bluuebunny/crossref_metadata_2025 huggingface dataset:
Interspecific Hybridization in Trifolium L. Section Trifolium Zoh. III. Partially Fertile Hybrids of T. sarosiense Hazsl. ✕ 4x T. alpestre L.1
Authors: Quesenberry K. H. , Taylor N. L.
Published: July 2010

Interspecific hybrids of Trifolium sarosiense Hazsl. ✕ 2x and 4x T. alpestre L. were produced by hand pollination in a greenhouse. Pollinations of 530 florets of T. sarosiense (2n = 6x = 48) ✕ T‐ alpestre (2n = 2x = 16) and 806 florets of the reciprocal produced only five and 10 seeds, respectively. Plants grown from these seeds were weak and chlorotic, and all putative hybrids died before flowering. Pollinations of 75 florets of T. sarosiense ✕ autotetraploid T. alpestre (2n = 4x = 32) produced 28 seeds which gave rise to 22 vigorous hybrid plants. Reciprocal pollinations of 101 florets produced 18 seeds, but all seedlings were chlorotic and died shortly after germination. Estimated pollen viability of the T. sarosiense ✕ 4x T. alpestre hybrids ranged from 41 to 73%, with a mean of 64%. Most frequently, metaphase‐I cells of these hybrids contained 8 I and 16 II, and mean associations were: 6.59 I, 13.86 II, 1.43 III, and 0.35 IV. Although hybrid plants were mostly self‐ and cross‐incompatible, sib mating the hybrids produced 0.01 seed per floret. Backcrosses to the parents (T. sarosiense and 4x T. alpestre) produced 0.04 and 0.02 seed per floret, respectively. Pollinations of more than 5,000 florets of the hybrid by both diploid and tetraploid red clover (T. pratense L.) produced no verified hybrids. Attempts to cross other diploid species (T. rubens L. and T. heldreichianum Hausskn.) with the polyploid species (T. medium L. and T. sarosiense) produced no hybrids. The crossability data combined with cytological evidence suggests that T. alpestre may be an evolutionary link between the diploid and polyploid species of section Trifolium.
Long‐Term Preservation of Sorghum Seed as Affected by Seed Moisture, Temperature, and Atmospheric Environment
Authors: Bass L. N. , Stanwood P. C.
Published: July 2010

Longevity of stored seed is affected by a number of controllable environmental factors. Sorghum bicolor (L.) Moench. seeds were stored in sealed metal cans to test the effects and interactions of three moisture levels, six atmospheric conditions, and five temperature regimes over a 16‐year period. Vacuum, and atmospheres of air, nitrogen, carbon dioxide, helium, and argon were not significantly different in preserving seed germination. Sealed samples maintained better germination than samples in paper envelopes at temperatures above freezing. At –1 C and –12 C, all treatments maintained good germination. Temperatures of 10, 21, and 32 C interacted with seed moistures of 4, 7, and 10%. At 32 C and 10% seed moisture all seeds were dead in 8 years. Germination of sorghum seeds was best preserved at –12 C, regardless of seed moisture content, atmospheric environment, or storage medium during the 16 years of storage.
Composite Breeding Methods and the DSM System in Cereals1
Authors: Jensen Neal F.
Published: July 2010

The integration of the diallel selective mating system (DSM) is discussed in relation to overall project breeding operations. An overview of composite breeding and the role of competition is given as background. Composite breeding methods are shown to be efficient users of germplasm and effort; cultivars can be created in time periods comparable to other widely used methods. Competition is viewed as a helpful force in plant breeding. Important features of the DSM are a widening of the germplasm base of the breeding project and improved economy of operations. Implementation procedures of the DSM include: a) the objective basis for the system; b) the formation of DSM objective base composites; c) early generation field operations; and d) details of the selective mating option. The supplementary and reinforcing nature of the DSM are stressed relative to other known successful breeding methods.
Vegetative Growth Responses of Maize Genotypes to Simulated Natural Chilling Events1
Authors: Castleberry Ron M. , Teeri James A. , Buriel Joe F.
Published: July 2010

A series of three maize (Zea mays L.) inbreds and five hybrids, selected to represent a range of adaptation to maturity zones in the United States and Canada, were subjected to simulated early season chilling events to determine whether seedling growth responses to chilling were related to maturity adaptation. Chilling periods (17/5 C day/night temperatures) of 4, 8, and 23 days were superimposed on a control temperature regime without cold periods. Early maturing inbreds and hybrids had greater rates of leaf area expansion and had higher seedling dry weights than late maturing inbreds or hybrids. However, the proportionate reduction in growth rate during chilling was approximately equal for early and late maturing genotypes. Selection for early maturity appears to have produced genotypes with high rates of leaf area expansion during vegetative growth but without specific adaptations which modify the direct detrimental effects of chilling. Significant treatment by entry interactions were found in which some hybrids had accelerated growth rates after chilling while other hybrids and the inbreds tested had rates which were equivalent to controls. For hybrids with accelerated growth, leaves which were expanded following chilling treatment were larger than the equivalent leaves on control plants. This may reflect a mechanism to maintain assimilatory area under intermittent chilling conditions. In addition, these results suggest that natural environmental variability may greatly affect relative ranking of maize genotypes for growth rate and limit comparisons of field and controlled environment studies, unless a wide range of environmental simulations is used.
Selection Responses, Genetic‐Environmental Interactions, and Heterosis with Recurrent Selection for Yield in Maize1
Authors: Moll R. H. , Cockerham C. Clark , Stuber C. W. , Williams W. P.
Published: July 2010

Populations of maize (Zea mays L.) and their hybrids derived from full‐sib family selection and reciprocal recurrent selection for increased yield were compared with the corresponding original populations over a range of environments. The populations derived from six selection cycles were evaluated in 12 year‐location environ. ments, and the eight cycle populations and their hybrids were evaluated in a separate study in five year‐location environments.

