bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen and CO2 Affect Regrowth and Biomass Partitioning Differently in Forages of Three Functional Groups
Authors: Morgan Jack A. , Skinner R.Howard , Hanson Jon D.
Published: July 2010

Little work has been done to assess the impact of elevated CO2 on responses of forages to defoliation. This study examines regrowth, biomass partitioning, and labile C and N metabolites in three functional plant‐types: a C3 grass [Pascopyrum smithii (Rydb.) A. Love], a C4 grass [Bouteloua gracilis (H.B.K.) Lag.], and a forage legume (Medicago sativa L.). Plants were grown from seed, defoliated twice, and grown in a controlled environment under a factorial arrangement of two CO2 [low CO2 (LC), 355 μmol mol−1, and high CO2 (HC), 700 μmol mol−1] and two N nutrition regimes [low N (LN), watered twice weekly with half‐strength Hoagland's containing 0 N, and high N (HN), half‐strength Hoagland's containing 14 mM N]. High N enhanced regrowth in all three species, while high CO2 enhanced regrowth only in the two C3 species. In M. sativa, CO2 and N treatments had no significant effect on k, the allometric growth coefficient. In contrast, k was reduced in P. smithii plants grown under LN (0.63) compared with HN (0.99). In B. gracilis, low N also reduced k, but it interacted with CO2 so that k was greatest for plants grown at HN/HC (0.95) and HN/LC (0.89), intermediate at LN/LC (0.58), and least at LN/HC (0.44). These results indicate greater partitioning to below‐ground organs (reduced k) when N is limiting, particularly under elevated CO2 Significant correlations were established between k and several measures of plant N status, suggesting that the effects of CO2 on plant biomass partitioning involve N status.
Evaluating On‐Farm Flooding Impacts on Soybean
Authors: Sullivan Matthew , VanToai Tara , Fausey Norman , Beuerlein James , Parkinson Robert , Soboyejo Alfred
Published: July 2010

Flooding is a major problem that reduces soybean [Glycine max(L.) Merr.] growth and grain yield in many areas of the USA and the world. Our objective was to identify the plant and soil characteristics associated with different flooding durations in six fields in central Ohio. The soybean plants were at the V2 and V3 stages when rainfall‐induced flooding occurred. The outer perimeters of the flooded areas were mapped, using GPS (global positioning system) technology, several times during the flooding event to delineate the change of the flooded area over time. Two 9‐m wide transects across the flooded area within each field were divided into plots of 9 m by 9 m according to flooding duration: no flooding, 1 to 3 d, 4 to 6 d, and 6 to 8 d. Soil and plant nutrient levels, grain yield data and grain protein and oil content were determined for each plot. The soil cation‐exchange capacity (CEC), pH, P, Ca, Mn, and Zn concentrations had significant positive correlation with flooding duration. There was a significant negative correlation of flooding duration with the population, height, number of pods, and yield of soybean. There was no significant correlation of flooding duration with seed weight, oil, or protein content of the seeds. Leaf tissue Ca, Mg, B, Fe, Cu, and Al concentrations had a significant positive correlation with flooding duration, whereas leaf tissue N concentration had a significant negative correlation with flooding duration.
QTL Conditioning Physiological Resistance and Avoidance to White Mold in Dry Bean
Authors: Miklas Phillip N. , Johnson William C. , Delorme Richard , Gepts Paul
Published: July 2010

Physiological resistance is an important component of integrated strategies used to control white mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary], a major disease of common bean (Phaseolus vulgaris L.) in North America. Information pertaining to inheritance of physiological resistance, as detected by the greenhouse straw test, and its relationship with field resistance is lacking. The objectives of this study were to compare physiological resistance as detected by two separate straw tests with field resistance, evaluate heritability of physiological resistance, and to characterize the disease reaction of G 122 by quantitative trait locus (QTL) analysis. This was done in a recombinant inbred population (A 55/G 122) consisting of 67 F8‐derived lines. The greenhouse tests with five and six replications, respectively, and the field test with three replications were conducted in randomized complete block designs. Moderate heritability for disease reaction (scored from 1 = no symptoms to 9 = severe disease) was observed across the straw tests (0.65) and in the field (0.78). Inheritance of disease reaction was further investigated with a framework linkage map composed of 74 markers. Interval mapping detected a QTL on linkage group B7 near the phaseolin seed protein (Phs) locus that explained 38% of the phenotypic variation for disease score across the straw tests. The same B7 QTL (26%), and an additional QTL (18%) on B1 near the fin gene for determinate growth habit, conditioned field resistance. A QTL (34%) for canopy porosity, a measure of potential disease avoidance, also mapped to the fin locus. Results confirmed that physiological resistance as detected by the straw test was an integral component of field resistance, and that both physiological and avoidance mechanisms contributed to field resistance in the A 55/G 122 population. The landrace G 122 clearly provides breeders with a heritable source of physiological resistance to combat white mold disease.
Selection of Sugarcane Clones in Small Plots: Effects of Plot Size and Selection Criteria
Authors: Jackson Phillip , McRae T.A.
Published: July 2010

