Improving Adaptation through Genetic Differentiation of Winter Wheat Breeding Populations Subjected to Different Management Systems.

Winter wheat (Triticum aestivum L.) is widely used in the southern Great Plains as a winter forage resource to supplement income from a wheat monocrop system. Depending on production and prevailing market conditions, some producers may allow cattle (Bos Taurus L.) to graze wheat until the first hollow stem stage or to graze entirely.  Thus, winter wheat offers dual benefits of grain and beef production for in the form of two management system: grain-only (GO, with no grazing), and dual-purpose (DP, grazing and gain).  Although traditionally, winter wheat cultivars are developed in GO production systems, they are often deployed in DP systems. The incidence and severity of soil-borne and insect transmitted diseases, insect herbivory and abiotic stress are increased and thus can reduce grain yield depending on the year or cultivar. We hypothesized that a grazing system can be used as a selection tool to create breeding populations enriched with genes that confer grazing tolerance, persistence, and ultimately, improved adaptation.  However, no clear evidence exists, in wheat to refute or support that hypothesis. Thus the main objective of this research was to evaluate the selection responses in winter wheat induced by GO and DP management system. Grain yield and associated traits for 24 sets of populations were measured in GO and DP system, following natural selection in those systems for three consecutive generations. Research was conducted in Marshal, Oklahoma using the F₅ bulk progeny from each population. Our analyses resulted grain yield in a DP system can be increased by early-generation selection in that system, without negative consequences to grain yield in a GO system.