Effects of Rhizobium strains on growth and nitrogen fixation of annual medics

Document Type : Research Paper

Authors

1 Research Institute of forests and Rangelands, Tehran

2 Scientific Board Member of Tehran Univesity

Abstract

Continuous grain cropping in many areas of the world has reduced soil nitrogen levels to a degree such that agricultural production is now largely dependent upon nitrogen fertilizer. Identification of highly effective legume and Rhizobium strain combinations, increased production of protein rich livestock forage and also improved the soil structure. Four species of annual medics (Medicago truncatula, M. littoralis, M. polymorpha, M. rigidula) were grown in all combinations with four various strains of Rhizobium meliloti (Locally, Hoomand, R95 and S13). There was also uninoculated check for each species. Control treatment (uninoculated) included mineral nitrogen (2.5 mM nitrate). All combinations of medics and rhizobium were grown without nitrate. Control treatment watered with nutrient solution contained 2.5 mM nitrate. Growth chamber experiment was conducted for 90 days to evaluate shoot dry matter and total shoot N. Medic lines varied in their ability to form an effective symbiosis with the rhizobia. M. truncatula has highest symbiotic with the strains Locally, Hoomand and R95. M. littoralis also in four inoculated treatment has %N near to control treatment.
M. rigidula had highest symbiosis with R95 and then S13. M. polymorpha had low symbiosis with all strains. M. truncatula had highest shoot dry matter (SDM) among five inoculated and uninoculated treatments (250 mg/plant). M. truncatula and M. littoralis exhibited similar response to all strains.
M. rigidula required specific strains of Rhizobium meliloti in order to fix more nitrogen. M. plymorpha hasn’t effective symbiosis with any of the strains that can result this plant required specific strain.

Keywords

References

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