Results of the two studies were in good agreement. Genetic environmental interactions were largely accounted for by responsiveness to environmental variation. Improved populations which were the direct result of selection were more responsive than the original populations. Other populations in which improvements resulted from indirect effects of selection showed less consistency in their responsiveness.

Heterosis was increased after reciprocal recurrent selection and decreased slightly after full‐sib family selection. Changes in heterosis were found to be compatible with a simple dominance genetic model.
Effect of Root Media on Growth of Wheat Seminal Roots1
Authors: O'Brien L.
Published: July 2010

Two wheat (Triticum aestivum L.) cultivars, one semidwarf (‘Israel M68’) and the other conventional height (‘Olympic’) were grown for 10 days in five root media in a growth chamber to determine differences in seminal root growth and the effect of root medium on seminal root growth. Differences were obtained between the cultivars for number of seminal root axes, maximum depth of penetration of the seminal root axes, number and length of lateral roots and total length of seminal root. Maximum expression of most variables was in a 1‐ to 2‐mm sized sand fraction. Significant cultivar ✕ root media interactions were obtained for shoot dry weight and root dry weight.
Effects of Defoliation and TIBA (Triiodobenzoic Acid) on Tillering, Dry Matter Production, and Carbohydrate Reserves of Two Cultivars of Kentucky Bluegrass1
Authors: Ackerson R. C. , Chilcote D. O.
Published: July 2010

The control of lateral bud development in grasses has important implications for turf management and in both forage and seed production. Defoliation, carbohydrate reserves, and growth regulators have been reported to affect this process. Studies were undertaken to evaluate the effects of clipping and Triiodobenzoic acid (TIBA) application on ‘Merion and ‘Pennstar’ cultivars of Kentucky bluegrass (Poa pratensis L.) under controlled environment. Weekly clipping heights of 5.0, 2.5, and 1.25 can were imposed for 6 weeks and tiller number, dry matter production, and carbohydrate reserves as a result of the treatments were determined. A comparison was made between clipping only and clipping plus application of 1,500 ppm TIBA as a foliar spray. Clipping retarded tillering in both cultivars with progressive reductions as clipping height decreased. However, plants of Merion bluegrass clipped and treated with TIBA increased in tillering in comparison to an unclipped, untreated control, or to those only clipped. Application of TIBA to Pennstar resulted in increased tillering when compared to the untreated experiment. However, differences among TIBA treatments were not significant. Dry matter production was reduced with clipping in both TIBA‐treated and untreated plants for both cultivars. However, TIBA application increased dry matter productivity when compared to the untreated experiment. When plants were treated with TIBA, a decrease in water soluble carbohydrates (WSC) in the stem bases was observed with decreased clipping height. Untreated plants generally did not show a reduction in WSC. It is suggested that an auxln‐carbohydrate balance theory alone cannot account for the release of lateral buds from apical dominance in Kentucky bluegrass.
Recurrent Selection for Grain Protein Content in Spring Wheat1
Authors: McNeal F. H. , McGuire C. F. , Berg M. A.
Published: July 2010

The importance of protein in the human diet justifies continued searching for new techniques and recombinations for accumulating in single wheat (Triticum aestivum L.) cultivars plant mechanisms responsible for grain protein formation. Recurrent selection within a series of crosses that involve high protein parents offers possibilities for such recombinations. High protein parents were chosen from a randomly selected group of 2,000 genotypes of the World Wheat Collection previously tested for grain protein content at Bozeman, Montana. Nine high protein genotypes from eight foreign countries were chosen and used in nine crosses. The high protein genotypes were crossed with each other or with U. S. cultivars and the two highest protein selections from F3 progeny rows of each cross were then crossed in all possible combinations to provide material for a second cycle of selection. First and second cycle selections were compared with each other and with original parents for potential advances in grain protein content and grain protein yield. Second cycle progeny had higher grain protein percentages than first cycle progeny. However, except for crosses 6711, 6721, and 6724, corresponding decreases in grain yield from first to second cycle provided the same or often less grams of protein in the second cycle. Crosses 6711, 6721, and 6724, plus high protein selections from other crosses, will be used as a germplasm pool for additional selection. A comparison of parents with 27 high protein lines from the second cycle showed an average increase of 2.5% in protein content and 12.0 g/2.4 m of plant row in protein yield. If these lines continue to produce high protein levels, they will be useful in breeding programs and in additional recurrent selection cycles.
Cytology, Reproductive Behavior, and Fertility Characteristics of Centipedegrass1
Authors: Hanna W. W. , Burton G. W.
Published: July 2010

