bluuebunny/crossref_metadata_2025 huggingface dataset:
DOES BLOCKING AFFECT EXPERIMENTAL EFFICIENCY ON SAND‐BASED PUTTING GREENS?
Authors: Karcher Douglas E. , Goss Ryan M. , Richardson Michael D. , Gaussoin Roch E. , Secks Margaret E.
Published: July 2010

Past experiments on sand‐based putting greens have frequently used randomized complete blocked designs (RCBD), even though these experimental areas are relatively uniform with regard to external variables. Consequently, completely randomized designs (CRD) may have had better precision with which to estimate treatment effects compared with RCBD. The objective of this study was to estimate the relative efficiency (ERE) of a RCBD compared with a CRD when evaluating common parameters on sand‐based putting greens. Uniformity trials were conducted in Arkansas and Nebraska on sand‐based putting greens established with creeping bentgrass (Agrostis palustris Huds.). Estimated relative efficiency values were calculated for varying blocking schemes when measuring canopy temperature, soil temperature, soil moisture, clipping yield, and macronutrient content in plant tissues. Since canopy temperatures were time dependent, when those measurements were collected by a blocking scheme, the associated RCBD was approximately nine times more efficient than a CRD. For the remaining parameter and blocking scheme combinations, ERE values indicated that the precision between RCBD and CRD was similar. Therefore, it is likely that the precision with which treatment effects are estimated is not compromised from the use of RCBD on sand‐based putting green trials.
Air Temperature During Seed Filling and Soybean Seed Germination and Vigor
Authors: Egli D. B. , TeKrony D. M. , Heitholt J. J. , Rupe J.
Published: July 2010

High temperature stress during seed filling in controlled environments reduces soybean [Glycine max (L.) Merrill] seed germination and vigor, but the effect of high temperature in the field has not been determined. Seeds of two soybean cultivars (Hutcheson, maturity group [MG] V, and DP4690, MG IV) were produced in the field in Kentucky, Mississippi, Arkansas, and Texas in 2000 to 2002. Air temperature during seed filling was monitored and brown (mature) pods were harvested, hand threshed, and all shriveled and abnormal seeds were removed before determining standard germination and vigor (accelerated‐aging germination). Mean maximum temperatures during seed filling (growth stage R5 to R7) ranged from 24.0 (Kentucky) to 37.6°C (Texas). When seed lots infected with Phomopsis longicolla (Hobbs) were removed from the analysis, standard germination and accelerated‐aging germination (AA) decreased as mean maximum temperature during seed filling increased, but the decrease was significant (P = 0.05) only for Hutcheson. Standard germination of Hutcheson declined linearly (r
2 = 0.49) from near 100% at 24°C to 85% at 36°C, while the decrease in AA was curvilinear (R
2 = 0.86) and germination reached 11% at 36°C. Seeds of Hutcheson were more sensitive to high temperature than seeds of DP4690 and seed vigor (AA) was much more sensitive to high‐temperature stress than was standard germination. Our findings support the results of experiments in controlled environments by demonstrating that high temperature during seed filling in the field, without seed infection with P. longicolla or physical injury, reduced soybean seed germination and vigor.
myo‐Inositol, D‐chiro‐Inositol, and D‐Pinitol Synthesis, Transport, and Galactoside Formation in Soybean Explants
Authors: Gomes Carly I. , Obendorf Ralph L. , Horbowicz Marcin
Published: July 2010

Galactosides of myo‐inositol, D‐chiro‐inositol, and D‐pinitol, free cyclitols in soybean [Glycine max (L.) Merrill] plants, are seed storage products that accumulate during seed maturation and desiccation. There is no evidence for the synthesis of D‐chiro‐inositol and D‐pinitol in embryos. This study was conducted to determine whether D‐chiro‐inositol and D‐pinitol are synthesized in maternal tissues and if they are transported to soybean embryos and incorporated into their galactosides, fagopyritol B1 and galactopinitols, respectively. myo‐Inositol, D‐chiro‐inositol, and D‐pinitol were exogenously fed to soybean stem–leaf–pod explants. These explants were compared with control explants fed a solution without cyclitols. Galactosyl cyclitol products were extracted from mature seeds and analyzed by gas chromatography. Free cyclitol concentrations were higher in seed coats than in embryonic tissues. After feeding myo‐inositol, transient galactinol concentration was 50% higher and D‐chiro‐inositol concentration was threefold higher in mature embryos than in embryos from the control treatment. After feeding D‐chiro‐inositol, fagopyritol B1 concentration was 20‐fold higher and fagopyritol B2 concentration was 10‐fold higher than in embryos from the control treatment. After feeding D‐pinitol, galactopinitol concentrations were threefold higher than in embryos from the control treatment. Surgical removal of embryos from seed coats permitted an in planta study of phloem unloading by seed coats of developing soybean. Analysis of downloaded compounds demonstrated that myo‐inositol, D‐chiro‐inositol, and D‐pinitol are synthesized in maternal tissues, transported to soybean seeds, and directly unloaded from seed coats to embryos, whereas fagopyritols and galactopinitols are synthesized in embryonic tissues from transported D‐chiro‐inositol and D‐pinitol. Accumulation of fagopyritols and galactopinitols in maturing seeds is limited by the supply of D‐chiro‐inositol and D‐pinitol to the embryo.
Pollen–Pistil Interactions Result in Reproductive Isolation between Sorghum bicolor and Divergent Sorghum Species
Authors: Hodnett George L. , Burson Byron L. , Rooney William L. , Dillon Sally L. , Price H. James
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench] breeders have long recognized the importance of exotic germplasm and noncultivated sorghum races as sources of valuable genes for genetic improvement. The genus Sorghum consists of 25 species classified as five sections: Eu‐sorghum, Chaetosorghum, Heterosorghum, Para‐sorghum, and Stiposorghum Species outside the Eu‐sorghum section are sources of important genes for sorghum improvement, including those for insect and disease resistance, but these have not been used because of the failure of these species to cross with sorghum. An understanding of the biological nature of the incompatibility system(s) that prevent hybridization and/or seed development is necessary for the successful hybridization and introgression between sorghum and divergent Sorghum species. The objectives of this study were to determine the reason(s) for reproductive isolation between Sorghum species. The current study utilized 14 alien Sorghum species and established that pollen–pistil incompatibilities are the primary reasons that hybrids with sorghum are not obtained. The alien pollen tubes showed major inhibition of growth in sorghum pistils and seldom grew beyond the stigma. Pollen tubes of only three species grew into the ovary of sorghum. Fertilization and subsequent embryo development were not common. Seeds with developing embryos aborted before maturation, apparently because of breakdown of the endosperm.
Inheritance of High Levels of Adult‐Plant Resistance to Stripe Rust in Five Spring Wheat Genotypes
Authors: Navabi Alireza , Singh Ravi P. , Tewari Jalpa P. , Briggs Keith G.
Published: July 2010

