bluuebunny/crossref_metadata_2025 huggingface dataset:
Infection of Somatic Embroys of Tall Fescue with Acremonium coenophialum
Authors: Kearney J. F. , Parrott W. A. , Hill N. S.
Published: July 2010

The availability of a tall fescue (Festuca arundinacea Schreb.) clone whose members are infected with different strains of its endophytic fungus, Acremonium coenophialum Morgan‐Jones & Gams, would help identify the individual contributions of the endophyte and tall fescue toward traits normally associated with endophyte‐infected tall fescue plants. As embryos and very young seedlings are the only stages of the life cycle during which infection by the endophyte naturally occurs in planta, attempts were made to duplicate this phenomenon in vitro. Callus cultures of tall fescue were induced using leaf basal tissue as the explant source, and Murashige and Skoog (MS) basal medium supplemented with the synthetic auxins 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], 2,4,5‐T [(2,4,5‐trichlorophenoxy)acetic acid], or picloram (4‐amino‐3,5,6‐trichloropicolinic acid). Two tall fescue genotypes were exposed to four concentrations (15, 30, 45, or 60 μM) of each auxin. Calli were transferred to hormone‐free basal medium to permit the development of somatic embryos. Elongating shoots were counted to deter mine the effectiveness of each treatment and transferred to fresh medium to permit their development into plants. The most effective and consistent auxin concentration to stimulate somatic embryogenesis was 2,4‐D at 30 μM, producing almost 14 embryos per callus. Next, 60 explants of one fescue genotype were placed on MS medium supplemented with 30 μM 2,4‐D. Two isolates of the endophytic fungus were used to infect the explants and developing call! by inoculating at weekly intervals. The highest infection rate was obtained by inoculating somatic embryos with the fungus at the time the callus was transferred to hormone‐free medium, the stage at which somatic embryos begin to elongate and germinate. This stage corresponds with the stage at which infection is thought to occur in planta. This method will permit further studies of the interactions between tall fescue and its endophyte.
Genetic Trait Effects on Nonlint Trash of Cotton
Authors: Novick Ricardo G. , Jones J. E. , Anthony W. S. , Aguillard W. , Dickson J. I.
Published: July 2010

Genetic traits that reduce seed‐cotton (Gossypium hirsutum L.) trash or improve cleanability should improve lint grade and preserve fiber quality. Onr objective was to evaluate morphological traits that reduce trash and improve cleanability and grade. Twelve near‐isolines involving four leaf shapes (normal, semi‐okra, okra, and superokra) in two genetic backgrounds (LA 213‐613 and MD 65‐11), bract types (normal and frego), and two leaf‐pubescence levels (hairy and semi smooth) were grown for 2 yr at three locations in Louisiana. Seed‐cottun was harvested with a spindle‐picker and ginned on a miniature version of a commercial gin. Amount and type of trash was determined before and after (feeder apron) seed‐cotton cleaning, and after zero, one, and two saw‐type lint cleaners. Semi smooth and super‐okra leaf traits reduced motes by 25 and 15% and small‐leaf trash at the feeder apron by 47 and 20%, respectively, compared with the check. They produced grades similar to the check with one less lint dcaner. Frego‐bract isolines had less leaf and bract trash in lint than the normal‐bract check at any level of lint cleaning. Use of genetic traits such as semi smooth and super‐okra, and to a lesser extent sub‐okra and frego bract, can be used to reduce lint trash and improve cotton grade. Reductions in motes could help reduce the seed‐coat fragment‐white spot (dead fiber) problem in fabric dying.
Barley Yellow Dwarf Virus Effects on Fructan and Sugar Concentration in Winter Oat Crowns
Authors: Livingston D. P. , Gildow F. E.
Published: July 2010

Barley yellow dwarf virus (BYDV) significantly alters carbohydrate metabolism in cereal leaf tissue. If carbohydrate accumulation in overwintering storage organs (crowns) is affected by the virus, winter survival and subsequent regrowth in spring could also be affected. To determine if BYDV alters carbohydrate accumulation patterns in winter oat (Avena sativa L.) crowns, l‐wk‐old seedlings of two cultivars were infected with the PAV isolate of BYDV. After a 3‐wk hardening period at 2 °C, carbohydrates were extracted with ethanol/water and analyzed by high‐pressure liquid chromatography. No significant differences were observed in BYDV content of leaf tissue between the two oat cultivars based on enzyme immunoassay data. Infected plants had significantly (P < 0.05) less total carbohydrate in crowns. Fructan (except that with a degree of polymerization of 3) comprised a significantly lower (P < 0.01) percentage of total carbohydrate in infected plants, while the percentage of sucrose, glucose, and fructose was significantly (P < 0.01) higher in infected plants. Results suggest that BYDV infection may alter fructan metabolism, possibly by reducing substrate levels and/or by altering enzyme activity.
Reaction of a Group of Related Wheat Species (AABB Genome and an AABBDD) to Stem Rust
Authors: McVey D. V.
Published: July 2010

