bluuebunny/crossref_metadata_2025 huggingface dataset:
PREFERENCE FOR STARTING AND FINISHING BEHAVIOR PATTERNS
Authors: Shimp Charles P. , Sabulsky Sherry L. , Childers Leonard J.
Published: March 2006

Pigeon's key pecking was reinforced with food in two experiments in which the correspondence between preference for starting one of two reinforced behavior patterns and the likelihood of finishing it subsequently was examined. Reinforcers were scheduled according to concurrent schedules for two classes of interresponse times, modified such that reinforcers followed a center‐key peck terminating either a shorter interresponse time started by a left‐key peck or a longer interresponse time started by a right‐key peck. In Experiment 1, the times when reinforcers potentially were available were not discriminated, whereas in Experiment 2 they were. Absolute reinforced pattern durations were varied. The relative frequency of starting a particular pattern was highly correlated with relative frequency of that completed pattern in both experiments. Other relations between starting and finishing a pattern depended on whether reinforced interresponse times were discriminated. For instance, preference for starting a pattern sometimes correlated negatively with the likelihood of subsequently completing it. The present experiments are described as capturing part of the ordinary language meaning of “intention,” according to which an organism's behavior at one moment sets the occasion for an observer to say that the organism “intends” in the future to engage in one behavior rather than another.
GLOBAL INCREASE IN RESPONSE LATENCIES BY EARLY MIDDLE AGE: COMPLEXITY EFFECTS IN INDIVIDUAL PERFORMANCES
Authors: Myerson Joel , Hale Sandra , Hirschman Robert , Hansen Christine , Christiansen Bruce
Published: March 2006

Ten young women (age 20 to 22 years) and 10 middle‐aged women (age 36 to 44 years) served as subjects in choice reaction time, letter classification, and abstract matching‐to‐sample tasks. In each of seven conditions, the older group responded more slowly than the younger group. Age differences showed a complexity effect. That is, differences between the latencies of young and old subjects increased as the latency of the young subjects increased. Both linear and power functions accurately described the relation between the latencies of the middle‐aged and young adult groups. This was true not only for the relation between average latencies but also for the relation between corresponding quartiles of latency distributions. Similar results were observed at the individual level: All middle‐aged subjects showed complexity effects, and, for each middle‐aged subject, the relation between her latencies and those of the average young adult was well described by linear and power functions. These findings indicate that age‐related slowing is apparent by age 40, and that complexity effects are observable in individual performances. This slowing is global and not specific to particular tasks, as indicated by the fact that the latencies of older adults can be predicted directly from those of younger adults without regard to the nature of the task.
CONNECTIONIST MODELS OF CONDITIONING: A TUTORIAL
Authors: Kehoe E. James
Published: March 2006

Models containing networks of neuron‐like units have become increasingly prominent in the study of both cognitive psychology and artificial intelligence. This article describes the basic features of connectionist models and provides an illustrative application to compound‐stimulus effects in respondent conditioning. Connectionist models designed specifically for operant conditioning are not yet widely available, but some current learning algorithms for machine learning indicate that such models are feasible. Conversely, designers for machine learning appear to have recognized the value of behavioral principles in producing adaptive behavior in their creations.
NEUROLOGY AND NEUROPATHOLOGY OF SOMAN‐INDUCED BRAIN INJURY: AN OVERVIEW
Authors: Petras J. M.
Published: March 2006

Battlefield use of nerve agents poses serious medical threats to combat troops and to civilians in the immediate or adjacent environment. The experiments reported herein were carried out in the 1980s to help to define both the neurological and neuropathological consequences of exposure to the organophosphate nerve agent Soman. These data contributed to the scientific foundation for a program of drug development to find agents that would prevent or reduce the risk of injury to the central nervous system and specifically pointed to the importance of including an anticonvulsant in the treatment of agent exposure. Since these experiments were conducted, research efforts have continued to improve pretreatment and treatment, such as the inclusion of the anticonvulsant diazepam in the medical treatment of exposed personnel.
CONTEXT SPECIFICITY OF CONDITIONED‐REINFORCEMENT EFFECTS ON DISCRIMINATION ACQUISITION
Authors: Williams Ben A. , Dunn Roger
Published: March 2006

Pigeons were trained on a series of reversals of a simultaneous form discrimination in which the trial outcomes were separated from the choice responses by an 8‐s delay interval. Different conditions were defined by the stimuli occurring during the two halves of the delay interval. Discrimination learning was greatly facilitated by having differential stimuli during the delay following correct versus incorrect choices. When the differential stimuli appeared only at the midpoint of the delay, some facilitation occurred relative to when no different stimuli occurred, but there was substantially less facilitation than when the differential stimuli occurred immediately contingent on choice. A reversed‐stimulus condition, in which the stimulus at the onset of the delay following a correct choice was the same as that during the last segment of the delay following an incorrect choice, and the stimulus at the onset of the delay following an incorrect choice was the same as that preceding food during the last segment of the delay following a correct choice, also facilitated discrimination learning relative to the nondifferential stimulus conditions.
THE EFFECTS OF DIFFERING RESPONSE‐FORCE REQUIREMENTS ON FIXED‐RATIO RESPONDING OF RATS
Authors: Alling Ken , Poling Alan
Published: March 2006

