Characterization and Effectiveness of Co-inoculation of Sinorhizobium Strains on Annual Medics

• Published in: Crop science Vol. 52; no. 2; pp. 932 - 942
• Main Authors: Singh, Ruchi, Interrrante, Sindy M, Butler, Twain J, Young, Carolyn A
• Format: Journal Article
• Language: English
• Published: Madison, WI Crop Science Society of America 01.03.2012; The Crop Science Society of America, Inc
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; biomass production; economics; forage quality; Fundamental and applied biological sciences. Psychology; grazing; indole acetic acid; inoculum; Medicago orbicularis; Medicago rigidula; plant growth; polymerase chain reaction; repetitive sequences; Sinorhizobium medicae; Sinorhizobium meliloti; solubilization; Medicago; Inoculation; Spermatophyta; Leguminosae; Dicotyledones; Angiospermae
• ISSN: 1435-0653; 0011-183X; 1435-0653
• DOI: 10.2135/cropsci2011.08.0459

Selection and identification of better-adapted annual medics with an appropriate rhizobia inoculum is crucial for improved forage quality and yield. The objectives of this study were to characterize 11 rhizobial strains used for an effectiveness study on annual medics and generate an inoculum blend suitable for annual medic species adapted to the southern Great Plains. Each strain was compared to reference rhizobia strains by polymerase chain reaction (PCR) based on repetitive sequences (rep-PCR) and ribosomal gene sequences and analyzed for plant growth promoting (PGP) activities. Genetic characterization separated the strains into two groups belonging to Sinorhizobium medicae (seven isolates) and Sinorhizobium meliloti (four isolates). Three of the 11 strains tested positive for the PGP activities of indole acetic acid production and phosphate solubilization. A blend of three strains (NFmix3, consisting of WSM1115, 102F85, and M49), of which two were positive for PGP activities, was used in an effectiveness study for the annual medics Medicago minima (L.) Bartal., Medicago orbicularis (L.) Bartal., Medicago rigidula (L.) All., and Medicago rigiduloides E. Small. The NFmix3 association with three of the four annual medic species resulted in equivalent biomass production as that of the single specific strain. The NFmix3 blend would be suitable and more economic for use with a mixture of medic species that may provide expansion of the grazing season.