bluuebunny/crossref_metadata_2025 huggingface dataset:
Backcrossing High Seed Protein to a Soybean Cultivar
Authors: Wilcox James R. , Cavins James F.
Published: July 2010

An inverse relationship between seed yield and seed protein concentration has limited success in developing soybean [Glycine max (L.) Merr.] cultivars with high seed protein. High protein from the donor parent ‘Pando’ (498 g kg−1 protein) was backcrossed to ‘Cutler 71’ (408 g kg−1 protein) to determine if the yield of Cutler 71 could be recovered in addition to the high protein from Pando. Random F4‐derived lines, plus three lines with highest seed protein concentration, from the initial cross, the BC1, and the BC2 populations, were evaluated for agronomic traits in separate, two‐replicate tests for 1 yr at West Lafayette, IN. Seed from replication composites were evaluated for protein and oil concentration using near infra‐red reflectance or near infra‐red transmission. The parent line for each backcross was selected first for high seed protein, then for yield and agronomic similarity to Cutler 71. Random F4‐derived progenies of the BC3 population, the parent line for each backcross, and the cultivars Pando, Cutler 71, and Hamilton were evaluated in three‐replicate tests for 2 yr at West Lafayette, IN. In each backcross generation, lines were identified with seed protein in excess of 470 g kg−1 and that progressively approached the yield of Cutler 71. In the BC3 population, one line averaged 472 g kg−1 seed protein and was significantly (P = 0.05) higher in seed yield than Cutler 71, similar in yield to the cultivar Hamilton. In each backcross population, there were inverse relationships between seed yield and seed protein (R2 values ranging from 0.33 to 0.06) and between seed protein and seed oil (R2 values ranging from 0.55 in BC1 to 0.94 in BC3). In successive backcross populations, minimum oil values increased from 148 in BC1 to 174 g kg−1 in BC3, indicating a trend toward recovering oil concentration (204 g kg−1) of Cutler 71. The data demonstrate that high seed protein can be backcrossed to a soybean cultivar, fully recovering the seed yield of the cultivar, suggesting the absence of physiological barriers to combining high seed protein with high seed yield in these populations.
The 1BL/1RS Translocation: Agronomic Performance of F3‐Derived Lines from a Winter Wheat Cross
Authors: Moreno‐Sevilla B. , Baenziger P. S. , Peterson C. J. , Graybosch R. A. , McVey D. V.
Published: July 2010

Cultivar comparisons have suggested that the 1BL/1RS wheat (Triticum aestivum L.)‐rye (Secale cereale L.) chromosomal translocation enhances agronomic performance and environmental stability of wheat. This advantage has been attributed either to disease resistance genes or to unproved adaptation genes on the 1RS segment. The objective of this study was to determine the effect of 1BL/1RS without the confounding effect of cult!var background by evaluating 17 homogeneous 1B, 20 heterogeneous 1B:1BL/1RS, and 22 homogeneous 1BL/ 1RS lines. The lines were randomly selected from the cross ‘Siouxland’/ ‘Ram’. The 59 progeny lines and the two parents were tested in seven Nebraska field environments with a randomized complete‐block design. Data were obtained for grain yield, components of yield, grain volume weight, anthesis date, plant height, and leaf rust infection. The 1BL/ 1RS class was 9% higher yielding than 1B and heterogeneous classes. This yield advantage was attributed to increased kernel weight, which was generally expressed in lower yielding environments. Differential response to disease pressure did not explain yield differences. Within chromosome classes, differences in grain yield were attributed more to variation in number of spikes per square meter not kernel weight. The grain yield advantage of the 1BL/1RS appeared to be associated with a postanthesis stress tolerance, which resulted in increased kernel weight of the 1BL/1RS genotypes.
Assimilate Flux Determines Kernel Set at Low Water Potential in Maize
Authors: Schussler J. R. , Westgate M. E.
Published: July 2010

Plant water deficits during flowering cause maize (Zea mays L.) kernels to abort. Lack of current and reserve photosynthate account for much of the kernel loss, but partitioning to ovaries at low ovary water potential (ψw) may also be limited by lack of assimilate demand. To test this possibility, we measured the water status, carbohydrate content, and growth of ovaries on plants grown in the field in pots containing 22 kg of soil under one of three light environments [Control, 75‐cm rows, 43 055 plants ha−l; Shade, same as Control except under shade cloth (55% fight interception) from the sixth leaf stage until physiological maturity; or Isolated, 122‐cm rows, 6727 plants ha−1] and exposed to a water deficit during pollination. Water was withheld at silk emergence and plants were hand‐pollinated 4 d later when silk ψ was ≈ − 1.1 MPa, leaf ψw was ≈ − 1.8 MPa, and photosynthesis was completely inhibited. The water deficit decreased kernel set, which was correlated with the inhibition of ovary dry matter accumulation. The concentration of sucrose and glucose increased in ovaries of water‐deficient plants, and ovary turgor remained at or above control levels. Thus, inhibition of ovary growth at low ψw was not related to a loss of turgor, nor was it caused by a depletion of ovary sugars. Sugar accumulation at low ψw, suggested that metabolism may have been impaired. Coupled with a low level of reserves, failure to utilize available sugars at low ψw would severely inhibit assimilate flux to the ear and render kernel set highly vulnerable to water deficits during pollination.
Source Strength Influence on Soybean Yield Formation during Early and Late Reproductive Development
Authors: Board J. E. , Wier A. T. , Boethel D. J.
Published: July 2010

