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Modern cotton production (Gossypium hirsutum L.) in the United States relies on chemical and physical inputs that increase the environmental and monetary costs of managing the crop. Perennial groundcover crops (PGCC) may reduce inputs by persisting in the interrow spaces of the cotton crop during summer months. A 2‐year field study was conducted in Florence, SC, to evaluate growing PGCCs with cotton using a 4 × 4 Latin square consisting of four cover crop treatments: (1) a fallow, unplanted control, (2) annual ryegrass (Lolium multiflorum Lam.) monoculture, (3) a binary red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) mixture, and (4) a trinary mixture of annual ryegrass, red clover, and white clover. Fallow and annual ryegrass treatments were killed with a burndown herbicide application, while treatments containing clovers were mowed. Plots were strip‐tilled and planted with cotton in May each year. Interrow biomass, weed and thrips populations, and perennial clover populations were collected from June to October along with annual lint yields from cotton harvest in October. Results indicated that interrow biomass (2000–3000 kg ha−1), weeds (20 weeds m−2), and thrips (five thrips per five plants−1) populations were lowest in treatments containing perennial clovers, but drought and heat stress reduced clover stands within two growing seasons. Lint yield was not affected by incorporating perennial clovers into the interrow spaces of the crop. Perennial groundcover crops may provide an effective alternative to chemical weed control in cotton, but necessitate management changes to be viable in the southeastern United States. Core Ideas: Perennial groundcover crops reduced interrow weedy biomass compared to fallow or annual cover crops.Perennial groundcover crops reduced weed and thrips populations by 60% and 80%, respectively.Red and white clover mixtures persisted under irrigation, but not under drought and heat stress.Cotton lint yields were not affected by maintaining perennial clovers in cotton interrow spaces.Cost projections indicate perennial groundcover crops may reduce chemical input costs for cotton producers. [ABSTRACT FROM AUTHOR]

New atra paspalum (Paspalum atratum Swallen) accessions were found to be differentially grazed by cattle, without differences in herbage accumulation and nutritive value. This study aimed to evaluate cattle preference, morphological and anatomical leaf traits, and their relationships at four sampling events. Five new atra paspalum accessions and the cultivar Cambá were used. The experimental unit was a 2 m × 2 m plot. Treatments were replicated four times in a completely randomized design. Cattle preference was determined in spring (December 2016 and 2017), summer (March 2017), and autumn (May 2017) using six steers Bos spp. that grazed the plots for 4 h on two consecutive days. Plant height, leaf‐blade length, leaf‐blade width, and the proportions of five leaf tissues at three leaf regions were measured at each date. The proportion of the leaf that is curved was measured in December 2017. Cattle preference was variable among accessions and sampling events. Some accessions were shorter, with shorter and more flexible leaves than Cambá (p < 0.05). The proportion of lignified tissues was greater during the spring (2016 and 2017) and summer (7%–23%) than in the autumn. One accession had the lowest proportion of lignified tissue in the warm season (8%–12%) but the highest during the fall (around 15%). The same accession had the fewest primary vascular bundles in the warm season. Cattle preference was negatively correlated with the proportion of lignified tissues, the number of primary vascular bundles, plant height, and leaf‐blade length. Cattle preference was affected by the growing season and reduced by greater presence of leaf structural tissue. Core Ideas: Variability for cattle preference was observed among accessions of Paspalum atratum.Plant height, leaf length, and the number of primary vascular bundles negatively affected cattle preference.Cattle preference seemed to be limited by the fraction of leaf‐supporting tissue. [ABSTRACT FROM AUTHOR]

