Enhancing phosphorus uptake efficiency through QTL-based selection for root system architecture in maize

Root system architecture(RSA) plays an important role in phosphorus(P) acquisition,but enhancing P use efficiency(PUE) in maize via genetic manipulation of RSA has not yet been reported.Here,using a maize recombinant inbred line(RIL) population,we investigated the genetic relationships between PUE and RSA,and developed P-efficient lines by selection of quantitative trait loci(QTLs) that coincide for both traits.In low-P(LP) fields,P uptake efficiency(Pup E) was more closely correlated with PUE(r =0.48-0.54),and RSA in hydroponics was significantly related to Pup E(r=0.25-0.30) but not to P utilization efficiency(Put E).QTL analysis detected a chromosome region where two QTLs for PUE,three for Pup E and three for RSA were assigned into two QTL clusters,Cl-bin3.04 a and Cl-bin3.04 b.These QTLs had favorable effects from alleles derived from the large-rooted and high-Pup E parent.Marker-assisted selection(MAS) identified nine advanced backcross-derived lines carrying Cl-bin3.04 a or Cl-bin3.04 b that displayed mean increases of 22%e26% in PUE in LP fields.Furthermore,a line L224 pyramiding Clbin3.04 a and Cl-bin3.04 b showed enhanced Pup E,relying mainly on changes in root morphology,rather than root physiology,under both hydroponic and field conditions.These results highlight the physiological and genetic contributions of RSA to maize Pup E,and provide a successful study case of developing P-efficient crops through QTL-based selection.