9 Martinus Nijhoff Publishers, Dordrecht--Printed in the Netherlands PLSO 7018 Symbiotic effectiveness of indigenous arctic rhizobia on a temperate forage legume: Sainfoin (Onobrychis viciifolia)*

Sainfoin (Onobrychis viciifolia), a temperate perennial forage legume, can be nodulated by rhizobia isolated from 3 arctic legume species: Astragalus alpinus, Oxytropis maydelliana nd Oxytropis arctobia. Arctic rhizobia, which are adapted to growth at low temperatures, may be useful in improving symbiotic nitrogen fixation during cold phases of the growing season, if they are effective on a temperate l gume. In this study, we report on the symbiotic effectiveness ofarctic rhizobia on sainfoin, as appraised by the total shoot dry matter yield obtained from 2 harvests. Under N-free conditions, 5 arctic strains at the first harvest and 8 at the second harvest were as effective as temperate standard strains. In the presence of 30mgl-NO3-N, 7 arctic strains gave significantly higher yields than temperate strains at the second harvest. These results indicate that effective arctic rhizobia have a potential for use as inoculants on sainfoin