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Kentucky bluegrass (Poa pratensis L.) is a widely used, high-quality, sod-producing turfgrass. To maintain an acceptable level of quality and function requires irrigation in the semiarid regions of the western United States. Landscape water use, however, is coming under increased scrutiny, and reducing water inputs is a goal of many municipalities. To identify Poa germplasm that maintains green color under deficit irrigation over summer seasons, this study was designed to evaluate the percent of green cover of 24 Kentucky bluegrass cultivars, accessions (including core collections), and other Poa species. Cultivars generally had a higher percent green cover in spring and fall, while several accessions and old U.S. cultivars showed higher green cover during summer months. Other Poa species did not have percent green cover values above any cultivars and as a group consistently performed the lowest. Core collections of Kentucky bluegrass, aimed at representing overall variability of the species with fewer accessions, had variance estimates equal to or higher than the overall group of accessions. Seven cultivars and accessions consistently had higher percent green cover than the Midnight cultivar check during the August data collection dates, highlighting the potential to improve Kentucky bluegrass green cover over summer seasons under deficit irrigation. [ABSTRACT FROM AUTHOR]

Germination of five turfgrass species ['Barrister' kentucky bluegrass (Poa pratensis L.), 'Barvado' tall rescue (Festuca arundinacea Schreb.), 'Premier II' perennial ryegrass (Lolium perenne L.), 'Bargusto' bermudagrass (Cynodon dactylon L. Pers.), and 'Sea Spray' seashore paspalum (Paspalum vaginatum O. Swartz)] from coated (ZEBA® cornstarch coating; Absorbent Technologies Inc., Beaverton, OR) and uncoated seeds was evaluated on both filler paper and agar. Final germination percentage (FGP) and germination rate (GR) were determined at salinity levels of 0.6 (tap water, control), 2.2 (saline groundwater from a local shallow aquifer), and 7.0, 12.5, and 22.5 dS·m-1 [sodium chloride and calcium chloride (1:1, w:w) dissolved in tap water]. Final germination percentage for kentucky bluegrass, perennial ryegrass, and tall fescue was greater in agar at all salinity levels but was unaffected by the medium at any of the salinities except for 7 dS·m-1 for bermudagrass and seashore paspalum. Coated seashore paspalum and coated perennial ryegrass seed exhibited greater germination than uncoated seed at four of the five salinity levels. Seed coating had no effect on FGP of bermudagrass at any salinity level and coated kentucky bluegrass seed showed reduced germination at 0.6 and 7.0 dS·m-1. Final germination percentage for seashore paspalum improved from 22% to 54% at 12.5 dS·m-1 and from 8% to 20% at 22.5 dS·m-1 when coated seed was used instead of uncoated seed. Germination rates were unaffected by salinity levels ranging from 0.6 to 12.5 dS·m-1 and were higher on agar (10%/day) than on paper (8%/day). Our study suggests that the choice of medium can influence the outcome of germination tests and that results can also vary depending on the salinity level tested and whether the seed are coated. [ABSTRACT FROM AUTHOR]

Broad concerns over water shortages and drought where irrigated urban landscapes are common in high desert regions have focused attention on drought tolerance of turfgrass species. We investigated the physiological responses of kentucky bluegrass (KBG) and tall fescue (TF) under a prolonged drought under high desert conditions. The experimental design was a split plot with three replicates. Two irrigation treatments as a whole plot--well-watered and no water--were applied to subplots of 'Midnight' KBG and 'Gazelle' TF. Stomatal conductance (gs), canopy temperature, and predawn leaf water potential were measured over two seasons. KBG gs and leaf water potential decreased faster and to a greater extent than TF in response to soil drying, and KBG was in complete dormancy and brown within 5 weeks after cessation of irrigation. By contrast, TF maintained a green canopy throughout the drought periods, in the nowater plots, TF appeared to consume water from the deepest measured soil profiles (80- to 100-cm depth), whereas KBG used most of the water in the 50- to 60-cm depths. When watered for recovery in late summer, KBG plots were mostly green within 3 weeks after rewatering. The surface temperature of the well-watered plots was 6-13 °C cooler than the no-water plots and TF showed 5-7 °C lower temperature than KBG in no-water plots. TF is suitable for deep soil, exploiting a larger volume of water to avoid drought, whereas KBG's rapid drought avoidance would likely perform better in shallow landscape soils under drought. [ABSTRACT FROM AUTHOR]

Field experiments were conducted to assess the influence of plant growth and amendment addition on phytostabilisation of copper (Cu), lead (Pb), manganese (Mn) and zinc (Zn) along highway soil in southwest British Columbia, Canada. The plant species tested were Lolium perenne L (perennial rye grass), Festuca rubra L. (creeping red fescue) and Poa pratensis L. (Kentucky blue grass) and the amendments, lime and phosphate. The treatment efficiencies were assessed during different seasons as a completely randomized factorial experiment in split plot design. The research tasks involved: (1) quantifying the seasonal extent of metal accumulation in soil and assessing the seasonal impact on metal speciation for different soil amendments and plant species; (2) determining seasonal accumulation differences between sampling periods in plant parts; and (3) assessing the influence of root-soil interactions on metal dynamics. The amendments decreased the exchangeable fraction and plant uptake of all four metals. The lowest mobile fractions (exchangeable and carbonate bound) were found in soils growing Festuca for Cu, Lolium for Mn and a Lolium/Poa/Festuca combination for Pb and Zn. Metal accumulation and metal dynamics in the rhizosphere soil are compared with those of the bulk soil. The final outcome was the development of a remediation strategy for all four metals involving suitable plants and amendments and incorporating seasonal and rhizosphere influences. [ABSTRACT FROM AUTHOR]

Over the past 10 years, rust diseases have become increasingly prevalent on certain cultivars of Kentucky bluegrass. This pattern suggests that new races or new species of rust fungi may have emerged. To test this hypothesis, 66 samples of turfgrass rust fungi collected from across the United States were evaluated based on sequences of the internal transcribed spacer (ITS)-5.8S rDNA region. Phylogenetic analysis revealed three species: Puccinia coronata, P. graminis, and P. striiformis, comprising 67, 28, and 5% of the samples, respectively. P. coronata was frequently found in association with Kentucky bluegrass, a host-pathogen relationship that has not been previously reported. Comparison of molecular analyses with the use of standard field identification techniques-host association and pustule pigmentation-showed that 58% of the Kentucky bluegrass samples would have been incorrectly diagnosed using nonmolecular criteria. To avoid such misidentifications, a real-time polymerase chain reaction diagnostic protocol was developed for turfgrass-associated P. graminis, P. coronata, and P. striiformis using ITS sequences. Accurate, reproducible, species-specific identifications were made using as few as 50 to 150 urediniospores, even in mixed infections. This study represents the first DNA-based evaluation of turfgrass rust fungi and provides a quick and reliable sequence-based protocol as an alternative to less reliable field-based identification techniques. [ABSTRACT FROM AUTHOR]

Abstract: Female sterile plants are ideal for isolating genes involved in megasporogenesis and for investigating gene functions. Engineered female and male sterilities in plants have been considered as a way to reduce the potential of invasive species by eliminating seed set and to prevent gene flow between genetically modified species. A dwarf mutant ‘PM2’ induced by carrying ‘Nassau’ Kentucky bluegrass seeds to outer space lost the ability to produce seeds under either field conditions or artificial flower induction, whereas the untreated control was normal. Comparative study of microspore, macrospore, and embryo sac at different developmental stages along with controlled pollination showed that the PM2 mutant is likely both male and female sterile. The apoporous embryo development in PM2 aborted at globular stage prior to coleoptile formation. Multiple genes may be involved in the mutation based on the evidence observed from the morphology and anatomy of the mutant. [Copyright &y& Elsevier]

