IMPROVING SYMBIOTIC NITROGEN FIXATION: A KEY APPROACH FOR A SUSTAINABLE SEED PRODUCTION IN LEGUME GRASSES

N.A. Provorov¹, A.P. Kozhemyakov¹ and L.T. Pushkina²

¹All-Russia Research Institute for Agricultural Microbiology, Podbelsky Sh., 3, St.Petersburg, Pushkin-8, 189620, Russia.

²Siberian Research Institute of Fodder Crops, Novosibirsk area, Krasnoobsk, 633128, Russia.

Inoculation with Rhizobium strains improved sufficiently seed production in legume grasses: alfalfa (Medicago sativa L., M. x varia Mart.), fenugreek (Trigonella foenum-graecum L.), sweet clovers (Melilotus albus Medik., M. officinalis (L.) Pall.) and goat's rye (Galega orientalis Lam.). A highly-effective R. meliloti strain CXM1-105 improved the alfalfa seed mass by 26.6%, while the herbage mass was improved by 8.7% only (in average for six cultivars).  The fenugreek inoculation with R. meliloti strains 851 and 852 improved seed mass by 60.5-83.1% while the herbage mass was improved by 93.6-94.5%. The goat's rye inoculation with five selected R. galegae strains improved seed mass by 36.1-57.7% while the herbage yield was not changed.  High intercultivar variation in symbiotic efficiency was revealed in sweet clover and alfalfa.  Two-factor analysis of variance demonstrated that the strain-specific plant polygenes (expressed as non-additive partners interactions) play a crucial role in controlling efficiency of "Melilotus sp. - R. meliloti" symbiosis.  A coordinated plant-microbe breeding should be carried out to increase N²-dependent seed production in the legume grasses.

Keywords: rhizobia; alfalfa; sweet clover; fenugreek; goat's rye; symbiotic efficiency, seed yield.