bluuebunny/crossref_metadata_2025 huggingface dataset:
Dry Weight Production and Nitrogen Efficiency Traits in Kentucky Bluegrass Cultivars in Nutrient Solution and Soil
Authors: Bertauski Anthony F. , Swiader John M. , Wehner David J.
Published: July 2010

Because of the importance of such factors as appearance and vigor in turf management, genetic selection of Kentucky bluegrass (Poa pratensis L.) is often conducted at high levels of N application. This process can mask potential differences between genotypes in N efficiency, especially under low N levels. The case is also made that because soil is the medium in which plant selections ultimately must perform, culfivar screening for N efficiency in solution culture should relate to results in soil. This study was conducted to evaluate N‐utilization efficiency (NUE—mg plant dry matter mg−1 plant N) in six bluegrass cultivars at low (0.2, 0.7 mM NO3‐N) and high (3.5 mM NO3‐N) levels of N supply in nutrient solution culture( nutriculture) and soil. With high N supply, total plant N accumulation and N‐root uptake efficiency (NRE‐mg plant N g−1 root dry matter) increased in each cultivar, while NUE and shoot efficiency ratio (SER‐mg shoot dry matter mg−1 shoot N) decreased, with the magnitude and relative response dependent on genotype and medium. As a group, as well as individually, cultivars Asset, Dawn, and Trenton were higher yielding, more responsive to increasing solution N concentration, and more efficient (NUE) at low levels of N supply than cultivars Limousine, Barzan, or Midnight. Under low N supply, NUE in nutriculture ranged from 26.2 (g plant dry weight mg−1 N) in Limousine to 40.1 in Asset, and in soil from 63.6 in Midnight to 77.4 in Asset. Differences in NUE among cultivars were more associated with shoot efficiency than with root absorption efficiency. Despite noticeably higher NUE in soil than in nutriculture, and significant effects of N fertility, genotypic differences in the various N efficiency traits in solution culture were also apparet in soil. The results suggest that NUE in Kentucky bluegrass can be enhanced by cultivar selection under low‐N conditions. while the similarities of the actual N conditions between nutriculture and soil remain in question, it appears that solution culture can be used as an effective surrogate for characterizing NUE in divergent types of bluegrass cultivars.
Phytochemical Changes during Recurrent Selection for Resistance to the European Corn Borer
Authors: Bergvinson David J. , Arnason John T. , Hamilton Robert I.
Published: July 2010

Feeding performance of herbivorous insects is influenced by host plant nutritional quality which can be improved for insect resistance by artificial selection. This study was conducted to determine which biochemical constituents in maize (Zea mays L.) change during recurrent selection for resistance to first‐ and second‐generation European corn borer (ECB) [Ostrinia nubilalis (Hübner)]. Four cycles of selection (C0, C2, C4, and C5) from the BS9 population were field grown, artificially and naturally infested with ECB, and the following tissues sampled for biochemical analysis: immature and mature leaf blade, leaf sheath, rind, node, and pith. Tissue was analyzed for percent protein, DIMBOA [2,4‐dihydroxy‐7‐methoxy 2H‐l,4‐benzoxazin‐3 (4H)‐one], fiber, and cell wall‐bound phenolics, which included p‐coumaric acid (pCA), ferulic acid (FA), cyclobutane dimers (CBD), and diferulic acid (DFA). Leaf and stalk toughness were also determined and showed significant increases over cycles of selection. Protein content was lowest in stalk tissues with advanced cycles having lower levels, but leaf protein content did not differ significantly. DFA reached high levels in the rind (0.85 mg/g) and leaf sheath (1.35 mg/g) tissues, and increased significantly in immature leaf tissue (0.55–1.02 mg/g) over cycles of selection and may serve to fortify tender whorl tissue. Number of tunnels per stalk was negatively correlated with DFA content in the pith (r = − 77, P = 0.02). Microspectrophotometer determinations of epidermal cell wall absorbance for leaf blade and rind tissue showed increased absorbances (23 and 27%, respectively) in the spectral region characteristic of phenolic acids over cycles of selection. Phenolic acids, in particular DFA, have increased over cycles of selection to render maize tissue more resistant through fortification of cell walls, especially in leaf and rind epidermal tissue.
Genetic Relatedness among Soybean Genotypes Using DNA Amplification Fingerprinting (DAF), RFLP, and Pedigree
Authors: Prabhu R. R. , Webb D. , Jessen H. , Luk S. , Smith S. , Gresshoff P. M.
Published: July 2010