Centipedegrass, Eremochloa ophiuroides (Munro) Hack., is an excellent lawn grass in the southeastern U.S. but information is limited on its cytology, reproductive characteristics, and fertility. Cytological observations on several introductions from China and on local sources of common centipedegrass showed that metaphase I meiosis was regular with nine bivalents; however, eight bivalents + two univalents were observed in 1 to 15% of the microsporocytes due to a precociously dividing bivalent. Pollen stainability ranged from 93 to 99%. Megasporogenesis and embryo sac development revealed normal sexual development and functional embryo sacs at anthesis. It was concluded that centipedegrass is a sexually reproducing species. Open‐pollinated, cross‐pollinated, and selfed seed ranged from 59 to 90%, 45 to 66%, and 0.0 to 58%, respectively. A self incompatibility system is present in centipedegrass.
Outscoring Rates in Oat Species Crosses (Avena sativa L. ✕ A. sterilis L.)1
Authors: Shorter R. , Gibson P. , Frey K. J.
Published: July 2010

Outcrossing percentages were estimated in F3 oat populations from four matings of Avena sativa L. ✕ A. sterilis L. The populations were generated from the original cross and backcross 1 to 5 to the A. sativa parent in each mating. Mean outcrossing averaged across generations ranged from 1.8 to 8.7% for the four matings. Outcrossing values were 2.8, 10.7, 9.1, 4.7, 2.4, and 4.9% in the Bc0, Bc1, Bc2, Bc3, Bc4, and Bc5, respectively.

Calculations showed that outcrossing in oats has a much greater relative effect on retaining heterozygosity in the F5 to F10 generations than it has in F1 to F5.
Scoring Photoperiod Sensitivity in Barley1
Authors: Tew Thomas L. , Rasmusson D. C.
Published: July 2010

Photoperiod response in barley (Hordeum vulgare L.) was studied in short and long‐day environments using selected barley lines and advanced generation populations. In a short‐day environment, days to flowering in selected barley lines ranged from 51 to 140; in a long,lay environment, from 37 to 48 days. In the same short‐day environment, days to node at ground level (NGL) ranged from 28 to 70 and in the long‐day environment from 20 to 30 days. The relative differences among lines were similar whether response was measured by days to NGL or by days to flowering. Also, data from four barley populations indicated that the NGL stage of growth provides a reliable guide to photoperiod sensitivity. Because of certain advantages, espedally saving of time and space in growth chamber experiments, we recommend that days to NGL be considered as an alternative to scoring of flowering as a measure of photoperiod response in barley.
Fungicide Application to Cottonseed Using Methylene Chloride Carrier1
Authors: Halloin J. M. , Minton E. B , Petersen H. D.
Published: July 2010

A method is described for quantitative application of chemicals to cottonseed (Gossypium hirsutum L.), using methylene chloride as a carrier. The objective of this study was to compare the performance of fungicides applied with methylene chloride with those of fungicides applied in wettable powder formulations in field studies. Nonsystemic fungicides used were PCNB (pentachloronitrobenzene) and ETMT [5,ethoxy‐3‐(trichloromethyl)‐l,2, 4‐thiadiazolel. Systemic fungicides used were chloroneb (l,4‐dicholoro‐2,5‐dimethoxybenzene) and carboxin (5,6‐ dihydro‐2‐methyl‐1,4‐oxathiin‐3‐carboxanilide). Germination of cottonseed was reduced by methylene chloride, apparently because it killed mechanically damaged seeds. This reduction was reflected in field studies where stands from seeds treated with fungicides in the solvent averaged 6% less than stands from seeds treated with fungicides in wettable powder formulations. Solvent‐applied fungicides, both systemic and nonsystemic, gave no more seed protection than wettable powders.
Environmental Effects on Turgor Pressure Response in Range Grasses1
Authors: Johnson Douglas A.
Published: July 2010

The effect of environment on turgor pressure responses was determined over a range of drought stress for the following grass species: Agropyron caninum (L.) Beauv.; A. desertorum [Fisch. ex Link] Schult.; A. intermedium (Host) Beauv.; A. trachycaulum (Link) Malte ex H. F. Lewis; Elymus cinereus Scribn. & Merr.; E. junceus Fisch. Plants of each species were started from seed and exposed to environments characterized by three nightday temperature combinations of 5/10, 10/15, and 15/25C. Water potential components of detached leaf samples were determined throughout a drying cycle with a psychrometric technique.

Turgor pressure responses changed as environmental conditions changed. Generally, plants in the low‐temperature environment maintained turgor over a wider range of leaf water potentials than plants did in the two higher temperature environments. Temperature environments also influenced turgor responses to a larger degree in some species than in others. The effect of environments on the leaf water potential where turgor declined to zero ranged from about 4 bars in E. junceus and A. intermedium to more than 8 bars in E. cinereus. When values of leaf water potential where turgor equals zero were used to rank species for drought resistance, rankings changed in different environments. These resuls suggest that the environments in which plant materials are grown should be carefully considered if maintenance of turgor is used to estimate relative drought resistance.
Isozyme Patterns and Differences in Plant Parts and Their Callus Cultures in Common Bean1
Authors: Bassiri A. , Carlson P. S.
Published: July 2010

Changes that occur in different enzyme systems during the culture of cells or callus have been extensively studied in several plant species. A question exists whether different tissues of the same plant maintain persistent tissuespecific patterns of gene expression during in vitro culture or whether in vitro cultures are characterized by identical patterns of gene expression no matter what their tissue of origin. This question is of importance to crop improvement since many genetic selections in vitro and rapid assays for agronomic traits in vitro require the cellular expression of tissue specific traits.