Soybean [Giycine max (L.) Merr.] yield is affected more by assimilatory capacity (source strength) during reproductive (R1–R7) than vegetative (emergence to R1) growth periods, but relative sensitivities of yield components to source strength have not been clearly demonstrated. This study was conducted to verify that source strength (R1–R7) affects yield primarily through regulation of pod number. Source strength effects (R1–R6) on pod number and effects of altered source‐sink strength during R5 to R7 on seed per pod and seed size were determined. Soybean cultivar Centennial was planted at an optimal date in 1991 and 1992 near St. Gabriel, LA. Source strength during R1 to R6 and source‐sink strength during R5 to R7 were altered with three treatments: control, 30% shade (R1–R7), and partial pod removal 10 d after RS. Shade vs. control reduced source strength and yield 30% through a 20% reduction in pod number. Number of branch nodes and main stem pods per reproductive node, yield components shown previously to respond to source strength at late plantings, responded similarly to altered source strength at optimal planting dates. In contrast, a 28% decrease in source‐sink strength during R5 to R7 reduced seed per pod and seed size by only 7.7 and 4.5%, respectively. The results substantiate that source strength during R1 to R7 influences soybean yield primarily by affecting pod number and that R1 to R6 is the most responsive part of the reproductive period to altered source strength.
Intercropping Stokes Aster: Effect of Shade on Photosynthesis and Plant Morphology
Authors: Callan E. J , Kennedy C. W.
Published: July 2010

Stokes aster [Stokesia laevis (Hill) E. Greene] is a potential new crop source of an epoxy acid but grows slowly and does not yield the first summer. It could be intercropped that year. To evaluate Stokes aster's response to intercrop shade, plants were grown under 1010 [high light (HL)], 320 [medium light (ML)], or 120 [low light (LL)] μmol m−2 s−1 photosynthetic photon flux density (PWD) for 50 d prior to measurements of photosynthetic rate, light compensation point, light saturation point, chlorophyll concentration, and morphology of whole plants. Near light saturation points, LL and ML plants had the highest net CO2 assimilation based on leaf area and ML plants were highest based on land area. High light plants were least efficient due to a vertical leaf orientation. As environment light intensity (LI) declined, plants had more chlorophyll per unit dry weight (DW), a higher chl b/chl a ratio, less leaf DW, less leaf area, and a lower root/shoot ratio. Light compensation points were 25, 55, and 185 μmol m−2 s−1 PPFD for LL, ML, and HL plants, respectively. Saturation points were between 400 and 800 μmol m−2 s−1 for LL plants and between 800 and 1500 μmol m−2 s−1 PPFD for ML and HL plants. In an intercrop, stokes aster should produce efficiently on a leaf area basis but less efficiently on a land area basis when grown under a LI of 120 μmol m−2 s−1 or less. Growth in full sun after the overstory crop is harvested would not be a problem for intercropped plants.
Agronomic Performance of Barley Lines Derived from Tissue Culture
Authors: Bregitzer Phil , Poulson Malyn
Published: July 2010

The practical application of in vitro genetic manipulations to plant breeding may be hindered by unselected and potentially undesirable somacional variation. To determine the potential for recovering cultivars from tissue cultures without somaclonai variation, 30 families of tissue culture derived lines from six barley (Hordeum vulgare L.) cultivars were analyzed for agronomic performance. Each family was derived from a single regenerated plant that in turn was derived from an immature embryo callus culture. Four tosix R2 plants were selected from each family based on phenotypic similarity to the uncultured parental controls. One‐hundred‐seventy‐four R2 derived lines were advanced by bulking to the R5 generation. The results of replicated field trials indicated that the agronomic performance for the majority of these lines was altered by passage through tissue culture and that the alterations were generally undesirable. Cultivar‐dependent differences were noted in the frequency and degree of agronomic alterations. Families within cultivars was an important source of variation, but selections within families was not. Successful selection of tissue culture derived barley lines without somocional variation therefore may be cultivar dependent and may require screening large populations of regenerated plants.
Genetic Diversity among Common Bean Breeding Lines Developed for Central America
Authors: Beebe Stephen E. , Ochoa Ivan , Skroch Paul , Nienhuis James , Tivang Jan
Published: July 2010

A study was undertaken to estimate the relative degree of genetic diversity among lines of common bean (Phaseolus vulgaris L.) selected in Central America for BGMV resistance vs. lines that had no selection. Genetic distance (GD) based on the presence or absence of random amplified polymorphic DNA (RAPD) bands was estimated among breeding lines and cultivars of red and black beans. Another six black‐seeded cultivars from Brazil and Argentina were included for comparison. The multidimensional scaling plots revealed that the red and black beans in this study formed distinct clusters with no overlap. Based on consistency of marker frequencies within vs. between populations, reds and blacks were confirmed to be distinct populations. The mean RAPD marker diversity measured among lines selected for resistance was significantly less than that among unselected lines in reds (0.140 vs. 0.224) and blacks (0.170 vs. 0.223). Coeffecients of parentage (CP) were also utilized to estimate the relationships among selected and unselected lines. Selected lines displayed significantly larger CP than unselected lines in both reds (0.29 vs. 0.06***) and blacks (0.13 vs. 0.05***), reflecting closer genetic relationships and reduced diversity. Therefore, both molecular markers and CP indicated that selection for resistance had reduced genetic variability in both red and black beans. When CP were correlated with GD for reds, blacks, and all genotypes, correlations of −0.35***, −0.38***, and −0.36*** resulted, respectively. In spite of low correlation values, GD and CP presented similar tendencies. The choice of GD or CP as a measure of genetic relationship may depend on the quantity and quality of pedigree information available.
Breeding Systems of Several Vicia Species
Authors: Zhang X. , Mosjidis J. A.
Published: July 2010