Rats were exposed to two‐component multiple schedules of food delivery. In the first experiment, 15 responses were required to produce food in both components. A downward force of 0.25 N (25 g) was always required to operate the response lever in one component. In the other, the required force was 0.25, 0.50, 1.00, or 2.00 N (25, 50, 100, or 200 g). In the second experiment, 0.25 N of force operated the lever in one component, but in the other, the force requirement for five consecutive responses at the beginning, middle, or end of each ratio was increased from 0.25 to 2.00 N. In the third experiment, the number of responses required to produce food was reduced from 15 to 5, and then to 1. Again, the effects of altering response force from 0.25 to 2.00 N were examined. In general, as response force increased in all experiments, mean response rates decreased and mean interresponse times increased.
ACTION AT A TEMPORAL DISTANCE: COMPONENT TRANSITION AS THE RELATIONAL BASIS FOR SUCCESSIVE DISCRIMINATION
Authors: White K. Geoffrey
Published: March 2006

In a successive discrimination, red and green hues signaled component variable‐interval schedules. The exponent of the power function relating ratios of responses in the red and green components to ratios of reinforcers provided a reinforcement‐free measure of discrimination or stimulus control. Responses were recorded in successive 10‐s subintervals of the 50‐s components. The power‐function exponent decreased systematically with increasing time since component transition in most conditions of five experiments. This reduction was not influenced by the absolute rate of reinforcement, consistent with the interpretation of the exponent as a measure of stimulus control. A reduction in the overall level of stimulus control by increasing the duration of response‐produced keylight offset did not influence the decrease in discrimination with increasing time since component transition. The results support the conclusion that discriminative responding in successive discriminations is governed by several sources of stimulus control including delayed control by component transition.
FOOD AND WATER INTAKE AS FUNCTIONS OF RESOURCE CONSUMPTION COSTS IN A CLOSED ECONOMY
Authors: Mathis Carl E. , Johnson Deanne F. , Collier George
Published: March 2006

In two experiments, rats living in a closed economy were offered continuous, concurrent access to four resources: food, water, a nest, and a running wheel. Costs of consuming food and water were imposed with bar‐press requirements, and the price of either one or both resources was raised. As the consumption cost increased, less was consumed in each bout of resource use. Bout frequency increased, but not sufficiently to compensate for the fall in bout size, and total intake fell. Food and water tended to be complementary resources, in that as intake of one fell with its price, intake of the other also decreased. This interaction was accounted for by the defense of the ratio of body water to lean body mass. As amount consumed decreased, increases in feed efficiency (weight gain per unit of food ingested) and the use of stored calories compensated for the reduced energy intake. There was evidence of competition between feeding and drinking at the higher costs: When both commodities were expensive, the decline in the intake of each one was greater than when only one commodity was expensive. Although the time spent nesting, running, and in unmonitored activity was adjusted when feeding or drinking took more of the rat's day, there was no particular activity that was sacrificed.
RESPONSE‐DEPENDENT PRECHOICE EFFECTS ON FORAGING‐RELATED CHOICE
Authors: Williams Wendy A. , Fantino Edmund
Published: March 2006

Three experiments explored the influence of prechoice events on pigeons' preference. In two of three studies, a fixed‐interval 200‐second prechoice period preceded the initial links of a concurrent chain in which outcomes differed either (a) in terms of the delay to food or (b) in terms of amount of food and delay to food. In Experiment 3, the prechoice period preceded the initial links that provided a choice between a small single food presentation and two identical, more delayed food presentations. In all three cases, obtained choice proportions did not vary as a function of prechoice duration. These results suggest that a local‐contextual view adequately describes the foraging context; they also have implications for the appropriate formulation of the delay‐reduction theory of conditioned reinforcement and rate‐maximizing views of optimal foraging theory.
Association Between Coping With Anger and Feelings of Depression Among Youths
Authors: Goodwin Renee D.
Published: March 2006

Objectives. I examined the association, among youths, between coping behavior when angry and depression.

Methods. Data were drawn from the Health Behavior in School-Aged Children in the United States survey (n=9938). Factor analyses and multivariate logistic regression analyses were used to determine the association between self-reported coping behavior when angry and depression. Gender-specific models were run.

Results. Factor analysis of 11 coping behaviors indicated a 4-factor solution: substance use, physical activity, emotional coping behavior, and aggressive behavior. Substance use, emotional coping, and aggressive behavior coping were associated with increased likelihood of depression, whereas physical activity was associated with decreased likelihood of depression. Male youths were more likely to engage in physical activity and were less likely to feel depressed.

