Growth, development, and germination among jointed goatgrass (Aegilops cylindrica Host. # AEGCY) accessions collected from nine western states were not consistently different in field plots near Pullman, WA, or in the greenhouse. Germination percentage and rate of spikelet germination of all accessions produced in the field and greenhouse were consistently high, averaging about 64% and 5.2 (on a unitless scale of 0 to 7), respectively. The Montana accession germinated consistently less than the others. In a separate greenhouse study comparing only the accessions from Colorado and Nebraska, the accession from Colorado averaged 18, 16, and 15% greater net photosynthesis rate (Pn), transpiration rate (E), and stomatal density, respectively, and 21% lower diffusive resistance (rl) than did the accession from Nebraska. However, growth parameters of the Nebraska accession averaged 7 to 35% greater than for the Colorado accession. Overall, the germination, growth, CO2 fixation, and water use among accessions appeared to be similar when jointed goatgrass was grown under Pacific Northwest conditions.

Greenhouse and field studies were conducted to compare root development of jointed goatgrass to winter wheat. Time of seminal root development in jointed goatgrass was similar to that of winter wheat and to root development predicted by a model. The only exception was the epiblast node roots (−1A and −1B), which developed approximately 1 phyllochron later in jointed goatgrass than in winter wheat. At crown nodes, A and B roots developed later in jointed goatgrass than in winter wheat, but development of X and Y roots at these nodes was similar for both species. First-order branching at a given root axis in jointed goatgrass roots began approximately 1 phyllochron after development of that axis, compared to 2.5 phyllochrons for winter wheat and the model. Second- and third-order branching of jointed goatgrass roots began 1 and 0.5 phyllochrons earlier than the respective branching of winter wheat roots. Leaf and tiller development followed the same pattern with time for both species. Maximum distance between crown roots was 1.5 to 3 times greater in winter wheat than in jointed goatgrass. Root length density at the 0- to 10-cm depth was less for jointed goatgrass than for winter wheat, but there were no differences at greater depths. The frequency of branching of first-order laterals was greater for jointed goatgrass than for winter wheat. In the field, the relationship of jointed goatgrass shoot development to accumulated growing degree-days was linear (R2 = 0.97), with a slope and y-intercept similar to winter wheat (R2 = 0.95). These data, showing slight differences in root growth and development between jointed goatgrass and winter wheat, may be used in predictive modeling to better understand the biology and ecology of each species, and may be used in conjunction with other models to establish weed threshold levels and improve selective placement of fertilizers and herbicides to benefit crop development.

Near isolines of ‘Nugaines’ winter Triticum aestivum that differed in height were planted with and without Aegilops cylindrica to determine the effect of plant height on competition against A. cylindrica. The isolines had either reduced height gene Rht 1, Rht 2, Rht 1 plus Rht 2, or neither Rht genes and averaged 79, 77, 51, and 101 cm tall, respectively, when grown with or without competition from A. cylindrica. Plants with fewer reduced height genes had the faster rates of height and weight gain, which are important traits for enhanced competitiveness. When growing in competition with A. cylindrica, the shortest isoline allowed the greatest amount of A. cylindrica seed production but did not have the lowest T. aestivum yield. However, when compared to the A. cylindrica-free control, the shortest isoline had the greatest percent yield loss. The tallest isoline reduced A. cylindrica seed production the most, and T. aestivum yield reduction due to A. cylindrica on a percent basis was the least when averaged over 2 yr. When competing against A. cylindrica, the tallest isoline did not always have the largest yield and yield parameters, and the shortest isoline did not always have the smallest yield and yield parameters. There is a cost to the T. aestivum plant to produce extra stem biomass that may reduce yield potential of taller plants and reduce the advantage gained by being taller than the surrounding weeds.

Winter wheat grain contaminated with jointed goatgrass joints is often discounted as much as 20% by grain buyers. A mail survey to Nebraska farmers in 1984 identified jointed goatgrass as one of the ten worst weed problems in winter wheat, but a field survey to the same area in 1986 found it in less than 1% of surveyed fields. The objective of this survey was to map the geographic distribution and severity of jointed goatgrass contaminating winter wheat grain in western Nebraska. Jointed goatgrass was found in 25, 29, and 20% of all wheat samples collected in 1990, 1991, and 1992, respectively. Nebraska counties bordering Colorado were found to have the highest percentage of wheat samples contaminated with jointed goatgrass joints, ranging from 23% in Cheyenne county in 1992 to 61% in Keith county in 1991.

