Discovering Nitrogen Use Efficiency Heritability and Potential Using Ex-PVP Germplasm.

Genetic improvement of N-use efficiency in maize (Zea mays) can be associated with increased N-uptake efficiency (NUpE), N-utilization efficiency (NUtE), and genetic utilization (GU).  Genetic utilization describes the physiological efficiency of maize to convert plant N content into grain under N stress conditions. The objective of this research was to better understand the quantitative genetic variation of the N-use traits and their association with different maize heterotic groups using ex-plant variety protection germplasm (ex-PVP). During the years of 2011, 2013, and 2014, 264 single-cross maize hybrids using a combination of 93 ex-PVP inbreds (34 stiff stalk synthetic, SSS and 59 non-stiff stalk, NSS) were characterized for grain yield and N-use traits. Best unbiased linear predictor estimates for NUpE, NUtE and GU were 0.40 kg _plantN kg _N ^-1, 43.7 kg kg_plantN ^-1, and 59.2 kg kg_{plant N} ^-1, respectively. Heritability of GU (0.79) was greater than heritability for NUpE (0.57) and NUtE (0.39), indicating that GU is highly heritable. There was a large residual error variance associated with all N-use traits. Nonetheless, the genotypic variance components were significant for all N-use traits. The SSS heterotic group accounted for 63% of NUtE genotypic variance and 53% of GU genotypic variance compared to the NSS heterotic group. Genetic utilization could be used as a potential trait for genomic selection studies in breeding programs targeting for improved N-use efficiency.