bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Photosynthate Source‐Sink Manipulation on Dinitrogen Fixation of Male‐Fertile and Male‐Sterile Soybean Isolines1
Authors: Riggle B. D. , Wiebold W. J. , Kenworthy W. J.
Published: July 2010

The effect of carbohydrate availability upon nodule activity was studied using male‐sterile (ms2 ms2) and male‐fertile (Ms2 Ms2) soybean (Glycine max L. Merr.) isolines. At 63 days after emergence (DAE), treatments intended to increase or decrease the supply of carbohydrate to nodules were imposed. Treatments were: control, partial shading, partial defoliation, and partial depodding. At 70 DAE, partial sha,ding decreased photosynthetic photon flux density 75%, partial defoliation decreased leaf dry weight 60%, and depodding reduced pod dry weight 40 to 87%. Specific nodule activity (SNA) was determined during seed‐filling using acetylene reduction assay. Specific nodule activity of both isolines changed very little until 83 DAE, then declined rapidly during the next 14 days as male‐fertile plants approached physiological maturity. Control male‐fertile and male‐sterile plants had similar SNA until 83 DAE when SNA of sterile plants was greater than SNA of male‐fertile plants. Treatments intended to decrease the supply of carbohydrate to nodules decreased SNA throughout seed‐filling. Depodding increased SNA of male‐fertile plants, but decreased SNA of male‐sterile plants at 83 DAE. Depodding increased total root N concentration. Other treatments did not affect root N concentration. Control male‐sterile plants had higher total root N concentrations than control male‐fertile plants. On most dates, concentrations of starch and total soluble sugars were greater within roots of control male‐sterile plants than within roots of control male‐fertile plants. At 70 DAE, partial shading and partial defoliation of male‐fertile plants resulted in decreased root soluble sugars but had no affect on root starch concentration. Depodding increased the concentration of starch and total soluble sugars within roots of both isolines 77 and 83 DAE. Treatment and isoline effects on SNA were not consistently related to treatment effects on root carbohydrate concentration. Male‐sterility and depodding treatments which decreased the reproductive sink for carbohydrate also decreased the reproductive sink for newly reduced N. Data indicate that factors other than carbohydrate availability may be responsible for the decline in SNA during late seedfilling.
Growth Analysis Based on Degree Days1
Authors: Russelle M. P. , Wilhelm W. W. , Olson R. A. , Power J. F.
Published: July 2010

Comparisons of growth analysis functions within and among experiments are often confounded by sources of variation other than those imposed by treatment. We suggest use of a temperature index, such as modified growing degree days, as the divisor in growth functions to facilitate treatment comparisons within certain experiments and to reduce the effects of differing temperature regimes among experiments on these comparisons. Three experiments were identified to provide data to analyze this new approach. Mean absolute growth rate () and mean relative growth rate () were compared in two experiments with maize (Zea mays L.) conducted in eastern Nebraska. Previously published values of and mean net assimilation rate () of barley (Hordeura vulgare L.) grown under controlled environments in a soil temperature and P fertility study were also evaluated. Use of modified growing degree days, rather than days, as the divisor in these growth functions led to the recognition of physiological differences due to or associated with treatment, which were previously masked by normal crop response to temperature, and clarified other treatment differences by reducing the effect of temperature.
Effects of Two Maize Endosperm Mutants on Kernel Maturity, Carbohydrates, and Germination1
Authors: Churchill G. A. , Andrew R. H.
Published: July 2010

The shrunken‐2 (sh2) and sugary enhancer (se) genes which modify endosperm carbohydrates in maize (Zea mays L.) show promise as a means of improving quality for human consumption. A major factor limiting their use is the associated low germination of the seed and low seedling vigor. This research was undertaken to measure germination of sh2 and se hybrids as compared to their respective standard counterparts, Sh2 and Se, when seed was harvested at successive stages of maturity, and to examine germination differences as related to corresponding carbohydrate fractions. Hybrids were hand pollinated on the same day, and ears were harvested at approximately weekly intervals on six successive dates beginning 32 days after pollination. Kernel weight, moisture, reducing sugars (RS), total sugars (TS), water soluble polysaccharides (WSP), total soluble carbohydrates (TSC), water insoluble polysaccharides (WlP), tal non‐structural carbohydrates (TNC), cold and warm temperature germination, and seedling vigor were determined for seed at each harvest. Although the sh2 gene markedly increased kernel sugars and reduced kernel weight, seed of the hybrid, sh2 (2 ✕ 3), had satisfactory cold.temperature germination when harvested after mid‐September, when its moisture content was approximately 50%. Seed of the hybrid, se (8 ✕ 10), also higher in sugar than its standard counterpart, germinated satisfactorily at cold‐temperature when harvested at a moisture content of 60%. Cold‐temperature germination was negatively associated with kernel moisture, RS, TS, WSP, TSC, and TNC and positively associated with WlP. It usually was not significantly related to kernel weight. Root, shoot, and total seedling length were positively correlated with cold temperature germination. These results indicate that germination at low temperatures simulating those in the field can often be satisfactory for hybrids carrying the sh2 or se genes.
Response of Six Rice Callus Cultures to Deep‐Frozen Temperatures1,3
Authors: Ulrich J. M. , Finkle B. J. , Mackey B. E. , Schaeffer G. W. , Sharpe Frank
Published: July 2010