In the greenhouse, glyphosate [N-(phosphonomethyl)glycine] at 0.6 kg ae/ha applied directly to seeds alone or seeds on the soil surface reduced germination and shoot dry weight of common rye (Secale cereale L. ♯3 SECCE). Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) applied similarly at 0.6 kg ai/ha reduced germination and shoot dry weight of downy brome (Bromus tectorum L. ♯ BROTE) and wheat (Triticum aestivum L. ‘Daws' ♯ TRZAX). Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)-one] at 0.6 kg ai/ha applied to seeds, soil, or seeds and soil had very little effect on germination, but significantly reduced shoot dry weight of common rye, downy brome, wheat, and jointed goatgrass (Aegilops cylindrica Host. ♯ AEGCY). Pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] at 0.6 kg ai/ha, and propham (isopropyl carbanilate) at 3.4 kg ai/ha plus extender (p-chlorophenyl-N-methylcarbamate) at 0.4 kg ai/ha substantially reduced shoot height and dry weight of all species, regardless of application method, with pronamide completely inhibiting shoot elongation and dry-weight production in three of the four species.

Seed survival of jointed goatgrass over 2 yr was related to cyclical seasonal changes in ability to germinate, field emergence, and seasonal precipitation and air temperature. The ability of seed to germinate was studied by incubating spikelets under constant, defined incubation conditions after retrieving samples from the field every 2 weeks over 2 yr. Less than 8% of jointed goatgrass seed that were initially set outdoors survived beyond 2 yr when left undisturbed on the soil surface or buried 5 cm deep. Periods of greatest seed loss coincided with periods of peak emergence in fall (late September and October). The ability of seed to germinate also peaked in fall and preceded the period of greatest field emergence and greatest decreases in seed survival.

Phytotoxic effects of metabolites from a naturally occurring rhizobacterial isolate, Pseudomonas syringae strain 3366, were determined on downy brome and ‘Hill 81’ winter wheat, along with 10 other weed and crop species. Centrifuged supernatant and concentrated ethyl acetate extracts from aerobic shake cultures of strain 3366 suppressed germination of seeds and reduced root and shoot growth in agar diffusion assays, soil assays, and under field conditions. Generally, root growth was inhibited more than shoot growth. Strain 3366 metabolites applied in soil inhibited all species tested. Crude ethyl acetate extracts in soil inhibited downy brome at concentrations that had little effect on winter wheat. Inhibitory activity was greater in Palouse silt loam (pH 5.8, 3.6% organic matter) than in Shano silt loam (pH 9.0, 0.8% organic matter). Activity of extracted metabolites decreased rapidly in wet soil but remained high in dry soil. Active metabolites were isolated and purified from the ethyl acetate extract using column chromatography, thin-layer chromatography, and crystallization. Chemical analysis revealed the presence of phenazine-1-carboxylic acid, 2-amino phenoxazone, and 2-amino phenol. Activity of these metabolites against downy brome was confirmed in agar assays. Phenazine-1-carboxylic acid, the major identifiable metabolite present in ethyl acetate extracts (20% by weight), inhibited downy brome root growth by 99% at concentrations of 5.7 mg L−1. Production of these metabolites in field soil by live bacteria of strain 3366 was confirmed with thin-layer chromatography.

Above-ground seedling development was characterized for five annual grass weeds: downy brome, bulbous bluegrass, jointed goatgrass, Italian ryegrass, wild oat; and three cereals: winter wheat, winter barley, and winter triticale in field experiments over two years. The rate of leaf production on the main stem of each species was linearly related to cumulative growing degree days (GDD) since planting. Leaf production rates were faster for bulbous bluegrass, downy brome, Italian ryegrass, wild oat, and barley than for wheat, triticale, and jointed goatgrass. The main stem development stage when individual tillers appeared was similar in all species except under poor seedbed conditions in 1991, in which case lower-node tillers were delayed in the cereals and jointed goatgrass, but not in most of the weed species. Bulbous bluegrass, downy brome, and barley had the same percentage of plants produce the first four primary tillers on the main stem in both years; the other species showed more year-to-year variation. Seedling heights at full emergence were generally greater for large-seeded species. Small-seeded species compared to large-seeded species tended to have greater relative increases in plant height over time. Knowledge of comparative development rates between these weeds and cereals could provide information for development of growth models for each of the species and could also improve understanding of the competitive relationships between grass weeds and cereal grains.

