Efficiency of Phosphorus Use for Dinitrogen Fixation Varies between Common Bean Genotypes under Phosphorus Limitation

Low P availability in the soil is a major constraint to legume production, and efforts are being made to identify legume genotypes with tolerance to low P and greater phosphorus use efficiency (PUE) for N-2 fixation. Common bean (Phaseolus vulgaris L.) genotypes vary in their adaptation to low-P soils. To investigate to what extent this variation may be related to PUE for N-2 fixation, six recombinant inbred lines (RILs) of common bean contrasting in PUE for symbiotic N-2 fixation, namely RILs 147, 115, 104, 83, 34, and 29 were studied in the field conditions during four growing seasons from 2011 to 2015. We collected biomass (aboveground and belowground) at flowering stage, and both samples were analyzed P content. Results indicate that low-P availability in the soil significantly limited plant growth, nodulation, and N-2 fixation for all common bean RILs though with highest extent for common bean RILs 147, 83, and 29, whereas in this soil, common bean RILs 34 and 104 showed highest PUE for their N-2 fixation. The genotypes with high PUE for N-2 fixation showed greater mycorrhizal-plant symbiosis activity rate than the genotypes with low PUE for N-2 fixation. We also found a significant correlation between nodule biomass and nodule P content for all common bean RILs. We conclude that quantifying PUE for N-2 fixation may contribute to characterize the level of adaptation of N-2-fixing legumes to low-P soils.