Sugarcane (Saccharum spp.) clones are frequently evaluated in one‐ or two‐row plots in the early stages of selection in sugarcane breeding programs. This study assessed the value of performance in small plots for predicting performance under near pure stands and compared different selection methods and criteria based on measurements made in small plots. Two populations of unselected seedling clones were evaluated in different plot sizes in experiments at two sites over two and three crop‐years, respectively. Commercially recoverable sugar content in cane (%), cane yield (kg/ha), sugar yield, and an estimate of relative economic value (REV, $) were determined in each plot. Cane yield was biased by competition effects in the small plots, but this was not the case for sugar content. Genetic correlations between cane yield in one‐row plots and the middle two rows of the six‐row plots in the same experiment and year averaged 0.49, while the equivalent correlation involving sugar content was 0.91. Measurements of sugar yield and REV were also biased in small plots because of the influence of cane yield. Measurements in small plots were considered in terms of indirect selection criteria for improving REV in large plots (the latter representing REV in pure stands). Selection based on sugar content alone in small plots gave equal or larger gains compared with other selection criteria, including REV itself in small plots. It is suggested that selection in small plots in early stages of selection in sugarcane breeding programs should be based largely on sugar content. Measuring cane yield in such trials may be inefficient and where destructive measurement via mechanical harvesting is involved, may unnecessarily delay progression of selected clones through to the next stages of selection.
Drought and Heat Stress Injury to Two Cool‐Season Turfgrasses in Relation to Antioxidant Metabolism and Lipid Peroxidation
Authors: Jiang Yiwei , Huang Bingru
Published: July 2010

Drought and high temperature are two major factors limiting the growth of cool‐season turfgrasses during summer in many areas. The objective of the study was to examine whether the adverse effects of drought and heat alone or in combination on tall fescue (Festuca arundinacea L.) and Kentucky bluegrass (Poa pratensis L.) involve oxidative stress. Grasses were exposed to drought (withholding irrigation), heat (35°C/30°C), and the combined stresses for 30 d in growth chambers. Turf quality (TQ), leaf relative water content (RWC), and chlorophyll content (Chl) decreased with prolonged drought, heat, and combined stresses for both species, but the severity of decline varied with stress type and duration. Transient increases in superoxide dismutase (SOD), ascorbate peroxidase (AP), and glutathione reductase (GR) activities occurred at 6 or 12 d of drought and the combined stresses in both species; however, the activities of all three enzymes decreased with extended periods of drought and the combined stresses. The SOD activity was not affected by heat stress alone. The activities of AP and GR were reduced after 18 d of heat stress for both species, but reductions were less than under the combined stresses. The catalase (CAT) activity continued to decrease to below the control level, beginning at 12 d for drought‐stressed or heat‐stressed plants and 6 d for plants exposed to the combined stresses. Lipid peroxidation occurred after 18 d of stresses in both species, as indicated by the increase in malondialdehyde (MDA) content. The results suggested that injuries of drought, heat, or the combined stresses to both tall fescue and Kentucky bluegrass, as manifested by declines in TQ, RWC, and Chl, could be associated with a decrease in antioxidant enzyme activities and an increase in membrane lipid peroxidation.
Dry Matter Production of Orchardgrass and Perennial Ryegrass at Five Irrigation Levels
Authors: Jensen Kevin B. , Asay Kay H. , Waldron Blair L.
Published: July 2010

Within the Great Basin, availability of irrigation water throughout the growing season is the limiting factor in the development of improved pastures. The choice of species and their water requirements are critical factors for providing a stable source of forage throughout the grazing season. A line‐source irrigation system was used from 1995 to 1998 to evaluate dry matter (DM) production and seasonal forage distribution of nine orchardgrass (Dactylis glomerata L.) and perennial ryegrass (Lolium perenne L.) hybrid cultivars along with check cultivars of meadow brome (Bromus riparius Rehm.) and smooth brome (B. inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), and quackgrass [Elytrigia repens (L.) Nevski] × bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Love] hybrids (RS) under five irrigation levels ranging from 41 to 91 cm per year. Mean DM production rankings across water levels combined over years were tall fescue > orchardgrass > meadow brome > RS‐hybrid > smooth brome > perennial ryegrass‐hybrids. The DM production response across water levels was largely linear with a minor but significant quadratic component at lower water rates. Tall fescue was most responsive (i.e., produced more DM production) to increased irrigation rates. At lower water levels, meadow brome outyielded orchardgrass. However, when water was not limited, orchardgrass outyielded meadow brome. The RS hybrid and smooth brome had relatively low DM production at both low and high water levels. All species produced significantly (P < 0.01) more DM than perennial ryegrass at lower water levels. Under limited irrigation, tall fescue and meadow brome will produce more DM.
Molecular Markers Linked to Brown Stem Rot Resistance Genes, Rbs1 and Rbs2, in Soybean
Authors: Bachman M.S. , Tamulonis J.P. , Nickell C.D. , Bent A.F.
Published: July 2010

