bluuebunny/crossref_metadata_2025 huggingface dataset:
Forage Quality and Yield in 4X Progeny from Interploidy Crosses in Dactylis L.
Authors: van Santen Edzard , Casler M. D.
Published: July 2010

Important goals in forage‐grass breeding are improvement in forage yield and quality. The objectives of this study were to evaluate 4x offspring from interploidy crosses of Dactylis L. and 4x‐4x crosses, one parent in each cross originating from wild germplasm. Tetraploid parental and offspring genotypes were planted at three locations in Wisconsin. Each plant was surrounded by solid‐seeded cultivated orchardgrass (Dactylis glomerata L.) to provide root and shoot competition without losing the identity of individual genotypes. Plants were harvested three times during 1987 and dry‐matter yield (DMY) determined. Each plant was analyzed for forage quality traits (in vitro dry‐matter disappearance, neutral detergent fiber, acid detergent fiber, acid detergent lignin). Statistical analysis was done for total seasonal dry‐matter yield and the weighted average of forage quality traits over harvests. Means and ranges among genotypes were generally similar for forage quality traits in parents and offspring. The performance of offspring for DMY was inferior to the parents. Significant (P ≤ 0.05) genotypic effects were detected for parents as well as offspring. Genotype ✕ location interaction was significant (P ≤ 0.05) for all traits but one in each generation. There was variation for more traits among 2x‐4x families than for other family groups. Within‐family variation for forage quality traits was not consistent. For DMY, all but one 4x‐2x family had significant (P ≤ 0.10) within‐family variation, whereas no 2x–4x family showed this variation. The performance of offspring families appears to be more related to the cultivated 4x parent than to the parent from wild germplasm. There was sufficient variation in the desired direction for all traits to permit phenotypic selection of offspring genotypes exceeding the best parents.
Shading and Thinning Effects on Multi‐ and Standard‐Floret Winter Wheat
Authors: Jedel P. E. , Hunt L. A.
Published: July 2010

Grain set in a crop is related to many factors, including genotype and assimilate supply. This study was conducted to examine differences in grain set in two winter wheat (Triticum aestivum L.) cultivars differing in spike characteristics. The multiflorous cultivar Benni and the standard floret cultivar Houser were investigated in field studies at Elora and Woodstock, Ontario, Canada. In 1984, three 50% of full daylight shading treatments were imposed (PRE: a 2 wk period prior to anthesis; POST: 2 wk following anthesis; PRE + POST: 2 wk prior to anthesis plus the 1 wk following anthesis). In 1985, a postanthesis thinning treatment (THIN), in which stem number was reduced by 50%, was added. In 1984, Houser had reduced total aboveground biomass and grain yields per meters squared with the PRE and PRE + POST treatments. Grain yield reduction was associated with reduced kernel number per meters squared. For Benni in 1984, shading treatments affected neither total biomass nor grain yield. In 1985, all shading treatments reduced total biomass and grain yield for Houser, while treatments PRE and PRE + POST reduced total biomass and treatments PRE + POST and THIN reduced grain yield for Benni. Grain yield reduction for Houser was associated with reduced kernel weight for all treatments and reduced kernel and spike numbers per meters squared for treatment PRE + POST. Reduced grain yield for Benni was associated with reduced kernel numbers for treatments PRE + POST and THIN and spike numbers for treatment PRE + POST. The responses, usually manifest in a similar aboveground biomass production under different shade conditions, suggest that some internal limitation was present.
Postemergence Mortality and Barrenness of Two Maize Hybrids Affected by Tillage and Nitrogen
Authors: Olness Alan , Evans S. D. , Harris K. R. , Rinke J. L. , Gooch S.
Published: July 2010

Tillage and/or fertilizer N by hybrid interactions in maize (Zea mays L.) affect resource use efficiency. Our objective was to document these interactions for postemergent mortality (PEM) and barrenness of two maize hybrids, Pioneer Brand Hybrid 3906 (Pi 3906) and Dekalb‐Pfizer XL8 (De XL8). The PEM was measured in continuous tillage‐continuous maize‐N (CTMN) study in 1985 and 1986 and a continuous tillage maize‐soybean [Glycine max (L.) Merr.I rotation (TMSR) study in 1986 and 1987. The CTMN and TMSR field experiments were conducted on a Tara silt loam (fine, silty, mixed Pachic Udic Haploboroll) and Doland silt loam (fine, loamy, mixed Udic Haploboroll), respectively, in a randomizedblock design. Tillage‐N combinations were moldboard plow (MP), chisel plow (CP), ridge till (RT), and no‐till (NT) with fertilizer (N) applied in the fall as anhydrous ammonia at 0, 5.6, 10.8, 16.4, and 22.7 g m−2 N, plus 0.9 g m−2 N applied as starter fertilizer. The PEM was recorded only for NT and MP tillage treatments, which had received 6.5 and 17.3 g m−2 N in the CTMN study and 18.0 g m−2 N in the TMSR study. Plant and emergence marker counts were recorded in two 9.2‐m row lengths at 2‐d intervals for 6 wk and thence weekly until harvest. Plant losses in De XL8 ranged from about 3 to 6% and 4 to 12% in the CTMN and TMSR studies, respectively. Plant losses in Pi 3906 ranged from 2 to 3% in both studies. The PEM of Pi 3906 with no‐tillage treatments was significantly less than that of De XL8, but not different from other tillage‐hybrid combinations. Plant barrenness at harvest decreased significantly as applied N rate increased only in De XL8; in 1986 (third year of CTMN study), barrenness generally decreased from greater than 40 to less than 10% as the intensity of tillage increased. Barrenness in Pi 3906 was unaffected by tillage.
Manganese Toxicity Effects on Visible Symptoms, Yield, Manganese Levels, and Organic Acid Levels in Tolerant and Sensitive Wheat Cultivars
Authors: Burke Daniel G. , Watkins Karina , Scott Brendan J.
Published: July 2010

