Rhizobia selection for Lotus pedunculatus in acid soil

Abstract

A laboratory and glasshouse trial was conducted with the aim of selecting Rhizobium sp. for Lotus pedunculatus in acid conditions. Thirteen rhizobia strains were tested for their growing capacity in liquid media with pH 4.5, 4.7, 4.9 and 5.2. The limiting pH for these strains was 4.7, with only two strains growing in this pH (EEL 7784 and 7984). In pH 5.2 all the strains grew. In glasshouse these strains were tested in a Haplohumox soil with pH 5.1. In this soil it was possible to distinguish two groups of strains by their symbiotic efficiency based on nodulation, dry matter production and nitrogen accumulation in the shoot. The most efficient strains were SEMIA 839, USDA 3469, EEL 883, 1083, 4284 and 4484. The strain EEL 40 - with the same origin as USDA 3469 (=CC 814s) - and the strain USDA 3470 produced good nodulation but they were inefficient. Since these strains are considered efficient, this result suggests a possible loss of their efficiency.