bluuebunny/crossref_metadata_2025 huggingface dataset:
Pollinator Effects on Genotypically Distinct Soybean Cytoplasmic Male Sterile Lines
Authors: Zhao Limei , Sun Huan , Peng Bao , Li Jianping , Wang Shuming , Li Maohai , Zhang Weilong , Zhang Jingyong , Wang Yueqiang
Published: October 2009

Poor seed‐set limits potential for soybean hybrid seed production. The objective of this study was to evaluate effects of different pollinators on the rate of seed set in three soybean cytoplasmic male sterile (CMS) lines, JLCMS9A, JLCMS82A, and JLCMS89A. The following five treatments were applied under net room isolation‐conditions: (i) insecticide application and release of alfalfa leafcutter bees (Megachile rotundata) during flowering; (ii) insecticide application in the absence of leafcutter bees; (iii) release of alfalfa leafcutter bees during flowering without insecticide application; (iv) the absence of insecticide or alfalfa leafcutter bees during flowering; (v) plants without a net cover and pesticide application. Results indicated that the rate of pod production and seed set differ significantly between CMS lines and between treatments. Alfalfa leafcutter bees were an effective pollinator as evidenced by increases in pod‐bearing rate and seed‐set rate respectively from 21.35 to 53.22% and from 19.91 to 58.77% in the three CMS lines. The three CMS lines also showed significant differences in seed set, with JLCMS82A exhibiting the highest rate in all five treatments, followed by JLCMS9A and then JLCMS89A. These results suggested that thrips (Sericothrips variabilis) might have some effect on soybean pollination, but did not elicit a major influence based on the low increases in seed production. The natural insect population served an important role in outcrossing and seed set in soybean.
Consequences of ex situ Conservation on the Genetic Integrity of Germplasm Held at Different Gene Banks: A Case Study of Bread Wheat Collected in Pakistan
Authors: Hirano Ryoko , Jatoi Shakeel Ahmad , Kawase Makoto , Kikuchi Akira , Watanabe Kazuo N.
Published: October 2009

Genetic diversity and genetic integrity were tested for wheat (Triticum aestivum L.) landraces conserved in two gene banks with considerably different germplasm management systems. We identified two sets of 17 wheat accessions derived from identical sources collected in Pakistan, which were later deposited at the National Institute of Agrobiological Sciences, Japan (NIAS) and the Plant Genetic Resources Program, Pakistan (PGRP). Regeneration of the conserved germplasm was infrequent at both gene banks. Amplified fragment length polymorphism (AFLP) profiles did not indicate prominent changes in the banding patterns of the wheat landraces conserved at the two gene banks. No significant differences were observed in allele frequency of the detected loci in comparison to the original collections (materials preserved without regeneration and multiplication), except in one accession at NIAS. We conclude that genetic diversity was conserved at these two gene banks with different management systems. However, among the 161 scored loci, 26 AFLP bands disappeared at the same loci in NIAS and PGRP accessions, four disappeared only in NIAS accessions, and 28 only in PGRP accessions. At one particular locus, the band disappeared in 12 PGRP accessions but not in NIAS accessions. The results indicate that unique selection might occur at PGRP and that regeneration strategies to reduce it will be needed in the future.
Impact of Genetic Divergence on the Ratio of Variance Due to Specific vs. General Combining Ability in Winter Triticale
Authors: Fischer S. , Möhring J. , Maurer H.P. , Piepho H.‐P. , Thiemt E.‐M. , Schön C.C. , Melchinger A.E. , Reif J.C.
Published: October 2009

The objective of our study was to examine the influence of genetic divergence on the ratio of the components of variance for specific (σ2SCA) and general (σ2GCA) combining ability using experimental data in triticale (×Triticosecale Wittm.). In total, 21 lines and their 210 crosses were evaluated for grain yield in field trials. Published molecular data were reanalyzed, indicating an optimum of two subgroups. The estimates of σ2SCA and σ2GCA were determined for the total diallel and between the two subgroups. The ratio of σ2SCA vs. σ2GCA tended to be lower for crosses between than within genetically distinct groups. Our experimental findings can be interpreted as an indicator of a more favorable ratio of σ2SCA vs. σ2GCA in situations with two genetically distinct populations than in situations with populations that are not genetically distinct.
Selection for Drought Tolerance in Dry Bean Derived from the Mesoamerican Gene Pool in Western Nebraska
Authors: Urrea Carlos A. , Yonts C. Dean , Lyon Drew J. , Koehler Ann E.
Published: October 2009

Dry bean (Phaseolus vulgaris L.) is highly susceptible to drought stress, and drought affects 60% of global bean production. We evaluated elite exotic dry bean germplasm derived from the Mesoamerican gene pool for drought tolerance, yield, and adaptation to western Nebraska during 2006 and 2007 at three research sites. Seven tropical lines were evaluated with two great northern cultivars (Matterhorn and Beryl‐R) and one pinto cultivar (Bill‐Z) serving as checks. Adjacent nonstressed (NS) and drought‐stressed (DS) blocks were evaluated. Within each block, the selected lines were assigned to experimental units using a randomized complete block design with four replications at each location. On average, yield was 60% less, 100‐seed weight was 19.2% lower, and maturity occurred 4 d earlier under DS than under NS conditions. Beryl‐R, SER 22, and Matterhorn had the greatest average yield under both NS (3564, 3347, and 3440 kg ha−1, respectively) and DS (1701, 1773, and 1584 kg ha−1, respectively). These genotypes were also the most drought tolerant based on the drought susceptibility index (0.9, 0.8, and 0.9, respectively) and geometric mean (2462, 2436, and 2335, respectively). Based on these results, Matterhorn, Beryl‐R, and SER 22 show the most promise for use in breeding for drought tolerance.
Genetic Variation for Resistance to Ear Rots and Mycotoxins Contamination in Early European Maize Inbred Lines
Authors: Bolduan C. , Miedaner T. , Schipprack W. , Dhillon B. S. , Melchinger A. E.
Published: October 2009