The effects of elevated plant intake of Mn were studied to determine whether an accurate and objective criterion could be found to identify wheat breeding lines possessing the Mn tolerance genotype. Seven wheat (Triticum aestivum L.) cultivars (‘Teal’, ‘Lance’, ‘Isis’, ‘Maringa’, ‘Warigal’, ‘Carazinho’, and BH1146) were grown in solution culture at basal (0.5 mg/L) and increased (30, 60,90, and 180 mg/L) Mn concentrations in order to determine their biochemical response to Mn toxicity. The cultivars Teal and Isis had severe toxicity symptoms at 90 and 180 mg Mn/L. Carazinho and Warigal were unaffected at all Mn rates tested. Lance and Maringa were symptom free to 90 mg/L, while at this level BH1146 had easily visible symptoms. The reduction in dry matter yield was greatest for Teal and Isis and reflected the same pattern as observed with symptoms. In plant shoots, Mn levels were generally highest for those cultivars having least toxicity symptoms; Carazinho and Warigal had maximum levels approaching 4000 mg/kg dry matter. Reduction in dry matter yield of roots was not strongly correlated with Mn levels. Aconitic acid concentration in shoots of sensitive cultivars increased 14‐fold to a maximum value of about 30 mmol/kg fresh weight with 90 mg Mn/L in solution. There were smaller increases in the concentrations of malic and citric acids. The levels of these three acids did not change in the two tolerant cultivars.
Visualizing Interactions of Water Stress Responses with a Whole‐Plant Simulation Model
Authors: McCree K. J. , Fernandez C. J. , de Oliveira R. Ferraz
Published: July 2010

Simulation models provide a framework for visualizing how different physiological responses may be interacting when plants respond to water stress. The model McStress was used to evaluate data for rates of whole plant gas exchange of three species that showed contrasting responses to water stress under controlled environment conditions. Inputs to the model were systematically varied until the outputs matched the data. Excellent agreement was obtained. In analyzing how the model achieved the match, it became apparent that many of the differences among species could be explained by differences in leaf conductance under well‐irrigated conditions without invoking differences in stress response. The analysis showed both the boundary layer component and the stomatal component contributing to species differences in simulated leaf conductance, sometimes in opposite directions. Analysis of water use efficiency and carbon use efficiency data pointed up complex interacting effects of accelerated senescence on rates of photosynthesis and respiration that could not be discerned in the data. The relationship between root biomass and water uptake was analyzed by introducing the idea that only fine roots are capable of taking up water. The analysis could have been made even more realistic if the model had included gradients in water potential.
Carbon Isotope Dicrimination: Potential in Screening Cool‐Season Grasses for Water‐Limited Environments
Authors: Johnson Douglas A. , Asay Kay H. , Tieszen Larry L. , Ehleringer James R. , Jefferson Paul G.
Published: July 2010

Carbon isotope discrimination (∆) has been shown to be negatively related to water use efficiency (WUE) in several C3 crop species and has been proposed as a criterion to select for improved WUE in plant breeding programs. This study was conducted to determine if ∆ is related to WUE in crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] and AItai wildrye [Leymus angustus (Trin.) Pilger] and to evaluate the influence of drought on the magnitude of genetic variability and broad‐sense heritability of ∆ among clones of crested wheatgrass. In a greenhouse pot experiment, ∆ was negatively related to WUE in crested wheatgrass (r = −0.73**, significant at P < 0.01) and Altai wildrye (r −0.81**). In field studies, a line‐source sprinkler system operated in conjunction with an automated rainout shelter imposed a continuously variable water application on 29 vegetatively propagated clones of crested wheatgrass. Three water levels along the water application gradient were selected for sampling and forage dry weights and ∆ values were determined for two harvests in 1986 and one harvest in 1987. In the field experiment, ∆ declined as less water was applied and was positively associated with forage yield at each of the three harvests (r = 0.59**, 0.44**, and 0.80**, respectively). Significant variability for ∆ was detected among the clones for the two peak‐season harvests, hut not for the late‐season harvest in 1986. Broad‐sense heritability for ∆ was 0.49 in the analysis of data combined over harvests and water levels. Genetic variances and broad‐sense heritabilities (H) for ∆ were generally greater at the high (H = 0.52) and intermediate (H = 0.52) water applications than at the low water application (H = 0.37), and coefficients of variation for ∆ were typically less than 4.5%. Selection for ∆ appears to be a promising screening tool for the development of crested wheatgrass populations that are productive and make efficient use of limited water resources.
Defoliation Effects on Grain Filling of R‐nj Color‐Selected Maize Strains
Authors: Mostafavi M. R. , Cross H. Z.
Published: July 2010