Accessions of spring habit Triticum spp. with genomes AABB and T. sphaerococcum Percival (genomes AABBDD) were surveyed characterize their reaction to stem rust (Puccinia graminis Pets.: Pers. f. sp. tritici Eriks. & Henn.). Because of the dearth of information in the literature on the reaction of these species to stem rust, the objectives of this study were to screen the accessions for possible new sources of resistance to stem rust, and to postulate the identity of known genes and the minimum number of unknown genes for resistance to stem rust among accessions of each species. Infection‐type data from seedlings of 164 introductions of the USDA National Small Grains Collection artificially infected with 35 isolates of P. graminis tritici were categorized as either low or high infection type. A boxing program based on the gene‐for‐gene concept was used to identify corresponding resistance/avirulence gene pairs. In the combined AABB genomic groups, only 2 of a possible 28 known Sr genes, Sr9f and SrMCN, were among the 35 distinct Sr genes postulated. The other 33 Sr genes were associated with reaction patterns not previously identified. Six accessions were resistant to all isolates and several accessions were resistant to the present prevalent races of the stem rust pathogen in North America. Based on the accessions evaluated, T. sphaerococcum is a poor source of Sr genes for resistance to stem rust.
Maize Kernel Set at Low Water Potential: I. Sensitivity to Reduced Assimilates during Early Kernel Growth
Authors: Schussler J. R. , Westgate M. E.
Published: July 2010

Plant water deficits during flowering and early kernel growth reduce the yield potential of maize (Zea mays L.) by decreasing kernel number per ear. Our objective was to determine if zygotic abortion, which increases in water‐deficient plants, is caused by a decrease in assimilate supply to the ear. Plants were grown in soil/sand media in a controlled environment. Beginning at silk emergence and continuing for 3 wk after pollination, leaf photosynthesis was inhibited ≈50% (moderate) or 100% (severe) by withholding water (water‐deficit treatment) or decreasing light intensity (low‐light treatment). Silk water potential (ψw) at pollination was about −0.7 and −1.1 MPa in the moderate and severe water‐deficit treatments, compared to about −0.4 MPa in well‐watered plants. Mean kernel number per ear was 581 in control plants and was decreased 48 and 99% by the moderate and severe water‐deficit treatments, respectively. In the corresponding low‐light treatments, kernel number was decreased 40 and 100%. Thus, losses in kernel number pe ear reflected the relative inhibition of photosynthesis during early kernel growth, regardless of plant water status. Compared to controls, the water‐deficit and low‐light treatments decreased partitioning of dry matter, carbohydrates, and reduced N to the kernels. However, carbohydrates continued to accumulate immediately after pollination in the stalk and leaf tissue. This suggests that some stalk and leaf reserves were unavailable to support early kernel growth at low ψw. Collectively, these data indicate that early kernel development is highly dependent on a continued supply of carbohydrates from concurrent photosynthesis. Water deficits increase the probability of developmental failure by limiting this supply.
Stem Infusion of Liquid Culture Medium Prevents Reproductive Failure of Maize at Low Water Potential
Authors: Boyle Mark G. , Boyer John S. , Morgan Page W.
Published: July 2010

Maize (Zea mays L.) plants exposed to low water potentials (ψw) at anthesis frequently experience failure of reproduction despite high plant ψw before and after anthesis. Since the supply of reserve carbohydrates in maize stems may be low at anthesis and low ψw can inhibit photosynthesis, it is possible that a water deficit at anthesis causes a deficit of photosynthetic products or their derivatives, which could lead to premature cessation of reproductive development. To test this hypothesis, a high‐sucrose (150 g L−1 liquid tissue culture medium was supplied to the stems of dehydrating maize plants from an external reservoir using a new stem infusion technique. Plants were grown in controlled environment chambers in large pots containing soil. At midday, the rates of net photosynthesis of upper leaves of well‐watered plants were ≈20 μmol m−2 s−1 and the ψw of these leaves was −0.6 MPa. Approximately 5 d after water was withheld from pots, upper leaf ψw dropped to −1.6 to −1.8 MPa and photosynthetic rates of the same leaves were ≈20 μmol m−2 s−1. Stem infusion of liquid tissue culture medium during 5‐ or 7.5‐d water‐deficit periods initiated 1 d after silking prevented reproductive failure without rehydrating the plant. Final grain yields of some of the medium‐infused plants approached control yields. Dehydrated plants which received infusion of a similar volume of water or which were not infused experienced nearly complete reproductive failure. Following rehydration, photosynthesis of all plants exposed to low ψw during anthesis recovered, but only those infused with the medium during low ψw continued kernel development to maturity. Additional experiments indicated that plant growth regulators were not required for an effective medium. These experiments identify assimilate supply and not low plant ψw per se as a limiting factor in maize reproductive failure near anthesis and suggest that improvement in drought tolerance may be achieved by changes in the assimilate storage patterns and/or the phenology of maize plants. Additionally, this whole plant system provides an agriculturally relevant model system for studying the cellular and subcellular mechanisms associated with failure of reproductive growth at low ψw.
Productivity and Consumption of Wheatgrasses and Wheatgrass‐Sainfoin Mixtures Grazed by Sheep
Authors: Griggs T. C. , Matches A. G.
Published: July 2010