Ear rots caused by Fusarium spp. are a major concern in many maize (Zea mays L.)–growing regions of the world. Our objectives were (i) to evaluate a set of European maize inbreds for resistance to ear rots and mycotoxin concentrations, (ii) to estimate variance components and heritabilities, and (iii) to compute correlations among resistance traits. Forty‐two inbreds were evaluated for resistance to F. graminearum in four environments, and 21 inbreds were evaluated for resistance to F. verticillioides in three environments, under artificial inoculation. Data were recorded on severity of Gibberella (AGER) and Fusarium ear rots and accumulation of deoxynivalenol (DON), zearalenone, and fumonisins. Artificial inoculation was effective particularly for Gibberella ear rot. Genotypic and genotype × environment interaction variances were generally significant. Heritability estimates were moderate to high. Disease severity had strong correlations with respective mycotoxin concentrations. Selection for resistance is expected to have favorable correlated response for mycotoxins particularly with respect to AGER and DON (r p = 0.94). We recommend conducting initial selection on the basis of visual ratings and evaluate the selected elite material for mycotoxin concentrations.
Generalizing the Sites Regression Model to Three‐Way Interaction Including Multi‐Attributes
Authors: Varela Mario , Crossa Jose , Joshi Arun Kumar , Cornelius Paul L. , Manes Yann
Published: October 2009

When a multienvironment trial (MET) is established across several locations and years, the interaction is referred to as athree‐way arrayThree‐way interaction can be studied by means of three‐way principal components analysis. In this study, the three‐way principal components analysis is adapted to the sites regression model (three‐way SREG). The three‐way SREG with location and year combines the effects of genotype, genotype × location, genotype × year, and genotype × location × year. The objective of this study is to show how the three‐way SREG can be put to practical use in agriculture and breeding. We utilized two wheat (Triticum aestivumL) data sets that have already been used for fitting a three‐way additive main effects and multiplicative interaction model. One data set had genotype (25) × location (4) × sowing times (4) and eight attributes, and the other data set included genotype (20) × irrigation level × year on grain yield. The three‐way SREG applied simultaneously to eight attributes facilitates the interpretation of genotypic performance for all traits in specific locations and across locations for a selected sowing time. Results of the three‐way SREG for both data sets show the different response patterns of genotypes for locations and sowing dates (Data Set 1), as well as genotypic responses across irrigation levels in different years (Data Set 2). Using Data Set 1, we show that fitting a three‐way data structure to a three‐way SREG model is more effective for detecting important interaction patterns than using the two‐way SREG.
Heritability Estimates for Turfgrass Performance and Stress Response in Zoysia spp.
Authors: Schwartz Brian M. , Kenworthy Kevin E. , Engelke M. C. , Genovesi A. Dennis , Quesenberry Kenneth H.
Published: October 2009

Zoysiagrasses (Zoysia spp.) are widely adapted and highly variable; however, information is lacking regarding the heritability and potential for improvement of numerous performance characteristics. Three individual replicated field studies, which included 90 very fine, 108 fine, and 126 coarse‐textured zoysiagrass genotypes, respectively, were conducted near Gainesville, FL, to determine the response and broad‐sense heritabilities of 10 turfgrass performance and stress‐related characteristics. Genotypic variance largely contributed to the wide range in expressed phenotypic response for plot coverage, turf density, turf quality, genetic color, and seedhead density, which resulted in higher broad‐sense heritability estimates (0.62 ≤ H 2 ≤ 0.94). Fall dormancy and spring greenup were influenced more by the environment and had lower heritabilities (0.32 ≤ H 2 ≤ 0.58). Turf quality was also rated considering the effects of glufosinate [2‐amino‐4‐(hydroxymethylphosphinyl)butanoic acid] herbicide application, Bipolaris incidence, and mole cricket (Scapteriscus spp.) damage. Large error variances and low broad‐sense heritablities were typical for these stress‐related traits. Potential exists for improvement of characteristics that exhibited large amounts of genetic variation and were less influenced by the environment. Broad‐sense heritability estimates indicate the possibility of combining desirable traits in superior clonally propagated F1 hybrids.
Growth Analysis of Biomass Production in Sole‐Crop and Double‐Crop Corn Systems
Authors: Heggenstaller Andrew H. , Liebman Matt , Anex Robert P.
Published: October 2009

