Abstract
Twenty commonly used winter wheat genotypes collected throughout China were used in field screening for phosphorus (P)-efficient germplasm in a calcareous soil with and without fertilizer P application; the same genotypes were also evaluated for high and low P inputs in a greenhouse experiment. The overall criterion for P efficiency was the capacity to produce a relatively high yield with low P availability. Significant differences in grain yield production occurred between efficient and inefficient genotypes. Four parameters were calculated to determine which was the most useful for describing P efficiency: (1) percentage of relative yield with no applied P; (2) total P uptake; (3) P-harvest index (PHI: grain P/total P uptake); and (4) P-utilization efficiency (PUE: grain yield produced per unit of P taken up). A simple but satisfactory criterion in screening P-efficient wheat genotypes, 85% of relative grain yield at low P/high P, was recommended and proved to be more effective than the other three parameters. With this criterion, 12 out of 20 genotypes were classified as P-efficient (≤ 15% yield reduction with no P applied) from both field and pot experiments. Phosphorus efficiency may have resulted from either P uptake or P-utilization efficiency. Three parameters, namely relative yield without applied P, PHI and PUE, were found to be useful, together with P uptake, in determining overall P efficiency. Successful selection for P efficiency was found to be possible at the shooting stage (but not at tillering) by comparing P uptake and P-utilization efficiency of plants at this growth stage with those of plants at maturity.
ACKNOWLEDGMENTS
This work was funded by the National Natural Science Foundation of China (Project No. 39790100). We thank numerous colleagues in the Research Center for Eco-Environmental Sciences and the Institute of Genetics, Chinese Academy of Sciences, for technical assistance.
Notes
aGrain P uptake + straw P uptake, mg pot− 1.
bGrain DM yield/(grain P uptake + straw P uptake), g DM g− 1 P.
cRatio of grain P uptake/(grain P uptake + straw P uptake).
aGrain P uptake + straw P uptake, mg pot− 1.
bGrain DM yield/(grain P uptake + straw P uptake), g DM g− 1 P.
cRatio of grain P uptake/(grain P uptake + straw P uptake).
*Significant at P < 0.05
**Significant at P < 0.01 (n = 20).
ryxi = correlation coefficient between Yi and Xi.
Sy = standard deviations for Xi and Yi, respectively.
The proportion of the sum of squares for Y attributable to Xi is ∑ XiY/∑ Y2 = (ryxi) Sxi/Sy.
*Significant at P < 0.05
**Significant at P < 0.01.
P-utilization efficiency at shooting stage represents DM produced by per g of P taken up.
*Significant at P < 0.05
**Significant at P < 0.01 (n = 60).