bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural Stem Cells Express Non-Neural Markers During Embryoid Body Coculture
Authors: Denham Mark , Huynh Trieu , Dottori Mirella , Allen Greg , Trounson Alan , Mollard Richard
Published: October 2005

The capacity of neural stem cells (NSC) to transdifferentiate into a wide range of non-neuronal lineages is the subject of debate. One approach to test NSC plasticity is to ectopically place NSCs in permissive or instructive microenvironments in which the signals driving differentiation of multiple cell types are being elicited. Here we produce embryoid body neurosphere aggregates by combining neurosphere derivatives from fetal mice constitutively expressing green fluorescent protein with embryonic stem (ES) cells isolated from Zin40 mice constitutively expressing nuclear β-galacosidase. Under these conditions, we assess neurosphere-derivative–immunoreactivity to anti-neurofilament heavy chain, anti-pan-cytokeratin, anti-smooth muscle α-actinin and anti-α-fetoprotein–specific antibodies. Furthermore, we determine lineage-specific transgene expression and undertake fluorescence in situ hybridization to assess ES cell–neural stem cell–fusion indices. Our data demonstrate that following coculture in hanging drops with ES cells, neurosphere derivatives display immunoreactivity to non-neural markers, in particular smooth muscle, which is not dependent upon cell–cell fusion. These results suggest that given an appropriate environment, NSC may lose their in vivo restrictions and display non-neuronal phenotypes.
Human Bone Marrow Stromal Cells Express a Distinct Set of Biologically Functional Chemokine Receptors
Authors: Honczarenko Marek , Le Yi , Swierkowski Marcin , Ghiran Ionita , Glodek Aleksandra M. , Silberstein Leslie E.
Published: October 2005

Stromal cells isolated from bone marrow (BMSCs), often referred to as mesenchymal stem cells, are currently under investigation for a variety of therapeutic applications. However, limited data are available regarding receptors that can influence their homing to and positioning within the bone marrow. In the present study, we found that second passage BMSCs express a unique set of chemokine receptors: three CC chemokine receptors (CCR1, CCR7, and CCR9) and three CXC chemokine receptors (CXCR4, CXCR5, and CXCR6). BMSCs cultured in serum-free medium secrete several chemokine ligands (CCL2, CCL4, CCL5, CCL20, CXCL12, CXCL8, and CX3CL1). The surface-expressed chemokine receptors were functional by several criteria. Stimulation of BMSCs with chemokine ligands triggers phosphorylation of the mitogen-activated protein kinase (e.g., extracellular signal–related kinase [ERK]-1 and ERK-2) and focal adhesion kinase signaling pathways. In addition, CXCL12 selectively activates signal transducer and activator of transcription (STAT)-5 whereas CCL5 activates STAT-1. In cell biologic assays, all of the chemokines tested stimulate chemotaxis of BMSCs, and CXCL12 induces cytoskeleton F-actin polymerization. Studies of culture-expanded BMSCs, for example, 12–16 passages, indicate loss of surface expression of all chemokine receptors and lack of chemotactic response to chemokines. The loss in chemokine receptor expression is accompanied by a decrease in expression of adhesion molecules (ICAM-1, ICAM-2, and vascular cell adhesion molecule 1) and CD157, while expression of CD90 and CD105 is maintained. The change in BMSC phenotype is associated with slowing of cell growth and increased spontaneous apoptosis. These findings suggest that several chemokine axes may operate in BMSC biology and may be important parameters in the validation of cultured BMSCs intended for cell therapy.
Cultivation of Human Embryonic Stem Cells Without the Embryoid Body Step Enhances Osteogenesis In Vitro
Authors: Karp Jeffrey M. , Ferreira Lino S. , Khademhosseini Ali , Kwon Albert H. , Yeh Judy , Langer Robert S.
Published: October 2005

Osteogenic cultures of embryonic stem cells (ESCs) are predominately derived from three-dimensional cell spheroids called embryoid bodies (EBs). An alternative method that has been attempted and merits further attention avoids EBs through the immediate separation of ESC colonies into single cells. However, this method has not been well characterized and the effect of omitting the EB step is unknown. Herein, we report that culturing human embryonic stem cells (hESCs) without the EB stage leads to a sevenfold greater number of osteogenic cells and to spontaneous bone nodule formation after 10–12 days. In contrast, when hESCs were differentiated as EBs for 5 days followed by plating of single cells, bone nodules formed after 4 weeks only in the presence of dexamethasone. Furthermore, regardless of the inclusion of EBs, bone matrix formed, including cement line matrix and mineralized collagen, which displayed apatitic mineral (PO4) with calcium-to-phosphorous ratios similar to those of hydroxyapatite and human bone. Together these results demonstrate that culturing hESCs without an EB step can be used to derive large quantities of functional osteogenic cells for bone tissue engineering.
Weed Control for Tall Fescue Seed Production and Stand Duration without Burning
Authors: Mueller-Warrant George W. , Rosato S. Caprice
Published: October 2005

