Effects of distinct phosphorus application on physiological responses and rhizosheath bacterial community diversity among three lupin species

White lupin (Lupinus albus) mobilize inaccessible phosphorus (P) by producing cluster root that can secrete carboxylates and enhance the phosphatase activity. Blue lupin (L. angustifolius) and yellow lupin (L. luteus) are classified in the same legume genus as white lupin, this study investigates whether blue and yellow lupins can evoke adaptation strategies under P scarcity.

For this pot experiment, three lupin species were subjected to -P, + Pi (NaH₂PO₄), and + Po (Phytate) treatments. After two months, we determined biomass and P allocation in lupins, Hedley-P fractions, exudate composition, and bacterial diversity in the rhizosheath under distinct treatments.

The results indicate white lupin accumulated high P content under -P and + Po treatments, while yellow lupin exhibited similar P content under + Po and + Pi treatments. Additionally, white lupin showed higher citrate secretion, ALPase, and PHYase activities under -P condition, as well as increased PHYase and β-Glu activities under + Po treatment. Particularly, the genera Segetibacter, Granulicell, Candidatus_Methylacidiphilum, and Bryobacter, which contributed to phytate activation, were simultaneously present in the rhizosheaths of both white and yellow lupins under + Po treatment.

This study elucidates the multifaceted physiological responses of lupins in adapting to P-deficient and provides novel insight into the role of rhizobacteria in phytate mobilization.