Grain yield in maize (Zea mays L.) is often related to rate and duration of grain filling, which can be influenced by selection for R‐nj aleurone color expression. This study was conducted to determine how modifying the source/sink ratio affects grain‐filling characteristics and R‐nj color expression from two genetic backgrounds. Field experiments were conducted at Fargo, ND, with six synthetic strains derived from NDSF (early maturing) and NDSC (late maturing) and divergently selected for R‐nj color expression. A single plant from each plot was tagged and pollinated with bulked pollen from ‘Cudu’, a source homozygous for R‐nj. Three defoliation treatments (0, 50, and 100%) were applied at silking. Four sequential 15‐kernel samples (five each from the apical, mid‐ear, and basal sections of the ears) were taken at 3‐ to 4‐d intervals from alternate kernel rows during the linear phase of grain filling and at kernel maturity. Combined analyses of data over years indicated that source reduction (defoliation) reduced color intensity (CI), rate of dry matter accumulation (RDMA), and kernel weight. Strains selected for high color expression had higher RDMA and kernel weight than low color selections. As expected, the CI ratings corresponded to color selection groups. Color expression was positively correlated with RDMA and kernel weight. Results suggest that R‐nj color expression is related to sugar concentration in the endosperm during kernel development, and that selection for differences in color expression may be a simple, inexpensive means of modifying RDMA.
Preharvest Kernel Infection by Aspergillus flavus for Resistant and Susceptible Maize Hybrids
Authors: Scott Gene E. , Zummo Natale
Published: July 2010

Kernel infection of maize, Zea mays L., by Aspergillus flavus Link ex Fr. and subsequent aflatoxin production is a frequent and serious problem in the southeastern USA. Some maize inbreds with resistance to kernel infection by A. flavus in the field have been identified. The objective of this study was to compare the level of kernel infection by A. flavus for 15 crosses among six resistant inbreds with IS crosses among six susceptible inbreds. The top ear of each plant was inoculated with the fungal spores using the pinbar inoculation technique. Crosses among resistant inbreds averaged 16.6% infected kernels compared with 30.4% for hybrids among susceptible inbreds during 2 yr of testing. Thus, incidence of A. flavus kernel infection in resistant crosses was 45% less than for hybrids of susceptible inbreds.
Adventitious Somatic Embryogenesis from Cultured Immature Zygotic Embryos of Peanut and Soybean
Authors: Sellars Rebecca M. , Southward G. M. , Phillips Gregory C.
Published: July 2010

The ability to regenerate plants from tissue cultures of Arachis has been limited to a few species and, in most cases, to short‐term cultures. Tissue cultures of peanut (A. hypogaea L.) usually are derived from seedling explants and regenerate by organogenesis. This study evaluated the potential to induce somatic embryogenesis in peanut (‘NC‐7’, ‘Comet’, and ‘McRan’) and A. paraguariensis Chod. & Hassel., in comparison to a similar regeneration system in soybean [Glycine max (L.) Merr. ‘Forrest’] and G. canescens F.J. Herm. Intact, immature zygotic embryos were cultured on L2 media with various hormonal treatments. Adventitious somatic embryogenesis was induced from 53% of the cultured immature zygotic embryos of McRan, Comet, NC‐7, and A. paraguariensis, compared to 29% for Forrest and G. canescens, scored after 30 d incubation. By the end of the test period (150 d of culture), Arachis formed an average of 29 somatic embryos per explant compared to 16 for Glycine. An average of 77% of the peanut somatic embryos formed shoots and 61% formed roots compared to 30% shoots and 33% roots for soybean. This regeneration system offers an additional and more efficient tool for peanut biotechnology research programs.
Relative Resistance of Cotton Lines to Pink Bollworm
Authors: Wilson F. Douglas
Published: July 2010

Pink bollworm (PBW), Pectinophora gossypiella Saunders, is a serious insect pest of cotton, Gossypium hirsutum L., in the irrigated deserts of the southwestern USA. Several sources of resistance to PBW have been identified in cotton. The objectives of this study were to determine whether certain other sources are equal or superior to a resistance standard. AET‐5 (as shown by the amount of seed damage sustained by the plants), and whether F1 hybrids show higher levels of resistance than expected based on parental response. A series of diallel and generation‐mean experiments was grown in the field at Tempe and Maricopa, AZ, from 1982 to 1987. No insecticide was applied. The diallel analyses revealed significant general and specific combining ability (GCA and SCA) and reciprocal effects, as well as year ✕ GCA and year ✕ SCA interactions, which complicated the interpretation of the data. However, it was clear that of the 13 lines evaluated, only Stoneville 7A okra leaf was equal to AET‐5 as a source of PBW resistance. The line 7203‐14‐104, while showing some PBW resistance, was inferior to AET‐5. Furthermore generation‐mean analysis of AET‐5 ✕ 7203‐14‐104 data revealed large nonadditive genetic effects, which would make it difficult to combine or transfer resistance. Texas 39C‐1‐L behaved inconsistently with respect to PBW resistance; however, this line has a higher yield potential than AET‐5 and, from this standpoint, deserves continued evaluation. No F1 hybrid and only one F1 reciprocal hybrid had significantly lower seed damage than that of the lowest parent.
Northern Root‐Knot Nematode Populations and Soil Temperature Effect on Alfalfa
Authors: Griffin G. D. , Rumbaugh M. D. , Crebs D. L.
Published: July 2010

