Phylogenetic relationships of 30 diploid species of Triticeae (Poaceae) representing 19 genomes were estimated from the sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. The ITS sequence phylogeny indicated that: (i) each genome group of species is monophyletic, concordant with cytogenetic evidence; (ii) Hordeum (I) and Critesion (H) are basal; (iii) Australopyrum (W) is closely related to Agropyron (P); (iv) Peridictyon (G), Heteranthelium (Q), and Dasypyrum (V) are closely related to Pseudoroegneria (S); (v) most of the annuals, Triticum s.l. (A, B, D), Crithopsis (K), Taeniatherum (T), Eremopyrum (F), Henrardia (O), Secale (R), and two perennials, Thinopyrum (J) and Lophopyrum (E), all of Mediterranean origin, are a monophyletic group. However, phylogenetic trees based on morphology group these Mediteranean species with various perennial lineages of the Arctic-temperate region. The molecular data and biogeography of the tribe suggest that the Mediterranean lineage is derived from the Arctic-temperate lineage and that the two lineages have evolved in parallel. Extensive morphological parallelism apparently obscures the true genealogical history of the tribe when only morphology is considered.

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Entire sequences of the internal transcribed spacers (ITSs) and 5.8S subunit of nuclear ribosomal DNA (nrDNA) were obtained from nine grass species by direct double-stranded sequencing of polymerase chain reaction (PCR) amplified DNA fragments. These sequences from subfamily Pooideae (Triticum aestivum, Crithodium monococcum, Sitopsis speltoides, Hordeum vulgare, Secale montanum, Avena longiglumis, Bromus inermis, Brachypodium distachyon) and subfamily Panicoideae (Sorghum bicolor) together with published ITS sequence of rice (Oryza sativa, Bambusoideae) were analyzed using Wagner parsimony (PAUP) and the neighbor-joining distance method to assess the phylogenetic utility of ITS sequences at various taxonomic levels. Among the aligned sequences that ranged from 588 to 603 nucleotides in length, 118 of 269 variable sites contained potential phylogenetic information. A member of Bromus, B. inermis, was the sister taxon to the Triticeae species. Brachypodium was more distantly related to Triticeae than was Bromus or Avena. These data, with Oryza sativa as the outgroup, indicate monophyly of the Pooideae species and of the members of the tribe Triticeae within Pooideae. Phylogenetic trees of the 10 grass species generated from the ITS sequence data were in general agreement with phylogenies based on molecular data from ribosomal RNA (rRNA) and chloroplast DNA (cpDNA) of similar grass taxa. This study reaffirms that sequences of the ITS region are useful for phylogenetic inference among closely related monocot species.

MATERIALS AND METHODS Grazing animals prefer some plants to others. These choices are Cultivars and Experimental Design likely related to physical and chemical factors such as energy-dense The eight endophyte-free tall fescue cultivars included in carbohydrates contained in plants. This study quantified the nonstructhis study were 'Barcel', 'Kenhy', 'Kentucky-31' (KY-31), tural carbohydrate fractions in each of eight vegetatively growing, 'Missouri-96' (MO-96), 'Mozark', 'Stargrazer', and the experiendophyte-free, tall fescue cultivars (Festuca arundinacea Schreb.) mental selections C-1 and HiMag (Mayland and Sleper, 1993). and relates their sugar concentrations to cattle grazing preferences. On 20 Sept. 1991, these grasses were seeded in rows into The experimental area consisted of eight cultivar plots replicated three an irrigated, Portneuf silt loam loess soil (Durinodic Xeric times in each of three pastures. Within each pasture, forage was Haplocalcid) near Kimberly, in south-central Idaho (42Њ30Ј sampled between 0830 and 1000 h mountain daylight time (MDT) N, 114Њ08Ј W, elevation 1200 m). The experimental design during each of four seasons and 2 yr. Freeze-dried forage samples was a randomized complete block with three pastures (blocks), were extracted with hot water and an amylase (Clarase) solution. three replications nested within blocks, eight entries (main Sugars were quantified colorimetrically using potassium-ferricyanide plots), and six rows per main plot. Rows were 0.56 m apart and glucose-oxidase methods. Cattle grazing preferences among these and main plots were 3.35 by 6.7 m. tall fescue cultivars were related to the concentrations of total nonstructural carbohydrates (TNC) (r 2 ϭ 0.49, P Ͻ 0.05). Other sugar Harvesting and Sample Preparation fractions were not significantly related to grazing preference in this study. The nonstructural carbohydrate concentrations averaged over Vegetatively growing forage was clipped at a stubble height the entire study were glucose, 14; fructose, 5; sucrose, 40; fructan, 23; of 8 cm from randomly located 0.6-m sections of Rows 3 and insoluble starch, 24; and TNC, 129 g kg Ϫ1 . A forage selection criterion 4 in each plot. The forage in Block 1 was clipped on d 131, should include measures of the TNC because of their close relationship 165, 221, and 256 of 1993 and d 129, 164, 220, and 262 of 1994. to animal grazing preference.