An increasing amount of reclaimed water is being used in turfgrass management; however, reclaimed water is often high in total dissolved salts and can result in salt stress injury and poor turf quality. The objective of this study was to use an overhead irrigated greenhouse screening technique to identify Kentucky bluegrass (Poa pratensis L.) cultivars with increased salinity tolerance, using growth parameters and physiological measurements. Salt treatments were applied using an overhead sprinkler system. Twenty-four Kentucky bluegrasses and Texas bluegrass (Poa arachnifera Torr.) x Kentucky bluegrass hybrids were established in 100% sand tanks and evaluated at a control (1 dS m-1) and three salinity concentrations (3, 6, and 9 dS m1) for a total of 10 wk. Plants were arranged in a split plot design with three replications. Percent green ratings and digital images were collected weekly and clipping weights were collected biweekly. Root and shoot weights were taken at the end of the study. Significant differences were observed between salinity treatments and cultivars. The cultivars Eagleton, Moonshadow, Fairfax, Cabernet, and Liberator exhibited the most salt tolerance, having the least decrease in growth parameters compared to the control plants (1 dS m-1), while cultivars Baron, A0384, and A03-TB246 were the most salt sensitive when compared to control plants. Relative water content and photochemical efficiency were useful to quantify physiological differences between tolerant and susceptible cultivars. [ABSTRACT FROM AUTHOR]

We describe a new Epichloë species found in symbiosis with Poa pratensis ssp. pratensis in Liyang, China. Stromata characteristic of Epichloë spp. were present on some of the reproductive tillers of individual host grasses. Only three of the 98 stromata observed on field plants became orange and produced perithecia. Phylogenetic analyses based on sequences of tubB and tefA indicated that this Epichloë sp. was an interspecific hybrid related to both E. yangzii and members in the E. typhina complex clade (ETC). Allele-1 of tefA and tubB grouped in the E. bromicola/E. yangzii clade; allele-2 of these two genes clustered in a distinct subclade in the ETC. This is the first report of an Epichloë species that has interspecific hybrid origins. We propose the name Epichlog liyangensis Z. Wang, Y. Kang et H. Miao, sp. nov. for this species. [ABSTRACT FROM AUTHOR]

An in situ study (Exp. 1) using 4 ruminally cannulated steers (343 ± 11 kg BW) in a completely randomized design was used to compare ruminal degradation characteristics of low-quality cool-season (C3; Kentucky bluegrass straw; Poa pratensis; 6.3% CP; DM basis) and warm-season (C4; tallgrass prairie; 5.7% CP; DM basis) forage. Four ruminally cannulated steers (252 ± 8 kg BW; Exp. 2) and 4 wethers (38 ± 1 kg BW; Exp. 3) were used in two, 2 × 2 factorial design experiments to determine the influence of supplemental CP (CPSupp; soybean meal; 0.09 and 0.19% BW, CP basis, for steers and lambs respectively) on nutrient intake and digestion of C3 and C4 forages. Steers and wethers were allotted to separate 4 × 4 Latin squares that ran simultaneously with 20-d periods. In Exp. 1, C3 had greater A fractions (fraction of total pool disappearing at a rate too rapid to measure) and effective degradability of DM and NDF compared with C4 (P < 0.01). Also, C3 had a greater (P < 0.01) A fraction and effective degradability of N while the C fraction (fraction of total pool unavailable in the rumen) was less (P < 0.01) compared with C4. Consequently, rumen degradable protein accounted for 84.7% of total CP in C3 as compared to 66% for C4 (P < 0.01). In Exp. 2, a CPSupp × forage interaction (P < 0.01) was noted for forage and total DMI, with CPSupp increasing intake of C4 by 47%, and C3 forage by only 7%. Dry matter digestibility responded similarly with a CPSupp × forage interaction (P = 0.05; CPSupp increased digestibility 21% with C4 and 9% with C3 forage). Also, CPSupp × forage interactions were noted for ruminal liquid retention time (P = 0.02; CPSupp decreased retention 3.6 h with C4 and only 0.6 h with C3 forage) and particulate passage rate (P = 0.02; CPSupp increased passage 46% with C4 and 10% with C3 forage). As in Exp. 2, a CPSupp × forage interaction (P = 0.01; CPSupp increased digestibility 18% with C4 and 7% with C3 forage) was observed with DM digestibility in Exp. 3. In contrast, only N balance (P < 0.01) and N digestibility (P < 0.01) were affected by CPSupp. These data suggest that intake and digestion of low-quality C3 and C4 forages by ruminants are not similar and, more importantly, the physiological response of ruminants to protein supplementation of low-quality forage is dependent on forage type. [ABSTRACT FROM AUTHOR]

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Prairie junegrass (Koeleria macrantha) is a perennial, cool-season, native grass that has shown potential for use as a turfgrass species in the northern Great Plains; however, limited information is available on its salt tolerance, in this study, salinity tolerance of four junegrass populations from North America (Colorado, Minnesota, Nebraska, and North Dakota) and two improved turf-type cultivars from Europe ('Barleria' and 'Barkoel') was evaluated and compared with kentucky bluegrass (Poa pratensis), perennial ryegrass (Loliumperenne), sheep rescue (Festuca ovina), hard fescue (F. brevipila), and tall fescue (F. arundinacea). Salinity tolerance was determined based on the predicted salinity level causing 50% reduction of final germination rate (PSLF) and daily germination rate (PSLD) as well as electrolyte leakage (EL), tissue dry weight (DW), and visual quality (VQ) of mature plants. All populations of prairie junegrass showed similar salt tolerance with an average of PSLF and PSLD being 7.1 and 5.3 g⋅L-1 NaCl, respectively, comparable to kentucky bluegrass and hard and sheep fescue but lower than tall fescue and perennial ryegrass. Larger variations were observed in VQ in the junegrasses compared with EL and DW, in which 'Barleria' from the European population showed the highest VQ, following two salt-tolerant grasses, tall fescue and sheep fescue. Nebraska population was the least salt-tolerant within the species but still exhibited similar or higher tolerance than kentucky bluegrass and perennial ryegrass cv. Arctic Green. Overall, junegrass was more salt-sensitive during germination but more tolerant to salinity when mature. Salinity tolerance of junegrass may be further improved through turfgrass breeding because salinity tolerance varied in different populations. [ABSTRACT FROM AUTHOR]

The speed at which a baseball travels after impact with a playing surface has been referred to as playing surface pace. Little information is available regarding the effects of varying construction and maintenance practices on the pace of baseball playing surfaces. Research was conducted to evaluate the effects of construction and maintenance practices on a non-turfed basepath, Kentucky bluegrass (Poa pratensis L.) turf, and six synthetic turf surfaces. Factors evaluated on the non-turfed basepath included soil compaction at installation, surface scarification, and topdressing with a soil conditioner (calcined clay). The effects of cutting height and thatch thickness were evaluated on Kentucky bluegrass, while the effects of simulated traffic and grooming were evaluated on synthetic turf. On the non-turfed basepath, increasing soil compaction yielded increases in surface pace. Calcined clay topdressing and increasing scarification depth did not affect surface pace. On Kentucky bluegrass, varying cutting height and thatch thickness levels had no effect on surface pace. On synthetic turf, increases in simulated traffic resulted in slight increases in pace. Surface pace measurements on synthetic turf were less variable than those made on natural turfgrass. The results indicate that the pace of commonly used baseball playing surfaces is not easily altered with minimally invasive maintenance procedures and should be addressed at construction or during aggressive renovations. [ABSTRACT FROM AUTHOR]

Salinity tolerance ofl2 turfgrasses in four groups, creeping bentgrass (Agrostis stolonifera L.), fescues (Festuca spp.), kentucky bluegrass (Poa protests L.), and alkaligrass [Puccinellia distans (Jacq.) Parl.], was evaluated using three germination methods. Seeds were germinated on 1% agar medium, on germination paper, or in a hydroponic system under salinity levels of 0,5,10,15, or20g⋅L-1 NaCl. Germination rate and seedling growth of each grass were determined. Salinity reduced the final germination rate (FGR), daily germination rate (DGR), and seedling leaf area (LA) in all tests. On agar medium, no significant difference in salinity tolerance was observed among the four turf groups; however, 'Turf Blue' kentucky bluegrass with a corn starch-based coating (coated 'Turf Blue') showed a significant higher salinity tolerance than the uncoated one. Using germination paper, creeping bentgrass required the highest salinity level to cause 50% reduction in FGR followed by alkaligrass, fescues, and kentucky bluegrass. Kentucky bluegrass required the lowest salinity level (9.5 g⋅L-1) to reduce DGR by 50%. With the hydroponic system, alkaligrass required a salinity level of 26.3 g⋅L-1 to reduce FGR by 50%, the highest among the four groups. Alkaligrass showed again the highest salinity tolerance with an average of 12.7 g⋅L-1 needed to reduce LA by 50%. Among the grasses, coated 'Turf Blue' kentucky bluegrass, 'Declaration' creeping bentgrass, and 'Fults' alkaligrass showed the highest salinity tolerance when evaluated on agar medium, on germination paper, or in the hydroponic system, respectively. The present study determined the salinity tolerance of 12 turfgrasses at seed germination and early seedling growth stages and showed that the germination method was a factor affecting the evaluation result and it should be considered in a seed germination test of turfgrass for salinity tolerance. [ABSTRACT FROM AUTHOR]