Inheritance of adult‐plant resistance to stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici) in five spring wheats (Triticum aestivum L. em. Thell) following inoculation with the Mexican race Mex96‐11 was studied. All possible crosses among these resistant genotypes and a susceptible genotype, ‘Avocet‐YrA’, were made in a one‐way diallel mating design. F1 crosses, F2 populations, and F2:F3 and F5 single seed‐descent lines were evaluated under artificial field epidemics initiated with race Mex96‐11. The adult‐plant resistance in crosses of resistant parent with Avocet‐YrA tended to be incompletely dominant and was based on the interaction of gene Yr18 and at least three additional additive genes in each parent. Transgressive segregation was detected in all F2 populations and F5 single seed‐descent lines of the resistant parent inter‐crosses, indicating that some additive genes were nonallelic. Combining ability analyses indicated that additive gene effects were more important than nonadditive gene effects in the inheritance of adult plant resistance to stripe rust in the evaluated material. Estimates of narrow‐sense heritability ranged from 0.88 to 0.96. Stripe rust resistance in these wheats is expected to be durable.
Validation and Designation of Quantitative Trait Loci for Seed Protein, Seed Oil, and Seed Weight from Two Soybean Populations
Authors: Fasoula Vasilia A. , Harris Donna K. , Boerma H. Roger
Published: July 2010

In soybean [Glycine max (L.) Merr.], there is limited and inconsistent information on the confirmation of previously reported QTL. The objectives of this study were to: (i) confirm previously reported QTL for seed protein, seed oil, and seed weight in an independent population of PI97100 × ‘Coker 237’ with the same RFLP markers and (ii) verify previously reported QTL in an independent population of ‘Young’ × PI416937 for the same seed traits using SSR markers mapped in the same region as the original RFLP markers. Each population consisted of 176 F2:4 lines and was grown in randomized complete block trials in two or three different environments. Single‐factor analysis of variance was used to verify the QTL that had significant (P ≤ 0.01) associations. In the PI97100 × Coker 237 population, two (cqProt‐001 and cqProt‐002) of four previously described QTL for seed protein, two (cqOil‐001 and cqOil‐002) of three QTL for oil content, and none of three QTL for seed weight were confirmed in the independent population. In the Young × PI416937 population, none of the three previously reported QTL for protein was confirmed. One (cqOil‐003) of three QTL for oil content and two (cqSd wt‐001 and cqSd wt‐002) of three QTL for seed weight were verified. The unconfirmed QTL may have been false positive or they may have been specific for the sample of lines used in the original populations. These results confirm the necessity of validating QTL in parallel populations before utilizing them in a plant improvement program.
Extent of Cross‐Fertilization in Maize by Pollen from Neighboring Transgenic Hybrids
Authors: Ma B. L. , Subedi K. D. , Reid L. M.
Published: July 2010

There is an increasing concern about the preservation of genetic identity of conventional maize (Zea mays L.) and of distance required to segregate non‐genetically modified (non‐GM) from GM grain production since the introduction of Bacillus thuringiensis (Bt) and other transgenic events into commercial hybrids. Field experiments were conducted at three sites in Ottawa, Canada, for 3 yr to determine (i) the extent of cross‐fertilization of a maize genotype by foreign pollen of neighboring hybrids and (ii) the practical distance required to isolate conventional maize hybrids from neighboring GM maize fields. At each site, yellow‐kernel Bt maize was planted in the center (27 by 27 m) of a field surrounded in all directions by the distance equivalent to 24 or 48 rows (37 m) of white‐kernel maize, and a 200‐m non‐maize crop was maintained in all directions. Phenology and weather conditions were closely monitored during the tasseling and silking period. At maturity, a thorough examination on the cross‐fertilization was conducted in the white maize population. Our results showed that the rate of cross‐fertilization in maize was dependent upon the distance from the pollen source, wind direction and synchronization of silking and pollen shedding of the two genotypes involved. Up to 82% out‐cross was measured in the first row adjacent to the Bt maize. The level of out‐cross was <1% beyond the 37th border row (28 m) downwind and the 13th row (10 m) upwind in all site‐years. An exponential decline model was fitted well (P < 0.01) to the cross‐fertilization data as a function of distance from the yellow maize pollen source with R2 up to 0.64. Our data suggested that it is possible to produce non‐GM maize grains by removing the outside rows of non‐GM maize plants (about 30 m) neighboring the GM maize field in concern if the acceptance level is set at ≤1% out‐cross. The generally recommended 200‐m distance between two genotypes (inbreds, populations, hybrids, and wild relatives) appears to be appropriate for Bt or other GM maize, as well.
The Fate of Nitrogen‐15 Ammonium Sulfate Applied to Kentucky Bluegrass and Perennial Ryegrass Turfs
Authors: Engelsjord M. E. , Branham B. E. , Horgan B. P.
Published: July 2010

