Poa Arachnifera Research Articles

Two-Sex Demography, Sexual Niche Differentiation, and the Geographic Range Limits of Texas Bluegrass (Poa arachnifera).

AbstractUnderstanding the mechanisms that generate biogeographic range limits is a long-standing goal of ecology. It is widely hypothesized that distributional limits reflect the environmental niche, but this hypothesis is complicated by the potential for intraspecific niche heterogeneity. In dioecious species, sexual niche differentiation may cause divergence between the sexes in their limits of environmental suitability. We studied range boundary formation in Texas bluegrass (Poa arachnifera), a perennial dioecious plant, testing the alternative hypotheses that range limits reflect the niche limits of females only versus the combined contributions of females and males, including their interdependence via mating. Common garden experiments across a longitudinal aridity gradient revealed female-biased flowering approaching eastern range limits, suggesting that mate limitation may constrain the species' distribution. However, a demographic model showed that declines in λ approaching range limits were driven almost entirely by female vital rates. The dominant role of females was attributable to seed viability being robust to sex ratio variation and to low sensitivity of λ to reproductive transitions. We suggest that female-dominant range limits may be common to long-lived species with polygamous mating systems and that female responses to environmental drivers may often be sufficient for predicting range shifts in response to environmental change.

Development of ent-kaurene Oxidase-Based Conserved Intron Spanning Primers for Species Identification in the Genus Poa (Poaceae; Bluegrass)

Interspecific hybridization has been attempted to combine the heat and drought of Poa arachnifera Torr. with the turf quality characteristics of several Poa species. Confirmation of an F1 hybrid through morphological analysis of vegetative and flowering characteristics is often time consuming and ambiguous. Ent-kaurene oxidase (KO) has been sequenced in rice, barley, and wheat. In rice, each of the five copies of KO gene has unique lengths for the first intron. Conserved intron spanning primers (CISP) can be used as a DNA marker to exploit variations of intron lengths that flank conserved gene sequences. In the present study, we developed CISP to sequence partial genomic fragments of the KO gene from seven Poa species. Through sequence analysis, species-specific primers were also developed to produce co-dominant markers that can be used to identify interspecific hybrids between Texas bluegrass and six other Poa species used in the present study.

Can't live with them, can't live without them? Balancing mating and competition in two-sex populations.

Two-sex populations are usually studied through frequency-dependent models that describe how sex ratio affects mating, recruitment and population growth. However, in two-sex populations, mating and recruitment should also be affected by density and by its interactions with the sex ratio. Density may have positive effects on mating (Allee effects) but negative effects on other demographic processes. In this study, we quantified how positive and negative inter-sexual interactions balance in two-sex populations. Using a dioecious grass (Poa arachnifera), we established experimental field populations that varied in density and sex ratio. We then quantified mating success (seed fertilization) and non-mating demographic performance, and integrated these responses to project population-level recruitment. Female mating success was positively density-dependent, especially at female-biased sex ratios. Other demographic processes were negatively density-dependent and, in some cases, frequency-dependent. Integrating our experimental results showed that mate-finding Allee effects dominated other types of density-dependence, giving rise to recruitment that increased with increasing density and peaked at intermediate sex ratios, reflecting tension between seed initiation (greater with more females) and seed viability (greater with more males). Our results reveal, for the first time, the balance of positive and negative inter-sexual interactions in sex-structured populations. Models that account for both density- and sex ratio dependence, particularly in mating, may be necessary for understanding and predicting two-sex population dynamics.

