Higher leaf area and post-silking P uptake conferred by introgressed DNA segments in the backcross maize line 224

Many quantitative trait loci (QTLs) associated with phosphorus (P) acquisition and use efficiency in maize have been identified. To get a better understanding of the genetic control of P acquisition and grain yield in maize, a two-year field experiment with a line 224 from a backcross population, its donor parent 478 and recurrent parent 312 was conducted at three P levels. The results demonstrated an increased total leaf area and whole plant dry weight (DW), P uptake and grain yield in 224, compared with its recurrent parent 312, especially under extremely low P condition. The increase in total leaf area was explained by the increased length of immediately neighboring leaves around the ear. Similar with its donor parent 478, 224 took up more post-silking P than 312 at all P levels in both years, revealing previously unidentified functions of introgressed DNA segments from 478. On the other hand, irrespective of the increased P uptake, total root length and root vertical distribution in 0-40 cm soil profile of 224 was not increased compared with 312, although some QTLs related to root traits in line 224 had been proved to be derived from 478, an inbred line with larger root system. The results provide positive evidence for developing P-efficient crops with improved ability to acquire P and to increase grain yield under suboptimal P conditions through genetic approaches.