Agrostis Species Relationships Based on Trnl-Trnf and Atpi-Atph
Total Page:16
File Type:pdf, Size:1020Kb
HORTSCIENCE 47(1):18–24. 2012. from these Agrostis diversity studies, but there have been no studies designed to specifically explore these relationships. Agrostis Species Relationships Based on Species relationships can be deduced from nuclear and plastid DNA sequences. trnL-trnF and atpI-atpH Intergenic Reichman et al. (2006) sequenced the chlo- roplast matK gene and nuclear internal tran- Spacer Regions scribed spacer (ITS) region from 19 Agrostis and three Polypogon accessions. Phyloge- Keenan Amundsen1 netic analysis of the DNA sequences was Department of Agronomy and Horticulture, University of Nebraska, 377H used to determine if transgenic A. stoloni- Plant Science Hall, Lincoln, NE 68583-0915 fera from a controlled area was capable of pollinating wild populations of related spe- Scott Warnke cies growing at a distance. The individual Floral and Nursery Plants Research Unit, U.S. Department of Agriculture, phylogenies were used to distinguish Agro- stis accessions by species. Certain Agrostis Beltsville, MD 20705 species have been included in phylogenies Additional index words. turfgrass, Agrostis, chloroplast, phylogeny of the Aveneae and Poeae tribes based on DNA sequence data, placing Agrostis spe- Abstract. The bentgrasses (Agrostis spp.) are among the most important species to the cies sister to Calamagrostis and Polypogon turfgrass industry. They have complex genomes resulting from polyploidization and high species within the tribe Aveneae (D¨oring rates of interspecific hybridization. An understanding of species relationships would et al., 2007; Quintanar et al., 2007; Soreng improve the efficiency of developing improved bentgrass cultivars. To elucidate the et al., 2007). evolutionary relationships among Agrostis species, phylogenetic analyses were per- Inference of Agrostis evolution, a highly formed on sequences of two chloroplast-encoded intergenic spacer regions. A 298-bp outcrossing polyploid, based on ITS or other region of the trnL-trnF intergenic spacer and a 451-bp region of the atpI-atpH intergenic high copy-repetitive sequence elements, spacer were included in the analyses. A total of 47 Agrostis accessions were included with might not provide an accurate depiction of both cultivated and unimproved material from the National Plant Germplasm System. species evolution (Feliner and Rossello´, Of these 47 Agrostis collections, there were 10 unique trnL-trnF haplotypes and eight 2007) and single or low-copy nuclear genes distinct atpI-atpH haplotypes, indicating a high degree of shared sequence identity within might be more informative (Feliner and these chloroplast intergenic regions. These findings suggest that the chloroplast genomes Rossello´, 2007; Sang, 2002). One drawback of A. canina and A. stolonifera are more closely related to each other than either species is of using low copy genes is that they can be to A. capillaris, incongruent with our previous understanding of genome relationships in difficult to identify in non-model organisms the genus. such as Agrostis. Rotter et al. (2007) se- quenced expressed sequence tag DNA li- braries of the two Agrostis tetraploid species The bentgrasses (Agrostis spp.) are im- (Brilman, 2001). The tetraploids A. capillaris A. stolonifera and A. capillaris covering portant species to the turfgrass industry (A1A1A2A2)andA. stolonifera (A2A2A3A3) 10% of the predicted gene space. This because of their ability to form a dense, share one sub-genome in common (A2A2)and sequencing effort led to the identification high-quality turf at low mowing heights. the hexaploid A. gigantea (A1A1A2A2A3A3) of 177 and 161 Oryza Conserved Ortholog There are between 150 and 200 species of has two sub-genomes in common with both Set (COS; Fulton et al., 2002) genes con- Agrostis (Harvey, 2007), and the evolution- A. capillaris and A. stolonifera (Jones, served in the A. capillaris and A. stolonifera ary relationships between species are not 1956b, 1956c). The experiments conducted DNA sequence libraries, respectively. Fulton clearly understood. Deducing these relation- by Jones are among the most compre- et al. (2002) describe a reference set of 1025 ships is complicated by a number of factors. hensive describing the relationships be- COS genes that are single or low copy genes The major turf-type Agrostis species are tween these common turf-type Agrostis and conserved across diverse genomes. highly outcrossing and exhibit high rates of species. Seven of the 161 A. stolonifera and 11 of heterozygosity (Warnke et al., 1998). Sev- Evidence of Agrostis species relationships the 177 A. capillaris Oryza COS gene homo- eral species are polyploid causing homoe- based on contemporary molecular marker logs were found to have conserved