bluuebunny/crossref_metadata_2025 huggingface dataset:
Soybean Yield Partitioning Changes Revealed by Genetic Gain and Seeding Rate Interactions
Authors: Suhre Justin J. , Weidenbenner Nicholas H. , Rowntree Scott C. , Wilson Eric W. , Naeve Seth L. , Conley Shawn P. , Casteel Shaun N. , Diers Brian W. , Esker Paul D. , Specht James E. , Davis Vince M.
Published: July 2014

Soybean [Glycine max (L.) Merr.] yield has increased during the past century; however, little is understood about the morphological parameters that have contributed most to yield gain. We conducted field studies to determine relationships between genetic gain of soybean yield and seeding rate. The hypothesis was newer cultivars would express higher yield than older cultivars when grown in higher plant populations. A total of 116 soybean cultivars equally representing Maturity Groups (MGs) II and III released over the last 80 yr were evaluated at high and low seeding rates in Wisconsin, Minnesota, Illinois, and Indiana. Seeding rates were 445,000 and 148,000 seeds ha−1 resulting in 311,000 and 94,000 plants ha−1 (high and low, respectively). Seed yield was greater for the high seeding rate vs. low seeding rate throughout all cultivars and years of release, but the difference was larger in newer cultivars. The differences observed primarily came from an increased number of pods and seeds plant−1. However, newer cultivars grown in low seeding rates increased per plant yield linearly by 0.118 (± 0.02)x– 208.0 g plant−1, where x = year‐of‐release, which was three times greater than at the high seeding rate. The greater yield trend came from seeds produced on plant branches. Therefore, newer cultivars produce more compensatory yield on plant branches under lower plant populations than older cultivars, so over the last 80 yr there has been a diminishing response to the expected yield penalty from reduced plant density.
Boll Retention and Boll Size among Intrasympodial Fruiting Sites in Cotton
Authors: Boquet Donald J. , Moser Edgar Barry
Published: July 2014

Competition among cotton (Gossypium hirsutum L.) bolls for assimilates may affect boll retention and size, making it an important factor affecting productivity. A 4‐yr field study was conducted on Commerce silt loam to evaluate relationships among fruiting sites (FS) on sympodial branches of cotton receiving preplant fertilizer N rates of 0, 28, 56, 84, 112, 140, or 168 kg ha−1 or a preplant + sidedress application of 56 + 56 kg ha−1 each year. For each FS on each sympodium, there were four possible competition levels based on boll retention or abscission at FS 1, 2, and 3. Competition levels were determined by natural retention or abscission of fruit. Boll retention and weight were influenced by competition level, year, sympodia, FS location on the sympodia and by N rate. Competition effects on boll retention were affected by N rate but not by sympodia. Conversely, competition effects on boll weight were not affected by N rate but were affected by sympodia. Boll weight at FS 1 increased when bolls were retained at FS 2 and 3. Retention of a boll at FS 1 increased boll retention at FS 2 but decreased boll weight at FS 2. In contrast, boll weight at FS 2 increased when bolls were retained at FS 3, or at FS 1 and 3. Fertilizer N increased boll weight at FS 2, except when a competing boll was present at FS 1. Apparent increased competition among FS on a sympodium had favorable effects on boll retention and on boll weight except for FS 2 when FS 1 retained a boll and FS 3 did not retain a boll.
Tillage and Seeding Rate Effects on Wheat Cultivars: II. Yield Components
Authors: Carr Patrick M. , Horsley Richard D. , Poland Woodrow W.
Published: July 2014

Tillage is declining in dryland wheat production systems. Our objectives were to determine if tillage × cultivar, seeding rate × cultivar, and tillage × seeding rate × cultivar interactions occurred for the yield components of hard red spring wheat (Triticum aestivum L. emend. Thell.) in a wheat–fallow monoculture. The cultivars AC Minto, Amidon, Bergen, Grandin, and Norm were seeded at 123, 247, and 371 kernels m−2 in conventional‐till (CONT), reduced‐till (RT), and no‐till (NT) systems in a randomized complete block in a split‐split plot arrangement during 1995–1998. Tillage × cultivar and tillage × seeding rate × cultivar interactions did not occur for any yield component (P > 0.05). A seeding rate × cultivar interaction occurred for both plant stand and tiller production, but the interaction resulted from a change in the magnitude of response and not in the ranking of cultivars to seeding rate adjustments for either yield component. Plant stand and the number of tillers per plant were unaffected by tillage systems, but the number of spike‐bearing tillers increased from 411 m−2 under CONT to 457 m−2 under NT. Tillage systems did not affect the number of kernels per spike or kernel weight. More spike‐bearing tillers per square meter occurred as the seeding rate increased, but there were fewer tillers per plant and a negative quadratic response in the number of kernels per spike. Results of this study indicate that the ranking of contrasting hard red spring wheat cultivars for yield components is unchanged by reductions in tillage in a wheat‐fallow monoculture.
Summer Root Decline: Production and Mortality for Four Cultivars of Creeping Bentgrass
Authors: Huang Bingru , Liu Xiaozhong
Published: July 2014