Turfgrasses that possess a spreading growth habit typically produce an organic layer, termed thatch, that has been shown to sequester significant quantities of applied nitrogen. This study was conducted to compare the fate of nitrogen in a thatchy Kentucky bluegrass (Poa pratensis L.) and a non‐thatch producing perennial ryegrass (Lolium perenne L.) turf. The effects of sampling time and sampling depths on the distribution of labeled fertilizer nitrogen (LFN) were investigated. Ammonium sulfate was applied to 36 microplots installed in a Marlette sandy loam soil (fine‐loamy, mixed, mesic Glossoboric Hapluadalfs) at a rate of 293 kg ha−1 yr−1 in six equal applications of 48.8 kg N ha−1, with the initial application containing 15N‐labeled (NH4)2SO4 Four microplots from each turf species were excavated on 17 June, 6 July, and 10 Aug. 1994 and on 15 June 1995 for nitrogen analysis. Two days after treatment, the Kentucky bluegrass LFN recoveries in shoot tissue, thatch, and soil were 34, 38, and 20% of the total LFN applied. These values changed to 47, 20, and 9% at 365 DAT. For perennial ryegrass, the corresponding values were 25, 28, and 27% at 2 DAT and 43, 10, and 14% at 365 DAT. Thatch was a better N sink than mat, but mat also sequestered significant quantities of LFN. Some downward movement of LFN was observed, particularly in perennial ryegrass. The very small LFN concentrations found in the 20‐ to 40‐cm soil layer confirms that leaching is not a major pathway for N loss from turf. Soil LFN was primarily found in the 0‐ to 5‐cm soil layer and as organic nitrogen. These results indicate that while thatch is important in reducing N leaching in turf, the absence of thatch does not dramatically alter nitrogen dynamics in turf.
Comparison of Bermudagrass, Bahiagrass, and Kikuyugrass as a Standing Hay Crop
Authors: Evers G. W. , Redmon L. A. , Provin T. L.
Published: July 2010

Stockpiling of warm‐season perennial grasses for grazing after frost is a management practice that can lower livestock production costs. Six seeded bermudagrass [Cynodon dactylon (L.) Pers.] cultivars, two bahiagrass (Paspalum notatum Flugge) cultivars, and a kikuyugrass (Pennisetum clandestinum Hochst. ex Chiov.) cultivar were compared with ‘Coastal’ and ‘Tifton 85’ bermudagrass in a small plot study in northeast Texas. Plots were sampled monthly from October through February in 1999 through 2002 to monitor accumulated dry matter (DM), crude protein (CP), and acid detergent fiber (ADF). Initial standing forage mass was <3000 kg DM ha−1 and remained relatively stable during the sampling period in the first 2 yr. In the third year, initial standing forage mass was >4000 kg DM ha−1 and declined during the sampling period for all entries. Standing forage mass of Tifton 85 bermudagrass was usually greater than the other entries. Crude protein decreased with time, but the rate of decline was related to initial CP concentrations and forage maturity at first frost. Bahiagrass cultivars and kikuyugrass generally had higher CP concentrations than bermudagrass cultivars. Crude protein concentrations were always above the minimum requirements for mature, nonlactating, pregnant beef cows (70–80 g kg−1). Acid detergent fiber increased with time for all entries, with the largest monthly increase usually occurring after December. The ADF concentration in bahiagrass cultivars was always higher than in bermudagrass cultivars and kikuyugrass. Species suitability for stockpiling forage was bermudagrass > kikuyugrass > bahiagrass. Tifton 85 was superior to the other bermudagrasses because of greatest autumn growth.
Molecular and Phenotypic Diversity of Common Bean Landraces from Nicaragua
Authors: Gómez Oscar J. , Blair Matthew W. , Frankow‐Lindberg Bodil E. , Gullberg Urban
Published: July 2010

The knowledge and understanding of the genetic structure of bean (Phaseolus vulgaris L.) landraces is important for the implementation of measures addressed to their management and conservation. The purpose of this paper was to study the pattern of genetic variation in nine red‐seeded landraces currently grown by farmers with molecular and phenotypic markers. Twelve individuals per landrace were genotyped with seven bean microsatellite markers. Fourteen phenotypic traits were additionally measured in a field study in two localities. An important finding of this study was the complementary information obtained with both kinds of markers. Most of the variation at the molecular level was explained by differences within or among landraces but not among agroecological zones, while at the phenotypic level most of the variation was attributed to differences among agroecological zones. This suggests that molecular differentiation of landraces [coancestry coefficient (FST) = 0.34] was due to founder effect while phenotypic differentiation was due to the effect of adaptation. Within landraces, an average of 5.7 alleles per locus was identified, with a range from 2 to 13 alleles depending on the individual microsatellite. The average gene diversity within landraces and total gene diversity was 0.35 and 0.51, respectively. Implications of the findings in planning future collections of genetic resources of common bean as well as the effect of sites on uncovering adaptive traits are also discussed.
Effects of Random Mating on Marker–QTL Associations in the Cross of the Illinois High Protein × Illinois Low Protein Maize Strains
Authors: Dudley J. W. , Dijkhuizen A. , Paul C. , Coates S. T. , Rocheford T. R.
Published: July 2010