Jointed goatgrass (Aegilops cylindrica Host. ♯3 AEGCY) has a quantitative requirement for vernalization in order to flower. In greenhouse and field studies, increasing periods of vernalization progressively reduced the number of days needed for plants to mature following transfer from the cold treatment to favorable growing conditions. Plants that had been vernalized at 3 ± 2 C for 8 weeks as imbibed seed took 120 days to flower following transfer to the greenhouse. Unvernalized controls flowered 197 to 222 days after planting in the greenhouse. Lengthening periods of vernalization from 2 to 8 weeks increased the number of seedheads per plant and dry weight per seedhead. Vernalized plants partitioned more dry matter into seedheads than unvernalized controls. The ratio of seedhead dry weight to vegetative shoot dry weight increased with duration of vernalization, even though vernalization did not alter total shoot dry-matter production. In field studies, plants that were established in the fall flowered sooner and more synchronously after resumption of growth in the spring than those that were planted in the spring and flowered in the summer. Plants seeded after May failed to flower in the same summer.

Jointed goatgrass is a winter annual grass weed which is believed to have been introduced into North America as a contaminant in winter wheat seed. Although jointed goatgrass was first discovered in some states early in the 20th century, changing wheat production practices during the past 25 yr have encouraged its spread and increase. Winter wheat producers in the western United States are concerned about the lack of adequate selective control measures for this weed. Jointed goatgrass and wheat share the D chromosome in common and have similar growth habits. Jointed goatgrass lowers winter wheat yield by competing for growth requirements, reducing harvesting efficiency, and lowering crop quality by contaminating harvested grain. Jointed goatgrass is well adapted to stubble-mulch or reduced tillage crop production, particularly in regions where climate limits cropping options to the winter wheat-fallow rotation or continuous wheat. This review summarizes jointed goatgrass seed germination, dormancy, physiology, yield loss estimates in winter wheat, and both herbicidal and non-chemical methods of managing jointed goatgrass.

Laboratory experiments were conducted to assess the influence of surfactants applied with or without nitrogen on MON 37500 foliar absorption by Bromus tectorum, Bromus japonicus, Aegilops cylindrica, Triticum aestivum, Chorispora tenella, and Lactuca serriola. MON 37500 absorption in B. tectorum and B. japonicus increased from 40% 24 h after treatment (HAT) to 48% 48 HAT, averaged across surfactants with no added nitrogen. Averaged across nitrogen source and species, nonionic surfactant, ethylated seed oil, and organosilicate provided comparable enhancement of MON 37500 absorption (56 to 68%), whereas crop oil concentrate provided only 27 to 29% absorption under the same conditions. Averaged across species and surfactant class, urea ammonium nitrate had the greatest effect on MON 37500 absorption (68%), compared to ammonium sulfate (59%) or no nitrogen (40%). Nitrogen, regardless of the type, significantly improved foliar absorption of MON 37500. MON 37500 absorption by species was 71, 63, 57, 57, 49, and 38% in C. tenella, B. japonicus, T. aestivum, A. cylindrica, B. tectorum, and L. serriola, respectively, when averaged across surfactants and nitrogen. Densely pubescent B. japonicus leaves did not retain significant amounts of MON 37500 following a primary leaf wash.

Jointed goatgrass (Aegilops cylindrica) is a serious problem for winter wheat producers throughout the western U.S. Interference from this weed can severely reduce grain yield and contaminate harvested grain, resulting in dockage losses. There are currently no selective herbicides registered for controlling jointed goatgrass in wheat. Imazamox, an imidazolinone herbicide, was applied to an imidazolinone herbicide-resistant (IMI) wheat mutant of the winter wheat cultivar ‘Fidel.’ Jointed goatgrass control from spring postemergence application of imazamox ranged from 61 to 97% when applied at 36 g/ha. Negligible crop injury from imazamox treatment was observed at 36 g/ha at several locations under dryland environments in the U.S. Pacific Northwest. Wheat yield was increased 19 to 41% by imazamox treatment in three of four experiments. Percent dockage resulting from jointed goatgrass spikelet contamination of harvested wheat grain was eliminated by imazamox treatment. Introduction of the IMI trait into commercial wheat cultivars could provide an effective method for selective control of jointed goatgrass in winter wheat.