Information on the breeding system of plants is crucial for maintenance of accessions in germplasm banks. Controlled pollination experiments were conducted in the field to determine the breeding systems of several Vicia species. Vicia articulata Hornem., V. benghalensis L., V. ervilla (L.) Willd., V. lutea L., and V. sativa L. were automatic self‐fertilizing species. Vicia pannonica Crantz was nonautomatic self‐fertilizing. Vicia villosa Roth ssp. villosa and V. villosa Roth ssp. varia (Host) Corbiere were cross‐fertilizing. Therefore, regeneration of the accessions of the latter two species requires the use of procedures that provide isolation from foreign pollen.
Carbon Isotope Discrimination: Potential for Indirect Selection for Seed Yield in Canola
Authors: Matus Alejandro , Slinkard Alfred , van Kessel Chris
Published: July 2010

Carbon isotope discrimination (CID) has been proposed as a parameter to select indirectly for improved water use efficiency and seed yield. To determine the effectiveness of CID to select indirectly for seed yield, 10 diverse canola (Brassica napus L.) genotypes were grown at five locations in Saskatchewan in 1992 and 1993. Samples were collected for CID determination from leaves at flowering, mature stems, and mature seed. Phenotypic correlations between seed yield and the three CID traits were not significant. Genotypic differences in CID were significant, but were caused by ‘AC Tristar’ canola, which is triazine tolerant and has a low photosynthetic capacity. The ranking of canola genotypes for CID was constant across locations and years. The CID of mature seeds was significantly lower than CID of leaves at flowering or CID of mature stems. The correlation between dry matter at flowering (DMF) and CID of leaves at flowering was negative and significant, but inconsistent across locations and years. The broad sense heritability (h2) for seed yield was similar to that for CID traits. These results suggest that CID would not be effective for indirectly selecting for improved seed yield in canola.
Epistasis in an Elite Maize Hybrid and Choice of Generation for Inbred Line Development
Authors: Lamkey Kendall R. , Schnicker Bruce J. , Melchinger Albrecht E.
Published: July 2010

Second cycle breeding, utilizing backcross and F2 generations, has become the predominant type of line development program in the U.S. maize (Zea mays L.) industry. Epistasis and linkage have been identified as possible limits to progress from selection in F2 and backcross populations. Objectives of this study were to determine the importance of epistasis in an elite maize hybrid and to determine the appropriate generation for initiation of inbred line development. Six generations of progeny were developed from B73 and B84: the two parental generations, Pl (B73) and P2 (B84); the F2 generation [(B73 × B84) F2]; the BCP1 generation [(B73 × B84) × B73]; the BCP2 generation [(B73 × B84) × B84]; and the F2‐Syn 8 generation (the F2 generation random mated for eight generations). Testcross progeny were produced by crossing random S9 plants from each of the six generations onto the inbred tester Mo17. One‐hundred progeny of F2 × Mo17 and F2‐Syn 8 × Mo17 and 50 progeny of BCP1 × Mo17 and BCP2 × Mo17, as well as the parental testcrosses, were harvested. The experiment was evaluated at four locations in 1990 and three locations in 1991. Epistatic effects were significant for grain yield and grain moisture, and accounted for 21 and 18% of the variation among generation means, respectively. The genetic variance and heritability for grain yield ranked F2‐Syn 8 > F2 > BCP1 > BCP2, but differences among generations were not significant. The predicted gains for each generation ranked in agreement with the heritability. Under low selection intensities (a = 20%), the predicted mean (usefulness) ranked the generations BCP22 > F2 >> F2‐Syn 8 > BCPI. Under high selection intensity (a = 1%), usefulness ranked the generations F2 > F2‐Syn 8 > BCP2 > BCP1. The choice between F2 and backcrosses as source populations is primarily a function of selection intensity. Our results suggest little to no advantage of random mating the F2 before initiating selection and inbreeding.
Custer Analysis for Genotype × Environment Interaction with Unbalanced Data
Authors: Ouyang Z. , Mowers R. P. , Jensen A. , Wang S. , Zheng S.
Published: July 2010

From the viewpoint of a seeds business, classification of locations into homogeneous groups based on genotype × environment interaction (GE) facilitates selection of testing sites and proper placement hybrids or cultivars. Our principal objective was to develop methods to cluster ICI Seeds' strip‐test locations into homogeneous groups with respect to GE. Difficulties encountered in these cluster analyses included missing values in the distance matrix used for cluster analysis (caused by unbalanced data), selection of a proper distance measure, and graphical presentation of clusters. We propose use of a modified distance measure to resolve the first two difficulties. Dendograms are used to present clusters, and bar charts are used to show relative effects of individual hybrids or cultivars within clusters. Classification of counties in Iowa is into four groups: northern, central, southeastern, and southwestern regions. The results of the GE analyses compare favorably with breeder and agronomist observations on hybrid adaptation and show some similar groupings with divisions of the state specified in the Iowa State University yield test report.
Inheritance of Russian Wheat Aphid Resistance in Spring Barley
Authors: Mornhinweg D. H. , Porter D. R. , Webster J. A.
Published: July 2010

