bluuebunny/crossref_metadata_2025 huggingface dataset:
Inoculum Rate Influences Selection for Field Resistance to Soybean Sudden Death Syndrome in the Greenhouse
Authors: Njiti V. N. , Johnson J. E. , Torto T. A. , Gray L. E. , Lightfoot D. A.
Published: July 2010

Effective selection of field resistance to soybean sudden death syndrome (SDS) caused by Fusarium solani (Mart.) Sacc. f. sp. glycines (Fsg) (Roy, 1997), measured by disease index (DX), requires multiple environments. Current greenhouse assays reduce genotype × environment interactions, but fail to predict field resistance. Our objective was to compare selection for field resistance to SDS in the greenhouse among recombinant inbred lines (RILs) inoculated with Fsg at three rates. Thirty soybean [Glycine max (L.) Merr.] RILs with characterized field resistance to SDS were evaluated in the greenhouse for scorch severity at three inoculum rates in four experiments. Ten cultivars with characterized field resistance were compared using disease severity (DS) readings from one experiment at one inoculum rate. The heritability of DS among RILs in the greenhouse was 46% at the low, 66% at the moderate, and 37% at the high inoculum rates. Reduced inoculum rates in the greenhouse (3500 to 5000 spores cm−3 plant growth medium) provided DS values that explained ≈65% of variation in the field Using a Fsg inoculum rate of 5000 spores cm−3 plant growth medium and greenhouse midparent DS as criterion for selection, the number of lines potentially resistant to SDS within a segregating population could be reduced by 53%. Errors caused ≈10% of field resistant lines to be eliminated. Among unrelated soybean cultivars, greenhouse DS values from an inoculum rate of 4000 spores cm−3 plant growth medium explained 81 and 73% of variations in field DS and DX, respectively. Therefore, the method is an effective tool for inheritance studies and cultivar evaluation for SDS.
Association of the Brazil Nut Protein Gene and Kunitz Trypsin Inhibitor Alleles with Soybean Protease Inhibitor Activity and Agronomic Traits
Authors: Streit Leon G. , Beach Larry R. , Register James C. , Jung Rudolph , Fehr Walter R.
Published: July 2010

The use of soybean [Glycine max (L.) Merr.] in animal feed without heat treatment may be possible by reducing protease inhibitors. The objectives of this study were to determine to what extent soybean protease inhibitors would be reduced genetically by combining the Brazil nut protein (BNP) gene from the transgenic line BX4P9341B6 with the ti allele for the Kunitz trypsin inhibitor from the cultivar Kunitz and their effect on agronomic traits. Soybean seed from 42 F2‐derived lines from the cross BX4P9341B6 × Kunitz were evaluated in replicated trials in 1995 for trypsin inhibitor (TI), chymotrypsin inhibitor (CI) activity, and agronomic traits. There were six lines homogeneous for presence of the BNP gene and the Ti allele (BNP+, Ti), 18 lines homogeneous for presence of the BNP gene and the ti allele (BNP+, ti), six lines homogeneous for absence of the BNP gene and presence of the Ti allele (BNP−, Ti), and 12 lines homogeneous for absence of the BNP gene and presence of the ti allele (BNP−, ti). The mean TI activity of the BNP+, ti lines was 85.1% less than for the BNP−, Ti lines representative of conventional soybean cultivars. The mean CI activity of the BNP+, ti lines was 61.4% less than the BNP−, Ti lines. The means of the four genotypic classes were not significantly different (P > 0.05) for seed yield, maturity, lodging, and protein content. It should be possible to develop high‐yielding cultivars with the BNP+, ti genotype that have major reductions in TI and CI activity.
Frost Tolerance of Ten Seedling Legume Species at Four Growth Stages
Authors: Meyer D. W. , Badaruddin M.
Published: July 2010

Spring frost in cooler regions periodically kills seedling legumes and makes replanting necessary. Experiments were conducted in the growth chamber to determine freezing tolerance of 10 legume species at four growth stages and to determine the freezing temperature that kills 50% of seedlings (LT50) for each species under temperatures more commonly found in the field. Four temperatures (−2, −4, −6, and −8°C), four seedling ages (1, 2, 3, and 4 wk after planting), and 10 legume species [alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), sweetclover (Melilotus officinalis Lam.), alsike clover (T. hybridium L.), white clover (T. repens L.), sainfoin (Onobrychis viciifolia Scop.), pinto bean (Phaseolus vulgaris L.), navy bean (Phaseolus spp.), soybean [Glycine max (L.) Merr.], and field pea (Pisum sativum L.)] were included. Hardened (vernalized) seedlings were placed in a programmable freezing chamber at 3°C and the temperature decreased or increased 1°C h−1 to or from a minimum‐freezing temperature. Pinto and navy beans were the least tolerant, soybean and field pea were moderate, and forage legumes were the most tolerant to freezing temperature. The LT50 was −3.25 to −3.5°C for dry beans, −4.5°C for soybean and field pea, and −6.3 to −7.4°C for forage legumes. One‐week‐old seedlings had the highest tolerance to freezing temperature when close to the LT50, compared with older seedlings. However, this tolerance at 1 wk of age disappeared when temperature was lower than the LT50 of the species. The prediction equation and LT50 for each species have potential for predicting seedling stand loss after a spring frost, realizing that field validation of these is impossible.
Amino Acid and Protein Changes during Cold Acclimation of Green‐Type Annual Bluegrass (Poa annua L.) Ecotypes
Authors: Dionne Julie , Castonguay Yves , Nadeau Paul , Desjardins Yves
Published: July 2010