Net (apparent) photosynthesis rate (Pn) of jointed goatgrass (Aegilops cylindrica Host # AEGCY) leaves in the greenhouse became light saturated at a photosynthetic photon flux density (PPFD) of about 1000 μE·m–1-2·s–1 with a maximum Pn of 27 mg CO2 ·dm–2 ·h–1. Diffusive resistance to water vapor (rl) of adaxial leaf surfaces was 43% that of abaxial surfaces, in part, because stomatal density was 50% greater on adaxial leaf surfaces than on abaxial surfaces. Dark respiration rate (Rd) was 1.6 mg CO2 ·dm−2·h−1. Light compensation point (CPl) was 21 μE·m−2·s−1 and CO2 compensation point (CPc) was 32 ppmv. In the field, where light intensity and temperature were greater than in the greenhouse, leaves became light saturated for Pn at a higher intensity, and Rd and CPl were three times greater than in the greenhouse. Pn and Rd of spikes at anthesis were at least 30% less and 200% greater, respectively, than the values for leaves.

In three replacement series experiments, winter wheat (Triticum aestivum L.), jointed goatgrass (Aegilops cylindrica Host. #3 AEGCY), and downy brome (Bromus tectorum L. # BROTE) were paired in all possible combinations to determine competitive relationships during vegetative growth. Under growth chamber conditions of ample fertility and soil moisture and day/night temperatures of 18/10 C, relative yield totals for the three species were similar, indicating that they compete for the same resources. Both winter wheat and jointed goatgrass had greater plant growth and higher relative crowding coefficients than downy brome, which indicated a hierarchy of relative competitiveness of winter wheat > jointed goatgrass >> downy brome. In other growth chamber studies, winter wheat was slightly more competitive than jointed goatgrass regardless of fertility levels. Winter wheat was the superior competitor at 18/10 C and −33 kPa (soil moisture), whereas jointed goatgrass was superior at 27/10 C and −300 kPa, conditions that are frequently encountered in the Pacific Northwest.

In most cases, a herbicide must traverse the cell wall, the plasma membrane, and organellar membranes of a plant cell to reach its site of action where accumulation causes phytotoxicity. The physicochemical characteristics of the herbicide molecule including lipophilicity and acidity, the plant cell membranes, and the electrochemical potential in the plant cell control herbicide absorption and accumulation. Most herbicides move across plant membranes via nonfacilitated diffusion because the membrane's lipid bilayer is permeable to neutral, lipophilic xenobiotics. Passive absorption of lipophilic, ionic herbicides or weak acids can be mediated by an ion-trapping mechanism where the less lipophilic, anionic form accumulates in alkaline compartments of the plant cell. A model that includes the pH and electrical gradients across plant cell membranes better predicts accumulation concentrations in plant cells of weak acid herbicides compared to a model that uses pH only. Herbicides also may accumulate in plant cells by conversion to nonphytotoxic metabolites, binding to cellular constituents, or partitioning into lipids. Evidence exists for herbicide transport across cell membranes via carrier-mediated processes where herbicide accumulation is energy dependent; absorption is saturable and slowed by metabolic inhibitors and compounds of similar structure.

In a kiln experiment, temperatures of 200 to 400 C for 120 sec reduced germination of jointed goatgrass seeds 50 to 100%. Postharvest field burning of wheat and jointed goatgrass stubble destroyed 43 to 64% of the jointed goatgrass spikelets located on the soil surface. Seeds contained in spikelets that were minimally burned (slightly browned) germinated 32 to 65%, while seeds contained in spikelets moderately (less than 50% charred) and severely burned (greater than 50% charred) germinated 5 and 0%, respectively. Field burning destroyed 90% or more of jointed goatgrass seeds in spikelets located on the soil surface. Burning may be a feasible method for controlling small infestations of this weed.