Callus cultures of five mutants of rice (Oryza sativa L.), which could grow in the presence of the synthetic analog of lysine, S‐aminoethyl‐L‐cysteine, and the nonmutant strain from which the mutants were derived were studied for growth response after freezing at several temperatures. Although the mutant lines were derived from a single line, variations were noted in response to the mixture of cryoprotectants added [10% polyethylene glycol, 8% glucose, 10% dimethylsulfoxide (PGD) in H2O, w/v] and freezing treatments. Following freezing (and subsequent thawing), growth of callus was less at lower freezing temperatures; but all cultures grew even after freezing at —196°C. After the —196°C treatment, three lines increased three to four times the initial inoculum weight after 6‐, 8‐, and 10‐week growth periods, compared to an increase of 14 times in 4 weeks for the cell line which grew most rapidly after thawing. Because all rice lines survived a brief period at —196°C and two lines tested, later survived —196°C for more than a year, the possibility exists for long‐term, deep‐frozen preservation of rice callus cultures.
Comparison of Grain Yield of Uniblends and Biblends of 10 Spring Barley Cultivars1
Authors: Baker R. J. , Briggs K. G.
Published: July 2010

Pure strands (uniblends) of 10 cultivars of spring barley (Hordeum vulgare L.) and the 45 possible 50:50 mixtures (biblends) were evaluated for 3 years in four‐replicate randomized blocks. In addition to plot grain yield, data were collected on grain weight, shoot weight, and harvest index from 20 plants (10 in 1977) sampled from each uniblend and from 10 plants of each of the components of each of the biblends. Single plant sampling was carried out in only two replicates in each year. Cultivar identification in the biblend samples was facilitated by evaluation of spike and seed characteristics of each plant. Analyses of whole plot yield and of single plant data indicated that there were no significant differences between average performances in uniblends and biblends. Absence of significant interaction implied that relative cultivar performance in uniblends and biblends was the same. These results suggest that intergenotypic competition among relatively well adapted genotypes should not be of serious consequence in barley breeding programs.
Symbiotic Interactions between Strains of Rhizobium phaseoli and Cultivars of Phaseolus vulgaris L.1
Authors: Pacovsky R. S. , Bayne H. G. , Bethlenfalvay G. J.
Published: July 2010

Several cultivar‐strain combinations of the Phaseolus vulgaris L.‐Rhizobium phaseoli association were evaluated for N2 fixation, N assimilation, and primary (biomass) production. Plants were grown in a greenhouse. Nitrogen fixation rates were estimated from H2‐ and C2H4‐production data. The relative efficiency of N2 fixation was less than 0.60 indicating a loss of reducing power to H2 evolution. Copious production of H2 by all effective strains used in this study suggests that energy losses through H2 evolution may limit the productivity of the Phaseolus‐Rhizobium symbiosis. Assimilation of N by the symbiotic association in response to N2 fixation was influenced by both strain and cultivar effects. Analysis of variance showed significant differences due to both symbionts in most growth parameters measured. However, there was no significant correlation (P < 0.05) between N assimilation and the estimated rates of N2 fixation in the various effective host‐endophyte combinations. Assimilated N is a better, more direct measure of symbiotic efficiency than the estimate of N2‐fixation rate by C2H4 and H2 production, and the merits of different growth parameters as measures of symbiotic effectiveness are compared and discussed.
Insect Resistance Factor in Soybean PI's 229358 and 227687 Demonstrated by Grafting1
Authors: Lambert Lavone , Kilen T. C.
Published: July 2010

Soybean [Glycine max (L.) Merr.] plant introductions (PI) 229358 and 227687 have been reported to be resistant and the cultivar Davis to be susceptible to foliar‐feeding by corn earworm, Heliothis zea (Boddie). A bioassay technique utilizing expanding leaves from non‐grafted and reciprocally‐grafted Davis, PI 229358, and PI 227687 plants was used to determine if resistance or susceptibility is conditioned by translocated factors. Corn earworm larvae reared on leaves from non‐grafted Davis plants were significantly (P = 0.01) larger on Day 16 than larvae reared on leaves from Davis scions or stocks of reciprocallygrafted plants. Larvae reared on leaves from non‐grafted PI plants were significantly (P = 0.01) smaller than larvae reared on leaves from non‐grafted Davis plants, but were not significantly smaller than larvae reared on leaves from PI scions or stocks of reciprocally‐grafted plants. Thus, a resistance factor which is translocated throughout the leaves is indicated for PI 229358 and PI 227687. Translocatable factors which condition susceptibility were not indicated.
A New Chromosone Number for the Genus Medicago1
Authors: Bauchan G. R. , Elgin J. H.
Published: July 2010

