Crop Science 41:1300-1305 (2001)
© 2001 Crop Science Society of America
PLANT GENETIC RESOURCES
AFLP Variation in Agamospermous and Dioecious Bluegrasses of Western North America
S. R. Larson*,a,
B. L. Waldrona,
S. B. Monsenb,
L. St. Johnc,
A. J. Palazzod,
C. L. McCrackena and
R. D. Harrisona
a USDA-ARS, Forage and Range Res. Lab., Utah State Univ., Logan, UT 84322-6300
b USDA-FS, Rocky Mountain Res. Stn., 735 North 500 East, Provo, UT 84606-1856
c USDA-NRCS, Aberdeen Plant Materials Center, 1691A South 2700 West, Aberdeen, ID 82100-296
d USDOD-ACE, Cold Regions Research and Engineering Lab., 72 Lyme Road, Hanover, NH 03755-1290
* Corresponding author (stlarson{at}cc.usu.edu)
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ABSTRACT
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Native perennial bluegrasses are common and persistent in the understory steppe vegetation of western North America. The agamospermous Poa secunda Presl. complex circumscribes a number of commonly recognized forms including big bluegrass (P. ampla Merr.), canby bluegrass (P. canbyi Scribn.), and sandberg bluegrass (P. sandbergii Vasey). Poa fendleriana (Steudel) Vasey is a dioecious, morphologically distinct bluegrass species that is also native to western North America. The amplified fragment length polymorphism (AFLP) method was used to analyze genetic variation within and among cv. Canbar canby bluegrass, cv. Sherman big bluegrass, two allopatric natural populations of sandberg bluegrass, and one natural germplasm source of P. fendleriana. Results indicate that Sherman and Canbar are comprised of one or several fixed genotypes, respectively, that are related to sandberg bluegrass. Although several fixed genotypes were also detected within the two natural sandberg bluegrass populations, high levels of genetic diversity were present in the agamospermous sandberg populations and dioecious P. fendleriana population. Patterns of AFLP variation in P. secunda are consistent with facultative apomixis and outcrossing mode of reproduction. Moreover, population differentiation between the two highly diverse natural sandberg bluegrass populations, collected from sites nearly 600 km apart, is very low (GS = 0.14) and reflect a high degree of gene flow. However, the AFLP profiles of Canbar canby bluegrass and Sherman big bluegrass were distinct from sandberg bluegrass. The P. secunda complex, as a group, was clearly distinguishable from P. fendleriana. Thus, DNA fingerprinting was used to characterize naturally diverse bluegrass germplasm sources that may be used for large-scale revegetation efforts across the western USA.
Abbreviations: AFLP, amplified fragment length polymorphism • nt, nucleotides
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INTRODUCTION
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THE GENUS Poa displays extraordinary ecological and reproductive diversity (Kellogg, 1985a) and is of great importance in forage production, soil stabilization, and lawns. Poa secunda is a dominant perennial bluegrass in the understory steppe vegetation of western North America (Daubinmire, 1970) and has the capacity to produce superior forage and flourish under heavy sheep grazing (Allred, 1945; Stark et al., 1950; Daubinmire, 1970; Olson and Wallander, 1998; Rickard, 1975). On overgrazed sites, P. secunda may be the only perennial grass remaining (Hull and Stewart, 1948). Poa secunda is commonly distinguished from the rest of the genus by the lack of a prominent keel on the lemma (Hitchcock, 1950). Spiklet shape, rachilla-internode length, and lack of cobwebby lemma hairs also distinguish P. secunda from most other Poa species (Kellogg, 1985a). The agamospermous Poa secunda complex is considered a facultative apomictic (Hiesey and Nobs, 1982; Kellogg, 1987, 1990) and floral variation among P. secunda populations of eastern Washington is consistent with apomictic differentiation (Gilmartin et al., 1986). Members of the P. secunda have been placed in as many as 45 species (Kellogg, 1990) including big bluegrass (P. ampla Merr.), canby bluegrass (P. canbyi Scribn.), and sandberg bluegrass (P. sandbergii Vasey) (Arnow, 1981; Kellogg, 1985a,b). Yet, quantitative studies of variation in agamospermous grasses give little evidence of microspecies formation (Usberti and Jain, 1978; Ishimitsu and Tateoka, 1983; Helgadóttir and Snaydon, 1986; Kellogg, 1990). Moreover, sister groups of P. secunda may also be sought with other bluegrasses native to western North America including P. fendleriana (Steudel) Vasey, which displays similar morphological characteristics (Kellogg, 1985a). However, P. fenderliana is characterized as incompletely dioecious (Hitchcock, 1950) with plants usually pistillate or occasionally hermaphroditic (Cronquist et al., 1977; Soreng, 1991). Moreover, the chloroplast DNA of P. fendleriana is also different from that of P. secunda (Soreng, 1990).