Annual Bluegrass Control during Hybrid Bluegrass Establishment from Sprigs

Hybrid bluegrass (Poa arachnifera Torr. × P. pratensis L.) establishment may be compromised by the emergence of annual bluegrass (P. annua L.) in the fall. The objective of this research was to evaluate the efficacy of herbicides for annual bluegrass control during the establishment of ‘DALBG 1201’ hybrid bluegrass from sprigs. Herbicides were applied at two timings: 5 d after planting (DAP) or 3 wk after planting (WAP). Hybrid bluegrass cover was rated four times between 9 and 35 WAP. The first and second visual ratings of annual bluegrass cover were made between 16 and 18 and at 30 WAP, respectively. At 26 WAP, hybrid bluegrass cover was approximately two‐fold in plots treated with mesotrione, oxadiazon, or topramezone compared with the nontreated. Primisulfuron applied singly or sequentially at 0.04 kg ha−1 controlled annual bluegrass ≥88% but reduced hybrid bluegrass cover >30% relative to the nontreated. Ethofumesate applied at 0.84 kg ha−1 at 3 WAP controlled annual bluegrass 74%. Oxadiazon at 1.12 or 2.24 kg ha−1 applied 5 DAP controlled annual bluegrass 67 to 75% at 30 WAP without reducing hybrid bluegrass cover. All other treatments provided poor (<70%) control of annual bluegrass. Overall, hybrid bluegrass was tolerant to ethofumesate, oxadiazon, mesotrione, and topramezone at rates evaluated during establishment from sprigs. Programs that included ethofumesate at 0.84 kg a.i. ha−1 or oxadiazon at 1.12 or 2.24 kg ha−1 provided best annual bluegrass control and improved hybrid bluegrass cover from the nontreated.

Seed Germination of Five <i>Poa</i> Species at Negative Water Potentials

Under field conditions water is often inadequate for satisfactory seed germination. An experiment was conducted to determine the effects of simulated dry conditions on germination and seedling growth of five bluegrass (Poa) species, including: Texas, P. arachnifera Torr.; annual, P. annua L.; mutton, P. fendleriana Vasey; Kentucky, P. pratensis L., and Sandberg, P. secunda J. Presl. bluegrasses. Fifty-seed samples of each species were germinated at water potentials of -1.6, -0.8, -0.4, -0.2, and 0 MPa for a 42-d period. Annual and Sandberg bluegrass tolerated moisture stress at germination better than the other species, requiring 14 d to reach 40% germination in water of -0.8 MPa potential. Kentucky bluegrass required 21 d to reach 40% germination under similar conditions. Mutton and Texas bluegrass were the least tolerant of low water potentials, requiring 42 d to reach 20% germination. Selection for increased seed germination at low water potentials should be possible in Poa species assuming the trait has moderate heritability.

The application of flow cytometry and a thioredoxin‐like nuclear gene for breeding Poa arachnifera x Poa pratensis hybrids

AbstractInterspecific hybridization between Poa arachnifera Torr. (Texas bluegrass) and Poa pratensis L. (Kentucky bluegrass) has shown to be a proven method for the development of turf‐type hybrid bluegrass cultivars for the southern United States. Unlike in P. pratensis, the use of DNA markers for molecular characterization and flow cytometry to determine nuclear DNA contents has not been extensively utilized in P. arachnifera. In this study, 2C nuclear DNA content of 19 different genotypes of P. arachnifera (both males and females) was determined to range from 8.02 to 13.24 pg/2C using flow cytometry. The DNA content of the hybrids between P. arachnifera and P. pratensis from two different pedigrees was found to be intermediate between their parents. Furthermore, the utility of the trx (thioredoxin‐like) nuclear gene in the identification of interspecific hybrids between P. arachnifera and P. pratensis was demonstrated using sequence and phylogenetic analyses. A newly discovered 851‐bp trx allele may serve as a useful marker to differentiate P. arachnifera from P. pratensis and provide insights into the evolutionary origin of P. arachnifera.