Numerous methods now exist for plant breeders and others to estimate genetic relationships among different germplasm. Two of the most commonly used methods have been restriction fragment length polymorphism (RFLP) and pedigrees. The objective of this study was to compare a relatively new method, DNA amplification fingerprinting (DAF), which is a short, arbitrary‐primer, polymerase chain reaction (PCR)‐amplification method, to RFLP and pedigree methods for genetic distance estimation among soybean [Glycine max (L.) Merr.] genotypes. The genotypes consisted of agronomically important soybean lines Archer, BSR101, Forrest, Hartwig, 9171, 9341, 9392, 9593, S8330 and the plant introduction, PI437.654. The 10 genotypes were evaluated by means of 53 RFLP clones, a subset of 12 RFLP clones, seven DAF primers, and available pedigrees. The DAF data set and the subset of 12 RFLP clones each consisted of 18 markers. For each method, the data were used to calculate the 45 pairwise genetic‐distance estimates among the varieties using the average linkage algorithm in SAS. The genetic‐distance estimates were correlated from 0.63 to 0.89 among the four methods. Dendrograms based on each method were therefore considered similarly reliable. For varietal identification, the DAF and RFLP markers distinguished the varieties with similar efficiency. We conclude that both DAF and RFLP marker technologies and pedigrees are useful tools for estimating genetic distances in soybean.
Characterization of a Yield Quantitative Trait Locus on Chromosome Five of Maize by Fine Mapping
Authors: Graham Geoffrey I. , Wolff David W. , Stuber Charles W.
Published: July 2010

In an earlier study for identifying quantitative trait loci (QTLs) a maize (Zea mays L.) population generated from the cross B73 × Mo17, a major effect on grain yield and yield related traits was detected on chromosome 5. This chromosomal region has also shown significant associations with grain yield in several other studies. These findings have, thus, provided the impetus to further characterize this segment. A set of BC2S1 lines was created, each containing an intrugressed segment of Mo17 in a B73 background. A reciprocal set of lines, each with a B73 donor segment in a Mo17 background, also was created. These BC2S1 lines were genotyped by means of 16 restriction fragment length polymorphism (RFLP) and two isozyme markers that mapped to the targeted region on chromosome 5. From field data based on testcrosses of these lines, this one large region on chromosome 5 was dissected into at least two smaller QTLs. Effects at these two QTLs appear to act in a dominant manner, each showing significance in one testcross but not the other. These genetic factors are in repulsion phase linkage and their effects support the dominance theory of heterosis. One other segment in this region on chromosome 5 showed a significant association with yield, but it was not consistently expressed and may be spurious. The largest of these three segments has been mapped to a 27.5‐centimorgan (cM) interval near Amp3. if the observed results are indicative of the true complexity associated with QTLs having large effects, marker‐aided breeding involving such regions could be difficult, particularly if the marker‐aided breeding is based on early generation (backcross, F2, or F3) data, where the intricate nature of a region cannot be resolved.
Pedigree and RAPD‐Based DNA Analysis of Commercial U.S. Rice Cultivars
Authors: Cao D. , Oard J. H.
Published: July 2010

Pedigree information has traditionally been used to obtain estimates of genetic variation, predict hybrid performance, and select parents for crossing in crop improvement programs. We have generated and compared pedigree and randomly amplified polymorphic DNA (RAPD) data obtained from 26 elite cultivars and lines rice (Oryza sativa L.) recommended for commercial production in Louisiana and elsewhere in the USA. For the RAPD analysis, 220 commercially available primers (10‐mers) were evaluated for their ability to distinguish pairwise combinations of the cultivars‐lines that included four sets of full sibs. A total of 69 primers produced 92 polymorphic bands, 0.25 to 3.5 kb in size. Seven primers were identified that could differentiate all cultivars‐lines. Genetic distances obtained from RAPD data were correlated with estimated kinship coefficients. Within the RAPD or pedigree method, similar mean genetic distances were detected for long‐ and medium‐grain cultivars. However, mean genetic distances based on pedigrees were significantly greater than those based on RAPD data for both grains types. Cultivars with the same maturity group or grain type were generally placed together in cluster analyses based on either RAPD or known pedigree data. RAPD information can be used to establish genetic relationships among commercial U.S. rice cultivars with unknown or unrelated pedigrees.
A Cost Analysis of Maintaining Cassava Plant Genetic Resources
Authors: Epperson James E. , Pachico Douglas H. , Guevara Claudia L.
Published: July 2010

