Influence of genotype on phosphate uptake and utilization efficiencies in spring barley

To investigate the genetic variation of phosphate (P) uptake and P utilization efficiency, 24 high-yielding spring barley cultivars were grown in two pot experiments on a loess loam-sand mixture. In the first experiment, the plants grew until maturity under P stress (50% of the maximum yield), and in the second experiment, the plants grew until the stage of tillering (DC 25) at a low or at a high P supply.

At maturity, the range between cultivars with the highest and the lowest values were 30% for total dm yield (grain and straw), 28% for grain yield, 24% for P uptake efficiency (P in grain and straw), 26% for P concentration in grains and 24% for P utilization efficiency quotient PEQ (g dm grain per mg P in shoots) (mean of all cultivars = 100%). Grain yield was correlated with P uptake per plant, r = 0.71^***, and with PEQ, r = 0.60^**. Between P uptake and PEQ, there was only a weak relationship (r = ?0.14). Therefore, a combination of high uptake efficiency and high PEQ in a cultivar may be possible.

At growth stage DC 25, the cultivars showed a significant variability in shoot biomass, P concentration, P removal, P influx, acitvity of acid phophatases (P_ase) and root length. The ranking of the cultivars, however, was very different at the two P levels, but the root-length and the P_ase activity were more influenced by genotype than by the P supply.

As the relationships between grain yield, P removal, PEQ and the characters of the young plants cultivated under P stress were very weak (r < 0.43), selection for P efficiency at the stage of tillering cannot be recommended.