A better understanding of the seasonal dynamics of root activity for creeping bentgrass [Agrostis palustris Huds. = A stolonifera var. palustris (Huds.) Farw.] would be beneficial for developing effective breeding and management programs to maximum summer turf quality. The objectives of this study were to examine dynamics changes in root production and mortality for four creeping bentgrass cultivars that differ in summer shoot performance. The study was conducted on a USGA‐specification putting green in Manhattan, KS, during 1997 and 1998. The cultivars evaluated were ‘L‐93’, ‘Penncross’, ‘Providence’, and ‘Crenshaw’. Grasses were mowed daily at 4 mm and irrigated on alternate days. Root production and mortality were monitored using the minirhizotron technique. In both years, total root length and number were highest in August and then decreased in September for all four cultivars. From July to September, the length and number of newly produced roots decreased while those of dead roots increased. The ratio of dead roots to live roots in length and number increased in late summer for all cultivars. While the differences in total root length and number among cultivars were not consistent between 2 yr, Penncross consistently had more dead roots, fewer new roots, and higher root mortality compared with the other cultivars. The results indicate that summer root decline of creeping bentgrass resulted from both decreased new root production and increased root mortality, which could be associated with high soil temperatures during the summer. Variation in root production and mortality may contribute to the differences in shoot summer performance of the four cultivars.
Extractable Soil Phosphorus Concentrations and Creeping Bentgrass Response on Sand Greens
Authors: Guillard Karl , Dest William M.
Published: July 2014

Few studies have directly related turfgrass growth and quality responses to extractable soil P concentrations in sand greens. A 3‐yr field experiment was conducted on a sand‐based putting green to determine creeping bentgrass (Agrostis stolonifera L.) growth and quality responses to extractable soil P. Extractable soil P concentrations were obtained by using the modified‐Morgan, Mehlich‐1, and Bray‐1 extractants. Critical extractable P concentrations (above which there is a low probability of response to increasing soil P concentrations) for shoot counts, thatch thickness, relative clipping yields, quality ratings, P deficiency ratings, tissue P concentrations, and root weights were determined using Cate‐Nelson (CN) and quadratic response and plateau (QRP) models. Both models fit the data relatively well in most cases (R2 values from 0.12 to 0.89), and critical concentrations for the QRP models were always greater than the CN models. Critical extractable P concentrations were lowest for the modified‐Morgan extractant (1.4 to 12.0 mg kg−1) and greatest for the Mehlich‐1 extractant (14.1 to 63.6 mg kg−1). Application of estimated critical extractable P concentrations in this study could be used to substantiate observed responses or explain lack of responses in other previously reported creeping bentgrass P studies. We found better model fits with modified‐Morgan extractable P for bentgrass quality ratings, deficiency ratings, and tissue P concentrations than with P extracted by the Mehlich or Bray methods. This suggests that the modified‐Morgan extractant may have advantages over stronger‐acid extractants when used on sand‐based media. The results can be used to revise or update existing P fertilization recommendations for bentgrass grown on sand‐based media.
C‐Banding and Localization of 18S‐5.8S‐26S rDNA in Tall Oatgrass Species
Authors: Mitchell Crystal C. , Parkinson Susan E. , Baker Theron J. , Jellen Eric N.
Published: July 2014

The tall oatgrasses (Arrhenatherum spp., x = 7) are perennial diploid or autotetraploid forages of temperate grasslands. The most economically important species is common tall oatgrass, A. elatius (L.) P. Beauv. ex J. Presl & C. Presl. We were interested in cytogenetically characterizing this species due to its potential as a tertiary germplasm source for improving heat and cold tolerance in common oat (Avena sativa L.). We used C‐banding and fluorescence in situ hybridization with an 18S‐5.8S‐26S (45S) ribosomal DNA probe to examine the degree of chromosomal variation among tetraploids of the tall oatgrass genus. C‐banding karyotypes were analyzed for three geographically diverse accessions of A. elatius and one accession each of A. album (Vahl) Clayton, A. parlatorei (Woods) Potzt., and A. thorei Durieu [= A. longifolium (Thore) Dulac]. Tall oatgrass chromosomes were predominantly euchromatic and metacentric to submetacentric, with occasional subtelocentric chromosomes. The A. parlatorei karyotype was the most distinct of the six accessions, having a prominent telomeric C‐band. Arrhenatherum album, A. elatius, and A. thorei had a single nucleolus organizer region (NOR) locus as evidenced by the appearance of four in situ hybridization sites on somatic metaphase chromosome preparations using the wheat 45S ribosomal DNA (rDNA) clone pTa71.
Genetic Analysis and Random Amplified Polymorphic DNA Markers Associated with Cooking Time in Common Bean
Authors: Jacinto‐Hernandez Carmen , Azpiroz‐Rivero Susana , Acosta‐Gallegos Jorge A. , Hernandez‐Sanchez Humberto , Bernal‐Lugo Irma
Published: July 2014

Cooking time is an important trait in the breeding of common beans (Phaseolus vulgaris L.), especially in Mexico where 96% of beans consumed are prepared in the household. Because of the characteristics of the cooking time trait, a method of indirect selection would increase selection efficiency. The objective of this study was to identify random amplified polymorphic DNA (RAPD) markers associated with the trait and estimate genetic parameters of cooking time. For that purpose, 104 recombinant inbred lines (RILs), derived from contrasting cooking time bean cultivars were evaluated for three consecutive generations (F5 to F8). In each generation, cooking time was determined and plants in the F7 generation were genotyped. One marker was associated with cooking time. The polymorphic UNAM‐16 of 310 base pairs (bp) explained 23% of the variation in cooking time of the lines studied. Narrow sense heritability (h2) was estimated for cooking time, as was the number of genes involved in the trait. A high value of h2 (0.74) was estimated for cooking time. Also, it was estimated that two genes control the cooking time trait.
Molecular Mapping of Leaf Rust Resistance Gene Rph5 in Barley
Authors: Mammadov J. A. , Zwonitzer J. C. , Biyashev R. M. , Griffey C. A. , Jin Y. , Steffenson B. J. , Maroof M. A. Saghai
Published: July 2014

