatory varied among temperatures and were as follows: 15°C, Serratia proteamaculans 1-102; 17.5° C, S. proteamaculans 1-102 and Aeromonas hydrophila P73; 25°C, Serratia liquefaciens 2-68.