Cold acclimation is associated with many metabolic changes that lead to increase freezing tolerance. This study was conducted to assess amino acid and protein changes occurring during cold acclimation of green‐type annual bluegrass ecotypes cold hardened under both environmentally controlled and simulated‐winter conditions in an unheated greenhouse. These biochemical changes were monitored in three ecotypes of contrasting freezing tolerance originating from Western Pennsylvania (OK), Coastal Maryland (CO), and central Québec (CR). Cold hardening induced major changes in amino acid levels in overwintering crowns of the three ecotypes and the highest contributions to total amino acid accumulation after acclimation at subfreezing temperatures came from proline, glutamine, and glutamic acid. Higher levels of amino acid and greater differences among ecotypes were observed after acclimation at subzero temperatures. Amino acid levels, including proline, were not related to the differential freezing tolerance among the three annual bluegrass ecotypes tested. Specific soluble polypeptides and thermostable proteins showed cold responsiveness and in some cases, their peak accumulation coincided with maximum freezing tolerance of annual bluegrass. In plants hardened to winter conditions in a unheated greenhouse, there was a distinct accumulation of polypeptides from fall until midwinter with a subsequent decrease in the spring.
Morphological and Physiological Characteristics Associated with Heat Tolerance in Creeping Bentgrass
Authors: Xu Qingzhang , Huang Bingru
Published: July 2010

Growth of creeping bentgrass (Agrostis palustris Huds.) is limited by heat stress during summer. Understanding the morphological and physiological characteristics associated with heat tolerance of creeping bentgrass would facilitate breeding programs in improving those characteristics. The objectives of this experiment were to study responses of single‐leaf photosynthetic capacity, tillering, and root growth to heat stress for two creeping bentgrass cultivars differing in performance under heat stress and to determine the relative importance of these factors in heat tolerance. The cultivars L‐93 (heat tolerant) and Penncross (heat sensitive) were exposed to day/night temperatures of 20/15°C (control) and 35/30°C (heat stress) in growth chambers. Canopy net photosynthetic rate (Pn), single‐leaf Pn, and RuBP carboxylase (Rubisco) activity were reduced by heat stress for both cultivars. Canopy Pn of L‐93 was significantly higher (more than double at 64 d of treatment) than that of Penncross under heat stress. Cultivars were not different in single‐leaf Pn and Rubisco activity under either control or heat stress conditions. High temperature reduced plant density, tiller density, root number, and root fresh weight for both cultivars. L‐93 had higher plant and tiller densities, greater root to tiller ratio, and more and finer roots than Penncross under control and high temperature conditions. The better performance of L‐93 under heat stress was due largely to its morphological characteristics, including tillering and root growth, but was not related to single‐leaf photosynthetic capacity. Narrow leaves, small plants, dense tillers, big root system, and high root‐to‐shoot ratio could be used to select heat tolerant cultivars.
Zoysiagrass Water Relations
Authors: White R.H. , Engelke M.C. , Anderson S.J. , Ruemmele B.A. , Marcum K.B. , Taylor G.R.
Published: July 2010

Development of drought resistant, water‐conserving cultivars continues to be an objective of turfgrass breeding programs. This study was conducted to determine for 15 zoysiagrasses [Zoysia japonica Steud., Z. matrella (L.) Merr., and Z. japonica Steud. × Z. tenuifolia Willd.] under greenhouse conditions (i) water relations characteristics, (ii) survival and recovery from extreme water stress, and (iii) the relationship of water relations characteristics to supplemental irrigation requirement determined in field studies. Leaf water potential at zero turgor (ΨL0) ranged from −1.76 MPa to −2.52 MPa before, and from −2.18 MPa to −2.59 MPa after water stress. Though ΨL0 of genotypes such as Cavalier, El Toro, and Emerald decreased after stress, ΨL0 of genotypes such as Korean Common and DALZ8515 did not change. Osmotic potential at full turgor (Ψπ100) of genotypes such as DALZ8501 and DALZ8506 was similar or increased after water stress but decreased for genotypes such as Crowne and Korean Common. The ΨL0 and Ψπ100 after stress were negatively correlated with recovery from stress and positively correlated with irrigation requirement. Zoysia genotypes with low relative water content at zero turgor (RWC0), bulk modulus of tissue elasticity (ε), and apoplastic water fraction (β) demonstrated poor recovery from stress and required more supplemental irrigation. Cultivars such as Crowne, El Toro, and Palisades had the greatest recovery from stress, the least irrigation requirement, more negative ΨL0 and Ψπ100, and positive RWC0, ε, and β. This study demonstrates that improvements in biophysical as well as morphological traits should contribute to development of water‐conserving Zoysiagrass germplasm.
Nitrogen Fertilization of Buffalograss
Authors: Springer T.L. , Taliaferro C.M.
Published: July 2010