Conclusions. These data provide preliminary evidence of a link between specific coping behavior when angry and the likelihood of depression among youths. Whether these associations may be useful in identifying youths at risk for depression cannot be determined from these data alone but may be an important area for future study.
Biplot Analysis of Genotype by Environment Interaction for Barley Yield in Iran
Authors: Dehghani H. , Ebadi A. , Yousefi A.
Published: March 2006

Cultivar evaluation and mega‐environment identification are the most important objectives of multienvironment trials (MET). The objective of this study was to explore the effect of genotype and genotype × environment interaction on the grain yield of 19 barley (Hordeum vulgare L.) genotypes via GGE (genotype plus genotype × environment) biplot methodology. Experiments were conducted using a randomized complete block design with four replications for 3 yr at 10 locations. The biplot analysis identified three barley mega‐environments in Iran. The first mega‐environment contained locations Khoy, Mashhad, Miandoab, Karaj, and Nyshabour, where genotype Bahtim7‐D1/79‐w40762 was the winner; the second mega‐environment contained locations Tabriz, Hamedan, Ardabil, and Arak, where genotype Walfajre/W1‐2291 was the winner. The location of Zanjan made up the other mega‐environment, with 73‐M4‐30 as the winner. Genotypes Bahtim7‐D1/79‐w40762 and Walfajre/W1‐2291 had the highest mean yield and genotype K‐201/3‐2 had the poorest mean yield. The estimated relative yield of genotypes at Karaj station shows that genotype Bahtim7‐D1/79‐w40762 had the highest yield and genotype Owb70173‐2H‐OH had the poorest. The performances of genotypes Star/Alger and K‐201/3‐2 were highly variable, whereas genotypes Cossak/Gerbel/Harmal and Toji“S”/Robur were highly stable. The results of this study indicate the possibility of improving progress from selections under diverse location conditions by applying the GGL (genotype plus genotype × location) biplot methodology.
Comparison of Site‐Specific Management Zones: Soil‐Color‐Based and Yield‐Based
Authors: Hornung A. , Khosla R. , Reich R. , Inman D. , Westfall D. G.
Published: March 2006

Numerous techniques of management zone delineation have been studied; however, few comparisons between techniques exist in the literature. The objectives of this study were: (i) to determine how consistently two management zone delineation techniques (a soil‐color‐based management zone [SCMZ] technique and a yield‐based management zone [YBMZ] technique) characterize regions of high, medium, and low grain yield; and (ii) to compare the relative accuracies with which the two management zone delineation techniques characterize the grain yield within low, medium, and high productivity potential management zones. This study was conducted for three site years in northeastern Colorado. Management zones were delineated before planting. The SCMZ technique used: (i) bare‐soil imagery, (ii) topography, and (iii) farmer's experience. The YBMZ relied on: (i) bare‐soil imagery, (ii) soil organic matter, (iii) cation exchange capacity, (iv) soil texture, and (v) the previous season's yield map. Grain yields ranged from 6.9 to 15.5 Mg ha−1across all site years. Grain yields were significantly different between SCMZ zones for all site years. Grain yield in the SCMZ high zones were up to 1.88 Mg ha−1higher than YBMZ high zones. Areal agreements for the SCMZ technique were 37, 41, and 45% for Site Years I, II, and III. Based on the approaches used in this study to classify grain yield patterns, the SCMZ technique was found to be relatively better than the YBMZ technique.
An Assessment of Phenotype Selection for Linolenic Acid Using Genetic Markers
Authors: Beuselinck P. R. , Sleper D. A. , Bilyeu K. D.
Published: February 2006

Marker assisted selection (MAS) procedures potentially can make breeding more efficient, as genotypes can be identified before pollination allowing breeders to cross or backcross only suitable materials. Our objective was to assess the accuracy of our phenotypic selections in soybean [Glycine max(L.) Merr.] for linolenic acid using molecular markers specific for mutations in two fatty acid desaturase genes, GmFAD3Aand GmFAD3CThe markers were not available earlier in the selection process and were used retrospectively to determine that phenotypic selection for seed linolenic acid ≤ 35 g kg−1oil was successful in capturing genotypes homozygous for mutant alleles at both loci, but phenotypic selection was not perfect. Chemical analysis for seed linolenic acid concentration was not an accurate predictor of genotype. The advancement of heterozygotes reduced the selection efficiency relative to what would have been possible using molecular markers specific for mutations in the two fatty acid desaturase genes. Errors are thought to have derived from inaccurate sample tracking or identification, contamination, or errors in chemical analyses. Use of mutation‐specific molecular markers to identify F2lines homozygous for mutant alleles in GmFAD3Aand GmFAD3C, combined with diligence in reducing sampling errors, would eliminate the need for chemical testing for linolenic acid content in subsequent generations where screening can emphasize other traits.
Quantitative Trait Loci for Genetically Correlated Seed Traits are Tightly Linked to Branching and Pericarp Pigment Loci in Sunflower
Authors: Tang Shunxue , Leon Alberto , Bridges William C. , Knapp Steven J.
Published: February 2006

The seed oil concentrations of large‐seeded, low‐oil and small‐seeded, high‐oil sunflower (Helianthus annuus L.; x = 17) cultivars differ by 180 to 280 g kg−1 We identified quantitative trait loci (QTL) for seed oil and other seed traits in a low‐ × high‐oil (RHA280 × RHA801) recombinant inbred line (RIL) mapping population segregating for apical branching (B), phytomelanin pigment (P), and hypodermal pigment (Hyp) loci. B, Hyp, and P mapped to linkage groups 10, 16, and 17, respectively. The seed oil concentrations of RHA280 and RHA801 were 254 and 481 g kg−1, respectively. Composite interval mapping (CIM) identified 40 QTL for seed oil concentration, 100‐seed weight, seed length, width and depth, kernel and pericarp weight, and kernel‐to‐pericarp weight ratio in 14 DNA marker intervals on 10 of 17 linkage groups. Twenty‐four of the QTL were tightly linked to B, P, and Hyp and may have been partly or wholly caused by the pleiotropic effects of B, P, and Hyp Multilocus QTL analyses were performed using B, P, Hyp, and four DNA marker loci as independent variables in mixed linear models. Seventy percent of the additive effects (39/56) and 42% of the additive × additive and additive × additive × additive effects (189/448) were significant (p < 0.05). The linked, pleiotropically acting, and epistatically interacting QTL identified for seed traits in RHA280 × RHA801 were presumably targeted by selection in the transition from large‐seeded, low‐oil to small‐seeded, high‐oil cultivars in sunflower.
Aegilops Species from Semiarid Areas of Lebanon: Variation in Quantitative Attributes under Water Stress
Authors: Baalbaki R. , Hajj‐Hassan N. , Zurayk R.
Published: February 2006

Aegilops species in semiarid areas constitute potentially important gene sources for abiotic stress resistance of domesticated Triticum species. Drought tolerance of several Aegilops species was evaluated, and the structure and extent of variation in quantitative attributes of those species when subjected to different degrees of water stress was evaluated. Twenty‐one populations belonging to six species were collected: Ae biuncialis Vis., Ae cylindrica Host, Ae geniculata Roth, Ae markgrafii (Greuter) Hammer, Ae triuncialis L., and Ae vavilovii (Zhuk.) Chennav. Quantitative attributes, namely above‐ground dry weight, plant height, tillers per plant, days to maturity, productive tillering, spike length, kernels per spike, seed number, seed weight, and yield, were evaluated at three levels of moisture stress. On the basis of changes in measured quantitative attributes under different levels of drought stress, Ae geniculata and Ae. markgrafii were found to be the most drought tolerant species. Attributes accounting for most of the variation under different levels of water stress were total seed number, seed weight per spike, total number of tillers, and productive tillering capacity, although the extent of each attribute's variation depended on water stress level. Under severe water stress, the ability of plants to produce many fertile tillers with few large seeds seems to be an important adaptive mechanism which should be considered in evaluating plants for drought tolerance.
Bayesian Modeling of Heterogeneous Error and Genotype × Environment Interaction Variances
Authors: Edwards Jode W. , Jannink Jean‐Luc
Published: February 2006

An important assumption in the analysis of multienvironment cultivar trials is homogeneity of error and genotype × environment interaction variances. When variances are heterogeneous, the best estimators of performance are obtained by weighting inversely to variance components. However, because variances are almost never known and must be estimated, the additional error introduced into the model from estimating many variances may cause weighted estimators to perform poorly. Our objective was to test a Bayesian approach to estimating heterogeneous error and genotype × environment interaction variances. A Bayesian model for multienvironment yield trials that includes a linear model for error and genotype × environment interaction variances was applied to yield data from the Iowa State University Oat Variety Trial for the years 1997 to 2003. The Bayesian approach revealed that error variances were highly heterogeneous among environments and that genotype × environment interaction variances were heterogeneous among environments and genotypes. Incorporation of heterogeneity of variances significantly decreased estimates of marginal error, genotypic, and genotype × environment variance components, with the largest change being a reduction in the marginal genotype × environment interaction variance. Repeatabilities were higher in the heterogeneous variance model but not at a high level of statistical significance. Genotype‐specific estimates of genotype × environment interaction variances were correlated with estimated genotypic yields and heading dates, providing biological validity to our estimates of genotype‐specific estimators of genotype × environment interaction variances as stability estimators.
Kernel Set in Maize Hybrids and Their Inbred Lines Exposed to Stress
Authors: Echarte Laura , Tollenaar Matthijs
Published: February 2006

Heterosis for grain yield in maize (Zea mays L.) has been associated with heterosis for kernel number. The objective of this study was to elucidate physiological traits underlying the superior kernel no. establishment in hybrids in comparison with that in their inbred lines, using the relationship between kernel no. plant−1 (KNP) and plant growth rate during the critical period of approximately 30 d bracketing silking (PGRS). Experiments were performed at the Arkell Research Station near Guelph, ON, Canada, during 2003 and 2004. Maize was grown at three levels of water availability (100, 75, or 60% of daily transpiration) during a period bracketing silking and at two plant densities (6 and 10 plants m−2) without nutrient limitations to generate a range of levels of resource availability plant−1 Kernel no. plant−1 was greater in the hybrids than in their parental inbred lines at all levels of resource availability, which was attributable mainly to a greater kernel set per unit PGRS in the hybrids. Greater kernels set per unit PGRS in hybrids vs. their inbred lines resulted from one or more of the following features: (i) low threshold of PGRS for kernel set, (ii) high kernel set response to PGRS increments at low resource availability plant−1, and (iii) high potential kernel number. Heterosis for kernel set was associated with heterosis for ear growth rate during the critical period for kernel set bracketing silking (EGRs) to varying degrees, and the extent of the association varied with inbred line–hybrid combination and level of resource availability plant−1
Field Evaluation of Green Stem Disorder in Soybean Cultivars
Authors: Hill Curtis B. , Hartman Glen L. , Esgar Ralph , Hobbs Houston A.
Published: February 2006

Green stem is a disorder of soybean [Glycine max (L.) Merrill] that causes the stems to remain green, nonsenescent, and moist, although pods and seeds are fully ripe and dry. The disorder is a nuisance for producers because it complicates harvesting of soybeans by significantly increasing the difficulty in cutting the affected plants during harvest. The cause of the disorder is unknown; however, differences in relative sensitivity to the disorder have been observed. The primary objective of this research was to evaluate the relative sensitivity among commercial or near‐commercial cultivars from private and public soybean breeding organizations in replicated variety tests in Illinois. In 31 tests at Dekalb, Monmouth, and Urbana, IL, during 2001 to 2004, 1187 different MG I (maturity group)‐MG IV conventional and glyphosate[N‐(phosphonomethyl)glycine]‐tolerant, cultivars were visually evaluated. There were significant differences in sensitivity among cultivars in 29 of the 31 tests, indicating that genetic variability among cultivars for green stem sensitivity exists. This variability may provide a basis for breeding for low sensitivity to the green stem disorder. Total levels of green stem disorder incidence varied over years and locations. Herbicide management systems did not appear to affect the levels of green stem incidence.
Development of Canopy Reflectance Algorithms for Real‐Time Prediction of Bermudagrass Pasture Biomass and Nutritive Values
Authors: Starks Patrick J. , Zhao Duli , Phillips William A. , Coleman Samuel W.
Published: February 2006

Timely assessments of forage biomass production and nutritive values during the growing season are important for livestock managers to make decisions for adjusting stocking rate and pasture management. Remote sensing of canopy reflectance may provide a rapid and inexpensive means of estimating pasture nutritive values and biomass. The objective of this study was to determine the relationships between neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) concentration, biomass, and CP availability of bermudagrass [Cynodon dactylon (L.) Pers.] pastures and canopy reflectance. An experiment was conducted in the 2002 and 2003 growing seasons using three bermudagrass pastures of ‘Midland’, ‘Ozarka’, and an experimental hybrid, 72x12–12. Pasture CP concentration, biomass and CP availability correlated linearly with the reflectance ratios of R605/R515, R915/R975, and R875/R725 (0.44 ≤ r2 ≤ 0.63) as well as with the first derivatives of reflectance with wavebands centered at 545, 935, and 755 nm (0.49 ≤ r2 ≤ 0.68). Linear equations between each forage variable and the ratios or derivatives of reflectance were developed on the basis of data pooled across years, plant genotypes, and sampling dates. Validation of developed equations indicated that the CP concentration, biomass, and CP availability could be predicted by either the ratios or derivatives of the reflectance. Pasture NDF and ADF had lower correlation with canopy reflectance than other measured variables. Our results suggest that two‐narrow‐waveband reflectance ratios or the first derivatives in visible and near‐infrared spectral regions can be used for real‐time and nondestructive prediction of forage productivity and CP content in bermudagrass pastures.
Identifying Discriminating Locations for Cultivar Selection in Louisiana
Authors: Blanche Sterling B. , Myers Gerald O.
Published: February 2006

Plant breeders generally conduct the selection phase of their program at few locations, mainly on the basis of geography and resource limitations. We conducted this study to identify test locations that optimize genotype selection on the basis of discriminating ability and representativeness. GGE Biplot Pattern Explorer was used to rank six test locations in Louisiana for cotton (Gossypium hirsutum L.) lint yield and fiber length using data from the 1993 to 2003 Louisiana Official Variety Trials (early and medium maturity). Biplots were generated and distances between the “ideal” and actual test locations were measured. Locations with shorter distances were closer to the ideal location and were considered more desirable test locations for the traits of interest. Each test location's distance was standardized by the mean distance of all locations for each biplot. For lint yield, on the basis of its close proximity to the ideal test location and the low standard deviation, the most desirable selection location was St. Joseph loam (Commerce silt loam; fine‐silty, mixed, nonacid, thermic, Aeric, Fluvaquent). Winnsboro nonirrigated and Bossier City were not good selection locations for lint yield. For fiber length, Winnsboro irrigated was ranked first and St. Joseph loam was ranked third. Winnsboro nonirrigated was ranked sixth. A composite distance, reflecting the distance between the actual and “ideal” location for lint yield weighted at 60% and fiber length weighted at 40%, was used to determine the desirability of test locations on the basis of simultaneous selection for lint yield and fiber length. St. Joseph loam ranked first, Winnsboro irrigated ranked second, and Winnsboro nonirrigated ranked sixth. St. Joseph loam or Winnsboro irrigated should be used for selecting cultivars for lint yield and fiber length. Winnsboro nonirrigated should not be used for selecting cultivars because of its low level of discrimination and unique behavior.
Genotypic Variation for Stem Reserves and Mobilization in Wheat: I. Postanthesis Changes in Internode Dry Matter
Authors: Ehdaie B. , Alloush G. A. , Madore M. A. , Waines J. G.
Published: February 2006

Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on current photosynthesis. We evaluated the hypothesis that internode length, weight, and specific weight of genotypes affect accumulation and mobilization of stem reserves. This knowledge might complement selection in stressful environments. Genotypic variation for internode characteristics and their effects on dry matter accumulation and mobilization were measured at 10‐d intervals in 11 diverse wheat cultivars grown under well‐watered and droughted field conditions across 2 yr. Relationships among internode characteristics and accumulation and mobilization of stem reserves were determined. The main effect of year, irrigation, genotype, and harvest date and genotype × harvest date interaction were significant. Internode length, weight, and specific weight were reduced under drought. Mobilized dry matter from peduncle, penultimate, and the lower internodes ranged from 43 to 171, 81 to 272, and from 198 to 474 mg, respectively. Mobilized dry matter was less in well‐watered than in droughted conditions for peduncle (93 vs. 110 mg) but not for penultimate (173 vs. 143 mg) and the lower internodes (331 vs. 304 mg). Drought increased mobilization efficiency, expressed as percentage of maximum dry mater mobilized, in the peduncle, penultimate, and the lower internodes by 65, 11, and 5%, respectively. Stem maximum specific weight was correlated (r = 0.64) with stem mobilized dry matter. Balanced partitioning of stem length into upper and lower internodes and internode maximum specific weight are important in genotypic accumulation and mobilization of stem reserves in wheat.
Variation in the U.S. Photoperiod Insensitive Sorghum Collection for Chemical and Nutritional Traits
Authors: Hooks Tisha , Pedersen J. F. , Marx D. B. , Vogel K. P.
Published: February 2006

Screening germplasm for chemical and nutritional content can be expensive and time consuming. Near infrared spectroscopy (NIRS) and application of geostatistical models can make screening more efficient. The objectives of this study were to utilize these technologies to: (i) generate chemical and nutritional values for the U.S. photoperiod insensitive sorghum collection, (ii) describe variability for those traits, (iii) identify accessions in the highest and lowest 1% for each trait, and (iv) describe relationships among the accessions. Accessions were grown at Ithaca, NE, during 2001 and 2002. Samples of grain were scanned and NIRS equations developed for starch, fat, crude protein, acid detergent fiber, and phosphorus. The NIRS generated values for each accession can be accessed on GRIN at http://www.ars‐grin.gov/cgi‐bin/npgs/html/desclist.pl?69; verified 22 November 2005. The highest and lowest 1% of accessions was identified for each trait by best linear unbiased predictors (BLUPs). Means and standard deviations for observed values and variances due to accessions were calculated. Rank correlations between BLUPs and observed values ranged from r = 0.82 to r = 0.92. Principal component analysis showed that much of the variation is attributable to a contrast of starch with a weighted average of fat, crude protein, acid detergent fiber, and phosphorus. Cluster analyses showed clusters on the basis of canonical values, but no geographical, taxonomical, or morphological interpretation of the clusters was apparent.
Genetic Diversity in the Core Subset of the U.S. Red Clover Germplasm
Authors: Mosjidis J. A. , Klingler K. A.
Published: February 2006

Biochemical diversity present in accessions of the red clover (Trifolium pratense L.) U.S. core subset is unknown. Its isozyme characterization would facilitate the study of relationship among accessions and assist in the identification of unique accessions and duplicates and in the detection of genetic differences among accessions. This study was undertaken to assess genetic diversity in the core subset using the isozymes esterase, β‐glucosidase, phosphoglucomutase, peroxidase, diaphorase, phosphoglucoisomerase, and superoxide dismutase. Ten isozyme loci with 30 alleles were detected. All loci were polymorphic in at least one accession. Percentage polymorphic loci within populations ranged from 50 to 100% with an average of 77.5%. At the species level, the number of alleles per polymorphic locus was 3.00, and the effective number of alleles per locus was 1.81. Within accession averages were 2.75 and 1.66, respectively. The core subset had a large amount of genetic diversity. Most accessions were different from each other except PI 207972 and PI 251564, PI 217507, and PI 229799 that were alike. One accession, PI 235867, was not a red clover. Most accessions (56) were in Hardy‐Weinberg equilibrium, and thus they are more likely to maintain genotypic and allelic frequencies when increased. Genetic diversity at the species level was high and there was nearly twice as much variability among the wild populations as among the cultivars or landraces included in the core subset.
Virulence of Two Russian Wheat Aphid Biotypes to Eight Wheat Cultivars at Two Temperatures
Authors: Jyoti J. L. , Qureshi J. A. , Michaud J. P. , Martin T. J.
Published: February 2006