Extracts of primary leaf, epicotyl tip, epicotyl, cotyledon, mesocotyl, and radicle tissues of Phaseolus vulgaris L. and of callus derived from them were subjected to electrophoretic separation and assays of cathodal and anodal peroxidases and malate dehydrogenases and anodal acid phosphatase isozymes. The patterns of most of the isozyme systems were specific at the organ tissue level; however, a great uniformity of isozyme pattern occurred within and between the calli of the same or different origins. Rapidly growing calli derived from different plant parts expressed similar, though not in all cases identical, isozyme patterns.
Soybean Response to Selected Rice Herbicides1
Authors: Eastin E. F.
Published: July 2010

Occasionally rice (Oryza sativa L.) herbicide drift or accidental overspray to adjacent growing soybeans [Glycine max (L.) Merr.] occurs in the southeastern U.S. Therefore, five current, or potential, rice herbicides, either alone or in combination with propanil (3',4'‐dichloropropionanilide), were applied in the field for 2 years to the soybean cultivar ‘Davis’ when either three (V3) or eight (V8) nodes on the main stem had completely unrolled leaves. The purpose of this study was to determine if injury and yield loss to Davis soybeans occurs from the rice herbicides. Propanil, or combinations containing propanil, generally reduced yield of V3 soybeans, even at 0.6 kg/ha. A rate of 3.4 kg/ha reduced yield of both V3 and V8 soybeans. Bifenox [methyl‐5‐(2,4‐dichlorophenoxy)‐2‐nitrobenzoate] at 3.4 kg/ha and oxadiazon [2‐tert‐butyl‐4‐(2,4‐dichloro.5.isopropoxyphenyl)‐∆2‐l,3,4‐oxadiazolin‐5‐one] at 0.8 kg/ha reduced yield of V3 soybeans equivalent to 0.6 kg/ha propanil. Chlorpropham (isopropyl‐m‐chlorocarbanilate), molinate (S‐ethylhexahydro‐1H‐azepine‐1 ‐carhothioate) and thiobencarb [S‐(4‐chlorophenyl)diethylcarbamothioate] did not reduce soybean yields at either 0.6 or 3.4 kg/ha when applied at the V3 or V8 stage of growth.
Physiological Aspects of Peanut Yield Improvement1
Authors: Duncan W. G. , McCloud D. E. , McGraw R. L. , Boote K. J.
Published: July 2010

Development of new peanut (Arachis hypogaea L.) cultivars over the past 40 years has more than doubled yield potential. The purpose of this paper is to identify and evaluate the physiological changes made in the course of this varietal improvement that are responsible for the great increase in yield potential. Weekly harvests of large samples of four Florida cultivars, a Spanish peanut type, and one soybean (Glycine max (L.) Merr.) cultlvar gave the information needed to show the progressive changes in dry weights of all plant parts throughout the growing season. Other weekly samplings and observations gave numbers of pegs, flowers, and fruits as well as fruit weights, root length, shoot length, and leaf areas. Quantitative estimates of the physiologlcal factors responsible for the dry weight differences were made by computer simulation using the PENUTZ model. Differences in three physiological processes explain most of the yield variation among the five peanut cultivars; the partitioning of assimilate between vegetative and reproductive parts, the length of the filling period, and the rate of fruit establishment. Of these, the partitioning of assimilate had the greatest effect on fruit yield. Estimates of partitioning to fruit ranged from 41% in the first cultivar released to 98% in the most recently released cultivar. Crop growth rates did not differ significantly among peanut cultivars but all were much higher than the crop growth rate of soybeans.
Genetic Control of Aluminum Tolerance in Corn1
Authors: Rhue R. Dean , Grogan C. O. , Stockmeyer E. W. , Everett H. L.
Published: July 2010

Inbred lines, F1 hybrids, and composites of corn (Zea may L.) exhibited a wide range in tolerance to aluminum. F1 hybrids obtained from inbred lines differing in A1 tolerance exhibited tolerance equal to or greater than that of the more tolerant parent, indicating that tolerance is a dominant trait. F2 and backcross (BC) populations had two distinct classes of tolerance when screened over a wide range of AI stress, with segregating ratios of tolerant: sensitive plants of 3:1 and 1:1, respectively. Progeny obtained by selling tolerant plants from a composite also segregated into distinct classes of tolerance. The wide range in tolerance to AI among genotypes as well as the existence of distinct classes of tolerance in S1, F2, and BC populations suggested that AI tolerance in corn is controlled at a single locus by a multiple allelie series. Screening of reciprocal crosses as well as inbred lines in various cytoplasms showed no cytoplasmic affect on A1 tolerance in corn.
Resistance Evaluation and Inheritance of a Nonchlorotic Response to Brown Spot of Soybean1
Authors: Young L. D. , Ross J. P.
Published: July 2010