Growth Responses of Hybrid Bluegrass and Tall Fescue as Influenced by Light Intensity and Trinexapac-ethyl

Interspecific hybrids between texas bluegrass (Poa arachnifera Torr.) and kentucky bluegrass (Poa pratensis L.) are known to exhibit good heat tolerance, which has aided in their adaptation to the warmer climates of the southern United States, but their tolerance to shade has not been investigated. The objectives of this study were to 1) evaluate the growth responses of interspecific bluegrass hybrids (P. arachnifera × P. pratensis) in comparison with kentucky bluegrasses and a shade-tolerant cultivar of tall fescue (Festuca arundinacea Schreb.) under full sunlight and shaded environments, 2) identify optimum times to evaluate shade tolerance using the selected growth measurements, 3) calculate the minimum daily light requirements to retain acceptable turfgrass quality, and 4) determine if trinexapac-ethyl (TE) applications enhance hybrid bluegrass quality under shade. Two 10-week greenhouse experiments (late spring and early fall) were conducted in Dallas, TX. Within each of three light environments a randomized complete block design was used to accommodate three replications of eight genotypes treated with and without TE (0 or 0.228 kg·ha−1 a.i.). Turfgrass quality, leaf elongation rates, clipping dry weights, and percent green cover were measured. Meaningful comparisons were best during the late spring when daily light integrals (DLI) were optimum for healthy plant growth. Shade-tolerant hybrid bluegrasses (DALBG 1201 and TAES 5654) were identified using turfgrass quality and leaf elongation rates. These genotypes exhibited above-acceptable turfgrass quality in all environments, and a reduced leaf elongation rate similar to the tested dwarf-type tall fescue. DLI requirements of DALBG 1201 and TAES 5654 were ≤4 to achieve acceptable quality. TE applications generally did not improve turfgrass quality of genotypes, although leaf elongation rates were significantly reduced in all environments.

Frequency of androgenesis in Poa arachnifera × P. ligularis and P. poiformis hybridizations

AbstractThe rapid generation of haploids in most species remains a relatively infrequent event, but is considered an important tool for the development of homozygous lines and an approach for cytoplasmic transfer across related species. Poa arachnifera ‘Texas bluegrass’ is known to occasionally produce androgenic haploid recoveries following hybridization with Poa secunda. However, little information regarding the frequency of such behavior following hybridization with other Poa species is available. This study was undertaken to determine the frequency of androgenic haploids following interspecific hybridization of P. arachnifera × Poa ligularis and P. arachnifera × Poa poiformis. The P. arachnifera × P. ligularis hybridizations exhibited a frequency of androgenic dihaploids (ADH) at 1.00%; where the P. arachnifera × P. poiformis hybridizations indicated a frequency of 0.69%. Results from this study suggest ADH generation is an infrequent but consistent behavior likely found in sexual P. arachnifera.

DNA contents in Texas bluegrass (Poa arachnifera) selected in Texas and Oklahoma determined by flow cytometry

Texas bluegrass (Poa arachnifera Torr.) is a dioecious, perennial, cool-season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. Its major use has been for forage on rangelands in Texas and Oklahoma. More recently, interspecific hybrids between Texas bluegrass and Kentucky bluegrass (P. pratensis L.) have been developed and commercially released as heat tolerant turfgrass. Currently, the 2C nuclear DNA content of Texas bluegrass is unknown. Therefore, flow cytometry was performed on an assortment of male and female Texas bluegrass genotypes (n = 24) collected from fourteen locations in Texas and Oklahoma to estimate DNA content in picograms (pg). The DNA content of Texas bluegrass fell into two groups based on collection location. Plants collected from northwest Oklahoma and five other locations west of 33.75, −98.39 (latitude, longitude) ranged from 9.64 ± 0.04 to 10.07 ± 0.09 pg. Plants collected from four sites in Texas, east of 33.20, −98.16 contained a DNA content that ranged from 14.02 ± 0.04 to 14.75 ± 0.13 pg. Based on a root tip chromosome count, a male Texas bluegrass plant estimated to be 9.96 pg, appeared to contain 56 chromosomes, indicating the smaller DNA content plants may be octaploids (2n = 8x = 56). Significant differences were not detected between male and female plants based on DNA content. Knowledge of the DNA content in Texas bluegrass should be useful in a breeding program for characterizing germplasm and identifying desired DNA content levels among parental genotypes.