The effects of random mating on population performance and identification of marker–quantitative trait loci (QTL) associations were studied in the cross of the Illinois High Protein (IHP) and Illinois Low Protein (ILP) maize (Zea mays L.) strains. The F1 was randomly mated to produce the Syn0 and Syn4 generations. Two hundred Syn0 S1 and 200 Syn4 S1 lines were crossed to two inbred testers. The S1 lines per se and the testcrosses (TCs) were evaluated for grain protein, starch, and oil concentrations in four environments. Genetic variance for protein and starch was reduced from the Syn0 to the Syn4 and genetic variance for the S1 lines per se was greater than for the TCs. Heritability was similar in the Syn0 and Syn4. With single factor (SF) analysis, the number of significant marker–QTL associations for protein and starch in the Syn4 was drastically reduced from the number found in the Syn0. Multiple regression (MR) analysis supported this result. Very few significant marker–QTL associations for oil were found in either the Syn0 or Syn4. Agreement between the testers and the S1 lines per se for chromosomal regions identified as associated with QTL for starch and protein was high. Genotypic correlations of starch with protein ranged from −0.96 to −0.98. However, three markers had the same sign and significant additive effects for both starch and protein in the S1 progeny and both TCs. Such markers should be useful for simultaneous selection for high starch and high protein.
Diverse Adapted Populations for Improving Northern Maize Inbreds
Authors: Taller Jennifer M. , Bernardo Rex
Published: July 2010

Inbred recycling has narrowed the diversity of U.S. Corn Belt germplasm. Exotic populations, landraces, open‐pollinated populations, and synthetic populations are possible sources of new germplasm. The objectives of this study were to (i) identify the best maize (Zea mays L.) populations among a diverse group of 17 early populations for improving an elite single cross, LH 227 × LH 295, and (ii) determine the genetic diversity among the populations and Minnesota inbreds from the Iowa Stiff Stalk Synthetic (BSSS) and non‐BSSS heterotic groups. The LH 227 × LH 295 single cross, the two parental inbreds, and the testcrosses of the 17 populations to LH 227 and to LH 295 were evaluated at three Minnesota locations in 2002. The genetic diversity among the populations and Minnesota inbreds A632 and A679 (BSSS) and A619 and A682 (non‐BSSS) was assessed with 55 simple sequence repeat (SSR) markers. Yield data were used in a quantitative genetic model to estimate, in each population, the relative frequency of favorable dominant alleles (lp̄lμ) not found in LH 227 × LH 295. Cateto, AS5, ASA(FNI)C5, and ASA(FI)C5 had the highest lp̄lμ values for yield. Cluster analysis of SSR data grouped these four populations in one cluster and the Minnesota inbreds in a different cluster. We concluded that Cateto, a synthetic from South America adapted to the northern Corn Belt, is a suitable population for improving LH 227 × LH 295.
Occurrence of a New Russian Wheat Aphid Biotype in Colorado
Authors: Haley Scott D. , Peairs Frank B. , Walker Cynthia B. , Rudolph Jeffrey B. , Randolph Terri L.
Published: July 2010

Russian wheat aphid [RWA, Diuraphis noxia (Mordvilko)] is a serious pest of wheat (Triticum aestivum L.) in the western USA Great Plains region. While variation in virulence among different RWA isolates has been reported elsewhere, no such variation has been documented among North American RWA isolates. Our objective was to confirm observations in spring 2003 suggesting that a new biotype of RWA was present in southeastern Colorado. The new biotype induced greater injury (leaf rolling and overall plant damage) than the original biotype in standard greenhouse seedling screening tests with a limited collection of resistant and susceptible cultivars. A second experiment with a broader collection of known RWA resistance sources identified only one accession, 94M370 (Dn7 gene), with resistance to the new biotype. Development of wheat cultivars with resistance to this new biotype will depend on rapid identification and deployment of new resistance sources.
Genetic Variation for Carbon Isotope Discrimination in Sunflower
Authors: Lambrides C. J. , Chapman S. C. , Shorter R.
Published: July 2010

Plants accumulate isotopes of carbon at different rates because of discrimination against 13C relative to 12C. In plants that fix carbon by the C3 pathway, the amount of discrimination correlates negatively with transpiration efficiency (TE) where TE is the amount of dry matter accumulated per unit water transpired. Therefore, carbon isotope discrimination (Δ) has become a useful tool for selecting genotypes with improved TE and performance in dry environments. Surveys of 161 sunflower (Helianthus spp.) genotypes of diverse origin revealed a large and unprecedented range of genetic variation for Δ (19.5–23.8‰). A strong negative genetic correlation (rg) between TE and Δ (rg = −0.87, P < 0.001) was observed in glasshouse studies. Gas exchange measurements of field grown plants indicated that Δ was strongly correlated with stomatal conductance to water vapor (g), (rg = 0.64, P < 0.01), and the ratio of net assimilation rate (A) to g, (rg = −0.86, P < 0.001), an instantaneous measure of TE. Genotype CMSHA89MAX1 had the lowest TE (and highest Δ) of all genotypes tested in these studies and low yields in hybrid combination. Backcrossing studies showed that the TE of this genotype was due to an adverse effect of the MAX1 cytoplasm, which was inherited from the diploid perennial H. maximiliani Schrader. Overall, these studies suggested that there is an excellent opportunity for breeders to develop sunflower germplasm with improved TE. This can be achieved, in part, by avoiding cytoplasms such as the MAX1 cytoplasm.
Crop Yield and Nitrogen Accumulation Response to Tillage of a Coastal Plain Soil
Authors: Hunt P. G. , Bauer P. J. , Matheny T. A. , Busscher W. J.
Published: July 2010

