Photoperiod Response Gene Ppd-D1 Affects Nitrogen Use Efficiency in Soft Red Winter Wheat

Optimal N application is critical to ensure profitable soft red winter wheat (Triticum aestivum L.) production and limit negative environmental effects. This study was conducted using 12 wheat lines grown in two Ohio and six Virginia environments to determine the effects of differentially split N rates on grain yield, yield components, and N-related traits. Upon analysis of wheat lines in two contrasting photoperiod groups, it was discovered that wheat lines containing the photoperiod sensitivity allele (Ppd-D1b) conferred a significant (P < 0.05) yield advantage under N-limited conditions in Ohio and across N treatments in half of the Virginia testing environments. This resulted from increased harvest index, grains per square meter, number of kernels per spike, and floret fertility in Ppd-D1b lines relative to lines with the insensitive allele (Ppd-D1a). However, wheat genotypes in the photoperiod-insensitive allelic group had significantly higher (P < 0.05) grain N concentration in all Virginia testing sites. A spring split N application of 33 kg N ha⁻¹ at Zadoks growth stage (GS) 25 and 101 kg N ha⁻¹ at Zadoks GS 30 produced the highest grain yields and grain N contents in five of the six Virginia environments. Nitrogen utilization efficiency was the primary contributor to variation in N use efficiency under higher N rates, whereas N uptake efficiency was the greatest contributor under low N rates. The contribution of N utilization and uptake efficiencies varied among wheat lines in the Ppd-D1a group when 67 kg N ha⁻¹ was applied at Zadoks GS 25 under the moderate and standard N rates.