Despite increasing interest in the patterns of trace gas emissions in terrestrial ecosystems, little is known about the impacts of climate change on nitrous oxide (NO) fluxes. The aim of this study was to determine the importance of the three main drivers of climate change (warming, summer drought, and elevated CO concentrations) on NO fluxes from an extensively managed, upland grassland. Over a 2-year period, we monitored NO fluxes in an in situ ecosystem manipulation experiment simulating the climate predicted for the study area in 2080 (3.5°C temperature increase, 20% reduction in summer rainfall and atmospheric CO levels of 600 ppm). NO fluxes showed significant seasonal and interannual variation irrespective of climate treatment, and were higher in summer and autumn compared with winter and spring. Overall, NO emissions showed a positive correlation with soil temperature and rainfall. Elevated temperature had a positive impact on mean annual NO fluxes but effects were only significant in 2007. Contrary to expectations, neither combined summer drought and warming nor the simultaneous application of elevated atmospheric CO concentrations, summer drought and warming had any significant effect on annual NO fluxes. However, the maximum NO flux rates observed during the study occurred when elevated CO was combined with warming and drought, suggesting the potential for important, short-term NO-N losses in enriched CO environments. Taken together, our results suggest that the NO responses of temperate, extensively managed grasslands to future climate change scenarios may be primarily driven by temperature effects. [ABSTRACT FROM AUTHOR]

Abstract: Poa pratensis, a type species for the grass family (Poaceae), is an important cool season grass that accumulates fructans as a polysaccharide reserve. We studied fructan contents and expression of candidate fructan metabolism genes during cold acclimation in three varieties of P. pratensis adapted to different environments: Northern Norway, Denmark, and the Netherlands. Fructan content increased significantly during cold acclimation and varieties showed significant differences in the level of fructan accumulation. cDNA sequences of putative fructosyltransferase (FT), fructan exohydrolase (FEH), and cold acclimation protein (CAP) genes were identified and cloned. In agreement with a function in fructan biosynthesis, transcription of a putative sucrose:fructan 6-fructosyltransferase (Pp6-SFT) gene was induced during cold acclimation and fructan accumulation in all three P. pratensis varieties. Transcription of putative PpFEH and PpCAP genes was also induced by cold acclimation; however, transcription of these two genes was several-fold higher in the variety from Norway compared to the other two varieties. The results presented here suggest that Pp6-SFT is involved in fructan biosynthesis in P. pratensis. FEHs have previously been suggested to be involved in fructan biosynthesis and freezing tolerance, and induced expression of PpFEH during fructan accumulation could also suggest a role in fructan biosynthesis. However, based on the different PpFEH transcription rates among varieties and similar expression of PpFEH and PpCAP, we suggest that PpFEH is more likely to be involved in mediating freezing tolerance, e.g., by regulating the cell osmotic potential through fructan degradation. [ABSTRACT FROM AUTHOR]

Dynamics of vegetation is more and more affected by human activities. The more human society changes or the more and more systems are being built, the more important it is to understand how human activities affect succession. Human dominance of the systems covers a great variety of the management or control. The evolution and succession of the vegetation is developing permanently as a result of the development law and human impact, the development of the vegetation cover being analysed by the scientists from different countries. Through this work we are trying to do an appreciation on the effect of restriction of mowing and grazing on a permanent grassland of Poa pratensis L. The study was developed in the Surducului Hills that are placed at the base of the Poiana Rusca Mountains, at the east of the Bega river terraces. The observations were done on permanent grassland during five years (2006-2009). The vegetation was determined using the linear point-quadrate method, the results being calculated on the base of the botanical surveys. The geographical coordinates were determined with the help of a GPS receptor Magellan. The statistical method used was the correlation analysis. In conclusion we can say that the dynamics of the vegetation is in an intermediate evolution state created by the disturbances connected with the mowing and grazing; the underexploitation and the microclimate created by the presence of the Surduc Lake has determined the trend of the species from the point of view of the FS%; there is a negative correlation between VP and FS% of the legumes and between VP and FS% of the species belonging to other botanical families isn't any correlation. Thus, our purpose is to continue this study for the applying and implementing of some restoration measures for the increase of the quantity and quality of the yield obtained on the surface of these permanent grasslands. [ABSTRACT FROM AUTHOR]

Foliar accumulations of gaseous elemental mercury (GEM) were measured in three plant species between nominal temperatures of 10 and 30 °C and nominal irradiances of 0, 80, and 170 W m-2 (300 nm-700 nm) in a 19 m3 controlled environment chamber. The plants exposed were as follows: White Ash (Fraxinus americana; WA); White Spruce (Picea glauca; WS); and Kentucky Bluegrass (Poa partensis; KYBG). Foliar enrichments in the mercury stable isotope (198Hg) were used to measure mercury accumulation. Exposures lasted for 1 day after which the leaves were digested in hot acid and the extracted mercury was analyzed with ICPMS. Resistances to accumulative uptake by leaves were observed to be dependent on both light and temperature, reaching minima at optimal growing conditions (20 °C; 170 W m-2 irradiance between 300-700 nm). Resistances typically increased at lower (10 °C) and higher (30 °C) temperatures and decreased with higher intensities of irradiance. Published models were modified and used to interpret the trends in stomatal and leaf interior resistances to GEM observed in WA. The model captured the experimental trends well and revealed that stomatal and internal resistances were both important across much of the temperature range. At high temperatures, however, stomatal resistance dominated due to increased water vapor pressure deficits. The resistances measured In this study were used to model foliar accumulations of GEM at a northern US deciduous forest using atmospheric mercury and climate measurements made over the 2003 growing season. The results were compared to modeled accumulations for GEM, RGM, and PHg using published deposition velocities. Predictions of foliar GEM accumulation were observed to be a factor of 5-10 lower when the temperature and irradiance dependent resistances determined in this study were used in place of previously published data. GEM uptake by leaves over the growing season was shown to be an important deposition pathway (2.3-3.7 μg m-2 of one-sided leaf area; OSLA) when compared to total mercury wet deposition (1.2 μg m-2 OSLA) and estimates of reactive mercury dry deposition (0.1-6μg m-2 OSLA). Resistance-Temperature-Irradiance relationships are provided for use in models. [ABSTRACT FROM AUTHOR]

Changes in fatty acid composition and saturation levels may be involved in leaf tolerance to dehydration during drought stress and recovery on rewatering. The objective of this study was to compare changes in compositional and saturation levels of leaf fatty acids between two cultivars of Kentucky bluegrass (Poa pratensis L.) contrasting in drought tolerance in response to drought stress and rewatering. Drought-tolerant `Midnight' and sensitive `Brilliant' were maintained well-watered (control) or subjected to drought for 15 d by withholding irrigation and then rewatered in a growth chamber. Compared to Brilliant, Midnight maintained higher turf quality, leaf photochemical efficiency, relative water content, and membrane stability expressed as electrolyte leakage during drought stress. Following rewatering, Midnight recovered more rapidly in each parameter than Brilliant. The degree of fatty acid unsaturation decreased in both cultivars during drought stress, and the decrease was less pronounced and occurred later in Midnight. Fatty acid unsaturation level resumed to the control level in Midnight leaves, but did not fully recover in Brilliant after rewatering. The alteration in fatty acid unsaturation level induced by drought and rewatering were mainly due to the changes in the composition of linolenic acids (18:3), linoleic acids (18:2), palmitic acids (16:0), and stearic acids (18:0). Our results suggest that leaf dehydration tolerance and postdrought recovery in Kentucky bluegrass was associated with their ability to maintain relative higher proportion and level of unsaturated fatty acids, particularly linolenic acids and linoleic acids. [ABSTRACT FROM AUTHOR]