Delineation of the benefit derived from either surface or subsoil tillage is important for the advancement of soil‐conserving crop production systems in the Coastal Plain. The objective of this experiment was to measure the impact of surface and subsoil tillage of a sandy Coastal Plain soil (fine‐loamy, siliceous, thermic Typic Kandiudult) on grain yield and nitrogen accumulation for a 2‐yr rotation of corn (Zea mays) and wheat–double‐cropped soybean {(Triticum aestivum L.) and [Glycine max (L.) Merr.]}. Soils of the experimental plots initially possessed different surface residue and organic matter characteristics because they had received in‐row subsoiling with either surface‐disking tillage or no surface tillage for the previous 18‐consecutive years. The current experiment was conducted from 1997 to 2001, which was an exceptionally dry period. Thus, results of this experiment provide insight into how these cropping and tillage treatments performed during one of the driest 5‐yr periods of the last half century. In each year, both phases of the crop rotation were grown in plots with the following tillage treatments: (i) neither surface nor subsoil tillage, (ii) paratill subsoiling without surface tillage, (iii) surface tillage without subsoiling, and (iv) both surface tillage and paratill subsoiling. Soybean was not significantly affected by any tillage treatment. With subsoiling, corn grain yields (4‐yr means) were not significantly different with surface‐disking tillage versus no surface tillage (4.98 and 4.92 Mg ha−1, respectively). Without subsoiling, corn yields were higher with no surface tillage (4.24 Mg ha−1) than with surface‐disking tillage (3.51 Mg ha−1). Likewise, with subsoiling, wheat grain yields (5‐yr means) were not significantly different with surface‐disking tillage versus no surface tillage (3.12 and 3.24 Mg ha−1, respectively). Without subsoiling, wheat grain yields were higher with no surface tillage (2.80 Mg ha−1) than with surface‐disking tillage (2.59 Mg ha−1). Nitrogen accumulations in both shoot dry matter and grain generally followed the treatment responses of grain yield. Thus, during this dry period, surface no‐till and the associated accumulation of organic matter could only somewhat compensate for the need to subsoil. With or without surface tillage, paratill subsoiling was very beneficial for corn and wheat yields.
Sequence Diversity of Puroindoline‐a, Puroindoline‐b, and the Grain Softness Protein Genes in Aegilops tauschii Coss
Authors: Massa A. N. , Morris C. F. , Gill B. S.
Published: July 2010

Aegilops tauschii Coss. constitutes a valuable resource of genetic variability for improving cultivated bread wheat, Triticum aestivum L. Nucleotide sequence diversity was examined at the Hardness (Ha) locus, which bears the Puroindoline‐a (Pina‐D1) and Puroindoline‐b (Pinb‐D1) genes, and the closely related Gsp‐D1 gene. A distinct signature of polymorphism and selection was evident in each of the three genes across loci for the 50 accessions of Ae. tauschii Pinb‐D1 was characterized by a high level of nucleotide diversity (π = 0.02966; θ = 0.0166) relative to a low level of variation in the neighboring linked Pina‐D1 and Gsp‐D1 genes. Despite the close genetic and physical linkage among these three loci, recombination and linkage disequilibrium analyses detected at least two recombination events, most likely at the interlocus level. Tests for neutrality showed that polymorphism at Pina‐D1 and Gsp‐D1 did not depart from a drift–mutation model. Genetic variation at the Pinb‐D1 locus was higher than expected under neutrality suggesting that selection might operate to maintain polymorphism at this locus. The sequence variation resolved here will help elucidate the kind of variation that may be important for the function of these genes as well as to identify novel Ae. tauschii genotypes that may be used to broaden the range in wheat endosperm texture. Lastly, these results on sequence diversity, linkage disequilibrium, and recombination may help in the development of new strategies for breeding purposes.
Inheritance and Characterization of Angular Leaf Spot Resistance Gene Present in Common Bean Accession G 10474 and Identification of an AFLP Marker Linked to the Resistance Gene
Authors: Mahuku George , Montoya Carmenza , Henríquez María Antonia , Jara Carlos , Teran Henry , Beebe Stephen
Published: July 2010

Angular leaf spot (ALS), caused by the fungus Phaeoisariopsis griseola (Sacc.) Ferr., is one of the most important diseases of common bean (Phaseolus vulgaris L.) in tropical and subtropical bean producing areas. The common bean accession G 10474 has been widely resistant to P. griseola, including pathotype 63‐63, one of the most virulent P. griseola pathotypes characterized. The objectives of this study were to determine the inheritance of angular leaf spot resistance and to identify molecular markers linked to the resistance gene in G 10474. Resistance to P. griseola pathotypes 63‐63 in G 10474 was investigated in F2 populations derived from a cross between G 10474 and Sprite (universally susceptible). Inoculation of parents, F1, F2, and backcross‐derived plants with race 63‐63 revealed that a single dominant gene conditioned ALS resistance in G 10474. A combination of the amplified fragment length polymorphism (AFLP) technique and bulked segregant analysis (BSA) was applied to the F2 population to identify molecular markers linked to the ALS resistance gene in G 10474. Three AFLP markers (E‐ACA/M‐CTT330, E‐AAC/M‐CAG310, and E‐AAC/M‐CAT285) segregated in coupling phase with the resistance gene in G 10474. The E‐ACA/M‐CTT330 marker was successfully converted to a codominant sequence characterized amplified region (SCAR) marker at 5 cM from the resistance gene. Validation of the SCAR marker outside the mapping population showed that the utility of this marker for marker‐assisted selection (MAS) was limited to the Andean gene pool of P. vulgaris. Therefore, the SCAR marker we report can only be used to introgress the ALS resistance of G 10474 into Andean backgrounds.
Effects of Growth Regulators on In Vitro Plant Regeneration in Durum Wheat
Authors: Satyavathi V. V. , Jauhar P. P. , Elias E. M. , Rao M. B.
Published: July 2010

