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Abstract: Species of the genus Poa are taxonomically and genetically difficult to delineate owing to high and variable polyploidy, aneuploidy, and challenging breeding systems. Approximately 5% of the proposed species [...]

Stolon connection of clonal plants can translocate resources and signalling molecules between interconnected ramets to enhance resistance. Plants are well known to enhance leaf anatomical structure and vein density to respond to insect herbivory. Herbivory signalling molecules are transferred through vascular system to alert distant undamaged leaves, which is called systemic defence induction. Here, we investigated how clonal integration modulates leaf vasculature and anatomical structure of Bouteloua dactyloides ramets to cope with different levels of simulated herbivory. Ramet pairs were subject to six treatments, daughter ramets were exposed to three defoliation levels (0 %, 40 % or 80 % leaf removal) and their stolon connections to mother ramets were either severed or kept intact. Local 40 % defoliation increased vein density and adaxial/abaxial cuticle thickness, decreased leaf width and areolar area of daughter ramets. However, such effects of 80 % defoliation were much smaller. Compared with remote 40 % defoliation, remote 80 % defoliation increased leaf width and areolar area and decreased vein density of interconnected undefoliated mother ramets. Without simulated herbivory, stolon connection negatively affected most leaf microstructural traits of both ramets except from denser veins of mother ramets and more bundle sheath cells of daughter ramets. The negative effect of stolon connection on leaf mechanical structures of daughter ramets was ameliorated in the 40 % defoliation treatment, but not in the 80 % defoliation treatment. Stolon connection increased vein density and decreased areolar area of daughter ramets in the 40 % defoliation treatment. In contrast, stolon connection increased areolar area and decreased bundle sheath cell number of 80 % defoliated daughter ramets. Defoliation signals were transmitted from younger ramets to older ramets to change their leaf biomechanical structure. Clonal integration can adjust leaf microstructure of younger ramets according to the degree of herbivory stress, especially leaf vasculature. [ABSTRACT FROM AUTHOR]

Poa annua L. is a globally distributed grass with economic and horticultural significance as a weed and as a turfgrass. This dual significance, and its phenotypic plasticity and ecological adaptation, have made P. annua an intriguing plant for genetic and evolutionary studies. Because of the lack of genomic resources and its allotetraploid (2 n = 4 x = 28) nature, a reference genome sequence would be a valuable asset to better understand the significance and polyploid origin of P. annua. Here we report a genome assembly with scaffolds representing the 14 haploid chromosomes that are 1.78 Gb in length with an N50 of 112 Mb and 96.7% of BUSCO orthologs. Seventy percent of the genome was identified as repetitive elements, 91.0% of which were Copia- or Gypsy-like long-terminal repeats. The genome was annotated with 76,420 genes spanning 13.3% of the 14 chromosomes. The two subgenomes originating from Poa infirma (Knuth) and Poa supina (Schrad) were sufficiently divergent to be distinguishable but syntenic in sequence and annotation with repetitive elements contributing to the expansion of the P. infirma subgenome. [ABSTRACT FROM AUTHOR]

Poa is a complex genus taxonomically and genetically. As a result, relatively little information exists for this economically important genus with regards to reproductive mode and variability in chromosome number. We examined apomixis frequency and ploidy levels in 83 Poa accessions representing 33 species from the National Plant Germplasm System using flow cytometric techniques. In reproductive mode analysis, we analyzed at least three preparations of 50 seeds each from the accessions. In ploidy level analysis, at least three plants of each accession were analyzed. Sixty percent of the species had at least one apomictic or facultative apomictic accession; 40% were sexual. Thirty-three percent of the species had no sexual accessions. Autonomous apomixis was newly identified in P. bactriana and P. bulbosa in addition to it being previously reported in P. nervosa. Poa annua and P. trivialis were identified as obligate sexual, and P. nervosa as obligate apomictic. Two of four P. palustris accessions exhibited facultative apomixis. Ploidy levels among sexually reproducing Poa accessions ranged from 2n = 2x = 14 to 2n = 12x = 84, with most accessions between 2n = 3x = 21 to 2n = 8x = 56. Among apomictic accessions, ploidy levels ranged from 2n = 3x = 21 to 2n = 10x = 70, with most between 2n = 4x = 28 and 2n = 10x = 70. These results emphasize the wide variability in Poa, both among and within species.