Four varieties or accessions of P. secunda are currently available for large-scale revegetation efforts (Alderson and Sharp, 1993). The most widely recognized varieties used in rangeland revegetation, in the western USA are Sherman (big bluegrass) and Canbar (canby bluegrass). Sherman big bluegrass was developed by mass selection of an agronomically superior accession collected in 1932 and recollected in 1935 from Sherman Co., OR. Canbar was presumably increased directly from a superior accession, identified in a large observational nursery of native bluegrass collections. Canbar was collected from Columbia Co., Oregon, and released in 1979. Both Sherman and Canbar have also been evaluated in an extensive hybrid-breeding program (Hiesey and Nobs, 1982) involving wide crosses with Kentucky bluegrass (P. pratensis L.). Two other varieties, 9005460 and Service, are also produced as a direct seed increase of germplasm collected near Laramie, WY, and Whitehorse, Yukon Territory, respectively. However, natural germplasm sources for other bluegrass species of western North America are not widely recognized or utilized.
Supplemental funding, seed cost, and seed availability are factors that limit implementation of native plant species in large-scale fire rehabilitation, the overwhelming revegetation effort on public rangelands of the western USA (Richards et al., 1998). However, commercial seed growers can efficiently produce an adequate supply of high-quality native grass seed if the market demand is sufficiently reliable for their products. Yet, some ecologists are concerned that the agronomic approach, typically used in cultivar development, reduces or eliminates genetic diversity. Consequently, cultivars may lack the genetic diversity needed to maintain adaptation in dynamic environments, may not be adapted over broad regions, and may contribute to genetic pollution of remnant natural populations (Roundy et al., 1997; Roundy, 1999). In any case, natural genetic diversity and germplasm identity may be important characteristics to consider in the selection, development, and marketing of native plant materials that will be used in large-scale revegetation efforts. However, the amplitude of genetic diversity within and among natural populations and commercial germplasm sources remains an unwieldy question of considerable importance to many conservation groups and land managers.
The AFLP method (Vos et al., 1995) is a robust DNA fingerprinting technique that is highly informative within many plant species. The objective of this study is to use the AFLP method to characterize genetic variation within and between germplasm sources of the agamospermous P. secunda complex and dioecious P. fendleriana.
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MATERIALS AND METHODS
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The YTC sandberg bluegrass population (Table 1) was comprised of one or two plants from each of 19 different sites at the Yakima Training Center collected in 1998. The MH sandberg bluegrass population (Table 1) was comprised of plants grown from seeds collected and bulked from the Mountain Home site in 1997. The Canbar and Sherman plants (Table 1) were grown from seed obtained from the USDA-NRCS, Plant Materials Center at Pullman WA. The P. fendleriana plants (Table 1) were grown from seed collected and bulked directly from the Caliente, NV, site in 1995. Greenhouse specimens of P. secunda displayed perfect flowers, whereas the P. fendleriana plants displayed either perfect or pistillate flowers. Morphology of these greenhouse specimens were consistent with the descriptions of these species (Hitchcock, 1950; Cronquist et al., 1977).
Relative nuclear DNA contents were compared between individual plants within and between populations (excluding the YTC sandberg population) with a Partec Cell Analyzer CA II (Partec GmbH, Münster, Germany). Nuclei were prepared with the Partec High Resolution DNA kit P.