Seasonal and annual changes in stubble characteristics can affect the regrowth of warm‐season perennial grasses. Understanding these changes and their effects on forage accumulation rate (FAR) can improve defoliation management. Our objective was to describe and relate variations in stubble characteristics with FAR during regrowth of four palisadegrasses [Brachiaria brizantha (Hochst. Ex A. Rich.) Stapf. syn. Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster], genotypes Marandu, Xaraés, Arapoty, and Capiporã, and one signalgrass [Brachiaria decumbens (Stapf.) syn. Urochloa decumbens (Stapf.) R.D. Webster] cultivar Basilisk, in southeastern Brazil. Plots were harvested at 15‐cm stubble height every 28 d during the warm season and 42 d during the cool season of years 2005–2006 and 2007–2008. Stubble mass was ∼1,070 kg DM ha−1 greater in the cool than warm season, whereas FAR was less in the cool season. Arapoty and Basilisk showed generally less FAR (∼45 kg d−1) and stubble leaf, stem, dead material, and total mass during the warm season than more productive grasses Capiporã and Xaraés (∼63 kg d−1). Leaf and canopy photosynthesis varied over seasons and years, but they were similar among grasses despite differences in stubble characteristics and FAR. Marandu accumulated more leaf in the stubble than other grasses, resulting in greater residual leaf area index, but it did not increase FAR. Under less favorable growth conditions, grasses increased stubble herbage mass (SHM). More productive grasses generally present greater SHM and leaf mass, indicating that stubble characteristics play an important role in the regrowth of brachiariagrasses. Core Ideas: Stubble characteristics play an important role in the regrowth of brachiariagrasses.Grasses increased stubble herbage mass and reduced forage accumulation rate during the cool season.Marandu palisadegrass had greater stubble leaf mass, but similar accumulation rate to less productive grasses.Capiporã and Xaraés palisadegrasses had greater stubble herbage mass and forage accumulation rate. [ABSTRACT FROM AUTHOR]

Turf‐type bermudagrass is susceptible to winterkill when grown in transition zone climates. Minimizing water use in turfgrass management is of societal significance. African bermudagrass (Cynodon transvaalensis Burtt‐Davy) has been extensively used to cross with common bermudagrass (C. dactylon Pers. var. dactylon) in the creation of F1 hybrid cultivars. Little information regarding the molecular basis of winter survivability and drought resistance in African bermudagrass is available. Accordingly, the objectives of this study were to quantify genetic variability and identify quantitative trait loci (QTL) associated with winter survivability traits (spring greenup, SG; spring greenup percent green cover, SGPGC; winterkill, WK), and leaf firing (LF) in African bermudagrass. A total of 109 first‐generation self‐pollinated (S1) progeny of 'OKC1163' were evaluated in a field trial in a randomized complete block design with three replications for four seasons. Significant genetic variation existed for all the traits examined, and the broad‐sense heritability estimates ranged from.36 to.54 for the winter survivability traits and.80 for LF. Ten QTL were identified for winter survivability traits and two for LF based on a preexisting high‐density linkage map, which was aligned, reoriented, and renamed as to a recently published reference genome. Seven of 12 QTL were consistently identified at least in 2 yr. The colocation of two QTL, one for winter survivability and another for LF, suggests the possibility of improving both traits together. Findings provide new insights to genetic control of winter survivability traits and LF and contribute genetic resources for marker‐assisted selection in turf‐type bermudagrass improvement. Core Ideas: Winter survivability traits and LF are critical to the development of new turf‐type bermudagrass cultivars.One hundred and nine S1 African bermudagrass progeny were characterized for winter survivability and LF. We identified 10 QTL associated with winter survivability and two QTL for LF. [ABSTRACT FROM AUTHOR]

Grazing cover crops can improve land‐use efficiency and diversification, making agricultural enterprises more resilient to market fluctuations. We investigated how grazing intensity affects cover crop forage responses and cotton (Gossypium hirsutum L.) lint yield. Cover crops were a rye (Secale cereale L.)–oat (Avena sativa L.) mixture managed as follows: no grazing + 34 kg N ha–1 (NG34), no grazing + 90 kg N ha–1 (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG), compared with a no cover crop control. All grazed treatments received 90 kg N ha–1. Average postgrazing herbage mass (HM) for HG, MG, and LG was 520, 1,350, and 2,120 kg dry matter ha–1, respectively. Herbage accumulation (HA) rate was greater for LG than HG, with MG being intermediate. Forage crude protein (CP) and in vitro digestible organic matter (IVDOM) concentrations decreased as the season progressed and were usually greater for HG than MG and LG. Stubble residue before cover crop termination was greatest for NG34 and NG90 in 2018 and 2020, however, in 2019 NG90 had greater stubble residue before termination than NG34 (7540 vs. 6650 kg dry matter ha–1). Heavy grazing resulted in greater weed proportion (17 vs. 6.5%) and lesser soil cover (49 vs. 70%) than nongrazed cover crops. Cotton lint yield was low and unaffected by treatment, reaching a maximum of 520 kg ha–1 in 2019. Although lint yield was not affected by cover crop fertilization or grazing during 3 yr, HG reduced soil cover and increased weed presence. Core Ideas: Herbage accumulation rate was greater for light grazing than heavy grazing.Heavy grazing resulted in lesser soil cover and greater weed proportion than no‐grazing.Forage nutritive value was greater for heavy grazing than light grazing and decreased with maturity.Applying different grazing intensities on cover crops did not affect cotton lint yield. [ABSTRACT FROM AUTHOR]