Leaf rust caused by Puccinia hordei G. Otth is an important disease of barley (Hordeum vulgare L.) in many regions of the world. Yield losses up to 32% have been reported in susceptible cultivars. The Rph5 gene confers resistance to the most prevalent races (8 and 30) of barley leaf rust in the USA. Therefore, the molecular mapping of Rph5 is of great interest. The objectives of this study were to map Rph5 and identify closely linked molecular markers. Genetic studies were performed by analysis of 93 and 91 F2 plants derived from the crosses ‘Bowman’ (rph5) × ‘Magnif 102’ (Rph5) and ‘Moore’ (rph5) × Virginia 92‐42‐46 (Rph5), respectively. Bulk segregant analysis (BSA) using amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP), and simple sequence repeat (SSR) markers was conducted. Linkage analysis positioned the Rph5 locus to the extreme telomeric region of the short arm of barley chromosome 3H at 0.2 centimorgans (cM) proximal to RFLP marker VT1 and 0.5 cM distal from RFLP marker C970 in the Bowman × Magnif 102 population. Map positions and the relative order of the markers were confirmed in the Moore × Virginia 92‐42‐46 population. RFLP analysis of the near isogenic line (NIL) Magnif 102/*8Bowman, the susceptible recurrent parent Bowman, and Rph5 donor Magnif 102, confirmed the close linkage of the markers VT1, BCD907, and CDO549 to Rph5. Results from this study will be useful for marker‐assisted selection and gene pyramiding in programs breeding for leaf rust resistance and provide the basis for physical mapping and further cloning activities.
Inheritance and Expression of Transgenes in Barley
Authors: Bregitzer Phil , Tonks Dennis
Published: July 2014

Empirical assessments of transgene inheritance and phenotypic expression will assist in the development of efficient breeding strategies for transgenic germplasm, and guide research into the improvement of transformation techniques. The inheritance of a barley yellow dwarf virus (BYDV) coat protein gene and bar, and the expression of bar as measured by resistance to glufosinate‐ammonium damage, was studied in the T1 and T3 generations of barley (Hordeum vulgare L.) populations derived from seven independent transformation events. Most populations deviated from Mendelian inheritance patterns, and several showed evidence of transgene silencing. To further study transgene behavior, several transgenic lines were crossed to a diverse set of nontransgenic cultivars and breeding lines to produce single cross‐ and backcross‐derived populations. In these populations, the inheritance of glufosinate‐ammonium resistance generally fit Mendelian expectations for single, dominant loci. Quantitative measurements of glufosinate‐ammonium resistance showed heritable variability for glufosinate‐ammonium resistance both among and within individual transformation events, but no variability could be attributed to the different genetic backgrounds of the nontransgenic parents. It is concluded that, although transgenic parents such as these can be used in a breeding program, transformation systems that result in greater stability of transgene behavior are desirable.
Illinois Bundleflower Genetic Diversity Determined by AFLP Analysis
Authors: DeHaan L. R. , Ehlke N. J. , Sheaffer C. C. , Muehlbauer G. J. , Wyse D. L.
Published: July 2014

Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMillan] is an herbaceous perennial legume native to North America. Useful as a N2–fixing plant in warm‐season grass pastures, Illinois bundleflower is also a promising perennial grain crop. Knowledge of the distribution of genetic variation in Illinois bundleflower would increase efficiency of germplasm preservation and expedite plant breeding progress. The objective of this experiment was to determine the distribution of genetic variation within and between Illinois bundleflower accessions by amplified fragment length polymorphism (AFLP) markers. Semi‐automated fluorescence‐based AFLP analysis was performed on three individuals from each of 50 accessions. We identified 222 markers, 159 of which were polymorphic. Within‐accession diversity was low (HS = 0.013) compared with total gene diversity (HT = 0.086). Analysis of molecular variance (AMOVA) showed that 83% of the molecular variance was explained by two major clusters, supporting a previous phenotypic study that suggested the existence of two distinct races of Illinois bundleflower. The less commonly occurring of the two races contained greater genetic diversity and originated from a localized region in the south central USA. The collection of more accessions from throughout the USA and focused on the Southeast would likely increase the genetic variation available to plant breeders.
Visualization of freezing progression in turfgrasses using infrared video thermography
Authors: Stier J. C. , Filiault D. L. , Wisniewski Michael , Palta J. P.
Published: July 2014