Resistance is the only practical method of controlling northern root‐knot nematode [Meloidogyne hapla (Chitwood)] on alfalfa (Medicago sativa L.). This study was conducted to determine if physiological differences in geographically separated nematode populations affected the resistance and susceptibility of alfalfa to M. hapla. The host/parasite relationship between resistant and susceptible alfalfa and five M. hapla populations was investigated at Logan, UT in regulated greenhouse and growth chamber studies. Meloidogyne hapla‐susceptible ‘Ranger’ alfalfa was 100% susceptible to all M. hapla populations, while M. hapla‐resistant Nevada Synthetic XX (Nev Syn XX) germplasm differed in the percentage of plants susceptible to California 1 (CA1), California 2 (CA2), Utah (UT), Nevada (NV), and Wyoming (WY) populations. Ranger was 100% susceptible to all populations at soil temperatures of IS to 30 °C. The Nev Syn XX was 100% susceptible to CA1 at all temperatures, but differed in the percentage of susceptibility to the other populations at temperatures of 20 to 30 °C (P < 0.05). Reproduction on Ranger for all nematode populations was greatest at 25 °C (P < 0.05), while CA1 and CA2 had a higher reproduction rate at 30 °C than the other populations. On Nev Syn XX, the greatest reproduction for CA1 occurred at 25 °C, and with the other populations at 30 °C (P < 0.05) where resistance was lost. Shoot dry weights of Ranger were less at 30 °C for CA1 and CA2, and at 25 °C for the other nematode populations (P < 0.05). The greatest reduction of Nev Syn XX shoot growth by CA1 occurred at 25 °C. Physiological differences in the virulence and reproduction of M. hapla populations and the effect of soil temperatures on expression of plant resistance should be considered in an alfalfa breeding program involving this nematode.
Variability for Recombination Frequencies in the AP12 Soybean Population
Authors: Pfeiffer T. W. , Vogt S. D.
Published: July 2010

Repeated intermating in a plant‐breeding procedure increases the number of meiotic cycles and the opportunities to break genetic linkages, but it also increases the number of generations required to complete a round of the procedure. Because a 50% increase in recombination over the normal level in an F1 generation would be as effective in breaking linkages as one generation of intermating of F2 individuals, genetic control of recombination might be usable in place of repeated intermating. The objectives of this study were to determine if variability in recombination frequency exists in the API2 soybean [Glycine max (L.) Merr.] population and to isolate genotypes with increased or decreased recombination rates. Recombination frequencies were measured in F2 populations of 50 AP12 individuals crossed with each of three ‘Clark’ near isolines containing the respective linkage groups P1r, lnp2, and dt1L1. For each of the three linkage groups, significant (P ≤ 0.05) variability for recombination frequency existed among individuals in the AP12 population, and the recombination frequencies were normal|y distributed. As in many other organisms, recombination frequency of soybean appears to be under polygenic control. Correlation coefficients of recombination frequencies among individuals across the three linkage groups were nonsignificant (P > 0.05). Although genotypes were present with recombination frequencies above or below the population mean for all the linkage groups, a genotype that generally enhances or represses recombination was not isolated.
Genotypes and Plant Densities for Narrow‐Row Cotton Systems. I. Height, Nodes, Earliness, and Location of Yield
Authors: Kerby T. A. , Cassman K. G. , Keeley M.
Published: July 2010

Recent yield advances in cotton (Gossypium hirsutum L.) hive been associated with early fruiting and high harvest index (hi). This study was conducted to examine the effects of plant density in a narrow‐row (0.76‐m interrow spacing) system on plant morphology, fruiting pattern, and yield of five genotypes that differ in degree of determinacy. ‘Acala SJ‐2’, ‘Acala SJC‐1’, and 2218, 2280, and 2086 (USDA‐ARS Shafter short‐season germplasm) were grown in a factorial design at 5, 10, and 15 plants m‐2 in 1984 and 1985. Growth data were collected four times daring the season and fruiting data obtained from plant mapping at the end of the season. Genotypes did not differ in plant height until after anthesis, when the most indeterminate genotype (Acala SJ‐2) continued vegetative growth longer than the more determinate genotypes 2280 and 2086. Increasing plant density from 10 to 15 plants m‐2 delayed maturity of the more indeterminate genotypes but had no effect on the shorter, more determinate 2280 and 2086. Genotypes 2280 and 2086 were earlier mataring than the other three genotypes regardless of plant density. Earliness was associated with a lower node number of the first fruiting branch, more rapid production of early main‐stem nodes, and increased retention of early fruiting forms. Lint yield decreased 59 kg ha‐1 for each O.l‐m increase in final plant height between 0.77 and 1.36 m when genotypes were grown at 15 plants per m‐2; at densities of 5 and 10 plants m‐2, there was no significant relationship between lint yield and plant height across genotypes and years.
Soybean Germplasm Evaluated for Resistance to Races 3, 5, and 14 of Soybean Cyst Nematode
Authors: Young L. D.
Published: July 2010

Additional resistance to soybean cyst nematode (SCN), Heterodera g1ycines Ichinohe, has been identified by screening the USDA soybean, Glycine max (L.) Men., collection. Approximately 600 plant introductions in Maturity Groups V through X have been added to the collection since Anand and Gallo screened the germplasm for SCN Race 3 resistance in 1984. The new additions were evaluated for resistance to SCN Races 3, 5, and 14 in the greenhouse by inoculation with approximately 1000 SCN eggs and enumeration of the cysts on the roots and in the soil at 30 d after planting. The PI 424137B was moderately resistant to the three races having 17 to 31% as many cysts as the susceptible check ‘Lee’. Plant Introduction 399061, Pl 424595, and PI 438342 were highly resistant to Race 5 but were susceptible to Races 3 and 14. This is the first time soybean lines have been identified as susceptible to Race 3 and highly resistant to another SCN race.
Disease Progression and Leaf Area Dynamics of Four Peanut Genotypes Differing in Resistance to Late Leafspot
Authors: Pixley K. V. , Boote K. J. , Shokes F. M. , Gorbet D. W.
Published: July 2010