Seventy‐two accessions of Medicago scutellata (L.) Mill. and 37 accessions of M. rugosa Desr. were screened to determine if diploid forms of these species exist and to observe the morphological variation within the two species. Diploid plants are desirable for crossing with both the diploid and tetraploid forms of M. sativa L. (alfalfa). The somatic chromosome number of 2n–30 was observed in all accessions of M. scutellata and M. rugosa, and no diploid forms were found. Both species contain satellited chromosomes (SAT‐chromosomes), M. scutellata has two pairs of SAT‐chromosomes and M. rugosa has one pair. The satellites are large and they are located a relatively long distance from the main body of the chromosome, possibly leading to the erroneous chromosome counts of 2n = 32 recorded previously. Meiosis was regular in the microspore mother cells of both species with 15 bivalents forming at metaphase I. On the basis of intraspecific variation, plants of M. scutellata could be separated into three morphological groups: 1) nonvigorous plants that flower approximately 1 month after planting and have one flower per inflorescence, 2) vigorous plants that flower 2 months after planting and have three flowers per inflorescence, and 3) an intermediate group. The way in which these 2n=30 species may have evolved and their potential value in a breeding program are suggested.
Hypocotyl Pigments in Soybeans1
Authors: Peters D. W. , Wilcox J. R. , Vorst J. J. , Nielsen N. C.
Published: July 2010

Seedlings of 23 soybean (Glycine max L. Merr.) cultivars and experimental lines that had purple, bronze, or white hypocotyl color were examined to determine pigmentation differences, as well as to isolate and identify the responsible compound(s). Spectral examination of methanolic extracts of fresh hypocotyls revealed significant differences in the 480 to 580 nm region. The purple and bronze hypocotyl types exhibited major absorption peaks at 535 and 530 nm, respectively, but the white hypocotyl types did not. Pigment content of the purple hypocotyl lines ranged from 34 509A1535 nm/g fresh weight to 17 956 A1535 nm/g fresh weight and exhibited a gradation between the extremes. Bronze hypocotyl lines showed a similar gradation in a range of 7708 A1530 nm/g fresh weight to 4407 A1530 nm/g fresh weight. High pressure liquid chromatographic (HPLC) analysis of the methanolic extracts revealed an anthocyanin form of three major anthocyanidins: delphinidin, petunidin, and malvidin. Malvidin was predominant both in pruple and bronze hypocotyl types, but there was five‐fold more present in purple hypocotyls compared with bronze ones. It was concluded that the bronze hypocotyl types may be dilute‐purple, representing the lower end in a continuum among soybean cultivars in their anthocyanin content.
Evaluation of Methods Used in Testing Winter Wheat Susceptibility to Preharvest Sprouting1
Authors: Hagemann M. G. , Ciha A. J.
Published: July 2010

Rains after wheat (Triticum aestivum L.) is physiologically ripe can cause preharvest sprouting which can lower the baking quality of flour due to de novo synthesis of alpha‐amylase. A fast, repeatable method is needed by plant breeders to screen wheat lines for their susceptibility to preharvest sprouting. In this study, three winter wheat cultivars varying in susceptibility to preharvest sprouting were grown in six different environments within the Pacific Northwest and were used to evaluate four germination and three enzymatic tests that measure sprouting susceptibility. Germination tests were performed with intact spikes and threshed seeds at four temperatures (15, 20, 25, and 30°C). Enzymatic tests were performed using flour milled from seeds that had been germinated at 15°C. The evaluation was based on 15 parameters of sprouting measured in the various tests. For a sprouting parameter to be considered a useful indicator of sprouting susceptibility it had to show significant (P < 0.05) differences in both cultivar and environmental effects at a given germination temperature, and its coefficient of variation had to be low. A germination test using intact spikes rolled in paper towels and one using threshed seeds in petri dishes at 20°C were the only tests that yielded parameters meeting the required criteria. Although disadvantages and advantages are associated with each of the parameters examined, germination tests were better in predicting sprouting susceptibility whereas enzymatic tests were better in quantifying actual sprout damage.
Partial Growth Analysis of Soybeans Stressed by Simulated Green Cloverworm Defoliation and Velvetleaf Competition1
Authors: Higgins R. A. , Pedigo L. P. , Staniforth D. W. , Anderson I. C.
Published: July 2010

Dry weight accumulation and allocation by soybean [Glycine max (L.) Merr. ‘Amsoy 71’] under selected combinations of competition with velvetleaf [Abutilon theophrasti (Medic.)] and simulated defoliation by the green cloverworm [GCW, Plathypena scabra (F.)] were evaluated with traditional growth analysis techniques in a 2‐year field study. Discernible effects of weed‐stress were restricted to soybeans grown in weed‐proximate locations for 42 days or more after emergence. In general, weed‐proximate soybeans stressed season‐long by velvetleaf exhibited smaller dry weights, mean crop growth rates (CGR), and mean relative growth rates (RGR) than those in plots where velvetleaf competition was terminated within 5.5 weeks of emergence. In. cremental defoliation, equivalent in phenology and intensity to 120 GCW larvae/m of row did not substantially influence reproductive dry weights or reproductive growth rates within 75 days of soybean emergence. However, leaf and stem components were sometimes reduced within this period. Velvetleaf competition and simulated GCW defoliation did not interact significantly in this study.
Influence of Drought Stress on Genetic Variances of Alfalfa and Wheatgrass Seedlings1
Authors: Rumbaugh M. D. , Asay K. H. , Johnson D. A.
Published: July 2010