Effective weed control was a major concern of Oregon grass seed growers during their recent transition from open‐field burning to mechanical methods of managing post‐harvest residues. This 4‐yr herbicide by residue management study was conducted to determine: (i) efficacy of herbicides on volunteer tall fescue (Festuca arundinacea Schreb.) seedlings and other weeds, (ii) whether treatments required for weed‐free seed production could be reapplied annually without damaging stands, (iii) occurrence of interactions between herbicides and crop residue management, and (iv) increases in grassy weeds over time. Nearly all herbicide treatments controlled volunteer tall fescue seedlings with bale/flail chop/rake residue removal. Vacuum sweep residue removal improved control over bale/flail chop/rake in many cases, and controlled seedlings even without herbicides in 1995. Incorporation of pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl2,6‐dinitrobenzenamine] improved weed control in bale/flail chop/rake and residue‐retained conditions. Although carryover treatment effects reduced weed seedling survival in later years of production and sometimes reduced tall fescue seed yield, specific treatments existed which controlled weeds for all 4 yr without reducing yield. Interactions between residue management and herbicide treatments included reduced efficacy of pendimethalin in residue‐retained management, higher yields at equal weed densities in residue‐removed conditions, and higher weed densities from equivalent herbicide treatments in residue‐retained conditions. Roughstalk bluegrass (Poa trivialis L.) increased over time in some treatments and was a major cause for reduced yields in later years of production. Tall fescue seed growers must risk some current‐year yield loss from herbicide injury to avoid greater losses in future years from perennial weeds like roughstalk bluegrass.
Multilocation Annual Ryegrass Cultivar Performance over a Twelve‐Year Period
Authors: Redfearn Daren D. , Venuto Brad C. , Pitman W. D. , Blouin David C. , Alison M. W.
Published: October 2005

Systematic performance trials have been conducted in several states for more than 20 yr to evaluate agronomic performance of annual ryegrass (Lolium multiflorum Lam.). Despite development and testing of many annual ryegrass cultivars, the first improved cultivar, Gulf, has remained one of 10 to 12 cultivars recommended for planting in the southeastern USA. Our objectives were to evaluate cultivar yield performance across 12 yr at five locations, to assess cultivar yield distribution within growing seasons, and to estimate cultivar yield stability (consistency of relative performance environments). Efficacy measures were early‐season yield (total before 1 March), late‐season yield (total after 1 March), and total annual yield. Overall means for all cultivars and individual cultivar performance (for common years) were compared with Gulf or Marshall. Neither location effects nor cultivar × location interactions were found. Cultivar and year effects, plus cultivar × year interactions were detected (P < 0.05) for all three yield responses. Mean early season yields ranged from 2.3 to 4.6 Mg ha−1, with mean late‐season yields ranging from 5.1 to 7.4 Mg ha−1 No trend existed for mean total yield relative to Gulf or Marshall to increase over time in association with availability of newer cultivars. Given large yearly fluctuation in yields, it is apparent that unpredictable environmental factors, including climate and perhaps pests, are the primary determinants of annual ryegrass performance rather than differences in yield potential among cultivars. Thus, yield stability may be an appropriate selection factor to include among the criteria for development of improved annual ryegrass cultivars.
Molecular Marker Satt481 is Associated with Iron‐Deficiency Chlorosis Resistance in a Soybean Breeding Population
Authors: Charlson Dirk V. , Bailey Theodore B. , Cianzio Silvia R. , Shoemaker Randy C.
Published: October 2005

Soybean [Glycine max. (L.) Merr.] breeders have improved resistance to iron‐deficiency chlorosis (IDC) using conventional breeding approaches; however, many IDC‐resistant cultivars have lower yields compared to IDC‐susceptible cultivars. The importance of environment on IDC‐resistance expression hinders progress in breeding for resistance. An environment‐independent selection strategy, such as marker‐assisted selection (MAS), may increase breeding efficiency. Our objective was to determine whether simple sequence repeat (SSR) markers located in previously reported quantitative trait loci (QTL) for IDC resistance would be associated with IDC resistance in a breeding population. One‐hundred and eight SSR markers genetically linked to eight QTLs on eight molecular linkage groups (MLGs) previously identified for IDC were tested in a breeding population evaluated for IDC resistance on calcareous soils in Iowa. The breeding population was developed from a cross between Pioneer 9254 and A97–770012. The F2 lines were genotyped with markers and the F2–derived lines (F2:4 and F2:5) were evaluated for IDC resistance. Three markers were associated with IDC resistance: Satt211, Satt481, and Sat_104. However, of the three markers, only Satt481 was associated to IDC resistance across environments. Although Satt481 accounted for only 12% of the total phenotypic variation, molecular analysis of the eleven‐most resistant lines in the population indicated that 73% of the lines were homozygous for the resistant allele at the Satt481 locus. Our results indicated that Satt481 may be useful to improve IDC resistance in this soybean population and that additional QTLs conferring resistance to IDC might exist in soybean.
Inheritance of Resistance to Phomopsis Seed Decay in Soybean PI 80837 and MO/PSD‐0259 (PI 562694)
Authors: Jackson Eric W. , Fenn Patrick , Chen Pengyin
Published: October 2005