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Intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth and D.R. Dewey], bred for high grain yield, has become the first perennial grain in North America and is commercialized under the tradename Kernza. The expansion of this crop from the U.S. Midwest to areas with milder winters would require an understanding of its vernalization requirements for flowering and the availability of genetic diversity for this trait. The goal of this research was to determine the length of the cold period required for vernalization in Kernza intermediate wheatgrass. Two treatment factors (population and length of cold incubation period) were evaluated. Seeds from eight breeding populations from Kansas and Minnesota were evaluated in growth chambers at 5 °C and 10 h light for cold periods from 3 to 9 wk. The percentage of plants that flowered increased from 30 to 96% as the length of the cold incubation period increased from 3 to 7 wk following a sigmoid model. For most yield components, no changes were observed after 7 wk of cold incubation. There were no differences among populations for most traits and there was large within‐population phenotypic diversity. These results confirm that Kernza intermediate wheatgrass populations have moderate vernalization requirements. Further research is needed to confirm the feasibility of breeding Kernza with lower vernalization requirements. Core Ideas: Kernza has moderate vernalization requirement for flowering.Plant heading percentage increased from 3 to 7 wk at 5 °C and 10 h light.Plant heading percentage did not differ among Kernza populations from KS and MN exposed to cold. [ABSTRACT FROM AUTHOR]

Intermediate wheatgrass (IWG) [Thinopyrum intermedium (Host) Barkworth & D. R. Dewey subsp. intermedium] is being domesticated as a perennial grain crop. Advanced grain‐type IWG populations display variability in key physiological parameters related to seed development, making it difficult to determine grain harvest timing. A quantitative literature review of cool‐season grasses informed the modeling of IWG field trial data. Results revealed that multiple species exhibited a consistent multiphase dry‐down pattern from anthesis to a stabilized moisture content, which often included a rapid dry‐down phase that presaged maximum seed dry matter and gave insight into the relationship between floret shatter and maximum seed yield. A field trial was conducted at three locations in which IWG spikes were repeatedly sampled postanthesis and divided into three fractions to measure physiological patterns over growing degree days (GDDs). Similar to literature review results, IWG demonstrated a rapid dry‐down phase that started when seed moisture content was between 44.7 and 52.8% and decreased at a rate of −0.12 to −0.20% GDD−1 during this phase. At all locations, florets began shattering before seeds reached maximum dry matter, which resulted in reduced floret site utilization. Seed from distal fractions reached 95% dry matter 135 GDDs earlier than seed from basal fractions, while basal seeds were 21% larger than distal seeds. Timing of maximized seed yield per spike ranged from 530 to 701 GDDs after mid‐anthesis provided a starting point for estimating optimum IWG seed harvest timing under high and low shattering conditions and also supports the importance of repeated measurement of seed moisture to pinpoint optimal harvest time. Core Ideas: Intermediate wheatgrass (IWG) grown for grain lacks research for modeling yield components.A quantitative literature review of perennial grass seed crops informed IWG model hypotheses.Perennial grasses exhibited multiphase moisture loss that regulated maximum seed dry matter.The onset and magnitude of shattering in IWG influenced the timing of maximum seed yield. [ABSTRACT FROM AUTHOR]

Lignin is a phenolic biopolymer that limits the intake potential and energy availability of forage crops. In order to understand the lignification process, enzymatic and biochemical studies were conducted at four different growth stages of tall fescue (Festuca arundinacea Schreb.). An increase in phenylalanine ammonia lyase and tyrosine ammonia lyase activity was observed with advancement of growth from first node palpable stage to third node palpable stage with a decrease at spikelet emergence stage. Cinnamoyl‐CoA reductase and peroxidase exhibited a continuous significant (p <.05) increase and positive correlation with lignin concentration. Cinnamyl alcohol dehydrogenase exhibited a significant (p <.05) positive correlation with lignin concentration, suggesting its probable exclusive role in tall fescue lignification. Cellulose and total phenol exhibited a 13.0 and 71.8% increase, whereas pectin and crude protein exhibited a significant (p <.05, p =.0001) decrease of 65.1 and 15.4%, respectively, with the growth advancement from first node palpable to spikelet emergence stage. Klason lignin also exhibited a dramatic 9.4‐fold increase from vegetative to reproductive stage. The enzymatic and biochemical alterations were closely associated with the lignification process. This study provides an integrated picture of the enzymatic and biochemical alterations that accompany changes in lignin deposition in tall fescue. Core Ideas: Cinnamyl alcohol dehydrogenase enzyme exhibits an exclusive role in the process of lignin deposition in tall fescue.Cinnamoyl‐CoA reductase and peroxidase exhibit a continuous significant increase and positive correlation with lignin.Lignin exhibits a 9.54‐fold increase from vegetative to reproductive stage. [ABSTRACT FROM AUTHOR]