Understanding turfgrass response to silicon (Si) application under salinity conditions is important to find a way to improve turfgrass salt tolerance for turf management. The objective of the study was to investigate effects of increasing amendment concentrations of Na2SiO3 on turf growth and distribution of Na+ and K+ in seedlings of kentucky bluegrass (KBG) (Poa pratensis L.) under salinity stress. This growth chamber experiment was consisted of a control (no salinity, and no Si) and five Si amendment treatments (0, 0.24, 0.48, 0.72, and 0.96 g Si/kg saline soil) under 10 g⋅kg-1 salinity conditions. Seed germination rate was significantly increased after 12 d under 0.48 g⋅kg-1 Si treatment. Plant height and canopy coverage were increased under 0.72 g⋅kg-1 Si treatment after 40 and 44 d of treatment, respectively, and tiller number was increased under 0.96 g⋅kg-1 Si treatment compared with 0 Si under saline conditions. With the supplement of Si at 0.48 to 0.96 g⋅kg-1, the ratio of Na+/K+ in shoots was decreased and individual leaf area was increased compared with 0 Si under saline conditions. The increase in individual leaf area was mainly the result of the increase in the leaf blade length. The concentration of K+ in shoots was significantly increased, whereas the concentrations of Na+ in roots were significantly decreased under all Si amendment treatments. The content of K+ was higher in shoots than in roots, but the ratio of Na+/K+ in roots was higher than in shoots in all Si amendment treatments. The results indicate that under saline conditions, Si induced the transfer of K+ from roots to shoots but inhibited the absorption and transfer of Na+, which may contribute to better turf quality and growth with Si treatment under saline conditions. [ABSTRACT FROM AUTHOR]

The effects of pipeline construction and reclamation techniques on the restoration of rough fescue plant communities following pipeline construction in southwestern Alberta, Canada were evaluated after 7–40 years. The pipeline construction right-of-way (ROW) sites varied from no recovery of rough fescue grassland to moderate recovery. The ROW sites had a higher proportion of introduced grasses and forbs, less topsoil, and poorer rangeland health than the adjacent undisturbed grassland. Within the ROW sites, less topsoil was present on those with larger diameter pipe and which had topsoil fully stripped from the ROW during construction. Introduced grasses, Festuca ovina (sheep fescue) and Poa compressa (Canada bluegrass), succeeded in establishment following seeding and persisted for at least 40 years. Poa pratensis (Kentucky bluegrass) dominated many of the ROW sites. Contributing factors to moderate recovery of rough fescue grassland were related to post-growing season pipeline construction, ideally, between August and March, summer or fall seeding, and minimum disturbance trench-only stripping. Reclamation practices appeared more important than time since restoration in the restoration of rough fescue grassland. [Copyright &y& Elsevier]

Kentucky bluegrass (Poa pratensis L.) is an important facultative apomictic temperate perennial grass species used for both forage and cultivated turf. Through apomixis, this species is able to propagate diverse and odd ploidy levels, resulting in many genetically distinct phenotypes. A wide range of diverse cultivars and accessions of kentucky bluegrass have been previously characterized based on common turf performance or morphological characteristics as well as by random amplified polymorphic DNA (RAPD) markers. Although previous characterization efforts have provided valuable information, the use of both morphological characteristics and RAPD markers for genetic diversity analysis has limitations. In the current report, we developed and characterized 88 novel microsatellite markers for kentucky bluegrass. Polymorphism for each marker was assessed in 265 kentucky bluegrass cultivars, experimental selections, collections, and hybrids. The number of alleles for individual microsatellites ranged from four to 81 with an average of 38.3 alleles per simple sequence repeat. These polymorphic microsatellite markers would be useful tools for investigating genetic diversity, creation of genetic linkage maps, assessment of levels of apomixis in cultivars and experimental varieties, and identification of aberrant progeny in apomictic kentucky bluegrass breeding programs. [ABSTRACT FROM AUTHOR]

Abstract: Decline of leafy spurge (Euphorbia esula) in the northern Great Plains of the US is generally viewed as a success story for biological control, but quality of the vegetation that survived the infestation is key to recovery of ecosystem function. In addition, effects of other invasive species, notably cool-season exotic grasses, must be taken into account. Objectives of this study were (1) to evaluate direction and significance of changes in biomass of native and exotic grasses, forbs, and leafy spurge and in plant species composition following control of leafy spurge by flea beetles and (2) to evaluate the relative effects of leafy spurge and exotic grasses on biomass of native grasses, biomass of forbs, and richness of native species. We monitored species composition (1998–2003 and 2008) and biomass (2000, 2002, 2003 and 2008) of these groups on spurge-infested and noninfested permanent plots at three sites with unbroken prairie sod in North Dakota, USA. We found little evidence, in terms of species richness or biomass of native grasses or forbs, that leafy spurge was being replaced by desirable native species, although desirable as well as weedy and exotic species were characteristic of 2008 vegetation at all three sites. Structural equation models revealed that leafy spurge had temporally intermittent negative effects on forb biomass and species richness, but no effects on native grasses. In contrast, exotic grass had consistently strong, negative effects on native grass biomass, as well as stronger negative effects than leafy spurge on native species richness. Although substantial native plant diversity remains at these sites, exotic grasses pose an important threat to these crucial building blocks of native prairie ecosystems. [Copyright &y& Elsevier]

Apical meristems of multiple shoots produced from axenic seedlings of Kentucky bluegrass ( Poa pratensis L.) were used for Agrobacterium tumefaciens-mediated transformation. Transformation parameters were optimized for concentration of bacterial cells, duration of infection, and vacuum infiltration. The highest transformation frequency (1.42%) was obtained by infection with Agrobacterium suspension of OD600 = 0.6 for 5 min, under a negative pressure of 0.5 × 105 Pa. After co-cultivation, the herbicide-resistant plants were rooted and transplanted into flowerpots. Transgenic plants were confirmed by polymerase chain reaction (PCR) assay and Southern blot analysis. Using this transformation system, the betA gene encoding choline dehydrogenase and mutant als gene encoding the enzyme acetolactate synthase were introduced into three Kentucky bluegrass cultivars. [ABSTRACT FROM AUTHOR]

Six cultivars or selections of kentucky bluegrass (Poa pratensis L.) were grown outdoors from vegetative clones in a gravelly sand medium from Apr. to Sept. 2005 in Riverside, CA, at soil water salinities ranging from 2 to 22 dS·m-1. Cultivars Baron, Brilliant, Cabernet, Eagleton, Midnight, and the selection A01-856, a 'Texas' x kentucky bluegrass hybrid (P. arachnifera x P. pratensis), were evaluated for salt tolerance based on relative and absolute cumulative biomass production, growth rates, leaf chloride concentration, and hyperspectral ground-based remote sensing (RS) canopy reflectance measurements. Remotely sensed indices were linearly correlated with absolute biomass production. Three variations of a Normalized Difference Vegetation Index (NDVIred, NDVIprotein, and NDVIinfra) decreased with increasing salinity-induced changes in grass canopies. An index based on the red-edge inflection point increased (became less negative) with increasing salinity. A Floating Water Band Index decreased with decreased leaf moisture content related to increasing salinity but did not discriminate between cultivars. Shoot spreading rate and NDVIinfra were both related to shoot chloride concentration differences among the kentucky bluegrass (Poa pratensis L) (KBG) cultivars or selections. In theory, non-destructive RS monitoring of above-ground turf development, including NDVIinfra, coupled with measurement of leaf chloride concentrations could be useful in turf salt tolerance breeding programs. Salt tolerance rankings among the KBG cultivars varied depending on the evaluation methods and selection criteria used. Based on absolute and relative biomass, growth rate, and RS, cultivars Baron, Brilliant, and Eagleton were rated as more salt-tolerant than 'Cabernet', 'Midnight', and AO1-856. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the importance of protein synthesis during germination of white clover ( Trifolium repens) and Kentucky bluegrass ( Poa pratensis) and to assess the impact of osmopriming on seed germination in the presence of cadmium. Cycloheximide (Cx, 20 and 100 μM), a translation inhibitor, delayed germination and reduced final germination percentage in both species, although to a higher extent in P. pratensis than in T. repens. This suggests that in white clover, some proteins involved in reserve mobilisation and metabolic activation were already present in mature seeds. Actinomycin-D (Act-D; 20 and 100 μM) and α-amanitin (α-Am 20 μM), both inhibitors of transcription, did not reduce P. pratensis germination, demonstrating that for this species, transcription is not essential for radicle protrusion and that long-lived mRNA are used for initial protein synthesis. In contrast, incised white clover seeds showed delayed germination in presence of α-Am, suggesting that expression of some specific genes may help in the first germination steps. Osmopriming (PEG 8,000 60%) improved germination of seeds exposed to 100 μM Cd but the positive effect of this pretreatment was suppressed ( T. repens) or drastically mitigated ( P. pratensis) when Act-D or Cx were added to the priming medium. Cadmium reduced α- and β-amylase activities in germinating seeds but osmoprimed seeds exhibited higher activities than unprimed seeds. The presence of inhibitors in the priming medium reduced α- and β-amylase activities. These results suggest that the two studied species differed significantly in the mechanisms occurring during early seed germination and that the beneficial effect of priming requires gene expression and protein synthesis. [ABSTRACT FROM AUTHOR]