Phomopsis seed decay [PSD; caused by Diaporthe phaseolorum var. sojae (Lehman) Wehmeyer, Diaporthe phaseolorum (Cooke & Ellis) Sacc. var. caulivora Athow & Caldwell, and Phomopsis longicolla Hobbs) reduces quality of soybean [Glycine max (L.) Merr.] seed when moist conditions and warm temperatures occur during seed development and maturation. Control of PSD by genetic resistance has not been well explored. of the genotypes reported with PSD resistance, PI 417479 and PI 80837 have received the most study. The PSD‐resistant line MO/PSD‐0259 derives its resistance from PI 417479. Objectives of this research were to characterize the inheritance of PSD resistance in PI 80837 and to determine if it differs from resistance in MO/PSD‐0259. PI 80837 was crossed with PSD‐susceptible ‘Agripro 350’ (AP 350); PSD‐susceptible PI 91113; and with MO/PSD‐0259. Populations and lines were screened in the field, and Phomopsis infection was assayed by plating seed. Seed infection of reciprocal F1 plants of AP 350 × PI 80837 was not different from that of PI 80837. Data from F2 populations of AP 350 × PI 80837 and PI 91113 × PI 80837; and F2:3 lines from AP 350 × PI 80837 fit models for a single dominant gene in PI 80837 that confers PSD resistance. F2 population data from AP 350 × MO/PSD‐0259 also fit a model for single dominant gene resistance in MO/PSD‐0259, and data from an F2 population and F2:3 lines of PI 80837 × MO/PSD‐0259 fit a model for two different dominant genes. These results show that PSD resistance in PI 80837 is conferred by a single dominant gene under nuclear control that is different from the gene in MO/PSD‐0259.
Wind Effect on Corn Leaf Azimuth
Authors: Elmore Roger W. , Marx David B. , Klein Ralph G. , Abendroth Lori J.
Published: October 2005

Stalk breakage, greensnap, in pretassel corn (Zea maysL.) increases when leaf azimuths are parallel to extreme thunderstorm winds. Yet wind effect on leaf azimuth is unknown. Azimuths recorded north of east–west windbreaks changed from 185° to 195° (north = 0°/360°; east = 90°; etc.) as distance from windbreaks increased from 1.4 to 13.6Hin 1999 in north–south rows;His the average height of the tallest row of windbreak trees. Plants at 20 to 25Hare considered unsheltered. In 2000, leaf azimuth changed from 195° to 178° from 1.5 to 25Hin north–south rows. With higher wind speeds and east–west rows in 2002, azimuths ranged 194° to 202° from 3.7 to 23H.In east–west rows windbreak sheltered leaves were oriented in north–south patterns. In contrast, unsheltered plants had few leaves pointing southward. Early‐season wind altered corn leaf azimuth. This affects greensnap tolerance and perhaps other physiological traits.
Heterosis and Combining Ability for Maize Adaptation to Tropical Acid Soils: Implications for Future Breeding Strategies
Authors: Welcker C. , Thé C. , Andréau B. , De Leon C. , Parentoni S. N. , Bernal J. , Félicité J. , Zonkeng C. , Salazar F. , Narro L. , Charcosset A. , Horst W. J.
Published: October 2005

Soil acidity reduces maize (Zea mays L.) yields by up to 70% on 8 million hectares in developing countries. Several breeding programs have produced populations better adapted to these conditions. The objectives of this study were to evaluate these populations for both per se cultivation and the development of new breeding germplasm. To do so, we generated a diallel cross design, which included six acid soil‐tolerant and five susceptible populations with high yield potential or tolerance to other stresses. Populations and crosses were evaluated in five environments, on acidic Al‐toxic soils and in comparable limed soils in Guadeloupe, Cameroon, and Colombia. Soil acidity decreased grain yield by 46 to 73%, depending on the location and year. Significant genotype × soil condition interactions were observed for grain yield. Mid‐parent heterosis for yield was significantly higher in acid soils (32%) than in nonacid soils (20%). This suggests that the development of variety crosses between acid soil‐tolerant populations could be used to increase maize yields in acid‐soil cropping systems. The observed high general combining ability (GCA) for yield variation of the crosses in acid soil and its close relationship to per se performance suggest that parental populations of variety crosses could be efficiently screened on the basis of per se performance in acid soil.
Leaf and Stem Characteristics of Timothy Plants Divergently Selected for the Ratio of Lignin to Cellulose
Authors: Claessens Annie , Michaud Réal , Bélanger Gilles , Mather Diane E.
Published: October 2005

Improved dry matter (DM) digestibility of herbage can be due to changes in fiber composition of leaves and/or stems, and/or to changes in the proportion of leaves and stems in the herbage. Previously, we reported that divergent selection for the ratio of acid detergent lignin (ADL) to cellulose (ADL/CEL) led to differences in timothy (Phleum pratense L.) DM digestibility. Here, we examined plant morphology (leaf‐to‐stem ratio, plant height and area, and stem diameter), leaf and stem fiber composition, and leaf and stem digestibility in timothy genotypes selected for high or low values of ADL/CEL and in divergent progeny populations derived from these selections. Parental genotypes and their progeny populations were field grown for 2 yr, and measurements were taken at the first harvest of each year. Selection for low values of ADL/CEL reduced ADL and neutral detergent fiber (NDF) concentrations in stems and increased the in vitro true digestibility (IVTD) of stems but had no consistent direct effects on plant morphology or leaf characteristics. Averaged over 2 yr, stems of the low‐ADL/CEL group of genotypes had lower ADL and NDF concentrations (by 3.4 and 12 g kg−1 DM, respectively) and a higher IVTD value (by 22 g kg−1 DM) than those of the high ADL/CEL group of genotypes. In addition, stems of the low‐ADL/CEL progeny population had lower ADL and NDF concentrations (by 4.2 and 26 g kg−1 DM, respectively) and a higher IVTD value (by 22 g kg−1 DM) than those of the high ADL/CEL progeny population. Thus, the observed changes in overall herbage DM digestibility due to selection for this ratio can be attributed mainly to modification of stem digestibility.
Quantitative Trait Loci Conferring Resistance to Fall Armyworm and Southwestern Corn Borer Leaf Feeding Damage
Authors: Brooks Thomas D. , Willcox Martha C. , Williams W. Paul , Buckley Paul M.
Published: October 2005

