Effects of Different Rhizobacteria on Nodulation and Nitrogen Fixation in Alfalfa (Medicago sativa) at Suboptimal Root Zone Temperatures

摘要

Co-inoculation of plant growth promoting rhizobacteria (PGPR) with Sinorhizobium meliloti has been shown to increase legume nodulation and nitrogen fixation at suboptimal soil temperatures. In this work, three rhizobacteria (Pseudomonas, Azotobacter and Azospirillum) co-inoculated with S. meliloti were tested for their ability to reduce the negative effects of low root zone temperature (RZT) on alfalfa (Medicago sativa L.) nodulation and nitrogen fixation. Three RZTs were tested: 25 (optimal), 15 (somewhat inhibitory) and 10°C (very inhibitory). The results of this study indicate that nodulation was inhibited under suboptimal root zone temperatures. At low temperature PGPR strains increased the number of nodules formed and the amount of fixed nitrogen when co-inoculated with S. meliloti, but the stimulatory strains varied with temperatures. Rhizobium and Pseudomonas co-inoculation moderated the negative effects of low temperatures on nodulation and nitrogen fixation in alfalfa plants.