DNA fingerprinting was conducted by means of the AFLP technique according to the methods of Vos et al. (1995), except that EcoR I selective amplification primers included fluorescent 6-FAM (6-carboxy fluorescein) label on the 5' nucleotide. Selective amplifications were performed with seven primer pairs and three selective nucleotides on each primer (e.g., E.ACC//M.CTC, E.AGC//M.CAC, M.AGC//M.CAT, M.AGG//M.CAA, E.AGG//M.CAG, E.AGG//M.CTA, and M.AGG//M.CTG), as described by Vos et al. (1995). The amplified fragments were fractionated and detected with an ABI373XL instrument (PE Applied Biosystems, Foster City, CA) using 34 cm well-to-read polyacrylamide gels formulated with 5.75% (w/v) Long Ranger Singel packs (FMC, Rockland, ME), 7 M urea, and 1 x TBE running buffer. Each sample lane included the GS500-ROX (PE Applied Biosystems) internal lane size standards (fluorescently labeled with rhodamine X) that range from 35 nucleotides (nt) to 500 nt. Fluorescent signals of the 6-FAM labeled AFLPs, between 35 nt and 500 nt, were identified by GeneScan 3.1 software (PE Applied Biosystems). The GeneScan sample (trace) files were subsequently analyzed for the presence and absence of AFLP products, in 
1 nt intervals, by Genographer (Benham et al., 1999).
The degree of polymorphism within populations was quantified using the Shannon-Weaver diversity index:
where 
is the frequency of Phenotype i, averaged over each AFLP primer pair (Paul et al., 1997; Larson et al., 2001). Likewise, the total amount of polymorphism between populations, averaged over each AFLP primer pair, was quantified as follows:
where Pi is the average i of each population. Differentiation among populations was calculated as the proportion of total variation among populations as follows:
where HAVW is the average HW for each population.
Estimates of genetic similarity between individual genotypes were based on Jaccard's similarity coefficient as follows:
where M is the number of matches (shared fragments) and N is the number of mismatches (Jaccard, 1908). Relationships between individual genotypes were analyzed by cluster analysis, of the Jaccard's similarity matrix, using the unweighted pair-group (UPGMA) procedure in NTSYS-PC (Rohlf, 1992).
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RESULTS AND DISCUSSION
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AFLP Variation between P. secunda and P. fendleriana
P. fendleriana displayed fewer AFLP fragments per plant than P. secunda (Table 2). The number of AFLPs per plant is a function of the genome size, complexity, and heterozygosity. Reports of chromosome numbers in P. fendleriana are 2n = 28 + 1 and 2n = 56 (Soreng, 1990). Most forms of P. secunda contain 63 (e.g. big bluegrass) or 84 chromosomes (Hiesey and Nobs, 1982). Therefore, it is not surprising that the P. fendleriana population displayed fewer AFLPs per plant than P. secunda. However, the relative DNA contents of the P. fendleriana plants were greater than P. secunda plants. Cytogenetic comparisons suggest that the chromosomes of P. cusickii, a close relative of P. fendleriana (Soreng, 1990; Soreng 1991), may be physically larger than the chromosomes of P. secunda (Stebbins and Love, 1941). Therefore, we speculate that the large P. fendleriana chromosomes may contain more repetitive DNA than P. secunda.
The proportion of shared AFLP fragments between P. fendleriana and P. secunda is higher than would be expected by chance alone. On average, we detected approximately 52 AFLP fragments per plant per primer pair in P. secunda and about 39 fragments per plant per primer pair in P. fendleriana (Table 2). The average lengths of the smallest and largest DNA fragments range from 62 nucleotides (nt) to 486 nt, with an overall average of 248 nt. With approximately 0.12 fragments per plant per nt interval in P. secunda and about 0.09 fragments per plant per nucleotide interval in P. fendleriana, the proportion of shared fragments (identical in size) expected by chance alone, is 0.01. However, the average proportion of shared fragments observed between individual plants of P. fendleriana and P. secunda actually ranged from 0.19 to 0.29 (Table 2). Therefore, the proportion of shared fragments between individual plants of P. fendleriana and P. secunda (i.e., 0.23) is higher than expected by chance alone (i.e., 0.01). As a group, the P. secunda populations displayed about 109 fragments per nt interval, whereas the P. fendleriana population dispalyed about 74 fragments per nucleotide interval (Table 2). With approximately 0.25 fragments per nucleotide interval in P. secunda and 0.17 fragments per nucleotide interval in P. fendleriana, the proportion of shared fragments expected by chance alone is about 0.04 (i.e., between species, considered collectively). However, only 103 fragments (less than 0.12 of total) were unique to P. fendleriana and only 343 fragments (less than 0.40 of total) were unique to P. secunda (Table 2). Therefore, the proportion of fragments present in both species (0.48), considered collectively, is considerably greater than would be expected by chance alone (i.e. 0.04). Although fragments of similar apparent size may not always be homologous, especially among divergent comparisons, we interpret these results to mean that P. fendleriana and P. secunda share homologous AFLP fragments.