Soybean (Glycine max (L.) Merr.) plant introductions and cultivars adapted for maturity an North Carolina were screened for resistance to brown spot, caused by septoria glycines Hemmi. Neither immunity nor high levels of resistance were found in the 626 lines tested in the seedling stage in the greenhouse and near full. pod stage in the field. Six lines did not develop the characteristic chlorotic halo around necrotic lesions. Symptoms on these lines when inoculated with fungal conidia were limited to black lesions 1 to 2 mm in diam and small areas of dead tissue. Segregation of F2 progenies from two crosses of chlorotic‐lesion parent ✕ nonchloroticlesion parent fit the ratio of 15 chlorotic‐lesion plants: 1 nonchlorotic‐lesion plant. The F3 families segregated 15 chlorotic‐lesion families: 1 nonchlorotic‐olesion families when the classes of all chlorotic‐lesion families and segre. gating families were combined. All plants with nonchlorotic lesions had green cotyledons in the seed. It was concluded that the genes controlling the nonchloroticlesion response were either identical to those controlling chlorophyll retention in cotyledons in the seed or were closely linked to the chlorophyll retention genes.
Effect of Durable‐Press Resin Treatment on Tenacity and Elongation of Fiber from Upland Cotton Strains1
Authors: Lawson Reba , Ramey H. H. , Meredith W. R.
Published: July 2010

Untreated and mercerized fiber samples from 14 cultivars and breeding strains of Upland cotton (Gossypium hirsutum L.) were evaluated for changes in tenacity when given durable‐press (DP) treatment. The average loss of tenacity after DP treatment of untreated cotton was about 59%, with little variation among cultivars and strains. Mercerization increased fiber tenacity by 50%. The tenacities of premercerized‐resinated samples were 25% lower than mercerized but 12% higher than that of untreated fibers. Strength uniformity, the ratio of the tenacity at 3.2‐mm gauge length (T1) to the tenacity at 0‐gauge (T0), was negatively correlated with the ratio of T1 for premercerized DP‐treated samples to T1 for untreated samples.

Results of the study support the use of T1 as a breeding criterion of high fiber quality. Strength uniformity may also be valuable for the selection of breeding strains because it is a measure of the stress points along the length of the cotton fiber.
Characterization and Performance Evaluation of Frego Bract Isolines of Cotton1
Authors: Percival A. E. , Kohel R. J.
Published: July 2010

The effect was measured statistically of introgressing the morphological character frego bract (fg) into a cotton (Gossypium hirsutum L.) genetic standard Texas Marker‐1 (TM‐1) to evaluate the performance of two isolines. Two frego bract (fg) sources and their normal‐allele (Fg) counterparts were synthesized into TM‐1 isolines through a multiple backcross and selfing program. Five sub‐lines were isolated within each isoline. The sub‐line within each isoline did not vary significantly. Tests of the isolines showed that they differed significantly in seven of the 13 agronomic characters measured (date of first flower, seed cotton yield, lint yield, boll size, seed index, lint percentage, and lint index). The introgression of frego bract (fg) into the standard background delayed the date of first flower (indicating lateness) and reduced boll size, lint percentage, and lint index. The other three characters, seed cotton yield, lint yield, and seed index, were affected by the TM‐1 background of the isolines.
Effect of Change in Time of Flowering, Induced by Altering Photoperiod or Temperature, on Attributes Related to Yield in Maize1
Authors: Allison J. C. S. , Daynard T. B.
Published: July 2010

Flowering date of maize (Zea mays L.) was advanced, by increasing temperature or decreasing photoperiod, in order to study the effect of a decrease in length of vegetative phase on leaf area at flowering, number of female florets, and length of grain‐filling period. Plants of two single‐cross hybrids were grown at temperatures of 20 or 25 C, combined with 10‐ or 15‐hour photoperiods, until ears started developing, and then transferred to a single regime of a 14 hour photoperiod and 23/19 C light/dark temperature.

Increased temperature shortened the intervals from sowing to start of ear initiation and from ear initiation to silking. Decreased photoperiod shortened only the first period. Total leaf area per plant decreased as temperature increased, because leaves were smaller, and as photoperiod decreased, because fewer leaves were formed. Change in temperature altered total leaf area and time between sowing and silking by proportionately similar amounts, but change in photoperiod altered leaf area proportionately more than it did time to silking. Number of florets per ear row was little affected by temperature or photoperiod; apparent rate of floret initiation was unaffected by photoperiod but increased with temperature. Some plants died prematurely, evidently because of insufficient assimilate to maintain plant tissues. The black layer, denoting grain maturity, formed sooner in the kernels of these plants than in those of the remaining plants. In the latter, number of days from silking to black layer formation was decreased slightly by an increase in either temperature or photoperiod during the period before ear initiation.
Soybean Hypocotyl Growth Under Field Conditions1
Authors: Knittle K. H. , Burris J. S.
Published: July 2010

In soybeans (Glycine max (L.) Merr.) an epigeal emerger, the sole seedling organ responsible for elevating the cotyledons and epicotyl to the soil surface is the hypocotyl. Yet, soybean seedling and, in particular, hypocotyl growth under field conditions have not been well studied.

We measured hypocotyl length and swelling index (mg fresh weight/cm length) of several cultivars and two seed sizes at several planting dates and depths. Genetic variability was found in these two measurements. Cultivar differences in hypocotyl length generally followed the “long” and “short” hypocotyl classification of cultivars based on hypocotyl growth at 25 C. Hypocotyl swelling‐index differences generally were independent of the “long” and “short” cultivar classification. Hypocotyl length was highly correlated with rapidity of emergence, whereas hypocotyl swelling index was not highly correated with this measurement. Small seed of ‘Amsoy 71’ and ‘Corsoy’ produced seedlings with longer hypocotyls than did large seed, but there was no effect of seed size on hypocotyl length in ‘Wayne’. Small seed of all cultivars produced seedlings with lower values of hypocotyl swelling‐index than did large seed. Depth of planting significantly affected hypocotyl length and swelling index, but the specific soil factors affecting these two measurements were not identified. The consistently larger values of hypocotyl swelling index at deep as compared with shallow plantings, as web as the relatively large values for this measurement in the field as compared with those obtained in the laboratory, suggested that soil resistance is one limiting soil factor.
Effect of Downward Force on Soybean Hypocotyl Growth1
Authors: Knittle K. H. , Burris J. S.
Published: July 2010