Kentucky bluegrass (Poa pratensis L.), one of the most commonly grown turfgrasses in temperate regions, is being developed for possible commercial release with transgenic traits. The use of this technology raises risk assessment questions because P. pratensis is perennial, often apomictic, competitive in many habitats, and hybridizes with other Poa. To further understand the potential environmental impact of a transgenic P. pratensis, we measured intra- and interspecific pollen-mediated gene flow in field conditions from P. pratensis to other Poa. We used a wagon-wheel design with a glyphosate (N-phosphono methyl-glycine) resistant P. pratensis as a pollen donor and a pollen receptor plot at 0 m and plots at 13 and 53 m along six equally spaced vectors. Each receptor plot included accessions from 25 Poa species. Seedlings from the receptor plants were screened for resistance to glyphosate and potential hybrids verified by PCR and geuomic fingerprinting. Hybrids were found with P. arachnifera Torrey, P. interior Rydb., P. pratensis x P. secunda J. Presl, and three other P. pratensis entries, but did not occur with P. annua L., P. palustris L., P. trivialis L., or P. compressa L., among other species. Overall hybrid frequency was 0.048% and hybrid frequency at the 0-m distance was 0.53%. While apomixis in receptor plants and pollen competition likely reduced the number of hybrids, gene flow did occur but at low frequency and over short distances.

Using reduced-maintenance turfgrass as an alternative to current high-maintenance turfgrass species would conserve resources, reduce labor, and potentially reduce pollutants in the environment. CWG-R is an experimental population of crested wheatgrass [Agropyron cristatum (L.) Gaertn.] from Iran that has shown potential as a low-maintenance turf. The objective of this research was to estimate the genetic variation for turf traits within the CWG-R population when evaluated under a reduced-maintenance regimen. Ninety CWG-R clonal lines were established in 1998 near Logan, UT, as spaced-plant plots in a RCB design with four replicates. Maintenance of 50% E[T.sub.0] replacement, 97.74 kg of nitrogen [ha.sup.-1] [yr.sup.-1], and mowing at 7.62 cm was approximately 40% lower than typical for high-input Kentucky bluegrass (Poa pratensis L.) turf. Critical turf traits, including spring regrowth, season-long (March-October) and mid-summer (June-July) turf quality, color, and rhizomatous spread were evaluated in 1999 and 2000. Significant genetic variation among clonal lines was evident with broad-sense heritabilities of 0.65, 0.76, 0.45, and 0.76 for spring regrowth, season-long turf quality, color, and rhizomatous spread, respectively. Several clonal lines remained green throughout the summer months and maintained acceptable turf quality and color ratings during the critical mid-summer period. The high broad-sense heritability estimates within this population indicate potential for successful improvement of critical turf traits by phenotypic selection. These results indicate that that CWG-R could be an important low-maintenance turf-type crested wheatgrass germplasm., SIGNIFICANT LANDSCAPE ACREAGE that has been planted to high-maintenance turf could be replaced with low-maintenance turf species or cultivars (Wu and Harivandi, 1988). Low-maintenance turf is a relative term describing [...]

Archaeological work at Tintagel Island in Cornwall, England, has disclosed Mediterranean material from the 5th and 6th centuries. This is the first strong evidence suggesting Tintagel was an early trading center for Mediterranean cultures.