Registration of DALBG 1201 Hybrid Bluegrass

DALBG 1201 (Reg. No. CV-101, PI 671854) is a turf-type interspecific F1 hybrid derived from a cross between Texas bluegrass (Poa arachnifera Torr.) 20-11 (3-88) (PI 655088) as the female parent and a Kentucky bluegrass (P. pratensis L.) ecotype, CS#4, as the pollen parent. DALBG 1201 was evaluated under the designation 01-59-5 and TAES 5653. A total of 47 experimental hybrid bluegrass lines and three commercial checks, ‘Rebel Exeda’ tall fescue (Festuca arundinacea Schreb.) and ‘Reveille’ and ‘Thermal Blue Blaze’ hybrid bluegrass (P. arachnifera × P. pratensis) were evaluated at five locations (Auburn, AL, Starkville, MS, Raleigh, NC, Knoxville, TN, and Dallas, TX) from 2009 to 2012. DALBG 1201 was characterized by its superior turfgrass quality, darker green color, and higher shoot density than Reveille and Thermal Blue Blaze. Its leaf texture was finer than Rebel Exeda and similar to the hybrid bluegrass checks. Linear regression analysis for turfgrass quality indicated that DALBG 1201 was more stress tolerant compared with the three commercial checks and was highly stable across varying environmental conditions. Its superior performance over a wide range of southern test locations suggests that DALBG 1201 cool-season turf-type hybrid bluegrass is well-suited for use on lawns, landscapes, and other recreational sites across the southern United States.

Transfer of the perfect flower trait fromPoa secundatoPoa arachnifera

A Texas bluegrass (Poa arachnifera) population has been developed that successfully integrates the perfect flower trait from Poa secunda through interspecific hybridization. The resulting perfect flowered P. arachnifera population is perennial, rhizomatous and lacks the cobweb-like hairs that are a typical characteristic of the P. arachnifera parent. Inheritance of the perfect flowered trait suggests a relatively simple inheritance, perhaps allelic to the segregation of staminate and pistillate individuals in other dioecious systems. This material may have applications as a clean seeded, perfect flowered P. arachnifera cultivar; or as a germplasm resource in a P. arachnifera breeding program.

Cultivar Performance of Low-Input Turfgrass Species for the North Central United States

Turfgrass managers are in need of low-input turfgrass species options. We have previously identified a number of species that do well as low-input, sustainable turf in the north central United States. The objective of this study was to evaluate multiple cultivars of turfgrass species with known adaption to low-input environments in the North Central Region. Twenty-five turfgrass cultivars and selections, representing ten grass species, were evaluated at eight locations. Plots were established in late summer 2007, and after establishment were maintained at 7.6 cm without inputs of pesticides, fertilizer, or supplemental irrigation. Tall fescue, Chewings fescue, hard fescue, and colonial bentgrass performed well at most locations. Sheep fescue, tufted hairgrass, and prairie junegrass all performed adequately at some locations, and poorly at others. Texas bluegrass hybrids and the single Idaho bentgrass entry were not well adapted to most of the region.

Generation and release of molecular markers for Poa arachnifera Torr.

AbstractDNA‐based molecular markers can be used in a wide array of plant genetic studies, marker‐trait associations, seed purity evaluations and cultivar protection. However, for the genus Poa, the use of molecular markers is limited by the current lack of informative DNA based markers. This report represents the development and release of an additional 39 molecular markers, all derived from an unenriched Poa arachnifera Torr. genomic library. The newly released markers include genomic microsatellite markers, tandem repeats, palindromes and regions exhibiting low complexity generated from the P. arachnifera library. Many of the primer pairs used to amplify the markers were observed to exhibit polymorphisms when evaluated across five additional Poa species (P. pratensis L., P. secunda J. Presl, P. ligularis Nees ex Steud., P. poiformis [Labill.] Druce and P. labillardieri Steud.) The availability of these new and informative markers should provide Poa breeders and geneticists with additional tools for breeding and genetic research.