Freezing injury can be a significant problem in turfgrasses. Understanding how freezing develops and ramifies throughout the plant could assist in the development of improved management or screening processes for cultivar improvement. The development of freezing injury is not well understood due partly to lack of technology to view freezing origin and progression of whole plants in real time. Perennial ryegrass (Lolium perenne L.) and supina bluegrass (Poa supina Schrad.) plants were incubated in either cold‐acclimating or nonacclimating temperatures. Droplets containing ice‐nucleating bacteria (Pseudomonas syringae) were placed on turf leaves, crowns, and roots. Plants were then subjected to progressively decreasing freezing temperatures in a controlled environment. An infrared thermal imaging radiometer (camera) was used to view ice initiation and propagation in whole plants in real time. Freezing always originated in roots, spreading acropetally and basipetally throughout connecting root tissues until it contacted the crown. Freezing was slow in the crown, then occurred rapidly upwards into shoots, then leaves. The time (i.e., temperatures) required for freezing was similar between the two species of nonacclimated plants. In acclimated plants, supina bluegrass roots froze earlier than roots of perennial ryegrass, though freezing times were similar for crown and leaf tissues. Ice‐nucleating bacteria did not incite freezing of turf tissues. The project demonstrated the utility of infrared imaging for detecting freezing events in whole turfgrass plants. Results suggest that root tissue in the vicinity of the crown can be a source of ice which propagates into the crown and kills the plant.
Morphological plasticity of chickpea in a semiarid environment
Authors: Liu Pu‐hai , Gan Yantai , Warkentin Tom , McDonald Cal
Published: July 2014

Chickpea (Cicer arietinum L.) is being rapidly adapted to the semiarid northern Great Plains, but little is known about the morphological responses of this annual grain legume to the dry environment. This study, conducted in southwestern Saskatchewan, examined the morphological plasticity of three market classes of chickpea by growing the crop at four plant population densities. Chickpea grown at high (50 plants m−2) population density produced approximately half as many fertile pods per plant as those grown at low (20 plants m−2) density, but total number of pods per unit area increased with increasing plant population density. Large‐seeded kabuli chickpea produced fewer pods per unit area, or <60% of that produced by small‐seeded kabuli, and <50% of that by desi chickpea. Infertile pods accounted for 17 to 23% of the total pods for large‐seeded kabuli, compared with 9 to 12% for small‐seeded kabuli, and 6% for desi chickpea. The large‐seeded kabuli produced <87 seeds for every 100 pods produced, whereas desi and small‐seeded kabuli produced >110 seeds for every 100 pods. Consequently, the large‐seeded kabuli chickpea produced <90% of seed yield per unit area than small‐seeded kabuli and desi chickpea. As plant population increased from 20 to 50 plants m−2, the seed yield m−2 increased by 20% for desi and 27% for small‐seeded kabuli, but only 17% for the large‐seeded kabuli chickpea. In the semiarid northern Great Plains, seed yield potential of desi and small‐seeded kabuli chickpea can be increased by increasing plant population density, whereas the seed yield of large‐seeded kabuli can be improved by increasing percentage pod fertility.
Absence of Epistasis for Grain Yield in Elite Maize Hybrids
Authors: Hinze Lori L. , Lamkey Kendall R.
Published: July 2014

Certain maize (Zea mays L.) inbred lines are more successful than others in forming elite hybrids. This study was conducted to determine whether epistatic interactions play a significant role in hybrid performance. Statistical epistasis was measured with a modified generation means model using testcrosses. Six progeny generations (P1, P2, F1, F2, and a backcross from the F1 to each parent) were produced for all possible hybrids of a five‐parent diallel in both the Iowa Stiff Stalk Synthetic (BSSS) and non‐BSSS heterotic groups. Two testers were hybridized to each of the 10 possible hybrid progeny sets in both groups. Each testcross progeny set was evaluated in 10 environments. The nonepistatic model accounted for a large amount of the variation in generation means and fit the data well. Of the 40 maize testcross progeny sets studied, five resulted in a significant epistatic effect for grain yield. Four of the significant epistatic effects showed evidence of linkage, while one was due to unlinked epistatic effects. Our results suggest that parents in a hybrid cross need to be significantly different and testers need to bring out those differences to detect epistasis better by means of testcross generation means.
Molecular Marker Analysis of Seed Size in Soybean
Authors: Hoeck Joseph A. , Fehr Walter R. , Shoemaker Randy C. , Welke Grace A. , Johnson Susan L. , Cianzio Silvia R.
Published: July 2014

Seed size is an important attribute of soybean [Glycine max (L.) Merr.] for some food uses. The objectives of this study were to identify simple‐sequence‐repeat (SSR) markers associated with quantitative trait loci for seed size (SSQTL) and to compare the effectiveness of phenotypic selection and marker‐assisted selection for seed size among individual F2 plants. Three small‐seeded lines were crossed to parents with normal seed size to form three two‐parent populations. The parents of the populations were screened with 178 SSR markers to identify polymorphism. Population 1 (Pop 1) had 75 polymorphic SSR markers covering 1306 centimorgans (cM), Pop 2 had 70 covering 1143 cM, and Pop 3 had 82 covering 1237 cM. Seed size of each population was determined with 100 F2 plants grown at Isabela, Puerto Rico, and their F2–derived lines grown in two replications at three environments. Single‐factor analysis of variance and multiple regression were used to determine significant marker‐SSQTL associations. Population 1 had 12 markers that individually accounted for 8.1 to 14.9% of the variation for seed size combined across environments, Pop 2 had 16 markers that individually accounted for 7.8 to 36.5% of the variation, and Pop 3 had 22 markers that individually accounted for 8.6 to 28.8% of the variation. Three marker loci that had significant SSQTL associations in this study also were significant in previous research, and 13 markers had unique SSQTL associations. The relative effectiveness of phenotypic and marker‐assisted selection among F2 plants varied for the three populations. Averaged across the three populations, phenotypic selection for seed size was as effective and less expensive than marker‐assisted selection.
Reproductive and Molecular Evidence for Allogamy in Lotononis bainesii Baker
Authors: Real Daniel , Rizza Marco Dalla , Quesenberry Kenneth H. , Echenique María
Published: July 2014