Increased biomass productivity could be achieved through double‐cropping if extended growth duration could be realized with minimal reductions in growth efficiency relative to sole‐cropping. To test this hypothesis, functional growth analysis was used to assess the relative importance of photosynthetic duration and efficiency in determining biomass production by sole‐crop corn (Zea mays L.; SC) and double‐crop triticale (×Triticosecale Wittmack)–double‐crop corn (DT–DC). Aboveground dry matter and leaf area were measured weekly, and net dry matter production was assessed for each crop at harvest. Over 2 yr, average harvested dry matter was 25% greater for DT–DC (22.7 Mg ha−1) than for SC (18.2 Mg ha−1), despite greater maximum leaf area index and greater maximum crop growth rate for SC relative to DT–DC. Leaf area duration was increased by 23% for DT–DC compared with SC, while maximum net assimilation rate and seasonal net assimilation rate did not differ between cropping systems. Across systems, variation in yield was positively related to maximum crop growth rate, maximum leaf area index, and leaf area duration but was not associated with maximum or seasonal net‐assimilation rate. Therefore, leaf duration was more important than leaf efficiency in determining productivity in both cropping systems, and greater biomass yield for DT–DC was the outcome of photosynthesis occurring over an extended duration. These results suggest that potential exists to increase biomass productivity by expanding the seasonal interval of photosynthesis, and that in the case of double‐cropping, expansion of leaf duration is not necessarily associated with reductions in leaf efficiency.
Japanese Sake‐Brewing Rice Cultivars Show High Levels of Globulin‐like Protein and a Chloroplast Stromal HSP70
Authors: Kamara Joseph S. , Hoshino Miki , Satoh Yuki , Nayar Nasrin , Takaoka Motoko , Sasanuma Tsuneo , Abe Toshinori
Published: October 2009

White‐core is an important trait in the selection of rice (Oryza sativa L. ssp. japonica) for sake (Japanese rice wine) production. The present study was conducted to find differences between the endosperm protein pattern of white‐core–bearing sake‐brewing cultivars and those of normal rice grains. Protein patterns of white‐core sake‐brewing grains were compared with those of normal cultivars by two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE). Several proteins showing different amounts were detected. These were identified by microsequencing and found to be known carbohydrate‐metabolizing enzymes as well as proteins with no known involvement in carbohydrate metabolism. Two units of globulin‐like protein (GLP) and a chloroplast stromal heat shock protein 70 (ctHSP70) showed the greatest difference in the white‐core group. Analysis of amyloplast proteins showed slightly higher amounts of GLP and ctHSP70 in the amyloplast than in the cytosol. Also, time‐course analysis of developing rice grains indicated that both proteins were elevated during the later stages of grain development. From this we conclude that GLP and ctHSP70‐II are associated with white‐core appearance and thus behave as biochemical markers for this character in sake‐brewing rice cultivars.
Cost Efficiency of Cryopreservation as a Long‐Term Conservation Method for Coffee Genetic Resources
Authors: Dulloo M. E. , Ebert A. W. , Dussert S. , Gotor E. , Astorga C. , Vasquez N. , Rakotomalala J. J. , Rabemiafara A. , Eira M. , Bellachew B. , Omondi C. , Engelmann F. , Anthony F. , Watts J. , Qamar Z. , Snook L.
Published: October 2009

Coffee (Coffea spp.) is one of the world's most valuable agricultural export commodities produced by small‐scale farmers. Its germplasm, which holds useful traits for crop improvement, has traditionally been conserved in field genebanks, which presents many challenges for conservation. New techniques of in vitro and cryopreservation have been developed to improve the long‐term conservation of coffee. But a question remains as to whether these new techniques are more cost effective than field collections and more efficient at reducing genetic erosion. This study compared the costs of maintaining one of the world's largest coffee field collections with those of establishing a coffee cryo‐collection at the Centro Agronómico Tropical de Investigación y Enseñanza (CATIE) in Costa Rica. The results indicate that cryopreservation costs less (in perpetuity per accession) than conservation in field genebanks. A comparative analysis of the costs of both methods showed that the more accessions there are in cryopreservation storage, the lower the per‐accession cost. In addition to cost, the study examined the advantages of cryopreservation over field collection and showed that for species that are difficult to conserve using seeds, and that can only be conserved as live plants, cryopreservation may be the method of choice for long‐term conservation of genetic diversity.
Bumble Bee Pollinators in Red Clover Seed Production
Authors: Rao Sujaya , Stephen William P.
Published: October 2009

Bumble bees pollinate red clover (Trifolium pratense L.) but impact on seed production depends on the species, abundance, and synchrony with bloom. The objectives of the current study were to examine pollination by a native bumble bee, Bombus vosnesenskii (Radoszkowski), determine the bumble bee fauna associated with red clover in Oregon, and assess if seed set is limiting. In a cage study, yields with B. vosnesenskii (average = 661 kg ha−1) and honey bees (Apis mellifera L.) (average = 640 kgha−1) were comparable. Yields were lower compared with open pollinated plots (average = 1127 kg ha−1), which was likely due to cage effect, as seed set (# seeds/# florets per seed head) was similar in all three treatments (excluding control). Examination of the diversity of endemic bumble bees through field counts and trapping in red clover fields indicated the presence of six species. Over 92% of these were B. vosnesenskii indicating that it is the key pollinator in Oregon. Seed set across four commercial fields was high (0.84–0.88) documenting that existing pollinators, including rented honey bees, and indigenous bumble bees and solitary bees, provide close to maximum pollination of red clover in Oregon. Higher yields will require improved production practices and new cultivars with more heads per plant. Sustainability of high yields in Oregon will depend on protection of indigenous bee pollinators through conservation of habitats that provide nesting sites, judicious pesticide use, and provision of floral resources before red clover bloom.
A Conceptual Model for Describing Processes of Crop Improvement in Database Structures
Authors: DeLacy Ian H. , Fox P. N. , McLaren Graham , Trethowan Richard , White Jeffrey W.
Published: October 2009