Grazing systems based on warm‐ and cool‐season components have limited productivity during parts of spring and autumn. Wheat‐grasses (Agropyron and Thinopyrum spp.) and sainfoin (Onobrychis viciifolia Scop.) may improve the seasonal distribution of growth in grazing systems on the U.S. Southern High Plains. Objectives were to determine the herbage production and consumption of three wheatgrasses and their binary mixtures with sainfoin under three schedules of initiation of spring grazing by sheep (Ovis aries). ‘Hycrest’ crested wheatgrass [A. cristatum (L.) Gaertn. ✕ A. desertorum (Fisch. ex Link) Schult.], ‘Jose’ tall wheatgrass [T. ponticum (Podp.) Barkw. & D.R. Dewey], and ‘Luna’ pubescent wheatgrass [T. inter‐medium subsp, barbulatum (Schur) Barkw. & D.R. Dewey] and their mixtures with ‘Renumex’ sainfoin were established on a Pullman clay loam (fine, mixed thermic Torrertic Paleustoll) in 1984. First growths were initially grazed in 1985 and 1986 under three schedules spaced ≈3.5 wk apart. Second growths were grazed ≈6 to 11 wk later. Herbage production of mixtures usually did not exceed that of grasses, but consumption was 13 to 29% greater in mixtures than in pure grasses except under drought conditions. Herbage mass increased with delays in the initiation of grazing in first growths with adequate soil water, and decreased with successive schedules in second growths. Herbage consumption in first growths was greatest for mid or late schedules of grazing initiation. Herbage live leaf and sainfoin concentrations suggest highest forage quality levels for mixtures, particularly in first growths. Wheatgrasses and their mixtures with sainfoin can make important seasonal contributions to the productivity of regional grazing systems.
Field Resistance to Russian Wheat Aphid in Barley: I. Sympton Expression
Authors: Calhoun D. S. , Burnett P. A. , Robinson J. , Vivar H. E.
Published: July 2010

Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a serious pest of wheat (Triticum aestim L.) and barley (Hordeum vulgare L.). This research was conducted to identify barley genotypes resistant to RWA under field conditions. Spring barley genotypes were evaluated during summer 1989 (109 genotypes) and winter 1990 (111 genotypes) at El Batán, Mexico. Hill‐plots of 8 to 10 seeds were infested with 90 to 110 greenhouse‐reared RWA per hill. Hills were visually rated on a 1 to 6 scale (1 no symptoms) for RWA damage at tillering (Zadoks 10 to 29), jointing (Zadoks 30 to 35), and post‐heading (Zadoks 59 to 65). Genotypes differed significantly (P < 0.01) in reaction to RWA at individual scoring dates, and averaged over all scoring dates. Fifteen genotypes were classified as resistant (score < 2.51) based on overall mean score; seven of these were resistant at all scoring dates. The latter included selections from the crosses SMA1/SB401, API/CM67//ACER,ASE/2CM//B.7.6.B.B, GLORIA/COME, CI1255/ARAMIR//GLORIA/3/CI2325/CI12225//BOY*2/3*SURB,ECT/6/M/N//V/4/USB//13914/C/3/SMA/5/SMA, and SD729/POR/3/APM/ATHS//GVA/4/ORE.Significant (P < 0.01) genotype ✕ crop cycle and genotype ✕ growth stage interactions suggest the possibility of improving detection of material with useful levels of resistance by screening in the environment where the material will ultimately be grown, and observing plants at various stages during crop growth. Despite the complication of interaction effects, field screening using artificially infested hill‐plots was effective in identifying barley genotypes that expressed RWA resistance across a broad range of growing conditions and crop development.
Comparative Histology of Cell Walls during Meiotic and Apomeiotic Megasporogenesis in Two Hexaploid Australasian Elymus Species
Authors: Carman John G. , Crane Charles F. , Riera‐Lizarazu Oscar
Published: July 2010

Diplospory in Elymus rectisetus (Nees in Lehm.) Löve & Connor has been compared with megasporogenesis in the close sexual relative Elymus scabrus (R. Br.) Löve. Distinct differences in cell wall morphology were reported. The present study considered the cause of these cell wall differences by comparing cell wall behavior and composition during megasporogenesis in two E. rectisetus and two E. scabrus accessions (Australian wheatgrasses). Micropylar walls of meiotic megaspore mother cells (MMCs) during prophase and metaphase I (MI) were significantly thicker than those of apomeiotic MMCs in corresponding stages. Thickness of chalazal walls during these early stages did not differ. Micropylar, chalazal, and lateral walls of meiotic dyads and tetrads were significantly thicker than those of apomeiotic late stage MMCs, dyads, or binucleate monads. The walls of nucellar cells in E. rectisetus were generally thinner than those in E. scabrus, particularly during the latter stages of megasporogenesis. Callose, which normally envelops MMCs of angiosperms that form monosporic or bisporic female gametophytes, accumulated in and around cell walls of E. scabrus MMCs and was subsequently degraded as in other sexual species. Absence of callose in and around cell walls of MMCs of E. rectisetus appeared to be the major reason for the differences in MMC shape and cell wall thickness. In contrast, callose was detected at abnormal locations in both the nucellus and ovary wall of E. rectisetus. Meiosis with the normal accumulation of callose in and around the cell walls of the MMC and its dyad and tetrad derivatives was infrequently observed in E. rectisetus. Thus, callose accumulation appears to inherently accompany meiosis in these taxa.
Morphological and Anatomical Variations among Barley Cultivars Influence Straw Degradability
Authors: Goto M. , Morita O. , Chesson A.
Published: July 2010