Leafspot epidemics caused by Cercospora arachidicola Hori (CA) and Cercosporidium personatum (Berk. & Curt.) Deighton (CP) cur every year on peanut (Arachis hypogaea L.) in the southeastern USA and can reduce yields even in fungicide‐treated fields. In this study, leafspot epidemic rates and leaf area dynamics were compared for the widely grown but susceptible cultivar Florunner and three genotypes (Southern Runner, F81206, and MA72x94‐12) having partial resistance to CP. Field studies were conducted at Marianna, FL in 1983 and at Gainesville, FL in 1985. Percent necrotic area in three leaf canopy layers (estimated using modified Horsfall‐Barratt diagrams), defoliation of the main stem (determined by counting missing leaflets), and leaf area index (LAI) were recorded at 7 10‐d intervals. In plots receiving no fungicide, rates of disease progress were one‐half to two‐thirds as great and areas under disease progress curves were 10 to 30% as large for the resistant genotypes as for Florunner. All genotypes lost similar amounts of LAI in response to disease, but defoliation was more complete for Florunner than for the other genotypes. Maintenance of higher LAI by these resistant genotypes was associated with sustained leaf production until maturity. The combination of lower epidemic rates with continned leaf growth (compensating for diseased leaves) appears reduce the adverse effects of leafspot on assimilation and yield capability of these resistant lines. Nevertheless, leaf replacement is probably not the optimum mechanism for minimizing effects of leafspot diseases, because leaf growth requires energy that could otherwise be available for pod growth.
Switchgrass Herbage and Seed Yield and Quality with Partial Spring Defoliation
Authors: George J. R. , Reigh G. S. , Mullen R. E. , Hunczak J. J.
Published: July 2010

Partial defoliation of switchgrass (Panicum virgatum L.) during early to mid‐June followed by a regrowth period can provide high yields of quality forage for midsummer grazing. No information is available on effects of partial spring defoliation on subsequent sameyear seed yields. The objective was to determine the effect of spring defoliation and N fertilization on spring herbage yield and quality and fall seed yield and quality of switchgrass cultivars. Established swards of ‘Cave‐in‐Rock’ (CR), ‘Pathfinder’ (PF), and ‘Blackwell’ (BW) switchgrass were grown in Ames, IA, on a Webster‐Nicollet soil complex (fine‐loamy, mixed, mesic Typic Haplaquoll—Aquic Hapindoll) with 0 or 90 kg N ha−1 for 2 yr. Spring herbage yield was highest for CR. Mean yield increased 0.11 and 0.16 Mg ha−1 d−1 between late May and mid‐Jane and reached 1.97 and 3.01 Mg ha−1, respectively. Herbage crude protein (CP) and in vitro dry matter digestibility (IVDMD) decreased linearly 3.36 and 3.57 g−1 d−1 respectively, daring the same period. Herbage CP and IVDMD concentrations were increased by N fertilization, whereas N reduced days to anthesis for PF and BW but had no effect on CR. Mean anthesis date was delayed 0.36 d for each day of delay in defoliation after late May; more so for CR (an earlier and more rapidly growing cnltivar) than for PR and BW. Cultivar seed yield was similar, and N more than doubled seed yield. Seed yield of the uncut check (521 kg ha−1) was highest. Defoliation reduced seed yields 27.7 and 11.5 kg ha−1 d−1 for 90 and 0 kg N ha−1, respectively. Reduction in seed yield caused by partial defoliation resulted primarily from removal of leaf blades rather than apical meristem removal. Defoliation did not affect seed germination or percentages of total viable seed. We conclude that spring top‐grazing of switchgrass would substantially reduce seed yields.
Root Growth of Winter Wheat under Elevated Carbon Dioxide and Drought
Authors: Chaudhuri U. N. , Kirkham M. B. , Kanemasu E. T.
Published: July 2010

With the atmospheric concentration of CO2 increasing, it is important to know how this will affect crop growth. The objective of this study was to determine the effect of enriched CO2 on root growth of winter wheat (Triticum aestivum L. ‘Newton’) under both wellwatered and dry conditions. The wheat was grown for 3 yr in 16 plastic chambers (121 by 92 by 168 cm) in the field under ambient CO2 (340 μL L−1) and elevated levels of CO2 (485, 660, and 825 μL L−1). Each chamber was placed over an underground box (77 by 37 cm at the top; 180 cm deep) containing a Muir silt loam (fine‐silly, mixed, mesic Cumulic Haplustoll). The boxes could be pulled out of the ground for observation of roots. Half of the boxes were maintained at field capacity (0.38 m−3 m−3) (well‐watered or not stressed plants) and half between 0.14 to 0.25 m3 m 3 (drought‐stressed plants). At harvest, root dry weights at different depths and stem dry weight were determined. Roots of plants grown under the three elevated levels of CO2 penetrated to the maximum depth of observation (176 cm) before roots of plants grown under the ambient level. At harvest, the difference in root growth between elevated and ambient levels of CO2 was most pronounced at the top level (0‐ to 10‐cm depth). Roots of drought‐stressed plants grown with 825 μL L−1 CO2 had a greater dry weight than roots of well‐watered plants grown with ambient CO2. The ratio of root to stem weight usually showed no trend (neither increase or decrease) with increasing CO2 concentration. Total dry weight at harvest of well‐watered root grown at ambient CO2 (3‐yr mean: 118 g m−2) was similar to that of drought‐stressed roots grown at the highest level of CO2 (3‐yr mean: 123 g m−2). The results indicated that high CO2 (825 μL L−1) can compensate for restrictions in root growth by drought.
Performance and Adverse Response of Sheep During Grazing of Four Legumes
Authors: Marten G. C. , Jordan R. M. , Ristau E. A.
Published: July 2010

