• Gains of Steers and Calves Grazing Crested Wheatgrass

      Hart, R. H.; Balla, E. F.; Waggoner, J. W. (Society for Range Management, 1983-07-01)
      Efficient utilization of pasture requires proper class of livestock, stocking rate, and season of use. Crested wheatgrass was grazed with steers in spring for 3 years at two stocking rates and with calves in fall for 2 years at 2 stocking rates to evaluate alternate uses. Differences in forage production and lengths of grazing season over years produced grazing pressures of 47-79 steer days or 53-73 calf days per metric tonne of forage produced. Steer gains of 0.85-1.20 kg/day were unaffected by grazing pressure, but lighter steers gained faster. Implantation of 36 mg of Ralgro per steer increased daily gains by 13%. Calf gains were 0.15-0.24 kg/day, and decreased with increasing grazing pressure according to the function ADG=0.45-0.0041 (calf days/tonne forage); r2=0.95. Such grazing pressure-gain response functions facilitate comparisons between seasons of use and class of livestock, as well as those between stocking rates, and help range managers make management decisions. Maximum steer gains in spring per hectare and tonne of forage were over 3 and 6 times, respectively, the gains of calves in fall.
    • Gambel Oak Control Studies in Southwestern Colorado

      Marquiss, R. W. (Society for Range Management, 1973-01-01)
      Gambel oak (Quercus gambelii) was treated with several brush-killing herbicides in southwestern Colorado. Tordon, alone or in a mixture, as a foliar spray increased the percentage of dead stems and reduced the occurrence of root sprouts when compared to other herbicides tested. One-half pound of Tordon 22K mixed with 2,4,5-TP at the 1 1/2 and 2-pound rates (ae/acre) and Tordon 22K at the 2-pound rate have resulted in the best herbicide treatments for controlling Gambel oak in southwestern Colorado.
    • Gambel oak root carbohydrate response to spring, summer, and fall prescribed burning

      Harrington, Michael G. (Society for Range Management, 1989-11-01)
      Control of Gambel oak (Quercus gambelii Nutt.) for increased forage production and conifer regeneration is difficult because of its vigorous sprouting ability. Nonstructural root carbohydrate concentrations, generally a good indicator of sprouting potential, were measured in understory Gambel oak in a dense ponderosa pine (Pinus ponderosa Laws.) stand following prescribed fire. Carbohydrates in roots of 1- to 2-year-old sprouts after a single fire treatment were similar to those in unburned, mature oaks. Two prescribed burns, 2 years apart during the summer carbohydrate depression, caused these root reserves to remain low into fall dormancy and probably contributed to an observed oak reduction. This summer carbohydrate depression, also observed in open-grown Gambel oak, can be recognized by rapid stem growth and new leaf production.
    • Game Animals: A Substitute for Cattle?

      Lambrecht, Frank L. (Society for Range Management, 1983-02-01)
    • Game Ranching in Western Canada

      Renecker, Lyle A.; Kozak, Henry M. (Society for Range Management, 1987-10-01)
    • Games People Play: Human Behavior and Invasive Weed Management

      McCoy, Nicole Haynes; Amatya, Pradyumna (Society for Range Management, 2005-12-01)
    • Gas exchange and water relations of Lemmon's willow and Nebraska sedge

