bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating Maize for Allelochemicals That Affect European Corn Borer (Lepidoptera: Crambidae) Larval Development
Authors: Warnock Daniel F. , Hutchison William D. , Tong Cindy B. S. , Davis David W.
Published: July 2010

European corn borer (ECB), Ostrinia nubilalis (Hübner), larvae develop resistance to management protocols in laboratory and field environments. Laboratory bioassays, tissue elemental analyses, and field resistance evaluations were conducted on ear tissues of maize, Zea mays L., to (i) identify genotypes and tissues which affect ECB development, (ii) isolate tissue extracts detrimentally affecting larvae, (iii) determine if high performance liquid chromatography (HPLC) absorption peaks are associated with biological activity, (iv) determine if ferulic acid and p‐coumaric acid affect ECB larvae, and (v) determine if laboratory and field resistance are related. Tissue and genotype did not affect larval survival. Silk tissue from W182E, ‘Apache’, MN 3153, and MN 276 reduced 10‐d larval weight, increased time to pupation, reduced pupal weight, and increased time to moth emergence compared with kernel tissue, which did not differ from the cellulose control. Methanol fractions of silks reduced 10‐d larval weight, but not larval survival, compared with the cellulose control. No methanol fraction of silks, except from MG 15, reduced 10‐d larval weight as much as nonextracted Apache silk, suggesting that some allelochemicals were not captured or were lost during extraction. HPLC analysis detected three to four large peaks only found in active methanol fractions. Ear tissue element levels, except for manganese (r = −0.70), were not associated with decreased 10‐d larval weight. Larvae reared on diet containing ferulic acid (2.61 and 1.67 mg/g) or p‐coumaric acid (<0.20 mg/g) had 10‐d weights similar to the control. Laboratory and field resistance were not correlated, suggesting that multiple resistance mechanisms exist in maize. The identification of allelochemicals affecting ECB larvae will allow breeding programs to select resistant maize genotypes.
Spatial Yield Distribution in Cotton Following Early‐Season Floral Bud Removal
Authors: Bednarz Craig W. , Roberts Phillip M.
Published: July 2010

A better understanding of cotton (Gossypium hirsutum L.) compensatory growth after loss of early‐season floral buds requires an assessment of the actual patterns of spatial yield distribution in damaged and undamaged plants. This study was conducted to determine if spatial yield distribution or yield components are altered in cotton in response to removal of early‐season floral buds. Beginning with the second week of squaring, floral buds were removed by hand for one, two, or three consecutive weeks. At 90 d after planting, plant height, leaf area index, main stem node number, fruit present, total fruiting positions, and dry weights were measured. The contribution to total yield from each fruiting position was determined at crop maturity. Results from this study show the lowest level of floral bud removal resulted in no differences in spatial yield distribution. As the intensity of early‐season floral bud removal increased, however, the probability of harvesting a mature boll decreased in the lower canopy but increased in the upper canopy. Removal of floral buds resulted in fewer first sympodial position fruit but more third sympodial position fruit at harvest. Thus, early‐season removal of floral buds resulted in additional seed cotton production on more apical and distal fruiting positions. These modifications in spatial yield distribution adequately replaced those floral buds removed early in the season because total seed cotton yield was not different among the treatments at crop maturity.
Flowering and Yield Response of Cotton to Application of Mepiquat Chloride and PGR‐IV
Authors: Biles Stephen P. , Cothren J. T.
Published: July 2010

Few studies have documented the effects of mepiquat chloride (MC) (1,1‐dimethyl piperidinium chloride) and PGR‐IV [0.001% (w/v) indolebutyric acid (IBA), 0.001% gibberellic acid (GA)] on flowering. This study was conducted in an effort to better understand the effects of these two plant growth regulators (PGRs) on cotton (Gossypium hirsutum L.) flowering when applied alone or used in sequential applications. Field experiments conducted in 1996 and 1997 at the Texas A&M University Agricultural Experiment Station near College Station, TX, contained the following treatments: an untreated control, MC, PGR‐IV, and a combination of both MC and PGR‐IV applied sequentially (PGR‐IV + MC). The MC and PGR‐IV + MC treatments caused plants to have a season‐long average of 0.55 and 0.48 more flowers m−1 of row d−1, respectively, than the untreated plants. All PGR treatments resulted in a higher rate of flowering than untreated plants between the 16th and 20th d of flowering. The MC treated plants also had 19.1 more total flowers per meter than PGR‐IV treated plants by the 40th d of flowering. Treatment effect on flower survival was different only for flowers that bloomed between the 36th and 40th d of flowering. At this time, the PGR‐IV + MC treated plants had a greater flower survival than plants treated with only PGR‐IV. All PGR treatments resulted in increased yields and boll numbers. These studies indicate that the application of MC and PGR‐IV, either in sequential applications or alone, increases both the rate of flowering and the number of flowers per meter of row, but does not impact the ability of flowers to survive to maturity.
Infection of Soybean with Soybean mosaic virus Increases Susceptibility to Phomopsis spp. Seed Infection
Authors: Koning Gwen , TeKrony Dennis M. , Pfeiffer Todd W. , Ghabrial Said A.
Published: July 2010