Reproductive characteristics can influence seed production and the amount and distribution of genetic variation within populations. Lotononis bainesii Baker is a subtropical forage legume from southern Africa that earlier researchers reported as having a cleistogamous form of reproduction. More recent reports suggest that species in the genus Lotononis Section Listia reproduce chasmogamously. Research from this study suggests that this species needs pollinators to produce seed and that genotypes exist that are self‐incompatible. The use of sequence characterized amplified regions (SCAR) and cleaved amplified polymorphic sequence (CAPS) markers demonstrated that L. bainesii is highly allogamous.
Random Mating before Selfing in Maize BC1 Populations
Authors: Arbelbide Martin , Bernardo Rex
Published: July 2014

In maize (Zea mays L.) inbred development programs, F2 and BC1 populations between two inbreds are usually not random‐mated before selfing. Previous results suggest random mating is not useful in F2 populations. A one‐locus model, however, suggests random mating increases the genetic variance by 50% in a BC1 population without affecting the population means. The objective of this study was to determine the effect of random mating on the testcross means and variances of BC1 populations. Random‐mated and nonrandom‐mated backcross populations were developed for two genetic backgrounds, Iowa Stiff Stalk Synthetic (BSSS) and non‐BSSS. Testcrosses of these four populations were evaluated at five locations in Minnesota and Wisconsin in 2002. For grain yield, grain moisture, plant height, ear height, root lodging, and stalk lodging, the differences between testcross means of random‐mated and nonrandom‐mated populations were not significant (P = 0.05), as expected. Testcross variances tended to increase with random mating for most traits in the two genetic backgrounds, but none of these differences was significant. Testcross means of the best 10% families did not differ significantly between random‐mated and nonrandom‐mated populations. Overall, the results indicated that random mating before selfing in BC1 populations is not useful in applied breeding programs.
Changes in Genetic Variance during Advanced Cycle Breeding in Maize
Authors: Yu Jianming , Bernardo Rex
Published: July 2014

Advanced cycle breeding in crops aims to develop newer, improved versions of inbreds from crosses among current, elite inbreds. Although genetic gains in many crops have been achieved through advanced cycle breeding, this breeding process systematically leads to a narrow germplasm base. Our objectives were to estimate the loss, if any, in genetic variance during advanced cycle breeding in maize (Zea mays L.), and to compare these genetic variance estimates with those expected under a testcross additive model. We evaluated the Iowa Stiff Stalk Synthetic (BSSS), B73 × B37, and Lo904 × Lo916 populations, which have a common genetic background but have different levels of genetic variance expected from the testcross additive model; that is, 100% in BSSS, 82% in B73 × B37, and 45% in Lo904 × Lo916. Contrary to expectations, testcross additive variances (VTA) for grain yield did not significantly differ among the three populations. As expected, VTA for grain moisture, stalk lodging, plant height, and ear height were significantly lower in B73 × B37 than in BSSS. The decreases in VTA for these traits were not significant from B73 × B37 to Lo904 × Lo916. Fitting a testcross epistatic model did not result in positive estimates of both VTA and testcross additive‐by‐additive variance (VTAA) for any trait. In summary, genetic variance, except for grain yield, was lost during advanced cycle breeding and the amount of loss was greater than expected.
Quantitative Trait Loci for Soybean Seed Yield in Elite and Plant Introduction Germplasm
Authors: Smalley Matthew D. , Fehr Walter R. , Cianzio Silvia R. , Han Feng , Sebastian Scott A. , Streit Leon G.
Published: July 2014

Genetic improvement for yield in soybean [Glycine max (L.) Merr.] has been accomplished by breeding within a narrow elite gene pool. Plant introductions (PIs) may be useful for obtaining additional increases in yield if unique and desirable alleles at quantitative trait loci (QTL) can be identified. The objectives of the study were to identify QTL for yield in elite and PI germplasm and to determine if the PIs possessed favorable alleles for yield. Allele frequencies were measured with simple sequence repeat (SSR) markers in three populations, designated AP10, AP12, and AP14, that differed in their percentage of PI parentage. AP10 had 40 PI parents, AP12 had 40 PI and 40 elite parents, and AP14 had 40 elite parents. Four cycles of recurrent selection for yield had been conducted in the three populations. Allele frequencies of the highest‐yielding C4 lines in the three populations were compared with the parents used to form the populations of the initial cycles. Allele flow was simulated to account for genetic drift. Fifty‐four SSRs were associated with 43 yield QTL. Seven of the QTL had been identified in previous research. Sixteen favorable marker alleles were unique to the PI parents. The genes associated with the unique PI alleles merit further investigation for their potential to increase yield of soybean cultivars.
Legal Liability Issues in Agricultural Biotechnology
Authors: Kershen Drew L.
Published: July 2014