Biotype 2 of the Russian wheat aphid, Diuraphis noxia (Mordvilko), is virulent to both sources of resistance presently available in commercial wheat, Triticum aestivum L. The performance of biotype 2 was compared with that of biotype 1 on eight wheat cultivars at two constant temperatures, and the plants were evaluated for overall damage and leaf rolling. Colonies of biotype 2 grew an average of 2.3 and 24.9 times faster in the first and second generation, respectively, than did their biotype 1 counterparts at 20°C, reaching 80 to 125 aphids per plant after 20 d, compared with 10 to 31. The no. of aphids per plant at 10 and 20 d after infestation displayed a significant biotype–temperature interaction. There was also a biotype–temperature interaction for plant damage at 10 d, and for damage and leaf rolling at 30 d. After 20 d at 24°C, damage ratings ranged from 7.3 to 8.6 on a scale of 1.0 to 9.0, and leaf rolling ranged from 2.4 to 2.9 on a scale of 1.0 to 3.0 for biotype 2, whereas values for biotype 1 ranged from 2.8 to 5.1 and 1.4 to 2.2, respectively. There were no differences among cultivars in plant damage or leaf rolling induced by biotype 2, and ratings of both were higher than for biotype 1 in all cultivar–temperature combinations. Biotype 2 D. noxia has overcome both Dn4‐ and Dny‐based sources of resistance, was more virulent than biotype 1 to all the cultivars tested, and induced plant injury more rapidly than biotype 1, especially at higher temperatures.
Fine Mapping of a Seed Protein QTL on Soybean Linkage Group I and Its Correlated Effects on Agronomic Traits
Authors: Nichols D. M. , Glover K. D. , Carlson S. R. , Specht J. E. , Diers B. W.
Published: February 2006

Soybean [Glycine max (L.) Merr.] is primarily grown as a source of protein and oil. A quantitative trait locus (QTL) controlling seed protein concentration was previously mapped to linkage group (LG) I of soybean. The objectives of this study were to fine map the QTL and to determine if additional recombination could reduce the inverse phenotypic relationship between seed protein concentration and yield and oil concentration. The fine mapping was done with two sets of backcross populations that were tested in the field and with genetic markers. These populations were developed by the introgression of a high protein allele from the Glycine soja Sieb and Zucc. plant introduction (PI) 468916 into the genetic background of the breeding line A81–356022. The first set (Set 1) included three populations of backcross‐four (BC4) lines, and the second set (Set 2) included four populations of BC5 lines. The populations segregated for different segments of the genomic region where the QTL maps. Tests of the two sets of populations resulted in the localization of the QTL for protein and oil to a 3‐cM interval between the simple sequence repeat (SSR) marker Satt239 and the amplified fragment length polymorphism (AFLP) marker ACG9b. The results from the agronomic trait evaluations were inconsistent, making it difficult to definitively conclude whether the protein QTL controls these other traits through pleiotropy.
Identification of Quantitative Trait Loci for δ13C and Productivity in Irrigated Lowland Rice
Authors: Laza Ma. R. , Kondo M. , Ideta O. , Barlaan E. , Imbe T.
Published: February 2006

Stable carbon isotope ratio (δ13C) in plants has been suggested as a useful indicator for cumulative Ci/Ca signature in a leaf, water use efficiency, and crop productivity, and is known to have genotypic variation in rice (Oryza sativa L.). We conducted a field study to identify quantitative trait loci (QTLs) for δ13C and other related leaf traits, such as leaf N, specific leaf area, and SPAD value, using recombinant inbred lines derived from an indica × japonica cross grown under flooded conditions. We also examined the genetic associations of δ13C with yield, yield components, and biomass productivity. Putative QTLs for δ13C were identified on chromosomes 2, 4, 8, 9, 11, and 12 across plant parts, stages, and years. Differential expression of QTL for δ13C among stages suggests that each QTL had different functions by stages. The QTLs for δ13C were associated with a few colocated QTLs for leaf traits indicating that their physiological and genetic associations with leaf traits may be complex. Values of δ13C at maturity were negatively correlated with harvest index and grain yield. However, genetic association of these traits could not be clarified due to the absence of co‐located QTLs. Further examination would be useful to elucidate the physiological and morphological functions of QTLs for δ13C found in this study.
Translational Fusion Hybrid Bt Genes Confer Resistance against Yellow Stem Borer in Transgenic Elite Vietnamese Rice (Oryza sativa L.) Cultivars
Authors: Ho N. H. , Baisakh N. , Oliva N. , Datta K. , Frutos R. , Datta S. K.
Published: February 2006

We have shown the efficacies of translationally fused gene (cry1Ab‐1B) under the control of maize ubiquitin promoter and hybrid Bt gene (cry1A/cry1Ac) driven by rice Actin‐1 promoter against the yellow stem borer (Scirpophaga incertulas Walker, YSB) insect in rice (Oryza sativa L.). The integration, expression, and functionality of the transgenes were confirmed by Southern, western, and insect bioassay. The bioassay results correlated with the molecular data. The amount of Bt protein (within the range of 0.8–1.3% of the total soluble protein) in the transgenics was sufficient to cause 100% mortality of the neonate larvae of YSB within 1 wk of infestation. The transgenic plants expressing the foreign Bt protein were normal in phenotype with as good seed setting as the nontransgenic control plants.
Risk Assessment for Transgenic Sorghum in Africa: Crop‐to‐Crop Gene Flow in Sorghum bicolor (L.) Moench
Authors: Schmidt Markus , Bothma Gurling
Published: February 2006