Differences in organization at morphological, anatomical, and molecular levels can influence overall fiber degradability of plant material by rnmen microorganisms. The morphological composition (leaf blade, leaf sheath, and stem content) of straw from three barley (Hordeum vulgare L.) cultivars was determined, and various quantitative anatomical measures, including the proportion of internode area occupied by specific tissues, cell number per unit area, and cellwall thickness, were made on stem sections using scanning electron microscopy (SEM) coupled with image analysis. Values obtained were related to the neutral detergent fiber (NDF) degradability the straws and their botanical fractions. The greater degradability of Doublet compared with Golden Promise and Klaxon was related to its higher leaf content (blade and sheath), and the inherently greater degradability of its leaf and stem fractions. Their differences in stem degradability were also more pronounced than those in leaf degradability. Substantial degradation of the internode tissue was observed, with disruption and erosion of the ground parenchyma cells, and thinning of sclerenchyma cell walls. Although the proportion of tissue area was similar for all cultivars, Doublet and Klaxon had a higher number of ground parenchyma cells per unit area than Golden Promise; Golden Promise, in contrast, had a higher number of sclerenchyma cells. Klaxon had thicker epidermis cell alls than the other cultivars, and thinner ground parenchyma cell walls than Doublet. These observations suggest that the differences in NDF degradability were closely related to variations in the composition and degradability of straw fractions, variations in the number and cell‐wall thickness of specific cell types, and the inherent differences in the degradability of different cell types.
Populations Structuring of Near Infrared Spectra and Modified Partial Least Squares Regression
Authors: Shenk John S. , Westerhaus Mark O.
Published: July 2010

The computer programs CENTER and SELECT have been presented as a way to establish population boundaries and choose samples for near infrared calibrations. This study was conducted to evaluate calibrations derived on samples chosen by CENTER and SELECT from broad groups of hay, haylage, corn (Zea mays L.), wheat (Triticnm aestivum L.), and barley (Hordeum vulgare L.) samples. Population boundaries were established with a maximum standardized H distance from the average spectrum of 3.0. Every fifth sample was reserved for equation validation. Calibration samples were selected with a minimum standardized H distance between samples of 0.6. Forage samples were found to have more diverse spectra and chemistry than grain samples. Average r2 values were smaller, numbers of eigenvectors were larger, and standard deviations of laboratory reference values were larger for forages than for grains. The standard error of performance (SEP) for all samples and SEP for samples chosen by SELECT with a limit of 0.6 were similar for four of five products. Calibrations were developed using five different math treatments with and without multiplicafive scatter correction (De‐trend). First derivative was the best math treatment for protein in all products. Second derivative was best for acid‐detergent fiber (ADF) in forage products, but no single math treatment was superior for ADF in grain products. De‐trend improved SEP in 28 of 50 calibrations.
Leaf Photosynthesis Water Use of Big Bluestem under Elevated Carbon Dioxide
Authors: Kirkham M. B. , He H. , Bolger T. P. , Lawlor D. J. , Kanemasu E. T.
Published: July 2010

With the atmospheric concentration of CO2 increasing, it is importanto know how this will affect crop growth. The objective of the study was to determine the effect of elevated CO2 on big bluestem (Andropogon gerardii Vitman) growing in a tallgrass prairie on Tully silty clay loam (fine, mixed, mesic Pachic Argiustoll) kept a high water level (field capacity) or a low water level (half field capacity). Sixteen cylindrical plastic chambers were placed on the prairie to maintain the two levels of CO2 (mean ± SD: 337 ± 32 and 658 ± 81 µmol mol‐1) over a full growing season. Soil‐water content was measured weekly with a neutron probe. Photosynthesis, transpiration, stonmtal resistance, and intercellular CO2 concentration were determined with a portable leaf photosynthetic system. Canopy temperature was monitored with an infrared thermometer. Elevated (doubled) CO2 reduced transpiration rate of big binestem by 25 and 35% under the high‐ and low‐water treatments, respectively. Under both watering regimes, stomatal resistance was greater by ≈1.6 s cm‐1 with doubled CO2 than with ambient CO2. Plants grown with doubled CO2 at high‐ and low‐water levels had warmer canopy temperatures (average 1.15 and 0.70 °C warmer, respectively) than plants grown ambient CO2. Carbon‐dioxide concentration did not affect the rate of photosynthesis, even though intercellular CO2 concentration was increased under high CO2. Elevated CO2 did not increase the height of plants grown at the high water level, but it did increase the height at the low water level by an average of 9 cm.
Dry Matter Yield, Nitrogen‐15 Absorption, and Water Uptake by Green Bean Under Sodium Cloride Stress
Authors: Pessarakli M.
Published: July 2010

Nutrient absorption and water uptake by plants seem to be impaired under salt stress, resulting in abnormal growth and lower yields. Plant types and species behave differently under stress conditions. Therefore, to select the most suitable green bean (Phaseolus vulgaris L.) cultivar for optimum dry‐matter yield and N and water uptake patterns, the cultivars Tender Improved, Slim Green, and Kentucky Wonder were compared using 15N under three NaCl levels (‐0.03 [control], ‐0.25, and ‐0.50 MPa osmotic potentials). Five days after the start of incubation, seedlings were exposed to light for 7 d and allowed to grow for an additional 7 d in complete Hoagland solution before and 7 d after completion of salt treatments. This was followed by a 15‐d 15N‐uptake period after ammonium nitrate (15NH4 15NO3) addition to nutrient solutions. Nitrogen‐15 was used to determine precisely the amount of N taken up by these cultivars specifically during NaCl stress period. Dry‐matter yield was determined and shoots and roots analyzed for total N and 15N uptake and distribution. Dry‐matter production, total N and 15N absorption, and water uptake decreased with increasing salinity for all cultivars, but Tender Improved was least severely affected by NaCl stress, probably due to its higher salt tolerance. The −0.25‐MPa stress caused >25% reduction in each of these components for each cultivar at each harvest. This value was >50% at −0.50 MPa osmotic potential. Based on the results of this investigation and under comparable conditions, Tender Improved seems the most suitable among these cultivars for growing under field conditions.
Gamma‐Zein Content is Ralated to Endosperm Modification in Quality Protein Maize
Authors: Lopes Mauricio A. , Larkins Brian A.
Published: July 2010