This article presents an overview of the legal liability issues in torts and patent law that arise from the use of transgenic crops produced by agricultural biotechnology. Torts—A tort is a civil legal action whereby the claimant alleges injury or wrong, arising independent of contract, to the person or property of the claimant. The article begins with legal liability claims for damage to property, damage to persons, and damage to economic interests (markets) that may arise with the use of transgenic crops. The tort theories discussed include the legal claims of trespass, strict liability, negligence, private nuisance, and public nuisance. With respect to each tort theory, the discussion points out unique legal issues that are likely to exist specifically because the litigation involves agricultural biotechnology. Patent Infringement—The article ends by focusing on four patent infringement cases that courts in Canada and the USA have decided regarding farmers who used patented seed from agricultural biotechnology without permission of the patent holder. As of May 2003, these are the only four patent infringement cases that have resulted in formal legal opinions by courts construing patent and antitrust laws in the context of farmers saving seeds protected by patents.
Pollination Timing Effects on Kernel Set and Silk Receptivity in Four Maize Hybrids
Authors: Anderson Steven R. , Lauer Michael J. , Schoper John B. , Shibles Richard M.
Published: July 2014

Silk receptivity and kernel set vary with time of pollination and environment. Our objectives were to evaluate differences in kernel set, silk elongation patterns, and duration of silk receptivity for four hybrids. These experiments used pollen‐saturating hand pollinations of four field‐grown maize (Zea mays L.) hybrids at varying days after first silk (DAFS) appearance in 1992, 1993, and 1994. Kernel set on primary ears was determined for B73 × MO17 (low silk turgor), WF9 × A632 (high silk turgor), Pioneer 3343, and Pioneer 3379 (Pioneer Hi‐Bred Int., Inc., Johnston, IA). WF9 × A632 had the fastest initial silk growth rate, resulting in earlier successful pollination of midbase floret positions. However, these floret positions declined in kernel set at later DAFS due to loss in silk receptivity and poor silk health. Thus, it had a lower final kernel number and a faster decline in kernel set when pollinated 10 DAFS in 1992 and 8 DAFS in 1993 and 1994. Hybrid WF9 × A632 had the lowest receptive trichome surface area, trichome density, and trichome number on its exposed silk surface 3 DAFS compared with the other three hybrids. Hybrid silk trichome length varied and was longer near the silk tip. Although silk elongation patterns were different, silk growth rates for all four hybrids gradually declined to near zero by 8 to 10 DAFS in 1992. We conclude that kernel set and yield stability are impacted by variation among hybrids for silk elongation and senescence.
Nitrate Uptake of Seedling and Mature Kentucky Bluegrass Plants
Authors: Jiang Zhongchun , Sullivan W. Michael
Published: July 2014

Understanding the relationship between seedling nitrate uptake rate (NUR) and mature plant NUR will benefit the selection of turfgrass cultivars for high NUR. Seedling NUR as affected by initial mowing is particularly important during turfgrass establishment. The primary objectives of this study were to determine NUR of individual Kentucky bluegrass (Poa pratensis L.) seedlings, to correlate seedling morphological characteristics with NUR, and to ascertain the relationship between seedling NUR and mature plant NUR. Thirty days after seeding, roots of seedlings were placed individually in a polystyrene cup filled with 2 mL of a nutrient solution containing 0.6 mM nitrate, which was replaced at 24‐h intervals for 20 d. After the total leaf and total root length and area were determined, each seedling was planted in silica sand and maintained as a miniature turf for five additional months before NUR was determined in a 130‐mL growth vessel. Seedling NUR was 10 to 60 nmol h−1 per seedling, decreased sharply to <10 nmol h−1 per seedling following the first clipping to remove 1/3 of the leaf blades by length. One week after the first clipping, NUR gradually increased to levels above 10 nmol h−1 per seedling. After seedlings were placed in deionized water for 24 h, NUR during the subsequent 24 h was stimulated, but the magnitude of stimulation differed among cultivars. We found significant among‐cultivar and within‐cultivar differences in seedling NUR, and significant and positive correlations between seedling NUR and seedling size. At the whole plant level, the correlation between seedling NUR and mature plant NUR was positive but generally not significant at P = 0.05.
Nitrogen Use in Tifway Bermudagrass, as Affected by Trinexapac‐Ethyl
Authors: Fagerness Matthew J. , Bowman Daniel C. , Yelverton Fred H. , Rufty Thomas W.
Published: July 2014

Nutrient movement from turfgrass systems into surface and ground water is a public concern. Data indicate that actively growing turf rapidly immobilizes applied N, thus restricting nutrient movement. It is possible, however, that growth suppression with plant growth regulators (PGRs) could reduce N demand and thus N uptake, resulting in greater leaching losses. An experiment was conducted with column lysimeters to investigate the effects of trinexapac‐ethyl (TE) on nitrate leaching and N‐use efficiency in Tifway bermudagrass (Cynodon dactylon × C. transvaalensis). The experiment was conducted in a growth chamber with day/night temperature set at 29/24°C and a 12‐h photoperiod. Trinexapac‐ethyl was applied twice at 4‐wk intervals at 0.11 kg a.i. ha−1 Ammonium nitrate (AN) was applied at 50 kg N ha−1 2 wk after each TE application, and again 6 wk after the second TE application. Separate sets of columns received 15N‐labeled AN for the first two applications. Irrigation was scheduled to provide a leaching fraction of ≈50%; leachate was collected after each irrigation and analyzed for nitrate and ammonium. Cumulative nitrate leaching was unaffected by TE after the first two N applications, but was reduced ≈60% by TE following the third N application. Trinexapac‐ethyl reduced 15N allocation to clippings by ≈25% and increased 15N allocation to roots and rhizomes; total recovery of applied 15N in tissues was ≈65%. Results demonstrate chemical growth suppression with TE does not reduce N uptake or increase nitrate leaching from bermudagrass.
Morphological Characteristics of Big Bluestem and Switchgrass Plants Divergently Selected for Seedling Tiller Number
Authors: Smart Alexander J. , Moser Lowell E. , Vogel Kenneth P.
Published: July 2014

