Phosphate (Pi) and arsenate uptake by two wheat (Triticum aestivum) cultivars and their doubled haploid lines

Arsenic accumulation in cereal crops represents an important pathway for human exposure to arsenic from the environment. The objectives of the present work were to find whether the relationship between arsenate and phosphate (Pi) uptake rate differs among genotypes and to select genotypes with a low arsenate uptake rate with the aim of improving food safety and human health.

A hydroponic experiment was conducted using two wheat (Triticum aestivum) cultivars (Hanxuan 10 and Lumai 14) and ten doubled haploid (DH) lines derived from them to investigate Pi and arsenate uptake over 48 h. Ten plants were transferred to bottles containing 50 mL of pre-treatment solution containing 0.5 mM CaCl2 and 5 mM MES set at pH 6.0 with 330 microM Pi as KH2PO4 and 7.33 microM arsenate. The solutions were aerated continuously. At 8, 24 and 48 h after uptake, 1 mL of test solution was sampled for determination of Pi and arsenate concentrations.

For each wheat line, Pi and arsenate concentrations in the test solution decreased with uptake time. Exponential (for Pi) or polynomial (for arsenate) regression plots fitted the data closely. For all genotypes, net Pi uptake rates decreased with time (from 0 to 48 h). However, net arsenate uptake rates decreased with time for D5, changed little with time for the male parent, D4 and D6, and increased with time for the others. An inflexion of about 25 microm Pi was observed for the relationship between arsenate and Pi concentrations in the test solution, indicating that 25 microm could be the point where the high-affinity uptake system 'switches on', or dominates over low-affinity uptake. In addition, the male parent, D1, D6 and D10 were considered ideal genotypes because they possess Pi transporters that discriminate strongly against arsenate and are expected to accumulate less arsenate in the field.