Heifers (Bos taurus) may exhibit severe photosensitization and low gains when they consume ‘Monarch’ cicer milkvetch (Astragalus deer L.). We wanted to determine whether grazing lambs (Ovis aries) also would display these problems when they consumed Monarch cicer milkvetch compared to ‘120’ alfalfa (Medicago sativa L.), ‘Norcen’ birdsfoot trefoil (Lotus corniculatus L.), or ‘Arlington’ red clover (Trifolium pratense L.). A controlled, light grazing pressure (5 to 6% of body weight in leaf‐plus‐flower tissue dry matter per day) was used in pastures that had a Waukegan silt loam (flne‐silty over sandy, mixed, mesic Typic Hapludoll) soil. Lambs confined to the least palatable legume (cicer milkvetch) gained as well as or better than those confined to each of the other three species, even though animals often exhibited photosensitization exclusively on cicer milkvetch. Mean average daily gains during the 3 yr were 215, 228, 217, and 224 g Iamb‐' for alfalfa, birdsfoot trefoil, red clover, and cicer milkvetch, respectively. Even though red clover was leafier and had superior digestibility of stems and total forage, it usually did not promote different animal gains. Bloat of lambs occurred infrequently and only on alfalfa. Lamb product per hectare was influenced more by legume carrying capacity than by daily gains. The first‐year carrying capacity advantage of red clover progressively declined until it was lowest during the third year. We conclude that legume nutritive value variation had no consistent significance for lamb performance, and that earlier intake and gain problems by cattle that grazed cicer milkvetch were not repeatable with lambs. The excellent long‐term pasture persistence, carrying capacity, nutritive value, and lamb gains attributable to cicer milkvetch indicate that more research and breeding improvement are merited with this species even though it can cause photosensitization. Poorer persistence, but excellent initial carrying capacity, nutritive value, and lamb gains from red clover and birdsfoot trefoil indicate that breeding specifically to develop longer stand life would greatly enhance their pasture potential.
Engineering of Herbicide‐Resistant Alfalfa and Evaluation under Field Conditions
Authors: D'Halluin Kathleen , Botterman Johan , De Greef Willy
Published: July 2010

The recent development of gene transfer systems for higher plants and progress in identifying genes encoding important agronomic traits have opened new possibilities for improvement of crop species. Our objectives were to establish a transformation procedure for alfalfa (Medicago saliva L.) line RA‐3 using Agrobacterium‐mediated T‐DNA transfer on stem and petiole discs, compare the applicability of three selectable marker genes, and introduce a trait conferring resistance to a broad‐spectrum herbicide. Fifty‐nine transgenic lines carrying the bialaphos resistance gene bar encoding resistance to the herbicide glufosinate‐ammonium [ammonium‐DL‐homoalanin‐4‐yl (methyl) phosphinate] were analyzed under greenhouse and field conditions. The plants expressing bar under control of the cauliflower mosaic virus CaM V35S promoter showed the highest levels of resistance, whereas plants carrying bar under control of the TDNA TR2' promoter generally exhibited only a tolerance under field conditions. Our data clearly demonstrate the necessity of combining molecular analysis and field evaluation of individual transgenic lines.
Inheritance of Striga Resistance in Cowpea Genotype B301
Authors: Singh B. B. , Emechebe A. M.
Published: July 2010

The parasitic weed, Striga gesnerioides (Willd.) Vatke, is a major constraint in cowpea [Vigna unguiculata (L.) Walp.] production semi‐arid regions of sub‐Sahara Africa. Several sources of resistance have been identified. Of these, B301 has shown complete resistance to Striga across several countries. This study was undertaken to elucidate the genetics of Striga resistance in this line so that it can be effectively used in breeding programs. It was crossed to a susceptible cultivar, IT84S‐2246‐4. Parental, F1, F2, and backcross seeds were screened for Striga infection using pot‐culture technique. Roots of each plant were washed free of soil and examined for Striga attachment. All 52 plants of B301 were completely free from Striga, whereas all 50 plants of IT84S‐2246‐4 were infected. All the 13 F1 plants and 47 backcross F1 plants involving B301 were also completely free. The backcross Ft plants involving IT84S‐2246‐4 segregated into.15 resistant: 14 susceptible ratio, whereas the F: plants segregated into 142 resistant and 47 susceptible, giving a close fit to 1:1 and 3:1 ratios, respectively. These data indicate a monogenic dominant inheritance for resistance to Striga in cowpea for which the gene symbol Rsg (resistance to S. gesnerioides) is assigned.
Wheat High Temperature Tolerance during Reproductive Growth. I. Evaluation by Chlorophyll Fluorescence
Authors: Moffatt J. M. , Sears R. G. , Paulsen G. M.
Published: July 2010

Photosynthesis is highly sensitive to high temperature stress, an important problem in many regions during reproductive growth of wheat (Triticum aestivum L.). Our objective was to evaluate chlorophyll fluorescence, which indirectly measures photosynthetic efficiency, as a screening criterion for high temperature tolerance in wheat. Six genotypes differing in adaptation to the southern Great Plains were tested in two controlled environments and in the field. Plants in controlled environments were subjected to 37/25 °C and 25/20 °C day/night regimes during grain filling and at different developmental stages from late boot to 10 d after anthesis. The field experiment was planted during late winter to increase the probability of high temperature stress after anthesis. Initial (Fo), variable (Fv), and maximum fluorescence (Fm) were measured using a portable fluorometer on flag leaves of intact plants. Fluorescence parameters differed significantly among genotypes in controlled environments and field conditions. Relative stability of Fv was positively related to yield when high temperature treatment was applied to all genotypes after anthesis. The Fv and grain yield were negatively correlated in controlled environments but positively and not significantly correlated in the field. Genotypes in the high Fv group were also in the high yield group. Chlorophyll fluorescence, especially Fv, may be a useful tool for screening wheat of similar maturity for high temperature tolerance during reproductive growth, but the technique should be used with other criteria that might indicate resistance to stress.
Near‐Isogenic Lines of Wheat Carrying Genes for Stem Rust Resistance
Authors: Knott D. R.
Published: July 2010