Selection at the seedling stage in grass breeding would be useful if seedling traits were correlated to desired agronomic traits of mature plants. Objectives of this study were to determine if seedlings from big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) populations that differ genetically in seedling tiller number differ in mature plant (i) morphological characteristics, (ii) forage yield managed by a three‐cut harvest system or a single end‐of‐season harvest, and (iii) leaf elongation rate. Field experiments were conducted on a Kennebec silt loam soil (fine‐silty, mixed, superactive, mesic Cumulic Hapludolls). In addition, greenhouse studies were conducted in 1999 through 2001. Seedlings from big bluestem and switchgrass populations that differed for seedling tiller numbers were transplanted into spaced‐planted field nurseries and greenhouse pots for study. Leaf width, leaf length, plant height, number of tillers per plant, yield, and leaf elongation rate were measured. Mature plant morphological characteristics differed between multiple‐tiller and single‐tiller plant types for both big bluestem and switchgrass. There were no differences in forage yield for big bluestem plant types. Switchgrass single‐tiller plant types yielded 200 g plant−1 more than multiple‐tiller types when harvested only once. Leaf elongation rate was 22 and 28% greater for single‐tiller types vs. multiple‐tiller types for big bluestem and switchgrass, respectively. Selection at the seedling level for tiller number appears to be an effective method to develop genotypes differing in yield per tiller, which has been shown to affect herbage yield when grown in swards.
Forage Production of Sainfoin across an Irrigation Gradient
Authors: Peel Michael D. , Asay Kay H. , Johnson Douglas A. , Waldron Blair L.
Published: July 2014

Limited water and curtailed use of public lands for grazing has increased interest in intensively managed pastures in the western USA. Our objective was to evaluate forage production of sainfoin (Onobrychis viciifolia Scop.), a nonbloating legume, compared with alfalfa (Medicago sativa L.). Thirteen sainfoin cultivars and ‘Deseret’ alfalfa were evaluated at four water levels (WLs) and four harvests in 1998 and 1999 under a line‐source irrigation system. Water levels (WL1, WL2, WL3, and WL4) received an average of 78.3, 65.8, 34.9, and 8.3 cm of water, respectively. Significant effects were found for cultivar, cultivar × WL, harvest date, and cultivar × harvest date. Annual production of sainfoin at WL1, WL2, WL3, and WL4 was 11.6, 11.4, 9.6, and 8.9 Mg ha−1, respectively, whereas annual production of Deseret was 20.7, 18.5, 18.0, and 16.3 Mg ha−1, respectively. Overall yield trends across WLs were linear for sainfoin and Deseret and were parallel (P = 0.55) with slopes of b = 0.042 and b = 0.054, respectively. Yield of sainfoin at Harvest 1 through 4 was 5.5, 2.1, 1.5, and 1.3 Mg ha−1, respectively. Yield of Deseret from Harvest 1 through 4 was 5.9, 5.3, 4.7, and 2.4 Mg ha−1, respectively. Yields of the two species at Harvest 1 did not differ. The flat linear trend across WLs verifies that both crops are tolerant to dry conditions. With its highest production potential during early growth, sainfoin is best suited for situations where early growth of a nonbloating legume is desired, but will not compete with alfalfa in total seasonal production.
Using Environmental Covariates to Explain Genotype × Environment and QTL × Environment Interactions for Agronomic Traits on Chromosome 3A of Wheat
Authors: Campbell B. T. , Baenziger P. S. , Eskridge K. M. , Budak H. , Streck N. A. , Weiss A. , Gill K. S. , Erayman M.
Published: July 2014

Genotype × environment interactions (GEI) and quantitative trait loci × environment interactions (QEI) are known to influence the expression of agronomic performance traits in wheat. The aim of this study was to provide biological and environmental explanations for large GEI and QEI known to affect the expression of genes on chromosome 3A of wheat (Triticum aestivum L.). Agronomic performance and molecular marker data available for a population of chromosome 3A recombinant inbred chromosome lines (RICLs‐3A) in seven environments was used along with environmental covariate data to construct individual factorial regressions to explain GEI and QEI. Precipitation and temperature before anthesis had the greatest influence on agronomic performance traits for the RICLs‐3A, and explained a sizeable portion of the total GEI for those traits. Individual molecular marker × environmental covariate interactions explained a large portion of the total marker × environment interactions for several agronomic traits. Seventy‐six percent of the QEI for a major grain yield quantitative trait locus (QTL) was explained by the effect of temperature during preanthesis growth on dissimilar QTL genotype differentials across testing environments. Environmental covariates provided a strong basis for explaining QEI using marker × environmental covariate interactions.
Linkage of Molecular Markers to Cercospora zeae‐maydis Resistance in Maize
Authors: Gordon Stuart G. , Bartsch Michael , Matthies Inge , Gevers Hans O. , Lipps Patrick E. , Pratt Richard C.
Published: July 2014