Crop yield loss–weed density relationships critically influence calculation of economic thresholds and the resulting management recommendations made by a bioeconomic model. To examine site-to-site and year-to-year variation in winter Triticum aestivum L. (winter wheat)–Aegilops cylindrica Host. (jointed goatgrass) interference relationships, the rectangular hyperbolic yield loss function was fit to data sets from multiyear field experiments conducted at Colorado, Idaho, Kansas, Montana, Nebraska, Utah, Washington, and Wyoming. The model was fit to three measures of A. cylindrica density: fall seedling, spring seedling, and reproductive tiller densities. Two parameters: i, the slope of the yield loss curve as A. cylindrica density approaches zero, and a, the maximum percentage yield loss as A. cylindrica density becomes very large, were estimated for each data set using nonlinear regression. Fit of the model to the data was better using spring seedling densities than fall seedling densities, but it was similar for spring seedling and reproductive tiller densities based on the residual mean square (RMS) values. Yield loss functions were less variable among years within a site than among sites for all measures of weed density. For the one site where year-to-year variation was observed (Archer, WY), parameter a varied significantly among years, but parameter i did not. Yield loss functions differed significantly among sites for 7 of 10 comparisons. Site-to-site statistical differences were generally due to variation in estimates of parameter i. Site-to-site and year-to-year variation in winter T. aestivum–A. cylindrica yield loss parameter estimates indicated that management recommendations made by a bioeconomic model cannot be based on a single yield loss function with the same parameter values for the winter T. aestivum-producing region. The predictive ability of a bioeconomic model is likely to be improved when yield loss functions incorporating time of emergence and crop density are built into the model's structure.

Root absorption of subtoxic levels of metribuzin and its ethylthio analog (ethyl-metribuzin) by downy brome, jointed goatgrass, and winter wheat increased by a factor of three to five times as temperature increased from 10 to 20 C. Absorption of ethyl-metribuzin per gram dry weight was similar for all three species. Absorption and distribution of ethyl-metribuzin, but not metribuzin, were similar per gram dry weight in downy brome and jointed goatgrass. Absorption of metribuzin per gram dry weight was lower for winter wheat than for the other two species at 20 C. In general, the ratio of absorbed ethyl-metribuzin detected in shoots to that in roots was less in winter wheat and jointed goatgrass than in downy brome. The absorption by roots of 14C-herbicides relative to water was similar for winter wheat and jointed goatgrass. Absorption of both 14C-herbicides by winter wheat and jointed goatgrass was nonpreferential with respect to water absorption at 10 and 15 C. However, at 20 C 14C-herbicide absorption was reduced 5 to 30% with respect to water absorption. Downy brome absorption of 14C-herbicides with respect to water was 30 to 50% less than that of the other two species.

Jointed goatgrass is a major weed in the wheat-producing areas of the western U.S. It shares the D genome with wheat, and interspecific hybrids between the two species occur in the field. The objective of this research was to determine if wheat X jointed goatgrass hybrids could serve to transfer genes from wheat to jointed goatgrass. A backcrossing program was initiated in the greenhouse between wheat X jointed goatgrass hybrids and either jointed goatgrass or wheat to determine the potential for seed set and the restoration of self-fertility. Seed was set by backcrossing with either species as the recurrent parent. Female fertility increased from 2% in the hybrid to 37% in the BC2 plants with jointed goatgrass as the recurrent parent. Partial self-fertility was restored in the second backcross (BC2) generation using jointed goatgrass as the recurrent parent. This indicates that genes could be transferred between wheat and jointed goatgrass after only two backcrosses. The number of bivalents observed in the plants during meiosis appeared to be key to increasing female fertility and self-fertility. Based on the results of this study, it is possible for genes to move from wheat to jointed goatgrass. Any release of a herbicide-resistant wheat should be accompanied by a management plan that would minimize the potential for gene movement between these species.

Field studies were conducted from 1990 through 1997 to evaluate the long-term effect of 2- and 3-yr rotations on the control of downy brome, jointed goatgrass, and feral rye in winter wheat. At the completion of the study, jointed goatgrass and feral rye densities averaged 8 plants/m2 and < 0.1 plant/m2 for the 2- and 3-yr rotations, respectively. Downy brome densities averaged < 0.5 plant/m2 for both the 2- and 3-yr rotations, with no treatment differences observed. Winter annual grasses were not eradicated after two cycles of the 3-yr rotations, but weed densities were reduced 10-fold compared to densities after one cycle and more than 100-fold compared with the 2-yr rotations. Wheat grain contamination with dockage and foreign material followed a similar trend. The 3-yr rotations were economically competitive with 2-yr rotations and provided superior control of the winter annual grass weeds.