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a devastating pest of barley (Hordeum vulgare L.). An excellent source of RWA resistance (STARS‐9301B) was recently released to the barley industry. This greenhouse study was conducted to determine the genetic control of RWA resistance in STARS‐9301B. Crosses were made between Morex, a susceptible malting barley cultivar and STARS‐9301B during 1992 and 1993. Genetic analysis was performed on the parents, F1, reciprocal F1, F2, and backcross (BC) populations, as well as 231 F2‐derived F3 families. Segregation in the F2 and BC populations indicated multiple gene control. Fourteen F3 families were found to be homozygous resistant and 16 were homozygous intermediate, indicating that two genes control RWA resistance in STARS‐9301B. Analysis of data from the F2 and BCs to both parents suggested recessive epistasis of a dominant gene (Dnb2) on an incompletely dominant gene (Dnbl). This type of genetic control will necessitate screening for RWA resistance after each cycle of selection in a breeding program.
Nitrogen Deficiency in Maize: II. Carbon‐Nitrogen Interaction Effects on Kernel Number and Grain Yield
Authors: Uhart Sergio Adolfo , Andrade Fernando Héctor
Published: July 2010

Assimilate and N supply at flowering are determinants of the number of kernels set in maize (Zea mays L.). The objectives of this work were (i) to evaluate the effect of N shortage on grain yield and its numerical components, particularly potential grain number, determining kernel losses due to morphogenesis d fertilization‐abortion, (ii) to analyze the combined effects and interactions of assimilate and N availability on kernel set, and (iii) to determine the existence of direct effects of N deficiencies on this yield component. Three experiments were conducted with a commercial hybrid (DK636) under field conditions at the INTA Balcarce Experimental Station, Argentina, without water limitations. The treatments consisted of different radiation levels, obtained by shading, combined with different levels of N availability obtained by the addition of N fertilizer or organic matter of high C/N ratio in the soil. Nitrogen stress reduced kernel number(K N) without a significant effect on morphogenesis of reproductive structures. Under normal incident radiation, kernel number was associated with crop and ear growth rate at flowering following linear + plateau functions. Under shading this relationship presented an optimum, indicating that the widely accepted linear and direct relationship (with or without plateau) between KN and crop or ear growth rate is not valid under high N rates and light stress at flowering. No direct effects of N were detected. Nitrogen deficiencies affected KN because of reductions in C assimilation.
Canopy Light Interception, Gas Exchange, and Biomass in Reduced Height Isolines of Winter Wheat
Authors: Gent Martin P. N.
Published: July 2010

A reduction in stem height may reduce light interception and thus reduce canopy gas exchange and biomass accumulation of winter wheat. This hypothesis was tested with 16 reduced height isolines in a hard red winter wheat background (Triticum aestivum L. cv Itana). These isolines were grown in the field in Hamden, CT, in 1991, 1992, and 1993, and biomass accumulation, leaf area index, light interception, and canopy gas exchange were measured throughout plant development. Comparisons were made between the four height classes: dwarf (Rht1Rht2), semidwarf Rht1 (Rht1rht2), semidwarf Rht2 (rht1Rht2), and tall (rht1rht2). Biomass of tall isolines was more than 20% greater than that of dwarf isolines early in development in each year and at maturity in 1991. Light interception of tall isolines was 20% greater than that of dwarf isolines during stem elongation in 1992 and at boot stage in 1993. Canopy photosynthesis of tall isolines was also more than 20% greater than that of dwarf isolines early in stem elongation in 1991 and 1992. After spike emergence, canopy light interception and photosynthesis did not differ among height classes. The low biomass of dwarf isolines was attributed to reduced light interception and canopy photosynthesis before spike emergence, compared with the taller isolines. Semidwarf isolines did not differ consistently from tall isolines in either biomass, light interception, or canopy photosynthesis, but semidwarf isolines had greater harvest index. Averaged across the three years, wheat plants of semidwarf stature yielded more than those with either tall or dwarf stature.
Red Clover Seed Production: III. Effect of Forage Removal Time under Varied Environments
Authors: Steiner J. J. , Leffel J. A. , Gingrich G. , Aldrich‐Markham S.
Published: July 2010

Red clover (Trifolium pratense L.) grown for seed in western Oregon must have the forage removed in spring so that flowering and seed maturation will be more uniform. There is little available information that describes the effects of time of forage removal on red clover seed production. This study was conducted to determine (i) the effects of time of forage removal on seed production of red clover grown under a range of common environmental conditions found in western Oregon and (ii) whether any crop phenological or environmental indicators can be used to describe optimal forage removal time. Twelve different experimental locations per year were established in 1990 and 1991 in commercial red clover seed production fields throughout a six‐county area in the Willamette Valley of Oregon. Forage was removed once per treatment and there were seven forage removal time treatments from early May to late June. Red clover seed yields are dependent on a relationship with the number of accumulated heat units (HUs) at the time of forage removal. The average HU optimum (199 HUs) is not exact for all sites, but can be adjusted for the estimated combined effects of factors that influence the relative productivity of each site. Relatively low yielding sites should have forage removal time advanced relative to the HU optimum, and high yielding sites should have forage removal time delayed. Also, named improved cultivars were not as sensitive to time of forage removal as are Oregon‐adapted ecotypes. Forage removal time is a critical factor that needs to be considered to achieve maximal seed yields.
Best Linear Unbiased Prediction of Maize Single‐Cross Performance
Authors: Bernardo Rex
Published: July 2010

