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There is interest in Canada wildrye (CWR, Elymus canadensis L.) and Virginia wildrye (VWR, E. virginicus L.) for conservation and forage uses. Our objectives were to identify a set of molecular markers to assess genetic structure within and diversity among populations of CWR and VWR from the Southern Great Plains and to determine if these populations had an associated fungal endophyte. Nine CWR and five VWR populations and two barley (Hordeum vulgare L.) cultivars were genotyped using simple sequence repeat (SSR) markers isolated from tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] expressed sequence tags (TF ESTs). Scorable fragments were produced by 31% of TF EST-SSRs tested, thus identifying a set of SSR markers for wildrye. Populations grouped into three clusters consisting of (i) three wild populations, one plant introduction, and two commercial sources of CWR; (ii) all VWR populations and three CWR plant introductions; and (iii) barley cultivars. Clustering indicated possible gene flow between CWR and VWR. Genetic variation within populations was minimal and comparable to that of the barley cultivars. Thus, unlike many ancestral cultivars and landraces of self-pollinated crops, CWR and VWR populations consisted of essentially pure lines and can be handled as such in a breeding program. Potentially sexual and asexual epichloe endophytes were found in several populations, indicating the need to account for endophytes in breeding and germplasm conservation efforts of wildrye.

Little information is available on the genetic diversity of hardinggrass (Phalaris aquatica L.), a cool-season forage grass with potential for use in the southern Great Plains. The objective of this study was to determine the genetic diversity within and among 22 promising hardinggrass populations, including plant introductions (PIs), breeding populations, and one cultivar. Nine plants from each population (198 genotypes) were characterized with amplified fragment length polymorphism (AFLP) markers. Genotypes were evaluated with nine selective primer combinations of fluorescent-labeled PstI and MseI primers, producing a total of 961 useful AFLP fragments. A high degree of genetic diversity was found, with a greater proportion of the diversity within (74%) rather than among (26%) populations. Clustering of populations on the basis of UPGMA closely followed the geographic origin and breeding history of the populations. Selections led to genetic shifts between two breeding populations, HG PI C1 and HG PI C2, although genetic diversity changed little if at all within these populations on the basis of polymorphism information content (PIC) scores of 0.22 versus 0.19, respectively. Two Moroccan PIs (PI 240248 and PI 517026) represent a distinct germplasm source on the basis of their genetic distances from other populations in the study. Genetic diversity data from this study will be helpful in grouping these accessions for development of breeding populations and various research purposes., HARDINGGRASS, a cool-season perennial, is native to the Mediterranean region (Carlson et al., 1996). It is commonly used as pasture forage in Australia and was introduced to the USA from [...]

Improved grazing tolerance is often an important goal in grass breeding programs. The objective of this research was to compare grazing tolerance of several cool-season perennial grasses planted as seeded sward plots and spaced plants. Cultivars or populations of smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), wheatgrass species (Thinopyrum spp.; Pascopyrum smithii (Rydb.) A. Love), tall fescue (Festuca arundinacea Schreb.), and hardinggrass (Phalaris aquaticu L.), were evaluated at Burneyville and Ardmore, OK, for 2 and 4 yr, respectively, as seeded sward plots and spaced plants. Following establishment, plots were grazed heavily (average of 6400 kg live weight [ha.sup.-1]) by cattle (Bos spp.) during spring and summer. Grazing tolerance was estimated each fall using survival as well as recovery scores for spaced plants and stand for seeded sward plots. Genotype x environment (GXE) interactions were prevalent, with the Burneyville site being more stressful for grass growth. Within an environment, recovery scores and survival of spaced plants were very similar, with rank correlations exceeding 0.81 (P < 0.05). As plantings became older, entries responded more similarly to heavy grazing across planting arrangements, with rank correlations between stand and survival exceeding 0.70 (P < 0.01) in some cases. 'Barton' western wheatgrass and 'Painte' orchardgrass were consistently among the most and least grazing tolerant entries, respectively, regardless of planting arrangement. Thus, where seed supplies are limited, initial screening of accessions as spaced plants for 2 to 4 yr should allow breeders to identify cool-season grass germplasm that is potentially grazing tolerant. Subsequent evaluations in sward plots at multiple locations would be helpful in determining which populations to incorporate into a breeding program. Abbreviations: E+, endophyte infected; E-, endophyte free; GxE, genotype by environment; KY-31, 'Kentucky 31'; [r.sub.s], Spearman's rank correlation., GRAZING TOLERANCE, characterized by survival of plants exposed to heavy livestock grazing pressure across time, is often an important target trait in grass breeding programs. A variety of methods have [...]

