Response of Spring Wheat Varieties with and without “Stay-Green” Trait to Nitrogen Fertilizer.

Spring wheat (Triticum aestivum L.) varieties possessing “stay-green” trait may have an extensive grain filling period due to delayed leaf senescence, which could contribute to a greater grain yield compared with varieties without the “stay-green” trait. This study was to investigate 1) if spring wheat varieties with and without “stay-green” trait respond differently to N fertilizer inputs; and 2) contribution of preanthesis stem-reserved water soluble carbohydrate (WSC) and protein to grains through remobilization. A study was conducted at two locations in Montana under dryland and irrigated conditions. Three spring wheat varieties (two with “stay-green” trait and one without) were planted in the spring of 2008 at four N input levels (0, 45, 90, and 134 kg/ha at dryland site and 0, 56, 112, 168 kg/ha at irrigated site). Plant samples were cut from ground level at anthesis and maturity, and the head and stem were separated. Plant tissue samples were dried and ground for WSC and nitrogen (protein) analyses. The remobilization of WSC and protein was estimated from the concentration changes between the anthesis and maturity stages. Spring wheat varieties with and without “stay-green” trait responded similarly to N fertilizer under either dryland or irrigated conditions. Grain yield was 1120 kg/ha at 0 N input level and 1760 kg/ha at the optimum N input level of 90 kg N /ha at dryland site; while the grain yield was 3700 kg/ha at 0N input level and 6720 kg/ha at the optimum N input level of 112 kg N/ha. The contribution of preanthesis stem WSC and protein to grain yield and protein was 11% and 80%, respectively, and did not differ among the varieties and N input levels at the dryland site. At the irrigated site, however, the contribution of preanthesis stem WSC to grain yield decreased from 15% with 0 N input to 5% with 168 kg/ha N input. The contribution of preanthesis stem protein to grain protein decreased from 80% at 0N input level to 45% at 168 kg/ha N input level. There was no significant difference between the varieties with and without “stay-green” trait.