Reduced-growth, glyphosate-resistant Kentucky bluegrass (Poa pratensis L.) has recently been developed. There has been no comparative analysis of the newly developed transgenic Kentucky bluegrass lines to conventional cultivars or tissue culture-derived lines to determine vegetative and flower characteristic differences and similarities. This study measured the vegetative and reproductive characteristics of the transgenic lines, tissue culture-derived control lines, and reference cultivars during 2004 and 2005, in Ames, IA. The study was conducted in a noncompetitive, nonmown, spaced plant setting. Data collection of vegetative characteristics included rhizome spread and total plant area. Data collection for flower characteristics included flower phenology and morphological characteristic measurements, including panicle length, number of spikelets per panicle, and flag leaf characteristics. Transgenic lines as a group exhibited 29 and 32% less rhizome spread than the reference cultivars and tissue culturederived control lines, respectively, in 2004 and 37 and 40% less rhizome spread than reference cultivars and tissue culture-derived control lines, respectively, in 2005. Flower emergence times for all transgenic lines were comparable to their respective tissue culture-derived control lines and reference cultivars. [ABSTRACT FROM AUTHOR]

Heat-tolerant bluegrass varieties were developed to resist dormancy and retain pigmentation during heat stress events. The objective of this study was to investigate the influence of grass species, nitrogen (N) fertilization, and seasonality on the accumulation patterns of lutein, β-carotene, and chlorophyll a and b in the leaf tissues of turfgrass. The heat-tolerant bluegrass cultivars Dura Blue and Thermal Blue (Poa pratensis L. x Poa arachnifera Torr.), Apollo kentucky bluegrass (Poa pratensis L.), and Kentucky 31 tall fescue (Festuca arundinacea Schreb.) were compared for the accumulation of plant pigments. Evaluations were conducted over 2 consecutive years (Years 4 and 5 after establishment) during two different seasons (spring and summer) and under varying N fertilization. Fertilizer applications of 5, 14, and 27 g N/m²/year resulted in a significant positive correlation for the accumulation of leaf blade lutein and chlorophyll a and b, but not for β-carotene. The accumulation of the four measured plant pigments among the grasses was significantly different with 'Apollo' having the largest concentration of pigments followed by 'Dura Blue', 'Thermal Blue', and finally 'Kentucky 31'. Specifically, when comparing the cultivars Apollo and Kentucky 31, the pigment levels decreased 27%, 26%, 26%, and 23% for lutein, β-carotene, and chlorophyll a and b, respectively. The interesting observation of the analysis of the grass pigment concentrations was that the least reported heat-tolerant cultivar in our study ('Apollo') had the largest measured pigment concentrations. [ABSTRACT FROM AUTHOR]

Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect C input and storage in these systems. Research was conducted to determine the rate of soil organic C (SOC) changes, soil C sequestration, and SOC decomposition of fine fescue (Festuca spp.) (rainfed and irrigated), Kentucky bluegrass (Poa pratensis L.) (irrigated), and creeping bentgrass (Agrostis palustris Huds.) (irrigated) using C isotope techniques. We found that 4 yr after establishment, about 17 to 24% of SOC at 0 to 10 cm and 1 to 13% from 10 to 20 cm was derived from turfgrass. Irrigated fine fescue added the most SOC (3.35 Mg C ha-1yr-1) to the 0- to 20-cm soil profile but also had the highest rate of SOC decomposition (2.61 Mg C ha-1 yr-1). The corresponding additions and decomposition rates for unirrigated fine rescue, Kentucky bluegrass, and creeping bentgrass in the top 20-cm soil profile were 1.39 and 0.87, 2.05 and 1.73, and 2.28 and 1.50 Mg C ha-1 yr-1, respectively. Irrigation increased both SOC input and decomposition. We found that all turfgrasses exhibited significant C sequestration (0.32-0.78 Mg ha-1 yr-1) during the first 4 yr after turf establishment. The net C sequestration rate was higher, however, for irrigated fine fescue and creeping bentgrass than for Kentucky bluegrass. To evaluate total C balance, additional work is needed to evaluate the total C budget and fluxes of the other greenhouse gases in turfgrass systems. [ABSTRACT FROM AUTHOR]

We tested the efficacy of matrix-based fertilizers (MBFs) to improve Kentucky bluegrass ( Poa pratensis L.) growth while reducing NH, NO3, dissolved reactive phosphorus (DRP), and total phosphorus (TP) compared to commercial slow-release fertilizer (SRF) Polyon®, ESN®, and Avail® in greenhouse column studies. The MBFs covered a range of inorganic N and P in compounds that are relatively loosely bound (MBF6) and more tightly bound compounds (MBF7) with Al(SO4)318H2O and/or Fe2(SO4)33H2O and with high ionic exchange compounds starch, cellulose, and lignin. The total amount of NO3 and NH4 leached was greater from columns receiving Polyon® and ESN® fertilizers than all other treatments. The MBF6+Avail® or MBF7+Avail® fertilizers leached 64–68% less NO3 than Polyon® (43-0-0) and ESN® (46-0-0), and 73–76% less TDP and TP than Avail® (10-34-0). A greater amount of NO3 was leached from the MBF6+Avail® and the MBF7+Avail® treatments than the other MBF fertilizer treatments. Shoot and root biomass were greater when plants received the Avail ®, MBF6+Avail®, and MBF7+Avail® fertilizer treatments than the other fertilizer treatments. When combined with small quantities of commercial SRFs, these new MBFs were able to maintain plant growth while reducing N and P leaching. These new MBF formulations do not depend on organic or inorganic coatings to reduce N and P leaching and with further testing and development could be effective commercial fertilizers. [ABSTRACT FROM AUTHOR]

1. The ability to suppress neighbour growth and the ability to withstand growth suppression are widely viewed as two forms of competition, competitive effect and competitive response. 2. We conducted a greenhouse experiment to determine whether these two forms of competition were functionally linked, and to determine which plant traits are associated with effect and response competitive abilities among seedlings of 22 perennial North American prairie species. We further explored the trait-function relationship by growing plants under different soil fertilities and with different neighbour species. 3. To determine competitive abilities, we used a phytometer approach with two phytometer species: Poa pratensis and Achillea millefolium grown in competition with each of the 22 focal species under low and high fertility. Root and shoot morphological traits were measured and principal component analyses were used to reduce the dimensionality of the data. Three axes were extracted, which roughly corresponded to size, root and shoot architecture. 4. The hierarchy of competitive effect ability of the target species did not vary with either soil fertility or neighbour identity, while the hierarchies of competitive response abilities were highly variable among the treatments. Competitive effect ability was closely associated with size-related traits under high nutrient conditions, and with root-related traits under low nutrient conditions. In contrast, few plant traits axes were related to competitive response. 5. These findings indicate significant differences between competitive effect and response ability. We suggest competitive effect ability is a consistent trait of a species, linked to specific plant traits. In contrast, we found little evidence to support the idea that competitive response ability is itself a species trait, and instead it appears this may be simply a collection of different ways of avoiding or tolerating competition and/or low nutrient conditions. Supporting this argument was a lack of any consistency in which traits were associated with competitive response ability. 6. We recognize the limitations of a single study of seedlings under greenhouse conditions. However, we suggest these findings indicate a need to critically examine current assumptions about plant competition, how it is defined, and the traits which control a species’ competitive ability. [ABSTRACT FROM AUTHOR]