AFLP Variation within P. secunda and P. fendleriana
Of the 22 plants analyzed from each cultivar, one fixed genotype was detected in the Sherman big bluegrass and only three genotypes were detected in Canbar canby bluegrass (Table 2, Fig. 1). Although several identical genotypes were also detected within the MH and YTC sandberg bluegrass populations (Table 2, Fig. 1), genetic diversity within these natural sandberg populations is evidently much greater than Sherman or Canbar (Table 2). Composites of true-breeding genotypes could be maintained by self-pollination of homozygous plants or apomixis. Self-pollinated P. secunda plants show seed set comparable to open-pollinated plants, although it is not known whether seed from these plants was produced sexually or by apomixis (Kellogg, 1987). However, aside from a few fixed genotypes, patterns of AFLP variation and estimates of genetic diversity are very similar within natural populations of agamospermous P. secunda and dioecious P. fendleriana (Fig. 1, Table 2). Moreover, Jaccard's similarity coefficients (Table 3) and patterns of AFLP variation (Fig. 1) within these natural bluegrass populations are very similar to that observed in outcrossing populations of bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve) (Larson et al., 2000) and perennial ryegrass (Lolium spp.) (Roldán-Ruiz et al., 2000). Low levels of population differentiation between the two natural sandberg bluegrass populations (GS = 0.14), collected from sites more nearly 600 km apart, also reflect a high degree of gene flow. Population differentiation within outcrossing grasses, such as bluebunch wheatgrass cultivars or perennial ryegrass, is generally quite low (Larson et al., 2000; Roldán-Ruiz et al., 2000), whereas population differentiation within inbreeding species, such as purple needlegrass [Nassella pulchra (Hitchc.) Barkworth], may be generally more pronounced (Larson et al., 2001). These observations are consistent with idea that modes of reproduction may not be very different between outbreeding grasses and agamospermous grasses such as P. secunda (Kellogg, 1990). On the basis of our results (Fig. 1), we speculate that outcrossing is the predominant mode of reproduction in P. secunda. However, P. secunda genotypes may be occasionally fixed (Fig. 1) by facultative apomixis.
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Fig. 1. UPGMA analysis of AFLP variation within and among sandberg bluegrass (Poa secunda) populations collected near Mountain Home (MH), ID, and Yakima Training Center (YTC), WA, cv. Canbar canby bluegrass (P. secunda), cv. Sherman big bluegrass (P. secunda), and one natural population of P. fendleriana collected near Caliente, NV. Plants having identical genotypes are enumerated within parentheses. Bootstrap confidence intervals are indicated for clusters present in the 50% majority-rule consensus of 100 UPGMA searches.
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Table 3. Average Jaccard's similarity coefficients among pair-wise comparisons of individual plants within (diagonal) and between (lower left) populations of Poa secunda and P. fendleriana. The range of observed values, for each comparison, is also shown in parentheses.