Rising research costs, broadening goals, intellectual property rights, and other concerns increase the need for robust management of crop improvement data. The data model of the International Crop Information System (ICIS) allows breeding processes to be recorded unambiguously in a relational database. This paper describes this model, which underlies the Genealogical Management System (GMS) of ICIS. The model recognizes three classes of methods by which genetic material is advanced. Generative methods such as crossing or mutagenesis increase variation. Derivative methods usually involve selection, and maintenance methods conserve the genetic makeup of germplasm, such as in seed multiplications. Unlike systems that only track pedigrees, the model describes steps of selection. Applications are illustrated for self‐pollinating, outcrossing, and clonally propagated crops. The ICIS GMS is in use for species including rice (Oryza sativa L.), wheat (Triticum aestivum L.), maize (Zea mays L.), potato (Solanum tuberosum L.), common bean (Phaseolus vulgaris L.), lesquerella [Lesquerella fendleri (Gray) S. Wats.], and witloof chicory (Cichorium intybus L.). The International Rice Information System, based on ICIS, holds more than 2.6 million unique identifiers for germplasm accessions, crosses, populations, and lines, requiring about 900 megabytes of storage space, which can easily be managed on a personal computer. The GMS model appears suited for widespread use in managing data on crop improvement.
Two Alleles of ahFAD2B Control the High Oleic Acid Trait in Cultivated Peanut
Authors: Chu Ye , Holbrook C. Corley , Ozias‐Akins Peggy
Published: October 2009

A high oleic:linoleic acid ratio (O/L) in peanut (Arachis hypogaea L.) seeds is controlled primarily by two recessive genes, ahFAD2A and ahFAD2B (ol1 and ol2). Marker‐assisted breeding for high O/L could become routine provided that user‐friendly and economical markers could be developed that would target mutant alleles underlying the trait. Previously, a mutant allele of ahFAD2A was characterized as having a 448G>A transition, and two ahFAD2B alleles were found with either a nonsense mutation caused by a single nucleotide insertion (441_442insA) (high O/L line F435) or a transposable element insertion (Flavorunner 458). A cleaved amplified polymorphic sequence (CAPS) marker targeting the 441_442insA site in ahFAD2B was designed. ‘Georgia‐02C’ and ‘Georgia Hi‐O/L’, derivatives of irradiation‐induced high O/L mutants, showed CAPS marker and sequence data diagnostic for the genetic mutations in ahFAD2 found in the spontaneous mutant line F435. In addition, conflicting reports regarding the organization of ahFAD2 genes and ahFAD2B mutations were reexamined. Our data clearly show that molecular markers can be used to screen for known ahFAD2 mutations and that only two mutant ahFAD2B alleles are present in the U.S. high O/L cultivars. Genetic markers based on these mutations have utility for detecting seed mixtures and heterozygotes, and can accelerate introduction of the high O/L trait into peanut breeding lines.
Microsatellite‐based Analysis of Tobacco (Nicotiana tabacum L.) Genetic Resources
Authors: Moon H. S. , Nifong J. M. , Nicholson J. S. , Heineman A. , Lion K. , van der Hoeven R. , Hayes A. J. , Lewis R. S.
Published: October 2009

Little is currently known about the genetic variation within diverse gene pools of cultivated tobacco (Nicotiana tabacum L.). Knowledge in this area could aid in future germplasm maintenance activities, provide additional information in the area of N. tabacum population genetics, and assist in selection of materials for breeding or genetic investigations. To this end, 702 N. tabacum accessions from the U.S. Nicotiana Germplasm Collection were genotyped with 70 microsatellite markers. A total of 1031 alleles were detected, with an average of 14.7 alleles per marker. Average gene diversity was quite large (0.7362) and was three times the value for a diverse population of U.S. flue‐cured tobacco. Cluster analysis using various distance coefficients generated seven consistent groups. Patterns of geographic‐specific clustering were frequent but not universal. An analysis of molecular variance for tobacco collected from Central and South America revealed that 92% of the total genetic variation among samples could be attributed to country‐specific subpopulations. There was also a significant level of population subdivision between country‐specific subpopulations, however. Tobacco samples collected from Peru had both the largest average gene diversity and the largest mean genetic distance, although N. tabacum collected from Mexico had the greatest allelic richness. Tobacco samples collected from Argentina were the most divergent subpopulation.
When Is Early Generation Selection Effective in Self‐Pollinated Crops?
Authors: Yang Rong‐Cai
Published: October 2009

Despite widespread use of early generation testing and selection (EGT) in breeding for self‐pollinated crops, its effectiveness remains largely an unresolved issue. This issue is tackled here using elaborated genetic models that enable genetic and nongenetic effects to be assessed for the effectiveness of EGT in terms of (i) the selection response at one or more early generations relative to the response to direct selection at homozygosity and (ii) the probability of retaining superior lines selected during EGT. The selection response to EGT is analyzed for a model with quadratic genetic components due to additive, dominance, additive × additive, and linkage effects in selfed populations derived from a cross between two inbreds. The response to one cycle of EGT is less than the response to direct selection and decreases with nonadditive effects, repulsion linkage and reduced heritabilities. The cumulative response to two or more cycles of EGT is greater than the response to direct selection unless there are strong nonadditive effects, strong repulsion linkage, and low heritabilities. The probability of retaining a superior line at EGT decreases with increased nonadditive effects and low heritabilities. The proportion of lines needed to minimize the risk of erroneously culling superior lines increases with increased nonadditive effects and low heritabilities. Thus, EGT should be used for populations or traits with little nonadditive effect, coupling linkage and high heritability.
Dynamics of the Evolution of the Genus of Agrostis Revealed by GISH/FISH
Authors: He Shibin , Huang Min , Huang Jing , Li Jun , Hu Yong , Zhang Lu , Zhang Chunzhen , Fei Shui‐zhang , Li Lijia
Published: October 2009