Infection of soybean [Glycine max (L.) Merr.] plants with Soybean mosaic virus (SMV) has been reported to enhance Phomopsis spp. seed infection, which reduces seed quality. The objective of this study was to determine the influence of SMV on Phomopsis spp. seed infection and seed germination and vigor. During 1995 to 1997, plants of two SMV‐susceptible cultivars (Clark and Williams) and their SMV‐resistant isolines (L78‐434 and L78‐379, resistant to SMV strains G1‐G6) were mechanically inoculated with SMV (G2 strain) at growth stages V4, V8 or R2, and Phomopsis spp. inocula were applied to all plants. Seeds harvested from SMV‐resistant isolines were consistently SMV free, whereas seeds from SMV‐inoculated susceptible cultivars accumulated SMV in seedcoats. Although environmental conditions were favorable, the incidence of Phomopsis spp. seed infection was consistently less than 12% in SMV‐resistant plants, and up to 14‐times greater in SMV‐inoculated susceptible plants, with primary infection occurring after seeds reached physiological maturity (at or after yellow pod stage). Seeds from SMV‐resistant isolines had high average standard germination (88%) and higher vigor (67% accelerated aging; 7 mS m−1 g−1 conductivity), whereas seeds from SMV‐inoculated susceptible cultivars had low standard germination (48%), low vigor (30% accelerated aging; 13 mS m−1 g−1 conductivity). Thus, infection by SMV at or before growth stage R2 increased the susceptibility of soybean seed to Phomopsis spp. infection, and resulted in poor seed quality and low vigor.
Distribution and Characterization of Heterochromatic DNA in the Tetraploid African Population Alfalfa Genome
Authors: Bauchan Gary R. , Hossain M. Azhar
Published: July 2010

A reference karyotype of tetraploid alfalfa (Medicago sativa subsp. sativa, ) African Population germplasm source (PI 536539) was constructed using the combined techniques of C‐banding and image analysis. The image analysis system is a method of obtaining enhanced images of chromosomes in which morphological data can be obtained for the development of karyotypes. In addition, C‐banding is a diagnostic tool for distinguishing the homologous chromosomes of alfalfa. Chromosome analysis of tetraploid alfalfa revealed that alfalfa has four similar series of chromosomes based on their chromosome morphology and C‐banding. The karyotype of African Population alfalfa germplasm consists of one set of chromosomes with satellites (SATs, Chromosome 8), four sets of submetacentric chromosomes (Chromosomes 1–4), and three sets of metacentric chromosomes (Chromosomes 5–7). All of the chromosomes have centromeric bands and a terminal band on the short arm, with the exception of the SAT. Interstitial bands were observed on the short arm of each of the chromosomes, with the exception of Chromosome 7. Chromosomes 1, 2, and 3 have interstitial bands on their long arms. There exists considerable variability in the number, intensity, and location of the constitutive heterochromatic DNA; however, this variability is not sufficient to preclude recognition of the homologous chromosomes. The chromosome banding pattern of the African Population germplasm resembles the distribution of heterochromatic DNA C‐bands of diploid M. sativa subsp. caerulea (Less. ex Ledeb.) Schmalh. The African Population karyotype of alfalfa developed in this study is suggested as the reference for the development of additional chromosome maps of diverse alfalfa populations.
Stability of QTL for Field Resistance to Blackleg across Two Genetic Backgrounds in Oilseed Rape
Authors: Pilet M.L. , Duplan G. , Archipiano M. , Barret P. , Baron C. , Horvais R. , Tanguy X. , Lucas M.O. , Renard M. , Delourme R.
Published: July 2010

Blackleg, caused by Leptosphaeria maculans (Desm.) Ces. et de Not., is a major disease of oilseed rape (Brassica napus L.) worldwide. Molecular markers would be useful tools to assist breeding for blackleg resistance. The objective of this study was (i) to map and characterize quantitative trait loci (QTL) for field blackleg resistance in doubled haploid (DH) and F2:3 populations from the cross ‘Darmor’ (resistant) × ‘Samourai’ (susceptible) and (ii) to compare QTL with those previously identified in the cross ‘Darmor‐bzh’ × ‘Yudal’. A total of 134 DH lines and 185 F2:3 families were genotyped with random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers and assessed for a disease index of resistance in 1998 and/or 1999 in one location. Genetic maps derived from the two populations included a total of 257 and 81 markers, respectively. Up to 30% of these markers were common to the Darmor‐bzh × Yudal map previously used. A total of six and four genomic regions were associated with resistance in the DH and F2:3 populations, respectively. They collectively explained 36 to 42% of the variation within each year and population. Three of them were consistent across the two populations derived from Darmor × Samourai cross and expressed dominant or overdominant effects. Four favorable alleles were derived from the susceptible parent. A total of 16 genomic regions were revealed for blackleg resistance in the two crosses Darmor‐bzh × Yudal and Darmor × Samourai studied. Four of them were consistent over the two crosses. The inconsistencies observed between populations and crosses can be explained by different genetic backgrounds and disease infestation levels. For marker‐assisted selection, these results suggest that QTL mapping must be carried out separately for each population.
The Extent of Use of Plant Genetic Resources in Research—A Literature Survey
Authors: Dudnik N.S. , Thormann I. , Hodgkin T.
Published: July 2010