Southwestern corn borer (Diatraea grandiosella Dyar) and fall armyworm [Spodoptera frugiperda (J.E. Smith)] damage ratings were measured on an F2‐derived maize (Zea mays L.) population segregating for leaf feeding resistance following artificial infestation with neonates. Damage ratings for each insect were recorded in replicated trials at three locations and used in conjunction with a genetic linkage map to identify quantitative trait loci (QTL) associated with resistance. Significant QTL and their interactions were estimated by multiple interval mapping analysis. Resistance to southwestern corn borer leaf feeding was fit to a model containing eight QTL and two interactions explaining 20% of the phenotypic variation. A model containing seven QTL and one interaction best fit resistance to fall armyworm leaf feeding damage, and it explained approximately 14% of the phenotypic variation. Three QTL located on chromosomes 6, 9, and 10 affect leaf feeding damage ratings of both insects with similar effects and gene action. Minor interaction effects were observed. The QTL on chromosomes 1, 5, and 9 correspond to previously identified regions affecting resistance to southwestern corn borer. Insect resistance genes including the mir family of genes located on chromosome 6 and the glossy15 locus on chromosome 9 fall within chromosomal regions of QTL predicted in this study. This study confirms that resistance to fall armyworm and southwestern corn borer involves many of the same QTL and candidate genes for insect resistance include the glossy15 candidate locus on chromosome 9.
Population Genetic Diversity in a Maize Reciprocal Recurrent Selection Program
Authors: Hinze Lori L. , Kresovich Stephen , Nason John D. , Lamkey Kendall R.
Published: October 2005

The genetic structures of the Iowa Corn Borer Synthetic #1 (CB) and Iowa Stiff Stalk Synthetic (SS) maize (Zea mays L.) populations are important because these populations serve as the model for development of modern commercial hybrids. In 1949, CB and SS were used to start a reciprocal recurrent selection (RRS) breeding program at Iowa State University. This study was conducted to analyze more thoroughly the genetic diversity within this RRS program and illustrate how the RRS program has changed over time at the molecular level. The progress of this program was measured by analyzing the variation at 86 SSR loci among 28 progenitor lines and 30 plants sampled from each of seven cycles (Cycle 0, Cycle 1, Cycle 3, Cycle 6, Cycle 9, Cycle 12, and Cycle 15) in each population. The progenitors of these populations show a high amount of variation on the basis of expected heterozygosity (0.557). As the RRS program proceeded, this variation decreased (Cycle 15, 0.245). In total, a larger amount of genetic variation was found among plants within cycles (66%) than among cycles (13%) or between populations (21%). The repartitioning of variation from within populations (96% in progenitors) to between populations (58% in Cycle 15) over time is consistent with theoretical expectations of divergence between the populations. By sampling intermediate time points, we gained a comprehensive genetic view of CB and SS permitting evaluation of the molecular‐level changes occurring as a result of reciprocal recurrent selection.
Differential Adaptation of CIMMYT Bread Wheat to Global High Temperature Environments
Authors: Lillemo M. , van Ginkel M. , Trethowan R. M. , Hernandez E. , Crossa J.
Published: October 2005

A good understanding of the target environment and the extent of genotype × environment (G × E) interaction is essential for all cereal breeding programs. Differential adaptation of bread wheat (Triticum aestivum L.) to various heat‐stressed environments around the world was analyzed by cumulative cluster analysis of locations and genotypes in 9 yr of CIMMYT's High Temperature Wheat Yield Trial (HTWYT). The grouping pattern of yield‐testing environments could largely be explained by the temperature at different growth stages and relative humidity at booting. A clear distinction was observed between sites with heat stress and more temperate locations, and the heat‐stressed environments could be grouped into sites experiencing high temperature throughout the season and sites with more specific terminal heat stress. In addition, dry and humid heat‐stressed locations tended to differentiate. The ability of individual locations to predict yield in different heat‐stressed environments was studied by the shifted multiplicative model (SHMM) site clustering method, and identified locations like Tandojam (Pakistan), which associated well with both heat‐stressed and temperate environments. The good ability of the January planting date in Ciudad Obregon (Mexico) to predict yield performance in many heat‐stressed environments was also confirmed. Genotypes grouped according to their relative performance in different locations, and specific adaptation to the various types of heat‐stressed environments was apparent. However, a subset of genotypes was identified that showed stable, and high yield across all types of environments, both heat‐stressed and temperate.
Hierarchical Analysis of Switchgrass Morphology
Authors: Boe Arvid , Casler Michael D.
Published: October 2005