Genomic changes in related species undergoing human‐driven and natural selection are important and biologically interesting. The genus Agrostis is an ideal model for studying the evolution of plants since it has not undergone artificial selection for the past thousands of years. Fluorescence in situ hybridization (FISH) or genomic in situ hybridization (GISH) technology is an effective method for analyzing genome homology and organization, detecting genomic rearrangements, and karyotyping based on visual features. In this study, GISH was performed on two tetraploid species, A. capillaris (2n = 4x = 28, A1A1 A2A2) and A. stolonifera (2n = 4x = 28, A2A2 A3A3), using genomic DNA from a putative ancestral diploid species A. canina (2n = 2x = 14, A1A1) as a probe. Genomic in situ hybridization results revealed that the two tetraploid species underwent intergenomic translocations and genomic rearrangements and demonstrated that the A1 genome is highly homologous to the A2 genome. We discovered the phenomenon of concentric parental genome separation in the nucleus of A. stolonifera in which the two parental genomes (A2 and A3) were spatially separated with limited intermixing and were of concentric arrangements. The FISH results showed that the distribution of 45S rDNA loci varied among the three species. The results of our study suggest that substantial genomic alterations occurred during the evolution of the genus of Agrostis
DNA Polymorphisms Reveal Geographic Races of Reed Canarygrass
Authors: Casler M. D. , Phillips M. M. , Krohn A. L.
Published: October 2009

Reed canarygrass (Phalaris arundinacea L.) is a cool‐season perennial with a circumglobal distribution in the northern hemisphere, native to Europe, Asia, and North America. Repeated introductions of European germplasm into North America have created confusion over the origins of reed canarygrass germplasm found in wetlands, pastures, and breeding programs. The objectives of this study were to identify sources of DNA marker variation among reed canarygrass cultivars from Europe and North America and between landraces and improved cultivars from North America. Analysis of 205 reed canarygrass plants from 15 cultivars based on 102 amplified fragment length polymorphic (AFLP) DNA markers revealed two groups of cultivars. One group consisted of three closely related but geographically diverse North American landraces that were completely separated from all other plants in only two dimensions of the AFLP incidence matrix. The complete discrimination of these plants from all European plants suggests their possible origin from native North American germplasm. These results were supported by chloroplast DNA sequence analysis, which additionally revealed separation of a potential Scandinavian cytoplasmic race from the continental European cytoplasmic race. This is the strongest evidence to date suggesting that native North American reed canarygrass germplasm has been preserved within cultivars of this species.
New and Old Soybean Cultivar Responses to Plant Density and Intercepted Light
Authors: De Bruin Jason L. , Pedersen Palle
Published: October 2009

Genetic gain for new soybean [Glycine max (L.) Merr.] cultivars is substantial, and research suggests this is partially explained by greater tolerance to increased plant densities. We conducted an experiment to determine if greater tolerance to increased plant density and more efficient use of cumulative intercepted photosynthetically active radiation (CIPAR) partially explained the yield difference of two old soybean cultivars and two new cultivars. Soybean cultivars were grown in 38‐cm spaced rows at final plant densities of 4.9, 14.8, 24.7, 34.6, and 44.5 plants m−2 for 2 yr in Ames, IA. New cultivars averaged 914 kg ha−1 and 4.9 g plant−1 greater yield compared with old cultivars averaged across years and plant densities. Yield plateaus occurred at plant densities of 23.0 plants m−2 for new cultivars and 19.9 plants m−2 for old cultivars. Each cultivar group showed a similar yield decline per plant to increased plant density. New and old cultivars showed a similar response to increasing values of CIPAR, attaining a 95% relative yield plateau at 466 MJ m−2 Soybean yield response to increased plant density and CIPAR has not changed over time, and genetic gain from new cultivars is associated with more efficient use of light.
Inheritance Characteristics of Brown Patch Resistance in Tall Fescue
Authors: Bokmeyer Jonathan M. , Bonos Stacy A. , Meyer William A.
Published: October 2009

Brown patch disease, caused by Rhizoctonia solani Kühn, is one of the most devastating fungal pathogens that occur on tall fescue [Lolium arundinaceum (Schreb.) Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort]. The development of genetic resistance to brown patch would provide the most effective long term control to this disease; however, the genetic mechanism of brown patch resistance in tall fescue is not known. For this study, a diallel cross involving six parents was conducted to investigate the genetic inheritance characteristics of brown patch resistance in tall fescue. Parents and their progeny were evaluated for brown patch resistance in a field experiment conducted over two years in which the field experiment was inoculated with a single isolate of R. solani Both general combining ability (GCA) and specific combining ability (SCA) effects were significant; however, the GCA accounted for a greater proportion of the sum of squares. Moderate narrow‐sense heritability estimates [0.62 (2007) and 0.57 (2008)] were calculated from mid‐parent‐progeny regression analysis. Estimates of the minimum number of effective genes ranged from 1.0 to 3.2 depending on the parents used in the crosses. The presence of a major gene for resistance was not detected in the study. These results support the idea that brown patch resistance is quantitatively inherited.
Evaluation and Characterization of Seedling Resistances to Stem Rust Ug99 Races in Wheat–Alien Species Derivatives
Authors: Xu S. S. , Jin Y. , Klindworth D. L. , Wang R. R.‐C. , Cai X.
Published: October 2009