Our aim was to assess the level of use of conserved plant genetic resources (PGR) in crop genetic research. To do this, we analyzed in detail the reports from four internationally recognized journals published in 1996. These journals were Crop Science, Euphytica, Plant Breeding, and Theoretical and Applied Genetics Our results indicate that about 23% of the articles published in these journals reported work conducted with material that originated in an ex situ PGR collection or was collected directly in the field. We also analyzed our results to determine the range of species and research topics involved, the sources of materials used, and the users of PGR for research. Of the material used, 80% was accessed from ex situ germplasm collections housed in genebanks in 27 countries and seven centers of the CGIAR. The rest of the studies utilized material gathered directly in the field. Almost all work was produced at national research centers and universities; very little work from private industry was published in the journals covered. Just under 20% of the institutions represented by authors were located in developing countries. Work published involved 112 species and included assessments of genetic diversity among accessions (42% of the studies), studies of the inheritance of biotic stress resistance (29%), taxonomic and phylogenetic analyses (16%), as well as cytologic, molecular and conservation research. Our research demonstrates a significant use of conserved material in research.
Family and Line Selection for Reduced Palmitate, Saturates, and Linolenate of Soybean
Authors: Streit Leon G. , Fehr Walter R. , Welke Grace A. , Hammond Earl G. , Cianzio Silvia R.
Published: July 2010

Development of soybean [Glycine max (L.) Merr.] cultivars with reduced palmitate and stearate will lower the total saturated fatty ester content of the seed oil, and reduction of linolenate will improve its oxidative stability. The objective of this study was to compare the family and line methods of selection for reduced palmitate, palmitate + stearate (saturates), and linolenate in four populations segregating for the major alleles fap1 and fap3 for reduced palmitate or the fan1(A5) and fan2 for reduced linolenate. Four random F3‐derived lines from 21 F2 families from each population were evaluated in a plant‐row‐yield test in 1995 and replicated trials at four locations in 1996. For the family method, the mean palmitate, saturates, and linolenate of the four F3‐derived lines of each F2 family was used to identify families from which to select individual lines. For the line method, lines were selected without regard to the family structure. The fatty ester contents of the selected and unselected lines based on data from one environment were compared with their mean fatty ester contents in the other environments. The number of lines selected for each of the traits by the family method was less than for the line method in all populations. There was a greater percentage of lines incorrectly rejected by the family method than by the line method. For development of cultivars with reduced palmitate, saturates, and linolenate, breeding methods that rely on family performance would not be more effective or efficient than methods that ignore family structure.
Evaluation of U.S. and Yugoslavian Maize Populations as Sources of Favorable Alleles
Authors: Trifunović Slobodan , Husić Ivan , Rošulj Milorad , Stojšin Radomir
Published: July 2010

Choice of an appropriate donor of alleles for use in reselection programs of existing inbred lines of maize (Zea mays L.) is crucial to the success of such programs. Well‐adapted local populations or exotic improved populations might be used as donors to improve a target genotype. The objectives of this study were to: (i) evaluate U.S. and Yugoslav maize populations as donors of favorable alleles for improvement of two single cross hybrids, (ii) estimate Dudley's relationship values to determine which inbred parent should be improved, and (iii) compare four estimators of the value of populations: Dudley's minimally biased estimators (Lplμ*), minimum upper bound (UBND), predicted three‐way cross (PTC), and net improvement (NI). Lplμ*, UBND, PTC, and NI showed significant differences among donors for grain yield. The highest values of favorable alleles were detected in populations, which had already undergone some type of family‐based recurrent selection for grain yield. The evaluation of Dudley's relationships between donors and parents of elite hybrids generally agreed with pedigree information. The improvement of both hybrids should be done with populations EP1, BS12C8, BS26, and ZPSyn1. The population EP1 can be used for comparative improvement of all three traits in the hybrid B73 × Mo17. Simultaneous improvement of grain yield and ear length in the hybrid A82/9 × L155 can be achieved with several donor populations. Rank correlations among applied estimators were positive and generally highly significant. The largest correlation values for grain yield were detected between Lplμ* and PTC.
Incorporation of Sequenced cDNA and Genomic Markers into the Soybean Genetic Map
Authors: Matthews Benjamin F. , Devine Thomas E. , Weisemann Jane M. , Beard Hunter S. , Lewers Kimberly S. , MacDonald Margaret H. , Park Yong‐Bong , Maiti Rama , Lin Jhy‐Jhu , Kuo Jonathan , Pedroni Monica J. , Cregan Perry B. , Saunders James A.
Published: July 2010