In preliminary studies, best linear unbiased prediction (BLUP) has been found useful for identifying high‐yielding maize (Zea mays L.) single crosses prior to field evaluation. In this study, the effectiveness of BLUP for large‐scale prediction of yield, moisture, stalk lodging, and root lodging was investigated. Multilocation data from 1990 to 1994 were obtained from the hybrid testing program of Limagrain Genetics. For each of 16 heterotic patterns, the performance of m untested single crosses was predicted from the performance of n tested single crosses as YM = CMP Cpp‐1 YP, where YM = m × 1 vector of predicted performance of the untested single crosses; CMP = m × n matrix of genetic covariances between the untested single crosses and the tested single crosses; Cpp = n × n phenotypic covariance matrix among the tested single crosses; and YP = n × 1 vector of average performance of the tested single crosses, corrected for yield trial effects. Correlations between predicted and observed performance were obtained with a delete‐one cross‐validation procedure. For heterotic patterns with large (>100) numbers of tested single crosses, the correlations ranged from 0.426 to 0.762 for yield, 0.754 to 0.933 for moisture, 0.300 to 0.739 for stalk lodging, and 0.164 to 0.532 for root lodging. The correlations, especially for lodging traits, increased as larger numbers of tested single crosses were available. The results in this study were obtained from large and diverse data sets (600 inbreds, 15 183 data points, and 4099 tested single crosses across 16 heterotic patterns) and provide strong evidence that BLUP is useful for routine identification of superior single crosses prior to field testing.
A Sampling of the Phenetic Diversity of Cacao in the International Cocoa Gene Bank of Trinidad
Authors: Bekele Frances , Bekele Isaac
Published: July 2010

The International Cocoa Gene bank, Trinidad, is an international cacao (Theobroma cacao L.) germplasm depository that conserves nearly 2500 accessions in its field collection. A portion of this germplasm was characterized for phenetic diversity with morphological descriptors from the International Board for Plant Genetic Resources cacao descriptor list. Data for 28 quantitative and 26 qualitative descriptors were obtained on 100 accessions representing 24 populations. Associations among the accessions were examined by hierarchical average linkage cluster analysis. Variances of the standardized values were computed for the quantitative descriptors. The diversity and evenness of the qualitative descriptors were assessed with the Shannon‐Weaver diversity index (SWDI). The variances and the Shannon‐Weaver diversity indices summarized the direct contributions of the quantitative and qualitative descriptors to the similarity measure. The variances of the standardized quantitative descriptors ranged from 0.03 for flower ligule length to 0.07 for fruit husk weight. About 75% of the fruit and bean descriptors had variances greater than 0.045, compared to 17% for the flower descriptors, indicating a relatively higher discriminative value of the former. Normalized SWDI values greater than 0.50 were obtained for 69% of the 26 qualitative descriptors. Eighty percent of the flower descriptors had SWDI values greater than 0.50, compared to 60% for those of the fruit and bean. Cluster analysis indicated rich phenetic diversity in this sample of germplasm. At the 75% level of similarity, the accessions were grouped in 11 clusters, each containing two or more accessions. Nine accessions were ungrouped. This diversity should prove useful for breeding programs. The observed link between geographic origin and accession grouping suggested that it is necessary to collect and conserve germplasm representing a broad geographic range.
Inheritance of Restoration of Helianthus petiolaris sp. fallax (PEF1) Cytoplasmic Male Sterility
Authors: Miller J. F.
Published: July 2010

Worldwide production of cultivated hybrid sunflower (Helianthus animus L.) presently utilizes only the PET1 source of cytoplasmic male sterility. The use of one sterile cytoplasm creates a high degree of genetic vulnerability. The objective of this study was to investigate the stability of a new cytoplasmic male sterile source, PEF1, derived from Helianthus petiolaris sp. fallax Heiser and to determine the inheritance of restoration of this cytoplasm. Crosses were made between the PEF1 cytoplasmic male sterile source and several restorer lines known to restore the PET1 cytoplasm. None of the PET1 restorer lines had effective restoration genes for the PEF1 cytoplasm. Two genotypes, ‘Zaria’ (PI 371935) and HA 60 (Ames 4035), restored male fertility to the PEF1 cytoplasm. Fully fertile F5 plants obtained from these crosses were used to pollinate the PEF1 cytoplasm. The fertile F1 plants were self‐pollinated and backcrossed to the PEF1 source to obtain F2 and BC1F1 seeds, respectively. These generations were planted in the field nursery at Fargo, ND, in 1994. Data were recorded for pollen restoration. The restoration of the PEF1 cytoplasmic male sterile was determined to be controlled by two complementary dominant genes with cumulative gene action. The stability and effective restoration of the PEF1 cytoplasm indicated that this source could be utilized to decrease the genetic vulnerability in hybrid sunflower.
Cytokinins in Enhanced Growth and Tillering of Wheat Induced by Mixed Nitrogen Source
Authors: Wang Xingting , Below Frederick E.
Published: July 2010

