Location: Rangeland and Pasture Research2015 Annual Report
The vision of this research is to increase the ecological and economic sustainability of forage-based livestock production systems associated with the Southern Plains mixed-grass prairie. Our strategy is to minimize environmental impacts and increase the efficiency of plant and animal resources while addressing the production and conservation goals of the Southern Plains mixed-grass prairie. Over the next five years, we will focus on these following objectives: Objective 1: Develop enhanced germplasm of eastern gamagrass, sand bluestem, little bluestem, and Texas bluegrass for improved forage yield, forage quality, seed yield, and stand persistence. Objective 1A: Breed eastern gamagrass cultivars with improved biomass yield and other performance traits. Objective 1B: Continue to develop a diallel population of sand bluestem from 15 diverse accessions. Objective 1C: Breed little bluestem cultivars with improved forage and seed production. Objective 1D: Breed and evaluate pure Texas bluegrass and interspecific hybrids with improved performance traits. Objective 2: Develop perennial sorghum-based, interspecific, and wide hybrids with high sugar content for livestock and biofuel production on the Southern Plains. Objective 3: Evaluate the potential for using patch-burning and supplementation strategies on rangelands to improve the productivity of stocker cattle and beef cows while enhancing other ecological services. Objective 4: Evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. Objective 5: Evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production, and determine the environmental benefits of these grasses relative to other forages, and/or cropping options.
To identify germplasm with superior traits, expand the limits of germplasm variation by wide hybridization using interspecific and intergeneric introgression and genetic manipulation, evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production, and then release superior germplasm and improved cultivars. Broad-based germplasm collections of eastern gamagrass, Texas bluegrass, little and sand bluestems are maintained at the Southern Plains Range Research Station in Woodward, OK. Further, a major resource problem is over-used rangeland, making it susceptible to erosion and weeds, also compromising other ecological services. The challenge is to develop economic, energy-efficient forage grazing systems for the Southern Plains while maintaining or improving ecological service to wildlife and society. This research will employ basic agronomic, animal performance, plant and animal physiology, genetics, cytogenetic, and molecular biology experiments.
Progress was made in all four objectives, all which fall under National Program 215, Pastures, Forages, and Rangelands. Objective 1 in our project is to develop enhanced germplasm of native grasses for improved forage yield, forage quality, seed yield, and stand persistence. In the first subobjective, eastern gamagrass was planted in 2012 to test different germplasms and available cultivars of their tolerance to frequent defoliation by grazing cattle. During 2013 and 2014, full stand establishment was achieved and grazing began in June of 2014. At the time of this report, the germplasm and available cultivars have been grazed for one complete growing season. To the present, all cultivars have withstood the high rates of forage utilization with no apparent necrosis. As reported in 2014, preference by the cattle among the germplasm cultivars is still apparent based on residual herbage mass after grazing. In the second subobjective, to develop a diallel population of sand bluestem, we have continued to make progress in completing the crosses. After reducing the number of accessions to 11 in 2014, we have some seeds in all 110 [(11 female parents x 11 male parents) minus the 11 parents] possible crossings (cells). Our goal is to have greater than 10 seeds in every cell. To achieve this goal, we increased the number of seeds in 34 cells in 2015. In the third subojective, we are breeding little bluestem with improved forage and seed production characteristics. In this subojective, we have continued to narrow the little bluestem populations to meet our goals of improving forage and seed production in this species. Last year, we planted 11 polycrosses; seven populations for improved seed germination at low water potentials and four populations for high seed yield. The seven populations will be selected again this year for improved germination at low water potentials before the field testing. We have also begun the selection of the four populations selected for high seed yield to also improve the seed’s ability to germinate at a low water potential. In Objective 2, approximately 300 seeds were produced by interspecific and wide hybridizations of perennial sorghum based forage plants for livestock and biofuel production, mainly from the cross using sweet sorghum 'Dale' as the male parent. These seeds will be grown this fall in the greenhouse and screened by DNA markers and flow cytometry to detect the true hybrids. Objective 3 in our project is to evaluate the potential for using patch-burning and supplementation to improve the productivity of cattle and enhance ecological services. The experimental plots were established in 2013 on the rangeland. However, because of drought, this project has been delayed more because of insufficient fuel on the site to carry a fire; hence this experiment has been delayed until 2016. Objective 4 in our project is to evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. The experimental plots were laid out in 2013; we planted the plots in mid-April of 2014. Because of early-spring drought conditions, no plants emerged by mid June. Because of a low Palmer-Drought Index for April 2015, plots were not replanted as per the protocol; recent rains should allow for planting in April 2016.
1. Investigations into the genetics of Texas bluegrass (Poa arachnifera Torr.) have been an interest of agricultural scientist for at least four decades because of the fact that this cool-season native grass persist through the hot, dry summers of the southern Great Plains. Further, this grass has the ability to produce green, highly nutritious forage for grazing livestock and wildlife when the other native grasses are dormant. A breakthrough has recently revealed that the DNA content, or genome size, of this single species varies greatly across the southern Great Plains. Scientist from the USDA in Woodward, OK, in cooperation with researchers from Rice University, have discovered that Texas bluegrass from eastern Texas has twice as much DNA as plants collected from western Texas and Oklahoma. Because Texas bluegrass has female and male plants, it was tested to see if the genome sizes were linked to the sex of the plant, but this does not seem to be the case. These differences in genome size seem to be only associated with the latitude of the plants. Scientist are now looking to see if this genome size is associate with trait of interest like forage production, drought tolerance, or season of production. This discovery of genome size differences should prove useful in breeding this plant in to a species highly valuable to the agricultural community and wildlife on the southern Great Plains.
Oltjen, J., Gunter, S.A. 2015. Managing the herbage utilisation and intake by cattle grazing rangelands. Animal Production Science. 55:397-410.
Goldman, J.J. 2015. DNA contents in Texas bluegrass (Poa arachnifera) selected in Texas and Oklahoma determined by flow cytometry. Genetic Resources and Crop Evolution. 62(5):643-647.
Puterka, G.J., Giles, K.L., Brown, M.J., Nicholson, S.J., Hammon, R.W., Peairs, F.B., Randolph, T.L., Michaels, G.J., Bynum, E.D., Springer, T.L., Armstrong, J.S., Mornhinweg, D.W. 2015. Change in biotypic diversity of Russian wheat aphid (Hemiptera: Aphididae) populations in the United States. Journal of Economic Entomology. 108(2):798-804.