Factors affecting hypocotyl elongation in soybeans Glycine max (L.) Merr., have not been well studied, with the exception of soil temperature. The limiting effect of soil resistance has not been examined heretofore. Soybean hypocotyl growth was studied in the laboratory. An apparatus was developed to apply a downward force to the apical hook of dark‐grown seedlings. An increase in downward force was accompanied by a decrease in hypocotyl length and an increase in hypocotyl swelling index (mg fresh weight/cm length of the hypocotyl). No difference in hypocotyl length was found between large and small seed of cultivar ‘Corsoy’, but hypocotyl swelling index was greater for large seed at all force levels. In cultivar ‘Amsoy 71’, small seed consistently developed seedlings with longer hypocotyls and had smaller values for the swelling index than did large seed at all force levels; the general response of Amsoy 71 to the inhibitory temperature of 25 C appeared to be independent of the response to downward force. The effect of force on hypocotyl length and swelling index was independent of temperature in cultivar ‘Wayne’, but hypocotyl elongation rate was significantly affected by temperature. Regression equations were obtained for hypocotyl length, swelling index, and hypocotyl elongation rate by using downward force and temperature as independent variables.
Photosynthetic Selection of Zea mays L. II. The Relationship Between CO2 Exchange and Dry Matter Accumulation of Canopies of Two Hybrids1
Authors: Vietor D. M. , Musgrave R. B.
Published: July 2010

Carbon dioxide exchange rate (CER) responses to irradiance level and temperature, and dry matter accumulation of the above‐ground portion of plants, were measured for field‐grown multiplant canopies of the maize (Zea mays L.) hybrids NY821 L1 ✕ C153 L1 and NY821 H6 ✕ C153 L3. A semiclosed and an open arrangement of a field scale gasometric system were used to measure the CER's in daylight and in darkness respectively. The objective of the measurements as to relate canopy CO2 exchange to dry matter accumulation rate of the above ground portion of the field grown canopies of each hybrid during grain filling.

Variation of solar irradiance at the top of the canopies and of plant age accounted for more than 90% of the variation of CERs measured in daylight. Variation of air temperature accounted for more than 77% of the variation of the CER's in darkness. The mean CERs in the dark changed less than 23 and 13% at 15 and 30 C, respectively, from the early dough to late dent stage. The CO2 efflux in darkness was attributed largely to maintenance metabolism in vegetative tissues because the small changes or reductions of CERs in darkness were observed while mean cob and kernel dry weights increased 220% from early dough to late dent.

Cumulative CO2 exchange from early dough to late dent was computed from regression models of the irradiance and temperature responses for each hybrid, and climatic data. The ratio of above‐ground dry weight change to cumulative CO2 exchange deviated from an expected value of 0.65 for both hybrids: they were 0.77 and 0.59 for L1 ✕ L1 and H6 ✕ L3, respectively.

A dry weight loss of from 11.7 to 16% from the vegetative tissues was larger than the substrate requirement for the estimated CO2 efflux that was attributed to maintenance metabolism from early dough to late dent. Part of the weight loss could have resulted from remobilization of stored carbohydrates from the vegetative tissues to the cob and kernels.
Forage Production and Quality of Synthetics Derived from Lolium ✕ Festuca Hybrids1
Authors: Berg Clyde C. , Hill R. R. , Buckner R. C. , Barnes R. F.
Published: July 2010

Nine experimental four‐parent synthetics from derivatives of Lolium ✕ Festuca hybrids and five cultivars of tall rescue (Festuca arundinacea Schreb.) were evaluated for spring growth, maturity, dry matter yield, in vitro dry matter disappearance (IVDMD), and other characters. Three synthetics were from parents that had been selected for yield and vigor in a topcross progeny test; four were from parents that were palatable in an animal acceptance trial; two were from parents that were unpalatable in an animal acceptance trial. Our objectives were to determine the effects of parental selection methods on performance of the synthetics and to compare the performance of the synthetics with that of tall rescue cultivars.

Synthetics from topcross‐selected parents had greater vigor and forage yields and matured earlier than those from palatable or unpalatable parents. IVDMD of the synthetics from topcross‐selected parents was not significantly different from the average IVDMD of synthetics from palatable and unpalatable parents. The synthetics from palatable parents had significantly greater IVDMD means than those from unl~alatable parents

The synthetics were less vigorous, matured earlier, had less first‐harvest, third‐harvest, and total season yield, and had a lower IVDMD mean than the tall rescue cultivars. Average second‐harvest yield of the synthetics significantly exceeded that of the tall rescue cultivars. Variability among the synthetics suggested that breeding could correct most of these deficiencies.
Direct and Indirect Recurrent Selection for Protein in Soybeans1
Authors: Miller J. E. , Fehr W. R.
Published: July 2010

Our objectives were to evaluate the effectiveness of population improvement by recurrent selection for protein percentage in soybean [Glycine max (L.) Merr.] seed by direct selection for high protein and indirect selection based on low oil, and to investigate methods of preventing change in maturity of populations during recurrent selection. A population was developed by crossing 12 high protein lines with 12 high yielding lines and intermating their progeny three times. A random sample of 100 S1 lines from the cycle 0 population was evaluated in two replications at two locations in Iowa in 1975. The 10 lines with highest protein and 10 with the lowest oil were used to develop two cycle 1 populations. Performance of 100 S1 lines from each population was evaluated in two replications at two locations in Iowa in 1976.