Work on improvement of durum wheat (Triticum turgidum L.) using tools of biotechnology is limited. Development of a reliable in vitro plant regeneration procedure for this important cereal is a prerequisite for its improvement by genetic transformation. Here, we report the effects of three growth regulators (GRs), 2,4‐D (2,4‐dichlorophenoxyacetic acid), picloram (4‐amino‐3,5,6‐trichloropicolinic acid), and dicamba (3,6‐dichloro‐o‐anisic acid), on callus induction and plant regeneration from scutellum cultures of four commercial durum cultivars: Ben, Maier, Munich, and Lebsock. Callus induction was obtained from isolated scutella cultured on modified Murashige and Skoog (MS) basal medium. After 4 wk of callus induction, all calli were plated on MS basal medium for regeneration. The regenerated plantlets were fertile, maintained the normal chromosome number (2n = 4x = 28) and structure as revealed by fluorescent genomic in situ hybridization (fl‐GISH), and showed no apparent somaclonal variation. Genotype and callus induction medium played a dominant role in plantlet regeneration. Dicamba proved the best GR for inducing compact callus and also gave the highest proportion (0.16) of regenerated plants across the four cultivars. Overall, Maier gave the highest proportion (0.27) of plantlet regeneration when dicamba at 2.0 mg L−1 concentration was used for initial callus induction. These results will facilitate genetic transformation work with durum wheat.
Release of Seed Dormancy in Field Plantings of Eastern Gamagrass
Authors: Gibson Lance R. , Aberle Ezra Z. , Knapp Allen D. , Moore Kenneth J. , Hintz Roger
Published: July 2010

Seed dormancy is a main factor limiting the use of eastern gamagrass (Tripsacum dactyloides L.) for forage and conservation purposes; however, there is little available information on the seed bank dynamics of eastern gamagrass plantings. Knowledge of the degree and rate of seed dormancy loss would improve decisions concerning eastern gamagrass plantings and provide a better understanding of the seed bank longevity for this species. In this study, cold, moist stratified seed or unstratified seed was planted at 2.5‐ and 5.0‐cm depths on 16 Aug. 1999, 1 Nov. 1999, 14 April 2000, 15 May 2000, and 16 June 2000 for the first year of the study and 15 Aug. 2000, 31 Oct. 2000, 17 April 2001, 15 May 2001, and 15 June 2001 in the second year. Plants and seeds were retrieved at 3, 6, 9, and 12 mo after planting of 50 seeds for each seed treatment and planting depth combination. Intact seeds were germinated for 28 d and the viability of ungerminated seeds was determined with a tetrazolium test. Seed dormancy of both stratified and unstratified eastern gamagrass seed was lost mostly between mid‐September and mid‐November. No more than 12% dormant seed remained after mid‐December and dormancy was completely lost by April and May. Seed dormancy in eastern gamagrass was substantially reduced with several weeks of soil temperatures below 15°C and adequate soil moisture.
Confirming QTLs and Finding Additional Loci Conditioning Sheath Blight Resistance in Rice Using Recombinant Inbred Lines
Authors: Pinson Shannon R. M. , Capdevielle Fabian M. , Oard James H.
Published: July 2010

One method for confirming the existence of quantitative trait loci (QTLs) is to identify loci of similar location and effect in multiple populations and/or environments. The literature contains two prior publications reporting the location of QTLs affecting resistance to sheath blight (SB) disease in rice (Oryza sativa L.), but lack of agreement between QTLs in the studies left all 12 unconfirmed, limiting the potential of marker‐assisted selection of this trait with worldwide importance. The earlier linkage analyses were imprecise due to heterozygosity, segregation, and limited plot size and replication. We evaluated a replicated set of pure‐breeding recombinant inbred lines (RILs) to increase reliability of the quantitative disease data and in turn improve accuracy of the QTL mapping. The RILs were F2:10 descendants from an early‐generation ‘Lemont’ × ‘Teqing’ population wherein SB resistance QTLs (SB‐QTLs) were first identified. The present study confirmed the location and effect of six SB‐QTLs, confirmed the existence but not the specific location of another, and identified eight new loci. Three of the confirmed QTLs were also found to be independent from undesirable plant height and maturity effects. This research demonstrated the importance of using replicated phenotypic data for reliably establishing the identity and effect of putative QTLs for complex traits such as SB resistance. Further marker development to facilitate marker‐assisted selection of these three SB‐QTLs is warranted.
Breeding CWG‐R Crested Wheatgrass for Reduced‐Maintenance Turf
Authors: Hanks Justin D. , Waldron Blair L. , Johnson Paul G. , Jensen Kevin B. , Asay Kay H.
Published: July 2010