Brown stem rot (BSR) of soybean [Glycine max (L.) Merr.] is caused by the fungal pathogen Phialophora gregata (Allington & D.W. Chamberlain) W. Gams and occurs in soybean production areas around the world. Brown stem rot resistance genes Rbs1, Rbs2, and Rbs3 have been identified in soybean germplasm and plant introductions through traditional genetic analyses. Resistance to BSR has been shown to reduce yield losses in soybean, but selection for this trait is laborious and confounded by environmental variation. The objectives of this study were to identify molecular markers linked to BSR resistance genes Rbs1 and Rbs2, and map these genes in the soybean genome. Genetic families of populations segregating for Rbs1 and Rbs2 were evaluated in the greenhouse for BSR phenotypic reaction and identified as resistant, segregating, or susceptible. Leaf tissue collected from members of F2:3 families was bulked and DNA simple sequence repeat (SSR) marker analysis was used to identify markers that cosegregated with BSR reaction phenotypes. Five pairs of Rbs2 near‐isogenic lines were subjected to a similar analysis to verify results obtained from marker analysis conducted on the population segregating for Rbs2 Results of marker analyses indicated that SSR markers Satt215 and Satt431 were linked to Rbs1 and that Satt244 and Satt431 were linked to Rbs2 Marker‐assisted selection in the Rbs1 (using Satt431) and Rbs2 (using Satt244) populations would have correctly predicted 88 and 82%, respectively, of the BSR reaction phenotypes. The Rbs1 and Rbs2 loci map to Molecular Linkage Group J and lie in a region known to contain Rbs3 This region also contains loci conditioning resistance to taxonomically diverse fungal pathogens and a locus affecting nodulation in response to a bacterial symbiont.
QTL Analysis of Resistance to Fusarium Root Rot in Bean
Authors: Schneider Kristin A. , Grafton Kenneth F. , Kelly James D.
Published: July 2010

A major constraint to dry edible and snap bean (Phaseolus vulgaris L.) production worldwide is root rot, one form of which is caused by Fusarium solani f. sp. phaseoli (Burk.) Snyd. & Hans (FSP). Sources of resistance to this pathogen exist in P. vulgaris, and, in the current paper, we studied the inheritance of one such source, FR266, using two recombinant inbred populations, MF and IF, derived from crosses of susceptible cultivars Montcalm (M) and Isles (I) with FR266 (F). Random amplified polymorphic DNA (RAPD) markers, associated with quantitative trait loci (QTL) controlling resistance to Fusarium root rot, also were identified. Genetic resistance to FSP, originally derived from PI 203958, was polygenically controlled and strongly influenced by environmental factors. Heritability estimates (h2) were moderate and ranged from 0.48 to 0.71 for MF population. Several RAPD markers were identified that demonstrated significant associations with resistance to FSP determined from both greenhouse and field evaluations. Markers associated with field ratings tended not to be associated with greenhouse ratings and vice versa, except for the P700 marker which was significantly associated with both greenhouse and field data. Individual markers identified in this study did not explain more than 15% of the phenotypic variation for root rot resistance, whereas a combination of four markers explained 29% of the phenotypic variation for root rot ratings in the field. The two regions of the bean genome associated with root rot resistance corresponded to loci controlling the Pv pathogenesis‐related proteins (PvPR). Mechanisms associated with host defense responses may be involved in resistance to FSP and selection directed towards enhancing these traits may allow for rapid improvement of resistance to Fusarium root rot in bean.
Resistance to Frogeye Leaf Spot in Maturity Groups VI and VII of Soybean Germplasm
Authors: Yang Wencai , Weaver David B.
Published: July 2010

Frogeye leaf spot (FLS) (caused by Cercospora sojina Hara) is an important foliar disease in many soybean [Glycine max (L.) Merr.] production areas of the world. It can cause severe yield losses, but can be completely managed with genetic resistance. Three dominant genes for resistance have been reported. However, the fungus is known to be genetically variable, and in the past, new races have developed that were capable of infecting previously resistant genotypes. Finding additional sources of resistance may reduce the impact of new virulent races. The objective of this study was to evaluate all available soybean plant introductions in maturity groups VI and VII for resistance to FLS. Plants were inoculated with C‐32, an isolate of C. sojina, in the greenhouse. Genotypes were rated on a scale of 0 to 6 on the basis of percent leaf area infected with lesions. Six hundred sixty (39.3%) of the accessions received a rating of 3 or lower, and were identified as resistant. Twelve accessions remained completely disease free after repeated inoculation, thus were considered highly resistant or immune. There appears to be adequate resistance to FLS within the germplasm collection, and many of these may have unique resistance genes.
Vitamin e concentration in upland cotton seeds
Authors: Smith C.Wayne , Creelman Robert A.
Published: July 2010

Vitamin E, tocopherol, is a naturally occurring antioxidant that has been implicated in human health issues such as decreased risk of cardiovascular disease and some forms of cancer, improved immune functions, and in slowing the progress of degenerative diseases. Tocopherol affects plant health much as it does human health, i.e., by scavenging free radicals, thus protecting plant membrane integrity. Tocopherol is a strong antioxidant and increases oil oxidative stability in cottonseed oil. Little is known about the tocopherol content of cotton (Gossypium hirsutum L.) seed. ‘Acala 1517‐88’ and ‘Acala 1517‐SR2’ are reportedly higher in α‐tocopherol than ‘Deltapine 50’ or ‘Stoneville 825.’ Objectives of this research were to determine the variability in vitamin E content among several current upland cotton genotypes grown during 1997 and 1998 at College Station, TX, and when grown at College Station and Chillicothe, TX, in 1997. Tocopherol was extracted from cotton seeds with hexane and levels were determined by HPLC. Years were significant for α‐ and δ‐tocopherol and location was significant for β/γ‐tocopherol. However, no differences were detected among 18 genotypes grown during 1997 and 1998 at College Station nor among 13 genotypes grown at College Station and Chillicothe during 1997.
Host Plant Resistance Genes for Fusarium Head Blight: Sources, Mechanisms, and Utility in Conventional Breeding Systems
Authors: Rudd J.C. , Horsley R.D. , McKendry A.L. , Elias E.M.
Published: July 2010

