Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2001
Publication Date: 2/1/2002
Citation: KHALIL, I.H., CARVER, B.F., KRENZER, E.G., MACKOWN, C.T., HORN, G.W. 2002. GENETIC TRENDS IN WINTER WHEAT YIELD AND TEST WEIGHT UNDER DUAL-PURPOSE AND GRAIN-ONLY MANAGEMENT SYSTEMS. CROP SCIENCE. v. 42. p. 710-715.
Interpretive Summary: Winter wheat is the primary winter forage grazed in the southern Great Plains (SGP). Nearly 8 million hectares of wheat planted yearly, and grain is often harvested from more than 3.2 million hectares or that is grazed. Traditionally, hard red winter wheat breeding programs develop cultivars for grain-only (ungrazed) production systems. We determined whether it is necessary for wheat breeding programs to use a forage-plus-grain production system when selecting new wheat cultivars for release to farmers in the SGP. Twelve widely adopted cultivars representing nearly 80 years of traditional breeding improvement in grain yield were compared using grain-only and graze-plus-grain production systems. THe breeding gains for yield were more evident for the grain-only system. In two of the three years, the breeding gains for yield were not evident when the forage-plus-grain system was used. These findings led us to expand our breeding objectives to include both production systems in the development of wheat cultivars for the SGP and allowed us to add direct selection criteria for the forage component of wheat. These results will be useful to wheat breeders and agronomists seeking to improve winter wheat grazing and grain production for farmers in the SGP.
Technical Abstract: Wheat (Triticum aestivum L.) cultivars of the southern Great Plains are traditionally bred in environments managed for grain production only, but are commonly used for the dual-purpose of producing winter forage and grain. We hypothesized that genetic improvement over time for grain yield and test weight of winter wheat may be expressed differently in dual-purpose versus grain-only management systems. A historical set of cultivars was evaluated over 3 yr under the two systems to compare their agronomic performance and derived estimates of genetic progress. Separate experiments were established for each system featuring whole- plot treatments of a foliar fungicide and split-plot treatments of 12 cultivars spanning from Turkey to 2174 (released in 1997). Dual-purpose experiments were generally grazed from November through February, with the intent to maximize animal performance and grain yield. Though the correlation between systems was high (r=0.89, P<0.01), estimates of yield progress differed markedly between systems. Yield in the grain- only system improved 18.8 kg/ha per yr, equivalent to 1.3% of the mean yield for Turkey or 0.7% of the mean of all cultivars in that system. The rate of progress in the dual-purpose system was significantly lower at 11.3 kg/ha per yr, equivalent to 0.9% of the mean for Turkey or 0.6% of the mean of all cultivars. Management for grazing had a more profound influence on estimates of yield improvement than did management for fungal disease protection. Trends in test weight were not evident in either system when averaged across years. Breeding practices should emphasize selection for grain yield in both environments if future progress is to be maximized in both.