Opaque‐2 (o2) is a mutation in one of the regulatory loci that control storage protein gene transcription in maize (Zea mays L.) kernels. It results in a significant reduction in the prolamine content of the endosperm, which becomes chalky and soft. Quality Protein Maize (QPM) genotypes are modified, hard‐endosperm, o2 mutants that carry genetic factors responsible for increased synthesis of the γzein protein (tool. wt. 27 kD). The genes encoding this storage protein are not under regulatory control of the 02 locus. We used a combination of genetic and biochemical analyses to investigate the relationships between endosperm modification and γ‐zein content in QPM. The use of unmodified and modified genotypes allowed us to demonstrate, by reciprocal crosses and F2 segregating progenies, that degree of vitreousness and increased synthesis of γ‐zein in modified endosperms are both dosage dependent and directly correlated. Additionally, we found that these same genetic factors are active in other soft‐endosperm mutants such as floury‐2 (fl2), and floury‐2;opaque‐2 (fl2;o2), as well as in normal inbred lines. Although endosperm modification appears to be the result of a genetically complex system, its primary effect appears to be on the synthesis of the γ‐zein protein. Our studiesuggest that there may be a relationship between the high content of this protein and increased kernel vitreousness in QPM.
Heritability Estimates of Creeping Bentgrass Root Systems Grown in Flexible Tubes
Authors: Lehman V. G. , Engelke M. C.
Published: July 2010

Turfgrass root systems are often concentrated in upper portions of soil profiles, and consequently depend on frequent precipitation or irrigation to avoid drought stress. Development of cultivars with extensive root systems could make use of greater volumes of soil water. We devised a greenhouse screening technique to characterize root systems of creeping bentgrass (Agrostis palustris Huds.), and to estimate the heritability of root characters. Thirteen clones, excavated in the field, exhibited genetic variation in root extension, tiller number, and root number at 10‐cm soil depths. Flexible, sandfilled polyethylene tubes were used to screen the same 13 clones in the greenhouse. Rank correlations were significant between field and greenhouse performance in root extension, root number through the 20‐cm depth, and tiller number. Parent‐progeny regression of 10 creeping bentgrass clones in flexible tubes indicated narrow‐sense heritabilities of 0.08,0.14,0.31, and 0.61 for root number at the 10‐, 20‐, 30‐, and 40‐cm depths, respectively. Parent‐progeny regression indicated narrow‐sense heritabilities of 0.07, 0.23, 0.27, 0.43, and 0.82 at soil depths of 5 to 10,11 to 20, 21 to 30, 31 to 40, and 41 to 50 cm, respectively, for root surface areas. Narrow‐sense heritability estimates for tiller number and tiller dry weights were 0.31 to 0.41, and 0.32, respectively. Root extension narrow‐sense heritability was 0.62 to 0.76, and was not significantly correlated with either tiller number or weight. The heritability estimates for root and shoot characters from these creeping bentgrass clones suggest progress could be made toward development of more drought‐avoidant turfgrasses, but selection for high tiller number or weight only will not necessarily yield the desired results.
Evaluation of Visual Rating Scales for Green Leaf Retention in Sorghum
Authors: Wanous Michael K. , Miller Frederick R. , Rosenow Darrell T.
Published: July 2010

Visual ratings that can be taken quickly in the field provide information for evaluation and selection that could not otherwise be obtained due to time or cost constraints of quantitative techniques. We evaluated the accuracy of two subjective visual rating systems that assess green leaf retention in sorghum [Sorghum bicolor (L.) Moench] under drought stress in the field: Green leaf retention (GLR) estimates the percentage of total laminar leaf area that is green; number of green leaves (NGL) estimates the number of green leaves. The relationships between GLR, NGL, and two parameters of green leaf area based on measured leaf area (green leaf area or GLA and percent green leaf area or PGA) were examined by correlation and regression analyses. The simple coefficients of correlation (r) for the relationships were GLR/GLA, 0.824; GLR/PGA, 0.926; NGL/GLA, 0.956; and NGL/PGA, 0.923. Linear regressions of these relationships had slopes significantly greater than zero. The GLR/GLA was analyzed as a second‐order relationship, with R2 = 0.821; GLR/PGA, NGL/GLA, and NGL/PGA were analyzed as linear relationships, with R2 = 0.857,0.913, and 0.852, respectively. The R2 values for these relationships were high for biological or agronomic data, confirming the reliability of these ratings for assessing green leaf retention and supporting the validity of such visual rating systems used in sorghum breeding programs.
Mode of Reproduction in Cytotypes of Lehmann Lovegrass
Authors: Voigt P. W. , Burson B. L. , Sherman R. A.
Published: July 2010