Because native, shortgrass prairies are not typically fertilized and otherwise extensively managed, little information is available on their response to nitrogen (N) fertilization. An experiment was conducted in 1997 and 1998 to study the effects of N fertilization on forage yield and quality, forage height, and subsequent nitrate accumulation in the soil of a rangeland site consisting primarily of buffalograss [Buchloë dactyloides (Nutt.) Engelm.]. The N treatments were 0, 34, 68, 102, and 136 kg ha−1 arranged in a Latin square design. An increase (P < 0.05) in forage dry matter (DM) yield was obtained with 34 kg ha−1 N. Greater (P < 0.05) forage yields were achieved with an additional 102 kg ha−1 N (total 136 kg ha−1 N). Forage yields averaged 2540 kg ha−1 in 1997 and 2340 kg ha−1 in 1998. Nitrogen fertilization increased crude protein (CP) of buffalograss forage. Each unit of 34 kg ha−1 N linearly increased CP up to approximately122 g kg−1 of DM forage. Weather conditions influenced in vitro digestible dry matter (IVDDM). As long as moisture conditions were favorable for forage growth, IVDDM increased linearly with N fertilization rate. In 1997, IVDDM ranged from 565 g kg−1 for the control to 658 g kg−1 for the 102 kg ha−1 N application rate. In 1998, IVDDM declined linearly (P < 0.05) with N fertilization rate. In vitro digestible dry matter averaged 539 g kg−1 for the control to 482 g kg−1 for the 136 kg ha−1 N application rate. Nitrogen fertilization of buffalograss dominated semiarid rangeland can enhance forage production and quality. Nitrate accumulation in the soil was insignificant over the study period.
Summer and Autumn Growth of Rhizomatous Birdsfoot Trefoil
Authors: Kallenbach R.L. , McGraw R.L. , Beuselinck P.R. , Roberts C.A.
Published: July 2010

A new population of birdsfoot trefoil (Lotus corniculatus L.) with rhizomes (RBFT) has been developed for greater persistence. No study has compared RBFT with a standard, non‐rhizomatous cultivar of birdsfoot trefoil (BFT). Objectives were to: (i) compare RBFT with BFT for differences in shoot and root mass and total nonstructural carbohydrate (TNC) concentration of taproots in both clipped and non‐clipped situations and (ii) describe rhizome production of clipped and non‐clipped RBFT. ‘Norcen’ BFT and RBFT were grown in field plots near Columbia, MO, in 1994 and 1995. The study had four treatments: non‐clipped RBFT, clipped RBFT, non‐clipped BFT, and clipped BFT. Each treatment was replicated four times in a randomized complete block. Plots were sampled biweekly for shoot and root mass and taproot TNC from early‐July until the first killing frost in October. In addition, length, mass, TNC, and number of rhizomes per plant were recorded for RBFT. From mid‐September until the final sampling, the shoot mass for RBFT was about half that of BFT; however, RBFT's shoot mass was less affected by clipping than was BFT's. Taproot TNC was 20 to 40 g kg−1 greater for RBFT than BFT throughout both growing seasons. Nearly all RBFT plants exhibited rhizomes by mid‐October both years. Clipping RBFT plants did not affect rhizome growth. Rhizome TNC concentration increased steadily during autumn, with a final concentration of approximately 220 g kg−1 The failure of clipping to decrease rhizome production, combined with higher levels of below‐ground TNC, may give RBFT the ability to withstand frequent defoliation.
Recurrent Selection for Grain Yield in Two Spanish Maize Synthetic Populations
Authors: Vales M.I. , Malvar R.A. , Revilla P. , Ordás A.
Published: July 2010

The most common maize (Zea mays L.) heterotic pattern in Europe is European flint × U.S. dent. Northern Spain × southern Spain has been proposed as an alternative heterotic pattern. Three maize synthetic populations, namely EPS6 from northern Spain, EPS7 from southern Spain, and EPS10 formed by early American populations, were produced in Pontevedra, Spain. Because of their low yield, the two Spanish synthetic populations were subjected to three cycles of intrapopulation S1 recurrent selection for grain yield. Our objectives were to evaluate the effect of selection on grain yield and other agronomic traits, and to determine the changes in heterosis and general (GCA) and specific (SCA) combining ability brought about by selection. The three original synthetic populations, the three cycles of selection of the two Spanish synthetic populations, and the crosses among the original and the improved cycles were evaluated in two locations in northwest Spain in 1994 and 1995. Yield significantly increased with selection in both Spanish synthetic populations. The GCA improved with selection in both EPS6 and EPS7. Heterosis and SCA did not change significantly with selection. The third cycles of each Spanish synthetic would be the most appropriate maize populations to start a reciprocal recurrent selection to improve the heterotic pattern northern Spain × southern Spain.
Isolation of High Molecular Length DNA: Alfalfa, Pea, Rice, Sorghum, Soybean, and Spinach
Authors: Bennett P.V. , Hada M. , Hidema J. , Lepre A.M. , Pope L.C. , Quaite F.E. , Sullivan J.H. , Takayanagi S. , Sutherland J.C. , Sutherland B.M.
Published: July 2010

Measuring DNA damage in higher plants is important in assessing the impacts of environmental conditions, e.g., increased UV resulting from ozone depletion, and in testing the relationship of productivity to DNA damage and repair. Sunlight exposure of plants produces UV‐induced DNA damages measurable by treating DNA with damage‐specific enzymes and dispersion of DNA molecules in denaturing media. Such DNA must be enzyme‐digestible, with few single strand breaks. DNA isolation must preclude repair, providing a “snapshot” of DNA damage. We developed a method for isolating DNA from several crop plants, both monocots and dicots—alfalfa (Medicago sativa L.), pea (Pisum sativum L.), rice (Oryza sativa L.), soybean [Glycine max (L.) Merr.], sorghum [Sorghum bicolor (L.) Moench], and spinach (Spinacia oleraceae L.). This method is simple, readily deals with multiple samples, and avoids organic solvents. We show that pyrimidine dimers can readily be quantified in DNA prepared by this method. This method should also be useful for other experiments requiring high molecular length, enzymatically digestible plant DNA.
Evaluation of a High Grain Protein QTL from Triticum turgidum L. var. dicoccoides in an Adapted Durum Wheat Background
Authors: Chee P.W. , Elias E.M. , Anderson J.A. , Kianian S.F.
Published: July 2010