Impact of Hybrid Bluegrass and Tall Fescue Seeding Combinations on Brown Patch Severity and Weed Encroachment

Tall fescue (Festuca arundinacea) and hybrid bluegrass (Poa pratensis L. × Poa arachnifera) can both be successfully grown in the transition zone of the United States. However, each grass has limitations. Tall fescue is susceptible to the fungal pathogen Rhizoctonia solani, whereas slow establishment and susceptibility to weed infestations limit hybrid bluegrass. Previous studies have shown the benefits of combining kentucky bluegrass with tall fescue in seeding mixtures. Research was conducted to evaluate the impact of two seeding combinations of hybrid bluegrass and tall fescue (one combination seeded at a 1.9:1 seed count ratio favoring tall fescue, the other combination seeded at a 1:1.8 seed count ratio favoring hybrid bluegrass) as well as monocultures of the species on turfgrass cover, weed species infestation, brown patch disease severity caused by R. solani, sod strength and species ecology. The seeding combinations had lower weed density during establishment and greater turf cover than the monoculture of hybrid bluegrass. The monoculture of tall fescue was subjected to more brown patch disease than the seeding combinations during and after the first year of establishment. Brown patch infestations likely reduced tall fescue cover and led to a species shift favoring hybrid bluegrass in the seeding combinations based on tiller count and weight data. Seeding combinations of tall fescue and hybrid bluegrass are beneficial from an epidemiological perspective because they reduce disease and weed infestations compared with monocultures of either species. From an agronomic perspective, the seeding combination favoring tall fescue provided the densest turf, whereas the seeding combination favoring hybrid had the greatest sod strength. Chemical name used: clopyralid (3,6 dichloropyridine-2 carboxylic acid)

Genetic Relationships in Advanced Generation Hybrids Derived from Crosses between Texas (<i>Poa arachnifera</i>) and Kentucky (<i>Poa pratensis</i>) Bluegrass Using ISSR Markers

Fertile, advanced generation hybrids derived from crosses between Texas (Poa arachnifera Torr.) and Kentucky (Poa pratensis L.) bluegrass have been selected. The hybrids are currently being evaluated for low-input turf potential. Since they are derived from hand-harvested seed from first-generation hybrids located in field nurseries their exact genetic origin is unknown. This experiment was conducted to determine if there are still genetic relationships among the advanced generation hybrids and some of the Texas and Kentucky parents in their pedigrees. Four Inter Simple Sequence Repeat (ISSR) primer combinations resolved on 6% nondenaturing polyacrylamide gels resulted in 179 polymorphic bands that were scored to create a genetic similarity matrix and dendrogram based on Jaccard’s coefficient. The clustering of the advanced generation hybrids was generally in agreement with what would be expected based on their pedigrees and indicated it was more likely to select a fertile hybrid from an advanced generation, rather than the F1 generation.

Forage nutritive value of Texas bluegrass harvested in the morning and afternoon in northwest Oklahoma

Abstract Texas bluegrass ( Poa arachnifera Torr.) is a highly rhizomatous, dioecious, sexual, perennial, cool‐season grass native to southern Kansas, Oklahoma, western Arkansas and most of Texas. This native species is of particular interest for development into an improved cool‐season forage plant because of its heat tolerance and persistence under the extreme environmental conditions of the southern Great Plains. The objectives of this experiment were to determine water‐soluble, non‐structural carbohydrate and crude protein concentrations, forage dry matter yield, and in situ organic matter and crude protein disappearance from Texas bluegrass as affected by germplasm, maturity and time of harvest (morning and afternoon) at Woodward, Oklahoma. Crude protein concentrations ranged from 9 to 12% across seasons and did not differ between a morning and afternoon harvest. Dry matter yield ranged from 2130 to 5580 kg ha−1 over all harvest dates. Water‐soluble, non‐structural carbohydrate concentration was greater in the afternoon compared to morning harvests and ranged from 11 to 26%. Based on estimates from in situ digestion, the ratio of ruminally degradable crude protein to ruminally degraded organic matter in Texas bluegrass, it may compensate for the ruminally degraded nitrogen deficiency associated with dormant warm‐season grasses during the winter. The forage nutritive value parameters estimated in this study indicate that Texas bluegrass has potential as an improved cool‐season pasture grass.