All known sources of lehmann lovegrass, Eragrostis lehmanniana Nees, reproduce by apomixis, which precludes hybridization and conventional genetic research. This study was conducted to locate sexual germplasm and describe the reproductive process in lehmann lovegrass. Purported diploid germplasm was grown in pots in a greenhouse. Chromosome number was determined and embryo sac development was studied and compared with another lehmann lovegrass accession. Self fertility, open‐pollinated seed set, and mode of reproduction by progeny test were evaluated. Three accessions were diploid (2n = 2x = 20) and two were tetraploid (2n = 4x = 40). Triploid plants (2n = 3x = 30), discovered in the primarily diploid accessions, probably resulted either from the union of reduced and unreduced gametes or from fertilization of diploid plants by pollen from nearby tetraploid lehmann lovegrass. Diploid plants were sexual (i.e., megaspores were produced) and required cross pollination for seed set. Triploid and tetraploid plants were facultative diplosporous apomicts. Progeny tests were not conclusive. Although some diploid plants were clearly different from others, morphological differences were not sufficient to clearly and easily differentiate genetic from environmental variation. This is the first report of sexual reproduction in E. lehmanniana. This sexual germplasm will be essential to future genetic research with lehmann lovegrass.
Nonstructural Carbohydrate Utilization by Sorghum and Maize Shaded during Grain Growth
Authors: Kiniry J. R. , Tischler C. R. , Rosenthal W. D. , Gerik T. J.
Published: July 2010

Grain sorghum [Sorghum bicolor (L.) Moench] and maize (Zea mays L.) in dryland conditions can experience environmental stress during grain filling, causing increased dependency on stored assimilate. Estimates of maintenance costs and efficiency of production of grain from stored assimilate are important for modeling yield production in such conditions. Our primary objectives in this study were to estimate the maintenance coefficient, the maximum decrease in leaf and stem dry matter, and the efficiency of production of grain from stored assimilate, all with severe stress during grain filling. We measured the loss of sorghum and maize stem dry weight and nonstructural carbohydrate (NCO) content and the increase in panicle and ear dry weight when severe shading stress occurred after anthesis. Extreme shading treatments were imposed from 7 to 8 d after anthesis until physiological maturity on three sorghum cultivars and a maize hybrid in the field at Temple, TX. Shading reduced the combined culm and leaf sheath weights of sorghum by 20 to 33% relative to the weights at anthesis. Measurements of NCO and dry matter of the maize hybrid indicated that 190 to 240 g kg−1 of the stem dry weight at anthesis represented assimilate available for respiration and growth. Mean maintenance coefficient values were 13 mg g−1 dry wt. d−1 for sorghum and 8 mg g−1 dry wt. d−1 for maize. Efficiencies of grain produced from stored assimilate were less than theoretical values. The importance of NCO stored prior to grain filling for maize and sorghum yield modeling appeared to be minimal.
Integrating Matriconditioning and Fungicidal Treatment of Table Beet Seed to Improve Stand Establishment and Yield
Authors: Khan Anwar A. , Abawi George S. , Maguire James D.
Published: July 2010

Preplant conditioning with solid carriers, termed matriconditioning, has proved effective in improving early emergence of vegetable seeds in laboratory studies. The objective of this study was to combine the advantages of matriconditioning with effective fungicide treatments to further improve emergence and yield in table beet (Beta vulgaris L. cv. Ruby Queen). Of the various carriers used, Micro‐Cel E (a synthetic calcium silicate) was found to be more effective than expanded vermiculite or Agro‐Lig (a Leonardite shale). The conditioning mixture consisted of 1 part seed to 0.2 part Micro‐Cel E to 1.15 part water (or fungicide suspension) by weight. Seeds were conditioned for 7 d at 15 °C. Although washing after conditioning improved the early emergence, air‐drying of conditioned seeds, with or without washing, was essential for obtaining maximum stand. A combined treatment of conditioning and metalaxyl [(N‐(2,6‐dimethylphenyl)‐N‐(methoxyacetyl) alanine methyl ester] + tolclofos‐methyl (O‐2,6‐dichloro‐4‐methylphenyl O,O‐dimethyl phosphorothioate) was more effective than the conditioning or fungicide seed treatment alone in improving stand and in reducing seedling mortality at 22 to 25 °C in soil infested with soilborne pathogen, Rhizoctonia solani Kuhn. In noninfested soil, conditioning with metalaxyl + thiram (tetramethylthiuram disulfide) was most effective. At 15 °C, conditioning in combination with metalaxyl + tolclofos‐methyl or metalaxyl + thiram induced earlier emergence and produced larger stands than did conditioning or fungicide treatment alone. In a filed trial planted on 1 May 1990, conditioning combined with metalaxyl + tolclofos‐methyl or metalaxyl + thiram produced a larger stand than did conditioning or fungicide treatment alone. In a field trial planted on 21 June 1990 and artificially infested with mycelial suspensions of R. solani and Pythium ultimum Trow, conditioning combined with metalaxyl + tolclofos‐methyl or metalaxyl + thiram reduced the early emergence time and increased the marketable root yield over that of conditioning or fungicide treatment alone. Root disease incidence was reduced maximally when conditioning was combined with metalaxyl + tolclofos‐methyl, to a lesser extent by fungicides alone, and none by conditioning alone.
Tissue Culture Regeneration of Desmodium
Authors: Wofford D. S. , Quesenberry K. H. , Baltensperger D. D.
Published: July 2010