Manganese is an essential nutrient and plays key roles in photosynthetic processes, including in NAD‐malic enzyme (NAD‐ME)‐type C4 plants as an activator of NAD‐ME. However, little is known about the Mn requirements of switchgrass (Panicum virgatum L.). To study Mn requirements for optimum growth and biomass production, a lowland ('Alamo') and an upland ('Cave‐in‐Rock') switchgrass ecotype were grown with either washed sand, vermiculite, or perlite and fertilized with nutrient solutions ranging in [Mn] from 0 to 200 μM. In the perlite experiment, pearl millet [Pennisetum glaucum (L.) R. Br. 'KGraze'] was also grown. Shoot [Mn] was highly responsive to increasing Mn in the nutrient solution. When grown in washed sand and vermiculite, tissue [Mn] remained above those normally considered deficient, even in the 0 μM Mn treatment, and no Mn treatment effects on biomass production were found. In perlite, end‐of‐season shoot [Mn] were <5 mg kg−1 in all entries when no Mn was supplied, and a decrease in biomass production compared with 10–25 μM Mn treatments was observed for Alamo and KGraze, but not for Cave‐in‐Rock. Relative chlorophyll contents of switchgrass were lower in the 0 μM Mn treatment than in other treatments late in the season, but in KGraze, they were low early in the season and increased throughout the season, resulting in less pronounced (but still significant) differences at late stages. Overall, results indicated that switchgrass and pearl millet respond differently to low Mn availability and that even low levels of shoot tissue [Mn] allow switchgrass to maintain biomass production. [ABSTRACT FROM AUTHOR]

Increasing temperatures associated with climate change will be the next challenge for crop improvement, especially for turfgrass species that are often grown in urban green spaces. Previous research on turfgrass heat stress tolerance has been limited to a small number of species and cultivars with different heat stress conditions between studies; therefore, we assessed heat stress tolerance of 34 turfgrasses representing 14 species. Four replicates of each entry were established for at least 12 wk and then subjected to 49 d of heat stress (35/25 °C day/night) followed by a 4 wk recovery period (25/15 °C day/night). Turfgrass entries were assessed using the normalized difference vegetative index, the percentage of green obtained with digital image analysis, and membrane stability estimated by electrolyte leakage. Buffalograss [Bouteloua dactyloides (Nutt.) J.T. Columbus], Kentucky bluegrass (Poa pratensis L.), tall fescue [Schedonorus arundinaceus (Schreb.) Dumort], and slender creeping red fescue (Festuca rubra ssp. littoralis) were more tolerant of heat stress than the other species. The Canada bluegrass (Poa compressa L.), blue grama [Bouteloua gracilis (Willd. ex Kunth.) Lag. ex Griffiths], and smooth brome (Bromus inermis Leyss.) cultivars were all tolerant of heat stress; however, only one cultivar for these three species was tested, making species‐wide generalizations difficult. In some cases, the cultivars and/or selections within a given species differed in heat stress response. Almost all entries were able to recover from the heat stress by the end of the recovery period. Altogether, we were able to identify turfgrasses that should perform adequately in high‐temperature urban environments. [ABSTRACT FROM AUTHOR]

Alfalfa (Medicago sativa L.) can enhance the supply of nutritious forage when interseeded into semiarid native grassland. Alfalfa is a high water‐using species; therefore, a possible trade‐off between soil water depletion and nutritive value merits study. We determined the effects of interseeding three alfalfa cultivars at two densities on crude protein (CP) and digestible organic matter (DOM) accumulations, the water footprint (WF, m3 evapotranspiration kg−1) of CP and DOM accumulation at two row spacings, and the marginal cost (MC) of such trade‐offs. Nutritive values and accumulation of CP and DOM for mixtures with alfalfa planted at 36‐ or 71‐cm row spacing did not differ in 2018 (P >.05), as both spacings reduced the WF over grass only (P <.0001). Alfalfa presence reduced the WF (P <.001) with respect to CP and DOM accumulation from 20.17 and 3.07 m3 kg−1 in the grass‐only control to 10.14 and 2.22 m3 kg−1 in alfalfa–grass mixtures, respectively. Interseeding alfalfa in wide rows had 23 and 26% less MC of revenue increment than interseeding in narrow rows, relative to grass only in Years 2 and 3, respectively (P <.01). Hay‐type cultivars NuMex Bill Melton and WL 440HQ enhanced the forage mixture nutritive value more than the grazing‐type Falcata–Rhizoma blend, mainly driven by greater alfalfa growth. Interseeding alfalfa into native grasses in wide rows can increase the efficiency of water use (lower WF) by enhancing forage nutritive value at low MC, thereby inducing a minimal trade‐off in soil water consumption. [ABSTRACT FROM AUTHOR]