Sprinkler irrigation gradient systems may be useful for screening plant populations for drought resistance. To be effective, traits chosen as measures of drought resistance must be heritable throughout the range of stress environments represented by the moisture gradient. Line source gradient techniques were used to evaluate the potential of these techniques in screening two forage crops for seedling drought resistance and to examine the effect of irrigation gradients on important genetic parameters. Stand densities and/or shoot dry weights were measured on populations and progenies of alfalfa (Medicago sativa L.) and a wheatgrass hybrid [Elytrigia repens (L.) Nevski ✕ E.spicata (Pursh) D.R. Dewey] grown in five experiments under greenhouse and field irrigation gradient systems. The means, genetic variances, broad sense heritabilities, and predicted genetic gains due to selection declined as the amount of supplemental water was reduced. Most of the phenotypic variance observed in the drier sections of the plots was environmental in origin. When water application gradient systems are used in breeding for drought resistance, the target environments must be carefully delimited. Gains due to selection may be more rapid if selection is made at intermediate rather than at extreme levels of drought stress.
Influence of Elevated CO2 on Growth of Soybean Plants1
Authors: Rogers Hugo H. , Cure Jennifer D. , Thomas Judith F. , Smith Joy M.
Published: July 2010

Continuing use of fossil fuels in industrialized countries has created a need to understand growth responses of major crop species to elevated concentrations of CO2. An analysis was therefore undertaken of the growth of soybeans [Glycine max (L.) Merr. ‘Bragg’] grown in pots in open top field chambers at six CO2 concentrations ranging from 332 μL L‐1 (ambient) to 910 μL L‐1. Major growth response occurred with the first increments of added CO2 with a maximum 66% increase in total vegetative dry matter at the 910 μL L‐1 CO2 level. Dry weight increases were proportionate among vegetative plant parts, although the harvest index was found to decrease slightly. Greater absolute growth rates in elevated CO2 treatments were associated with greater rates of branch and internode elongation, leaf initiation, and leaf expansion. Yield increases represented greater seed numbers per plant rather than larger seeds. Percentage protein of seed decreased with CO2 enrichment. In the interval from day 5 to 2 weeks after planting, mean relative growth rate (RGR) increased asymptotically with CO2 concentration. Of the two components of RGR, the mean net assimilation rate (NAR) increased dramatically and mean leaf area ratio (LAR) decreased. In the intervals from week 2 to 7 and from week 7 to 12, RGR became constant across CO2 treatments as the positive response of NAR and the negative response of LAR became less pronounced. Both RGR and NAR fell through the vegetative growth phase at each CO2 level. The adjustment in LAR resulted from a decrease in specific leaf area while leaf weight ratio remained unaffected by CO2.
Crossing and Morphological Relationships among Species Closely Related to Arrowleaf Clover1
Authors: Taylor N. L. , Giri N.
Published: July 2010

Isolation barriers were examined by making all possible crosses including reciprocals among arrowleaf clover (Trifolium vesiculosum Savi), T. mutabile Portenschl. and T. leiocalycinum Boiss. & Spruner. No evidence of sterility was indicated by cross seed set. All F1 cross seed germinated readily but yellow seedlings were produced by crosses of T. mutabile and T. leiocalycinum with T. vesiculosum. F1 plants from reciprocal crosses of these species were normal green. The yellow condition disappeared as plants matured. Most F1 plants from crosses between accessions produced less stainable pollen than plants from crosses within accessions. All species had 16 somatic chromosomes and chromosome associations at metaphase I of meiosis were similar for all parents and F1 progenies. We concluded that T. mutabile and T. leiocalycinum are quite closely related and are slightly differentiated from T. vesiculosum. Therefore, the three taxa must be isolated under field conditions to prevent crossing.
Changes in Grain Sorghum Stomatal and Photosynthetic Response to Moisture Stress across Growth Stages1
Authors: Garrity Dennis P. , Sullivan Charles Y. , Watts Darrell G.
Published: July 2010

The dynamics of stomatal response and canopy apparent photosynthesis in grain sorghum [Sorghum bicolor (L.) Moench] were studied throughout a growing season in relation to water stress. Treatments received irrigation weekly at 100% soil water deficit replacement or no irrigation on the extremes of a sprinkler irrigation gradient conducted on a fine sand (Typic Ustipsamment). Stomatal resistance was sensitive to small reductions in leaf water potential during the vegetative period. During the reproductive period the stomata became nearly insensitive to leaf water potential and remained open at low leaf water potentials. Maximum midday deficits in leaf water potential due to drought stress were in the range of 0.1 to 0.2 MPa during the vegetative period, 0.3 to 0.4 MPa during the reproductive period and exceeded 0.5 MPa during grain filling. Stored soil water was steadily depleted in the unirrigated treatment. Water stress reduced grain and dry matter yields 36 and 37% respectively. Photosynthesis per unit leaf area was not decreased by water stress during the reproductive and grain filling periods. The rate of canopy apparent photosynthesis was reduced by 14 to 26% but this was solely a result of less leaf area in the stressed treatment. Canopy evapotranspiration was greatly reduced in the water stressed treatment but evapotranspiration per unit leaf area was apparently unaffected by water stress during all or a large portion of the post‐vegetative period. Reduction in leaf area was an important mechanism for transpiration control under drought stress during the entire reproductive and grain filling periods. Stomatal resistance was not a major transpiration control mechanism. In the absence of increased stomatal resistance both transpiration and photosynthesis per unit leaf area were not reduced during the continually intensifying seasonal drought.
Photosynthesis Assimilate Partitioning in Closely Related Lines of Rice Exhibiting Different Sink:Source Relationships
Authors: Lafitte H. R. , Travis R. L.
Published: July 2010