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Bootstrap confidence intervals suggest that Canbar canby bluegrass and Sherman big bluegrass can be distinguished from sandberg bluegrass (Fig. 1). Jaccard's similarity coefficients between the Canbar and sandberg bluegrass genotypes are similar or less than the lowest values observed within the natural sandberg bluegrass populations (Table 3). Moreover, we detected 15 AFLP fragments that were unique to Canbar and the average number of AFLPs per plant in Canbar was slightly more than the highest number of fragments observed in the sandberg bluegrass plants (Table 2). However, the relative DNA content in Canbar (2n = 84) could not be distinguished from sandberg bluegrass. Jaccard's similarity coefficients between the Sherman and sandberg bluegrass genotypes are well below the lowest similarity values observed within the natural sandberg bluegrass populations (Table 3). Moreover, we detected 49 AFLP fragments that were unique to the single Sherman genotype and the average number of AFLP fragments observed in Sherman is well above the range of values observed in sandberg bluegrass (Table 2). Despite the large number of AFLP fragments detected in Sherman, the relative DNA content of Sherman (2n = 63) was consistently less than Canbar (2n = 84) or sandberg bluegrass. Most forms of P. secunda contain approximately 63 or 84 chromosomes (Hiesey and Nobs, 1982). However, an inverse relationship between the number of AFLP fragments and number of chromosomes may indicate that these polyploid bluegrasses are comprised of slightly different genome combinations.
Results of this study are important in two different manners. DNA fingerprinting using the AFLP method elucidated a high degree of variation within but little divergence between two natural sandberg bluegrass populations, collected from sites nearly 600 km apart. If in fact these populations have similar adaptation potential, then efforts to develop natural germplasm sources for sandberg bluegrass might be streamlined. Conversely, DNA fingerprinting suggests the possibility of genetic discontinuities within the P. secunda complex that may correspond with cytogenetic differences (i.e., 2n = 63 vs. 2n = 84). Moreover, results of this study confirm that other genetically distinct bluegrass species, e.g., P. fendleriana also coexist in western North America. Therefore, advancing methods of DNA analysis may help streamline or facilitate efforts to utilize and conserve native grass species in large-scale revegetation efforts.
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NOTES
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This work was supported by joint contributions of the USDA, Utah Agric. Exp. Stn., Dep. of Defense Strategic Environmental Research and Development Program CS1103 project, and US Army BT25-EC-B09 project (Genetic Characterization of Native Plants in Cold Regions). Trade names are included for the benefit of the reader, and imply no endorsement or preferential treatment of the products listed by the USDA.
Received for publication April 10, 2000.
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REFERENCES
|
|---|
- Alderson, J., and W.C. Sharp. 1993. Grass varieties in the United States. Agriculture Handbook No. 170. USDA, SCS, U.S. Gov. Print. Office, Washington, DC.
- Allred, B.W. 1945. Some conditions and influences pertaining to the native forage crop of the northern mixed prairie. J. Am. Soc. Agron. 37:876–887.
- Arnow, L.A. 1981. Poa secunda Presl. versus P. sandbergii Vasey (Poaceae). Syst. Bot. 6:412–421.
- Benham, J., J-U. Jeung, M. Jasieniuk, V. Kanazin, and T. Blake. 1999. Genographer: A graphical tool for automated AFLP and microsatellite analysis. J. Agric. Genomics. 4:article 3 (http://www.ncgr.org/research/jag/papers99/paper399/indexp399.html; verified 21 Feb. 2001).
- Cronquist, A., A.H. Holmgren, N.H. Holmgregn, J.L. Reveal, P.K. Holmgren. 1977. The monocotyledons. In A. Cronquist (ed.) Intermountain flora: vascular plants of the intermountain west, U.S.A. Columbia University Press, New York.
- Daubinmire, A. 1970. Steppe vegetation of Washington. Wash. Agric. Exp. Sta. Tech. Bull. 62.
- Gilmartin, A.J., J. Dobrowolski, D. Soltis, E. Kellogg, and G. Harris. 1986. Variability within and among populations of four grass species. Syst. Bot. 11:559–566.
- Helgadóttir, A. and R.W. Snaydon. 1986. Patterns of genetic variation among populations of Poa pratensis L. and Agrostis capillaris L. from Britain and Iceland. J. Appl. Ecol. 23:703–719.
- Hiesey, W.M., and M.A. Nobs. 1982. Experimental studies on the nature of species: VI. Interspecific hybrid derivatives between facultatively apomictic species of bluegrass and their responses to contrasting environments. Publ. 636. Carnagie Institute, Washington, DC.
- Hitchcock, A.S. 1950. Manual of grasses of the United States. U.S.D.A. Misc. Publ. 200:1–1040.
- Hull, A.C., and G. Stewart. 1948. Replacing cheatgrass by reseeding with perennial grass on southern Idaho ranges. J. Am. Soc. Agron. 40:694–703.