Paspalum notatum Flüggé is an apomictic grass used for forage and turf. The recent generation of a sexual synthetic tetraploid population of the species provides the unique advantage to exploit heterosis by accumulating favorable alleles through recurrent selection cycles. The objective was to evaluate recurrent phenotypic selection (RPS) and recurrent selection based on combining ability (RSCA) as breeding methods. The best sexual genotypes in terms of warm‐season growth from a sexual synthetic tetraploid population were selected by RPS and RSCA. The selected genotypes were polycrossed and two new sexual populations were created, which were crossed with superior apomictic genotypes. Both methods allowed obtaining families that were evaluated for summer, fall, and spring growth. Breeding values and heterosis were also calculated. Summer growth for RPS families was greater than for RSCA families (33.1 and 29.08 g plant−1, respectively); however, fall, spring, and accumulated growth were similar. The breeding value for RPS sexual parents was greater than for RSCA sexual parents for summer growth, whereas those for fall and spring growth were similar. A greater level of families with heterosis (80%) was observed for RPS than for RSCA (30%) for summer growth, whereas the levels for fall and spring growth were similar. These results indicate that both breeding methods were successful in improving tetraploid P. notatum. They increased the mean value of the progenies and produced families superior for forage yield by accumulating favorable alleles. [ABSTRACT FROM AUTHOR]

Forage species with greater nutritive value have the potential to positively affect animal responses. 'Performer' switchgrass (Panicum virgatum L.) was released because of greater digestibility and lower lignin concentrations as compared to 'Alamo' and 'Cave‐in‐Rock.' However, the relationship between nutritive value, canopy characteristics, and dry matter yield for this species has not yet been established. The goal of this study was to determine in vitro true digestibility (IVTD), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) as a function of a wide range of defoliation management strategies to aim optimize production of nutritious forage. Treatments were the factorial combination (4 × 4) of defoliation height (DH; clipped to 10, 20, 30, and 40 cm) and defoliation frequency (DF; clipped every 3, 6, 9, and 12 wk). The range of digestibility values was greater due to DF (from 590–779 g kg−1 when averaged across DH treatments) than DH treatments (from 675–692 g kg−1 when averaged across DF treatments). In general, frequent defoliation resulted in greater IVTD and CP but lower yields; however, there were interaction effects of DF × DH for all response variables. With the exception of NDF, all response variables had strong correlations with dry matter yield, canopy height, and leaf/stem ratio. Although there are tradeoffs when managing for productivity and nutritive value, there is a wide range of defoliation management options for 'Performer' switchgrass that provide flexibility in terms of harvesting schedules to optimize productivity and persistence of nutritious forage. [ABSTRACT FROM AUTHOR]

Big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L.) were collected from remnant Midwestern prairies and evaluated as individual prairie accessions in replicated space-transplanted nurseries near Mead, NE, Ames, IA, and West Lafayette, IN. The objective was to determine the extent of differences among the accessions for plant biomass (g plant-1) and biomass quality, the extent of strain x location interactions, and the relationship between geographical locations of collection sites and evaluation locations for plant biomass production. Plant biomass has been used previously as a measure of plant adaptation and fitness. Big bluestem and indiangrass accessions differed significantly (P < 0.05) for plant biomass at all locations. Strain mean squares for plant biomass were 10x greater than strain x location effects for big bluestem and were not significant for indiangrass, indicating a general lack of specific adaptation across the Midwest. Accessions were identified that had high plant biomass at all three locations. These accessions should have value in breeding programs and for use in revegetation. Regression analyses were used to test the effect of north-to-south, east-to-west, and direct distances between the collection sites and the evaluation locations on plant biomass. The most important distance effects were the north-to-south effects, which were significant for plant biomass for big bluestem at all locations and for indiangrass at West Lafayette. Moving northern big bluestem accessions south resulted in reduced plant biomass, with the opposite effect when southern accessions were moved north. Results support the regional adaptation of the best accessions and cultivars for these grasses. [ABSTRACT FROM AUTHOR]