      Svejcar, T. J.; Trent, J. D. (Society for Range Management, 1995-03-01)
      There is considerable interest in riparian zones in the western United States, yet little information is available on the autecology of plant species that dominate these areas. We measured gas exchange and xylem water potential of Nebraska sedge (Carex nebrascensis Dewey) and Lemmon's willow (Salix lemonii Bebb) growing in a streamside location in the northern Sierra Nevada over a 2 year period. Standing biomass of both species and leaf area index of Lemmon's willow was also determined. Rooting activity of Nebraska sedge was measured the second year of the study. Measurements were taken during 1988 and 1989 with growing season precipitation 46% and 110% of average, respectively. Photosynthesis was remarkably similar for the 2 species (10.9 and 11.1 micromoles m-2 second-1 for Nebraska sedge and Lemmon's willow, respectively) when averaged over all dates for the 2 years. However, the 2 species exhibited different seasonal and yearly patterns of photosynthesis. Nebraska sedge maintained higher rates of photosynthesis during the early portion of the growing season and Lemmon's willow had higher photosynthesis during mid to late summer. Mean seasonal rates of willow photosynthesis were higher than those of the sedge during the drought year, and the opposite was true during the average year. Yearly average photosynthesis varied more for the sedge than for the willow. However, mean seasonal photosynthesis rates for each species were higher in an average year compared to a drought year. Nebraska sedge almost always had more negative values of xylem water potential than Lemmon's willow (overall average was -2.6 MPa and -1.25 MPa for Nebraska sedge and Lemmon's willow, respectively). Trends in transpiration and conductance were similar among species, except that Nebraska sedge maintained higher rates than Lemmon's willow during the spring of 1989. Willow biomass was similar among years, but willow leaf area index and sedge biomass were slightly greater in the wet year (1989) compared to the dry year. Contrasting growth forms and morphology of the 2 species may help explain differences in gas exchange and xylem water potential. The ability of willows to tap groundwater and the concentration of sedge roots in the upper soil profile probably accounts for the differential response to drought.
    • Gas exchange of Idaho fescue in response to defoliation and grazing history

      Doescher, P. S.; Svejcar, T. J.; Jaindl, R. G. (Society for Range Management, 1997-05-01)
      We tested the hypothesis that prior grazing history would influence the defoliation responses of Idaho fescue (Festuca idahoensis) growing in a common garden environment. Plants were taken from a grazed pasture and adjacent exclosure which had not been grazed since 1937, and established in a common garden at 1 m spacings during spring of 1989. Plants from defoliated and nondefoliated treatments within the 2 populations were sampled during 1992 and 1993. Photosynthesis, conductance to H2O, and xylem potentials were measured during the 2 growing seasons, and carbon isotope ratio (delta 13C) was measured for senescent leaf tissue. Both within exclosure and outside exclosure defoliated plants exhibited compensatory photosynthesis that averaged a 12% increase the first year, and a 52% increase during the second year, compared with nondefoliated plants. No differences in photosynthesis occurred between the 2 collections. However, outside exclosure plants had higher stomatal conductance than did exclosure plants for the dry year 1992. Also, outside exclosure plants exhibited more negative delta 13C (thus lower water use efficiency) than exclosure plants for 1992 and 1993. We suggest that the higher conductance of previously-grazed plants relative to nongrazed plant populations may be an adaptive response to greater soil moisture often found in grazed sites.
    • Gems of Oklahoma: 2013 SRM Meeting Technical Tours

      Ketch, Joshua; Gourley, Blayr (Society for Range Management, 2012-12-01)
    • Genecology and Seed Zones for Indian Ricegrass Collected in the Southwestern United States