Switchgrass (Panicum virgatum L.) has potential as a biomass crop in North America. Our objective was to determine effects of cultivar and location on morphological traits that influence biomass in switchgrass. Six cultivars with origins from 37° N, 88° W (Cave‐In‐Rock and Shawnee) to 46° N, 100° W (Dacotah) were evaluated in 1‐yr‐old swards at Bristol and South Shore, SD; in 3‐yr‐old swards at Brookings, SD, and Arlington, WI; and in 15‐yr‐old swards at Pierre, SD, for biomass; tillers m−2; reproductive tiller proportions by count and weight; weight tiller−1; phytomers tiller−1; leaf, stem, and inflorescence components of tiller weight; and sheath and stem components of phytomer weight. Biomass production was related to region of cultivar origin [e.g., Shawnee produced two times more than Dacotah (6.2 Mg ha−1)]. Tiller density was highest for Dacotah (1090 tillers m−2) and lowest for Cave‐In‐Rock (520 tillers m−2). Reproductive tiller fractions by count were plastic and higher at Arlington (0.81) than Brookings (0.08). Weights per reproductive tiller ranged from 0.7 g (Dacotah) to 3.4 g (Cave‐In‐Rock). Phytomers per tiller was not plastic (5.2 for Dacotah to 7.4 for Cave‐In‐Rock). Internode weight exhibited a basipetal increase and was highly plastic. Cultivars responded similarly to location effects on tillers m−2, weight tiller−1, and biomass production. Cultivar differences for biomass production were attributed to variation at tiller (phytomers tiller−1) and phytomer (weight phytomer−1) levels.
No Evidence for Epistasis in Hybrid and Per Se Performance of Elite European Flint Maize Inbreds from Generation Means and QTL Analyses
Authors: Mihaljevic Renata , Utz H. Friedrich , Melchinger Albrecht E.
Published: October 2005

Favorable epistatic gene complexes may be important for hybrid performance of maize (Zea mays L.). This study was conducted to assess the importance of epistasis in per se and testcross performance for grain yield and grain moisture in four crosses among four elite European flint maize lines by generation means analyses as well as genome‐wide tests for significant digenic epistatic effects between marker loci. For each cross, six generations (P1, P2, F1, F2, BC1, BC2) and testcrosses of these generations plus the F2–Syn1, F2–Syn2, and F2–Syn3 generations in combination with an unrelated dent tester were evaluated in four environments. Testcross generation means of P, BC, F1, F2, F2–Syn1, F2–Syn2, and F2–Syn3 did not significantly differ from each other for grain yield and grain moisture, indicating that epistasis between unlinked and moderately linked loci was negligible in its net effect. Depending on the cross, QTL mapping for per se and testcross performance with the dent tester was conducted with 71 to 344 lines (F3 to F6) grown in four environments. In genome‐wide two‐way ANOVAs, significant epistatic interactions were found with only a few marker pairs that did not improve the fit of the model after including main‐effect QTLs previously detected by composite interval mapping. Poor correspondence of the results from per se and testcross analyses reflects dominance and epistatic interactions between parental and tester alleles. Our results suggest that epistasis is of minor importance for both traits with regard to the optimum type of population (F2 vs. BC) in recycling breeding of elite maize inbreds. Estimates of digenic epistasis detected with genome‐wide tests must be treated with caution because of the problems associated with model selection in QTL mapping with the sample sizes commonly used.
Identification of QTL Associated with White Mold Resistance in Common Bean
Authors: Ender Marcio , Kelly James D.
Published: October 2005

White mold, caused by the necrotrophic fungusSclerotinia sclerotiorum(Lib.) de Bary, is a serious disease of common bean (Phaseolus vulgarisL.). The use of resistant cultivars is the preferred control strategy, but the approach has been difficult to implement because of quantitative nature of genetic resistance to white mold. The objectives of this study were to identify quantitative trait loci (QTL) associated with resistance toS. sclerotiorum, identify QTL associated with agronomic traits that contribute to white mold avoidance, and locate putative QTL on the integrated bean map. Bulked segregant analysis using multiple trait bulks that included disease severity index (DSI), yield, and days to flower was used to detect QTL associated with field resistance to white mold in a Middle American recombinant inbred line (RIL) population of common bean. QTL that accounted for 9.2 to 14.7% of the phenotypic variation for DSI were located on linkage groups B2, B5, B7, and B8 of the integrated bean map. In addition, QTL were detected for seed size and yield and agronomic traits associated with disease avoidance: days to maturity, days to flower, and lodging. Heritability estimates for DSI were moderate (0.41) and correlations with agronomic traits that included lodging (0.56**), architecture (0.35**), canopy height (−0.33**), and yield (−0.64**) support the importance of these traits in disease avoidance. Data from the current study provides breeders with critical information on which traits and genomic regions to target as part of an overall strategy to enhance resistance to white mold in common bean.
Nitrogen Fixation, Amino Acid, and Ureide Associations in Chickpea
Authors: Thavarajah Dil , Ball Rosalind A. , Schoenau Jeff J.
Published: October 2005

The metabolic products of nitrogen fixation (N2) in a legume can be either amides (asparagine, glutamine) or ureides (allantoin and allantoic acid), which are then exported to the shoot via the xylem. Ureides are synthesized solely in the nodules. Chickpea (Cicer arientinum L.) has been separately classified as an amide and as a ureide exporter; however, the exact shoot metabolic products resulting from N2 fixation are not known. The objectives of this study were (i) to determine the metabolites of N2 fixation, namely free amino acids and ureides and (ii) to quantify the differences in N2 fixation for chickpea cultivars in the field by 15N natural abundance. Leaf ureide concentrations were analyzed at Weeks 6, 7, 8, 9, 10, and 11 after emergence. Free amino acid concentrations were analyzed at Weeks 7, 9, and 11 after emergence. Flax (Linum usitatissimum L., CDC‐Bethune) was used as the reference crop for assessment of percentage nitrogen derived from the atmosphere. Two chickpea cultivars, CDC‐Anna and Myles, had significantly higher N2 fixation than the other three tested cultivars. Myles also maintained ureides and amides at a moderate concentration from flowering through reproductive growth. Overall, we found that asparagine and alanine were the major free amino acids, along with ureides, representing likely metabolites from N2 fixation. Therefore, chickpea should be classified as both an amide and ureide exporter, on the basis of the concentration of both types of N product found in the shoot.
Heterosis and Combining Ability in a Diallel Cross of Ethiopian Mustard Inbred Lines
Authors: Teklewold Adefris , Becker Heiko C.
Published: October 2005