Little information is available regarding genetic variation in tall rescue (Festuca arundinacea Schreb). Such information is important in constructing mapping populations and targeting germplasm collection and utilization. The objective of this study was to evaluate the genetic diversity among a number of tall rescue accessions, cultivars, and selected genotypes, in one experiment, 16 persistent tall rescue plants (genotypes) were assayed by a fluorescence-labeled amplified fragment length polymorphism (AFLP) detection method using DNA samples from individual plants. In a second experiment, AFLP diversity among 18 tall rescue populations, including sources of `KY-31', cultivars derived from KY-31 and accessions collected from Oklahoma and Texas, was assessed by an infrared dye-labeling method using DNA samples bulked by each population. On the basis of 461 AFLP markers from six primer combinations, the 16 individual plants were clustered in groups that largely supported the known origins of these plants. On the basis of genetic divergence, several candidate parents were identified for constructing a mapping population. Analysis of bulked DNA samples revealed that sources of KY-31 and cultivars derived from KY-31 generally clustered separately from accessions collected in the southern Great Plains. Such accessions thus provide an additional source of genetic variation for tall rescue breeding programs., TALL FESCUE, a major forage and turf grass species n the temperate regions of the world, is a hexaploid (2n = 6x = 42) with a genome size of ≅ [...]

Tolerance to acid soil would he a desirable trait for switchgrass (Panicum virgatum L.) cultivars that are to be grown across the southern Great Plains. The objectives of this research were to estimate genetic variation for, and examine the level of, acid soil tolerance at the seedling stage within two switchgrass populations. Seedlings of `Kanlow' and `Blackwell' were grown during 1993 and 1994 in acid soils (pH 3.9-5.0) in the greenhouse and harvested 7 to 8 wk after planting. Seedlings were allowed to regrow and planted in polycross field isolation where half-sib seed was produced. Progeny families were grown during 1995 and 1996 in acid soils (pH 4.4-5.1) in the greenhouse, and seedling shoot weight data collected 7 to 8 wk after planting. Heritability ([h.sup.2]) for weight of seedlings grown in acid soil was estimated by parent-progeny regression. Growth of half-sib families in a limed and non-limed acid soil was also examined. Estimates of [h.sup.2] were low or non -significant, ranging from 0.18 ± 0.08 to 0.06 ± 0.02 for Kanlow and 0.06 ± 0.02 for Blackwell. The low [h.sup.2] estimates, coupled with a lack of significant variation for seedling shoot weight among families grown in acid soil, indicate little or no genetic variation for acid soil tolerance among seedlings of Blackwell or Kanlow, Seedling weight of half-sib families grown in a soil limed to near-neutral pH was not significantly different from seedling weight of the identical families grown in an acidic soil. Thus, at the seedling stage Kanlow and Blackwell switchgrass appear to have substantial tolerance to acid soil., The occurence of acid soil (pH [is less than or equal to] 5.0) has become X widespread in the southern Great Plains (Johnson, 1986; Uhruh and Whitney, 1986), in association [...]

Information regarding ploidy level of switchgrass (Panicum virgatum L.) is needed for use of populations in breeding programs and for maintenance of germplasm. Our objectives were to determine chromosome number and variation in DNA content of several switchgrass populations and to examine the usefulness of flow cytometry techniques for estimating ploidy level in switchgrass. Chromosome numbers were determined by means of light microscopy; laser flow cytometry was used to determine nuclear DNA content. Only octaploid plants were found within 'Blackwell', 'Pathfinder', 'Cave-in-Rock', and 'Trailblazer', all of which were previously reported to be hexaploid populations. Average nuclear DNA contents, with ranges in parentheses, were 3.1 (2.7-3.2) pg for verified tetraploid populations and 5.2 (4.8-5.8) pg for verified octaploid populations. Flow cytometry techniques were useful in discriminating between 4x and 8x plants; ploidy level of plants estimated to be 6x may need to be verified with actual chromosome counts.

Switchgrass (Panicum virgatum L.) is used as a forage species and has shown potential for use in production of fuel ethanol from cellulosic biomass. Objectives of this research were to determine performance differences between elite switchgrass populations for agronomic, forage quality, and biofuel traits and to determine the magnitude of genotype X environment (G X E) interactions for these traits across mid-western environments. Twenty elite switchgrass populations, consisting of cultivars and advanced breeding populations, were planted in sward trials at Mead, NE, Ames, IA, and West Lafayette, IN, during 1990 and were evaluated in 1991 and 1992. Forage samples were taken at a vegetative growth stage, at heading, and at the end of the season. Plots were harvested for forage yield at heading and at the end of the growing season. Forage composition and in vitro dry matter digestibility was determined using near infrared reflectance spectroscopy. Significant differences (P < 0.05) between populations for forage yield were found at individual locations but not across locations, except at the P = 0.10 probability level, because of G X E interactions. Genotype X environment interactions were significant for hemicellulose plus cellulose (holocellulose) yield, a potentially important biofuel trait. In vitro dry matter digestibility was more stable than both forage yield and holocellulose yield. Despite large G X E interaction effects, a few populations consistently ranked high in forage yield and holocellulose yield. Multiple location, multiple year sward trials will be needed to develop switchgrasses broadly adapted to the midwest.

Improved forage yield and quality, which can lead to more efficient livestock production, are important goals in switchgrass (Panicum virgatum L.) breeding. Objectives of this study were to determine the effectiveness of multiple cycles of recurrent restricted phenotypic selection (RRPS) in improving forage yield in switchgrass and in improving in vitro dry matter digestibility (IVDMD), and to compare predicted and realized gains from selection. Six switchgrass populations were developed by selecting a base population for one cycle of low and three cycles of high IVDMD and two cycles for high yield. Half-sib progenies of parents selected from the base population for high and low IVDMD were used to estimate heritability for IVDMD by parent-progeny regression. Realized gains from selection were determined in a seeded sward trial that included the base and six selected populations. Estimated and realized heritabilities for IVDMD were 0.40 and 0.31, respectively. Predicted pins and (in parenthesis) realized gains from selection for I'MD in grams per kilogram per cycle were - 21 (- 15) for the Low IVDMD Cycle 1, 16 (15) for the High IVDMD Cycle 1 (|Trailblazer'), 14 (4) for the High IVDMD Cycle 2, and 19 (18) for the High IVDMD Cycle 3 populations. There was a low but positive genetic correlation between forage yield and RVDMD of 0.10. Forage yield was not improved by RRPS, probably because of lack of genetic variability for forage yield in the base population. It is concluded that RRPS is effective for improving I'MD in switchgrass, but was not effective in improving forage yield in the populations evaluated, and that predicted gains exceeded realized gains from selection for IVDMD due to limited selection for traits other than IVDMD.

Determines the genetic diversity of Festuca arundinacea Schreb in Great Plains. Use of amplified fragment length polymorphism detection method; Source of genetic variation of tall fescue; Genomic constitution of the turfgrass.