      Johnson, R. C.; Cashman, M. J.; Vance-Borland, K. (Society for Range Management, 2012-09-01)
      Indian ricegrass (Achnatherum hymenoides [Roemer J.A. Schultes] Barkworth) is a widely distributed, highly desirable native species in desert ecosystems in the western United States. Yet there are no studies linking genetic variation in Indian ricegrass with climate across major areas of its natural distribution. In this study, seeds from 106 collection locations from the southwestern United States were established in common gardens and four phenological traits (Phen; such as blooming date), six production traits (Pro; such as dry weight), and eight morphology traits (Morph; such as leaf dimensions) were measured in 2007 and 2008. Analyses of variance revealed that all basic garden traits differed among source locations (P<0.01), indicating widespread genetic variation. Within Phen, Pro, and Morph categories, canonical correlation was completed between basic garden traits and source location temperature and precipitation. This resulted in six significant (P<0.01) canonical variates (Phen 1, Pro 1 and 2, and Morph 1, 2, and 3) representing each category of traits. Linear correlations (r> +/- 0.25, P<0.01)consistently linked monthly temperature at collection locations with Phen 1, Pro 1, and Morph 1. For precipitation, however, correlations were more dependent on month, with the strongest correlations during the spring developmental period. Using regression models between traits and climate, a map with 12 seed zones was developed representing much of the southwestern United States. This generally distinguished genetic variation between cooler and warmer regions, usually separating more northern, higher elevation areas from more southern, lower elevation areas. The correspondence between climate and genetic variation suggested climate-driven differences in natural selection, likely leading to adaptation. The seed zone map is recommended to guide and broaden germplasm collection and utilization for Indian ricegrass restoration./Indian ricegrass (Achnatherum hymenoides [Roemer & J.A. Schultes] Barkworth) presenta una amplia distribución, es una especie altamente deseable en los ecosistemas desérticos en el oeste de los estados Unidos. Sin embargo, áun no hay ning ún estudio que relacione las variaciones genéticas de Indian ricegrass con el clima a través de las áreas de su distribución natural. Eneste estudio, semillas de 106 localidades del suroeste de Estados Unidos fueron colectadas y establecidas en jardines comunes ycon cuatro características fenológicas (Phen; como día de floración), seis características productivas (Pro; como peso seco), yocho características morfológicas (Morph; como dimensión de la hoja) fueron medidas en 2007 and 2008. Análisis de varianza revelaron que todas las características básicas fueron diferentes entre las localidades de origen (P<0.01), indicando una amplia variación genética. Dentro de las categorías Phen, Pro, y Morph una correlación crónica fue completada entre las características básicas de jardín y fuente de origen, temperatura y precipitación. Esto resultó en seis variables crónicas significativas (P<0.01; Phen 1, Pro 1 and 2, and Morph 1, 2, and 3) representando cada categoría de las características. Correlaciones lineales (r> +/- 0.25, P<0.01) unieron consistentemente cada mes con la temperatura en cada colección y locación con Phen 1, Pro 1,and Morph 1. Para precipitación, sin embargo, las correlaciones fueron más dependientes de la variable mes, con las relacion es más fuerte en el periodo de desarrollo de primavera. Usando los modelos de regresión entre las características climáticas un mapa con 12 zonas de colección de semillas fue desarrollado representando la mayor parte del suroeste de Estados Unidos. Este mapa en general distinguió la variación genética entre las regiones más frías y las más cálidas, separando las localizadas más hacia el norte, con elevaciones más altas de las áreas mas hacia el sur con elevaciones más bajas. La correspondencia entre lavariación genética y climática sugiere que el clima conduce a diferencias en selección natural, probablemente llevando a la adaptación. El mapa con las zonas de semillas se recomienda para guiar y ampliar la recolección de germoplasma y su utilización para la restauración de Indian ricegrass.
    • Genetic aspects of diet selection in the Chihuahuan desert

      Winder, J. A.; Walker, D. A.; Bailey, C. C. (Society for Range Management, 1995-11-01)
      Fecal microhistology and chemistry were used to evaluate botanical composition and quality of diets selected by Brangus cattle grazing Chihuahuan desert range in 3 seasons; fall: October, 1991; winter: January, 1992; and summer: July, 1992. Fecal samples were collected from 100 head in fall (58 2-8 year cows and 42 calves), 53 head (2-8 year-old cows) in winter, and 44 head (2-8 year-old cows) in summer. Paternal half sib analyses were used to estimate genetic and phenotypic variances and heritability estimates. Heritability is the proportion of total (phenotypic) variation which is due to additive genetic effects. The effect of sire within age was observed for percentage of Aristida spp. (P= 0.01), Sporobolus spp. (P= 0.09), total grasses (P = 0.02), Croton pottsii (Klotzsch) Muell.-Arg. (P= 0.03), and total forbs (P =0.02) in fall diets. The number of grass species in diets was also affected by sire (P=0.03). Heritability estimates were 0.87, 0.51, 0.78, 0.76, and 0.79 for percentages of Aristida spp., Sporobolus spp., total grasses, Croton pottsii, and total forbs, respectively. Heritability estimates for number of grass and forb species in fall diets were 0.68 and 0.26, respectively. Heritability estimates for winter samples were 0.40, 0.00, 0.37, and 0.27 for percentages of Sporobolus spp., total grasses, Yucca elata Engelm., and total shrubs, respectively. Heritability estimates for the number of grass and total species observed in winter diets were 1.11 and 0.47, respectively. Heritability estimates for percentages of Bouteloua spp., total grasses, Croton pottsii, Dalea spp., and total forbs in summer samples were 0.20, 0.55, 0.58, and 0.46, respectively. Heritability estimates for the number of grass and total species in summer diets were 0.49 and 0.79, respectively. These data suggest that genetic composition of beef cattle may affect diet selection under Chihuahuan desert conditions.
    • Genetic Differences in Resistance of Range Grasses to the Bluegrass Billbug, Sphenophorus Parvulus (Coleoptera: Curculionidae)