Costs represent a chief consideration as a major constraint to germplasm preservation. The objective of this study was to ascertain in detail the costs for cassava (Manihot esculenta Crantz) germplasm storage to identify potential areas for greater cost effectiveness. The cost analysis for this study encompassed the field and in vitro parts of the cassava collection at the Centro Internacional de Agricultura Tropical (CIAT), near Cali, Colombia. The isozyme laboratory costs used for genetic evaluation also were included in the analysis. The total cost of in vitro preservation of cassava germplasm at CIAT was about 53% more than that for field preservation. Variable costs (those that can vary within the year) were quite high for field preservation relative to that for in vitro preservation. Labor comprised a large part of the cost for both operations. Labor was considered part of the fixed cost (those that cannot be varied within the year) for in vitro preservation although it was a variable cost for field preservation. Skilled labor is required for the in vitro facility and cannot be varied in the short run without endangering the security of the collection. Further, since variable costs were quite high for field preservation, relative to that for in vitro preservation, greater cost savings can be achieved in the short run by reducing accessions and replications of accessions in the field where prudent. Use of the isozyme laboratory is cost effective if procedures allow the identification and elimination of duplicate accessions for both field and in vitro preservation of the collection.
Effect of Bermudagrass Height on Clover Establishment
Authors: Springer T. L.
Published: July 2010

Interseeding cool‐season forage legumes into bermudagrass [Cynodon dactylon (L.) Pers.] can extend the grazing season and increase forage quality. Common (cultivar unknown) and ‘Regal’ white clover (Trifolium repens L.) and ‘Dixie’ and ‘Tibbee’ crimson clover (T. incarnatum L.) were sown at 7000 pure live seed/plot into ‘Tifton‐ 44’ bermudagrass sod. The experimental design was a 4×4 Latin square with bermudagrass height (2, 7, 12, or 17 cm) as main plot treatments and legume cultivar as subplot treatments. There was a linear response in percentage legume ground cover with increasing bermudagrass heights. For every 5‐cm increase in bermudagrass height there was approximately a 2% reduction in ground cover for crimson clover and 10% for white clover. Crimson clover establishment (89%) was greater than white clover (51%), but stands of crimson quickly declined suggesting that it should be reseeded in years with excessive summer rainfall.
Soybean Mosaic Virus Incidence Level and Infection Time: Interaction Effects on Soybean
Authors: Ren Q. , Pfeiffer T. W. , Ghabrial S. A.
Published: July 2010

Soybean mosaic virus (SMV) infection can reduce soybean [Glycine max (L.) Merr.] yield and seed quality, but the magnitude of these reductions depends on several factors including the soybean developmental stage at infection and the incidence of infection. while most research has involved 100% infection at a defined growth stage, natural SMV infections are usually not 100% and occur at different times in different years. The objectives were to better define the relationship between incidence level and timing of infection and to determine the best approach for evaluating potential yield losses due to SMV infection. The effects of SMV on soybean seed yield and quality in relation to (i) the incidence level of SMV infection, (ii) the soybean growth stage at infection time, and (iii) the interaction between these were investigated using blends with different proportions of one pair of isolines, ‘Williams’ (susceptible to SMV) and L78‐379 (resistant to SMV). The effects of incidence level of SMV infection on yield, percentage of seed transmission and seed mottling were all linear in both early and late planting environments. A greater reduction in yield, and higher percentages of seed transmission and seed coat mottling resulted from infection of soybean by SMV at or before flowering compared to infection after flowering. When soybean plants were infected by SMV after flowering, negative effects were small or negligible. The interaction between incidence level of infection and inoculation stage was highly significant. When data from inoculation after flowering were dropped, the interaction between incidence of infection and inoculation stage was nonsignificant. Large's critical stage model is appropriate for the assessment of soybean yield losses due to SMV infection, and this critical stage is Growth stage R1.
Agronomic Performance of Related Durum Wheat (Triticum turgidum L.) Stocks Possessing the Chromosome Substitution T1BL.1RS
Authors: Villareal R. L. , Bañuelos O. , Mujeeb‐Kazi A.
Published: July 2010