Near‐isogenic lines (NILs) of wheat (Triticum aestivum L.) cartying single genes for resistance to stem rust (Puccinia graminis f. sp. tritici Eriks. & Henn.) are useful in genetical, plant pathological, and physiological studies. A stem rust susceptible, day‐length insensitive genotype was developed for use as a recurrent parent in the production of NILs. Thirty‐eight NILs were produced and tested with nine races of stem rust. Nineteen of the NILs carried numbered Sr (stem rust resistance) genes at identified loci, while 19 carried genes at loci whose relationship to the identified loci was not known. Of the latter group, seven genes appeared to be different from any of the numbered genes. The remaining 12 NILs either were shown to carry numbered genes or still were incompletely tested. Seven of the NILs were resistant to all nine stem rust races, and all but one carried a gene that had been transferred to wheat from a relative.
Potential Contributions of Five Exotic Maize Populations to Sweet Corn Improvement
Authors: Tracy W. F.
Published: July 2010

Sweet corn (Zea mays L.) is deficient in a number of agronomic traits such as stalk and root quality. Table quality (flavor, tenderness, texture, and appearance) is of prime importance in sweet corn improvement. A possible source of both improved agronomic performance and table quality is exotic cultivars of maize that have been developed for direct human consumption. The purpose of this study was to evaluate the potential contributions of five populations: NTZ Mexican Dent, NTZ Cateto, NTZ Caribbean Flint, NTZ Cuzco, and NTZ Coroico to sweet corn improvement. The five populations were crossed to nine sweet corn inbreds adapted to Wisconsin. The 45 resulting topcrosses and appropriate checks were grown at three locations in 1986 and 1987. Fifteen traits were evaluated including yield, stalk breakage, root lodging, and ear appearance factors. All traits varied significantly due to population and inbred effects. The population by inbred interaction effects were significant for growing degree days (GDD) to midsilk, plant height, root lodging, ear moisture, yield, kernel depth and width, ear length and width, and number of kernel rows. Mexican Dent topcrosses were the highest yielding, averaging 7.59 Mg ha−1. The lowest yielding topcrosses were those with Coroico as a parent, averaging 5.43 Mg ha−1. Compared to the sweet corn checks, the exotic populations contributed little to decreased stalk lodging or root lodging. The Mexican Dent population contributed the most positive and least negative effects followed by Caribbean Flint and Cateto. Coroico and Cuzco had little to offer in terms of plant and ear appearance.
Gas Exchange Rate and Yield Responses of Virginia‐type Peanut to Carbon Dioxide Enrichment
Authors: Chen J. J. , Sung J. M.
Published: July 2010

Poor seed fill and resultant seed‐coat shriveling occur commonly on Virginia‐type peanut (Arachis hypogaea L.) grown in Taiwan. The phenomenon may be linked to the limitation in photosynthate supply at seed filling. The objective of this study was to evaluate the effect of CO2 enrichment (1000 μL CO2 L−1) and depegging on CO2 exchange rate (CER) and yield responses of pot‐grown Virginia‐type peanut. Carbon dioxide enrichments were applied to the plants at pod filling. Depegging effect was examined contrasting the controls and the plants maintaining 38 to 40 pegs throughout the growing period. The results indicated that short‐term CO2 enrichment (CO2 treatment for 10 d) improved leaf and canopy CER. Long‐term CO2 enrichment (CO2 treatments throughout pod filling) tended to ease leaf ribulose 1,5‐bisphosphate carboxylase/oxygenase (rubisco) and chlorophyll (chl) deteriorations. Electrophoresis patterns of leaf soluble protein extracts confirmed this finding. Seed yield per plant was increased with high CO2 treatment applied at seed‐filling period, but the production of marketable seeds was improved only in the plants receiving CO2 and depegging treatments. The poor seed‐fill characteristic observed in Virginia‐type peanut is attributed to excessive sink load and low canopy CER.
Interspecific Trifolium Hybrids Produced by Embryo and Ovule Culture
Authors: Ferguson N. H. , Rupert E. A. , Evans P. T.
Published: July 2010

White or ladino clover (Trifolium repens L.) is an important forage or legume worldwide. However, lack of drought tolerance and disease resistance limit its usefulness. Although other Trifolium species express these traits, routine crossing to develop interspecific hybrids and introduce desirable traits has achieved limited success. The objective of this work was to culture embryos and ovules to rescue hybrids and regenerate plants in new interspecific hybrid combinations. A media regime is described that is generally useful with Trifolium hybrid embryos at the torpedo stage or later. Novel interspecific combinations include T. ambiguum Bieb. with T. montanum L. and T. occidental Coombe; T. isthmocarpum Brot. with T. repens and T. nigrescens Viv.; a trihybrid, designated RUO, of T. repens, T. uniflorum L., and T. occidentale with hexaploid T. ambiguum. The RUO‐T. ambiguum hybrid was produced in several genotypic combinations, one of which bloomed and yielded viable pollen. Interspecific hybridization in Trifolium offers a route to enhancement of forage germplasm by introducing traits that increase longevity while maintaining the superior forage quality of T. repens.
Viability of Acremonium coenophialum in Tall Fescue Seed after Ionizing Radiation Treatments
Authors: Bagegni A. M. , Sleper D. A. , Kerr H. D. , Morris J. S.
Published: July 2010