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)], also known as scab, is a destructive disease of wheat (Triticum aestivum L; T. turgidum L. var durum) and barley (Hordeum vulgare L.). Host resistance has long been considered the most practical and effective means of control, but breeding has been hindered by a lack of effective resistance genes and by the complexity of the resistance in identified sources. This paper will provide an overview of progress in developing host plant resistance for FHB, primarily in the USA, by review of the sources of resistance in wheat and barley, and their utilization in breeding programs. Although there are no reported sources of immunity, considerable genetic variability exists for resistance in both wheat and barley. Sources of resistance in durum, however, are limited. The strategy of breeding programs is to recombine different types and sources of resistance steadily through traditional breeding strategies. To facilitate selection, artificial inoculation techniques are used in both the field and greenhouse. This enables breeders to select simultaneously for resistance and desirable agronomic characteristics. Incremental increases in resistance are being reported in hexaploid wheat and to a lesser extent in barley and durum wheat. It is anticipated that the development of molecular markers will improve the efficiency of developing FHB wheat and barley cultivars.
Two Types of GGE Biplots for Analyzing Multi‐Environment Trial Data
Authors: Yan Weikai , Cornelius Paul L. , Crossa Jose , Hunt L.A.
Published: July 2010

SA genotype main effect plus genotype × environment interaction (GGE) biplot graphically displays the genotypic main effect (G) and the genotype × environment interaction (GE) of the multienvironment trial (MET) data and facilitates visual evaluation of both the genotypes and the environments. This paper compares the merits of two types of GGE biplots in MET data analysis. The first type is constructed by the least squares solution of the sites regression model (SREG2), with the first two principal components as the primary and secondary effects, respectively. The second type is constructed by Man‐del's solution for sites regression as the primary effect and the first principal component extracted from the regression residual as the secondary effect (SREGM+1). Results indicate that both the SREG2 biplot and the SREGM+1 biplot are equally effective in displaying the “which‐won‐where” pattern of the MET data, although the SREG2 biplot explains slightly more GGE variation. The SREGM+1 biplot is more desirable, however, in that it always explicitly indicates the average yield and stability of the genotypes and the discriminating ability and representativeness of the test environments.
Stability of Carbon Isotope Discrimination and Grain Yield in Durum Wheat
Authors: Merah O. , Deléens E. , Souyris I. , Nachit M. , Monneveux P.
Published: July 2010

Carbon isotope discrimination (Δ) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in bread wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), with potential value for durum wheat (Triticum turgidum convar. durum Desf. MacKey). We evaluated the genetic variation for Δ, the relationship between Δ and grain yield, and the magnitude of genotype × year (G × Y) interactions in durum wheat. Field experiments were conducted under Mediterranean conditions on 144 durum wheat accessions during three successive years. Grain yield and carbon isotope discrimination of flag leaves (ΔF) and kernels (ΔK) were measured. Large genotypic and year variation was observed for ΔF and ΔK. Flag leaf Δ was correlated with grain yield in 2 yr characterized as having greater water limitation (r = 0.29 − 0.38, P < 0.001). Conversely, ΔK and grain yield were significantly correlated in all 3 yr (r = 0.49 − 0.52, P < 0.001). In addition, G × Y interactions were significant for ΔF, ΔK and grain yield. However, significant correlations (P < 0.001) were noted for ΔK across years. As a result, ΔK may serve as a better predictive criterion for higher grain yield under Mediterranean conditions.
Genetic Analysis and QTL Mapping of Cell Wall Digestibility and Lignification in Silage Maize
Authors: Méchin Valérie , Argillier Odile , Hébert Yannick , Guingo Emmanuelle , Moreau Laurence , Charcosset Alain , Barrière Yves
Published: July 2010

Improving digestibility is a major goal for forage maize (Zea maysL.) breeding programs. Quantitative trait loci (QTL) affecting forage maize digestibility‐related and agronomic traits were mapped and characterized in a set of recombinant inbred lines (RIL). Eleven traits were analyzed on whole plant samples: neutral detergent fiber (NDF), starch content (STC), crude protein content (CPC), acid detergent lignin (ADL), in vitro dry matter digestibility (IVDMD), in vitro cell wall digestibility (IVNDFD), in vitro digestibility of non‐starch and non‐soluble carbohydrate (IVDNSC), dry matter content (DMC), dry matter yield (DMY), mid‐silk date (SILK), and plant height (PHT). Evaluation was performed among the RIL populations studied per se (RILps) and in combination with a tester (TC). The genetic variances (σ2g) were highly significant and, in most cases, greater than genotype × year interaction variances (σ2g×y). Heritabilities ranged from 0.49 to 0.70 in RILps and from 0.12 to 0.58 in TC. Twenty‐eight QTL were identified among TC by CIM, which explained individually between 3.3 and 20.2% of the phenotypic variation (R2p) for traits related to digestibility or agronomic performance. Twenty QTL were identified among RILps, which explained individually between 6.5 and 15.3% of the phenotypic variation (R2p). Seven of these QTL were common to TC and RILps. Cell wall digestibility estimates (IVNDFD or IVDNSC) were the traits with the highest number of QTL. In contrast, we detected only one QTL for dry matter digestibility (IVDMD). Thus, it may be useful to separate IVDMD into its two component parts, cell wall digestibility, which could be estimated from line per se values, and starch content. Characteristics such as IVDNSC or IVNDFD, coupled with QTL information, would be powerful tools in the search for genes involved in maize lignification or cell wall biogenesis.
A New Soybean Maturity and Photoperiod‐Sensitivity Locus Linked to E1 and T
Authors: Cober Elroy R. , Voldeng Harvey D.
Published: July 2010