The soybean [Glycine max (L.) Merr.] expressed sequence tagged (EST) database is growing rapidly and promises to be a valuable resource for discovering agronomically important genes. Genetic maps featuring cDNA clones of known sequence and function are important because association of genes with phenotypes will increase understanding of the molecular mechanisms affecting valuable agronomic traits. Our objective is to place sequenced cDNA (EST) and genomic clones on an anchored soybean genetic map. The genetic mapping of these markers was conducted by standard restriction fragment length polymorphism (RFLP) techniques with an F2 population of 149 individuals derived from a cross between two publicly available soybean genotypes cv. Noir 1 (PI 290136) and BARC‐2 (Rj4) (PI 547895). DNA sequences of mapped EST and genomic clones were compared with accessions in GenBank, and significant sequence similarities are reported. The ESTs were more likely than the genomic clones to have a significant similarity to a GenBank accession. Because the objective was to map ESTs and sequenced genomic clones, only the 24 linkage groups (1200 cM) containing the 39 mapped EST and sequenced genomic clone markers plus the four phenotypic traits root fluorescence (Fr2), seed coat color (I), flower color (W1) and nodulation response (Rj4) were presented. Amplified fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) markers were added to increase marker density. Simple sequence repeat (SSR) markers were included to align this map with other soybean maps. The population has been further advanced to develop a F8:9 recombinant inbred line population available to researchers interested in associating the mapped cDNAs with quantitatively inherited traits.
Adaptive Ecology of Lotus corniculatus L. Genotypes: I. Plant Morphology and RAPD Marker Characterizations
Authors: Steiner J.J. , de los Santos G.Garcia
Published: July 2010

Birdsfoot trefoil (Lotus corniculatus L.) is a highly variable and widely distributed Old‐World perennial forage legume found in wild and naturalized populations throughout temperate regions of Europe, Asia Minor, North Africa, North and South America, Australia, and New Zealand. Understanding the relationships among birdsfoot trefoil morphologic, ecogeographic, and genetic characteristics may provide insights for better utilizing exotic germplasm. The objectives of this research were to (i) compare morphologic and random amplified polymorphic DNA (RAPD) classifications of 28 exotic and ecologically diverse genotypes from the USDA National Plant Germplasm System (NPGS) birdsfoot trefoil collection, and (ii) determine the relationships between genotype classifications and collecting‐site ecogeographic features. Eighteen morphologic characteristics, 130 RAPD bands, and eight collecting‐site ecogeographic characteristics were used to classify the genotypes. The relatedness of genetic, morphologic, ecologic, and geographic distances among the genotypes was measured using the product moment correlation. Genotype morphology was related to collecting‐site distances from one another and ecologic similarity. Genetic relatedness was also associated with collecting‐site ecology, and specific morphologic characteristics were associated with different ecogeographic features. The similarity between the genetic and ecologic classifications suggested that genotypes adapted to similar habitats, even if geographically distant, have acquired similar phenotypes. Since RAPD descriptors were associated with the ecologic similarity of genotype collecting sites but not with their geographic closeness, classifications of birdsfoot trefoil should rely on both ecogeographic and morphologic characteristics of accessions.
Discovery and Deployment of Molecular Markers Linked to Fusarium Head Blight Resistance: An Integrated System for Wheat and Barley
Authors: Van Sanford David , Anderson James , Campbell Kimberly , Costa Josè , Cregan Perry , Griffey Carl , Hayes Patrick , Ward Richard
Published: July 2010

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)], is a devastating disease that reduces yield, quality and economic value of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). The quantitative nature of resistance and tremendous expense of phenotypic screening indicate that the identification of resistant genotypes in breeding populations might be expedited by molecular markers. The markers must be polymorphic and informative across populations for them to be used by breeders. Worldwide, several groups are mapping genes for FHB resistance in wheat and barley and marker discovery is underway. Although these markers may be validated and made breeder‐friendly by the laboratories that developed them, the urgency of the FHB situation in North America and worldwide requires efforts to accelerate this process. To take advantage of economies of scale and accelerate information sharing, we propose the establishment of a National Genotyping Center (NGC) for barley and wheat. The immediate objective of the NGC would be to identify and deploy breeder‐friendly markers linked to FHB resistance quantitative trait loci (QTL). Over time, we propose that several regional genotyping centers will be established to correspond to regional and market class needs. The NGC would provide the regional centers with high throughput marker systems that would be used to genotype plants in breeding populations submitted by plant breeders. For the long term, we expect that the focus of the NGC will extend beyond FHB resistance, and that a key objective will be the development of new technologies to enhance plant breeding efforts.
Temperature and Photoperiod Effects on Sterility in a Cytoplasmic Male‐Sterile Soybean
Authors: Smith M.B. , Horner H.T. , Palmer R.G.
Published: July 2010

Manual cross‐pollination to produce large quantities of hybrid soybean seed is difficult and time consuming. An environmentally stable sterility system is one of the necessary components to produce large quantities of hybrid seed. The objective of this study was to subject cytoplasmic male‐sterile (CMS) BC5F1 plants, from a cross of a Chinese Glycine max wild‐type soybean with a Chinese wild annual soybean G. soja (male parent) and controls, to a variety of different temperature and photoperiod treatments to test whether CMS is stable under various environmental conditions. Plants were grown in growth chambers under controlled temperature, photoperiod, and irradiance regimes until pod set, and then they were transferred to a glasshouse until they matured. Plants were evaluated for time of anthesis after photoperiod induction (13 h light/11 h dark) and fertility or sterility. Anther squash and pod set data showed that sterility of the CMS line was stable under all environmental conditions tested, whereas fertility‐restored control plants remained fertile. Extreme environmental conditions led to delayed floral induction and/or stunted growth.
Diallel Analysis of Cultivar Mixtures in Winter Wheat
Authors: Gallandt E.R. , Dofing S.M. , Reisenauer P.E. , Donaldson E.
Published: July 2010

