Rhizobial symbiosis efficiency increases in common bean under sparingly soluble calcium-phosphorus

The use of phosphate-solubilizing rhizobia as a rhizobial inoculant improves plant nutrient uptake (nitrogen (N) and phosphorus (P)) and subsequently crop yield stability. Three common bean varieties namely Coco blanc, Wafa, and Rebia were inoculated with the Rhizobium strain “Ar02” and grown under 250 μmol P as KH₂PO₄ Pi and 250 μmol P as Ca₃HPO₄ (Ca-P). Rebia showed the highest root biomass increase (35%) both under Pi and Ca-P supplies, while Wafa's root biomass significantly decreased under Ca-P condition. Application of Ca₃PO₄ stimulated acid phosphatase activities in shoots (50%), roots (45%) and nodules (49%) of Coco blanc variety as compared to Rebia and Wafa. Moreover, phenols content was enhanced in Wafa roots as compared to Coco blanc roots. N content increased in shoots (14% under Pi and Ca-P supplies) and nodules (6% under Ca-P supplies) of Coco blanc. P and K nutrition largely varied in response to P supplies through all plant parts.