      Asay, K. H.; Hansen, J. D.; Haws, B. A.; Currie, P. O. (Society for Range Management, 1983-11-01)
      Significant differences in plant resistance to larvae of the bluegrass billbug, Sphenophorus parvulus Gyllenhal (Coleoptera: Curculionidae), were found among and within range grass species and interspecific hybrids in nurseries at the Decker, Mont., surface mine and on a site near Miles City, Mont. Slender wheatgrass (Elymus trachycaulus) and related species were particularly susceptible. Crested wheatgrass (Agropyron cristatum and A. desertorum), thickspike wheatgrass (E. lanceolatus), Russian wildrye (Psathyrostachys juncea), and salina wildrye (Leymus salinae) were among the species with a relatively high degree of resistance to the insect. Clonal lines of the Et. repens × Et. spicata hybrid differed significantly in resistance. Over 50% of the total phenotypic variation among the hybrid lines was attributed to genetic effects, indicating that selection for resistance would be effective.
    • Genetic Improvement and Diversity in Snake River Wheatgrass (Elymus wawawaiensis) (Poaceae: Triticeae)

      Jensen, Kevin B.; Mott, Ivan W.; Robins, Joseph G.; Waldron, Blair L.; Nelson, Mark (Society for Range Management, 2012-01-01)
      With the increased emphasis on using native plant materials in range revegetation programs in the western United States it is critical to identify genetically similar groups and develop native grasses that are competitive with invasive weeds, easy to establish, and persistent, and that produce high seed yield. A grass that shows appreciable drought tolerance on arid rangelands is Snake River wheatgrass (Elymus wawawaiensis J. Carlson Barkworth). This study was designed to estimate genetic relationships and underlying genetic components for seed and forage trait improvement between plant introductions (PIs) of Snake River wheatgrass, 28 half-sib Snake River wheatgrass families (HSFs), and cultivars Secar and Discovery at Nephi, Utah, between 2005 and 2006. Based on molecular genetic diversity data in Snake River wheatgrass, with the exception of the Pis originating from Enterprise, Oregon, all other collections and cultivars are not genetically different and represent a common gene pool from which to develop improved Snake River wheatgrass germplasm. Selection in Snake River wheatgrass for total seed yield (g plot-1), 100-seed weight (g), and seedling emergence from a deep planting depth had a positive effect. Further increases through selection and genetic introgression from hybridization with PIs will likely increase seed yield and 100-seed weight, but will not increase seedling emergence. Increases in dry matter yield (DMY) were observed after two cycles of selection in the HSFs compared to the Pis. There remains considerable genetic and phenotypic variation to further increase DMY in Snake River wheatgrass through selection and hybridization. Trends in forage nutritional quality were not observed after two cycles of selection in the HSFs or the PIs and will not likely result in improvement. Through recurrent selection, populations of Snake River wheatgrass have been and can be developed to more effectively establish and compete on annual weed-infested rangelands./Con el aumento en el interés de usar plantas nativas para los programas de revegetación en el oeste de los Estados Unidos es necesario identificar grupos genéticamente similares y desarrollar pastos nativos que sean competitivos con plantas invasoras, fácil de establecerse, persistentes y con alto rendimiento en producción de semilla. El pasto que muestra buena tolerancia a la sequia en pastizales áridos es el Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkworth). Este estudio fue diseñado para estimar la relación genética y subrayar los componentes genéticos para el rasgo de mejoramiento de la semilla y el forraje entre introducción de plantas (PIs) de Snake River wheatgrass, 28 medio hermanas familias de Snake River wheatgrass (HSFs) y de cultivos de Secar y Discovery en Nephi, Utah, entre los años 2005 y 2006. Basados en datos de diversidad genética molecular del pasto Snake River wheatgrass con excepción del PIs originario de Enterprise, Oregon, todas las demás colecciones y cultivos no son genéticamente diferentes y representan un grupo con un gen común del cual se desarrollo el germoplasma mejorado del Snake River wheatgrass. La selección del Snake River wheatgrass por rendimiento total de semilla (g parecela-1), peso de semilla (g) y emergencia de plántulas de una profundidad de plantación profunda tuvo efecto positivo. Aunado al incremento a través de selección y introgresion genética de hibridación con PIs podría incrementar el rendimiento de semilla y el peso de 100 semillas pero no aumentar la emergencia de plántulas. El incremento en rendimiento de materia seca (RMS) fue observado después de 2 ciclos de selección en el HSFs comparado con el PIs. Ahí queda considerable variación genética y fenotípica para futuro incremento en rendimiento de materia seca (RMS) en Snake River wheatgrass a través de selección e hibridación. Tendencias en la calidad nutricional del forraje no se observaron después de 2 ciclos de selección en el HSFs ni en el PIs y no es probable que resulte en mejoramiento. A través de selección recurrente de poblaciones de Snake River wheatgrass han sido y pueden ser desarrolladas para establecerse con mayor efectividad y competir con hierbas anuales en pastizales infestados.
    • Genetic Progress Through Hybridization of Induced and Natural Tetraploids in Crested Wheatgrass