Grain protein concentration (GPC) is an important component of durum wheat (Triticum turgidum L. var. durum) quality. The ‘Langdon’‐Triticum turgidum L. var. dicoccoides chromosome 6B substitution line [LDN(DIC‐6B)] contains the high GPC quantitative trait locus “QGpc.ndsu.6Bb” We evaluated the effect of this quantitative trait locus on GPC, grain yield, and other agronomic traits in an adapted durum wheat background, verified its location on chromosome 6B and determined its relationship to the GPC locus previously identified. A recombinant inbred population consisting of 110 lines segregating for high GPC was developed from the LDN(DIC‐6B) with two doses of adapted germplasm. This population was evaluated in the field for GPC at two locations in 1995, and for GPC, grain yield, and other agronomic characteristics at three locations in 1996. Segregation analysis for GPC showed a bimodal distribution, indicating a single genetic factor or a tightly linked gene cluster controlling high GPC. This high GPC locus was insensitive to environmental conditions. Grain protein concentration was not correlated with plant height, but was loosely correlated with grain yield and heading date. Quantitative trait locus analysis using simple regression and interval mapping procedures identified a locus flanked by Xcdo365 and Xmwg79 on chromosome 6B as having a major effect on GPC. This high GPC locus, which explained up to 72% of the phenotypic variance, accounted for a 15 g kg−1 increase in average GPC. Selection for the two markers flanking the GPC QTL would be highly effective in introgressing this QTL into durum wheat breeding programs.
Direct and Correlated Responses to Divergent Selection for Leaf Abscisic Acid Concentration in Two Maize Populations
Authors: Landi P. , Sanguineti M.C. , Conti S. , Tuberosa R.
Published: July 2010

Abscisic acid (ABA) concentration can affect plant responses to drought and has been suggested as a selection criterion to improve drought tolerance. Divergent selection for high (H) and low (L) leaf ABA concentration was conducted under moderate drought conditions in the F2 of maize (Zea mays L.) single crosses Os420 × IABO78 and Mo17 × B88. Objectives of this study were to evaluate direct and correlated responses to the divergent selection. For each cross, the F2 and the H‐ and L‐populations (H‐P and L‐P) were compared. For Os420 × IABO78, the comparison was made in one location, for 2 yr, and at three irrigation volumes (corresponding to 0, 60, and 120% of crop evapotranspiration). At all irrigation volumes, H‐P exceeded L‐P for leaf ABA concentration, drought sensitivity, leaf temperature, silk delay, and lodging resistance, while it showed lower plant height and grain yield (on average, 3.61 vs. 5.14 Mg ha−1). The F2 was intermediate for most traits. Significant differences were not detected for water status traits. For Mo17 × B88, populations were compared at one irrigation volume (60% of evapotranspiration) in three environments. In all environments, H‐P was superior to L‐P for leaf ABA concentration and drought sensitivity, and it was shorter, and less productive (on average, 4.71 vs. 6.95 Mg ha−1). The F2 was intermediate for leaf ABA concentration but not for grain yield. Results indicate that selection for low leaf ABA concentration led to populations with better agronomic performance than did selection for high leaf ABA concentration.
Reduced Lodging for Soybean in Low Plant Population is Related to Light Quality
Authors: Board Jim
Published: July 2010

Lodging is a common production problem for soybean [Glycine max (L.) Merr.] in the southeastern USA. Reducing plant height by planting at a low optimal population (plant population sufficient to optimize yield) is a recognized practice for reducing lodging. Environmental factors responsible for reduced plant height in response to low optimal population have not been determined, however. Plant height for determinate soybean is determined mainly during the vegetative period (emergence to R1). Because light quality affects stem extension, our objective was to determine the roles of red/far red light ratios and blue light irradiance during the vegetative period on plant height. Determinate cultivar Deltapine 3606 (Maturity Group VI) was planted at an optimal planting date during 1995 and 1996 at low (80 000 plants ha−1), medium (145 000 plants ha−1), and high (390000 plants ha−1) plant populations on a Commerce silt loam soil (fine‐silty, mixed, nonacid, thermic, Aeric, Fluvaquents) near Baton Rouge, LA (30°N Lat). Experimental design was a randomized complete block in a split plot arrangement with four replications. Plant populations were main plots and split plots were staked (non lodging) and unstaked (prone to lodging) treatments. Increased lodging in staked vs. unstaked plots resulted in a 10% yield loss. Across unstaked plots, decreased lodging in low vs. high population was associated with a 25% reduction in plant height and a 29% increase in main stem thickness. These morphological changes were more closely related to differences in red/far red light ratios for low vs. higher plant populations rather than to changes in blue light irradiance.
Genetic Improvement in Short Season Soybeans: I. Dry Matter Accumulation, Partitioning, and Leaf Area Duration
Authors: Kumudini Saratha , Hume David J. , Chu Godfrey
Published: July 2010