Closely related rice (Oryza sativa L.) genotypes differing in sink to source ratios were evaluated for photosynthetic gas exchange characteristics, nonstructural carbohydrate content, leaf parameters, and yield components. Lines with a high sink to source ratio exhibited higher rates of carbon exchange per unit leaf area and accumulated lower amounts of nonstructural carbohydrates in vegetative storage tissues than did other lines. The line with the lowest sink to source ratio accumulated the most carbohydrates in storage tissues. The results suggest that the photosynthetic potential of rice was not fully realized, and that an increase in the sink to source ratio might result in higher yields. The low source lines had high specific leaf weights, however, and that factor may have been largely responsible for perceived increases in photosynthetic rates. When expressed on a unit leaf weight or unit leaf protein basis, low source lines did not necessarily exhibit high source activity. The results indicate that sink:source ratios can be altered genetically, and that such manipulations can affect plant yields.
Production of 2n Pollen in Red Clover1
Authors: Parrott W. A. , Smith R. R.
Published: July 2010

The success of tetraploid red clover (Trifolium pratense L.) in Europe has stimulated interest in developing tetraploid red clover adapted to the United States. The use of 2n gametes to produce tetraploid alfalfa (Medicago sativa L.) and potato (Solanum tuberosum L.) from diploid germplasm suggests that 2n gametes may be an alternative to chemical treatment. Diploid plants that produce 2n eggs are known to occur in red clover, and plants that produce 2n pollen have been reported. The objectives of this study were to search for red clover plants producing 2n pollen, and to determine the cytological origin of such pollen. Six hundred plants, belonging to six different diploid (2n = 2x = 14) cultivars, were screened for 2n pollen production by examining dry pollen samples with the aid of a microscope. Eighteen plants (3%) produced at least 1% 2n pollen and were classifted as 2n pollen producers. Individual plants ranged from 1 to 84% in frequency of 2n pollen production. Pollen mother cell analyses revealed that 2n pollen resulted from parallel or tripolar spindles during anaphase II of microsporogenesis. This mechanism is genetically equivalent to a first division restitution (FDR) mode of gamete formation. One 2n pollen producer proved to be a synaptic mutant. Normally, synaptic mutants are male sterile, but fertility is restored by parallel spindles in this plant. Because the lack of homologous pairing limits genetic recombination, this plant can produce gametes with the same genetic constitution as the sporophyte. It is apparent from the results that 2n gametes may be useful in red clover polyploidization programs.
Water Use Efficiency of Cassava. I. Effects of Air Humidity and Water Stress on Stomatal Conductance and Gas Exchange1
Authors: El‐Sharkaway Mabrouk A. , Cock James H.
Published: July 2010

Measurements of CO2 and H2O exchange of attached cassava (Manihot esculenta Crantz) leaves in water stressed and control plants of cultivars M Col 90 and M Col 88 were made at various leaf‐air vapor pressure differences (VPD) (0.8 to 4.5 kPa). Apparent photosynthesis and transpiration were sharply reduced by increase in VPD above 1.8 to 2.0 kPa in both stressed and nonstressed plants. This trend coincided with changes in leaf conductance over similar ranges of VPD. The rapid closure of stomata in dry air was independent of bulk leaf water potential (ψl). Furthermore, the response was completely reversible in humid air after short exposure to dry air, suggesting a direct response to changes in air humidity. Water use efficiency decreased as VPD increased over the range of 1 to 4 kPa. The significance of the Stomatal response to humidity is discussed in relation to WUE in long dry periods.
Water Efficiency of Cassava. II. Differing Sensitivity of Stomata to Air Humidity in Cassava and Other Warm‐Climate Species1
Authors: El‐Sharkawy Mabrouk A. , Cock James H. , Held K. Alexander A.
Published: July 2010

Measurements of CO2 and H20 exchange and the calculated leaf conductance of attached leaves in well‐watered plants were conducted over a range of leaf‐air vapor pressure differences (VPD) (1.0 to 4.0 kPa) to compare the response of cassava that of other warm‐climate species. Species tested were cassava (Manihot esculenta Crantz), andropogon (Andropogon gayanus Kunth), beans (Phaseolus vulgaris L.), siratro [Macroptilium atropurpureum (DC) urb], rice (Oryza sativa L.), eucalyptus (Eucalyptus deglupta Blume), amaranth weed (Amaranthus retroflexus L.) and grain sorghum [Sorghum bicolor (L) Moench]. Plants were grown in pots outdoors at the CIAT headquarters, Palmira, Colombia, South America. All except andropogon showed a decrease in leaf conductance with increase in VPD. The degree of stomatal sensitivity decreased as follows: cassava > siratro, amaranthus, eucalyptus, bean > sorghum, rice > andropogon. The greater sensitivity in cassava was associated with reduction in transpiration and stable leaf water potential (ψl) at large VPD. In other less sensitive species, transpiration increased and bulk leaf water potential decreased at large VPD. The response of cassava to changes in VPD resulted in higher water use efficiency (WUE = μmol CO2 uptake per mmol H2O loss) compared with other C3 species. This may contribute to the comparative advantage of cassava when grown under conditions of limited availability of water. The WUE of the C4 species (sorghum, andropogon, amaranthus) were higher than those of the C3 species. This greater WUE of C4 species was attributed mainly to the higher photosynthetic rates of the C4 species rather than to a lower transpiration rate.
Genotype and Genotype ✕ Environment Interaction Effects on Forage Yield and Quality of Crested Wheatgrasses1
Authors: Lamb J. F. S. , Vogel K. P. , Reece P. E.
Published: July 2010

