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Research Project: Sustaining Southern Plains Landscapes through Plant Genetics and Sound Forage-Livestock Production Systems

Location: Rangeland and Pasture Research

2016 Annual Report


Objectives
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.


Approach
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 Report
Progress was made in all four objectives, all of which are contributing to the National Program 215, Pastures, Forages, and Rangelands Systems. Objective 1 of our project is to develop and enhance germplasm of native grasses for improved forage yield, seed yield, and stand persistence. In the first subobjective (Objective 1A), the plant performance data for the third year has been collected from the gamagrass experiment designed to identify plants with significant grazing resistance. In the replicated variety trial, which includes new experimental varieties of eastern gamagrass, plants were transplanted to the field in June of 2016 and replacement plants were added to the plots that were planted in 2015 where plants did not fully establish. In Subobjective 1B, we have completed making crosses and now have a complete diallel crossing for 11 of 15 diverse sand bluestem accessions. We have had limited success in making crosses with 4 of the accessions, thus, we did not meet the required seed numbers for the diallel series. Therefore, these 4 accessions were removed from the experiment. In Subobjective 1C, we released seven little bluestem germplasm lines primarily selected for canopy morphology. With these little bluestem grasses, the germplasm lines NU-1 and NU-2 have a 'not-upright' (NU) canopy morphology that is characterized by a hemispherical shape and diffuse culms. Lines UC-1 and UC-2 have an 'upright-compact' (UC) canopy morphology that is characterized by a columnar shape and erect culms, and UO-1, UO-2, and UO-3 have an 'upright-open' (UO) canopy morphology that is characterized by a caespitose shape with ascending culms. These lines also show resistance to leaf rust (Puccinia andropogonis), resistance to culm lodging, and tolerance to higher-pH soils. These germplasm lines will be useful for the breeding and development of new cultivars intended for many purposes, such as, wildlife habitat, livestock grazing, soil stabilization, or biomass for renewable energy. We did not plant regional trials of the advanced lines, selected for better germination at a low water potential, due to the lack of seed to plant at all locations. Hence, we did plant advanced lines at Woodward, OK and they are performing as expected; we expect to plant the other locations in 2017. This research has shown that selection for greater germination at a low water potential produces germplasm lines with greater stand emergence and plant densities in the field. In Subobjective 1D, a selection of seeds from the D4 Texas bluegrass ecotype that germinated at low water potential were planted in isolation nurseries and seed was harvested in April 2016. Seed was also harvested from the original D4 isolated seed increase nursery. Seeds from promising hybrids are now under evaluation that were harvested from plants in the field and in the greenhouse. In our high-risk project, Objective 2, Hybrid seed was not obtained from the crosses which eliminated the opportunity to screen material for sugar content. A Saccharum spontaneum (wild sugarcane) plant initially flowered for the first time in the greenhouse in 2015. Hence, if timing for cross pollination is compatible, this plant is planned to be crossed with a male sterile line of sorghum this summer. Objective 3, to 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 research, has continued and all data was successfully collected this year. In Objective 4, we have discontinued our work to evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. We did begin the experiment in FY13, but in subsequent years we did not plant the experiment due to severe drought concerns at time of planting and the prediction of continued drought for the establishment season. We may revisit this objective when superior plant materials are released for little bluestem from subobjective 1C.


Accomplishments
1. Little bluestem selected for differing canopy morphology (Schizachyrium scoparium (Michx.) Nash) is a perennial, bunchgrass indigenous to North American prairies and open woodlands from southern Canada to northern Mexico. Little bluestem germplasm lines NU-1, NU-2, UC-1, UC-2, UO-1, UO-2, and UO-3 were developed and released by USDA-Agricultural Research Service in 2016. Germplasm lines NU-1 and NU-2 have a 'not-upright' (NU) canopy morphology that is characterized by a hemispherical shape and diffuse culms. Lines UC-1 and UC-2 have an 'upright-compact' (UC) canopy morphology that is characterized by a columnar shape and erect culms, and UO-1, UO-2, and UO-3 have an 'upright-open' (UO) canopy morphology that is characterized by a caespitose shape with ascending culms. The plant inventory numbers for NU-1, NU-2, UC-1, UC-2, UO-1, UO-2, and UO-3 are PI 676262, PI 676263, PI 676264, PI 676265, PI 676266, PI 676267, and PI 676268, respectively. Little bluestem, by virtue of its outcrossing, is an ideal species for breeding new cultivars for pasture and rangeland renovation, roadside revegetation, wildlife habitat, and recreation areas. These germplasm lines are a first step for the breeding and development of cultivars useful for wildlife habitat, grazing utilization, roadside stabilization, and renewable energy.


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Review Publications
Springer, T.L., Goldman, J.J. 2016. Germination of Saccharum ravennae(L.)L.(Poaceae) caryopses and intact spikelets. Crop Science. 56:682-688.
Springer, T.L., Goldman, J.J. 2016. Seed germination of five Poa species at negative water potentials. American Journal of Plant Sciences. 7:601-611.
Gunter, S.A., Cole, N.A. 2016. INVITED REVIEW: Getting more information from your grazing research beyond cattle performance 1,2. Professional Animal Scientist. 32(1): 31-41.