Comparisons of bread wheat (Triticum aestivum L.) germplasms provided evidence that the T1BL.1RS chromosome substitution enhances agronomic performance and, particularly, grain yield. There are no known reports of the effect of this translocation in durum wheat (Triticum turgidum L.), however. The objective of this study was to determine the effect of the T1BL.1RS chromosome on grain yield, yield components, and other agronomic traits using 22 related durum lines (11 homozygous for chromosome 1B, and 11 homozygous for T1BL.1RS). The test lines were produced by substituting the T1BL.1RS chromosome in T. turgidum cultivar Altar 84 (1B, 1B) through backcrossing. Two field trials were evaluated under optimum (five irrigations) and reduced (one irrigation) moisture conditions at the Mexican National Institute of Forestry, Agriculture and Livestock, Campo Agricola Experimental Valle del Yaqui (CAEVY) Research Center, Sonora, Mexico, during the 1993–1994 and 1994–1995 crop production cycles. The results indicated that the T1BL.1RS genotypes have increased above‐ground biomass at maturity, increased 1000‐kernel weight, and increased test weight in both irrigation treatments. The T1BL.1RS lines also possessed longer spikes and headed and matured later. The 1B lines produced more kernels m−2 than the T1BL.1RS lines in all tests, however. The yield superiority and longer grainfilling period of the T1BL.1RS translocation group were detected only under reduced irrigation conditions. The average effect of T1BL.1RS across years and irrigation treatments was to increase grain yield and aerial biomass by 3.5 and 3.3%, respectively. The yield advantage was attributed to increased kernel weight, test weight, and spike length.
Relationship between Plant Composition and European Corn Borer Resistance in Three Maize Populations
Authors: Ostrander B. M. , Coors J. G.
Published: July 2010

Breeders have selected for European corn borer [Ostrinia nubilalis (Hubner)] (ECB) resistance for manyears and this may have led to higher concentrations of cell wall carbohydrates and lignin in stalks and leaf sheaths of maize (Zea mays L.). Our objectives were to evaluate the compositional changes accompanying divergent selection for cell wall constituents in three maize populations and to determine whether these changes were associated with changes in ECB resistance. Population BS9(CB) had undergone five cycles of S1 family selection for increased first‐ and second‐generation ECB resistance. Cycle 2 of BS9(CB) also underwent one cycle of divergent S1 selection for neutral detergent fiber (NDF) and lignin concentrations in the stalk and leaf sheath. Populations WFISILO and WFISIHI underwent two cycles of S1 family selection, respectively, for low and high NDF, acid detergent fiber (ADF), and lignin. Whorl samples were collected at the time of first‐generation infestation. Stalks, leaf sheaths, and leaf blades were sampled following second‐generation infestation. Selection for increased ECB resistance in BS9(CB) increased NDF, ADF, and lignin concentrations in stalks and leaf sheaths. Selection for high NDF and lignin concentrations in BS9(CB) C2 produced materials with greater second‐generation ECB resistance than did divergent selection for low concentrations. Selection for decreased NDF, ADF, and lignin in WFISILO decreased second‐generation ECB resistance. Selection for increased NDF, ADF, and lignin in WFISIHI did not influence ECB resistance, however. In general, there was an association between plant cell wall composition and ECB resistance, but genetic background influenced the relationship.
The Development of Self‐Pollinated Inbred Lines of Meadowfoam by Direct Selection in Open‐Pollinated Populations
Authors: Knapp Steven J. , Crane Jimmie M.
Published: July 2010

Limnanthes alba Benth. (meadowfoam) is an allogamous insectpollinated oilseed crop. Poor pollination and pollinator costs have purportedly limited the commercial production of this crop. Production costs can be reduced and seed yields might be increased by using self‐pollinated cultivars. Such cultivars have not been developed for this crop, however. Our objective was to develop self‐pollinated inbred lines by directly selecting for self‐pollination in open‐pollinated meadowfoam populations. A total of 520 S0 progeny from 26 L. alba accessions were screened for self‐pollination in the field under reduced pollinator loads. Sixteen L. alba var. versicolor S0 progeny produced seed in a high percentage of flowers, whereas the other 504 progeny produced seed in a small percentage of flowers. A total of 288 S0 progeny from six L. alba var. versicolor accessions were screened for seeds per plant in a pollinator‐free greenhouse. Forty‐nine of these progeny produced 5 to 48 seeds per plant by self‐pollination. S3 lines were developed by selecting for seeds per plant (in the absence of pollinators) among OMF‐63, OMF‐64, and OMF‐66 S0, S1, and S2 progeny using single‐seed descent. OMF‐63, OMF‐64, and OMF‐66 S3 and OMF‐64 S3 produced significantly more seeds per plant and seeds per flower by self‐pollination than Mermaid, an open‐pollinated L. alba var. alba cultivar. OMF‐63, OMF‐64, and OMF‐66 S3 produced 26.3 to 30.1 seeds per plant and 0.97 to 0.99 seeds per flower, whereas Mermaid produced 3.0 seeds per plant and 0.14 seeds per flower. OMF‐64 S5 lines produced 41.0 to 72.3 seeds per plant and 1.26 to 2.07 seeds per flower, whereas Mermaid produced 2.9 seeds per plant and 0.12 seeds per flower. These self‐pollinated inbred lines should be useful for developing elite self‐pollinated meadowfoam cultivars.
Nitrate Uptake, Efflux, and In Vivo Reduction by Pima and Acala Cotton Cultivars
Authors: Aslam M. , Nielson K. , Travis R. L. , Rains D. W.
Published: July 2010