A crop‐to‐crop gene flow risk assessment study was conducted with Sorghum bicolor subsp. bicolor to estimate the impact of transgenic sorghum in (South) Africa. The trial was conducted with a central sorghum field (30 × 30 m) with male fertile donor plants that was surrounded by eight arms planted with male sterile recipient plants at a distance of 13 to 158 m from the central field. Gene flow was relatively high within the first 40 m and relatively low beyond that distance, but gene flow was detected even at the greatest distance investigated (158 m). The average hybridization or outcrossing rate for male sterile plants was 2.54% at 13 m, below 1% at a distance of 26 m or greater, and eventually dropping to 0.06% at 158 m. Outcrossing rates are expected to be even lower for male fertile plants, which were not investigated in this study. Mathematical models were used to estimate the maximum gene flow distance that is expected to be between approximately 200 and 700 m. These values are in line with observational data from sorghum plant breeders, who use an isolation distance of 100 m to achieve less than 1% genetic pollution. On the basis of the presence of fully fertile crop wild relatives and the weedy relative johnsongrass [S. halepense (L.) Pers.], which may form hybrids with crop sorghum, and on the fact that gene flow takes place, there is strong evidence that introgression of genetically modified‐ (GM)‐sorghum into crops and crop wild relatives will take place once GM‐sorghum is deployed.
Genetic Analysis of Corn Kernel Chemical Composition in the Random Mated 10 Generation of the Cross of Generations 70 of IHO × ILO
Authors: Clark Darryl , Dudley John W. , Rocheford Torbert R. , LeDeaux John R.
Published: February 2006

To identify and characterize quantitative trait loci (QTL) affecting oil, protein and starch concentration in the corn (Zea mays L.) kernel, plants from Generation 70 of the Illinois High Oil (IHO) and Illinois Low Oil (ILO) populations, previously developed by divergent selection for kernel oil concentration, were crossed. The cross was random mated 10 generations and selfed two generations to develop 500 F1RM10S2 lines. The lines per se and their testcross progenies were evaluated at three locations with two replications for 2 yr. Genotypes were evaluated using 479 SNP markers on a bulk of kernels from each line. Since the parent plants used to make the original cross were not available for genotyping, a multivariable optimization procedure was developed to estimate parental population parameters required for QTL mapping. Simple interval mapping was performed with software specially developed to account for the complex mating structure and the fact that the initial cross was made between populations. Correlations and signs of QTL effects suggest development of high oil–high starch lines would be difficult but that it should be possible to develop high oil–high protein lines. The identification of a large number of QTL (at least 40 each for oil, protein, and starch) with small effects has implications for breeding for improved corn chemical composition.
Two Genes from Soybean Encoding Soluble Δ9 Stearoyl‐ACP Desaturases
Authors: Byfield G. E. , Xue H. , Upchurch R. G.
Published: February 2006

The Δ9 stearoyl acyl‐carrier protein desaturase (SACPD) gene of soybean [Glycine max (L.) Merrill] encodes a soluble enzyme that converts stearic to oleic acid. Understanding the regulation of SACPD expression and enzyme activity are thus important steps toward developing soybean lines with altered stearic or oleic acid content. Using primers designed to a G. max SACPD cDNA sequence, a 3648‐bp product was cloned and sequenced from the genome of cultivar Dare. Comparison of the third SACPD exon protein sequence with other available Glycine SACPD sequences revealed unique amino acid variability at positions 310 and 313. Sequence‐specific primers were designed for Real‐time RT‐PCR (reverse transcriptase‐polymerase chain reaction) for this region of exon 3. Diagnostic and specific products were recovered with these primers using Dare cDNA template and Dare genomic DNA. Sequencing of a second genomic clone from Dare confirmed that there were two SACPD genes, designated A and B, in this cultivar. Survey of the genomes of 51 soybean lines and cultivars with PCR and the gene‐specific primers indicated that all 51 had both A and B Differences between SACPD‐A and ‐B transcript abundance in soybean tissues, while quantifiable, were not dramatic. SACPD‐A and ‐B transcript accumulation for three seed developmental stages between R5 and R6 was essentially equal. Biochemical analysis of the proteins encoded by these two SACPD genes may reveal whether the amino acid variability uncovered in this study has any relation to enzyme activity.
Sampling Strategies for Conserving Maize Diversity When Forming Core Subsets Using Genetic Markers
Authors: Franco Jorge , Crossa José , Warburton Marilyn L. , Taba Suketoshi
Published: February 2006

Core subsets can be formed on the basis of molecular markers and different sampling strategies. This research used genetic markers on three maize data sets for studying 24 stratified sampling strategies to investigate which strategy conserved the most diversity in the core subset as compared with the original sample. The strategies were formed by combining three factors: (i) two clustering methods (UPGMA and Ward), based on (ii) two initial genetic distance measures, and using (iii) six allocation criteria [two based on the size of the cluster and four based on maximizing distances in the core (the D method) used with four diversity indices]. The objectives were (i) to study the influence of these factors and their interaction on the diversity of the core subsets and (ii) to compare the 24 stratified sampling strategies with the M strategy implemented in the MSTRAT algorithm. Success of each strategy was measured on the basis of maximizing genetic distances (Modified Roger and Cavalli‐Sforza and Edwards distances) and genetic diversity indices (Shannon index, proportion of heterozygous loci, and number of effective alleles) in each core. Twenty independent stratified random samples were obtained for each strategy using a sampling intensity of 20% of the collection. For the three data sets, the UPGMA with D allocation methods produced core subsets with significantly more diversity than the other methods and were better than the M strategy for maximizing genetic distance. For most of the diversity indices, the M strategy outperformed the D method.