Stem rust (caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.), a devastating disease of wheat (Triticum aestivum L.), was effectively controlled worldwide for the past 50 yr by deployment of stem rust resistance (Sr) genes in wheat cultivars. However, a new stem rust race, TTKSK (known as Ug99 or TTKS) that emerged in eastern Africa, is a cause of concern because it has broad virulence to currently deployed Sr genes. To identify potentially new sources of effective Sr genes against Ug99, we evaluated and characterized the seedling responses to TTKSK of 62 wheat lines derived from crosses of common or durum wheat (T. turgidum L. ssp. durum) with the species Thinopyrum junceum, Th. intermedium, Th. bessarabicum, Th. elongatum, Th. ponticum, Elymus rectisetus, Aegilops caudata, and Ae. speltoides For stem rust evaluation, we first tested all lines for reactions to races TTTT and TTKSK. Lines initially showing resistance to TTKSK were then retested with eight races, including three races in the TTKS lineage (TTKSK, TTKST, and TTTSK) and five North American races (QFCS, QTHJ, RCRS, RKQQ, and TPMK). Thirty wheat–alien species derivatives had resistance to TTKSK, TTKST, and TTTSK. The comparisons of wheat–alien species derivatives and their parental lines for reactions to different races suggested that 12 partial amphiploids or amphiploids and four disomic addition lines may carry novel genes for stem rust resistance. These resistant lines represent materials for introducing stem rust resistance genes into wheat breeding.
Comparison of Weighting in Two‐Stage Analysis of Plant Breeding Trials
Authors: Möhring J. , Piepho H.‐P.
Published: October 2009

Series of plant breeding trials are often unbalanced and have a complex genetic structure. To reduce computing cost, it is common practice to employ a two‐stage approach, where adjusted means per location are estimated and then a mixed model analysis of these adjusted means is performed. An important question is how means from the first step should be weighted in the second step. Our objective therefore was the comparison of different weighting methods in the analysis of four typical series of plant breeding trials using mixed models with fixed or random genetic effects. We used four published weighting methods and proposed three new methods. Four evaluation criteria were computed to compare methods, using one‐stage analysis as benchmark. We found that the two‐stage analysis gave acceptable results with fixed genetic effects. When genetic effects were taken as random in stage two, in three of four datasets the two‐stage analysis gave acceptable results. In both cases differences between weighting methods were small and the best weighting method depended on the dataset but not on the evaluation criteria. A two‐stage analysis without weighting also produced acceptable results, but weighting mostly performed better. In the fourth dataset the missing data pattern was informative, resulting in violation of the missing‐at‐random (MAR) assumption in one‐ and two‐stage analysis. In this case both analyses were not strictly valid.
An Alternate Wetting and Moderate Soil Drying Regime Improves Root and Shoot Growth in Rice
Authors: Zhang Hao , Xue Yaguang , Wang Zhiqin , Yang Jianchnag , Zhang Jianhua
Published: October 2009

A major challenge in rice (Oryza sativa L.) production is to achieve the dual goal of increasing food production and saving water. This study aimed to investigate if alternate wetting and drying regimes could improve root and shoot growth and consequently increase grain yield and water use efficiency (WUE). Two rice varieties were field‐grown at Yangzhou, China in 2005 and 2006. Three irrigation regimes, alternate wetting and moderate soil drying (WMD, re‐watered when soil water potential reached −15 kPa at 15–20 cm depth), alternate wetting and severe soil drying (WSD, re‐watered when soil water potential reached −30 kPa), and a conventional irrigation (CI, continuously flooded), were imposed during the whole growing season. Compared with the CI, the WMD regime significantly increased, whereas the WSD regime reduced, root oxidation activity, cytokinin concentrations in roots and shoots, leaf photosynthetic rate, and activities of key enzymes involved in sucrose‐to‐starch conversion in grains. Grain yield of the two varieties, on the average, was increased by 11% under the WMD regime, and was reduced by 32% under the WSD regime when compared with that under the CI regime. Averaged WUE of the two varieties was increased by 55% under the WMD regime and 36% under the WSD regime. We conclude that a moderate wetting and drying regime can enhance root growth which benefits other physiological processes and result in higher grain yield and WUE.
Meta‐Analysis of QTL Associated with Fusarium Head Blight Resistance in Wheat
Authors: Liu Shuyu , Hall Marla D. , Griffey Carl A. , McKendry Anne L.
Published: October 2009