Supplying wheat plants with mixtures of NO3‐ and NH4+ increases growth and tiller production, but the physiological basis is unclear. Our objectives were to evaluate the roles for cytokinins and N use (e.g., accumulation, distribution, and utilization of absorbed N to produce tillers) in eliciting this response. Two species of spring wheat (Triticum aestivum L. cv. Len and Triticum durum Desf. cv. Inbar) were grown hydroponically in the greenhouse with N supplied as all NO3‐, all NH4+, or an equal mixture of each form. In one experiment, the synthetic cytokinin N6‐benzylaminopurine (100 µM) was applied repeatedly (a total of five times) to the shoots during tiller initiation and development, while in another, xylem exudate was collected from cut stumps during the early stages of tiller development. Plants not sprayed with cytokinins produced more tillers and accumulated more N when grown with mixed N than with either N form alone. Cytokinin sprays did not affect tillering of mixed N plants but increased tillers in all‐NO3‐grown or all‐NH4+‐grown plants to levels close to that obtained with mixed N. For unsprayed plants, the presence of NH4+ increased the shoot/root ratio, the proportion of N in the shoot, and the efficiency with which absorbed N was used to produce tillers, compared with plants grown with all NO3‐. Exogenous cytokinin appeared to mimic the effects of mixed N (and in some cases NH4+) in altering the distribution and use of N by the plant. In addition, plants grown with mixed N or all NH4+ exhibited higher concentrations and mass transfer of cytokinins in the xylem than those supplied with all NO3‐. These data are consistent with the interpretation that mixed N enhancement of tillering in wheat is due to increased synthesis of cytokinins, induced in part by use of NH4+‐N.
Evaluation of Lines Derived from Wild Emmer Chromosome Substitutions: I. Quality Traits
Authors: Steiger D. K. , Elias E. M. , Cantrell R. G.
Published: July 2010

Grain protein quality (gluten strength) and quantity affect the quality of pasta extruded from durum wheat (Triticum turgidum L. var. durum) semolina. Previously, an accession of wild emmer (Triticum turgidum L. var. dicoccoides) with high protein concentration was used to develop a complete set of ‘Langdon’ (T. dicoccoides) [LDN(DIC)] substitution lines. This study was conducted to evaluate the potential of using these LDN(DIC) substitution lines as parents for deriving lines with increased grain protein concentration and acceptable gluten strength. Each of the 14 substitution lines and Langdon parent were crossed to a common male parent, ‘Vic’. Parents and F2:4 and F2:5 lines were grown in replicated trials at two locations in North Dakota in 1989 and 1991. Grain protein concentration and sodium dodecyl sulfate (SDS) sedimentation volume were measured. Population means and genetic variances were compared with those of the Langdon/Vic population to identify substitution lines that conferred improved quality characteristics, and to determine their potential use in a breeding program. Heritabilities were estimated from standard‐unit parentoffspring regression and from variance components. LDN(DIC) chromosome substitution populations 1A, 6A, 5B, and 6B were significantly higher than the Longdon/Vic population in grain protein concentration. One population, LDN(DIC) 1B, was significantly higher in sedimentation volume than the Langdon/Vic population. The results indicated that selected LDN(DIC) substitution lines, especially LDN(DIC) 5B and 6B, when crossed to a strong gluten parent, may be useful in deriving lines with increased protein quantity and quality.
Estimates of Genetic Variances in Two Spanish Populations of Maize
Authors: Malvar R. A. , Ordás A. , Revilla P. , Cartea M. E.
Published: July 2010

Reports of estimates of components of genetic variance in open pollinated populations of maize (Zea mays L.) have been mostly on U.S. Corn Belt germplasm, whereas few studies have been conducted using European germplasm. This study was undertaken to obtain estimates of genetic parameters for important agronomic traits in two populations (Ribadumia and Tuy) from northwestern Spain. Full‐sib within halfosib groups were developed by the Design I mating system and evaluated at two locations in Spain in 1987 and 1988. The populations showed a similar genetic structure with very small differences. Moreover, the pattern of genetic variability was similar to other germplasm because the greatest proportion of total genetic variance was attributed to additive effects for most traits. In contrast, estimates of dominance variance were large for yield, ear, and plant height and ear length. In general, additive × environment interaction variances were significant while dominance × environment interaction variances were not significant for either population. The large range of variation and the high values of heritability for lodging and ear and kernels traits, as well as values of expected gain from selection for these traits, suggested good potential for improvement through an intrapopulation selection program. However, the large dominance effects and the small additive effects for grain yield indicated that an interpopulation selection program would be effective if the large intrapopulation dominance variance is expressed in population crosses. Yield did not show significant additive variance so estimates of additive correlation with any trait were not calculated. Correlated response between yield and any trait is not expected and improved grain yield based on indirect selection of yield components is not recommended.
Photosynthetic Rates and Ploidy Levels among Populations of Switchgrass
Authors: Wullschleger S. D. , Sanderson M. A. , McLaughlin S. B. , Biradar D. P. , Rayburn A. L.
Published: July 2010

