caa a22 4500 47710956X CHVBK 20180405111604.0 cr unu---uuuuu 170330e19960601xx s 000 0 eng 10.1007/BF00010452 doi (NATIONALLICENCE)springer-10.1007/BF00010452 Influence of drought on competition between selected Rhizobium meliloti strains and naturalized soil rhizobia in alfalfa [Elektronische Daten] [Mohammad Athar, Douglas Johnson] Drought is an important environmental factor that can affect rhizobial competition and N2 fixation. Three alfalfa (Medicago sativa L. and M. falcata L.) accessions were grown in pots containing soil from an irrigated (Soil 1) and a dryland (Soil 2) alfalfa field in northern Utah, USA. Mutants of three strains of Rhizobium meliloti Dang. from Pakistan (UL 136, UL 210, and UL 222) and a commercial rhizobial strain 102F51a were developed with various levels of resistance to streptomycin. Seeds inoculated with these individual streptomycin-resistant mutants were sown in the two soils containing naturalized rhizobial populations. Soils in the pots were maintained at −0.03, −0.5, and −1.0 MPa. After 10 weeks, plants were harvested and nodule isolates were cultured on agar medium with and without streptomycin to determine nodule occupancy (proportion of the nodules occupied by introduced rhizobial strains). Number of nodules, nodule occupancy, total plant dry weight, and shoot N were higher for Soil 1 than Soil 2. Number of nodules, plant dry weight, and shoot N decreased as drought increased from −0.03 to −1.0 MPa in the three alfalfa accessions. Rhizobial strains UL 136 and UL 222 were competitive with naturalized alfalfa rhizobia and were effective at symbiotic N2 fixation under drought. These results suggest that nodulation, growth, and N2 fixation in alfalfa can be improved by inoculation with competitive and drought-tolerant rhizobia and may be one economically feasible way to increase alfalfa production in water-limited environments. Kluwer Academic Publishers, 1996 competition nationallicence drought nationallicence Medicago falcata nationallicence Medicago sativa nationallicence nitrogen fixation nationallicence nodulation nationallicence rhizobia nationallicence Athar Mohammad Department of Rangeland Resources, Utah State University, 84322-5230, Logan, UT, USA aut Johnson Douglas Department of Rangeland Resources, Utah State University, 84322-5230, Logan, UT, USA aut Plant and Soil Kluwer Academic Publishers; gopher://gopher:wkap.nl 184/2(1996-06-01), 231-241 0032-079X 184:2<231 1996 184 11104 https://doi.org/10.1007/BF00010452 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00010452 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Athar Mohammad Department of Rangeland Resources, Utah State University, 84322-5230, Logan, UT, USA aut NATIONALLICENCE 700 1- Johnson Douglas Department of Rangeland Resources, Utah State University, 84322-5230, Logan, UT, USA aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; gopher://gopher:wkap.nl/ 184/2(1996-06-01), 231-241 0032-079X 184:2<231 1996 184 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer