Published in Crop Sci. 43:1852-1857 (2003).
© 2003 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
PLANT GENETIC RESOURCES
RAPD Variations in Selected and Unselected Blue Grama Populations
Anh T. Phan*,a,
Yong-Bi Fub and
S. Ray Smith, Jr.c
a Native Plant Solutions, Ducks Unlimited Canada, 1255 Clarence Avenue, Winnipeg, MB, R3T 1T4, Canada
b Plant Gene Resources of Canada, Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK, S7N 0X2, Canada
c Dep. of Crop & Soil Environment, Virginia Tech, Blacksburg, VA 24061, USA
* Corresponding author (raysmith{at}vt.edu).
 |
ABSTRACT
|
|---|
Blue grama (Bouteloua gracilis H.B.K. Lag. ex Steud.) is one of the most widespread native grasses in western North America. Little is known about the genetic diversity of this species and the genetic shift in selected populations. Random amplified polymorphic DNA (RAPD) markers were used to assess the genetic variations of blue grama plants in 11 natural source populations (SPs) in southern Manitoba and two selected populations. Population ‘BMSC’ was a balanced multisite composite of 99 clones selected for higher seed yield from the 11 SPs. Population ‘MSC’ was a mass-selected composite of 25 clones with higher seed yield from eight SPs. Twelve RAPD primers were used to assay 108 original propagules from the 11 SPs and 96 seedlings from each selected population. A total of 69 polymorphic RAPD bands were detected. No unique RAPD bands were found for any SPs and 97.8% of the total RAPD variation was detected within SPs. Variation in RAPD markers was not associated with geographical distances. Highly significant changes in RAPD band frequency from their SPs were detected in both selected populations, but only MSC displayed the fixation of polymorphic bands. The estimated genetic shifts were small, 0.6% for BMSC and 1.9% for MSC.
Abbreviations: AMOVA, analysis of molecular variance • AS, apparently selective • NTSYS, numerical taxonomy and multivariate analysis system • PCR, polymerase chain reaction • RAPD, random amplified polymorphic DNA • SP, source population • UBC, University of British Columbia • UPGMA, unweighted paired group method of arithmetic averages
|
INTRODUCTION
|
|---|
NATIVE PLANT SPECIES have gained renewed interest in research and plant breeding programs in recent years. Particular interest includes the uses of these species for soil stabilization (Cooper, 1957), mine site reclamation (Gaffney and Dickerson, 1987), wildlife habitat restoration (Duebbert et al., 1981), and development of high-quality forage (Vogel and Pedersen, 1993). One of the major limitations to the use of native plant species is the lack of commercial seed quantities. Efforts to develop cultivars with improved seed production have increased in USA and Canada (Crowle, 1970; Smoliak and Johnson, 1980; Smoliak and Johnson, 1983; Jones et al., 1991). However, the developed cultivars may not maintain sufficiently high levels of genetic diversity necessary for habitat revegetation and ecological restoration (Knapp and Rice, 1996; Roundy, 1999; Larson et al., 2000). Thus, more attention has been paid to the development of cultivars having both improved seed production and high genetic diversity for adaptation in different environments (May et al., 1997; Jones et al., 2002; Smith and Whalley, 2002).
Blue grama is a warm-season, highly outcrossing perennial grass (Riegel, 1941; Miller, 1967) that inhabits a wide ecological range in North America where it is used for reclamation and ground cover (Hitchcock, 1950). These adaptive features have stimulated some interest in utilization and cultivar development of this species (Smith and Phan, 1999). Two blue grama populations, one a balanced multi-site composite (BMSC) and the other a mass-selected composite (MSC), originated from 11 natural source populations (SPs) in southern Manitoba (Phan, 2000). Populations BMSC and MSC were selected for increased seed yield (Phan and Smith, 2000).
Studies that compare genetic diversity and shift between the selected and source populations are lacking. Genetic shifts attributed to selection have been reported in morphological studies of oat (Avena sativa L.) (Rodgers et al., 1983), maize (Zea mays L.) (Coors and Mardones, 1989; Helms et al., 1989; Stojsin and Kannenberg, 1994), and Pensacola bahiagrass (Paspalum notatum Flugge var. saurae Parodi) (Werner and Burton, 1991; Pedreira and Brown, 1996).
The objective of this study was to characterize the genetic diversity of blue grama plants in 11 natural SPs and two selected populations by means of the RAPD technique (Williams et al., 1990). This technique has been used to detect genetic variations in several grass species, including buffalograss [Buchlöe dactyloides (Nutt.) Engelm.] (Huff et al., 1993; Peakall et al., 1995), switchgrass (Panicum virgatum L.) (Gunter et al., 1996), perennial ryegrass (Lolium perenne L.) (Huff, 1997), little bluestem [Schizachyrium scoparium (Michx.) Nash] (Huff et al., 1998), smooth bromegrass (Bromus inermis Leyss.) and meadow bromegrass (B. riparius Rehmann) (Ferdinandez, 1999).
|
MATERIALS AND METHODS
|
|---|
Plant Materials
A total of 495 blue grama plants were collected from 11 natural populations in southern Manitoba (Table 1) and transplanted into a field nursery at Winnipeg (Phan and Smith, 2000). Population BMSC was a balanced multisite composite of 99 clones selected for higher seed yield from the 11 SPs and population MSC was a mass-selected composite of 25 clones with higher seed yield from eight SPs (Phan and Smith, 2000). Population MSC was not equally represented by each of the original collections. Seeds used for this study of the selected populations were harvested from selected clones after one generation of open-pollination in an isolated polycross nursery.
View this table:
[in this window]
[in a new window]
|
Table 1. RAPD variation patterns of blue grama plants collected from 11 natural source populations (SPs) in southern Manitoba, Canada.
|
|
For the RAPD assay, a random sample of seed for each selected population was germinated on filter paper in Petri dishes moistened with 0.5% (w/v) KCl solution, and put under a 16-h/8-h day-night photoperiod at 25°C, and their seedlings were transplanted into individual pots in a greenhouse. Young leaf tissue was collected from 96 individual plants for each selected population. Young propagule leaves of 108 original tillers from the 11 SPs were individually collected (8 to 12 tillers/SP; Table 1). Collected leaves were stored at -80°C and freeze-dried with a Labconco Freeze Dry system (Kansas City, MO, USA) for 3 to 5 d.
DNA Extraction and RAPD Analysis
DNA was extracted from 50 mg of lyophilized leaf tissue from each of the 300 samples. The dry leaves were clipped as finely as possible into 2-mL Eppendorf tubes, 4 to 5 glass beads were added, and the tubes were mechanically shaken for 30 min to produce a fine powder. Each tube was filled with 600 µL of hot (95°C) extraction buffer [2 M Tris-HCl (pH 8.0), 3 M KCl, 0.5 M EDTA (pH 8.0), 14% (w/v) SDS] and then incubated at 95°C for 15 min with occasional agitation. The homogenate was centrifuged to remove cell debris. The supernatant was treated with RNase and DNA was precipitated with isopropanol. The DNA was suspended in 100 µL of water, then quantified by fluorimetry using Hoechst 33258 stain (Sigma Chemical Co., St. Louis, MO, USA) and diluted to 2.5 ng µL-1 for polymerase chain reaction (PCR).
Each PCR reaction utilized 10 ng template DNA, 1 U of Taq DNA polymerase (BRL, Mississauga, Canada), 2.5 mM MgCl2, 200 µM of each dNTP and 0.2 µM decamer primer [University of British Columbia (UBC), Vancouver, Canada]. The DNA amplification protocol was one cycle of 1.5 min at 95°C; 35 cycles of 20 s at 95°C, 60 s at 36°C, and 1 min at 72°C (ramp 1°C/s); and a final cycle of 7 min at 72°C. All PCR products were separated by electrophoresis in 2% (w/v) agarose gels in 1x TAE ran at 100 V for 3 h. Gels were then stained with 70 µL ethidium bromide diluted in 700 mL water and photographed on a digital gel-documentation system (Stratagene, La Jolla, CA, USA).
Screening of informative RAPD primers was made on eight individual samples randomly selected from the SPs. Eighty-nine UBC primers were initially screened and 12 informative primers (see Table 2) were then selected for this study. Testing RAPD reproducibility was also made using six of the 12 selected primers on 12 other plants randomly selected from the SPs. DNA extraction of these 12 plants was made twice as described above, followed by PCR reaction and electrophoresis. Pairwise comparisons of the resulting RAPD profiles were made.
View this table:
[in this window]
[in a new window]
|
Table 2. RAPD variation patterns for each primer in blue grama plants of two selected populations (BMSC and MSC) and their source populations (SPs).
|
|
Data Analysis
For each sample assayed, RAPD bands were scored as 1 (dominant band) or 0 (absent band). RAPD polymorphism was first analyzed with respect to primer and population. Polymorphic dominant bands were counted and their frequencies in each SP and selected population were calculated.
To assess the RAPD variation of blue grama in the 11 SPs, average polymorphic band frequency was calculated for each population. Mean RAPD variation within a population were estimated following the method of Nienhuis et al. (1994) and from the sums of squares of Analysis of Molecular Variance (AMOVA; Excoffier et al., 1992). For each population, RAPD similarity between a pair of individual plants was first calculated using NTSYS-pc (Rohlf, 1997) with simple matching coefficients (Sokal and Michener, 1958). The resulting similarity matrix was then inverted into a Euclidean distance matrix. AMOVA was performed on all the Euclidean distance matrices generated from the 11 SPs and the total RAPD variation was partitioned into between- and within-population components. Significance of each component was tested with 2000 permutations. The proportion of variation partitioned between populations from AMOVA was used as a measure of interpopulation distance (phi-statistic) following Huff et al. (1993) and Huff (1997). These interpopulation distances were also used to assess the genetic relationships of the 11 SPs by NTSYS-pc with Unweighted Paired Group Method of arithmetic Averages (UPGMA) clustering and to test the association with their geographical distances by MXCOMP program of NTSYS-pc with 2000 permutations.
To assess genetic shift in the selected populations, RAPD variation between SPs and each selected population were compared. For each selected population, the numbers of polymorphic bands were plotted with respect to their band frequencies and the polymorphic bands showing reduction in band frequency from the SPs were identified. Significance of band frequency changes from the SPs was examined with a contingency Chi-square test for each polymorphic band. Heterogeneity Chi-square test was performed on all the bands to assess the significance of the difference in RAPD variation from the SPs. To quantify the genetic shift, two distance measures were applied, pairwise distances calculated, and their significances away from zero tested. First, the interpopulation genetic distance between SPs and a selected population was estimated from AMOVA as described above and tested for its significance with 2000 permutations. A cluster analysis of the resulting interpopulation distances was also made by NTSYS-pc with UPGMA clustering to assess the genetic relationships of each selected population with the SPs. Second, the Mahalanobis squared distance was calculated from a canonical discriminant analysis of the original RAPD data and tested for its significance with F-tests using CANDISC procedure of SAS program (SAS Institute, 1996).
|
RESULTS AND DISCUSSION
|
|---|
RAPD Polymorphism
Most of the 89 UBC primers initially screened (67%) displayed RAPD profiles with polymorphic bands, but many of these bands varied with thickness, molecular weight, and intensity. This variation made the scoring of RAPD bands difficult and less reliable. Thus, only the robust RAPD bands were considered in this study. Testing the reproducibility of some robust RAPD bands revealed identical band patterns with respect to the individual plants assessed and the primers tested, thus increasing the confidence of using RAPD markers to detect genetic variations in blue grama plants. Twelve UBC primers (Table 2) were selected to assay each sample. A total of 69 polymorphic RAPD bands, consisting of DNA fragments of molecular weights ranging from 330 to 1500 base pairs, were generated for each sample. The number of polymorphic bands scored per primer ranged from 3 to 10 with an average of 5 to 6 bands per primer. Two primers (UBC389 and UBC570) had 10 bands scored, while UBC249 had only 3 bands. No bands were found to be unique to plants from any SPs. The band frequencies detected in the SPs ranged from 0 to 1, but most of them were between 0.1 and 0.5 (Fig. 1).
View larger version (42K):
[in this window]
[in a new window]
|
Fig. 1. Distribution of 69 polymorphic RAPD bands with respect to their band frequencies in two selected populations (BMSC and MSC) and their source populations (SPs).
|
|
Genetic Diversity in Source Populations
Several patterns of RAPD variation in blue grama plants from the 11 SPs are given in Table 1. The numbers of polymorphic bands for these populations ranged from 46 to 61 with an average of 57 per population. The populations OAK and GDL2 had 46 and 52 polymorphic bands, respectively, while the populations DGL and RSL had 61 polymorphic bands each (Table 1). The mean band frequency for each population ranged from 0.389 to 0.459 with an average of 0.416 (Table 1). This indicated that most of the bands could be detected in four out of 10 plants sampled from each population. Out of the 69 polymorphic bands, three bands had frequencies less than 0.05 and one band close to unity (results not shown). The pattern of frequency distribution for each population was roughly similar and compatible with those calculated over 108 plants from all SPs (Fig. 1).
Average RAPD variation within a population, when estimated following Nienhuis et al. (1994), ranged from 0.229 to 0.249 with an average of 0.238 and, when estimated by AMOVA, ranged from 15.54 to 16.84 with an average of 16.25 (Table 1). These two sets of estimates, although in different scales, revealed the same pattern that within-population RAPD variation was similar for all SPs. Such uniformity was unexpected as these SPs were at least 30 km apart (Phan and Smith, 2000). This pattern may be indicative of (i) low differential selection pressures from habitat differences among the sampled sites and/or (ii) the consequence of strong gene flow between these natural populations. Further studies are needed to provide information on gene flow between natural blue grama populations and its effect on genetic diversity.
The proportions of the total observed RAPD variation within and between populations estimated by AMOVA were 97.8 and 2.2%, respectively. Despite the low between-population variation, it was significant from zero (P < 0.01), suggesting the presence of different genetic backgrounds among the SPs. The large within-population RAPD variation was expected for highly outcrossing blue grama plants and compatible with the genetic variability previously detected by McGinnies et al. (1988). Similar levels of within-population variation have been observed in RAPD studies for other outcrossing grass species, including smooth bromegrass and meadow bromegrass (Ferdinandez, 1999), buffalograss (Huff et al., 1993; Peakall et al., 1995), perennial ryegrass (Huff, 1997), and little bluestem (Huff et al., 1998).
The genetic relationships of the 11 SPs were presented in the form of a dendrogram constructed using inter-population distances estimated from AMOVA (Fig. 1A). Four major groups were observed (CHC and CVY; GDL1, GDL2 and DGL; KGR, LDR, RSL, and SDY; and OAK and S10). However, these groupings were not significantly (P = 0.481) associated with geographical origin (results not shown). For example, KGR and LDR (two of the most southern populations) were clustered together, but were also associated with RSL (the most northern population). Such nonsignificant association was not surprising, given the detection of similarly high levels of RAPD variation within each SP.
These results represented the first documentation of DNA variation in blue grama plants. No RAPD bands were found to be unique to specific SPs. These SPs had similarly high levels (about 98%) of within-population RAPD variation and extremely low levels (about 2%) of between-population RAPD variation. Observed variation was not associated with geographical distances. These findings were not consistent with population differences documented in morphology and flowering between widely separated blue grama plants in USA (Cornelius, 1947; McMillan, 1956; McMillan, 1959a, b; Miller, 1967). Our results may reflect only the RAPD variations for natural populations in the northern fringe of blue grama's distribution in southern Manitoba (Hitchcock, 1950), and not necessarily for those in the southern latitudes.
In spite of the limited range of these SPs, our findings are still significant for sampling genetic diversity. First, the geographical scope of collecting blue grama germplasm should be expanded into the southern latitudes, given the detection of nonsignificant association of RAPD variations with geographical distances. Second, distant populations should be selected, as the observation of low between-population variation implies high genetic similarity between nearby native stands. Third, fewer tillers could be sampled from a native stand, as the detection of larger within-population variation implies the presence of smaller effective population size in a natural population. However, exact sample size still needs to be determined empirically.
Comparative Genetic Diversity in Selected Populations
To assess genetic shift in the selected populations, comparisons were made of RAPD variations between SPs and each selected population. Population BMSC maintained all 69 polymorphic bands detected in this study and MSC had only 65 (Table 2), as four polymorphic bands of frequency 0.972, 0.073, 0.056, and 0.019, respectively, were fixed in MSC. Population BMSC had 36 polymorphic bands with reduced band frequencies relative to the SPs, three fewer than MSC (Table 2). Fewer numbers of significant Chi-square tests for band frequency change were obtained in BMSC than MSC (8 and 24 at P < 0.05, and 2 and 6 at P < 0.001, respectively; Table 2), indicating a small change in band frequency in BMSC. Further assessment of band frequency changes revealed three RAPD bands (UBC346E, UBC570F, and UBC580C) displaying significantly (P < 0.01) large reductions ( >50%) in band frequency in both populations. Such reduction could occur if these apparently selective (AS) bands were associated with viability genes acting at gametic and zygotic stages, but verification of these causes requires an assessment of segregation patterns of the AS bands in specific crosses (Fu and Ritland, 1994).
Heterogeneity Chi-square tests for all 69 polymorphic bands revealed highly significant changes in band frequency (
2 = 155.1 for BMSC and 301.8 for MSC, respectively, P < 0.0001; Table 3). When the three AS bands were excluded from the analysis, the significance level of the heterogeneity test was reduced from 0.0001 to 0.0255 in BMSC, but still remained similar in MSC (Table 3). Assessment of variation pattern in band frequency in each selected population (Fig. 1) also revealed greater departure from the SPs in MSC than BMSC. Thus, genetic shift was present in both selected populations.
View this table:
[in this window]
[in a new window]
|
Table 3. Significance level of testing difference in RAPD variation and distances of blue grama plants between two selected populations (BMSC and MSC) and their source populations (SPs).
|
|
Population BMSC displayed closer genetic relationship with its SPs than MSC (Fig. 2B). The interpopulation distances obtained between a selected population and its SPs were 0.006 for BMSC/SPs and 0.019 for MSC/SPs, both of which were highly significant from zero (P < 0.0001; Table 3). However, without the three AS bands, the distance observed for BMSC/SPs was reduced from 0.006 to 0.001 and not significant from zero (P = 0.1553; Table 3), but the distance obtained for MSC/SPs was only reduced slightly and remained significant at P < 0.0001 (Table 3). The Mahalanobis distances obtained from canonical discriminant analysis of the RAPD data were 3.22 for BMSC/SPs and 7.87 for MSC/SPs, both of which were highly significant from zero (P < 0.0077 and P < 0.0001, respectively; Table 3). Without the three AS bands, the distance for BMSC/SPs was reduced from 3.22 to 2.87 and less significant from zero (P = 0.0278; Table 3).
View larger version (23K):
[in this window]
[in a new window]
|
Fig. 2. UPGMA clustering of blue grama populations based on inter-population distances obtained from AMOVA on the detected polymorphic RAPD bands. A: The relationships of 11 natural populations and B: The relationships of the selected populations (BMSC and MSC) with their source populations (SPs) (with the three apparently selective RAPD bands).
|
|
To illustrate the genetic shift of both selected populations away from their SPs, a scattergram of all individual plants assessed was generated from the first two canonical variables obtained (Fig. 3). Population BMSC appeared to be slightly shifted away from its SPs by the second canonical variable, so was MSC by the first canonical variable. Without the three AS bands, the shifting patterns remained the same, but the shifting magnitudes were slightly reduced (results not shown). Comparisons of the interpopulation and Mahalanobis distances revealed no difference in shifting pattern, although the applied canonical discriminant analysis displayed a slightly higher sensitivity to significance testing of the Mahalanobis distances.
View larger version (25K):
[in this window]
[in a new window]
|
Fig. 3. Scattergram of all individual blue grama plants in two selected populations (BMSC and MSC) and their source populations (SPs) determined on the basis of the first two canonical variables (CAN1 and CAN2) obtained from canonical discriminant analysis of the RAPD data.
|
|
These diversity comparisons demonstrated the presence of small genetic shifts in both selected populations (0.6% for BMSC and 1.9% for MSC). The shift in BMSC was largely caused by the large reduction of band frequency in the three RAPD bands that might be associated with genes responsible for some type of viability selection. The shift in MSC may largely reflect the founder effect expected from the use of the small initial population size (25 out of 495 clones; Falconer and Mackay, 1996). The applied unequal representation of the SPs might also contribute to the shift observed in MSC. However, further studies are needed to assess the exact impacts of initial population size and selection protocol (unequal vs. balanced representation of SPs) on the genetic diversity captured from SPs (Larson et al., 2000). These assessments will facilitate breeding and utilization of blue grama and other under-exploited native grass species (Smith and Whalley, 2002).
|
ACKNOWLEDGMENTS
|
|---|
The authors gratefully acknowledge the financial support of Ducks Unlimited Canada on this research. Thanks also go to Dr. Daryl Somers for his technical support on the research and Mr. Yasas Ferdinandez for his technical assistance on the RAPD analysis.
Received for publication July 29, 2002.
|
REFERENCES
|
|---|
- Cooper, H.W. 1957. Some plant materials and improved techniques used in soil and water conservation in the Great Plains. J. Soil Water Conserv. 12:163–168.
- Coors, J.G., and M.C. Mardones. 1989. Twelve cycles of mass selection for prolificacy in maize. I. Direct and correlated responses. Crop Sci. 29:262–266.[Abstract/Free Full Text]
- Cornelius, D.R. 1947. The effect of source of little bluestem seed on growth, adaptation, and use in revegetation seedings. J. Agric. Res. 74:133–143.
- Crowle, W.L. 1970. Revenue slender wheatgrass. Can. J. Plant Sci. 50:748–749.
- Duebbert, H.F., E.T. Jacobson, K.F. Higgins, and E.B. Podoll. 1981. Establishment of seeded grasslands for wildlife habitat in the prairie pothole region. US Fish and Wildlife Service. Wildlife No. 234. Washington, DC.
- Excoffier, L., P.E. Smouse, and J.M. Quattro. 1992. Analysis of molecular variance inferred from metric distances among DNA haplotypes: Application to human mitochondrial DNA restriction data. Genetics 131:479–491.[Abstract]
- Falconer, D.S., and T.F.C. Mackay. 1996. An introduction to quantitative genetics, 4th Ed. Longarm Ltd. Burnt Mill, Harlow, England.
- Ferdinandez, Y.S.N. 1999. Characterization of meadow bromegrass X smooth bromegrass hybrid populations using morphological characteristics, quality parameters and RAPD markers. MSc. Thesis, Univ. of Saskatchewan, Saskatoon, SK, Canada.
- Fu, Y.B., and K. Ritland. 1994. Evidence for the partial dominance of viability genes contributing to inbreeding depression in Mimulus guttatus. Genetics 136:323–331.[Abstract]
- Gaffney, F.B., and J.A. Dickerson. 1987. Species selection for revegetating sand and gravel mines in the Northeast. J. Soil Water Conserv. 42:358–361.
- Gunter, L.E., G.A. Tuskan, and S.D. Wullschleger. 1996. Diversity among populations of switchgrass based on RAPD markers. Crop Sci. 36:1017–1022.[Abstract/Free Full Text]
- Helms, T.C., A.R. Hallauer, and O.S. Smith. 1989. Genetic variability estimates in improved and nonimproved Iowa Stiff Stalk Synthetic maize populations. Crop Sci. 29:959–962.[Abstract/Free Full Text]
- Hitchcock, A.S. 1950. Manual of the grasses of the United States. 2nd Ed., Rev. by A. Chase. USDA Misc. Publ. No. 200.
- Huff, D.R. 1997. RAPD characterization of heterogeneous perennial ryegrass cultivars. Crop Sci. 37:557–564.[Abstract/Free Full Text]
- Huff, D.R., R. Peakall, and P.E. Smouse. 1993. [Buchloë dactyloides (Nutt.) Engelm.] RAPD variation within and among natural populations of outcrossing buffalograss. Theor. Appl. Genet. 86:927–934.[Web of Science]
- Huff, D.R., J.A. Quinn, B. Higgins, and A.J. Pallazo. 1998. Random amplified polymorphic DNA (RAPD) variation among native little bluestem [Schizachyrium scoparium (Michx.) Nash] populations from sites of high and low fertility in forest and grassland biomes. Mol. Ecol. 7:1591–1598.
- Jones, T.A., D.C. Neilson, and J.R. Carlson. 1991. Development of a grazing-tolerant native grass for revegetating bluebunch wheatgrass sites. Rangelands 13:147–150.
- Jones, T.A., S.R. Larson, D.C. Nilson, S.A. Young, N.J. Chatterton, and A.J. Palazzo. 2002. Registration of P-7 bluebunch wheatgrass germplasm. Crop Sci. 42:1754–1755.[Free Full Text]
- Knapp, E.E., and K.J. Rice. 1996. Genetic structure and gene flow in Elymus glaucus (blue wildrye): Implications for native grassland restoration. Restor. Ecol. 4:1–10.
- Larson, S.R., T.A. Jones, Z.M. Hu, C.L. McCracken, and A. Palazzo. 2000. Genetic diversity of bluebunch wheatgrass cultivars and a muliti-origin polycross. Crop Sci. 40:1142–1147.[Abstract/Free Full Text]
- May, K.W., B. Wark, and B. Coulman. 1997. Ecovar development on the northern great plains of North America. Section 1.89–1.90. In Proc. of the XVII International Grasslands Congress-Winnipeg, MB and Saskatoon, SK, Canada.
- McGinnies, W.J., W.A. Laycock, T. Tsuchia, C.M. Yonker, and D.A. Edmonds. 1988. Variability within a native stand of blue grama. J. Range Manage. 5:391–395.
- McMillan, C. 1956. Nature of the plant community.II. Variation in flowering behavior within populations of Andropogon scoparius. Am. J. Bot. 43:429–436.
- McMillan, C. 1959a. Nature of the plant community. V. Variation within the true prairie community-type. Am. J. Bot. 46:418–424.
- McMillan, C. 1959b. The role of ecotypic variation in the distribution of the central grassland of North America. Ecol. Monogr. 29:285–307.
- Miller, R.V. 1967. Ecotypic variation in Andropogon scoparius and Bouteloua gracilis. Ph.D. Thesis, Colorado State Univ., Fort Collins, Colorado.
- Nienhuis, J., J. Tivang, and P. Skroch. 1994. Analysis of genetic relationships among genotypes based on molecular marker data. p. 8–14. In Analysis of molecular marker data. Joint Plant Breeding Symposia Series, Corvallis, OR. 5–6 August 1994.
- Peakall, R., P.E. Smouse, and D.R. Huff. 1995. Evolutionary implications of allozyme and RAPD variation in diploid populations of dioecious buffalograss Buchloë dactyloides. Mol. Evol. 4:135–147.
- Pedreira, C.G.S., and R.H. Brown. 1996. Physiology, morphology, and growth of individuals of selected and unselected bahiagrass populations. Crop Sci. 36:138–142.[Abstract/Free Full Text]
- Phan, A.T. 2000. Genetic diversity of blue grama (Bouteloua gracilis) and little bluestem (Schizachyrium scoparium) as affected by selection. Ph.D. Thesis, Univ. of Manitoba, Manitoba, MB, Canada.
- Phan, A.T., and S.R. Smith, Jr. 2000. Seed yield variation in blue grama and little bluestem plant collections in Manitoba, Canada. Crop Sci. 40:555–561.[Abstract/Free Full Text]
- Riegel, A. 1941. Life history and habits of blue grama. Trans. Kansas Acad. Sci. 44:76–83.
- Rodgers, D.M., J.P. Murphy, and K.J. Frey. 1983. Impact of plant breeding on the grain yield and genetic diversity of spring oats. Crop Sci. 23:737–740.[Abstract/Free Full Text]
- Rohlf, F.L. 1997. NTSYS-pc: Numerical taxonomy and multivariate analysis system. Exeter Publ. Ltd., Setauket, NY.
- Roundy, B.A. 1999. Lessons from historical rangeland revegetation for today's restoration. p. 33–38. In L.K. Holzworth and R.W. Ray (comps.) Revegetation with native species: proceedings. RMRS-P-8. USDA, Forest Service, Rocky Mountain Research Station, Ogden, UT.
- SAS Institute. 1996. SAS/STAT user's guide 6.03, SAS Institute Inc., Cary, NC.
- Smith, S.R., Jr., and A.T. Phan. 1999. Maintaining genetic diversity in native grass breeding. VIth International Rangeland Congress Proc. 2:648–650.
- Smith, S.R., Jr., and R.D.B. Whalley. 2002. A model for expanded use of native grasses. Native Plants J. 3:38–49.
- Smoliak, S., and A. Johnson. 1980. Elbee northern wheatgrass. Can. J. Plant Sci. 60:1473–1475.
- Smoliak, S., and A. Johnson. 1983. Walsh western wheatgrass. Can. J. Plant Sci. 63:759–761.
- Sokal, R.R., and C.D. Michener. 1958. A statistical method for evaluating systematic relationships. Univ. Kans. Sci. Bull. 38:1409–1438.
- Stojsin, D., and L.W. Kannenberg. 1994. Genetic changes associated with different methods of recurrent selection in five maize populations: II. Indirectly selected traits. Crop Sci. 34:1473–1479.[Abstract/Free Full Text]
- Vogel, K.P., and J.F. Pedersen. 1993. Breeding systems for cross-pollinated perennial grasses. Plant Breed. Rev. 11:251–274.
- Werner, B.K., and G.W. Burton. 1991. Recurrent restricted phenotypic selection for yield alters morphology and yield of Pensacola bahiagrass. Crop Sci. 31:48–50.[Abstract/Free Full Text]
- Williams, J.G.K., A.R. Kubelik, K.J. Livak, J.A. Rafalski, and S.V. Tingey. 1990. DNA polymorphisms amplified by arbitrary primers are useful as genetic markers. Nucleic Acids Res. 18:6531–6535.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
Y. S. N. Ferdinandez, B. E. Coulman, and Y.-B. Fu
Detecting Genetic Changes over Two Generations of Seed Increase in an Awned Slender Wheatgrass Population Using AFLP Markers
Crop Sci.,
May 6, 2005;
45(3):
1064 - 1068.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y.-B. Fu, A. T. Phan, B. Coulman, and K. W. Richards
Genetic Diversity in Natural Populations and Corresponding Seed Collections of Little Bluestem as Revealed by AFLP Markers
Crop Sci.,
November 1, 2004;
44(6):
2254 - 2260.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y.-B. Fu, Y. S. N. Ferdinandez, A. T. Phan, B. Coulman, and K. W. Richards
AFLP Variation in Four Blue Grama Seed Sources
Crop Sci.,
January 1, 2004;
44(1):
283 - 288.
[Abstract]
[Full Text]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
