Molecular and Biochemical Mechanisms Underlying Phosphorus Use Efficiency in Hydroponically Grown Beta vulgaris L.

Phosphorus (P) is an essential plant macronutrient, and improving its acquisition and utilization could reduce fertilizer requirements in crop production. This study investigated associations between the candidate 1G0 marker at a SAUR-associated locus and root-vigor- and P-related traits in two F3 sugar beet families grown under a single controlled hydroponic nutrient regime. Total root length was significantly greater in Family 12 than in Family 15 at both measurement times, whereas Family 12 did not differ significantly from the commercial hybrid ‘Shannon’. Energy-dispersive X-ray fluorescence indicated a higher leaf P concentration in Family 12, while ICP-OES showed a difference in the same direction that was significant only before correction for multiple testing. The transcript assays labelled 1G0 and 1G0_HRM showed nominal differences among genotype classes, with higher relative transcript abundance in A/A than in G/G individuals. However, this result must be considered preliminary because the A/A class contained only three individuals and genotype was partially confounded with family background. Visible-range absorbance spectra showed a multivariate genotype-associated difference within Family 12, whereas reflectance, transmittance, and individual spectral indices showed no significant genotype effects after multiple-testing correction. Phosphoglucomutase activity was higher in Family 12 than in Family 15 but did not differ among 1G0 genotypes, indicating a family-level rather than marker-specific association. Overall, the results identify preliminary associations between the 1G0 marker and selected molecular and physiological traits. However, the use of a single P supply and the absence of measurements of whole-plant P accumulation, biomass-based P efficiency, proton extrusion, or plasma-membrane H⁺-ATPase activity preclude functional validation of the marker or the proposed mechanism. Validation in larger independent populations exposed to contrasting P supplies is required before 1G0 can be considered for marker-assisted selection.