An association between early maturity and tawny pubescence has been observed in short‐season soybean [Glycine max (L.) Merr.]. The objectives of this study were to determine if a single locus controls early maturity; and if there is a new locus linked to E1 and T or, alternatively, a third allele at the E1 locus. A cross was made between ‘Harosoy’ isolines OT89‐5 (e3e3 e4e4) and OT94‐47. PI 196529 was the donor of early maturity in the backcrossing program which developed OT94‐47. A total of 229 F2 plants and the parents were grown under 20‐h photoperiods produced by incandescent lamps. OT94‐47 flowered in 43 ± 1.4 d, OT89‐5 flowered later in 57 ± 4.2 d, and the F2 population fit a 3 late: 1 early flowering ratio. Early‐flowering F2 plants produced F3 families that flowered similarly to OT94‐47. Later‐flowering F2 plants either segregated for flowering date or flowered similarly to OT89‐5. To test for allelism with E1 and linkage with T, a cross was made between OT93‐26 (E1E1 e3e3 e4e4 TT) and OT94‐47. F2 plants were classified as parental types or intermediate and equivalent to OT89‐5 in maturity. Maturity and pubescence color were recorded in 376 F3 progeny rows. The data did not fit a single locus model or a two loci dominant epistasis model (12:3:1). The E7 allele was partially, but not completely, dominant over the e7 allele. Therefore, a new locus E7 is proposed. Using the F3 segregation data, linkage between T and E1 was estimated to be 1.3 ± 0.6 centimorgan (cM). Linkage between E1 and E7 was estimated to be 6.2 cM and linkage between E7 and T was estimated to be 3.9 cM. E7 is a new flowering, maturity, and photoperiod sensitivity locus tightly linked to both E1 and T E7E7 results in later flowering and maturity, and sensitivity to long photoperiods produced by incandescent lamps when compared to e7e7
Seed Number as a Function of Growth. A Comparative Study in Soybean, Sunflower, and Maize
Authors: Vega Claudia R.C. , Andrade Fernando H. , Sadras Víctor O. , Uhart Sergio A. , Valentinuz Oscar R.
Published: July 2010

Seed number, the main yield component of cereals and oil‐seed species, strongly depends on the physiological status of the crop during a critical period for seed set. Using a comparative approach including three species with contrasting reproductive strategies, we investigated the relationship between seed number per plant (SNP) and plant growth rate during the critical period for seed set (PGRC). Indeterminate soybean [Glycine max (L.) Merr.], sunflower (Helianthus annuus L.), and maize (Zea mays L.) crops were grown under a wide range of plant densities to generate contrasting availability of resources per plant. Growth of individual plants was estimated by a novel, nondestructive method based on relationships between actual shoot dry matter and morphometric variables, including stem diameter, plant height, and dimensions of reproductive structures. Seed number per plant ranged from 0 to 890 in soybean, 0 to 4096 in sunflower, and 0 to 1348 in maize and PGRC (g d−1) from 0.01 to 4.3 in soybean, 0.3 to 17.6 in sunflower, and 0.4 to 12.3 in maize. Our study showed that (i) the relationship between SNP and PGRC was linear in soybean, reflecting the reproductive plasticity of this species, and curvilinear in sunflower and maize, reflecting morphogenetic restrictions to generate reproductive sinks under favorable growing conditions; (ii) the PGRC threshold below which no seed was set varied among species, being negligible in soybean, close to 0.35 g d−1 in sunflower, and 1 g d−1 in maize. Quantitative relationships between seed number and plant growth rate during the critical period of seed set could be useful for crop modeling.
Genetic Mapping and Analysis of Quantitative Trait Loci for Resistance to Stalk Tunneling by the European Corn Borer in Maize
Authors: Cardinal Andrea J. , Lee Michael , Sharopova Natalya , Woodman‐Clikeman Wendy L. , Long Mary J.
Published: July 2010

The European corn borer (ECB), Ostrinia nubilalis (Hübner), is an important pest of temperate maize (Zea mays L.). Damage to the stalk could be minimized by breeding for resistant genotypes but selection is hindered by a laborious phenotypic assay. Knowledge of the position of quantitative trait loci (QTL) conferring resistance to ECB tunneling could greatly simplify selection for this trait. This study was conducted to map QTL for resistance to ECB tunneling, plant height, and anthesis. Recombinant inbred lines of the maize single‐cross population B73×B52, were grown at two locations in Iowa in 1997 and 1998. Genotypic and phenotypic data were obtained from each line to perform the QTL analysis. Nine QTL were detected for ECB tunneling, and they were associated with 59% of the genetic variation. Genetic effects for decreased tunneling were derived from the resistant parent, B52, at six QTL. One digenic interaction was detected between QTL for ECB tunneling. Eight and 10 QTL were detected for anthesis and plant height, respectively. ECB tunneling was not significantly correlated with either trait. Several QTL for ECB tunneling reported herein, QTL for ECB tunneling in other maize populations, and QTL for resistance to leaf damage by insect pests of tropical maize are located at similar positions of the maize genetic map.
Defining a Multiple‐Use Germplasm Collection for the GenusTrifolium
Authors: Morris J.B. , Greene S.L.
Published: July 2010