Gray leaf spot (GLS) of maize (Zea mays L.) caused by Cercospora zeae‐maydis Tehon & E.Y. Daniels, can greatly reduce grain yield in conducive environments worldwide. This study was undertaken to evaluate a novel source of resistance to C. zeae‐maydis across macroenvironments and link molecular markers to resistance loci by selective genotyping. A population of 144 F2:3 progeny lines derived from a cross between resistant maize inbred VO613Y and susceptible inbred Pa405 were evaluated at Wooster, OH, USA, and Cedara Agricultural Research Institute, Department of Agriculture, KZN, Republic of South Africa (RSA), for resistance to C. zeae‐maydis The lines were assigned to phenotypic classes (resistant, intermediate, and susceptible) on the basis of percent leaf area affected (PLAA) values across environments. F2:4 progeny lines were produced by controlled self‐pollination of an individual plant within each F2:3 line. F2:4 lines derived from resistant and susceptible classes were evaluated at two Ohio locations. The same lines, plus a random sample of 54 F2:4 lines representing the intermediate class, were evaluated at Cedara. Molecular marker data were analyzed on the basis of PLAA means of F2:4 progenies by Kruskal–Wallis analysis and several markers on chromosomes 2 and 4 were deemed to be significantly associated with resistance. Additional molecular markers were added and composite interval mapping was conducted on genetic maps of those chromosomes. Quantitative trait loci (QTL) located on chromosome arms 2L and 4L together explained 40 to 47% of the phenotypic variation. A resistance gene analog probe flanked the significant interval on chromosome 4L. These intervals on chromosomes 2L and 4L were detected in all tests and we consider them to be suitable candidate QTL for marker‐assisted selection (MAS). These results indicate that VO613Y is a source of resistance with potential to be deployed effectively in both southern Africa and the U.S. Corn Belt.
Analysis of Genetic Diversity in Cultivated Jute Determined by Means of SSR Markers and AFLP Profiling
Authors: Basu A. , Ghosh M. , Meyer R. , Powell W. , Basak S. L. , Sen S. K.
Published: July 2014

Genetic improvement of the cultivars of jute (Corchorus olitorius L. and Corchorus capsularis L.) is needed to broaden the genetic base of new cultivars. All the cultivars in use have been evolved through pure line selection from a few common accessions. The objective of this study was to evaluate the genetic diversity available in the cultivated species of jute. Genetic diversity was evaluated by simple sequence repeat (SSR) marker loci and an AFLP assay. A total of 305 polymorphic products were detected by AFLP analysis using 10 pairs of primers (EcoRI and MseI) to amplify template DNA from 49 genotypes of the two jute species. Additionally, polymorphism with two to four allelic lengths was detected with each pair of chloroplast microsatellite primers developed from Nicotiana tabacum L. Results from both evaluations showed that the level of variation between species is high. The two species indeed are distantly related and their maternal origins may be different. On the contrary, genetic variability present at the intraspecific level is low. The resulting dendrogram showed common ancestral origin for many accessions. A few major Indian cultivars of both the species, used as an internal check, were closely related to the wild accessions. Nevertheless, RG, an Indian accession and two Kenyan accessions, KEN/BL/17 and KEN/DS/35C, among the C. olitorius genotypes and CHN/FJ/69 of C. capsularis revealed phenetic distinctiveness from the rest of the genotypes studied. The results indicate that enough diversity exists to broaden the genetic base of new jute cultivars.
An Improved Method for Accurate Phenotyping of Corn Stalk Strength
Authors: Robertson Daniel , Smith Simeon , Gardunia Brian , Cook Douglas
Published: July 2014

Weak stems or stalks in grass crop species increase the likelihood of stalk failure, thereby reducing yield. Three‐point bending tests are often employed in selective breeding studies to characterize stalk strength. However, it is hypothesized that the loading setup used during three‐point bending experiments may significantly alter test results. To investigate this hypothesis, two different loading configurations were employed in conducting three‐point bending experiments of corn (Zea mays L.) stalks. In the first configuration, stalks were loaded and supported at nodes. In the second configuration, stalks were loaded and supported at internodal segments. Significantly higher bending moments were experienced at internodal segments during the node‐loaded configuration than was required to fail the same segment during internode‐loaded tests. This is because the loading anvil significantly deforms the stalk's cross section when it is placed on an internodal segment, thereby inducing premature failure. In addition, internode‐loaded tests were observed to produce unnatural failure patterns, while node‐loaded tests demonstrated natural variability in failure location. While transverse deformation of the stalk cross section cannot be eliminated in three‐point bending tests, its effects can be mitigated by placing the loading anvil at nodal locations, which are much stiffer than internode regions. Maximizing the span length of bending tests likewise reduces transverse deformation of stalk cross sections. These results are relevant to selective breeding studies designed to produce lodging resistant crop hybrids.
Evaluation of the OhmMapper Instrument for Soil Moisture Measurement
Authors: Walker Jeffrey P. , Houser Paul R.
Published: July 2014

An instrument for making rapid measurements of the soil moisture content in the root zone is an essential tool for many applications, including understanding of soil water dynamics, evaluation of agriculture water stress, and validation of soil moisture modeling. Studies have shown that electrical resistance measurements may be used to infer soil moisture content under special circumstances. In this paper, electrical resistivity (resistance multiplied by a geometric factor) measurements of the soil by the Geometrics Inc. OhmMapper instrument are compared with point measurements of soil moisture to a depth of 70 cm. It was found that the OhmMapper resistivity measurements could be used to infer soil moisture content with a coefficient of determination as high as 0.34 when a simple power law relationship was used. A more sophisticated analysis of the resistivity measurements could potentially lead to a greater coefficient of determination.