Urea replaced ammonium nitrate (AN) as a nitrogen (N) source for dryland Kentucky bluegrass seed production in the inland Pacific Northwest in the United States. This study assessed ammonia (NH3) volatilization, N recovery, and seed yield from urea as compared to AN. Laboratory incubations indicate NH3 volatilization is greater from soil covered by fresh residue than soil alone or covered by burned residue. Although pH of the fresh and burned residues exceeded 8.0, urease activity in burned residue was <15% of that in unburned residue or soil. Ammonia volatilization from dry urea and fluid urea AN was greater than AN at burned and unburned sites after a 5 October application. Ammonia volatilization was higher and N recovery and seed yield were lower for urea after a 15 November application at an unburned site. To reduce NH3 volatilization, apply urea to fields with low urease activity or moisture content and/or immediately before a significant rain event. [ABSTRACT FROM AUTHOR]

Genetic diversity within species is a potentially important, but poorly studied, determinant of plant community dynamics. Here we report experiments testing the influence of genotype identity and genotypic diversity both on the invasibility of a foundation, matrix-forming species (Kentucky bluegrass, Poa pratensis), and on the invasiveness of a colonizing species (dandelion, Taraxacum officinale). Genotypes of Kentucky bluegrass in monoculture showed significant variation in productivity and resistance to dandelion invasion, but the productivity and invasion resistance of genotypic mixtures were not significantly different from those of genotypic monocultures. Indirect evidence suggested temporal shifts in the genotypic composition of mixtures. Dandelion genotypes in monoculture showed striking and significant variation in productivity and seed production, but there was no significant tendency for these variables in mixtures to deviate from null expectations based on monocultures. However, productivity and seed production of dandelion mixtures were consistently greater than those of the two least productive genotypes, and statistically indistinguishable from those of the three most productive genotypes, suggesting the possibility of greater invasiveness of genotypically diverse populations in the long run due to dominance by highly productive genotypes. In both experiments, the identity of genotypes was far more important than genetic diversity per se. [ABSTRACT FROM AUTHOR]

Post-harvest residue removal is critical for high seed production of Kentucky bluegrass (Poa pratensis L.). Previous work showed some accessions have little yield reduction with mechanical removal of post-harvest residue compared with the controversial practice of open-field burning. Using 10 of these accessions, our objectives were (i) to relate seed yield and yield components in spaced plants to yield in row-seeded plots, (ii) to link yield to growth and development factors, and (iii) to determine variation for seed production factors among accessions. Seed yield, seeds per panicle, panide number, weight per seed, heading, anthesis, and harvest dates showed strong accession differences on spaced plants in 2002 and 2003. Yields in row-seeded plots from 1998 and 1999 data were consistently correlated with yield per plant per area in spaced plants in 2002 (r = 0.75, P < 0.05) and 2003 (r = 0.90, P < 0.01). Turf quality was negatively correlated with yield per plant per area in 2002 and 2003 but was not consistently correlated with yield components. Days from heading to anthesis consistently correlated with yield per plant per area in 2002 (r = 0.81, P < 0.01) and 2003 (r = 0.85, P < 0.01). Variation for seed yield and yield components was observed within accessions both years and differed among accessions. The results show that seed yield per plant per area in spaced plants may be a useful predictor of yield in field stands and that a long heading to anthesis period promotes seeds per panicle and seed yield. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare differential nutrient responses heat stress in relation to heat tolerance for warm-season (C4) common bermudagrass [Cynodon dactylon (L.) Pers.] and cool-season (C3) kentucky bluegrass (Poa pratensis L.). Both species were exposed to two temperature regimes in growth chambers: optimal day/night temperature conditions (24/20 °C for kentucky bluegrass and 34/30 °C for bermudagrass) or heat stress (10 °C above the respective optimal temperature for each species). Heat injury in leaves was evaluated and the concentrations of several major macronutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)[ in both grass species were measured at 0, 7, 14, 21, and 28 days of treatment. Heat stress reduced leaf photochemical efficiency and cellular membrane stability in both species, but bermudagrass leaves exhibited less damage in these parameters than kentucky bluegrass. Heat stress caused a significant decline in N, P, and K concentration, beginning at 7 days in kentucky bluegrass, but had no significant effects on N, P, and K concentration in bermudagrass during the 28-day treatment period. The concentration of Ca and Mg increased under heat stress in both kentucky bluegrass and bermudagrass, but there were no significant differences between the species under optimal or high-temperature conditions, suggesting they were not involved in heat responses in either species. The differential responses of N, P, and K to heat stress could at least partially account for the differences in heat tolerance between the two species and demonstrate the importance of sufficient N, P, and K in turfgrass adaptation to heat stress. [ABSTRACT FROM AUTHOR]

Many field studies have examined how site fertility, soil differences and site history influence the diversity of a plant community. However, only a few studies have examined how the identity of the dominant species influences the diversity in grasslands. Plant species differ widely in phenology, growth form and resource uses; thus, communities dominated by different species are also likely to strongly differ in the environment that they create and in which the subdominant species exist. We examined the correlation between the four most dominant species and community diversity in 2100 plots, located in 21 abandoned agricultural fields in central Minnesota over a 23-year period. The four most common species were two non-native C3 cool season species, Poa pratensis and Agropyron repens, and two native C4 warm season species, Schizachyrium scoparium and Andropogon gerardii. We found that the differences in the dominants explained up to 27% of the community diversity. Thus, the identity of the dominant species can have a strong influence on community diversity and studies examining factors that influence plant community diversity need to incorporate the effect of the dominants. Secondly, we found that the non-native C3 grass dominated communities had lower overall and lower native species richness relative to the native C4 grass dominated communities. Therefore, a shift in dominants from C4 to C3 may lead to a large community diversity decline. We found that Poa pratensis, the most abundant non-native C3 grass increased in abundance over the 23 years; thus, the negative influence of non-natives on the community diversity is not decreasing over time and active management is required to restore native grassland plant communities. [ABSTRACT FROM AUTHOR]

Transgenic herbicide-resistant cultivars of creeping bentgrass (Agrostis stolonifera L.) have been developed and are being considered for commercial release. Concerns regarding transgenic species include potential for outcrossing of the crop, which may produce novel genotypes with increased weediness. Persistence and multiyear growth of interspecific hybrids between creeping bentgrass and velvet bentgrass (A. canina L.), colonial bentgrass (A. capillaris L.), dryland bentgrass (A. castellana Boiss. and Reut.), and redtop bentgrass (A. gigantea Roth) and the backcross progeny of the hybrids were compared with the parental species in field experiments. The plants were evaluated over 2 yr in residential Kentucky bluegrass (Poa pratensis L.) and a low maintenance roadside turf of mixed species. With the exception of redtop bentgrass by creeping bentgrass interspecific hybrids, all interspecific hybrids between creeping bentgrass and colonial, dryland, and velvet bentgrasses were equally or less competitive relative to their parental species. Backcross progeny of interspecific hybrids, including those of redtop bentgrass by creeping bentgrass hybrids, were equally or less competitive than parental species. Bentgrasses that were highly competitive in residential turf were also competitive under roadside maintenance, suggesting bentgrasses have weediness potential regardless of management intensity. [ABSTRACT FROM AUTHOR]