Genotype, environment, and genotype ✕ environment interaction effects for forage yield and quality of the crested wheatgrasses (Agropyron cristatum) and (A. desertorum) were studied using an array of 42 crested wheatgrass introductions, experimental lines, and released cultivars that were selected to be representative of the mix of germplasm available to a breeder. They were grown in two environments, Lincoln and Alliance, Nebr., that differ markedly in climate. Forage yield and forage quality as measured by in vitro dry matter digestibility (IVDMD) and percent protein were determined in both locations in 1980 and 1981. In the combined analyses over years and locations, there were significant differences among strains or genotypes and locations for first‐harvest forage yield, IVDMD, and protein. Strain ✕ location interaction effects were significant only for first‐harvest forage yield and for this trait its variance component was only 0.3 as large as the variance component for strains. Strain ✕ year interaction effects were not significant. Spearmen correlations, used to show relative ranking of the strains at the two locations, were moderate and positive for all first‐cut traits. The results indicate that existing genetic variability in forage yield and quality should permit the development of improved crested wheatgrasses and that at least in the initial stages of a breeding program, selection for these traits could be done in a single location and year.
Diploid‐Tetraploid Comparisons in Rye. I. Forage Production1
Authors: Pfahler P. L. , Barnett R. D. , Luke H. H.
Published: July 2010

Autotetraploids differ from their diploid counterparts in many morphological, physiological, cytological, and ecological characteristics. The tetraploidy effect on the amount and environmental stability of rye (Secale cereale L.) forage production was examined in this study. Six populations consisting of three diploid (2x) cultivars (‘Florida Black’, ‘Gator’, ‘Explorer’) and their autotetraploid (4x) derivatives were grown in two late fall‐winter‐early spring forage seasons (1979–1980, 1980–1981) at Gainesville (29°40′ N Lat) and Quincy (30°35′ N Lat), Fla., at two seeding rates (0.5, and 1.0 viable seeds/linear cm of row). Forage weight was obtained at a total of 16 clipping dates among seasons and locations (Gainesville—four dates in both seasons, Quincy—three dates in 1979–1980 and five dates in 1980–1981). The direction and magnitude of the differences between the forage production of the 2x and corresponding 4x populations were not consistent and were influenced by genetic background (2x cultivar source) and clipping dates within season and location. Apparently, the tetraploid effect was altered by genetic factors and many interacting environmental forces. Significantly higher production from the higher seeding rate was obtained primarily at the earlier clipping dates within each season and location but seeding rate interactions with all genetic and environmental variables were not significant. No differences among populations in environmental stability were found.
Effects of Night Temperature on Dry Matter Partitioning and Seed Growth of Indeterminate Field‐Grown Soybean1
Authors: Seddigh Majid , Jolliff Gary D.
Published: July 2010

Dry matter allocation, and thus productivity, within soybean plants (Glycine max (L.) Merr.) is affected by night temperature. The indeterminate soybean cultivar S09‐90 of Maturity Group O was grown in the field at Oregon State University in 1981 and 1982 to assess the effect of night temperature on dry matter partitioning and seed growth through out the growing season. Mean minimum night temperature used as treatments included check (noncontrolled, ca. 10°C), 16, and 24°C. Night temperatures for 16 and 24°C treatments were raised by enclosing plots with polyethylene‐covered chambers at night and increasing chamber temperature with electric heaters. The chamber covers were removed each morning to provide natural field conditions during the daylight hours. Treatments were applied from 2 weeks after crop emergence until physiological maturity. Higher night temperatures enhanced early vegetative growth, advanced reproductive development and physiological maturity, and increased seed yield. Although higher night temperatures increased crop growth rate during the vegetative period, final vegetative dry matter, pod weight, and leaf area generally decreased as night temperature increased. Net assimilation rates were similar among the treatments. Seed growth duration (SGD) did not vary considerably among the treatments except for 24°C plants in 1982 whose SGD was 6 days longer than the check plants. Increased seed yield of the 16°C plants over the check was associated with 31 and 38% increases in seed growth rates (SGR) in 1981 and 1982, respectively. Seed growth rate of 24°C plants also was 24% higher than the check in 1981. Increased seed yield of 24°C plants in 1982 was primarily due to their longer SGD. Increased seed growth along with reduced vegetative growth and pod wall growth of plants at higher night temperatures resulted in higher harvest indices in these plants compared to the check. Harvest index was increased above the check by 27 and 33% in 1981 and 16 and 23% in 1982, for 16 and 24°C plants, respectively. These data support the conclusion that SGR of early maturing soybeans is responsive to night temperatures. Low night temperatures restrict SGR that, in turn, favors partitioning of photosynthates to vegetative organs and pod walls.
Inheritance of Seedling Resistance to Gray Mold in Kenaf1
Authors: Campbell T. A.
Published: July 2010