Efficient tissue culture techniques for plant regeneration are known for many crops, but very considerably among species. These procedures need to be investigated, however, in crops that have no known method of regeneration. Six genotypes of two species of Desmodium were evaluated for tissue culture response on two protocols, an L2 basal salts + growth regulators embryogenic protocol and an MS basal salts + growth regulators organogenic protocol. Significantly greater callus growth was observed on the L2 callus induction medium for four of the six genotypes, with an average of 476.6 mg callus−1 for all genotypes on L2 compared with 47.9 mg callus−1 for the MS treatment. Based on L2 callus fresh weight data, genotypes could be classified into two groups, good and poor callus producers. Despite the overall poor callus growth on MS, shoot buds were induced for five of the six genotypes on the MS shoot induction medium. No genotypes produced somatic embryos on the L2 protocol; however, two genotypes, CIAT 6123 and CIAT 13083, did exhibit organogenesis on the L2 protocol. Plants were regenerated from CIAT 6123 on the L2 system. No shoot development was observed for any genotype on the MS treatment. Regenerated plants were phenotypically normal and no somaclonal variation was observed. Media modifications will be necessary in order to successfully manipulate Desmodium genotypes in vitro.
Heritability of Oat Mosaic Resistance
Authors: Uhr David V. , Murphy J. Paul
Published: July 2010

Detailed knowledge about the heritability of oat mosaic (OM) resistance would help breeders to more effectively plan strategies for incorporating OM resistance into new cultivars. The objective of this study was to estimate the heritability of resistance to OM in winter oat (Avena sativa L.) using variance component analysis, parent‐offspring regression, parent‐offspring correlation, and realized heritability. One hundred random F2:3 lines and their F2:4 progeny from a double‐cross population (NC 82‐45/NC 82‐79/2/NC 84‐67/NC 84‐68) were evaluated in six replicates of hill plots for 2 yr at two North Carolina locations. Soil type at the Piedmont Research Station was a Hiwassee clay loam (clayey, kaolinitic, thermic, Rhodic Kanhapludult) and at the Central Crops Research Station was a Cecil sandy clay loam (clayey, kaolinitic, thermic, Typic Kanhapludult). Resistance was estimated visually with a leaf mosaic symptom scale during the spring vegetative growth stage (GS 31). Broad‐sense heritability estimates based on entry means were 0.75 for F2:3 lines and 0.84 for F2:4 lines. The parent‐offspring regression coefficient was 0.80 and parent‐offspring correlation was 0.73. Realized heritability was 0.99, based on entry means from four environments. Heritabilities in a second population (Brooks/NC 81‐341/2/NC 83‐123/Madison) evaluated at one location over 2 yr were smaller. The results suggested that considerable progress may be expected from visual selection for OM resistance in segregating populations.
Selection Criteria for Grain Yield and Moisture in Maize Yield Trials
Authors: Eta‐Ndu J. T. , Openshaw S. J.
Published: July 2010

Grain yield and moisture in maize (Zea mays L.) are positively correlated, and must be considered simultaneously. Typically, breeders desire to identify better‐yielding hybrids within each of several maturity groups. Data from 28 multiple‐location yields trials were used to (i) compare five indices for ability to identify hybrids that are high yielding for their maturity; (ii) investigate the validity of assumptions used in developing estimated indexes; and (iii) investigate possible relationships between effectiveness of indexes and violations of assumptions. Selection criteria evaluated included: BSE, a base index; S‐H, a Smith‐Hazel index; Y/M, the ratio of yield and moisture; REG, yield adjusted for the regression of yield onto moisture; and DSG, a desired gains index designed to hold moisture constant. Departures from normality for distribution of grain yield means and for moisture were detected in 18 and 32% of the experiments, respectively. The regression of yield onto moisture varied considerably across experiments, with a mean coefficient of 12.5 kg ha−1 yield per g kg−1 moisture. Selection differentials of REG, BSE, and DSG for yield were 92, 91, and 89% respectively of that resulting from direct selection for yield, but changes for moisture were considerably less than those for selection based on yield. The Y/M selection differential for yield was only 64% of that of yield, and had a large decrease in grain moisture. No association between the success of an index and nonnormality was observed. Both BSE or REG are recommended for identification of hybrids that are high yielding for their maturity. However, these or other indices employed should be carefully evaluated in the context of the breeder's circumstances and objectives.
Gas Exchange Traits and Their Relationship to Water Use Efficiency of Grain Sorghum
Authors: Peng Shaobing , Krieg Daniel R.
Published: July 2010

Bleeding for increased water use efficiency (WUE) has been limited by the lack of screening criteria and methods for selecting desirable genotypes from large populations under field conditions. The purpose of this experiment was to determine whether genetic variation in gas exchange traits reflects differences among sorghum genotypes [Sorghum bicolor (L.) Moench] in WUE and thus could be used as screening criteria. Five sorghum genotypes were grown in the greenhouse and field during 1989 under well‐watered conditions. In the greenhouse study, individual entries were planted in plastic pots. The field experiment was conducted on an Amarillo loamy fine sand (fine‐loamy, mixed, thermic Aridic Paleustalf). Shoot biomass production, water use, and leaf area development were determined. Gas exchange measurements were made throughout the vegetative stage on uppermost fully expanded leaves, using a portable photosynthesis systems. The sorghum genotypes exhibited significant and consistent variation in C assimilation rate (A), shoot biomass and leaf area production, and WUE. No consistent genotypic variation was observed for transpira. tion (T) or whole‐plant water use rates. Single leaf measurements of .4 reflected single‐plant and whole‐canopy WUE differences among the genotypes, largely due to the positive correlation between A and shoot biomass production. In addition, there was a positive correlation among the genotypes between leaf area and A. The results indicate that measurements of A and leaf area reflected biomass production, which was the primary determinant of water use efficiency, since minor nonsignificant differences existed among the genotypes in water use.
Ear and Kernel Formation in Maize Hybrids Representing Three Decades of Grain Yield Improvement in Ontario
Authors: Tollenaar M. , Dwyer L. M. , Stewart D. W.
Published: July 2010