Nutrient assimilation by seedlings is an early indicator of subsequent plant growth and development. This study was conducted to compare NO−3 assimilation (net uptake, efflux and in vivo reduction) by 8‐d‐old seedlings of three Pima (S‐7, Oro Bianco, Conquistador) (Gossypium barbadense L.) and four Acala (Maxxa, GC‐510, Royal, SJ‐2) (Gossypium hirstum L.) cotton cultivars. The seedlings were grown hydroponically in a growth chamber and induced with 0.05, 0.1, or 1.0 mM NO−3 for 24 h. Net NO−3 uptake rates were determined by following its depletion from uptake solutions that initially contained the same concentration of NO−3 as the induction solutions. Efflux was measured by following NO−3 accumulation in an external solution. At 0.05 mM NO−3, net uptake rates for the Acala cultivars were about 40% lower than those for Pima cultivars. These differences disappeared as the NO−3 concentration in the growth mediumw as increased to 1.0 mM. In contrast, efflux from Acala roots was 40 to 50% lower than that from Pima roots at all NO−3 levels. Although NO−3 concentration of roots increased about three fold as the NO−3 level in the induction mediumin creased, efflux increased only 20 to 30%. In vivo NO−3 reduction by Pima and Acala cultivars was similar when the seedlings were supplied with 1.0 mM NO−3. However, at 0.05 mM NO−3 the Pima cultivars reduced NO−3 more effectively than did the Acala cultivars. The results indicate that Pima cultivars are better able to utilize available NO−3 at lower concentrations even though they efflux greater amounts of NO−3.
White Clover Clone Response to Alternative Defoliation Methods
Authors: Brink G. E. , Rowe D. E.
Published: July 2010

While clover (Trifolium repens L.) is often evaluated under clipping during selection of germplasm but is ultimately utilized in grazed pastures. The objective of this study was to determine the effect of defoliation method on morphological characters that serve as selection criteria for improving white clover productivity and persistence. Vegetative clones of 14 plants of Southern Regional Virus Resistant germplasm were space‐planted in a common bermudagrass [Cynodon dactylon (L.) Pers.] sward in each of 2 yr on a Savannah fine sandy loam (fine‐loamy, siliceous, thermic Typic Fragiudnlt). Clones were defoliated the following year by continuous stocking with cattle or by clipping or rotational stocking on a monthly basis. Lateral plant spread of all clones increased from April to June, but declined from July to October due to death of stolon apices, and was reduced up to 50% by continuous stocking compared with clipping and rotational stocking. In July, plant leaf area, stolon length, and number of stolon apices of all clipped and rotationally‐stocked clones were twice that of continuously‐stocked clones. Morphological response to defoliation method in October, however, was genotype‐dependent; clones that exhibited superior growth in response to one defoliation method did not exhibit the same response to either of the other methods. The differential effect of defoliation method on white clover morphology demonstrates the sensitivity of these characters to harvest management, and because of their association with persistence, the need to evaluate germplasm in the environment in which it will be utilized.
Effects of Coating on Seed Imbibition: II. Effect of Coating Rates
Authors: Schneider Anne , Renualt Pierre
Published: July 2010