Genetic improvement of short‐season soybean [Glycine max (L.) Merr.] cultivars has resulted in a 0.5% annual gain in yield. Although yield is the product of dry matter (DM) accumulation and partitioning, the relative contributions of these two components of yield to genetic improvement has not been documented. Furthermore, the mechanism by which higher DM accumulation or harvest index (HI) is accomplished in the newer cultivars is unclear. The objective of the current study was to characterize DM accumulation and partitioning in cultivars which differ in yield potential, and determine the role of these traits in yield improvement. Two older (low yield potential) and two newer (higher yield potential) soybean cultivars of similar maturity were grown in side‐by‐side trials in 1996 and 1997. Plant samples were taken during each growing season and separated into leaves, stems + petioles, roots, and seeds. Dry matter accumulation and leaf area indices were measured. Seed yield of the new cultivars was 30% greater than their older counterparts. Increased DM accumulation contributed 78% and increased HI contributed 22% towards the genetic gain in yield. Total plant dry weight increased to a maximum around R4/R5 and subsequently declined during the seed‐filling period (SFP) as pod development increased and leaf senescence began. This decline in dry weight during the SFP was greater for the old than for the new cultivars. The newer cultivars maintained leaf area further into the SFP than the old cultivars enabling continued dry matter accumulation. The results of this experiment indicate that genetic yield improvement in the short‐season soybean cultivars examined was mainly associated with longer leaf area duration and the subsequently greater DM accumulation.
Control of Interplot Interference in Grain Maize: A Multi‐Site Comparison
Authors: David Olivier , Monod Hervé , Lorgeou Josiane , Philippeau Gérard
Published: July 2010

Interplot interference is known to be potentially a major source of bias in cultivar trials of several plant species, but there are few published results concerning grain maize (Zea mays L.) in France. Two series of field experiments were conducted in the North and in the South of France from 1994 to 1996 to quantify interference in grain maize trials and compare methods of control. Each experiment typically consisted of a reference trial with two or three unharvested rows on each side of each plot, a four‐row‐plot trial with one unharvested row on each side of each plot, and a two‐row‐plot trial. Trials had seven cultivars in 1994 and 1996, and four additional cultivars in 1995. Interference was found to occur in two‐row‐plot trials and to be related to plant height. When a cultivar was 10 cm shorter than each of its neighbors, its yield was reduced by 0.16 Mg ha−1 in the North series and by 0.30 Mg ha−1 in the South series on average. Interference appeared much lower in the four‐row‐plot trials. Methods for controlling interference were assessed by comparing their cultivar estimates with those from the reference trials. Bias due to interference in the two‐row‐plot trials was reduced by using models for interference, but the four‐row‐plot trials appeared as a more reliable method to avoid such bias.
Soybean Light Interception and Yield Response to Row Spacing and Biomass Removal
Authors: Singer Jeremy W.
Published: July 2010

Biomass removal effects on soybean [Glycine max (L.) Merr.] light interception and yield under different row spacings have not been documented. Objectives for this study were to evaluate biomass removal, light interception, seed yield, and yield components of soybean under seven clipping treatments. Treatments in this study were clipping at V5, R1, R4, V5 + R1, V5 + R4, R1 + R4, and V5 + R1 + R4, and a control in 18‐ or 20‐cm and 76‐cm rows. In 1998, a dry year, biomass removal exhibited a negative linear relationship with seed yield in narrow rows (r2 = 0.62). A row spacing–clipping interaction was observed. In wide rows, clipping at V5 or R1 produced a compensatory response by increasing yield 12 and 5%, respectively. Generally, soybean in 76‐cm rows maintained seed yield by adjusting the number of pods or seed weight, except when clipping occurred at V5 + R4 or at three growth stages. In 1999, under severe moisture stress, row spacing influenced seed yield. Averaged across clipping treatments, narrow rows yielded 16% more (301 vs. 254 g m−2) than wide rows. Generally, soybean yield declined as clipping timing was delayed and as clipping frequency increased in narrow rows, except when clipping occurred at V5 + R1. Clipping at V5 and V5 + R1 did not affect yield in wide rows. All other clipping treatments suffered yield reductions ranging from 20 to 58%. A quadratic relationship (R2 = 0.83) was observed between biomass removal and seed yield.
Selection of Soybean Mutants with Increased Concentrations of Seed Methionine and Cysteine
Authors: Imsande John
Published: July 2010

Soybean [Glycine max (L.) Merr.] protein, which is deficient in the sulfur amino acids, especially methionine, is consumed world‐wide by both humans and other animals. Methionine deficiency is caused by an abundance of the β‐chain of β‐conglycinin, a seed storage protein that lacks methionine. De novo synthesis of the β‐chain is inhibited by an elevated concentration of methionine. The objectives of our investigations were to mutagenize soybean seeds, characterize a methionine over‐producing phenotype, and select several methionine over‐producing genetic lines. Mutant lines with a methionine over‐producing phenotype were isolated and crossed. Seeds from a cross, designated H82 × 20a2, contained a normal seed nitrogen concentration and an 18% increase in seed sulfur concentration. The S/N atomic ratio of line H82 × 20a2 was 16.2% greater than that of the parental line. Amino acid analyses of seeds from the derived and parental lines revealed mole percentages of 1.84 and 1.51, respectively, for methionine and 1.685 and 1.32, respectively, for cysteine. Thus, seed methionine and cysteine concentrations of H82 × 20a2 were each approximately 20% greater than those of the parental line. Protein produced by the derived line may fulfill nutritional requirements for methionine and cysteine.
Incidence and Diversity of Neotyphodium Fungal Endophytes in Tall Fescue from Morocco, Tunisia, and Sardinia
Authors: Clement S.L. , Elberson L.R. , Youssef N.N. , Davitt C.M. , Doss R.P.
Published: July 2010

