Rhizosphere processes do not explain variation in P acquisition from sparingly soluble forms among Lupinus albus accessions

Seven Lupinus albus L. landraces were selected, based on their geographic origin and the soil type and pH at the site of collection of the seeds, and compared with the cv. Kiev mutant. We hypothesised that those landraces collected from red/yellow acidic sands (pH 5–5.7) would be better at acquiring P from FePO4 or AlPO4 than those selected from brown neutral (pH 7) or fine, calcareous, alkaline sands (pH 9), and that those selected from fine calcareous sands would be more effective at acquiring P from Ca5OH(PO4)3. Plants were grown in sand and supplied with 40 mg P/kg as the above sparingly soluble forms, or as soluble KH2PO4; control plants received no P. All genotypes were able to use these P sources. Variation in using poorly soluble P was not due to differences in rhizosphere carboxylate concentration, cluster-root development, or rhizosphere-extract pH. L. albus landraces with a better ability to use P from different sparingly soluble forms could be exploited to develop cultivars that are more P-acquisition efficient on soils that are low in [P] or highly P-sorbing; however, desirable genotypes cannot simply be selected based on soil type of origin.