Using reduced‐maintenance turfgrass as an alternative to current high‐maintenance turfgrass species would conserve resources, reduce labor, and potentially reduce pollutants in the environment. CWG‐R is an experimental population of crested wheatgrass [Agropyron cristatum (L.) Gaertn.] from Iran that has shown potential as a low‐maintenance turf. The objective of this research was to estimate the genetic variation for turf traits within the CWG‐R population when evaluated under a reduced‐maintenance regimen. Ninety CWG‐R clonal lines were established in 1998 near Logan, UT, as spaced‐plant plots in a RCB design with four replicates. Maintenance of 50% ET0 replacement, 97.74 kg of nitrogen ha−1 yr−1, and mowing at 7.62 cm was approximately 40% lower than typical for high‐input Kentucky bluegrass (Poa pratensis L.) turf. Critical turf traits, including spring regrowth, season‐long (March–October) and mid‐summer (June–July) turf quality, color, and rhizomatous spread were evaluated in 1999 and 2000. Significant genetic variation among clonal lines was evident with broad‐sense heritabilities of 0.65, 0.76, 0.45, and 0.76 for spring regrowth, season‐long turf quality, color, and rhizomatous spread, respectively. Several clonal lines remained green throughout the summer months and maintained acceptable turf quality and color ratings during the critical mid‐summer period. The high broad‐sense heritability estimates within this population indicate potential for successful improvement of critical turf traits by phenotypic selection. These results indicate that that CWG‐R could be an important low‐maintenance turf‐type crested wheatgrass germplasm.
New Sources of Resistance to Gummy Stem Blight in Watermelon
Authors: Gusmini Gabriele , Song Ronghao , Wehner Todd C.
Published: July 2010

Gummy stem blight, caused by Didymella bryoniae (Auersw.) Rehm, is a major disease of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. Plant breeders need sources of resistance that can be incorporated into adapted breeding lines to help control the disease. We tested all the available accessions from the USDA‐ARS watermelon germplasm collection, including C. lanatus var citroides (L.H. Bailey) Mansf., for resistance to gummy stem blight. The experiment was a randomized complete block with 1332 cultigens, two sites (field and greenhouse), two or four replications, and two to six plants per plot. The resistant check was PI 189225 and the susceptible check was ‘Charleston Gray’. PI 279461, PI 482379, PI 254744, PI 526233, PI 482276, PI 271771, PI 164248, PI 244019, PI 296332, and PI 490383 were selected as the most resistant cultigens to be used in future breeding efforts. The most susceptible cultigens were PI 183398, PI 169286, PI 223764, PI 226445, PI 525084, PI 534597, and PI 278041.
Evaluation of Ancestral Lines of U.S. Soybean Cultivars for Resistance to Four Soybean Viruses
Authors: Wang Y. , Hobbs H. A. , Hill C. B. , Domier L. L. , Hartman G. L. , Nelson R. L.
Published: July 2010

Fifty‐two North American (NA) ancestral soybean [Glycine max (L.) Merr.] lines were screened for resistance to Bean pod mottle virus (BPMV), Soybean mosaic virus (SMV) strains G1 and G5, Tobacco ringspot virus (TRSV), and Tobacco streak virus (TSV). Seven ancestors, ‘CNS’, ‘Haberlandt’, ‘Ogden’, ‘Peking’, PI 71506, PI 88788, and ‘Tokyo’, were resistant to SMV‐G1. Sixteen entries, ‘A.K. (Harrow)’, ‘Capital’, CNS, FC 33243, Haberlandt, ‘Illini’, ‘Improved Pelican’, ‘Laredo’, ‘Lincoln’, ‘Mandarin’, ‘Mandarin (Ottawa)’, Ogden, ‘Palmetto’, Peking, PI 88788, and Tokyo were resistant to SMV‐G5. All ancestral lines tested were susceptible to BPMV and TRSV. Only one ancestor, ‘Tanner’, was resistant to TSV. On the basis of cultivar registration articles through 2002, there were 15 public soybean cultivars with reported resistance to SMV. The possible donors of resistance for each were identified. Two soybean ancestors, CNS and Ogden, were the most important possible sources of SMV resistance genes in U.S. commercial soybean cultivars, as the pedigree of 75 and 56% of the reported resistant cultivars contained CNS and Ogden, respectively. In most of the cultivar registration articles, reactions to SMV were not reported. With the relatively high frequency of SMV resistance in major ancestral lines, SMV resistance in U.S. cultivars may be more common than expected.
Inheritance of Seed Shattering in Interspecific Hybrids between Fagopyrum esculentum and F. homotropicum
Authors: Wang Yingjie , Scarth Rachael , Campbell G. Clayton
Published: July 2010

Fagopyrum esculentum Moench, common buckwheat (2n = 2x = 16), is a sporophytic self‐incompatible species with dimorphic flowers, which is resistant to seed shattering, a trait often lost in interspecific crosses. The objective of this study was to determine the inheritance of seed shattering in interspecific crosses with the shattering species F. homotropicum Ohnishi [=F. esculentum var. homotropicum (Ohnishi) Q‐F. Chen] (2n = 2x = 16) to use this species in buckwheat improvement. Four interspecific crosses between F. homotropicum and F. esculentum were made by means of ovule culture. Eight F2 populations derived from F1 single plants were developed and 28 F3 lines from F2 shattering plants were used for progeny testing. The F1 interspecific hybrids expressed seed shattering, indicating that shattering is dominant to nonshattering. The F2 populations from individual F1 plants segregated in the ratios of 3:1, 9:7, and 27:37, supporting the control of shattering by three complementary dominant genes, the first report of multiple gene control in buckwheat. The F3 progeny testing confirmed the F2 segregation patterns. The different segregation ratios in the F2 populations may have been caused by heterogeneity of F. esculentum because of cross‐pollination. The proposed genetic model describes the genotype of F. homotropicum as homozygous dominant to explain the absence of nonshattering genotypes. Fagopyrum esculentum genotypes are homozygous recessive at a minimum of one locus to explain the absence of shattering genotypes. This model provides an explanation for the occurrence of shattering phenotypes from crosses between two nonshattering parents and nonshattering phenotype from crosses between, or selfing of, shattering plants.
Tillage Effects on Canopy Position Specific Cotton Fiber Properties on Two Soils
Authors: Bauer Philip J. , Frederick James R.
Published: July 2010