Heterosis is commercially exploited in rapeseed (Brassica napus L.) and its potential use has been demonstrated in turnip rape (B. rapa L.) and Indian mustard (B. juncea L.). In Ethiopian mustard (B. carinata A. Braun), however, information regarding heterosis has not been previously reported. This study, therefore, was conducted to generate information on heterosis and combining ability in B. carinata Nine inbred parents and their 36 F1s, obtained by half‐diallel cross, were evaluated for 12 traits at three locations in Ethiopia. Analysis of variance showed the presence of significant heterosis for all the traits. Seed yield showed the highest relative mid‐parent heterosis that varied from 25 to 145% with a mean of 67%. Relative high‐parent heterosis for seed yield varied from 16 to 124% with a mean of 53%. General combining ability (GCA) effects were predominant in all traits except secondary branches and pods per plant. Specific combining ability (SCA) was significant for days to flowering, secondary branches, pods per plant, pod length, seeds per pod, 1000‐seed weight and oil content. Interaction effects of GCA × location were significant for all traits except days to flowering, days to maturity, and oil content. All traits had significant SCA × location interaction effects. GCA effect for seed yield was positively correlated with F1 performance (r = 0.77) and absolute mid‐parent heterosis (r = 0.67). The presence of high levels of mid‐ and high‐parent heterosis indicates a considerable potential to embark on breeding of hybrid or synthetic cultivars in Ethiopian mustard.
Characterization of Resistance to Soybean mosaic virus in Diverse Soybean Germplasm
Authors: Zheng C. , Chen P. , Gergerich R.
Published: October 2005

Soybean mosaic virus (SMV) causes one of the most destructive viral diseases in soybean [Glycine max (L.) Merr.] worldwide. Ninety‐eight SMV isolates identified in the USA have been classified into seven strain groups (G1–G7). Three independent loci (Rsv1, Rsv3, and Rsv4) have been identified for SMV resistance. Multiple resistance alleles have been reported for the Rsv1 and Rsv3 locus. The objective of this research was to group diverse soybean genotypes on the basis of their differential reactions to SMV strains. SMV strains G1 and G7 were used to characterize the reactions of 212 soybean genotypes to SMV. Fifty‐five genotypes were resistant to G1 but susceptible to G7, and virus was detected in G7‐inoculated plants. Thirty‐one genotypes were resistant to G1 but exhibited stem‐tip necrosis following G7 inoculation. These 86 soybean genotypes presumably carry alleles at the Rsv1 locus. Thirty‐seven genotypes were resistant to G1 and G7, and SMV was not detected by ELISA, indicating that they probably carry Rsv4, Rsv1‐r, or Rsv1‐h or a combination of two resistance genes Rsv1Rsv3, Rsv1Rsv4, or Rsv3Rsv4. Seven genotypes were susceptible to G1 but resistant to G7 and may carry alleles at the Rsv3 locus. PI 507389 and PI 61944 developed stem‐tip necrosis after inoculation with G1 and a mosaic symptom when inoculated with G7, indicating that PI 61944 may carry the same Rsv1‐n gene as PI 507389. Eighty soybean accessions developed mosaic symptoms when inoculated with G1 or G7 because of the lack of SMV resistance genes. The information from this research will be helpful in selecting SMV‐resistant parents for crossing in a breeding program.
Forage Yield of Smooth Bromegrass Collections from Rural Cemeteries
Authors: Casler M. D. , Brummer E. C.
Published: October 2005

Smooth bromegrass (Bromus inermis Leyss) is poorly adapted to management‐intensive rotational grazing because of slow and limited regrowth potential. In an effort to discover germplasm with tolerance to frequent cutting, smooth bromegrass plants were collected from fence and sod habitats of 30 rural cemeteries in Iowa, Minnesota, and Wisconsin. The objective of this study was to quantify, describe, and test the responses of paired fence and sod populations to different harvest frequencies. Thirty sod populations, 30 fence populations, and five cultivars were evaluated for season‐total forage yield and regrowth percentage at Arlington, WI, and Ames, IA. Three harvest managements were used, with mean harvest frequencies of four, five, or six harvests over 2002 and 2003. Fence populations had an average forage yield 5.5% higher than sod populations, a difference that was fairly consistent across harvest managements, test locations, and state of origin. Variation in linear responses to harvest management made up 65 and 77% of the harvest management × population interaction for forage yield and regrowth percentage, respectively. For seven cemetery sites, the sod population was better adapted than the fence population to a more frequent harvest management, as measured by a more stable response to harvest frequency (−2.02 ± 0.10 vs. −2.67 ± 0.12 Mg ha−1 harvest−1). For nine cemetery sites, the sod population had a higher increase in regrowth percentage with increased harvest frequency (15.8 ± 0.5 vs. 11.9 ± 0.7% units harvest−1). Smooth bromegrass germplasm from some cemetery sods appears to have potential value for developing tolerance to frequent defoliation.
Carbon Isotope Discrimination Accurately Reflects Variability in WUE Measured at a Whole Plant Level in Rice
Authors: Impa S. M. , Nadaradjan S. , Boominathan P. , Shashidhar G. , Bindumadhava H. , Sheshshayee M. S.
Published: October 2005