Poa annua L. is a turfgrass commonly found on golf course putting greens, as well as many other environments in temperate regions of the world. Although it can produce a very desirable putting surface, the species is usually considered a weed, in part because it is characterized by continuous flowering during the growing season. Flowering at the low mowing heights of a golf green, is detrimental to the putting quality of the green and the stress tolerance of the plants. However, many individuals of P. annua flower only in the spring. We conducted this inheritance study to investigate the genetic control of flowering pattern in four representative genotypes, then relate the information to the ecology of the species in golf course environment, and propose improvements for A annua breeding. One annual and three perennial tetraploid P. annua genotypes were crossed in all combinations. [F.sub.1], [F.sub.2], and in most cases [F.sub.3], populations were grown and observed in field or greenhouse conditions over 1 to 3 yr. Each plant was rated for flowering pattern during the growing season. A genetic model involving one locus and two alleles with continual flowering completely dominant to seasonal flowering is proposed for control of flowering pattern based on [F.sub.2] populations exhibiting 3:1 ratios of continual to seasonal flowering pattern types. Three distinct [F.sub.3] populations are produced from [F.sub.2] progeny: all continual flowering, all seasonal flowering, and segregating 3:1 continual to seasonal, similar to the [F.sub.2] generation. There may also be evidence of modifying loci and maternal effects in some populations. This simple inheritance may explain the high heritability of flowering traits and rapid evolution of plant types in golf course turfgrass. Qualitative inheritance also provides the opportunity for efficient selection of desirable seasonal flowering P. annua plants., Poa annua is a highly variable grass species that grows on all continents of the world including Antarctica (Scott, 1987) and is found usually in association with human activity. It [...]

Poa annua L. is a common turfgrass species in golf turf. The species is usually considered to be annual because of characteristics including continuous flowering throughout a growing season. In reality, the species exhibits a wide diversity of flowering habits from continual to seasonal, or only in spring. In efforts to study the flowering physiology of the species and to improve hybridization work, we initiated experiments to determine environmental conditions for floral induction in one P. annua var. annua and four P. annua var. reptans genotypes. Growth chamber and greenhouse environments were used to test (i) the minimum length of time needed for vernalization, (ii) the effective temperature for vernalization, and (iii) whether juvenility exists with regard to vernalization. Poa annua var. reptans genotypes were vernalized after 10 to 12 wk at 4 and 8C, but not at 12C. Poa annua var. annua did not respond to vernalization treatments. Poa annua var. reptans also exhibited variation in juvenile period ranging from 25 d to greater than 35 d after germination. Incomplete vernalization resulted in inflorescence development, but flowers were deformed. Vernalization requirements differed between var. annua and var. reptans genotypes, as well as among var. reptans. This information can be used to improve P. annua breeding, as well as to investigate the diversity within this species., Poa Annua is usually described as an annual A (Sprague and Burton, 1937; Wells, 1974; Hutchinson and Seymour, 1982), especially in the numerous trade journals. These annual forms (P. annua [...]

Poa annua L. turf on golf courses is often criticized for persistent flowering, even under low mowing heights. But in fact, P. annua genotypes exhibit wide variation in their flowering characteristics. This study was conducted in greenhouse and growth chamber environments during 1994 and 1995 at the University of Minnesota to test for photoperiod requirements for floral induction and development. The five P. annua genotypes studied ranged from a true annual type to strongly perennial forms. Photoperiod effects were investigated without prior cold treatment, during cold treatment, and after cold treatment requirements had been satisfied. Cold treatments were 4 ° C for 12 wk. The annual type (UM2283) was not responsive to cold treatments and is day-neutral. In the absence of a cold treatment, one perennial genotype (UM234) was induced in long days (16 h), two perennials (UM42, UM117) were induced to flower in short days (8 h), and one perennial (UM184) was not induced in either. Ninety minute night breaks during a 16-h dark period were effective in producing the long-day responses. Photoperiod did not affect the cold treatment response at 4 ° C Floral development after 4 ° C cold treatment was generally favored by long days (16 h), but is genotype dependent. Photoperiodism is associated with perenniality in P. annua, and may be important in the selection pressures caused by management practices golf course environments. Selection for longer cold treatment requirements and less induction in short days (8 h) may reduce the amount of flowering a genotype would exhibit in a turf stand., Poa annua is common in turfs in temperate regions A and around the world. However, it is usually considered a weed, especially on golf courses, because of the nearly continuous [...]