The benefits of conservation tillage on soil water availability are well established, but this soil management practice generally does not affect cotton (Gossypium hirsutum L.) fiber properties of the whole crop. The objective was to determine whether soil management practices affect canopy position specific fiber properties on two soils. A 3‐yr field study was conducted with plots on two soil types [Bonneau loamy sand (loamy, siliceous, thermic Arenic Paleudult) and Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudult)]. Treatments in the study were cover crop [none and rye (Secale cereale L.)] and tillage system (disk tillage and conservation tillage). Fiber properties were determined from hand picked samples at three canopy positions (first sympodial position bolls at Mainstem Nodes 6 and 7, 9, and 10, and 12 and 13). Yield and fiber properties of the whole crop were determined after machine harvesting. In two of the 3 yr, conservation tillage had 34% higher yield than disk tillage. Conservation tillage had higher fiber length uniformity every year, but no consistent differences between tillage systems occurred for the other fiber properties. Cover crop did not influence within‐canopy fiber properties. When differences occurred between tillage systems for fiber length at specific canopy positions, fibers from conservation tillage were about 1 mm longer than fibers from disk tillage. Fiber length uniformity results were similar to those for fiber length. Disk tillage resulted in cotton with 0.22 lower micronaire units than conservation tillage at Mainstem Nodes 6 and 7 when rainfall was plentiful in 1997, but had micronaire that was 0.82 units higher than conservation tillage at that canopy position during the dryer year of 1998. Within canopy variability for micronaire was greater on the more drought susceptible Bonneau soil than on the Norfolk soil. Results indicate that tillage management can influence canopy position specific fiber property distribution.
Screening Sunflower for Resistance to Sunflower chlorotic mottle virus and Mapping the Rcmo‐1 Resistance Gene
Authors: Lenardon S. L. , Bazzalo M. E. , Abratti G. , Cimmino C. J. , Galella M. T. , Grondona M. , Giolitti F. , León A. J.
Published: July 2010

Sunflower chlorotic mottling is an emerging virus disease which has been detected in commercial hybrids and wild sunflowers in Argentina. Two hundred thirty‐two sunflower (Helianthus annuus L.) lines were screened for resistance to Sunflower chlorotic mottle virus (SuCMoV) using artificial inoculations under greenhouse conditions. Only three lines (L33, L74, and L52) showed a partial resistance, L33 being the most resistant. Virus replication was delayed (A405 in DAS‐ELISA) and morphological traits (plant height and leaf width) were less affected in this line and its various hybrid combinations than in susceptible controls. Segregation data from an artificially inoculated F2 population, under greenhouse and field conditions, indicated the presence of a single dominant resistance gene which was designated Rcmo‐1 This gene was mapped on Linkage Group 14 between markers MS0022 (5 cM) and ORS‐307 (4 cM). Linkage between the two markers and the Rcmo‐1 locus was confirmed in a field evaluation.
Spatial Analysis of cDNA Microarray Experiments
Authors: Burgueño Juan , Crossa Jose , Grimanelli Daniel , Leblanc Olivier , Autran Daphne
Published: July 2010

Microarray experiments allow RNA level measurements for many genes in multiple samples. However, mining the biological information from the large sets of data generated by microarrays requires the use of appropriate statistical methods to adjust the observed values for experimentally introduced variability (normalization process) before testing differences among samples. Normalization of microarray experiments is a critical step for reducing false positives and false negatives. This paper explores the normalization of cDNA microarray experiments by a method that uses the blank spot intensity values to make spatial adjustment (SA) of both foreground and background DNA spot intensity values, by fitting an autoregressive mixed linear model through the residual maximum likelihood (REML) methodology in the direction of the rows and the columns of the microarray. Application of this spatial normalization to three cDNA array experiments serves as a case study to validate the SA. Results show that the spatial analysis allows selection of candidate genes with lesser numbers of false positive and false negative genes.
Plant Growth Regulators Alter Kentucky Bluegrass Canopy Leaf Area and Carbon Exchange
Authors: Beasley Jeffrey S. , Branham Bruce E. , Spomer L. Arthur
Published: July 2010

Turf managers apply plant growth regulators (PGRs) throughout the growing season to reduce clipping production, provide a uniform canopy, and increase color. Reduced efficacy of trinexapac‐ethyl (TE) [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS, 3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl) pentan‐3‐ol] has been reported during warmer summer months. Plant growth regulator dissipation and Kentucky bluegrass (KBG; Poa pratensis L.) clipping production, canopy leaf area, and carbon exchange rates (CERs) were measured following single TE or PAC applications applied at three rates and three application timings. Warmer summer conditions reduced the intensity and duration of TE and PAC growth suppression compared to spring applications. Plant growth regulator applications above the manufacturers label rate provided no additional suppression. Residues of PGRs were analyzed by HPLC‐UV. Warmer temperatures increased TE and PAC uptake, but accelerated the rate of PGR dissipation. Carbon exchange rates were measured weekly on ground (CERG) and leaf (CERL) area bases. Treatment with PGRs resulted in decreased leaf area early during inhibition followed by increased rate of leaf area production. Changes in canopy leaf area were greatest in spring and PAC caused the greatest change in leaf area. Changes in CERG reflected changes in leaf area. Paclobutrazol generally increased CERL during periods of clipping suppression, while TE had no effect on CERL.