Gray mold, caused by Botrytis cinerea Pers. ex Fr., is a potentially serious disease of kenaf (Hibiscus cannabinus L.) which usually attacks in the fall under cool temperatures and high humidity and can cause loss of an entire stand under epiphytotic conditions. Previous data indicate that strains highly susceptible to gray mold in the greenhouse as 1‐week‐old seedlings would demonstrate some level of field susceptibility as mature plants. However, the resistant reactions in seedlings and mature plants are not strongly related. Inheritance of resistance to gray mold was studied in the laboratory in 1‐week‐old S1, F1, backcross, and F2 progenies tracing to three parents. Progenies were inoculated with Botrytis cinerea (300 000 spores/seeding), maintained in moisture‐saturated atmosphere at 15°C for 72 h, incubated for 2 weeks at 10°C, then evaluated. Data indicate that resistance was conditioned by two genes; the genotype R __s produced the resistant phenotype and R__S__, rrS__, and rrss the susceptible. It is hypothesized that resistance is conditioned by R and is completely dominant to susceptibility (r); however, S (completely dominant to s) supresses the expression of R. High penetrance and simple inheritance of the susceptible reaction indicates that the laboratory technique could be used effectively for early elimination of plants that would be susceptible in the field.
Histological Features of Anthers from Normal and ms3 Mutant Soybean1
Authors: Nakashima H. , Horner H. T. , Palmer R. G.
Published: July 2010

Anthers of male‐sterile mutant (ms3) and normal soybean [Glycine max (L.) Merr.] were compared by using a triple‐staining procedure for DNA, polysaccharides and proteins, and a single‐staining procedure for sporopollenin in conjunction with brightfield and fluorescent microscopy. The purpose of this study was to determine at what stage of anther development histological differences were detectable between male‐sterile (ms3) and normal soybean. At the tetrad stage, a prominent greenish‐blue material, visible with the triple‐staining procedure, filled some of the enlarged tapetal cells of anthers of ms3 plants. This material was also autofluorescent and had an affinity for the fluorochrome primuline which identified sporopollenin. By the early microspore stage, microspores of ms3 plants were unusually enlarged and the tapetum surrounding them prematurely degenerated. This abnormality of tapetal behavior seems to be associated with microspore abortion and serves as an early marker for sterility. Other differences noted between the anthers of ms3 and normal plants with the staining procedures used, were variations in the endothecium and the thickness and degree of staining of the microspore and pollen walls. All of these differences suggest that the effect of the ms3 gene in the homozygous condition is expressed during early anther development, probably beginning at meiosis and directly influences the malfunctioning of the tapetum. The results of this study support numerous other published reports on both genetic and cytoplasmic male sterility implicating the tapetum as the primary tissue responsible for male sterility.
Differences among Nematode Populations in Tall Fescue Pastures in North, Central, and South Alabama1
Authors: Pedersen J. F. , Rodriguez‐Kabana R.
Published: July 2010

Surveys of nematode populations in tall fescue (Festuca arundinacea Schreb.) pastures in north, central, and south Alabama in 1982 and 1983 showed significant differences in frequency of occurrence of many nematode species by geographical region. Although nematode damage has been implicated in the poor adaptation of tall fescue to the sandy soils of the extreme Southeast, many plant parasitic nematode species occurred in low frequency in south Alabama pastures. There were significant differences in the frequency of occurrence of Paratrichodorus christiei (Allen) Siddiqi by region. This nematode occurred with relatively high frequency in south Alabama in both years. There were no differences in the frequency of occurrence of Helicotylenchus spp. [principally Helicotylenchus dihystera (Cobb) Sher]. However, Helicotylenchus spp. occurred with high frequency and in high numbers in all three geographical areas.
Solute Leakage from Artificially Aged Soybean Seeds after Imbibition1
Authors: Schoettle Anna W. , Leopold A. Carl
Published: July 2010

It is known that aged seeds release more solutes upon hydration than unaged seeds. Previous studies of this response have utilized measurements of leakage during imbibition, which combine changes in leakage due to imbibitional stress with changes due to the aging response. We have examined the leakage characteristics in response to accelerated aging after virtual completion of a gentle hydration. Solute leakage from imbibed soybean cotyledons increased with accelerated aging in a linear manner in the range over which vigor was depressed. The UV absorbing solutes that leaked from these seeds included a group with a molecular weight (MW) of over 2000 and another group of MW less than 500. The MW profile of leaked compounds reflected changes in butanol‐extractable solutes with accelerated aging. The decline in seed vigor was associated with the lowering of the level of low molecular weight compounds in the cotyledonary cells. Increases in leakage with accelerated aging were closely associated with increases in areas containing damaged cells as evidenced by staining with Evans Blue. These findings indicate that even when hydration stress is minimized, a major contribution of the A260 detected solutes leaking from soybeans after accelerated aging is from cells which had experienced massive membrane damage.
Pericarp Resistance to Mechanical Puncture in Sunflower Achenes1
Authors: Stafford R. E. , Rogers C. E. , Seiler G. J.
Published: July 2010