      Asay, K. H.; Dewey, D. R.; Gomm, F. B.; Horton, W. H.; Jensen, K. B. (Society for Range Management, 1986-05-01)
      Because of restrictions imposed by crossing barriers, crested wheatgrass breeders have usually limited themselves to selection and hybridization within ploidy levels i.e., diploid (2n=14), tetraploid (2n=28), or hexaploid (2n=42) populations. Several procedures have now been devised and evaluated to transfer genetic traits among ploidy levels, and interploidy breeding appears to be a feasible approach in the crested wheatgrass complex. Plant scientists with the USDA-ARS at Utah State University have developed a superior breeding population by hybridizing induced tetraploid Agropyron cristatum (L.) Gaertn. with natural tetraploid A. desertorum (Fisch. ex Link) Schult. The cultivar 'Hycrest' was released from this germplasm base in 1984. Chromosome number of the Hycrest breeding population ranged from 2n=28 to 32 and averaged 30. Chromosome pairing relationships were similar to those observed in natural tetraploids and the cultivar was as fertile as the parental species. Hycrest produced significantly more seeds per spike than 'Nordan,' and ample genetic variability for seed set existed in the population to make additional improvement through selection. Hycrest produced significantly (P<0.05) more forage than Nordan and Fairway in 9 of 12 comparisons at 5 semiarid range sites. The superiority of the cultivar was most noteworthy during and immediately after stand establishment on harsh sites. The need to expand the genetic base of the present population with selected parental materials is recognized.
    • Genetic Variability for Characters Affecting Stand Establishment in Crested Wheatgrass

      Asay, K. H.; Johnson, D. A. (Society for Range Management, 1983-11-01)
      Experiments were conducted in the laboratory (growth chamber) and field to determine the: (1) magnitude of genetic differences in crested wheatgrass [Agropyron cristatum (L.) Gaertn. and A. desertorum (Fisch. ex Link) Schult.] for characteristics related to seedling establishment on semiarid range and (2) effectiveness of laboratory procedures to estimate relative performance of breeding lines in the field. Significant differences were found among 175 crested wheatgrass progeny lines for seedling emergence, seedling height, seedling dry weight, and fall stand in the analyses of data combined over 2 field locations. The soil at both study sites was a Xerallic Calciorthids. The genetic variance among progenies comprised over 50% of the total phenotypic variance for most traits in the combined analyses of variance. Seedling emergence in the spring was positively related to fall stands (r = 0.54** to 0.61**). In growth chamber experiments involving 168 progeny lines, significant genetic variation was detected in seedling recovery after exposure to drought stress in 3 of 4 experiments. The genetic variance comprised over 50% of the total phenotypic variance in 5 of 6 instances in the combined analyses of the field data and in 3 of the 4 laboratory experiments. In general, laboratory determinations of seedling emergence under drought stress and seedling recovery after drought were not significantly related to seedling establishment in the field. A relatively close correlation between seed weight and all plant responses measured in the field (r = 0.46** to 0.57** in the pooled data) suggests that preliminary screening on the basis of seed weight appears promising.
    • Genetic variability for elements associated with grass tetany in Russian wildrye