Quantitative trait loci (QTL) associated with resistance to Fusarium head blight (FHB), which is mainly caused by Fusarium graminearum Schwabe [telomorph: Gibberella zeae Schw. (Petch)], have been identified in wheat (Triticum aestivum L.) from different countries. Due to the differences of genetic backgrounds and analysis methods, the linked marker and significance levels of QTL are not consistent across studies. Such discrepancies make it difficult to select diagnostic flanking markers. Meta‐analysis has been used to estimate the confidence intervals (CIs) of QTL in plant and animal genomes. The objective of this study was to cluster 249 FHB resistance QTL identified in 46 unique lines from 45 studies based on the estimated QTL CI by meta‐analysis. A total of 209 QTL conditioning FHB resistance type I, II, III and IV were classified into 43 clusters on 21 chromosomes. Among them, 119 QTL were significant and 116 QTL explained more than 10% of phenotypic variation. There are 19 confirmed QTL located on chromosomes 3A, 5A, 7A, 1B, 3BS, 5B, 6B, and 2D. The results provide chromosome locations and linked markers for overlapping and unique QTL. Markers flanking QTL clusters can be used to pyramid diverse QTL more efficiently through marker‐assisted breeding.
Water Use by Five Warm‐Season Legumes in the Southern Great Plains
Authors: Rao Srinivas C. , Northup Brian K.
Published: October 2009

Growing warm‐season legumes during fallow periods associated with traditional continuous systems of winter wheat (Triticum aestivum L.) in the southern Great Plains (SGP) can provide supplemental forage, biological N, and protection from soil erosion, provided the legumes can tolerate drought stress and not deplete the available water in the soil profile. Our objective was to quantify water use by five species of pulse legumes {pigeon pea [(Cajanus Cajan (L.) Millsp.) cv. GA‐2], guar [Cyamopsis tetragonobloba (L.) Taub., cv. Kinman], cowpea [Vigna unguiculata (L.) Walp., cv. Chinese red], mung bean [Vigna radiate (L.) Wilcz., cv. Berkins], and soybean [Glycine max (L.) Merr., cv. Hutcheson (the control)]}. Seeds were inoculated and planted after wheat harvest in mid‐June 2003 through 2006. The amount of water in the upper 65 cm of the soil profile was measured on nine dates [from 45 d before planting legumes to 195 d since planting (DSP)]. Significant (P < 0.01) differences in soil water were recorded among treatments, dates, and years. Differences in soil water among fallow, cowpea, and mung bean were less following the 2003 and 2004 summer seasons and most noticeable in 2005 and 2006. Mung bean, guar, soybean, and pigeon pea used the greatest amounts of water in 2005, the wettest season, while cowpea and mung bean used the least in 2003. Mung bean, cowpea, and guar generated smaller water deficits and used less soil water, in three of four years, and could be effective in wheat‐summer legume rotations in the SGP.
Heterosis Decreasing in Hybrids: Yield Test Inbreds
Authors: Troyer A. Forrest , Wellin Eric J.
Published: October 2009

Yield testing finished inbreds to replace preliminary single‐cross corn (Zea mays L.) yield tests will increase rate of commercial hybrid yield gains. Studies have shown that heterosis decreased 25%/50 yr, 10%/60 yr, and 35%/100 yr. Natural selection and artificial selection by plant breeders for adaptedness have increased parental inbred and hybrid seed yields, whereas percentage heterosis decreased. Four studies have shown inbred yields increased 1.9 to 3.5 times faster than heterosis yields. Pioneer Hi‐Bred generates 700 new inbreds tested in 6000 single‐cross hybrids at 15 to 20 locations annually. Predicted, untested, newer hybrids are then made and tested extensively with commercial hybrids. Parental inbred yield testing is the next to last of several steps in hybrid development. Commercial hybrid development costs have increased logarithmically, whereas performance has increased linearly. Replacing preliminary testcross trials with finished‐inbred yield trials is more efficient. About 12,000 new finished inbreds can be evaluated annually with no testers and at least 50% fewer locations per inbred with the same testing effort as 700 new inbreds with testers. A calendar year per breeding cycle and annual production costs for 6000 hybrids will be saved. Corn yield trials detect stress susceptibility, which is more apparent in inbreds than in hybrids. Evaluation of more new inbreds will be conducive to increased genetic diversity that produces higher‐yielding hybrids.
Genotype × Environment Interactions of Hybrid and Varietal Rice Cultivars for Grain Yield and Milling Quality
Authors: Blanche Sterling B. , Utomo Herry S. , Wenefrida Ida , Myers Gerald O.
Published: October 2009

The study of genotype × environment interaction is critical for accurate cultivar evaluation in large multi‐environment trials. Cultivars that exhibit high levels of mean performance and stability across a wide range of environmental conditions are desirable for rice production. Pure‐line varietal and hybrid rice cultivars are commercially produced in the U.S.; however, little research has been conducted comparing their stability for grain yield and milling quality. In this study, 15 hybrid and varietal cultivars were grown in 10 environments from 2005 to 2007 to determine the performance and stability of rough rice yield, whole milled rice percentages, and whole‐grain rice yield. Stability was analyzed using the coefficient of variation, Shukla's Stability Variance statistic with environment means as a covariate, and the Cultivar Superiority Measure. The hybrid rice cultivars XP723 and CLXL730 were ideal for high and stable rough rice and whole‐grain rice yields on the basis of the cultivar superiority measure; however, for whole milled rice percentage alone, they were among the least desirable cultivars. Among the varietal cultivars, Catahoula and Jupiter were ideal cultivar selections for high and stable whole‐grain rice yields. The results of this study indicate that the stability and performance of hybrid and varietal cultivars differ according to the trait of interest.
Maize Kernel Oil and Episodes of Shading during the Grain‐Filling Period
Authors: Tanaka Walter , Maddonni Gustavo Ángel
Published: October 2009