There is a premium on having Neotyphodium germplasm available for temperate grass improvement programs because these fungal endophytes present opportunities for developing new grass–endophyte combinations for enhanced tolerance to abiotic and biotic stresses. Unfortunately, surveys have revealed a low incidence of Neotyphodium fungi in grass germplasm collections. This research surveyed tall fescue (Festuca arundinacea Schreb.) accessions from a 1994 Australian–U.S. plant‐collection trip to Morocco, Tunisia, and Italy (Sardinia) for viable Neotyphodium fungi and determined whether infected accessions harbor different Neotyphodium genotypes. Conidial measurements of isolates cultured on agar and bioassays of the differential survival of bird cherry‐oat aphid [Rhopalosiphum padi (L.)] on infected accessions were used to characterize Neotyphodium diversity. A secondary objective determined the consistency of a polymerase chain reaction (PCR) method to detect Neotyphodium fungi in tall fescue. Neotyphodium was detected in 336 of 439 plants (76.5%) distributed among 104 accessions, of which 99 were endophyte‐infected. Mean conidial lengths of 42 isolates ranged from 3.91 to 9.91 μm. Most of the isolates (71.4%) had conidia with mean lengths smaller than the lower limit (6.5 μm) characteristic of the tall fescue endophyte N. coenophialum (Morgan‐Jones and Gams) Glenn, Bacon, and Hanlin. In aphid assays, all endophyte‐free plants were susceptible to R. padi and all but two infected plants were resistant to this aphid. Thus, a Mediterranean plant‐collection trip secured diverse Neotyphodium endophytes in tall fescue for storage in seed banks, and a PCR assay detected Neotyphodium in tall fescue plants of diverse geographical origin.
Karyotype and C‐Banding Patterns of Mitotic Chromosomes in Diploid Bromegrass (Bromus riparius Rehm)
Authors: Tuna Metin , Gill Kulvinder S. , Vogel Kenneth P.
Published: July 2010

Previous cytogenetic studies of the genus Bromus L. were limited to chromosome counts and construction of karyotypes on the basis of Feulgen staining. Since the chromosomes of Bromus are similar in morphology, these karyotypes are of limited use for chromosome identification and genome analysis. The objectives of this study were to develop and evaluate a Giemsa C‐banding procedure to use in identification of individual bromegrass chromosomes and to develop a karyotype for diploid Bromus riparius Rehm. (2n = 14; PI 440215). All chromosomes had one or more C‐bands which were located mainly at telomeric regions. A group (I) of four pairs of chromosomes had telomeric bands on only one arm and could be differentiated. In this group, one pair had an interstitial C‐band along with a telomeric band, one pair had a nucleolus organizer region (NOR) at a subtelomeric location on the short arm, and the other two pair could be distinguished by centromere location. The other group (II) of three pairs of chromosomes had telomeric bands on both arms. The unequivocal identification of specific chromosomes of Group II was not possible in all cells because of their similarity and differential condensation of chromosomes. Chromosomes of both groups were either metacentric or submetacentric. The total length of individual chromosomes ranged from 5.58 to 6.87 μm and the arm ratios ranged from 1.02 to 1.5. The homologous chromosomes were paired and assigned numbers I to VII in decreasing length. A karyotype was constructed by means of the C‐bands, mean chromosome lengths, and arm ratios. The C‐banding procedure used in this study could be used to developed karyotypes for the other species of the genus Bromus and these C‐banded karyotypes could be used to compare genomes within the genus.
A Core Collection for Saccharum spontaneum L. from the World Collection of Sugarcane
Authors: Tai P.Y.P. , Miller J.D.
Published: July 2010

Vegetative maintenance of the large number of Saccharum spontaneum clones in the World Collection is extremely laborious and expensive. A core subset, chosen to represent the range of diversity of the World Collection, can enhance preservation research and exploit the potential value for breeding. A total of 342 accessions of S. spontaneum from the World Collection at the USDA‐ARS National Germplasm Repository in Miami, FL, were used to evaluate various sampling strategies for choosing a core collection of this species and to designate a core collection of 75 clones using geographic origin and characterization data. Eleven sampling methods with 11 quantitative traits were used to designate the 75 clones in the core collection. The efficiency of sampling was increased by stratification by geographical grouping of accessions before a stratified random sampling procedure was carried out. Cluster analysis was used within each geographic region based on retained principal components with morphological variables, followed by random selection of entries within each cluster for designating the core collection. In addition to the efficient use of S. spontaneum, this core collection should prevent the loss of significant components of the World Collection, ensure better use of limited resources, and enhance conservation research.
Influence of Vernalization and Photoperiod Responses on Cold Hardiness in Winter Cereals
Authors: Mahfoozi S. , Limin A. E. , Fowler D. B.
Published: July 2010

An understanding of the genetic regulation of low‐temperature (LT) tolerance is a prerequisite for the development of cold tolerant cultivars for high stress regions. Vernalization requirement in winter habit cereals and photoperiod responsiveness in spring habit cereals has been shown to influence expression of the LT tolerance genes. The objective of the present study was to determine the influence of photoperiod response on expression of LT tolerance genes in vernalization requiring winter habit cultivars Norstar and Warrior wheat (Triticum aestivum L. em. Thell) and Kold barley (Hordeum vulgare L.). These cultivars were subjected to 8‐h‐short day (SD) and 20‐h‐long day (LD) photoperiods at cold acclimating temperature (4°C) over a period of 0 to 98 d. Final leaf number (FLN) was determined at intervals throughout the acclimation period to measure vernalization status. Photoperiod sensitivity did not affect vernalization as both SD and LD plants reached vernalization saturation at the same time. However, a significant increase in leaf number and delayed double ridge formation between 49 and 98 d under 4°C SD non‐inductive flowering condition relative to the LD treatments indicated that SD delayed phenological development. Low‐temperature tolerance gene expression as measured by LT50 was influenced before the signal for floral transition as indicated by FLN measurements. Photoperiodic response of SD sensitive winter barley and wheat cultivars was reflected in the level of expression of LT tolerance beginning in the early stages of vernalization and plant development. Subsequent LT acclimation continued for a longer time and to colder temperatures under SD compared to LD. These results support the hypothesis that vernalization and photoperiod responses regulate the expression of LT tolerance genes through their influence on the rate of plant development.
Heterotic Relationships among Nine Temperate and Subtropical Maize Populations
Authors: Mickelson Harold R. , Cordova Hugo , Pixley Kevin V. , Bjarnason Magnie S.
Published: July 2010