      Asay, K. H.; Mayland, H. F. (Society for Range Management, 1990-09-01)
      Grass tetany (hypomagnesemia) may be an important factor limiting productivity of animals grazing Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]. This malady is associated with relatively low concentrations in the forage of Mg and Ca, and high values for K and K/(Ca+Mg). We studied the genetic variability in a Russian wildrye breeding population for mineral elements that relate to grass tetany in ruminants. Forty-five progeny lines, estblished as spaced plants in a randomized complete block, were sampled at the pre-boot and boot stages in each of 2 years and analyzed for Mg, Ca, K, and P. Although seasonal variation was evident, K/(Ca+Mg) of the progeny lines ranged from 3.2 to 4.6, well above the 2.2 level at which a 5% incidence of grass tetany has been found in dairy cattle. With few exceptions, progenies differed for all traits evaluated. Differences among progenies were relatively consistent over harvests for all traits. A reduced tetany potential (RTP) was computed as the sum of normalized Mg and reciprocal of K/(Ca+Mg) values, providing an estimate of the grass tetany risk for individual progeny lines. The variation among progenies, and the magnitute of broad-sense heritability estimates for RTP (0.48) and K/(Ca+Mg) values (0.31), indicate that mineral ion composition of this breeding population can be altered through breeding. The high K/(Ca+Mg) values in the population suggest that it may be helpful to introduce genetic factors conditioning lower grass tetany potential from other sources. Intercharacter correlations suggest that breeding for higher levels of Mg will be accompanied by increased Ca and, to a lesser extent, increased K.
    • Genetic variability of Mg, Ca, and K in crested wheatgrass

      Mayland, H. F.; Asay, K. H. (Society for Range Management, 1989-03-01)
      Increasing available Mg in crested wheatgrass (Agropyron spp.) could reduce the incidence of grass tetany (hypomagnesemia) in ruminants grazing this forage. Raising the Mg levels might be done through genetic processes if enough variation in ion concentration existed in the Agropyrons. The purpose of this study was to determine the genetic variation in Mg, Ca, and K concentrations in 2 crested wheatgrass populations. Parent plants were vegetatively propagated to provide 6 replicates each of 12 clones of crested wheatgrass (A. desertorum) and 16 F3 clones of colchicine-induced tetraploid A. cristatum X natural tetraploid A. desertorum. Each plant was selected on a basis of seedling and mature plant vigor, forage, and seed yield, leafiness, resistance to pests, and response to environmental stress. The 2 populations were grown in separate, space-planted nurseries at Logan, Utah. Herbage was harvested at the pre-boot and early flowering stage in each of 2 years. Magnesium and Ca were determined by atomic absorption and K by flame emission. A reduced tetany potential (RTP) index for each clone was calculated as the sum of normalized Mg and (Ca+Mg)/K values. Significant (P < 0.01) differences for all traits were detected among clones in each population. All traits, except K and RTP, were closely correlated. Broad-sense heritability values for most traits ranged from 0.61 to 0.84. Enough genotypic variation existed in both populations to warrant breeding lines with higher concentrations of Mg and larger RTP values. Such changes could reduce the incidence of grass tetany in livestock grazing crested wheatgrass.
    • Genetic variances for dry matter yield, nitrogen content, and nitrogen yield in crested wheatgrass-alfalfa mixtures

      Asay, K. H.; Mayland, H. F. (Society for Range Management, 1991-09-01)
      Since its introduction from Asia in the early 1900s, crested wheatgrass [Agropyron cristatum (L.)Gaertner, A. desertorum (Fisch. ex Link) Schultes et al.] has had a major impact on the improvement of western rangelands of North America. Most of the early seedings with this cool-season grass were made as monocultures. Present and projected use of rangelands, however, prescribe that future crested wheatgrass cultivars have the genetic potential to be an effective component in a species complex including other grasses, shrubs, and forbs. The present study was conducted to evaluate the effect of associated alfalfa (Medicago sativa L.) on the performance and genetic variability in a 50-clone sample of a tetraploid crested wheatgrass breeding population. Significant (P < 0.05) differences were found among the clonal lines for dry matter (DM) yield, nitrogen (N), and N yield. Opportunities for genetic improvement, as indicated by the magnitude of the genetic variation for these characters, was significantly increased when the grasses were grown in association with alfalfa. Significant (P < 0.01) and positive correlations of clonal means between stand types indicated that differences among the clonal lines in DM yield, N content, and N yield were relatively consistent when grown with or without alfalfa. These results indicate that initial screening could be effectively done in tetraploid crested wheatgrass in the presence or absence of alfalfa. Final evaluation of breeding lines and experimental strains, however, should be done with alfalfa if the object is to develop cultivars to be grown in combination with that species.
    • Genetic variation and inheritance characteristics for carbon isotope discrimination in alfalfa