Cultivar mixtures have been suggested as a means to achieve increased crop productivity. By choosing cultivars that complement each other for performance of important traits, mixtures could be formulated to meet specific production requirements. The objective of this study was to evaluate the performance of wheat mixtures and their pure line component cultivars across a wide range of environmental conditions. Six winter wheat (Triticum aestivum L.) pure line cultivars and the 15 mixtures obtained by mixing seed of pairs of cultivars in equal proportions were evaluated in 33 environments in eastern Washington. Averaged across all environments, mixtures were 1.5% higher yielding than the mean yield of their pure line cultivar components. There was no difference in protein between mixtures and pure line cultivars. For both grain yield and protein, performance in mixtures was highly correlated with the average of the two component pure lines. Diallel analysis of mixing ability, analogous to genetic analysis of combining ability, demonstrated that pure lines differed in their ability to determine both grain yield and protein in mixtures. The ability to predict mixture performance based on pure line performance, together with the potential for above average grain yield, suggested that mixtures can be formulated to achieve specific production requirements.
Dollar Spot Resistance among Blends of Creeping Bentgrass Cultivars
Authors: Abernathy S.D. , White R.H. , Colbaugh P.F. , Engelke M.C. , Taylor G.R. , Hale T.C.
Published: July 2010

Disease is a major problem in creeping bentgrass (Agrostis stolonifera L.) on golf course putting greens. Genetic composition and uniformity of host populations can affect disease development. This study was conducted to determine the effects of blending creeping bentgrass cultivars on dollar spot (caused by Sclerotinia homoeocarpa F. T. Bennett) severity. ‘Penn A‐4’, ‘Crenshaw’, ‘L‐93’, ‘Mariner’, and ‘Penncross’ were planted in monostands or as two‐way or three‐way blends in a completely random design with three replications on a sand‐based putting green in the field at College Station, TX. Disease severity was determined by the number of infection centers and by total blighted area. Crenshaw was most susceptible, L‐93 most resistant, and all other cultivars were moderately resistant to dollar spot in monostands. Cultivar susceptibility in monostands to S. homoeocarpa was representative of each cultivars contribution to dollar spot severity in blends. In blends, L‐93 suppressed, whereas Crenshaw increased dollar spot. Penncross, Penn A‐4, and Mariner did not affect dollar spot severity across all blend combinations. Number of infection centers and infected area pooled across all monostands were similar when compared to all two‐ and three‐way blends indicating that dollar spot activity in blends was a compromise between resistance levels of individual cultivars. Two‐way blends of Penn A‐4, L‐93, Mariner, or Penncross with Crenshaw, however, resulted in 46 to 67% fewer infection centers and 71 to 98% less blighted area, when compared to the Crenshaw monostand. These data indicated that blending a resistant cultivar with a susceptible cultivar reduced dollar spot severity in the blended population.
Genetic Variability for Seed Size of Two‐ and Three‐Parent Soybean Populations
Authors: Johnson Susan L. , Fehr Walter R. , Welke Grace A. , Cianzio Silvia R.
Published: July 2010

Specialty soybean [Glycine max (L.) Merr.] cultivars with ≤ 80 mg seed−1 are needed to produce grain for export to Japan for the production of natto, a fermented food. The purpose of this study was to compare three population types for the recovery of lines that would have adequately small seed size for natto. Two small‐seeded and one normal‐size conventional cultivar or line were used to produce a small‐seeded × small‐seeded two‐parent population, a small‐seeded × normal‐size two‐parent population, and a small‐seeded × (small‐seeded × normal‐size) three‐parent population. Five sets of the three population types were developed with different parents in each set. The seed size of 100 random F2 plants was determined from each of the 15 populations and 10 plants of each parent. For each of the five sets, the progeny of the 100 F2 plants of each population type were compared as F2:3 lines with 10 entries of each of the three parents at two Iowa locations. The average percentage of lines with a seed size equal to or smaller than one of the parents in a cross was 90% for the small‐seeded × small‐seeded populations, 4% for the small‐seeded × normal‐size populations, and 20% for the three‐parent populations. An average of 10% of the lines from the small‐seeded × small‐seeded populations had significantly smaller seed size than either of the parents, and no transgressive segregation for small seed size was observed in the other two population types. For the development of small‐seeded cultivars, small‐seeded × small‐seeded and three‐parent populations would provide lines with acceptable seed size. A small‐seeded × normal‐size population may provide suitable lines if seed size of the conventional cultivar is sufficiently small and adequate resources are available to select for the limited number of small‐seeded segregates.
Genotypic and Environmental Effects on Grain Yield and Quality of Oat Grown in North Dakota
Authors: Doehlert Douglas C. , McMullen Michael S. , Hammond James J.
Published: July 2010