The introgression of exotic germplasm could increase the heterosis among maize (Zea mays L.) populations. Our objective was to assess heterotic relationships among BSSS (R) (‘Reid’ germplasm) and BS 26 (‘Lancaster’ germplasm) from the temperate USA; the southern African cultivars Salisbury White, Southern Cross, and Natal Potchefstroom Pearl Elite Selection (NPP ES); and the subtropical CIMMYT Populations 34, 42, 44, and 47. The nine cultivars and their diallel crosses were evaluated at five Mexico, Zimbabwe, and U.S. locations. Populations 34, 42, 44, and 47 and NPP ES demonstrated the highest per se grain yield with Population 44 ranking first (8.42 Mg ha−1). Low to moderate levels of high parent heterosis was observed for their crosses; nonetheless, they occurred frequently as parents of superior crosses at Mexico where Population 42 × Population 47 ranked first (8.42 Mg ha−1). BSSS (R) demonstrated the best general combining ability with variety heterosis effects averaging 1.34 Mg ha−1 Diversity among varieties was determined on the basis of “dominance‐associated” gene effects. When the diversity was resolved by principle coordinate analysis, BSSS (R) was separated from BS 26, and Salisbury White from Southern Cross along different dimensional axes, suggesting that the two pairs are sources of different genes for heterosis. The highest yielding cross (9.28 Mg ha−1) and best heterotic combination involved Population 44 and BSSS (R). BSSS (R), NPP ES, and Populations 44 and 42 performed well outside their target ecologic zones, indicating their potential benefit to breeding programs in new geographic areas.
Genetic Analysis of a Hulless × Covered Cross of Barley Using Doubled‐Haploid Lines
Authors: Choo Thin‐Meiw , Ho Keh Ming , Martin Richard A.
Published: July 2010

The effects of the hulless (nud) and rough‐awned (Raw1) genes are not fully understood in hulless barley (Hordeum vulgare L.). A study was initiated to (i) determine the potential of hulless lines in a hulless × covered cross, (ii) detect additive × additive epistasis and estimate genetic correlations, and (iii) determine the effects of hulless and rough‐awned genes on 11 agronomic traits of barley. Fifty covered lines and 48 hulless lines derived from a ‘Kunlun no. 1’ × ‘CIMMYT no. 6’ cross were evaluated for grain yield, test weight, seed weight, height, heading date, and maturity at two locations in Eastern Canada (Charlottetown and Ottawa) in 1998. Plant density, smut resistance, and scald resistance were also recorded at Charlottetown, while spike density was estimated at Ottawa. The 48 hulless lines contained 82 to 100% hulless kernels. At least one hulless line yielded similar to the highest yielding line if it was adjusted by the weight loss of the hull. This suggests that it is possible to breed for high‐yielding hulless barley cultivars. Additive × additive epistasis was detected for some of the traits. Yield was significantly correlated with test weight, seed weight, and height. In Eastern Canada, hullessness was associated with 17% lower plant density, 11 to 18% shorter plant height, 15 to 19% lower seed weight, 20 to 21% higher test weight, and 21 to 36% yield reduction. Hullessness, however, was not associated with heading date, maturity, smut resistance, scald resistance, and spike density. Since hulless progeny could have lower emergence rates and shorter plant heights, hulless barley breeding programs should avoid propagating segregating materials from hulless × covered crosses in bulk populations, as many hulless plants may be eliminated by competition. Rough‐awned hulless barley had more hulless kernels than smooth‐awned. Therefore, selection for rough‐awned plants could improve the threshability of hulless barley.
Recurrent Selection for Seedling Vigor in Kura Clover
Authors: DeHaan L. R. , Ehlke N. J. , Sheaffer C. C.
Published: July 2010

Kura clover (Trifolium ambiguum M. Bieb.) is a rhizomatous perennial forage legume that has outstanding persistence once established. Low seedling vigor presents a challenge to kura clover establishment. Kura clover seedlings partition a significant portion of their dry matter to below ground growth. Therefore, seedling vigor could be improved by increasing dry matter allocation to the shoot. Our objective was to study the potential of recurrent phenotypic selection in the greenhouse for reduced root/shoot ratio to increase seedling vigor. Three cycles of divergent selection for root/shoot ratio and a control selection for large plant biomass (LP) were performed from a parent population consisting of ‘Rhizo’, ARS‐2678, KZ1, and Erect Spreader populations. Selections for low root/shoot ratio (LoRS) and high root/shoot ratio (HiRS) were performed by independent culling after first selecting for large total biomass. Parent and selected populations were evaluated in the greenhouse and field. Three cycles of selection for LoRS and LP increased shoot yield in the field 42 d after planting (DAP) by 35 and 34%, respectively. Three cycles of selection for LoRS reduced root/shoot ratio in the field by 16%. Selection for HiRS did not affect seedling size in the field. Population mean shoot and total plant weights were correlated between greenhouse and field environments (average r = 0.89). Population mean seed weight was correlated with shoot weight in the field (r = 0.68, P < 0.05). The results indicate that phenotypic greenhouse selection for seedling size is an effective means of increasing seedling vigor in kura clover.
An Isozyme Marker for Resistance to Root‐Knot Nematode in Sugarbeet
Authors: Yu M. H. , Pakish L. M. , Zhou H.
Published: July 2010