Pericarp resistance to mechanical puncture using a penetrometer was determined for achenes of 72 sunflower (Helianthus annuus L.) genotypes grown in a greenhouse and sampled at 1, 5, 10, 15, and 20 days after fertilization. This study was undertaken to determine resistance of developing sunflower achenes to mechanical puncture and to relate this to possible genetic resistance to the sunflower moth, Homoeosoma electellum (Hulst). Pericarp resistance to puncture was found to be directly correlated with presence of phytomelanin. Significant genotypic differences in resistance to puncture were found among restorer (RHA) and maintainer (HA) lines. Achenes of the restorer lines RHA 272 and RHA 274 were most resistant to pericarp puncture. Of the maintainer lines, achenes of HA 65, HA 246, and HA 250 showed greatest resistance to pericarp puncture. Prediction equations indicated a positive linear relationship between resistance to puncture of the pericarp and age of the respective achene.
Leaf Orientation, Light Reception, and Growth of Winter Wheat1
Authors: Kirkham M. B.
Published: July 2010

A major goal of crop scientists is to develop methods of harnessing solar energy. Efficient utilization of direct‐beam radiation is one method. Therefore, it is important to determine radiation received on the inclined and horizontal surfaces of leaves. The objective of the present study was to determine if, and to what extent, two cultivars of winter wheat (Triticum aestivum L. ‘KanKing’ and ‘Ponca’) received different amounts of direct‐beam radiation. The wheat was planted at two locations on the border between an Eudora silt loam (Fluventic Hapludolls, coarse‐silty, mixed, mesic) and a Muir silt loam (Cumulic Haplustolls, fine‐silty, mixed, mesic). During fall, winter, and spring months, values of I/I0 (ratio of intensity of received direct‐beam radiation to intensity of incident direct‐beam radiation) were calculated from solar‐noon sun angles, leaf orientation, and leaf angle. Leaf length, leaf width, leaf area, plant height, dry weight of tops, and grain yield also were determined. A majority of KanKing's leaves faced north and south and a majority of Ponca's leaves faced east and west. KanKing had more horizontal leaves than did Ponca, and KanKing's leaves appeared to receive a greater amount of direct‐beam radiation than the more erect leaves of Ponca. In general, KanKing had longer leaves, wider leaves, a larger leaf area, a higher dry weight of tops, and was taller than Ponca. Grain yields of the two cultivars were similar. The results showed that radiation reception of the two cultivars varied because they had different leaf orientations.
Inheritance of Resistance to White Mold Disease in a Diallel Cross of Dry Beans1
Authors: Fuller P. A. , Coyne D. P. , Steadman J. R.
Published: July 2010

The inheritance of resistance to Sclerotinia sclerotiorum (Lib.) deBary was investigated in a nonreciprocal diallel cross of six dry bean (Phaseolus vulgaris L.) lines. Data were taken on the parents and their 15 F2 populations in greenhouse and field. Within each environment, the genotypic mean squares were highly significant and accounted for 74 and 76% of the total variation in the greenhouse and field, respectively. Partitioning the genotypic variation revealed that the line effects were highly significant, accounting for 89 and 94% of the genotypic variation in the greenhouse and field, respectively. The variation resulting from nonadditive gene action was not significant in either environment. Disease severity was greater in the greenhouse than in the field, but neither the environment × genotype, nor the environment × line interactions were significant. Resistance to S. sclerotiorum in this set of parents was quantitatively inherited and due primarily to additive gene action. A breeding strategy emphasizing recurrent selection should lead to improvements in resistance.
Potential for Genetically Modifying Dark Respiration of Tall Fescue Leaves1
Authors: Volenec J. J. , Nguyen H. T. , Nelson C. J. , Sleper D. A.
Published: July 2010

High dark respiration rate (RD) may be a physiological process associated with low herbage yield of tall fescue (Festuca arundinacea Schreb.) during summer. Our objectives were to 1) examine genotypic variability and determine genetic mechanisms controlling RD and 2) examine interrelationships between RD, concentrations of Kjeldahl N and water‐soluble carbohydrate (WSC) of leaf blades, and yield components. Progeny of a seven‐parent diallel were grown and sampled in controlled‐environment chambers at 20°C and in the field during August and September. The RD was estimated manometrically on center‐sections of recently‐collared leaf blades. Concentrations of N and WSC were estimated on adjacent leaf blade tissue. Herbage was harvested, tillers per plant counted, and yield per tiller (YPT) calculated. Reciprocal effects evaluated in controlled‐environment chambers were not significant for any characteristic. Genetic variation among single‐cross progenies was significant for RD, leaf N, tillers per plant, and YPT largely due to general combining ability. Narrow‐sense heritabilities ranged from 0.60 to 0.90 which suggested that additive gene action predominated for these characteristics in this population. The RD was not correlated consistently with any characteristic measured. Concentrations of N and WSC of leaf blades were negatively correlated (r = −0.61). Positive rank correlations (P < 0.05) were obtained among progeny responses from controlled‐environment chambers and that of both field harvests for RD, tillers per plant, and YPT, and between field harvests for all variables (P < 0.01). Interrelationships among characteristics for parental plants were similar to those of the progeny. The similarity in ranking of RD of genotypes among controlled environment chambers and the field during summer and autumn suggests efficient identification of desired genotypes is probable over a range of environments.