The grain yield and quality determine much of the value of an oat (Avena sativa L.) crop to the producer. This study investigated effects of genotype and environment on grain yield and quality. Twelve oat genotypes were grown during 3 yr at four locations in North Dakota where detailed environmental data were being collected. Grain yield, test weight, groat percentage, groat weight, and groat composition (protein, oil, β‐glucan, and starch concentrations) were evaluated. Results were subjected to analysis of variance and influences of environmental factors were evaluated by correlation analysis. Analysis of variance suggested that grain yield, groat starch, and ash concentrations were more strongly affected by environment than by genotype. Test weight, groat percentage, groat weight, protein, and β‐glucan were about equally influenced by environment and by genotype, whereas groat lipid was more strongly influenced by genotype. Significant environment × genotype interactions for all characteristics were attributed to differential resistance of genotypes to crown rust (caused by Puccinia coronata Corda var. aveneae W.P. Fraser & Ledingham) infection. Environments severely affected by crown rust produced grain with lower test weight, groat weight, and groat percentage in susceptible genotypes. Correlation analyses suggested that warm, bright (high solar radiation) spring weather, and cooler summer weather without excessive rains during grain filling generated the best oat yields with high quality grain.
Soybean Nodule Size and Relationship to Nitrogen Fixation Response to Water Deficit
Authors: King C. Andy , Purcell Larry C.
Published: July 2010

Decreased N2 fixation in response to drought in soybean [Glycine max (L.) Merr.] constrains grain and protein production, but differences exist among cultivars in sensitivity of N2 fixation to drought. We tested the hypothesis that large nodules may help confer drought tolerance because the fraction of N2‐fixing tissue (i.e., noncortical) is greater in large than small nodules. Consequently, the high energy demand of N2 fixation may create a greater sink demand by large nodules than small nodules during water deficit, increase phloem water supply to nodules, maintain nodule permeability to O2, provide sugars to support nodule activity, and supply water for the export of ureides from nodules. This hypothesis was evaluated for the cultivars Jackson (drought tolerant) and KS4895 (drought sensitive) in greenhouse and growth chamber experiments. Individual nodule mass and permeability to O2 were 0.65 to 0.70 times greater in Jackson than in KS4895 under well‐watered and water‐deficit conditions. For both cultivars, large nodules maintained a higher relative water content than small nodules across a range of soil‐water deficits. One day after labeling leaves of well‐watered plants with 14CO2, nodules ≤2 mm diam. had approximately 3.5 times the 14C concentration of nodules ≥4 mm diam. For plants of the water‐deficit treatment, 14C concentration of nodules ≤2 mm diam. was only 1.6 times that of nodules ≥4 mm diam. Nodules from the plants of the water‐deficit treatment had a greater 14C concentration than nodules from the well‐watered treatment for all nodule size classes >2 mm diam. Additionally, 14C concentration for all nodule size classes was greater for Jackson than for KS4895. We conclude that drought tolerance of Jackson is partially due to the advantages of large nodules, but that drought tolerance in Jackson also results from an inherently greater supply of photosynthates to nodules.
Primary Trisomics and SSR Markers as Tools to Associate Chromosomes with Linkage Groups in Soybean
Authors: Cregan P. B. , Kollipara K. P. , Xu S. J. , Singh R. J. , Fogarty S. E. , Hymowitz T.
Published: July 2010

Primary trisomics provide an excellent cytogenetic tool to associate genes and linkage groups with their respective chromosomes. A complete set of 20 primary trisomics (2x + 1 = 41) has been established in soybean [Glycine max (L.) Merr.]. A linkage map of soybean with 20 consensus linkage groups has recently been defined. Because simple sequence repeat (SSR) markers map to defined single positions in the soybean genome, the association of a SSR locus with a chromosome will provide an unambiguous association of a linkage group to a specific chromosome. The objective of this work was to demonstrate the use of SSR markers to associate linkage groups with chromosomes by means of primary trisomics. One population of F2 plants was developed from an F1 hybrid trisomic for chromosome 13 (Triplo 13) and a second F2 population was obtained from a F1 hybrid trisomic for chromosome 5 (Triplo 5). Polymorphic SSR markers from different consensus linkage groups were tested on a subset of 20 plants from each population to identify markers that appeared to show segregation that deviated from normal (1:2:1) disomic inheritance. Markers not associated with the specific chromosome segregated in a disomic (1:2:1) fashion. Markers identified in this manner were further examined in the complete population of F2 plants to identify those that demonstrated trisomic segregation (6:11:1). By this approach, Triplo 13 was associated with linkage group F and Triplo 5 with linkage group A1. This result was verified by the examination of seven SSR loci on linkage group F and eight loci from linkage group A1 with each showing trisomic segregation with the Triplo 13‐ and Triplo 5‐derived F2 populations, respectively. These results demonstrate the first association of molecular linkage groups with chromosomes in soybean and indicate that SSR markers provide a tool to associate the remaining 18 trisomics with their respective linkage groups.
Grain Fill Duration in Twelve Hard Red Spring Wheat Crosses
Authors: Talbert L. E. , Lanning S. P. , Murphy R. L. , Martin J. M.
Published: July 2010