Siberian wildrye (Elymus sibiricus L.) is a globally important cool-season forage grass for semiarid regions. However, its seed yield is often low or inconsistent. As previous studies examined the effects of row spacing and P and N levels on seed production of Siberian wildrye separately, this study was focused on the combined effects of four row spacings (30, 45, 60, 75 cm), four P application levels (0, 60, 90, 120 kg P ha-1), and four N application levels (0, 30, 60, 90 kg N ha-1). Treatments were established within a split-split-plot factorial arrangement, with main plots arranged in a randomized complete block design with four replicates. The field experiment was conducted on a Lithic Haprendoll soil type at the Guyuan farm in Hebei Province, China, during the 2010, 2011, and 2012 growing seasons with no supplemental irrigation. Narrow row spacing improved seed yield by increasing fertile tillers m-2, with 30 cm being the optimal row spacing. Phosphorus application increased seed yield by increasing spikelets per fertile tiller, with 90 kg P ha-1 being the optimal P application level. Nitrogen application had no significant influence on seed yield in any year. Path analysis structural equation modeling revealed that spikelets per fertile tiller and fertile tillers m-2 had significant and direct path coefficients with variances in seed yield. The best management practices for optimal seed yield of Siberian wildrye was 30-cm row spacing, 90 kg P ha-1, and no additional N beyond 109 g kg-1 available soil N under rain-fed conditions with annual rainfall <300 mm. [ABSTRACT FROM AUTHOR]

Well-managed irrigated pasture production can be optimized without nitrogen (N) fertilizer. The objective was to determine mixture and planting ratios of tall fescue (Schedonorus arundinacea Schreb.) (TF), meadow brome (Bromus riparius Rehm.) (MB), orchardgrass (Dactylis glomerata L.) (OG), timothy (Phleum pratense L.) (TIM), and perennial ryegrass (Lolium perenne L.) (PRG) with alfalfa (Medicago sativa L.) (ALF), birdsfoot trefoil (Lotus corniculatus L.) (BFTF), or cicer milkvetch (Astragalus cicer L.) (CMV) that maximize productivity. Planting ratios were 0:100 (grass:legume), 25:75, 50:50, 75:25, and three 100:0 grass monocultures fertilized at 0, 67, and 134 kg N ha-1. Seasonal production of TF-ALF was 12.69 Mg ha-1, equal to TF fertilized at 134 kg N ha-1. ALF mixtures with MB, OG, TIM, and PRG produced 12.57, 10.97, 11.77, and 10.74 Mg ha-1, respectively, and 8 to 40% more than grasses receiving 134 kg N ha-1. Production of BFTF mixtures with TF, MB, and OG were 11.69, 11.45, and 9.95 Mg ha-1, respectively, equal to their respective grass monoculture receiving 134 kg N ha-1. The BFTF-TIM and BFTF-PRG mixtures averaged 12% more forage than grass monocultures receiving 134 kg N ha-1. Production of CMV-grass was similar to that of grasses receiving 67 kg N ha-1. Seasonal forage distribution was more uniform in ALF- and BFTF-grass mixtures, averaging 30% more at the second and third harvests than fertilized grasses. The TF and MB legume mixtures averaged 7% more production in the 50:50 planting ratios than the other two grass-legume mixtures, while the 50:50 and 25:75 ratios of OG and TIM-legume mixtures averaged 12% more than the 75:25 and the 25:75 PRG-legume planting ratio averaged 9% more than the 50:50 and 75:25. Forage production of grass-legume mixtures can equal or exceed fertilized grass monocultures and with more uniform distribution over the growing season. [ABSTRACT FROM AUTHOR]