Phylogenetic relationships of the grass family inferred from the sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA (rDNA) are generally in accord with the boundaries of the six commonly recognised subfamilies: Bambusoideae, Pooideae, Arundinoideae, Centothecoideae, Chloridoideae and Panicoideae. ITS phylogeny recognises the herbaceous bamboo allies, Streptochaeta and Pharus, as the basal taxa to all grasses. The core grass lineage is resolved into three major clades: the basal Bambusoideae is sister to the monophyletic Pooideae and the Panicoideae–Arundinoideae–Centothecoideae–Chloridoideae (PACC) clade. Several genera with uncertain taxonomic affinities, Lygeum, Nardus, Brachyelytrum, Diarrhena, Anisopogon, Ampelodesmos, and the tribe Stipeae, are all clustered with a broadly defined Pooideae, and may be the ‘missing links’ between the Pooideae and the Bambusoideae. Relationships of the PACC clade indicate that C4 photosynthesis evolved independently among and within the PACC subfamilies. ITS phylogeny of the grass family, and evidence from the chloroplast genome, cytogenetics, fossil records, biogeography, and plate tectonic theory, suggest that the origin of the grasses is probably ‘out of South America’.

Phylogenetic relationships of the Poaceae subfamily, Pooideae, were estimated from the sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. The entire ITS region of 25 species belonging to 19 genera representing seven tribes was directly sequenced from polymerase chain reaction (PCR)-amplified DNA fragments. The published sequence of rice, Oryza saliva, was used as the outgroup. Sequences of these taxa were analyzed with maximum parsimony (PAUP) and the neighbor-joining distance method (NJ). Among the tribes, the Stipeae, Meliceae and Brachypodieae, all with small chromosomes and a basic number more than x=7, diverged in succession. The Poeae, Aveneae, Bromeae and Triticeae, with large chromosomes and a basic number of x=7, form a monophyletic clade. The Poeae and Aveneae are the sister group of the Bromeae and Triticeae. On the ITS tree, the Brachypodieae is distantly related to the Triticeae and Bromeae, which differs from the phylogenies based on restriction-site variation of cpDNA and morphological characters. The phylogenetic relationships of the seven pooid tribes inferred from the ITS sequences are highly concordant with the cytogenetic evidence that the reduction in chromosome number and the increase in chromosome size evolved only once in the pooids and pre-dated the divergence of the Poeae, Aveneae, Bromeae and Triticeae.This paper reports factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.

Summary• An analysis of fructan structures, to increase the understanding of biosynthetic pathways and enzymology of fructan synthesis in root and leaf tissues of Lolium perenne is reported.• Fructan extracted from stubble of L. perenne plants was analyzed by high performance anion exchange chromatography and pulsed amperometric detection (HPAEC-PAD) using a new desalting technique. Structures of fructan isomers, separated up to DP16 (DP, degree of polymerization), were established by chromatographic elution times or by GC-MS.• Fructans of DP8 belonged essentially to three series: inulin series, inulin neoseries and the levan neoseries, which is/are different in glucose (terminal or internal) and linked fructose residues. High DP fructans (DP > 8) comprised 75% molecules with an internal glucose residue. They had some branch points although 1 and 6 kestotetraose could not be detected and the β (2 -6) linked fructose residues were 70 times more abundant than the β (2 -1) linked fructose residues. Roots, sheaths, leaf blades and elongating leaves accumulated similar fructans although amounts of both low and high, and types of low, DP fructans, differed.• It is proposed that fructans in L. perenne are synthesized via four enzymes: 1-SST (1-sucrose-sucrosefructosyl transferase), 1-FFT (1-fructan-fructanfructosyl transferase), 6G-FT (6-glucose-fructosyl transferase) and 6-FFT (6-fructanfructanfructosyl transferase) or 6-SFT (6-sucrose-fructanfructosyl transferase).

The savannas (cerrado) of south-central Brazil are currently subjected to frequent anthropogenic burning, causing widespread reduction in tree density. Increasing concentrations of atmospheric CO could reduce the impact of such frequent burning by increasing the availability of nonstructural carbohydrate, which is necessary for resprouting. We tested the hypotheses that elevated CO stimulates resprouting and accelerates replenishment of carbohydrate reserves. Using a factorial experiment, seedlings of a common Brazilian savanna tree, Keilmeyera coriacea, were grown at 350 ppm and 700 ppm CO and at two nutrient levels. To simulate burning, the plants were either clipped at 15 weeks or were left unclipped. Among unclipped plants, CO and nutrients both stimulated growth, with no significant interaction between nutrient and CO effects. Among clipped plants, both CO and nutrients stimulated resprouting. However, there was a strong interaction between CO and nutrient effects, with CO having a significant effect only in the presence of high nutrient availability. Under elevated CO, carbohydrate reserves remained at higher levels following clipping. Root total nonstructural carbohydrate remained above 36% in all treatments, so carbohydrate reserves did not limit regrowth. These results indicate that under elevated CO this species may be better able to endure the high frequency of anthropogenic burning in the Brazilian savannas.