- Ishimitsu, M., and T. Tateoka. 1983. Morphological variation and taxonomy of the Poa macrocalyx complex (Poaceae) in Hokkaido. Bot. Mag. (Tokyo) 96:245–267.
- Jaccard, P. 1908. Nouvelles rescherches sur la distribution florale. Bull. Soc. Vaud. Sci. Nat. 44:223–270.
- Kellogg, E.A. 1985a. A biosystematic study of the Poa secunda complex. J. Arnold Arboretum 66:201–242.
- Kellogg, E.A. 1985b. Variation and names in the Poa secunda complex. J. Range Manage. 38:516–521.
- Kellogg, E.A. 1987. Apomixis in the Poa secunda compex. Am. J. Bot. 74:1431–1437.[ISI]
- Kellogg, E.A. 1990. Variation and species limits in agamospermous grasses. Syst. Bot. 15:112–123.
- Larson, S.R., T.A. Jones, C.L. McCracken, Z.M. Hu, and A.L. Palazzo. 2000. Genetic diversity of bluebunch wheatgrass cultivars and a multiple-origin polycross. Crop Sci. 40:1142–1147.[Abstract/Free Full Text]
- Larson, S.R., E. Cartier, C.L. McCracken, and D. Dyer. 2001. Mode of reproduction and AFLP variation in purple needlegrass (Nassella pulchra): utilization of natural germplasm sources. Mol. Ecol. (in press.)
- Olson, B.E., and R.T. Wallander. 1998. Effect of sheep grazing on a leafy spurge-infested Idaho fescue community. J. Range Manage. 51:247–252.
- Paul, S., F.N. Wachira, W. Powell, and R. Waugh. 1997. Diversity and genetic differentiation among populations of Indian and Kenyan tea (Camellia sinensis (L.) O. Kuntze) revealed by AFLP markers. Theor. Appl. Genet. 94:255–263
- Richards, R.T., J.C. Chambers, and C. Ross. 1998. Use of native plants on federal lands: policy and practice. J. Range Manage. 51:625–632.
- Rickard, W.H. 1975. Vegetation of knob and kettle topography in south-central Washington. Northwest Sci. 49:147–152.
- Roldán-Ruiz, I., J. Dendauw, E. Van Bockstæle, A. Depicker, M. DeLoose. 2000. AFLP markers reveal high polymorphic rates in ryegrasses (Lolium spp.). Mol. Breed. 6:125–134.
- Rohlf, F.J. 1992. NTSYS-pc. Numerical taxonomy and mutivariate analysis system (version 2.02). Exeter Software, Setauket, NY.
- Roundy, B.A., N.L. Shaw, D.T. Booth. 1997. Using native seeds on rangelands. p. 1–8. In N.L. Shaw and B.A. Roundy (comps.) Proceedings: Using seeds of native species on rangelands. Gen. Tech. Rep. INT-GTR-372. U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Ogden, UT.
- Roundy, B.A. 1999. Lessons from historical rangeland revegetation for todays 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.
- Soreng, R.J. 1990. Chloroplast-DNA phylogenetics and biogeography in a reticulating group: study in Poa (Poaceae). Am. J. Bot. 77: 1383–1400.[ISI]
- Soreng, R.J. 1991. Systematics of the Epiles group of Poa (Poaceae). Syst. Bot. 16:507–583.
- Stebbins, G.L., Jr., and R.M. Love. 1941. A cytological study of California forage grasses. Am. J. Bot. Syst. Bot. 11:559–566.
- Stark, R.H., A.L. Hafenrichter, and W.A. Moss. 1950. Adaptation of grasses for soil and water conservation at high altitudes. Agron. J. 42:124–127.[Free Full Text]
- Usberti, J.A., and S.K. Jain. 1978. Variation in Panicum maximum; a comparison of sexual and asexual populations. Bot. Gaz (Chicago) 139:112–116.
- Vos, P., R. Hogers, M. Bleeker, M. Reijans, T. Van de Lee, M. Hornes, A. Frijters, L. Pot, J. Peleman, M. Kuiper, and M. Zabeau. 1995. AFLP: A new technique for DNA fingerprinting. Nucleic Acids Res. 23:4407–4414.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