Planting tall fescue (Festuca arundinacea Schreb.) seed free of the endophyte Acremonium coenophialum Morgan‐Jones & Gains allows establishment of swards free of the fungus. Eradication of the fungal endophyte from infected tall fescoe seeds containing 130 g kg−1 moisture using ionizing radiation was investigated. Three sources of radiation were used: gamma rays (60Co source), neutron particles (252Cf source), and a thermal neutron beam. The percent germination of tall fescue seeds among gamma doses did not differ significantly (P < 0.05) from the control treatment and did not show a significant negative response (R2 = 0.41) to increasing levels of gamma radiation. At 250 Gy of gamma radiation, percent germination after 14 d was still =90%. Percent seed germination of tall fescue and high levels of radiation were negatively correlated for both sources of neutrons. Gamma radiation was shown to reduce (P < 0.01) the percent of the viable endophyte to =10% of control. The 2s2Cf and thermal neutrons reduced the percent of tall fescue infected by the endophyte to =30% without deleterious effects on seed germination.
Embryo Rescue through in Ovulo Culture in Helianthus
Authors: Espinasse Anne , Volin John , Dybing C. Dean , Lay Charles
Published: July 2010

In vitro rescuing of interspecific embryos between sunflower (Helianthus annuus L.) and other Helianthus species has been limited by the inability to culture embryos less developed than the vascular stage. The objective of this research was to develop a technique for rescuing ✕ Helianthus embryos at an earlier growth stage. This objective was achieved by culturing the embryos for 1 wk in ovulo on artificial agar media. During that culture period, 51 to 84% of the embryos from five sunflower genotypes developed to the vascular stage like in vivo sib‐embryos of the same age left as checks on greenhouse plants. Survival and development of sunflower embryos grown in ovulo were not affected by the salt composition of the four media tested (B5, B5S, MS and NN), or benefited by high sucrose levels (90 or 120g L−1). The technique of in ovulo culture resulted in rescuing 52% of H. annuus ✕ H. maximiliani Schrad. hybrid embryos. This indicates that sunflower ovules cultured on standard media fulfilled the requirements of Helianthus hybrid embryos at an early stage of development. After excision from the ovule and subsequent culturing for 2 wk on fresh media with the same composition, 40 to 60% of H. annuus embryos and 25% of H. annuus ✕ H. maximiliani hybrid embryos germinated into plantlets. Six H. annuus ✕ H. maximiliani plantlets survived transfer to the greenhouse and grew into flowering plants that exhibited traits from both parents. These are the first reported hybrid plants between H. annuus and H. maximiliani using sunflower as the female parent.
Chloride and Sulfate Salinity Effects on Selenium Accumulation by Tall Fescue
Authors: Wu Lin , Huang Zhang‐Zhi
Published: July 2010

The discovery of high levels of Se in soil and water samples from the San Joaquin Valley, California, and of its responsibility for deformity and death of wildlife at Kesterson National Wildlife Refuge have renewed interest in the bioaccumulation of this element. Greenhouse nutrient solution culture and field experiments were conducted to examine the effects of Cl and SO4 salt on growth and Se accumulation in tall fescue (Festuca arundinacea Schreb.) cultivars Alta, Falcon, and Olympic. Sulfate salt substantially reduced growth inhibition and Se accumulation. Tall fescue from the field irrigated with water low in salinity had higher tissue Se concentration than plants from the field irrigated with water high in salinity. No difference in tissue Se concentration was found among the three tall fescue cultivars; however, forage‐type Alta produced the most shoot biomass and accumulated the most total Se. The soil irrigated with water high in salinity had 10 times higher Se concentration thansoil irrigated with water low in salinity. The highest soil Se concentration was found in the top 15 cm of soil. Growing fescue for one year reduced soil Se by 50%. Selenium concentrations below 15‐cm depth were lower and similar between the bare soil and the soil under tall fescue. Both the high and low salinity water irrigations did not cause high levels of Se accumulation by the tall fescue cultivars unless there was continual addition of Se into the system. This study generated important information for Se bioaccumulation management in soils with elevated salinity and Se levels.
Physiological Basis of Genetic Improvement of Maize Hybrids in Ontario from 1959 to 1988
Authors: Tollenaar M.
Published: July 2010

Genetic improvement in grain yield of North American maize (Zea mays L.) hybrids during the past three to five decades can be attributed to increased phytomass production. The objective of this study was to identify the physiological traits that have contributed to the improvement in dry matter production of maize hybrids in Ontario. Experiments were conducted during 1987 and 1988 at two locations in Ontario with nine maize hybrids representing three decades of yield improvement in Ontario. Hybrids were grown at 2, 4, 8, and 13 plants m‒2 and phenological development was studied from planting to maturity. Phenological development differed very little between old and new hybrids. Rates of leaf appearance, days from planting to silking and from silking lto maturity, and kernel moisture loss during the grain‐filling period did not show a consistent trend with year of release of the hybrid. The interval from tassel to silk emergence, however, tended to be shorter for new than for old hybrids. Differences in rate of dry matter accumulation among hybrids were largest at late stages of development (3 wk post silking to maturity). Effects of plant density and hybrid on leaf senescence and loss of stover weight from 3 wk post silking to maturity were additive, with older hybrids and higher plant densities showing greater losses of stover weight and higher rates of leaf senescence. The improvement in dry matter accumulation from old to new hybrids may be attributable, in part, to increased tolerance of high plant density.