Water use efficiency (WUE) is physiologically linked to discrimination of the stable isotope of carbon (Δ13C) in leaves of plant species. We determined the genetic variability in WUE by gravimetric approach and Δ13C among 34 diverse germplasm accessions of rice (Oryza sativa L.). The leaf Δ13C ranged between 18.7 and 21.6‰, representing a significant variability and showed a strong inverse relationship with WUE. The gravimetrically determined WUE represents time integrated values, and hence its regression with Δ13C strongly proves the relevance of Δ13C as a surrogate for WUE in rice. For a trait to be successfully exploited for crop improvement, it should have low genotype × environment (G × E) interaction. Six contrasting genotypes selected and examined in a separate experiment showed good correspondence in both WUE and Δ13C between the experiments indicating that WUE is genetically controlled in rice and hence can be exploited through breeding. A prior knowledge on the constituent physiological factors controlling WUE is an important prerequisite for exploiting this trait in crop improvement programs. An inverse relationship between WUE and mean transpiration rate (MTR) indicates a stomatal control of WUE among rice genotypes. Although total biomass normally decreases while selecting for high WUE from among conductance types, a few promising genotypes with high WUE coupled with moderately high total biomass can still be identified for further crop improvement.
Distribution and Mobilization of Sulfur during Soybean Reproduction
Authors: Naeve Seth L. , Shibles Richard M.
Published: October 2005

Soybean [Glycine max (L.) Merr.] seed protein is deficient in the essential sulfur‐containing amino acids, methionine, and cysteine. Transgenic approaches to increase coding for these amino acids have not been particularly fruitful. Little is known about the relative importance of S stored in vegetative tissues for seed protein synthesis. This study was conducted to secure data on sulfur (S) uptake, distribution, and mobilization patterns in the reproductive phase of soybean grown under S sufficient conditions. Soybean plants were grown in hydroponic culture and pulsed with 35S labeled SO4 at several discrete stages during the reproductive phase of development. Sequential harvest of plants indicated where and how S is stored and mobilized during reproduction in soybean. Leaves supplied developing soybean seed with approximately 20% of its S requirement. Distribution of newly acquired S within plants changed through reproductive development; however, leaves mobilized S with a similar efficiency through R5.5. Expanding leaves take up disproportionately large quantities of S; however, leaf tissue seems dependent on newly acquired S, and is unable to utilize stored SO4 Pods play an important role in S storage and mobilization to seed. In contrast to the leaf fraction, expanding pods were able to utilize stored S. Pods and seeds seem dependent on mobilized S. This study demonstrates that developing soybean seeds are dependent on S that has been mobilized from other plant tissues.
Genome Size Analysis of Weedy Amaranthus Species
Authors: Rayburn A. Lane , McCloskey R. , Tatum Tatiana C. , Bollero German A. , Jeschke Mark R. , Tranel Patrick J.
Published: October 2005

Weedy Amaranthus species pose a serious threat to agriculture. One of the areas that causes the greatest concern is development of herbicide resistance and subsequent transfer of herbicide resistance genes among the species. To determine the potential impact of interspecific hybridization, one must first be able to detect such hybrids. To determine if genome size could be useful in the detection of interspecific hybrids among the weedy Amaranthus species, the genome sizes of the weedy Amaranthus species sympatric in Illinois were analyzed. In a series of experiments, the genome sizes of these species were determined by flow cytometric analysis. A significant variation was observed with respect to nuclear DNA content in the eight species examined. The genome sizes ranged from ≈0.95 pg in A. palmeri to ≈1.4 pg in A. tuberculatus Overlap of genome sizes among the species does exist; however, due to the reproductive biology of the species, this overlap does not preclude the detection of interspecific hybrids. Any dioecious weedy Amaranthus plant in Illinois that has a genome size between 1.3 pg and 1.1 pg is probably a hybrid. Thus, the potential for genome size determination to reveal interspecific hybrids among weedy Amaranthus species has been demonstrated.
Quantitative Trait Loci for Multiple Disease Resistance in Wild Barley
Authors: Yun S. J. , Gyenis L. , Hayes P. M. , Matus I. , Smith K. P. , Steffenson B. J. , Muehlbauer G. J.
Published: October 2005

Foliar diseases of barley (Hordeum vulgare L.) such as spot blotch [caused by Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dastur], net type net blotch (NTNB; caused by Pyrenophora teres f teres Drechs), Septoria speckled leaf blotch (SSLB; caused by Septoria passerinii Sacc.), leaf scald [caused by Rhynchosporium secalis (Oudem.) J. J. Davis], and powdery mildew (caused by Blumeria graminis f. sp. hordei Em. Marchal) can result in significant yield reductions in many production areas. The wild progenitor of cultivated barley, Hordeum vulgare subsp. spontaneum is well known as a rich source of disease resistance. To determine the location of H. vulgare subsp. spontaneum‐derived alleles for disease resistance, we conducted quantitative trait locus (QTL) analysis of a recombinant inbred line (RIL) population derived from a cross between the resistant H. vulgare subsp. spontaneum accession OUH602 and the two‐rowed malting cultivar Harrington. A total of 151 simple sequence repeats (SSR) markers were mapped into 11 linkage groups, covering 948 cM. Major QTLs for resistance to each disease were identified: one for spot blotch resistance on chromosome 1(7H); three for NTNB resistance on chromosomes 3(3H), 4(4H), and 5(1H); two for SSLB resistance on chromosomes 2(2H) and 6(6H); one for leaf scald resistance on chromosome 5(1H); and two for powdery mildew resistance on chromosomes 4(4H) and 5(1H). Resistance alleles for each QTL were contributed by OUH602, except those for NTNB and powdery mildew resistance on chromosome 5(1H) and chromosome 4(4H), respectively. The two QTLs identified for SSLB resistance are novel. All other QTLs mapped to regions where known resistance QTLs or major resistance genes have been reported. Our results indicate that most of the OUH602‐derived loci are clustered in regions coincident with those described in cultivated barley. These resistance QTLs and their associated markers should be valuable for further exploitation of disease resistance variation in barley improvement.
Genetic Diversity among CIMMYT Maize Inbred Lines Investigated with SSR Markers: II. Subtropical, Tropical Midaltitude, and Highland Maize Inbred Lines and their Relationships with Elite U.S. and European Maize
Authors: Xia X. C. , Reif J. C. , Melchinger A. E. , Frisch M. , Hoisington D. A. , Beck D. , Pixley K. , Warburton M. L.
Published: October 2005