Increased prolificacy and reduced barrenness have been identified as physiological traits in maize (Zea mays L.) hybrids that are tolerant of environmental stresses induced by high plant density. The objective of this study was to investigate ear and kernel formation under a range of plant densities in old and new hybrids. Experiments were carried out during 1987 and 1988 at two locations in Ontario with nine maize hybrids representing three decades of yield improvement in Ontario, grown at 2, 4, 8, 10, and 13 plants m−2. Dry matter was measured at 1 wk presiiking, 3 wk postsilking, and at physiological maturity and plant growth rates calculated for both periods. Grain yield, kernel weight, and kernel number were determined at physiological maturity. Kernels per plant and plant growth rate for the period from 1 wk presilking to 3 wk postsilking could be fitted to a discontinuous function of multiple rectangular hyperbolae; a single rectangular hyperbola was associated with the kernel number on each grain‐bearing ear. The first rectangular hyperbola for each hybrid had a positive x‐axis intercept, which was interpreted as the threshold plant growth rate for ear formation. The analysis showed that grain yield improvement of Ontario maize hybrids was associated with an increase in kernel number per plant and higher plant growth rates from 1 wk presilking to 3 wk postsiiking. The increase in kernels per plant was associated with an increase in ears per plant. The increased prolificacy of recent hybrids appeared to be the combined result of higher rates of plant dry matter accumulation during silking and a greater inherent tendency to exhibit prolificacy. The lower barrenness of recent hybrids at high plant densities was associated with higher plant growth rates, but was not the result of a lower threshold plant growth rate for ear formation.
Soybean Pubescence and Its Influence on Larval Development and Oviposition Preference of Lepidopterous Insects
Authors: Lambert Lavone , Beach R. M. , Kilen T. C. , Todd J. W.
Published: July 2010

Lepidopterous insects often cause serious economic damage to soybean, Glycine max (L.) Merr. One possible source of resistance to these pests is plant pubescence. To determine the effects of pubescence on the larval stages of corn earworm (CEW), Helicoverpa zea (Boddie), velvetbean caterpillar (VBC), Anticarsia gemmatalis Hübner, and soybean looper (SBL), Pseudoplusia includens (Walker), they were reared on foliage of ‘Tracy‐M’ lines isogenic for dense, normal, or glabrous pubescence. In addition, SBL was reared on foliage of ‘Davis’ lines isogenic for the same characters. To determine the effect of pubescence on oviposition preference and on subsequent larval defoliation levels, SBL and VBC imagoes were allowed to oviposit, under free choice conditions, on Tracy‐M lines isogenic for dense, normal, and glabrous pubescence type. In all instances, larval growth and development were significantly (P ≤ 0.05) reduced and oviposition preference was significantly increased by the presence of plant pubescence. Corn earworm larvae were more affected by pubescence than SBL or VBC larvae, as exhibited by a greater increase in larval development time and a greater decrease in pupal weight when reared on normal and dense isolines. No differences were noted in VBC and SBL growth and development on normal vs. dense isolines. In one environment, SBL deposited significantly more eggs on dense plants than on normal plants. Larval populations of both SBL and VBC produced a significantly higher level of defoliation on normal and dense isolines than on the glabrous isoline. These results show that pubescence of soybean, when compared with plants without pubescence, functions as a resistance mechanism to the larval stage of lepidopterous defoliators but enhances adult oviposition. Under free‐choice conditions, the level of increased larval damage due to the superior food substrate of glabrous plants is more than offset by the reduction in oviposition on these plants.
Estimation of Leaf Area from Leaf and Total Mass Measurements in Peanut
Authors: Ma L. , Gardner F. P. , Selamat A.
Published: July 2010

Leaf area index (LAI) is important for light interception, radiation‐use efficiency (RUE), and plant growth; however, determination LAI requires substantial capital investment, often not available in developing countries. On the assumption that there is a sufficiently close relationship between leaf area (LA) and leaf dry weight (LDW) and possibly total biomass (TBM), it should be possible to estimate LA from these parameters. Therefore, eight peanut (Arachis hypogaea L.) cultivars varying widely in growth habit were harvested at 10‐d intervals, starting from 30 days after planting (DAP) until harvest maturity in 1989 and used to determine LA from both LDW and aboveground TBM. The relationship between LA and LDW and LA and TBM were determined by two statistical models: linear and nonlinear. The general nonlinear model (LA = 0.0234 × LDW0.97) derived from LDW gave the best fit (R2 = 0.98) and standard error (SE = 0.71), compared with the TBM model (LA = 0.0205 × TBM0.85; R2 = 0.95; SE = 0.83). Both LA‐LDW and LA‐TBM models were validated using data from an experiment conducted in 1985, which showed a good agreement between the estimated and measured LA. The LA‐LDW nonlinear model produced estimations close to 1:1 (R2 = 0.98). Although cultivars exhibited disparate morphology and growth habit, specific cultivar models differed only slightly from one another. Therefore, we concluded that the general nonlinear model (LA =0.0234 ✕ LDW0.97) can accurately estimate leaf area of peanut canopies across a wide range of cultivars and growth stages.