Photosynthetic rates reportedly increase with increasing ploidy levels among lowland and upland ecotypes of switchgrass (Panicum virgatum L.). Such reports are based on data derived from native plant materials and no investigation has tested whether a similar relationship exists among released or experimental populations. A series of studies were conducted to address this question, with rates of photosynthesis measured with an infrared gas analyzer and ploidy levels estimated with flow cytometric analysis of nuclear DNA contents. Analyses of nuclei isolated from young stems and stained with propidium iodide indicated that of the 14 populations examined, eight are tetraploids (‘Alamo’1, ‘Kanlow’, ‘NC‐116’, ‘NC‐216’, ‘PMT‐279’, ‘PMT‐785’, ‘Stuart’, and ‘Wabasso’) and six are hexaploids (‘Blackwell’, ‘Caddo’, ‘Cave‐in‐Rock’, ‘Pathfinder’, ‘Shelter’, and ‘Trailblazer’). Twelve of these populations (not including NC‐116 and NC‐216) were grown in the greenhouse and photosynthetic rates measured on the youngest fully expanded leaf blade 40 to 45 d after germination. Rates of photosynthesis did not differ among populations or between tetraploids and hexaploids. Field studies at Knoxville, TN, Stephenville, TX, and Blacksburg, VA, did indicate, however, that tetraploids often had mean photosynthetic rates 12 to 18% higher than those of hexaploids. These differences were observed at many field sites during May, June, and July, yet based on repeated sampling at Knoxville, rates of leaf photosynthesis measured in September were up to 6.5 μmol CO2m−2 s−1 higher in hexaploid compared with tetraploid populations. Contrary to earlier reports that photosynthetic rates increase with increasing ploidy level, our results indicate that such a relationship is not consistent for tetraploid and hexaploid populations of switchgrass but rather may change with season or environmental stress.
Growth at Low Temperatures Increases Alfalfa Leaf Cell Constituents Related to Pasture Bloat
Authors: MacAdam Jennifer W. , Whitesides Ralph E.
Published: July 2010

The incidence of alfalfa (Medicago sativa L.) pasture bloat appears to increase with growth at the low temperatures that prevail in the high‐altitude valleys of the Intermountain West. This study determined whether plant characteristics associated with bloat are more prevalent in the leaves of alfalfa plants grown at suboptimal (15/5°C) day/night temperatures than in plants grown at optimal (25/15°C) temperatures. We hypothesized that the larger leaves characteristic of alfalfa grown at low temperatures would contain more soluble protein and chlorophyll than leaves of plants of the same cultivars grown at higher temperatures, even though cell number per leaf remains constant. We also expected that the larger cells typical of alfalfa grown at low temperatures would rupture more easily than cells of alfalfa grown at warmer temperatures. Fresh leaves were ground with a mortar and pestle, or shaken in buffer with glass beads to simulate mechanical damage such as would occur with rumination. Leaves from growth chamber‐grown Ranger and Fortress alfalfa contained more chlorophyll and more than twice the soluble protein when grown at low than at optimal temperatures. Contrary to our expectations, susceptibility of cells and tissue to damage decreased by approximately 15% with growth at low temperatures. Soluble plant protein and chlorophyll have been implicated in alfalfa bloat, and the increased content of cellular components related to bloat with low temperature growth could increase the rate of their release into the rumen, resulting in bloat.
Rhizomatous Lotus corniculatus L.: II. Morphology and Anatomy of Rhizomes
Authors: Li B. , Beuselinck P. R.
Published: July 2010

Birdsfoot trefoil (Lotus corniculatus L.) is a valuable forage legume. Rhizomatous L. corniculatus germplasm from Morocco was recently discovered. Increased persistence may result from rhizomatous habit, because new plants vegetatively generated by rhizomes could replace diseased or dead plants. Rhizome morphology in L. corniculatus from Morocco is unique because taxonomic descriptions for L. corniculatus do not include the presence of rhizomes. The objectives of this study are to describe and compare morphology and anatomy of subterranean lateral shoots (rhizomes) and aerial shoots (stems) L. corniculatus. Rhizomes of Moroccan L. corniculatus are initiated from axillary buds on basal portions of shoots. The rhizome consists of nodes and internodes, with buds, scale leaves, and adventitious roots occurring at each node. Anatomically, the rhizome of L. corniculatus has a large cortex, small pith, and six to seven primary vascular bundles. No endodermis exists in the cortex, and parenchyma cells contain starch. In contrast, the aerial shoot of L. corniculatus has a small cortex, large pith, and nine to 10 primary vascular bundles. An endodermoid layer is peripheral to the concentric ring of vascular bundles of the aerial shoot, and parenchyma cells in the cortex contain chloroplasts. Morphological and anatomical differences between L. corniculatus rhizomes and aerial shoots are distinguishable.
Heritability of Resistance to Bacterial Streak in Winter Wheat
Authors: Tillman B. L. , Harrison S. A.
Published: July 2010