Some perennial grasses secrete phytosiderophores from the roots in response to Fe-deficiency. Here, we characterized the pattern of phytosiderophore secretion by Lolium perenne (cv. ‘Tove’) and Poa pratensis (cv. ‘Baron’), which are used to correct iron-deficiency induced chlorosis in fruit trees grown on calcareous soils. Both species showed a distinct diurnal rhythm in phytosiderophore secretion, but the secretion time differed between species; the secretion peak time was about 2 h earlier in L. perenne than in P. pratensis under the same growth conditions. The secretion time was shifted by changing temperature during the collection of phytosiderophores in both L. perenne and P. pratensis. Increasing root-zone temperature resulted in earlier secretion, while lowering the temperature resulted in delayed secretion. Furthermore, this shift of secretion time was achieved by changing the temperature around the root-zone. Shading treatment during the secretion period did not affect the secretion time in either species. These results indicate that the secretion of phytosiderophore is triggered by the temperature around the roots, but not light, in these two perennial grasses. [ABSTRACT FROM AUTHOR]

As competition for water resources in areas of western North America intensify as a result of increasing human populations, the sustainability of turfgrass irrigation with limited water resources is questionable. A potential part of the solution is the use of recycled wastewater for landscape irrigation. However, as a result of high levels of salt, successful irrigation with recycled wastewater will likely need to be coupled with selection for increased salinity tolerance in turfgrass species. Additionally, salinity tolerant turfgrass will allow production on soils with inherently high salt levels. The study described here characterized the relative salinity tolerance of 93 accessions of Poa germplasm from the USDA National Plant Germplasm System (NPGS). Control cultivars of tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire], perennial ryegrass (Lolium perenne L.), and kentucky bluegrass (Poa pratensis L.) were also evaluated for comparison. Kentucky bluegrass accessions exhibited a wide range of LD50 (salinity dosage necessary to kill 50% of plants) values from 811 ECdays (PI 369296 from Russia) to 1922 ECdays (PI 371768 from the United States). Five kentucky bluegrass accessions exhibited salinity tolerance equal to or better than that of the tall fescue (LD50 = 1815 ECdays) and perennial ryegrass (LD50 = 1754 ECdays) checks. Thus, there is sufficient variation within this species to develop bluegrass with substantially higher salinity tolerance. [ABSTRACT FROM AUTHOR]

Persistency of grass associations is one of the way to counteract degradation of grasslands. The objective of the investigations carried out in 9-11 years of pasture use was to evaluate Poa pratensis persistence in sward. In the years 2005-07 Poa pratensis made 22.3-47.6% in the first regrowth of grass-clover sward and 39.3-52.1% of grass sward. The last two years were marked by a clear decrease of the studied species amount in the pasture association, irrespective of sward type and N fertilization dose. However, it was noted that the further increase of Poa trivialis and Deschampsia caespitosa share in spring sward, while Trifolium repens and Dactylis glomerata in summer. The higher competitiveness of Dactylis glomerata under conditions less suitable for Kentucky bluegrass development induced pasture productivity stabilization. Yet a higher abundance of this species in summer, like the growing Poa trivialis contribution in spring sward regrowth, has not ensured stabilization of pasture association in a marshy habitat. [ABSTRACT FROM AUTHOR]

Abstract  An endophytic bacterium, wild poplar strain B (WPB), isolated from stems of wild cottonwood (Populus trichocarpa) was identified to Burkholderia vietnamiensis by analyzing the recA and rDNA genes. Phylogenetic analysis of the nifHDK cluster indicates that the WPB isolate shares high sequence similarity with known B. vietnamiensis strains. The nitrogenase activity of WPB was determined by a 15N2 incorporation assay and an acetylene reduction assay. WPB was also monitored for production of indole-3-acetic acid (IAA), a phytohormone which can promote plant growth, when incubated with l-tryptophan. In addition, its plant growth promotion capacity was assessed by inoculating the WPB strain onto Kentucky bluegrass in nitrogen-free medium. Compared to uninoculated control plants, the plants inoculated with WPB gained more dry weight (42%, p = 0.01) and more nitrogen content (37%, p = 0.04) in 50 days. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to investigate accumulation of reactive oxygen species, antioxidant enzyme activities, and gene expression patterns of antioxidant enzymes of Kentucky bluegrass (Poa pratensis L.) under drought stress and recovery. Grass (c.v. Midnight II) was subjected to soil drying for 5 d and then rewatered for 1 d in growth chambers. Drought stress increased superoxide (O2 −) production of leaves and hydrogen peroxide (H2O2) content of the leaves and roots. Recovery enhanced leaf O2 − production and root H2O2 content. Lipid peroxidation of the roots increased 4.5-fold and 2.4-fold under drought stress and recovery, respectively. Drought stress increased the leaf activities of ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and the root activities of catalase (CAT, EC 1.11.1.6), glutathione reductase (GR, EC 1.6.4.2) and MDHAR, while reducing the root activities of superoxide dismutase (SOD, EC 1.15.1.1) and DHAR, respectively. The increased leaf activities of APX, MDHAR, DHAR and the root activities of MDHAR and CAT were observed after rewatering, compared to the control. For the leaves, the expressions of iron SOD (FeSOD), cytosolic copper/zinc SOD (Cu/ZnSOD), chloroplastic Cu/ZnSOD, and DHAR were down-regulated by drought stress but recovered to control level after rewatering, while the expressions of GR and MDHAR were up-regulated and remained that levels after recovery. For the roots, the expressions of cytosolic Cu/ZnSOD, manganese SOD (MnSOD), cytosolic APX, GR, and DHAR were down-regulated under drought stress but recovered except for GR and DHAR, while MDHAR expression was up-regulated. No differences in CAT transcript abundance were noted among the treatments. Antioxidant enzymes and their gene expressions may be differentially or cooperatively involved in the defense mechanisms in the leaves and roots of Kentucky bluegrass exposed to drought stress and recovery. [Copyright &y& Elsevier]

The apomictic breeding behavior of Kentucky bluegrass (Poa pratensis L.) results in many unique cultivars. A classification system was previously developed to characterize the large number of Kentucky bluegrass cultivars into different types. However, many new cultivars have been released since the last refinement of the classification system. The objectives of this study were to determine differences in morphological and agronomic characteristics among select Kentucky bluegrass cultivars representing the major classification types and to determine broad-sense heritability estimates for important morphological (plant height, panicle length, flag leaf height, and flag leaf length and width) and agronomic (rhizome spread) traits in Kentucky bluegrass. A spaced-plant nursery trial was established in the spring of 2003 at Adelphia, NJ. One hundred seventy-three cultivars and selections were planted in a randomized complete block design with three replications. The morphological and agronomic traits listed were measured on spaced plants. High Density type cultivars (formerly the Aggressive type cultivars) had the most prostrate growth habit with plant heights of 33 and 43 cm in 2004 and 2005, respectively. Mid-Atlantic and Texas x Kentucky bluegrass hybrids had the widest rhizome spread (Mid-Atlantic = 73 and 121 cm; Texas x Kentucky bluegrass hybrids = 72 and 122 cm) in 2004 and 2005, respectively. Broad-sense heritability estimates were high for plant height (H = 0.84), panicle length (H = 0.88), flag leaf height (H = 0.85), and rhizome spread (H = 0.85); moderate for flag leaf length (H = 0.71); and low for flag leaf width (H = 0.11). This study characterizes new cultivars into respective groups and identifies the genetic inheritance of important morphological and agronomic traits in Kentucky bluegrass. [ABSTRACT FROM AUTHOR]

Waterlogging often occurs simultaneously with high temperatures during summer. The objective of this study was to characterize anaerobic metabolism and transcript abundance of fermentative enzymes in roots of Kentucky bluegrass ( Poa pratensis L.) in response to short-term waterlogging and high temperature stresses. Grasses were subjected to four treatments: (1) well-drained under normal temperature (20/15°C, day/night; control); (2) waterlogging under normal temperature (WL); (3) well-drained under high temperature (35/30°C, day/night; HT); and (4) waterlogging under high temperature (WL + HT). Greater reductions in leaf elongation rate and shoot dry mass were observed under WL + HT than either stress alone. Root water-soluble carbohydrate concentration decreased 45% and 46% at 3 and 5 days of WL + HT, respectively, compared to the control. At 5 days, activities of root alcohol dehydrogenase increased 93% and 90% and lactate dehydrogenase increased 95% and 98% under WL and WL + HT, respectively, compared to the control. Transcript abundance of ADH and PDC genes in the roots were not or only slightly shown under the control or HT conditions but were induced by WL or WL + HT, particularly under WL. The results indicated that short-term WL + HT induced root anaerobic metabolism in a similar way to WL alone but had more severe effects on leaf growth and root WSC than did WL in Kentucky bluegrass. [ABSTRACT FROM AUTHOR]