Estimating genetic parameters is an essential step in breeding by recurrent selection to maximize genetic gains over time. This study evaluated the effects of selection on genetic variation across two successive cycles (C1 and C2) of a 'Summer'x'Kanlow' switchgrass (Panicum virgatum L.) population. Two progeny tests were planted in 2007 and 2011 near Mead, NE and respectively analyzed for 2 and 4 yr. Each test was a randomized complete block design, with four replicates of 34 halfsib families in single-row plots of 10 seedlings in C1 and with three replicates of 111 halfsib families in single-row plots of fve seedlings in C2. The C2 test included C0, C1, and parental populations for comparison. Multivariate mixed linear models revealed ample additive genetic variation for dry matter yield (DMY), Klason lignin (KL), and predicted ethanol yield (ETOH) in both cycles, with heritability ranging from 0.40±0.18 to 0.5±0.14 at the family level, from 0.22±0.17 to 0.36±0.22 at the individual level, and from 0.25 to 0.31 within family in C1. Matching values in C2 were: from 0.42±0.09 to 0.63±0.07, f rom 0.10±0.07 to 0.34±0.13, and from 0.12 to 0.48. More opportunity exists to improve DMY, with a coefficient of additive genetic variation of 11 to 32%, than KL (3-5%) or ETOH (3-6%). The traits were properly aligned for joint improvement for high DMY and reduced KL in C1, owing to favorable genetic correlations (rA=-0.33±0.11) and each having respective rA of 0.60±0.05 and -0.62±0.07 with ETOH. In C2, the rA between DMY and KL (-0.19±0.10) or ETOH (0.04±0.04) decreased towards zero, and that between KL and ETOH was moderately less negative (-0.35±0.15) . These results suggest a strong genetic basis for improvement of the traits and monitoring of their patterns every cycle to fnd the proper weights that maximize the breeding goal of designing the ideal bioenergy switchgrass. [ABSTRACT FROM AUTHOR]

Currently, the standard germination test (SGT) is the official test for evaluating seed viability in seed testing laboratories around the world. The SGT takes 3 to 4 wk to complete for most grasses, including the dormancy breaking treatment period. The tetrazolium test (TZT), however, offers quick viability determination within 24 to 48 h, even for dormant seeds. This study was conducted to compare SGT and TZT results for tall fescue (TF), annual and perennial ryegrass (ARG and PRG), orchardgrass (OG), bentgrass (BG), Kentucky bluegrass (KBG), and fine fescues (FF). A total of 3432 samples representing the seven species were evaluated for viability by SGT and TZT during 2009 to 2013 at the Oregon State University Seed Laboratory (OSUSL). According to the germination tolerance table of the Association of Official Seed Analysts (AOSA), both SGT and TZT results were within tolerance in 94.2% of TF samples, 95.2% of ARG samples, 90.4% of PRG samples, 93.7% of OG samples, 90.8% of FF samples, 83.9% of BG samples, and 42.4% of KBG samples. Dormancy was the main reason for higher viability by TZT results than by SGT in the same sample, causing the two test results to be out-of-tolerance. Based on these results, it can be concluded that the TZT can be used as an alternative viability test to the SGT for TF, ARG, PRG, OG, FF, and possibly for BG. However, the KBG has higher levels of dormancy, which brings the SGT below the TZT results, especially for freshly harvested seeds. [ABSTRACT FROM AUTHOR]

Temperature and photoperiod are key factors regulating plant growth and development. The objective of this study was to investigate the effects of temperature and photoperiod on tillering and rhizome formation in tall fescue [Lolium arundinaceum (Schreb.) Darby.]. Different genotypes were selected based on tillering ability and/or rhizome production. Plants were grown in growth chambers with a combination of different photoperiods and day/night temperatures: short photoperiod (9 h) and low temperature (day/night at 15/10°C) (SL), long photoperiod (18 h) and low temperature (LL), short photoperiod and high temperature (day/night at 25/15°C) (SH), and long photoperiod and high temperature (LH). The SL treatment resulted in significant increases in the number of tillers in the experiment and Genotype 1109 produced the maximum number of tillers. The number of rhizomes was increased under LL and LH conditions in three clonal lines. Our results suggested that the responses of tiller and rhizome development to temperature and photoperiod varied with genotypes; in addition, longer photoperiod appeared to promote rhizome formation, regardless of temperature, whereas lower temperature stimulated rapid tiller production in some genotypes of tall fescue. This study will help to determine the performance of tall fescue under the longer/shorter photoperiod and variable temperature conditions in different parts of United States. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) is a candidate for cellulosic bioenergy feedstock development in many parts of North America, Europe, and Asia. Breeding for increased biomass yield is a viable and desirable research objective to improve both economic and energy yields per hectare. The objectives of this study were to estimate progress from (i) selection for biomass yield in upland switchgrass, (ii) selection for winter survival, biomass yield, and biomass quality in lowland switchgrass, and (iii) advanced-generation heterosis effects in four upland × lowland hybrid switchgrass populations. Selection for increased biomass yield in upland switchgrass resulted in mean genetic gains for of 0.71 Mg ha-1 per cycle (8% per cycle = 4% yr-1) for biomass yield. Selection for increased biomass yield in lowland switchgrass resulted in mean genetic gains of 0.89 Mg ha-1 (18% = 1% yr-1) for biomass yield. Mean high-parent heterosis between upland and lowland ecotypes was 3.57 Mg ha-1 (43%). These gains in biomass yield resulted in significant increases in ethanol production for a fermentation platform or high heating value for a combustion platform. Biomass yield is a moderately heritable trait in switchgrass and it can be readily improved in both upland and lowland populations using conventional breeding methods. [ABSTRACT FROM AUTHOR]