The rate and duration of grain fill period has been shown to be associated with increased yield in cereals when water deficits occur during maturation. Grain fill duration can be approximated as the time between heading date and physiological maturity, allowing measurements to be obtained for large breeding populations. Our objectives were to determine the genetic variation for grain fill duration, and to determine its association with agronomic traits in a set of spring wheat (Triticum aestivum L.) crosses. Fifty F3.5 progenies from 12 spring wheat crosses plus parents were grown in replicated trials in three Montana environments. Heritabilities were consistently high across crosses for grain protein (mean = 0.92) heading date (mean = 0.89) and test weight (mean = 0.79), intermediate for physiological maturity (mean = 0.64) and grain yield (mean = 0.59) and lowest for grain fill duration (mean = 0.4). Earlier heading and later physiological maturity were associated with longer grain fill across crosses. Earlier heading also was often significantly correlated with higher grain protein concentration and higher test weight, but usually was not associated with grain yield. Longer grain fill duration was usually associated with higher grain protein in two environments, but with lower grain protein for the cool, wet environment. Grain fill duration showed no significant association with grain yield in most instances. Selection for early heading in early generations followed by selection for grain yield and grain fill duration in later generations using multi‐location trials may circumvent the negative association between grain yield and grain protein.
Forage Yield and Quality of Corn Cultivars Developed in Different Eras
Authors: Lauer J. G. , Coors J. G. , Flannery P. J.
Published: July 2010

Gains in corn (Zea mays L.) grain yield over time are well documented, but corresponding changes in forage and stover yield and quality have received less attention. Our objective was to describe yield and quality changes of representative cultivars used by farmers in the northern Corn Belt. Six open‐pollinated cultivars used prior to 1930, 24 cultivars representing four 15‐yr eras between 1931 and 1990, and six modern cultivars, for a total of 36 cultivars, were divided into early‐ and late‐maturity trials. Each trial was grown at three locations in Wisconsin during 1997 and 1998. Since 1930, corn forage dry matter yield has increased at the rate of 0.128 to 0.164 Mg ha−1 yr−1 with stover dry matter yields increasing at the rate of 0.043 to 0.054 Mg ha−1 yr−1 Forage crude protein has not changed significantly with time. Forage neutral detergent fiber concentration has decreased 0.825 to 0.948 g kg−1 yr−1, while forage in vitro digestibility increased 0.538 to 0.612 g kg−1 yr−1 Stover neutral detergent fiber concentration and in vitro digestibility have not changed over time. Since 1930 forage, stover, and ear yield have increased 1.4, 0.7, and 2.4% yr−1, respectively. This trend will no doubt continue, but greater progress might be made if corn forage breeding improvement concentrates on yield and quality changes in stover.
AFLP Variation in Bromus Section Ceratochloa Germplasm of Patagonia
Authors: Massa A. N. , Larson S. R. , Jensen K. B. , Hole D. J.
Published: July 2010

Bromus sect. Ceratochloa includes cultivated and native grasses of South and North America. This study examines amplified fragment length polymorphism (AFLP) variation among 30 hexaploid and two octoploid accessions of South American B. catharticus Vahl., B. coloratus Steud., B. lithobius Trin., B. mango Desv., B. stamineus Desv., and B. tunicatus Phil. and one accession representing octoploid North American B. carinatus Hook & Arn. The proportion of shared AFLP fragments among accessions ranged from 0.67 to 0.99. Although 65% of all fragments (including rare phenotypes) were present in hexaploids and octoploids, the South and North American octoploids displayed more fragments per plant and a common set of additional AFLP fragments not present in the hexaploid accessions. The hexaploid B. coloratus, B. lithobius, and B. stamineus accessions form one well‐defined group, evident by the proportion of shared AFLPs, whereas B. mango and B. tunicatus accessions formed another well‐defined hexaploid group. However, taxa within these two hexaploid groups were poorly resolved and subtend the highly diverse group of hexaploid B. catharticus accessions. Excluding octoploids, 94% of the AFLP diversity was partitioned among accessions but only 53% of the variation was distributed among taxa. Moreover, variation within hexaploid B. catharticus alone reflected 97% of the total diversity among hexaploid accessions. The overall correlation between geographical distances and genetic similarities among hexaploid accessions, irrespective of taxa, is low (r = −0.243) but significant (P ≤ 0.01). Although recognizable forms of genetic variation certainly exist, it may be difficult practically to identify more than one genetically distinct species in the hexaploid Ceratochloa germplasm of Patagonia.
A Comparison between Crop Domestication, Classical Plant Breeding, and Genetic Engineering
Authors: Gepts P.
Published: July 2010

Several claims have been made about genetic engineering (GE) in comparison with crop domestication and classical plant breeding, including the similarity of genetic changes between those taking place during domestication and by GE, the increased speed and accuracy of GE over classical plant breeding, and the higher level of knowledge about the actual genes being transferred by GE compared with classical breeding. In reviewing evidence pertaining to these claims, I suggest that (i) it is unlikely that changes introduced by GE will make crops weedier, although exceptions have been noted, (ii) changes brought about by GE currently often involve gain‐of‐function mutations, whereas changes selected during domestication generally involve loss‐of‐function mutations, (iii) adoption of GE cultivars has been much faster than any previous introduction and spread of agriculture that occurred earlier but has occurred at about the same rate as the spread of cultivars obtained by plant breeding, (iv) introduction of agriculture reduced the health of agriculturists compared with that of hunter–gatherers, suggesting that introduction of innovations do not automatically improve well being, (v) although GE is not a substitute for plant breeding, it can significantly contribute to plant breeding by generating additional genetic diversity, (vi) uncertainties associated with the site of insertion of transgenes in the genome and the expression of transgenes following insertion, makes GE less rapid and precise than originally claimed, and (vii) a potential advantage of GE over classical breeding is the knowledge of the actual gene(s) being inserted, although few cases of unwanted gene introductions through classical plant breeding have been documented. Further advances in GE will increase the precision of the technique, its relevance to consumers, and its environmental friendliness. What is most needed are even‐handed, case‐by‐case assessments of the benefits and potential pitfalls of GE in comparison with other crop improvement techniques. Classical plant breeding may, in the end, also be regulated in the same way as GE.
Screening the Cucumber Germplasm Collection for Fruit Yield and Quality
Authors: Shetty Nischit V. , Wehner Todd C.
Published: July 2010