Bacterial streak caused by Xanthomonas campestris pv. translucens reduces yield of wheat [Triticum aestivum (L.) em Thell] worldwide. Attempts to control the disease with bactericides have been unsuccessful. Resistant cultivars offer the best protection against yield loss, but little is known about the inheritance of resistance. The objectives of this study were to estimate the heritability of resistance to bacterial streak in soft red winter wheat and to derive an effective strategy for selecting resistant genotypes. About 60 F2:3 and F2:4 lines from each of three populations (Popl, Pop2, and Pop3) were tested for resistance to bacterial streak in three Louisiana environments with two to three replications per environment from 1991 to 1994. Variation due to genotype × environment (G × E) interaction occurred in each of the populations and was one‐fourth to one‐half the magnitude of error variance. Heritability of resistance to bacterial streak was relatively low and ranged from 0.12 to 0.70 (average 0.31) with parent‐offspring regression and from 0.18 to 0.40 with variance components (average 0.36). Heritability increased by 0.22, 0.29, and 0.29 for Popl, Pop2, and Pop3, respectively, with means of two replications and two environments. Non‐normal distributions in two of the three populations may have inflated estimates of heritability. Across populations, four lines were resistant in all three environments and 12 lines were resistant in two of three environments. Because of G×E interaction, testing should be conducted with at least two replications in two environments under high disease pressure. Such a testing program should be effective in selecting wheat lines resistant to bacterial streak.
The Relationship between Field Winter Injury and Fall Growth Score for 251 Alfalfa Cultivars
Authors: Schwab P. M. , Barnes D. K. , Sheaffer C. C.
Published: July 2010

The winter hardiness of alfalfa cultivars (Medicago saliva L.) affects stand persistence in northern climates. Fall growth, a measure of fall dormancy, has been associated with alfalfa winter hardiness in some areas of North America, including Minnesota. This study evaluated 251 North American alfalfa cultivars for fall growth and winter injury and determined the relationship between fall growth and winter injury scores under Minnesota winter conditions. All cultivars were established by transplanting 9‐wk‐old plants into space‐planted field plots in June 1991, 1992, and 1993. Plants were clipped in mid July and early September each yr and overwintered in the field. Fall growth was measured as individual plant height in mid‐October 1992 and 1993. Winter injury was evaluated in May each year. Entries differed for fall growth and winter injury score in all years. The 2‐yr‐mean fall growth score was related to the 3‐yr‐mean winter injury score (r2 = 0.85). Only seven of 251 entries fell outside the 95% confidence interval of the linear regression of winter injury score on fall growth score. Fall growth scores from 1992 and 1993 were correlated (r2 = 0.88). Winter injury scores from 1992, 1993, and 1994 were also correlated (r2 = 0.69‐0.96). Although concerns exist about the use of fall growth score to predict winter hardiness in less severe climates, it remains a useful predictor of alfalfa winter hardiness in Minnesota when winter injury data are not available.
Cynogenesis and Climatic Relationships in U.S. White Clover Germplasm Collection and Core Subset
Authors: Pederson Gary A. , Fairbrother Timothy E. , Greene Stephanie L.
Published: July 2010

Cyanogenesis, the production of hydrocyanic acid, is a trait in white clover (Trifolium repens L.) controlled by alleles at two unlinked loci, Ac and Li. The objectives of this study were (i) to determine the proportion of cyanogenic plants in the accessions of the U.S. white clover germplasm collection, (ii) to determine how representative the core subset was of the entire collection for cyanogenesis, and (iii) to determine the relationship of cyanogenesis, in accessions collected in situ, to collection site and climate. Twenty plants from each of 548 white clover accessions were grown in the greenhouse from 1991 to 1993. Two to three leaves per plant were harvested and the presence or absence of hydrocyanic acid was determined by the picric acid test. The U.S. germplasm collection was predominantly acyanogenic with a third of the plants evaluated being cyanogenic. Accessions with the most cyanogenic plants were collected in Morocco, Spain, Portugal, France, and Turkey while the least cyanogenic plants were collected in China, Romania, Russia, Kazakhstan, Croatia, Bosnia‐Herzegovina, and Slovenia. Accessions collected in Morocco, Portugal, and Spain had the greatest intensity of cyanogenic reaction. Geographic stratification with random sampling was an effective method of developing a core subset, as the white clover core subset was representative of the entire collection for total cyanogenesis and distribution of cyanogenic plants. Cyanogenic frequency was greater in accessions collected at low altitudes and at sites with high winter temperatures, lower summer precipitation, greater spring cloudiness (% sunshine), and less snow cover. Latitude of collection was not associated with cyanogenic frequency in white clover.
Plant Breeding, an Evolutionary Concept
Authors: Duvick Donald N.
Published: July 2010

Recorded history and the archaeological record tell us that plant culture has been an inseparable part of human society for the past several millennia. Repeatedly, humans have developed radical new technology for controlling the plants that provided their sustenance; they have modified the genotypes of the plants they cultivated, and at the same time they have modified the way the plants were grown. In modern terminology, plant breeding and plant culture have always been essential agents of change in human society. History and the archaeological record also tell us that in each instance the new technologies brought more changes than had been intended. The unexpected changes have sometimes been beneficial to human society, sometimes not. They have always modified the world of nature. Today we are dealing with the latest in a long series of radical new technologies for modifying our food production practices. One of them is biotechnology applied to plant breeding. In this essay, I will look at biotechnology for plant breeding in context with some of the revolutionary technologies that have preceded it. I then will evaluate its utility (or danger) to human society and also to the world of nature that sustains‐and includes ‐ humanity.