Effectiveness of Sinorhizobium Inoculants on Annual Medics

Abstract

Annual medics (Medicago spp.) have potential to be important forage legumes in the southern Great Plains of the United States. Currently there are no commercial medic species‐specific rhizobia strains identified for their inoculation. However, commercially available alfalfa (Medicago sativa L.) inoculants may be effective at successfully nodulating annual medics. The objective of this study was to determine the relevant symbiotic rhizobial partner in association with seven annual medics. A greenhouse experiment arranged in three replications of a randomized complete block design quantified rhizobium effectiveness index and shoot and root dry matter (DM) of Medicago arabica (L.) Huds., Medicago lupulina L., Medicago minima (L.) Bartal., Medicago orbicularis (L.) Bartal., Medicago polymorpha L., Medicago rigidula (L.) All., and Medicago rigiduloides E. Small when inoculated with five Sinorhizobium spp. strains (M2, M49, Nitragin A, Nitragin N [a blend of three isolates], and WSM1115) and an untreated control (UTC). Strain M49 was the only strain that effectively nodulated M. rigiduloides, while Nitragin A commercial alfalfa strain was only effective on M. rigidula. Inoculants M2, Nitragin N, and WSM1115 were able to effectively nodulate M. polymorpha, M. arabica, M. minima, and M. orbicularis. To a lesser extent, M. lupulina, M. minima, and M. orbicularis were also effectively nodulated by Nitragin A alfalfa strain. These data indicate that there are differences in rhizobia specificity of annual medic species, and further research is warranted to improve nodulation of these legumes in the field.

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

“…Comparative data of dry weight and effectiveness index provided strong evidence for selective nodulation by annual medics. These results are in accordance with the finding of Interrante et al (2011) whereby total plant dry biomass followed the same trends as was observed by rhizobia effectiveness index (Fig. 3A and 3B).…”

“…The NFmix3 performed as effectively for M. orbicularis and M. rigiduloides when compared to the most effective isolate as reported by Interrante et al (2011). However, NFmix3 was not as effective on M. minima as the single specific strain WSM1115 but performed equally as well as 102F85, which was reported as the second most effective strain by Interrante et al (2011).…”

“…Seeds were surface sterilized in 95% (v/v) ethanol (15 min) and 0.2% HgCl 2 (v/v) for 60 min and then rinsed thoroughly with sterile water. Twenty seeds of a single species were planted per pot and grown in 1.9‐L bottom‐watered pots (Apollo Plastics Ltd., Mississauga, ON) containing 1:1 ratio by volume of washed and autoclaved masonry sand and vermiculite as described by Interrante et al (2011). Inoculant strains were cultured in YEM broth for 4 d at 28°C.…”

“…Recently seven annual medics ( Medicago arabica (L.) Huds., Medicago lupulina L., M. minima , M. orbicularis , M. polymorpha , M. rigidula , and M. rigiduloides ) were evaluated for their ability to form effective symbiotic associations with 11 rhizobial stains, WSM1115, M2, 102A13, 102B11, 102H2, WSM540, W118, 102F85, M18, M49, and RR1128, and significant difference in rhizobia specificity to these annual medics was found (Interrante et al, 2011). To identify reasons for the difference in sinorhizobial specificity noted by Interrante et al (2011), characterization of these 11 Sinorhizobium strains was performed using a polyphasic approach. Strains were genotypically characterized by rep‐PCR using BOX elements and sequence analysis of 16S and intergenic spacer (IGS) region and assessed for the PGP activities of phosphate solubilization and IAA production.…”

Characterization and Agronomic Evaluation of Local Populations of Medicago minima (L.) Collected in Algerian Steppe Area

“…Zhu et al (1998) reported that medics have the ability to fix 100-200 kg N per ha per year with appropriate rhizobia inocula. They have the potential to increase forage production and extend the grazing season (Interrante et al, 2011).…”