Cropping History Affects Nodulation And Symbiotic Efficiency Of Distinct Hairy Vetch (Vicia Villosa Roth.) Genotypes With Resident Soil Rhizobia

Compatible rhizobia strains are essential for nodulationand biological nitrogen fixation (BNF) of hairy vetch(Vicia villosa Roth, HV). We evaluated how past HV cultivationaffected nodulation and BNF across host genotypes. Fivegroups of similar HV genotypes were inoculated with soildilutions from six paired fields, three with 10-year HV cultivationhistory (HV+) and three with no history (HV-), andused to determine efficiency of rhizobia nodulation and BNF.Nodulation was equated to nodule number and mass, BNF toplant N and Rhizobium leguminosarum biovar viceae (Rlv)soil cell counts using qPCR to generate an amplicon of targetedRlv nodD genes. Both HV cultivation history andgenotype affected BNF parameters. Plants inoculated withHV+ soil dilutions averaged 60 and 70 % greater nodulenumber and mass, respectively. Such plants also had greaterbiomass and tissue N than those inoculated with HV- soil.Plant biomass and tissue N were strongly correlated to nodulemass (r2=0.80 and 0.50, respectively), while correlations tonodule number were low (r2=0.50 and 0.31, respectively). Although hairy vetch rhizobia occur naturally in soils, pastcultivation of HV was shown in this study to enhance nodulationgene-carrying Rlv population size and/or efficiency ofrhizobia capable of nodulation and N fixation.