Native perennial grasses have potential as lowinput biomass feedstocks. Basin wildrye [Leymus cinereus (Scribn. & Merr.) Á. Löve] is the largest native grass in western North America but is susceptible to defoliation. Creeping wildrye [Leymus triticoides (Buckley) Pilg.] is a shorter less productive grass with durable rhizomes and higher forage quality. Two creeping wildrye pseudo-backcross populations derived from interspecific hybrids were used to identify quantitative trait loci (QTL) controlling plant height, rhizome spreading, flowering, postanthesis biomass yield, cellulosic fiber, lignin, and protein traits using a linkage map comprising 376 expressed sequence tags and 423 other DNA markers. Biomass yields of the F1 hybrids and pseudo-backcross populations were significantly greater than creeping wildrye with some genotypes nearly equal to or greater than basin wildrye. Rhizome spreading and forage quality of the creeping wildrye pseudo-backcross populations were significantly greater than basin wildrye. Six of nine plant height QTL overlap with biomass QTL. Three flowering QTL detected in both populations overlap with fiber QTL. Plant height and flowering QTL were aligned to genes controlling dwarfing, photoperiod response, and vernalization in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) using the Brachypodium distachyon (L.) P. Beauv. genome reference sequence. Evidence suggests that genetic mechanisms controlling plant height and flowering are conserved among temperate grasses and reveals pathways for improving biomass production and forage quality. [ABSTRACT FROM AUTHOR]

Biomass composition of switchgrass (Panicum virgatum L.) can affect its utilization by ruminants and its conversion to liquid fuels in a biorefinery. The objective of this study was to evaluate the effects of six generations of divergent breeding for forage in vitro dry matter digestibility (IVDMD) on switchgrass biomass composition, forage quality traits, and ethanol yield. Initially there was one cycle of selection for both low (C-1) and high IVDMD (C1 = cv. Trailblazer), followed by four additional breeding cycles for high IVDMD. In cycles 4 and 5, winter survival was included as a selection criterion because of decreased winter survival of the C3 population. The experimental populations that were produced by these breeding generations and nine half-sib families from cycle 5 were evaluated for two post-establishment years at the research station in eastern Nebraska, where all the breeding work was conducted. The six breeding generations resulted in significant differences among the populations for all the 28 cell wall and non-cell-wall composition variables measured, forage quality, and ethanol yield traits measured except for total biomass C, cell wall concentration, soluble glucose, and etherified ferulates. These traits included all cell wall and nonstructural carbohydrates. Breeding for the heritable complex trait IVDMD affected a large number of plant biomass characteristics and also adversely affected plant biomass yield and winter survival. [ABSTRACT FROM AUTHOR]

Pollination bags for making controlled crosses between switchgrass (Panicum virgatum L.) plants were made from a polyester micromesh fabric with a mesh size of 41 μm, which is smaller than the mean reported 43 µm diameter of switchgrass pollen. When used in paired-plant crosses between switchgrass plants, the mean amount of seed produced per plant was about 1 g, or approximately 800 seeds, which was significantly greater than the 10 to 250 seeds produced previously in paired-plant crosses of switchgrass using paper pollination bags. The four- to tenfold increase in seed produced per cross enables the progeny of the crosses to be evaluated in larger numbers in genetic studies and in replicated space-transplanted or seeded sward evaluation trials. The micromesh pollination bags cost about $15 each because of fabric costs but could be reused for 10 or more pollination seasons at an annual cost per cross of about $1.50 or less. [ABSTRACT FROM AUTHOR]

CSSA Fellows * Aamodt, O. S. * Adair, C. R. Adams, M. W. Ahlgren, H. L. * Albrecht, H. R. Alexander, D. E. Allan, R. E. Allard, R. W. Allen, [...]

CSSA Fellows * Aamodt, O. S. * Adair, C. R. Adams, M. W. Ahlgren, H. L. * Albrecht, H. R. Alexander, D. E. Allan, R. E. Allard, R. W. Allen, [...]