An effective germplasm collection provides genetic variation useful to crop improvement, botanical research, and conservation of plant biodiversity. The USDA NationalTrifoliumgermplasm collection currently limits the collection's effectiveness in serving multiple uses. Reflecting the historic mandate of plant introduction, the collection is strongly biased toward the two major cultivated red and white clover species, which make up 56% of the collection. Although many wild species are present in the collection, representation is poor for species that are considered gene sources for the cultivated species and for species that have minor use. The objectives of this article are to demonstrate how the collection can be diversified to better serve users and contribute to the conservation of the genus. Reflecting priorities proposed in the 1970s, the scope was defined as containing all species within the genusTrifoliumNext, a broad gene‐pool model was defined on the basis of ease for interspecific hybridization and the history of crop use. Areas in the model were then identified that required more accessions to represent diversity of specific interest to users or that were vulnerable to erosion or extinction. An essential step before making any changes to the collection is to establish priorities by the crop curators and members of the Crop Germplasm Committee (CGC). If a diverse set of collection stakeholders can be included in the process, changes are more likely to result in a germplasm collection that serves diverse users and makes a significant contribution to conserving plant biodiversity.
Selection for Persistence in Endophyte‐Free Kentucky 31 Tall Fescue
Authors: Bouton J. H. , Gates R. N. , Hoveland C. S.
Published: July 2010

‘Kentucky 31’, released in 1943, remains the most widely used tall fescue cultivar (Festuca arundinaceaSchreb.). The fungal endophyte,Neotyphodium coenophialum(Morgan‐Jones & Gams.) Glenn, Bacon & Hanlin comb. nov., which naturally infects Kentucky 31, enhances survival and competitiveness of the grass. However, cattle grazing forage from endophyte‐infected (E+) Kentucky 31 suffer from fescue toxicity because of alkaloids in the forage. A possible strategy to reduce fescue toxicity is cultivar improvement to develop more persistent endophyte‐free (E−) cultivars. The objective of our research was to assess the results of selection with different levels of stress (grazing and competition with bermudagrass,Cynodon dactylonL.) to increase persistence and competitiveness within E− Kentucky 31. Populations were selected in the following environments: (i) seeded into bermudagrass and grazed with continuously stocked beef cattle, (ii) seeded into bermudagrass and clipped intermittently with a mower, (iii) seeded into tilled soil and grazed with continuously stocked beef cattle, and (iv) seeded into tilled soil and clipped intermittently with a mower. Populations were developed from the best surviving plants in each selection condition and tested for grazing persistence and competitiveness with bermudagrass. Grazing, especially when combined with bermudagrass competition, created the greatest reduction of persistence. No selected population was found to survive better than E− Kentucky 31 even when tested in the same conditions used during its selection. The E+ checks were the most persistent entries in all testing conditions. These experiments indicate that selection within E− Kentucky 31 for improved persistence will be difficult and may need to be explored on other E− tall fescue germplasm sources, but another strategy may be reinfection with non‐toxic endophyte strains.
Diallel Analysis for Tocopherol Contents in Seeds of Rapeseed
Authors: Goffman Fernando D. , Becker Heiko C.
Published: July 2010

Because of their nutritional and antioxidative properties, tocopherol production is an interesting trait for the lipid quality of oil crops. Total tocopherol content in rapeseed (Brassica napus L.) is medium to low, and therefore, higher levels of tocopherol are desirable in this species. The objective of the present study was to determine the inheritance of α‐, γ‐, and total tocopherol content and the α‐/γ‐tocopherol ratio in seed of rapeseed. Two diallel mating designs with six parents each were used. In Diallel I, the parents selected were high or low for total tocopherol content and in Diallel II, the parents were high or low for the α‐/γ‐tocopherol ratio. Parents and F1 hybrids were tested in a screenhouse in 1998 and under field conditions in 1999 by means of a completely randomized design with two replications. In addition, 10 selected F2 populations were grown along with their respective parents. Compared with the parents, the F1 hybrids showed a significantly higher γ‐tocopherol content of about 6 mg kg−1 seed for Diallel I and 24 mg kg−1 seed for Diallel II. General combining ability effects in both diallels were highly significant (P < 0.01) and much larger than specific combining ability effects for all traits studied. Reciprocal effects were not statistically significant. γ‐Tocopherol was not correlated with α‐tocopherol. The results indicate that tocopherol content and composition inheritances are strongly associated with additive gene action in rapeseed.
Environmental Effects on Cotton Fiber Carbohydrate Concentration and Quality
Authors: Pettigrew W. T.
Published: July 2010

Cotton (Gossypium hirsutum L.) grown in reduced light environments produces inferior fiber compared with that produced in abundant sunlight environments. This response to low light suggests that insufficient photosynthetic assimilates are the cause of the fiber quality reductions. The primary objective of this research was to determine how fiber carbohydrates respond to varying levels of sunlight during development. A field study was conducted from 1995 to 1997 in which cotton was exposed to two light regimes during reproductive growth: (i) incident sunlight and (ii) 70% of incident sunlight achieved with shade cloth. Samples of fiber, ovules, and leaves subtending the boll were collected at 0, 14, 21, and 35 d post anthesis (DPA) and analyzed for starch, glucose, fructose, and sucrose. Fiber quality was determined at the end of the season. With some exceptions, the shade treatment reduced carbohydrates levels in the leaf and ovule tissue. At 14 DPA, starch was reduced 29% in fiber grown under shade. Sucrose levels in shade fiber was reduced 31% at 21 DPA. The carbohydrate reductions at 14 and 21 DPA occurred during a period of fiber development when strength is determined. These carbohydrate reductions parallel the 3% fiber strength reductions seen with low light. The reduced sucrose levels at 21 DPA induced by the shade also occur during fiber secondary cell wall deposition and match the lower fiber micronaire produced under shade. These data present compelling evidence that adequate carbon assimilates are required to produce fiber quality approaching genetic maximums.
Cotton Growth and Development under Different Tillage Systems
Authors: Kennedy Charles W. , Hutchinson Robert L.
Published: July 2010