No-Till Drill Planting of Texas bluegrass: On the Southern Plains

Combining the use of a flail-vac harvester, a hammer mill, and the Woodward WW2000 cleaner, Texas bluegrass ( Poa arachnifera Torr. [Poaceae]) seeds were successfully harvested, cleaned, and planted with a no-till drill at Woodward, Oklahoma. Texas bluegrass is one of only a few native, cool-season perennial grasses that withstand the region’s heat, droughts, and grazing. It produces nutritious and palatable forage during the late fall, winter, and early spring when most warm-season rangeland forages are low in nutrients and least preferred by livestock. The use of Texas bluegrass has been severely limited because the extremely cottony seed head makes it difficult to harvest and clean the seeds so they will flow through a drill. Seeds were no-till drilled into clear ground or into herbicide-killed wheat stubble and Texas bluegrass stands were established on 22 March 2007 and 15 September 2008 when soil moisture was available on the drilling date and for 6 to 8 wk after planting. The cleaning and planting method presented here could enable more widespread use of Texas bluegrass for pasture establishment, inclusion in native mixed seedlots for rangeland restoration, or inclusion in warm-season native pastures lacking a cool-season component.

Salinity Tolerance of Kentucky Bluegrass Cultivars and Selections Using an Overhead Irrigated Screening Technique

ABSTRACTAn 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.) × 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 m−1) 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, A03‐84, 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.

Isolation and characterization of microsatellite markers in the grass Poa arachnifera Torr

Microsatellite markers represent a proven class of genetic markers that have wide use in a variety of plant genetic studies and exhibit several advantages when compared to other DNA-based marker systems. Because of their successful use for genetic analysis in a number of plant species, their generation and availability in the genus Poa (Poaceae) would be advantageous for a multitude of Poa improvement, selection or marker-assisted breeding endeavors. However, due to the cost of their development, few microsatellite markers are available for Poa. In this study, we describe the isolation and characterization of 46 informative microsatellite primer pairs from an unenriched Poa arachnifera Torrey (Texas bluegrass) genomic library. Most of the microsatellite primer pairs amplify a single amplification product and were found to be useful across seven other Poa species. The availability of these informative microsatellite markers should serve a valuable role in the analysis and construction of genetic linkage maps and future marker assisted selection projects.

Relationships between Normalized Difference Vegetation Index and Visual Quality in Cool‐Season Turfgrass: II. Factors Affecting NDVI and its Component Reflectances

Normalized difference vegetation index (NDVI, computed as [near infrared (NIR) – Red)]/[NIR + Red]) may provide an objective means to evaluate visual quality of turfgrass. The NDVI is influenced by red (visible) and NIR reflectance (invisible), but each may respond differently to environmental factors; basic information is lacking about the two components in relation to turf quality. In this 3‐yr study near Manhattan, KS, we examined relationships of NDVI and its component reflectances along with visual quality ratings in Kentucky bluegrass (Poa pratensis L., ‘Apollo’), two Kentucky bluegrass × Texas bluegrass (Poa arachnifera Torr.) hybrids (‘Thermal Blue’ and ‘Reveille’), and tall fescue (Festuca arundinacea Schreb., ‘Dynasty’). Percentage green cover was measured with digital image analysis and shoot density was estimated visually to evaluate their impacts on turf quality and reflectance. Differences in NDVI and red and NIR reflectances were observed among turfgrasses at each level of quality. Across the range of turf quality, NDVI was influenced more strongly by red than NIR reflectance. Red reflectance was strongly affected by density (r = 0.85) and green cover (r = 0.86); NIR reflectance was affected by density (r = 0.63) but negligibly by green cover. Results suggest other fundamental factors that are poorly understood may be affecting NIR reflectance and, hence, NDVI in turf. These factors may confound relationships between NDVI and turf quality and require further study.