Growth and P uptake by wheat genotypes supplied with phytate as the only P source

In many soils, organic P is the major component of the total P pool. Genotypic differences in wheat for P acquisition from organic P in the form of phytate, a common organic phosphorus component in soil, were investigated in a glasshouse experiment. Twenty genotypes differing in the ability to utilise poorly soluble phosphate sources were grown in P-deficient brown sand amended with phytate or inorganic phosphate. The P efficiency of wheat genotypes was evaluated by 3 criteria: growth at low phytate-P supply; growth at low phytate-P supply relative to growth at the same rate supplied as soluble inorganic P; and phosphorus acquision efficiency (PAE), calculated as the amount of P in the plant divided by the amount of P supplied in the soil.All wheat genotypes tested were able to utilise phytate as a source of P, albeit at a lower efficiency than soluble inorganic phosphate. Across the genotypes tested, plants supplied with 20 mg P as phytate produced only 23% of the shoot biomass of plants supplied with 20 mg P as inorganic P. When P supply was increased to 100 mg P as phytate, this increased to 88%. There was a significant variation in wheat genotypes in the ability to acquire P from phytate. Genotypes more efficient in acquiring P from sparingly water-soluble Fe phosphates were also more efficient in taking up P from phytate-amended soil. The genotypes Cadoux, Blade, ES8, Chinese 80-55, Wawht 2066, and Wawht 2128 were rated as efficient, whereas Janz, Machete, Kalingri, and Spear were rated inefficient on all 3 criteria.