Protein increased from 43.1% in the cycle 0 population to 44.6% in the high protein and 43.9% in the low oil populations. Direct selection caused a significant decrease in both oil and carbohydrate, and indirect selection significantly reduced oil but did not change carbohydrate percentage. Selection for low oil cannot be considered an efficient method for protein improvement when cost and time for protein analysis are not limiting factors.

Maturity was 5.3 days later in the high protein population and 9.3 days later in the low oil population than in the cycle 0 population. The change in maturity was unacceptable, and three selection methods were evaluated, with and without restrictions on inbreeding, for avoiding similar shifts in the selection of lines for development of cycle 2 populations. Maturity class selection, linear regression adjustment, and a selection index were all successful in selecting lines with an average maturity similar to the cycle 1 populations. Restrictions on amount of inbreeding generally reduced expected gain from selection for seed composition.
Allocation of Resources in Selection for Resistance to Alfalfa Blotch Leafminer in Alfalfa1
Authors: Hill R. R. , Byers R. A.
Published: July 2010

Sixteen plants from each of 54 polycross families of alfalfa (Medicago sativa L.) were evaluated for reaction to the alfalfa blotch leafminer (Agromyza frontella Ron‐dani). Reaction to the insect was measured as the number of mined leaflets in a 30‐leaflet sample taken from each plant on first harvest and later‐season forage in 1976 and 1977. Estimates of variance components were used to calculate heritability of resistance and estimated gain from mass, half‐sib family, and modified ear‐to‐row selection. Predicted gains were compared to determine optimum allocation of number of replications and selection pressures to apply within and among families.

Variability among families was significant, but the heritability estimate was low (4.18%). Predicted gains with modified ear‐to‐row selection were greater than with mass selection only if the number of replications was large and the selection intensity within families was moderate. Half‐sib family selection always had smaller predicted gains than the most effective modified ear‐torow procedure. Mass selection had greater predicted gains when the number of replications was low and selection intensity within families was very low or very high. The predicted efficiency of mass selection increased relative to that of the other methods when the overall selection intensity decreased. The modified ear‐to‐row procedure with high selection intensity was recommended for increasing resistance to the leafminer alfalfa.
Selection for Yellow Clover Aphid and Pea Aphid Resistance in Red Clover1
Authors: Gorz H. J. , Manglitz G. R. , Haskins F. A.
Published: July 2010

Most red clover (Trifolium pratense L.) cultivars are susceptible to attack by the yellow clover aphid (Therioaphis trifolii Monell) and the pea aphid (Acyrthosiphon pisum Harris). Starting with 27 yellow clover aphidresistant plants selected from a wide diversity of germplasm, phenotypic recurrent selection was used to improve resistance to the two aphids. Through five cycles of testing and selection for yellow clover aphid resistance and three such cycles for pea aphid resistance, a synthetic, ‘N‐2’, was developed that had a high level of resistance to both aphids.
Recurrent Selection in Soybeans. I. Seed Yield1
Authors: Kenworthy W. J. , Brim C. A.
Published: July 2010

Three selection criteria were compared after three cycles of a recurrent selection procedure in soybeans (Glycine max (L.) Merr.). The criteria were seed yield per se, efficiency expressed as the ratio seed weight]straw weight, and an index in which the ranks of the components seed yield and efficiency were weighted equally. Selection was based on S1 progeny performance in a replicated nine‐hill plot grown at one location. Composites of S3 seeds from selected St progenies from each cycle within the three selection criteria were evaluated in four environments with 12 replications per environment to compare the effectiveness of each selection criterion for yield response. Only selection for seed yield per se was effective in significantly increasing the yield of the base population. An average yield increase of 134 ± 30 kg/ha/cyde of selection was observed for seed yield per se and 38 ± 55 kg/ha/cycle for the index. Yield decreased an average of 2 ± 47 kg/ha/cycle for selection based on efficiency.

Selection for seed yield per se had no significant effect on the unselected traits of seed size, percent oil, and percent protein. The favorable yield response observed in this recurrent selection program suggests that this breeding scheme may be used to develop populations of greater diversity and productivity.
Evaluation of Safflower Cultivars and Lines for Agronomic Traits1
Authors: Yazdi‐Samadi Bahman
Published: July 2010

In 1975, 1,618 lines and cultivars of safflower (Carghamus tinetorius L.) were studied for seven agr6nomic traits. All were from Iran except for 28 fines and cultivars from the United States. The traits, in terms of percentages of the mean of the two nearest check rows, varied as follows: 1) number of days from planting to flowering, 85 to 198%; 2) plant height, 61 to 182%; 3) number of heads per plant 10 to 241%; 4) number of seeds per head, 11 to 423%; 5) seed weight, 71 m 169%; 6) seed yield, 1 to 539%; 7) oil percentage, 79 to 124%.
Regression Analysis of Genotype‐Environment Interaction in Smooth Bromegrass1
Authors: Tan Wai‐Koon , Tan Geok‐Yong , Walton P. D.
Published: July 2010

Twenty‐one single crosses and seven selected parental clones of smooth bromegrass (Bromus inermis Leyss.) were grown in replicated trials at four locations in Alberta (Lethbridge, Edmonton, Kinsella, and Beaverlodge). Lethbridge and Edmonton were higher yielding environments than either kinsella or Beaverlodge. Plants at Beaverlodge had the highest yield per unit area and tiller dry weight.