Annual bluegrass (Poa annua L.) is a problematic weed in Kentucky bluegrass (Poa pratensis L.). Bispyribac-sodium herbicide can effectively control established annual bluegrass in other cool-season turfgrasses, but unacceptable injury to Kentucky bluegrass has been reported. However, only a few Kentucky bluegrass cultivars have been evaluated. The objective of this study was to determine the extent of intraspecific variability among Kentucky bluegrass cultivars and selections to sequential applications of bispyribac-sodium herbicide. Field experiments were conducted in 2004 and 2005 in New Jersey to determine the response of 55 Kentucky bluegrass cultivars and selections to bispyribac-sodium. The herbicide was applied at 188 g·ha-1 followed 3 weeks later by a second application of 281 g·ha-1. Kentucky bluegrass injury ranged from 8% to 93% 8 weeks after initial treatment (WAIT). 'Blackstone', 'Serene', and A98-962 were the most tolerant to bispyribac-sodium, exhibiting less than 20% injury 8 WAIT. Conversely, 'Washington', 95AN-10, and 'Avalanche' were the most susceptible with up to 93% injury 8 WAIT. The range in tolerance to bispyribac-sodium within Kentucky bluegrass indicates the potential for the identification and development of cultivars with improved tolerance to bispyribac-sodium herbicide. [ABSTRACT FROM AUTHOR]

New turfgrass varieties and management practices have introduced new options for transition zone athletic field managers. Our objectives were to determine the wear tolerance of four turfgrasses in the transition zone with and without crumb rubber under simulated athletic field conditions, and to determine if improved cool and warm-season turfgrass species can be used for transition zone athletic fields. Field trials evaluated the use of four turfgrass species with and without crumb rubber topdressing in Knoxville, TN, and Fayetteville, AR. Experimental design was a randomized complete block with a split-strip plot treatment arrangement. Plots containing 'Thermal Blue' hybrid Kentucky bluegrass (Poa pratensis L. × P. arachnifera Torr.) or 'Riviera' [Cynodon dactylon (L.) Pers.], 'Quickstand' (C. dactylon), or 'Tifway' (C. dactylon × C. transvaalensis Burtt-Davy) bermuda-grass were evaluated. Crumb rubber treatments were topdressed to achieve a 2-cm depth. Traffic was applied to each plot using a Cady Traffic Simulator to simulate athletic field wear. Traffic applications coincided with actual fall athletic seasons ranging from October to December 2005. Hybrid Kentucky bluegrass proved to be acceptable for use in transition zone athletic fields, Riviera and Tifway showed comparable wear tolerance, and Quickstand showed the lowest wear tolerance of the varieties tested. Crumb rubber topdressing resulted in a significant increase in turfgrass wear tolerance, and a decrease in surface hardness, soil bulk density, and shear resistance. [ABSTRACT FROM AUTHOR]

Abstract: We examined how elevated atmospheric [CO2] and higher rate of nitrogen (N) input may influence grasshopper growth by changing food plant quality and how such effects may be modified by species diversity of the plant community. We reared grasshopper nymphs (Melanoplus femurrubrum) on Poa pratensis from field-grown monocultures or polycultures (16 species) that were subjected to either ambient or elevated levels of CO2 and N. Grasshopper growth rate was higher on P. pratensis leaves grown in monocultures than in polycultures, higher on P. pratensis grown under elevated than under ambient [CO2], and higher on P. pratensis grown under elevated than under ambient [N]. The higher growth rate observed on P. pratensis exposed to elevated [CO2] was, however, less pronounced for polyculture- than monoculture-grown P. pratensis. Growth rate of the grasshoppers was positively correlated with leaf [N], [C], and concentration of soluble carbohydrates+lipids. Concentration of non-structural carbohydrates+lipids was higher in leaves grown under elevated than under ambient [CO2], and the difference between P. pratensis grown under ambient and elevated [CO2] was greater for monoculture- than polyculture-grown P. pratensis. In addition, leaf N concentration was higher in P. pratensis grown in monocultures than in polycultures, suggesting that plant species richness, indirectly, may influence insect performance by changed nutritional value of the plants. Because we found interactive effects between all factors included ([CO2], [N], and plant species diversity), our results suggest that these parameters may influence plant–insect interactions in a complex way that is not predictable from the sum of single factor manipulations. [Copyright &y& Elsevier]

A field experiment was conducted to determine the optimal method for turfgrass revegetation at the new Incheon International Airport, Republic of Korea. The existing soil base was reclaimed sea sand dredged from the Yellow Sea. Ten different soil media main plots were created by treating the sand with combinations of mountain soil, chemical fertilizer [15-11-14 nitrogen-phosphorus-potassium (N-P-K)], peat moss, a wetting agent, pig manure, and composted pine bark. Subplots were established with five turfgrass treatments that included Zoysia japonica (ZJ), Z. sinica (ZS), Z. koreanna (ZK), cool-season grass combination I (CSG I: Festuca arundinacea 30%, Poa pratensis 40%, and Lolium perenne 30%), and cool-season grass combination II (CSG II: Festuca arundinacea 40%, L. perenne 20%, F. rubra 20%, and Puccinellia distans 20%). The highest percentage cover rate for all grass treatments occurred in sea sand treated with 5 cm of mountain soil plus 114 g m-2 of chemical fertilizer. Zoysia japonica had the highest percentage cover rates throughout the study. On 4 July 1998, the turfgrass cover ranking was ZJ (99.5% cover)>ZK (86.7%)>ZS (39.6%)>CSG II (33.3%), CSG I (33.1%). Zoysia japonica also showed the highest drought tolerance among turfgrass species on all soil bases. The treatment that included mountain soil plus chemical fertilizer reduced the pH, EC, alkalinity, and soluble sodium (Na+) by the exchange of calcium (Ca2+) for Na+. The amendment of sea sand with mountain soil and chemical fertilizer, followed by establishment to ZJ, was determined to be the best method of reclamation for the new airport. [ABSTRACT FROM AUTHOR]

Creeping bentgrass (Agrostis stolonifera L.; CBG) is a common weed in home lawns and golf course roughs in many regions of the United States. Currently, no herbicides are registered for selective control of CBG in cool-season grasses. The objective of this field study was to evaluate the ability of mesotrione and triclopyr ester to selectively remove CBG from Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.). Mesotrione (0.14 and 0.21 kg⋅ha-1 a.i.) and triclopyr ester (0.56 and 1.12 kg⋅ha-1 a.i.) were applied on a 2-week interval two, three, or four times in Connecticut and Maryland in 2005, and three or four times in Maryland in 2006. Two applications of mesotrione at 0.21 kg⋅ha-1 a.i. provided marginally acceptable CBG control, but three or four applications at 0.14 or 0.21 kg⋅ha-1 a.i. provided excellent CBG control. Mesotrione elicited little or no injury to Kentucky bluegrass, but generally caused objectionable injury in tall fescue for about 7 to 14 d after each application. Triclopyr applied at 0.56 kg⋅ha-1 a.i. reduced CBG cover, but the level of control generally was unacceptable, regardless of application frequency. Three or four applications of triclopyr (1.12 kg⋅ha-1 a.i.) effectively controlled CBG in Connecticut in 2005 and Maryland in 2006. Triclopyr caused no visual injury to tall fescue, regardless of rate or application frequency. Four triclopyr applications to Kentucky bluegrass, however, were phytotoxic and reduced stand density, especially at the high rate (1.12 kg⋅ha-1 a.i.). Three summer applications of mesotrione (0.14 kg⋅ha-1 a.i.) or triclopyr (1.12 kg⋅ha-1 a.i.) provided the best combination of turfgrass safety and CBG control. Chemical names used: [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr ester); 2-[4-(methylsulfonyl)-2-nitrobenzoyl]-l,3-cycilohexanedione (mesotrione) [ABSTRACT FROM AUTHOR]