Adoption of reduced tillage systems is a means to lower production costs and improve soil productivity, but yield of cotton (Gossypium hirsutum L.) can be variable. Our objective was to determine when and how different tillage systems affected growth quantities and yield. The effect of conventional tillage (CT), ridge tillage (RT), and no tillage (NT) on crop growth rate (CGR), leaf area index (LAI), net assimilation rate (NAR), fruiting form numbers and weights, plant population, and crop yield was determined on a Gigger silt loam (fine‐silty, mixed, thermic, Typic Fragiudalf). In 1991, the NT system produced a maximum prebloom CGR of 11 g m−2 d−1 compared with 7 and 7.5 g m−2 d−1 for the CT and RT systems, respectively. In 1992, a year with more adverse growing conditions, prebloom CGR values were lower for all systems but NT was greatest at 7 g m−2 d−1 Differences in prebloom CGR among tillage systems in 1994 were similar to the1992 results although values were similar to those of 1991. Prior to blooming, the RT system produced a consistently lower CGR than one or both of the other systems. Differences in LAI corresponded to CGR differences, but there were no differences among the three tillage systems in NAR. Greater early CGR led to faster ontogenic development and eventually to greater lint yields. Lint yields averaged 1057 kg ha−1 for NT, 1007 kg ha−1 for CT, and 890 kg ha−1 for RT. The NT system, which in this study had the greatest prebloom CGR and lint yield, was the conservation tillage system with the greatest production potential in this soil type. Early‐season differences in soil characteristics among tillage systems at 0 to 0.15 m was considered a factor.
Comparative DNA Profiling of U‐3 Turf Bermudagrass Strains
Authors: Anderson M. P. , Taliaferro C. M. , Martin D. L. , Anderson C. S.
Published: July 2010

Long‐term maintenance of genetic fidelity of clonally propagated bermudagrass (Cynodon spp.) cultivars is difficult. Contamination may arise through mechanical mixtures, the presence of viable seed, and somatic mutations. DNA amplification fingerprinting (DAF) was used to compare genetically putative ‘U‐3’ bermudagrass [Cynodon dactylon (L). Pers.] selected in the early 1930s with bermudagrass currently produced in Oklahoma and sold as U‐3. Four samples of putative U‐3 and seven samples of Oklahoma U‐3 were tested. Foundation class ‘Tifway’ (C. dactylon × C. transvaalensis Burtt‐Davy), along with two other commercially labeled Tifway strains, were included as reference standards to gauge genetic diversity. Six DAF primers were used to differentiate the 14 bermudagrass strains used in this study. The DAF analysis of all bermudagrass strains produced an average of 56.0 ± 5.9 SE polymorphic bands/primer. Comparisons among the putative and Oklahoma grown U‐3 strains resulted in 37.1 ± 5.1 SE polymorphic bands/primer. Phenetic analyses using both the UPGMA algorithm and principal coordinate analysis revealed a wide separation between the putative U‐3 and the Oklahoma strains identified as U‐3. Putative U‐3 samples collected from three mid‐Atlantic golf courses clustered tightly as did all U‐3 strains from Oklahoma. A putative U‐3 strain from Illinois clustered with putative U‐3 from the mid‐Atlantic golf courses, but was distinct. The Oklahoma U‐3 strains were equally distant from Foundation class Tifway as they were from putative U‐3. The Oklahoma U‐3 collections appear genetically identical and likely resulted from mechanical contamination of a true U‐3 nursery plot that served as a source of planting stock for sod growers.
Identification of a QTL Associated with Tolerance of Soybean to Soil Waterlogging
Authors: VanToai Tara T. , St. Martin Steven K. , Chase Kevin , Boru Getachew , Schnipke Virginia , Schmitthenner A. Fred , Lark Karl G.
Published: July 2010

Soil waterlogging is a major environmental stress that suppresses soybean [Glycine max(L.) Merr.] growth and yield. Our objective was to identify quantitative trait loci (QTL) associated with the tolerance of soybean to soil waterlogging. We subjected 208 lines of two recombinant inbred (RI) populations, ‘Archer’ × ‘Minsoy’ and ‘Archer’ × ‘Noir I’, to 2 wk of waterlogging when the plants were at the early flowering stage. The control plants were not flooded. The experiment was conducted in three environments: Columbus, OH, in 1997 and 1998 and Wooster, OH, in 1998. We identified a single QTL, linked to marker Sat_064, from the Archer parent which was associated with improved plant growth (from 11–18%) and grain yields (from 47–180%) in waterlogged environments. This highly significant QTL (P= 0.02–0.000001) was identified in both RI populations and at both Columbus 1997 and 1998 environments, but not at the Wooster 1998 environment. The differences in soil type and flooding treatment (stagnant versus moving water) could have contributed to the lack of QTL identification at the Wooster 1998 environment. The Sat_064 QTL was uniquely associated with waterlogging tolerance and was not associated with maturity, normal plant height or grain yields. The Sat_064 marker maps close to theRps4 gene for Phytophthora (Phytophthora sojaeM.J. Kaufmann & J.W. Gerdemann) resistance; however, since Archer does not contain theRps4 resistance allele, it is probably not a disease tolerance QTL. Near isogenic lines with and without the Sat_064 marker have been developed and are being field tested under waterlogging conditions to confirm the association of the QTL with the tolerance of soybean to waterlogging stress.
Quantitative Trait Loci Associated with Milling and Baking Quality in a Soft × Hard Wheat Cross
Authors: Campbell Kimberly Garland , Finney Patrick L. , Bergman Christine J. , Gualberto Daisy G. , Anderson James A. , Giroux Michael J. , Siritunga Dimuth , Zhu Jiaqian , Gendre Francois , Roué Catherine , Vérel Aliette , Sorrells Mark E.
Published: July 2010