sequences ologous loci. Homologous genes often have technologies is lacking. Molecular markers in other grasses. These sequences were used high levels of sequence identity and may have been used in several studies to explore in phylogenetic analyses that placed the not be informative. Intermediate morphol- Agrostis genetic diversity. For example, Agrostis species closer to Festuca arundina- ogies exist between taxa making taxonomic Vergara and Bughrara (2003) examined 400 cea than to Avena sativa, which is interesting classification difficult. Interspecific hybrid- polymorphic amplified fragment length poly- because Agrostis is in the same tribe as ization is common and these reticulation morphism (AFLP) makers in a set of 40 A. sativa, whereas F. arundinacea is in the events are difficult to represent in bifurcat- Agrostis accessions representing 14 species. Poeae tribe. Agrostis was placed in the ing phylograms. They reported that A. transcaspica is diploid Aveneae tribe based on morphological char- Jones (1956a, 1956b, 1956c) described the and based on clustering of AFLP markers, acteristics and enzyme restriction patterns chromosome pairing behavior during meta- this species may have contributed the A3A3 of chloroplast DNA (Soreng and Davis, phase I of meiosis among Agrostis stolonifera, genome to the evolution of A. stolonifera and 1998; Watson, 1990). The two tribes are A. canina, A. capillaris, A. vinealis,andA. A. gigantea. Amundsen and Warnke (2011) closely related (Kellogg, 1998; Soreng gigantea. Agrostis vinealis is an autotetra- explored genetic diversity among 75 Agrostis et al., 2007) and share many common chlo- ploidization of A. canina (Jones, 1956a) accessions along with six closely related roplast DNA restriction sites (Soreng et al., and these species have the genome designa- species based on 1309 miniature inverted- 1990). tions A1A1A1A1 and A1A1, respectively repeat transposable element (MITE) display Chloroplast sequences would be more in- markers. The modified AFLP technique, formative for deducing Agrostis relationships MITE display, anchors the amplified prod- because chloroplasts are maternally inher- Received for publication 26 Aug. 2011. Accepted ucts to MITEs. The Agrostis accessions were ited in Agrostis and have simple genomes for publication 10 Nov. 2011. divided into six clades based on marker (Warnke, 2003). Soreng et al. (2007) per- 1To whom reprint requests should be addressed; clustering (Amundsen and Warnke, 2011). formed a phylogenetic analysis of the tribe e-mail [email protected]. Species relationships can be partially inferred Poeae using morphological characteristics and 18 HORTSCIENCE VOL. 47(1) JANUARY 2012 sequence data of three chloroplast-encoded Agrostis based on chloroplast sequences. In Materials and Methods genes, maturase K (matK), NADH dehy- the present study, the chloroplast encoded drogenase subunit F (ndhF), and ATP trnL-trnF and atpI-atpH intergenic spacer Plant material and DNA extraction. Ac- synthase beta subunit (atpb). The sequence regions were sequenced from a diverse set of cessions of Agrostis were chosen that repre- data for this project are available through Agrostis germplasm to study the relation- sent cultivated and non-cultivated accessions, the National Center for Biotechnology In- ships between accessions. Phylogenies of various ploidy levels as predicted by flow formation databases and the analysis in- both cultivated and non-cultivated National cytometry, different species, and different cluded the species Agrostis tenerrima Trin., Plant Germplasm System Agrostis acces- geographic regions (Table 1). Seeds of each Calamagrostis arundinacea (L.) Roth., C. sions were compared to identify any in- accession were obtained from the National canadensis (Michx.) P. Beauv., Polypogon congruence and infer species relationships. Plant Germplasm System, Dr. Doug Johnson monspeliensis, Festuca rubra L., and Species relationships are complex in Agro- (Forage and Range Research Laboratory, F. subverticillata (Pers.) E.B. Alexeev. stis, but a better understanding will assist U.S. Department of Agriculture), or from Soreng et al. (2007) found that molecular plant breeders in maximizing wide cross- the National Turfgrass Evaluation Program. character data were better than morpholog- breeding, identify bridging species to intro- Seeds were planted in Premier Pro-Mix BX ical data at describing a well-resolved set gress important traits, identify evolutionary soil (Premier Horticulture Inc., Quakertown, of species relationships. Similarly, D¨oring events that have led to important turf charac- PA) in 2.5-cm-diameter Cone-tainers (Stuewe et al. (2007) sequenced the matK gene from teristics, and resolve polyploidization events and Sons, Tangent, OR) and maintained a number of specimens from the Aveneae/ in the genus.