Previous studies documented the stability of maize (Zea mays L.) kernel oil concentration for a wide range of kernel weights promoted by contrasting post‐flowering assimilate availabilities per kernel (i.e., source–sink ratios). These studies mainly modified the sink size with a low impact on the source size. In this study, we focused on kernel oil concentration response to source–sink ratio alterations promoted by different timings and intensities of shading during the effective grain‐filling period. Two crosses with contrasting kernel oil concentration (‘DK752’ × DK752 and DK752 × ‘5MG’) were tested. Kernel oil concentration was positively related to the embryo–kernel ratio (r = 0.96, P < 0.001) and embryo oil concentration (r = 0.94, P < 0.001) and crosses differed in both traits. Severe shading (85% reduction of incident solar radiation) at early stages of kernel growth reduced the final embryo–kernel ratio and the embryo oil concentration of both crosses. Contrarily, moderate shading (45% reduction of incident solar radiation) did not modify the kernel oil determinants. Kernel oil concentration and kernel weight declined when severe shading shortened the kernel growth period. Our results collectively sustain the hypothesis that maize kernel oil concentration is commonly sink‐limited. We established that kernel oil concentration of both crosses was reduced when post‐flowering plant growth rate per kernel was less than 50% of kernel growth rate.
Genetically Engineered Flax: Potential Benefits, Risks, Regulations, and Mitigation of Transgene Movement
Authors: Jhala Amit J. , Weselake Randall J. , Hall Linda M.
Published: October 2009

Flax (Linum usitatissimum L.) has been grown for more than 6000 years, primarily for oil and fiber. Advances in plant biotechnology have resulted in flax cultivars with increased herbicides resistance and there is potential to produce transgenic flax with seed oil containing fatty acids with nutraceutical properties. Flax oil is a rich source of α‐linolenic acid (ALA, 18:3cisΔ9,12,15), a precursor of the very long chain polyunsaturated fatty acids (VLCPUFA), eicosapentaenoic acid (EPA, 20:5cisΔ5,8,11,14,17), and docosahexaenoic acid (DHA, 22:6cisΔ4,7,10,13,16,19). Current research on medicinal applications of ω‐3 fatty acids, especially to reduce the risk of cardiovascular diseases and cancer, suggests that genetic modification of flax may provide substantial health benefits. There are concerns, however, with the commercialization of genetically engineered (GE) flax (which includes the potential movement of transgenes by pollen and seed, and subsequent introgression with weedy and wild relatives, impact on non‐target organisms, and changes in biodiversity). A prerequisite to the unconfined cultivation of transgenic flax is an environmental risk assessment analysis. In this paper, we discuss the history and current status of genetic transformations in flax, potential benefits and consequences of GE flax, and the government regulatory framework in Canada for regulating novel flax. Finally, we discuss the best management practices to mitigate transgene movement from transgenic flax. Our intent was to evaluate biology and agronomy to predict the environmental biosafety of GE flax before commercial cultivation.
Water Deficit, Heat Tolerance, and Persistence of Summer‐Dormant Grasses in the U.S. Southern Plains
Authors: Malinowski D. P. , Kigel J. , Pinchak W. E.
Published: October 2009

Summer‐dormant cool‐season grasses are being used in the Southern Plains of the United States in place of traditional summer‐active cultivars for high‐quality winter forage. One reason for this is the ability of cultivars with summer dormancy traits to tolerate increasing annual temperature, decreasing precipitation, and repeated severe summer droughts. Research on adaptation of these grasses and mechanisms of summer dormancy has been conducted at Vernon, TX, since 2000. The experimental location is in a semiarid, subtropical climate with bimodal rainfall pattern with peaks in May and September, and prolonged summer drought. Adaptation and persistence studies involved summer‐dormant and summer‐active cultivars of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), and hardinggrass (Phalaris aquatica L.). Summer‐active types of these grasses were not adapted to this environment and could not survive the first summer after planting. Summer‐dormant types were fully adapted and persisted for at least 5 to 8 yr, depending on species. The most adapted were tall fescue, hardinggrass, and to some extent orchardgrass [subsp. hispanica (Roth) Nyman]. Detailed studies have also been conducted by the Samuel Roberts Noble Foundation at Ardmore, OK. Both research centers have breeding programs for summer‐dormant grasses.
Summer Drought Survival Strategies and Sustainability of Perennial Temperate Forage Grasses in Mediterranean Areas
Authors: Volaire F. , Norton M. R. , Lelièvre F.
Published: October 2009

Perennial grasslands provide numerous agroenvironmental benefits due to continuous soil cover. In Mediterranean areas, chronic summer drought is expected to increase as a result of climate changes. Plant adaptations that protect meristematic tissues include dehydration delay, dehydration tolerance, and summer dormancy. Summer dormancy can only be reliably tested in plants not subjected to water deficit. Under summer irrigation, complete dormancy is manifested by cessation of growth in association with full senescence of foliage and induced dehydration of leaf bases. Incomplete dormancy occurs when leaf growth is partially constrained and associated with moderate levels of foliage senescence. Summer dormancy is under hormonal control and is induced under increasing photoperiod and temperature. Recent results show that drought cannot induce summer dormancy under early‐spring short days, although a water deficit under late‐spring long days reinforces it and could enhance drought survival. Dehydration tolerance and dormancy are independent phenomena. Summer dormancy has been correlated with superior survival after severe summer droughts in many perennial grass species. This trait has potential for improving cultivars able to meet agronomic and environmental goals.