Yield of cucumber (Cucumis sativus L.) in the United States has not been significantly increased during the last two decades. Our objective was to evaluate the USDA cucumber germplasm collection for fruit yield and quality. All cucumber plant introduction accessions from the USDA National Plant Germplasm System collection plus check cultivars and breeding lines (hereafter collectively referred to as cultigens) were evaluated for early, total, and marketable yield (number and weight), fruit quality rating, and days to harvest in small plots harvested once. All plants were treated with ethephon (2‐chloroethyl phosphonic acid) to make them gynoecious. Highly significant differences were observed among cultigens for all traits evaluated in the study. Pickling type cultigens with the highest yield (fruit weight) were PI 209065, PI 326598, PI 137848, PI 285610, and PI 264666. Slicing type cultigens with the highest yield were PI 234517, PI 118279, PI 304085, and PI 512614. Beit Alpha type cultigens with the highest yield were PI 167050, PI 163213, PI 532519, PI 211978, PI 357864, PI 183231, and PI 211117. Trellis type cultigens with the highest yield were PI 264228, PI 478366, PI 390262, PI 532524, PI 390267, and PI 532520. The USDA collection also exhibited a wide range in diversity for marketable fruit number, fruit weight, percentage of culled fruit at harvest, fruit quality, and days to harvest. High yielding cultigens identified in the study could be used to develop high yielding cultivars.
Soil Type and Moisture Level Influence on Alamo Switchgrass Emergence and Seedling Growth
Authors: Evers Gerald W. , Parsons Margaret J.
Published: July 2010

Attempts to establish lowland types of switchgrass (Panicum virgatum L.) in the Lower South have frequently been unsuccessful. A greenhouse study was conducted to determine the influence of soil texture and moisture on ‘Alamo’ switchgrass emergence and seedling growth. Soils used were a very fine sandy loam, loamy fine sand, silt loam, and clay that were watered every 3 to 4, 7, 10 to 11, or 14 d. Emergence was recorded daily for the first 28 d and seedlings were harvested at 6 wk to determine survival and seedling traits. The study was initiated on 30 March 2001 and repeated on 29 May and 24 July. Run date caused significant (P ≤ 0.001) interactions for all measurements with soil series and watering interval because of increasing greenhouse temperatures with each succeeding run. Watering interval affected emergence only at the 24 July run with emergence decreasing as watering interval increased. However, watering interval of at least 7 d was necessary for greater than 90% seedling survival in all soils. Only the clay soil consistently had good seedling survival (≥94%) at all watering intervals. Shoot stage and weight and root stage and weight decreased as watering interval increased. These seedling traits were usually higher in the loamy fine sand and very fine sandy loam if watered at least every 10 d. The trend for root/shoot ratios was to increase as moisture became limiting because shoot weight decreased faster than root weight. Rainfall occurring at greater than 10 d intervals is one of the factors for unreliable switchgrass establishment on sandy soils in the Lower South.
Agronomic Characteristics, Malt Quality, and Disease Resistance of Barley Germplasm Lines with Partial Fusarium Head Blight Resistance
Authors: Urrea Carlos A. , Horsley Richard D. , Steffenson Brian J. , Schwarz Paul B.
Published: July 2010

Fusarium head blight (FHB), incited by Fusarium graminearum Schwabe, has caused devastating losses in both yield and quality of barley (Hordeum vulgare L.) produced in the northern Great Plains from 1993 to 2003. Thirty‐five barley germplasm lines with partial resistance to FHB have been identified in exotic and unadapted germplasm lines. Little is known about their agronomic characteristics, malt quality, and reaction to other diseases as compared to adapted cultivars. This information is needed so barley breeders can make informed decisions when planning crosses involving the resistant germplasm lines. The objective of this study was to compare the agronomic performance, malt quality, and disease reaction of barley germplasm lines with partial FHB resistance to cultivars grown in the northern Great Plains. Agronomic and malting data were collected on the 35 germplasm lines and five check cultivars grown in five environments in North Dakota from 1998 to 2000. Data for FHB severity and deoxynivalenol (DON, a mycotoxin produced by F. graminearum) accumulation were obtained for the same 40 entries grown in FHB‐epidemic nurseries in North Dakota from 1997 to 1999. Seedling responses to foliar pathogens common in the northern Great Plains were determined in the greenhouse during fall 1997. None of the FHB‐resistant barley germplasm lines had acceptable malt quality for all traits. Kernel plumpness, grain protein concentration, and malt extract were the traits impacted most severely. The FHB‐resistant barley germplasm lines headed significantly later than the adapted barley cultivars. Most FHB‐resistant germplasm lines were susceptible to the common foliar diseases of the northern Great Plains. At least four cycles of breeding will probably be necessary to develop FHB‐resistant germplasm lines acceptable to producers and the malting and brewing industry.