Characterization of genetic diversity of maize (Zea mays L.) germplasm is of great importance in hybrid maize breeding. The objectives of this study were to (i) investigate genetic diversity in CIMMYT subtropical, tropical midaltitude and highland inbreds with simple sequence repeat (SSR) markers, (ii) identify appropriate testers for the development of new inbred lines, (iii) compare this sample to U.S. and European elite maize lines and CIMMYT tropical lowland inbreds, and (iv) use the marker and pedigree information as a guide to understanding the heterotic relationship among the CIMMYT maize lines (CMLs) and their potential practical use in maize breeding programs worldwide. Inbreds included in the study were assayed with 79 SSR markers. The CIMMYT inbred lines originated from 35 mostly broad‐based populations and pools with mixed origins. A total of 566 alleles were scored, (averaging 7.2 and ranging from 2 to 16 alleles per locus). The modified Roger's distance (MRD) between pairs of inbreds averaged 0.78, with a range of 0.45 to 0.93. Unweighted paired group method using arithmetic averages (UPGMA) cluster analysis revealed no clear clustering. This reflects a mixed composition of CIMMYT subtropical, tropical midaltitude and highland maize populations and pools, and indicates that large amounts of variation have been incorporated into CIMMYT germplasm. Temperate heterotic groups were separated based on the markers, and nontemperate CIMMYT maize was genetically distinct from temperate lines. Discrete clusters were difficult to identify within and often between megaenvironments. Specific recommendations for nontemperate hybrid maize breeding are made.
AFLP Diversity within and among Hardinggrass Populations
Authors: Mian M. A. Rouf , Zwonitzer John C. , Chen Yiwu , Saha Malay C. , Hopkins Andrew A.
Published: October 2005

Little information is available on the genetic diversity of hardinggrass (Phalaris aquatica L.), a cool‐season forage grass with potential for use in the southern Great Plains. The objective of this study was to determine the genetic diversity within and among 22 promising hardinggrass populations, including plant introductions (PIs), breeding populations, and one cultivar. Nine plants from each population (198 genotypes) were characterized with amplified fragment length polymorphism (AFLP) markers. Genotypes were evaluated with nine selective primer combinations of fluorescent‐labeled PstI and MseI primers, producing a total of 961 useful AFLP fragments. A high degree of genetic diversity was found, with a greater proportion of the diversity within (74%) rather than among (26%) populations. Clustering of populations on the basis of UPGMA closely followed the geographic origin and breeding history of the populations. Selections led to genetic shifts between two breeding populations, HG PI C1 and HG PI C2, although genetic diversity changed little if at all within these populations on the basis of polymorphism information content (PIC) scores of 0.22 versus 0.19, respectively. Two Moroccan PIs (PI 240248 and PI 517026) represent a distinct germplasm source on the basis of their genetic distances from other populations in the study. Genetic diversity data from this study will be helpful in grouping these accessions for development of breeding populations and various research purposes.
Soil Water Retention
Authors: Haverkamp R. , Leij F. J. , Fuentes C. , Sciortino A. , Ross P. J.
Published: October 2005

Knowledge of soil water retention is fundamental to quantify the flow of water and dissolved substances in the subsurface. Water retention is often quantified with models fitted to observed retention points. Interpretation and conversion of parameters from different models is subjective and prone to error. We examined 461 retention curves from the UNSODA database and 660 from the GRIZZLY database. Parameters of the Brooks‐Corey (BC) and van Genuchten (vG) equations were fitted to the retention data. The shape parameters in these functions (λ, m, and n) are closely correlated to soil texture and may be predicted with so‐called pedotransfer functions (PTFs). Among the scale parameters, the saturated water content θs proved to be a robust fitting parameter regardless of parameterization. Reliable optimization of the residual water content θr is more difficult; without any constraint it was negative for 54.4% of the GRIZZLY samples, and its value was strongly correlated to the shape parameters. The BC‐ and vG‐shape parameters are often converted assuming λ = mn, which is incorrect when λ or mn is large (e.g., λ > 0.8). To facilitate the interpretation, conversion, and optimization of retention parameters, we introduce a water retention shape index P This index constitutes an integral measure of the slope of the retention curve and characterizes the retention behavior of a particular soil with a single number. A value for the index can be estimated directly from retention data. For the majority of the samples P ranged between 0 and 0.4; rarely did P exceed 3, which is the maximum expected for fractal behavior. The value for P was related to soil texture: fine‐textured soils tend to have smaller values than coarse‐textured soils. The shape index provides a benchmark for conversion and comparison of parameters.