P-405 - Evaluation of rhizobia isolated from nodules of an interspecific hybrid Lotus uliginosus × Lotus corniculatus

The hybrid G1 was developed from a cross-breeding between Lotus uliginosus and Lotus corniculatus. The parent species belong to different inoculation compatibility groups, which refer to the specificity between these different Lotus species and the rhizobia genera capable of forming efficient nodules on their roots. Therefore, L. uliginosus and L. corniculatus require different commercial inoculants: Bradyrhizobium sp. U526 and Mesorhizobium sp. U510, respectively. Hybrid plants do not have a specific inoculant, which raises the question of which inoculation group they belong to. We evaluated rhizobia strains isolated from nodules of hybrid plants grown on experimental field trials. Only one Bradyrhizobium sp. was identified among thirteen efficient isolates; the rest were Mesorhizobium spp. Among the latter, Mesohizobium sp. H7 was selected for further evaluation in hybrid and parental species. We observed that strain H7 was efficient in hybrid plants and also in the parental species L. uliginosus. Hybrid plants exhibited inefficient nodulation with Mesorhizobium sp. U510 and variable results with Bradyrhizobium sp. U526. These unexpected results suggest that strain H7 could be a broad-range rhizobium, making it a promising candidate for further evaluation in the inoculation of hybrid G1.