      Johnson, D. A.; Rumbaugh, M. D. (Society for Range Management, 1995-03-01)
      The negative correlation between carbon isotope discrimination and water-use efficiency in C3 species, including alfalfa (Medicago sativa L.), suggests that carbon isotope discrimination that might be useful in the selection of alfalfa cultivars that use water more efficiently. We initiated field experiments with alfalfa in northern Utah to determine genetic variation for carbon isotope discrimination within representative breeding populations, the effect of drought on carbon isotope discrimination, magnitudes of heritability for carbon isotope discimination, genetic regulation of carbon isotope discrimination, and how carbon isotope discrimination differs among plant parts. In an experiment conducted under a rainout shelter facility equipped with a line-source sprinkler system, genetic variability for carbon isotope discrimination was not detected in 15 clones each from the NC-83-1 germplasm and 'Spredor 2' cultivar. In another experiment with 25 clones from the NC-83-1 germplasm, there was significant (P < 0.01) genetic variation for carbon isotope discrimination with a range of 1.6 per thousand, and broad-sense heritabilities exceeded 0.80. In a field trial with 78 cultivars and elite breeding lines, significant genetic variation for carbon isotope discrimination was observed, although the range for carbon isotope discrimination was only 0.8 per thousand. We also detected significant genetic variation for carbon isotope discrimination in a diallel experiment with 196 crosses from 14 parent clones from NC-83-1. Furthermore, general combining ability was significant, but specific combining ability and reciprocal effects were not, indicating that standard breeding techniques could be used to alter carbon isotope discrimination response in alfalfa. Plant parts differed significantly for carbon isotope discrimination with stems having the lowest value (18.7 per thousand) followed by the entire shoot (19.0 per thousand), upper leaves (19.4 per thousand), and bottom leaves (20.2 per thouand). The lack of significant statistical interactions among plant parts suggested that any plant part could be sampled to determine carbon isotope discrimination. The results from these experiments indicated that promise exists for using carbon isotope discrimination to improve water-use efficiency in alfalfa; however, use of more diverse germplasm may be necessary to expand opportunities for selection in North American alfalfa germplasm.
    • Genotype and planting depth effects on seedling vigor in sericea lespedeza

      Qiu, J.; Mosjidis, J. A. (Society for Range Management, 1993-07-01)
      Sericea lespedeza [Lespedeza cuneata (Dumont de Courset) G. Don.] is a small-seeded forage legume that can improve forage quality and nitrogen content of interseeded pasturelands. Poor seedling vigor has caused interseeding failure. This study was conducted to determine the effects of genotype, planting depth, and their interaction on seeding vigor of services lespedeza in the field, and to determine if seedling traits measured in a growth chamber can be used to predict seedling growth in the field. Substantial variability was found among 54 sericea lespedeza genotypes for traits that can be used in a breeding program to improve seedling vigor. All seedling traits were correlated with each other, indicating a high proportionality existed among plant parts. Thus, any of the seedling traits measured could be used to represent seedling vigor. Genotypes 73-162-16, AU L2, AU L13, and 'Serala 76' outperformed other genotypes for most seedling traits under field and growth chamber conditions. Planting to a depth of 3 cm did not reduce seedling vigor, and therefore, may be recommended when there is insufficient moisture in the upper layer of sandy loam soils at planting. Although measurements taken in the growth chamber did not reliably predict field performance, information gathered in the growth chamber provides a good means of increasing the frequency of superior plants to be tested in the field.