Phosphorus efficiency in soybean genotypes: investigating morphological and physiological plant traits

Abstract This study aimed to (i) classify soybean genotypes related to P uptake and utilization efficiencies and responsiveness to P supply; (ii) investigate plant morphological and physiological characteristics related to P efficiencies; and (iii) identify plant traits for selecting P–efficient genotypes. Sixteen soybean genotypes grew under deficient and sufficient P supply (10 and 100 µmol P L − 1 ). Phosphorus absorption kinetic parameters, root morphology, growth, photosynthetic, and nutritional parameters were determined to investigate the P acquisition efficiency (PAE) and P utilization efficiency (PUE). Soybean genotypes with high PAE exhibited a twofold greater P influx, and approximately 25% lower values of both the Michaelis–Menten constant (K m ) and the minimum solution concentration at which influx ceases (C min ) compared to low–PAE genotypes. Specifically, K m values decreased from 0.66 to 0.68 in low-PAE genotypes to 0.52–0.59 in high–PAE genotypes, while C min values decreased from 0.80 to 0.86 to 0.65–0.78, respectively. Genotypes with high PUE showed higher rates of net photosynthesis and electron transport, and leaf area, associated with lower light stress than low PUE genotypes. Only one soybean genotype (BMX 50i52 IPRO) was efficient in both acquisition and utilization of P, as well as responsive to P application. Leaf area may represent a promising trait for the initial screening of P-efficient soybean genotypes, although validation under soil and field conditions is still required. Our findings provide foundational knowledge for bioengineering soybean P–efficient genotypes, possibly assisting in reducing the overall reliance on P fertilization even more relevant under P impoverished environments.