The analyses of variance revealed that genotypes interacted significantly with environments for all characters. The genotype ✕ environment interaction source was further partitioned into the heterogeneity among regression and the residual. Environments were assessed in two ways: (i) the mean expression of all genotypes and (ii) the average performance of the seven parental genotypes. When environments were measured by the mean of all genotypes, a significant part of the interaction was ascribed to the heterogeneity among regression lines for all characters. The residual components were also significant in most cases indicating the presence of some unpredictable variation. The test of the heterogeneity of regressions against residuals revealed that the linear model would retain considerable predictive value for characters such as tiller density, yield per area, and fall yield since most of the interactions were accounted for by the heterogeneity of regressions.

When environment was assessed independently by the mean of the seven parents of the single crosses, the proportion of the interaction attributed to heterogeneity of regression differed considerably from that assessed dependently by overall genotypes. Height was the only character which failed to fit the linear model. Despite the differences obtained from the test of significance for heterogeneity of regressions, the rankings of the genotypes on the basis of their linear regression coefficients were similar. The results showed that the conclusions drawn from regression data were unaffected by the choice of measure of environment and that predictability of genotypes varied with characters measured.
Tolerance of Glabrous and Pubescent Cottons to Tarnished Plant Bug1
Authors: Meredith W. R. , Schuster M. F.
Published: July 2010

Lint yields of glabrous cottons (Gossypium hirsutum L.) are frequently lower than those of pubescent cottons. Since glabrous cottons might be more sensitive to tarnished plant bugs [Lygus lineolaris (Palisot de Beauvois)] than are pubescent cottons, we investigated the association between plant bugs and reproductive development of glabrous and pubescent cottons. Greenhouse evaluations were conducted in 1975 and 1977 with two plant bug nymphs per five plants. In the first test, reduction of flower buds by the plant bugs was 74% for four glabrous cottons, but was only 15% for two pubescent cottons. Similarly, in the second test, these reductions were 78 and 33% for five glabrous and two pubescent cottons, respectively.

We also needed to develop a method for detecting tolerance that was not associated with pubescence. Thirty hybrids were produced by crossing the cultivar ‘Carolina Queen’ and its glabrous (Sm2Sm2) isoline to 15 tester parents. Each tester parent and its two hybrids were grown in the field in two bisect regimes. In one, plant bug infestations were minimized with early‐season use of insecticides, while in the other infestations were encouraged by growing mustard (Brassica juncea L. Czern. & Coss.) nearby. Yields were decreased by the plant bug enhancement; yields of glabrous hybrids were reduced by 239 kg/ha while those of pubescent hybrids were reduced by only 163 kg/ha. Tolerance to plant bugs was observed in eight of the parental lutes, but only hi two of the Sm2sm2 hybrids. One of these hybrids, with ‘Timok 811’ as a parent, was itself hirsute; the other had a high terpenoid nectariless strain, HG‐BR‐8N, as a parent.

These data demonstrate that glabrous cottons are more sensitive to plant bugs than are pubescent cottons. They also indicate that possibly detection of germplasm tolerance to plant bugs can be facilitated through field evaluations of Sm2sm2 hybrids.
Bridging Ploidy Differences in Crested Wheatgrass with Hexaploid ✕ Diploid Hybrids1
Authors: Asay K. H. , Dewey D. R.
Published: July 2010

Hybrids between hexaploid (2n = 6x = 42) and diploid (2n = 2x = 14) Agropyron cristatum (L.) Gaertn. were crossed with the 6x and 2x parents, with colchicine‐induced tetrapinid (C4x) A. cristatum (2n = 4x = 28), and with natural tetraploid (N4x) A. desertorum (Fisch. ex. Link) Schult. (2n = 4x = 28). Fertility and chromosomepairing relationships were studied in the triploid, tetraploid, and pentaploid progenies to evaluate ways that 6x‐2x hybrids could be used to combine the genetic resources of the three ploidy levels into one germplasm pool. Cytological data demonstrated that genomes from e three ploidy levels were similar, differing only by structural rearrangements. The (6x‐2x) ✕ C4x tetraploids were the most fertile hybrids, with an average seed set of 53 seeds per spike compared with 21, 9, and 0.2 seeds per spike for the (6x‐2x) ✕ N4x, (6x‐2x) ✕ 6x, and (6x‐2x) ✕ 2x hybrids, respectively. Some (6x‐2x) ✕ N4x hybrid tetraploids, with germplasm of all three ploidy levels represented, were fertile enough to be used directly in a breeding program. The (6x‐2x) ✕ C4x hybrid tetraploids should have merit in crosses with (6x‐2x) ✕ N4x hybrids and N4x tetraploids to produce breeding populations with germplasm from the three ploidy levels. The sterility and meiotic irregularity of the (6x‐2x) ✕ 6x triploid hybrids and (6x‐2x) ✕ 6x pentaploid hybrids seriously limit their direct use in breeding schemes.