Interclass hybridization between soft and hard wheat (Triticum aestivum L.) results in new genetic combinations of potential value. We investigated whether interclass hybridization could improve end‐use quality of both classes. Our objectives were to analyze quality traits in a population of recombinant inbred lines (RILs) derived from a cross between the good quality soft white wheat NY6432‐18 (NY18), and good quality hard white wheat Clark's Cream (CC), identify quantitative trait loci (QTLs) for those traits, and use linkage analysis to determine which parent was contributing favorable alleles at specific QTLs for a given trait. The population was assessed for milling, protein and dough mixing, hydration, cookie and loaf traits. Traits were measured in two to six environments grown over three seasons in Ithaca, NY. The molecular map for the population contains 370 molecular markers including restiction fragment length polymorphisms (RFLPs), microsatellites, and markers derived from known function genes in wheat. Linkage groups have been located to all the wheat chromosomes except for 7D. Pinb derived from the puroindoline b gene on chromosome 5DS was the major QTL for milling, hydration, and cookie baking traits. The major QTL for mixograph peak time was at the Glu‐Dy1 marker, derived from Glu‐D1‐2 gene on chromosome 1DL. The Glu‐Ax1 and Glu‐By1 markers were QTLs for mixograph peak height and tolerance, respectively. QTLs for flour protein quantity were detected on chromosome 2B. With the exception of the hydration traits, multiple regression models included alleles from both parents. Interclass hybridization may be an underexploited wheat breeding strategy for improvement of agronomic and quality traits in wheat.
Drought and Heat Responses in the Wild Wheat Relative Aegilops geniculata Roth: Potential Interest for Wheat Improvement
Authors: Zaharieva M. , Gaulin E. , Havaux M. , Acevedo E. , Monneveux P.
Published: July 2010

Wild wheat (Triticum aestivum L.) relatives could represent a valuable source of genetic variation for improvement of abiotic stress tolerance in cultivated wheat. A better knowledge of the adaptive strategies developed by these species is needed. A collection of 157 Aegilops geniculata accessions originating from different ecogeographical regions was studied during two successive years for several traits related to water status, chlorophyll content, and plant thermal regulation under Mediterranean field conditions. Close association was found between the studied traits and the origin of accessions. Two adaptive strategies were distinguished. Accessions originating from harsh environments had low biomass, low grain production and high water‐use efficiency (low C isotope discrimination). They were early, with small, thick leaves exhibiting low chlorophyll content, high surface temperature and low epidermal transpiration. We suggest that in these accessions, decreased leaf chlorophyll content could limit the energy load from strong sunlight. In accessions originating from regions with a mild Mediterranean climate, thermal regulation of the leaf may rather depend on transpiration, as suggested by high C isotope discrimination values. These accessions also were characterized by high chlorophyll content, leaf area, and biomass production. Associations between the physiological traits observed could help to better understand the relationship between abiotic stress tolerance and yield in cultivated wheats. Results obtained confirmed the potential value of Aegilops geniculata for improvement of high temperature and drought stress tolerance in wheat and could contribute to the choice of traits to be introgressed and the accessions to be used in wide hybridization programs.
Assessment of Plant Pathogenicity of Endophytic Beauveria bassiana in Bt Transgenic and Non‐Transgenic Corn
Authors: Lewis Leslie C. , Bruck Denny J. , Gunnarson Robert D. , Bidne Keith G.
Published: July 2010

Field and greenhouse studies were conducted to determine the proclivity of Bacillus thuringiensis (Bt) (Berliner)‐transgenic corn (Zea mays L.) to form an endophytic relationship with Beauveria bassiana, and to evaluate the corn for possible plant pathological effects associated with this relationship. Beauveria bassiana (Balsamo) Vuillemin was applied as a granular formulation to two separate lines of corn, expressing Bt events MON802 and MON810, and their corresponding isolines. There were no significant differences in levels of endophytism between transgenic events or their near‐isolines. In greenhouse studies, B. bassiana was applied as a liquid seed treatment to Bt transgenic corn hybrids Pioneer 34R06 (event MON810) and Ciba Max 454 (event 176) and their near isolines at a rate of 2 × 1010 conidia per ml. There were no significant differences in seed germination or presence of root pathogens in transgenic or isoline seeds soaked in a B. bassiana suspension. The same lines of corn were used in field experiments with treatments of seeds soaked in a suspension of B. bassiana, a foliar application of a granular formulation of B. bassiana, and corresponding untreated checks. Plants were sampled throughout the growing season and evaluated for growth of individual plant components, including sheaths, leaves, stem, husk, ear, plant leaf‐to‐stem ratio and overall plant growth. There were no significant differences in overall plant growth between the B. bassiana treatments or in the growth of each plant component. The results of this study indicate that B. bassiana readily forms an endophytic relationship with transgenic and non‐transgenic corn and causes no plant pathology.