Root‐knot nematode (Meloidogyne spp.) is a destructive pest of sugarbeet (Beta vulgaris L.) that reduces production in infested areas and is difficult to manage. Identification of nematode‐resistant plants is a time‐consuming process that is subject to genotype–environment interaction. Development of resistant cultivars/hybrids is the most effective control. This study was conducted to establish a rapid and effective screening technique to detect a large number of sugarbeet genotypes with resistance to Meloidogyne spp. A nematode‐resistant sugarbeet germplasm line, Mi‐1 Beta, was previously developed using J2 inoculation and screening procedures. Leaf and cotyledon extractions were used in diagnosis. Phosphoglucomutase (PGM) was found to be a potentially useful isozyme marker of resistance in Mi‐1 Beta and derived lines in starch gel electrophoresis. Seven banding patterns (four resistant and three susceptible) were produced. All susceptible plants shared the banding pattern of the resistant strains, except for a single PGM band. If demonstrated to be tightly linked to nematode resistance, this novel PGM isozyme marker will accelerate breeding sugarbeet with resistance to root‐knot nematode.
Solvent Retention Capacities of Irrigated Soft White Spring Wheat Flours
Authors: Guttieri Mary J. , Bowen David , Gannon Diane , O'Brien Katherine , Souza Edward
Published: July 2010

The solvent retention capacity (SRC) test uses the ability of flour to retain a range of solvents as a means of evaluating multiple aspects of wheat (Triticum aestivum L.) quality: pentosan content, starch damage, gluten strength, and general water retention. To assess the utility of the SRC in cultivar evaluation, 26 soft white spring wheat genotypes were produced in seven irrigated environments, and milling and baking quality parameters for these genotypes were determined. Solvent (water, 500 g kg−1 sucrose, 50 g kg−1 sodium carbonate, and 50 g kg−1 lactic acid) retention capacities of flours effectively differentiated genotypes across environments. Flour protein concentration and sucrose SRC together effectively modeled sugar snap cookie diameter. Flour extraction and sodium carbonate SRC were negatively correlated. Whole grain measurements, including near‐infrared hardness, single kernel hardness, and sodium dodecyl sulfate (SDS) sedimentation volume were correlated with SRC values. The SRC test is a promising method for evaluating soft wheat genotypes on the basis of their underlying biochemical flour characteristics, independent of flour protein concentration.
High Temperatures during Endosperm Cell Division in Maize: A Genotypic Comparison under In Vitro and Field Conditions
Authors: Commuri P. D. , Jones R. J.
Published: July 2010

High temperature during endosperm cell division reduces grain yield of maize (Zea mays L.). The objective of the study was to determine if there were differences in tolerance of two inbred lines (B73 and Mo17) to exposure to brief high temperature treatments (HTTs). Beginning 5 d after pollination (DAP), kernels were exposed to a continuous 35°C temperature for either 4 or 6 d. The effects of HTTs on kernel development, ultrastructure, and sink capacity were evaluated under both in vitro and field conditions. In B73, the 4 and 6 d HTT reduced final kernel dry weights >40 to 60% under in vitro and 79 to 95% under field conditions, compared with the controls. The HTT‐induced reduction in kernel mass was due mainly to reduction in starch granule number, since by 16 DAP the endosperm cell number had recovered and was not significantly different from the controls. In contrast, in Mo17 both the number of endosperm cells and starch granules were reduced by >45 to 80% by the 4 and 6 d HTT imposed under the two growing conditions. Hence, these data and kernel ultrastructure evidence confirm that kernel development is more tolerant to high temperature in B73 than in Mo17. The difference appears to be due mainly to the ability of B73 to maintain a higher kernel sink capacity after exposure to HTT during endosperm cell division. Exploiting the differential response of these genotypes appears to be a viable approach to further elucidate the physiological basis for heat tolerance during early kernel development.
Quantification of Root Chicoric Acid in Purple Coneflower by Near Infrared Reflectance Spectroscopy
Authors: Gray D. E. , Roberts C. A. , Rottinghaus G. E. , Garrett H. E. , Pallardy S. G.
Published: July 2010

Purple coneflower [Echinacea purpurea (L.) Moench] is an increasingly popular crop because of its value in the U.S. botanical industry. At present, there is no rapid method of analyzing it for chicoric acid, the predominant phenolic acid associated with immunostimulation in humans. The objective of this study was to quantify chicoric acid in purple coneflower roots by near infrared (NIR) reflectance spectroscopy. One hundred sixty‐nine plants were harvested and their root tissues analyzed for chicoric acid by high performance liquid chromatography (HPLC). Root samples were scanned between 1100 and 2498 nm and reflectance data recorded. The HPLC data were regressed against infrared spectra to develop empirical prediction equations. The optimum prediction equation produced coefficients of determination for calibration and cross validation of 0.90 and 0.86, respectively. The mean chicoric acid concentration was 8.29 g kg DM−1, and the standard errors of calibration and cross validation were 0.89 and 1.06 g kg DM−1, respectively. We conclude that NIR reflectance spectroscopy can accurately quantitate chicoric acid in purple coneflower.