Coatings may slow water uptake by seeds. To analyze this effect, imbibition of coated and non‐coated maize (Zea mays L.) seeds was determined in gaseous and liquid phases. One coating material was applied at five different rates. Similar experiments were done with porous silica beads in saturated air. The volume and surface of the seeds and silica beads were either measured or calculated, and the thickness of the coating was measured. Water potential and wettability were estimated for the seeds, silica beads, and coating. The mechanical behavior of the coating was observed during imbibition. Data were compared with simulations by a simple model. When the seeds are soaked in a liquid medium, coating had no effect. In saturated air, coatings enhanced seed water uptake at low coating rates and slowed it at higher rates. When applied to silica beads, coating slowed imbibition at all rates of application. Thus, we distinguished between a positive effect which predominates at low coating rates for seeds (wetting or breaching effect of the surfactants on the pericarp wax) and a barrier effect to water uptake which increases with the coating rate. On seeds, these effects may be modified by the appearance of cracks in the coating, which resulted from seed swelling. Two independent estimates of the vapor diffusion properties of the coatings were deduced from experiments performed on seeds and silica beads and they differed by a factor of approximately 1.7. It seems therefore possible to determine coating transport properties with this model.
RFLP Mapping of Resistance to Southern Root‐Knot Nematode in Soybean
Authors: Tamulonis J. P. , Luzzi B. M. , Hussey R. S. , Parrott W. A. , Boerma H. R.
Published: July 2010

In the USA, the southern root‐knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] (Mi) is a serious pathogen soybean [Glycine max (L.) Merrill]. The objectives of this study were the following: (i) to use restriction fragment length polymorphism (RFLP) to identify markers associated with quantitative trait loci (QTL) conferring Mi resistance, (ii) to estimate the relative contribution to resistance of each QTL, and (iii) to locate each QTL on the molecular map of the soybean genome. PI96354, a plant introduction with a high level of resistance to Mi, was crossed with ‘Bossier’, a highly susceptible cultivar, and 110 F2 plants were produced and mapped with 121 RFLP markers. A greenhouse screening procedure was used to determine the level of galling for the F2:3 lines. Data were analyzed using single‐factor and two‐factor analysis of variance and interval mapping. Two QTL were identified which mapped to LG‐O and LG‐G of the USDA/ARS‐Iowa State Univ. (USDA/ARS‐ISU) soybean RFLP Map. Results showed a major resistance QTL (R2 = 31%) linked to marker G248A‐1 on LG‐O. The second QTL (R2 = 14%) was localted on LG‐G in the interval from K493H‐1 to Cs008D‐1 and was dominant with respect to resistance. The two QTL explained 39% of the variation in Mi galling in a multiple QTL model. Marker G248A‐1 may be closely linked to the Rmi1 gene. When galling data was classified into three distinct classes, it mapped distally to G248A‐1 on LG‐O. Mi resistance also was linked to G248A‐1 through simulated marker analysis. The root‐knot nematode resistance QTL identified were found in duplicated DNA segments.
Field Performances of Rice Somaclones at Low Temperature: Effects of Callus Chilling Treatment
Authors: Bertin P. , Busogoro J.‐P. , Tilquin J.‐P. , Kinet J.‐M. , Bouharmont J.
Published: July 2010

Chilling is one of the major constraints of rice (Oryza saliva L.) culture in cool environments. As an alternative to classical breeding, rice plants showing enhanced chilling tolerance in controlled environments were previously obtained from tissue culture. This study tested these plants in the field under a cool climate. Calli of four cultivars adapted to high altitude (‘Facagro 57’, ‘Facagro 76’, ‘Kirundo 3’, and ‘Kirundo 9’) were cultivated either at 4°C (during 2, 4, or 6 wk, continuously or not) or at 25°C. R0 plants (i.e., plants regenerated from calli) were then regenerated at 25°C and cultivated in a greenhouse. The R1 families (i.e., plants rising from a same R0 plant) and the original parental cultivars were cultivated at 1580 m in Burundi, East Africa, from 1991 to 1992. The R2 progenies of the best‐performing R1 families and parental plants were cultivated in the same conditions in 1993. For parameters concerning tillering capacity, maturity, and seed production, R2 families had lower means but higher variation (variation coefficients, minimum, and maximum values) than the parental plants. Differences appeared between callus chilling treatments. In the Kirundo cultivars, the longest chilling treatments led to the best performing families for most parameters, while no callus stress usually resulted in the lowest performances. In contrast, the best performing Facagro families usually arose from unstressed calli. Opportunity for in vitro selection may thus depend on the original genotype.
Agronomic and Grain Quality Evaluations of Triticum aestivum × Aegilops tauschii Backcross Populations
Authors: Murphy J. P. , Griffey C. A. , Finney P. L. , Leath S.
Published: July 2010

Aegilops tauschii Coss., a diploid progenitor of common wheat, Triticum aestivum L., is a valuable source of pest resistance alleles. However, interspecific populations generated for pest‐resistant germplasm development may contain beneficial alleles for other important traits. The objective of this research was to evaluate eight agronomic and grain quality traits in three soft red winter wheat × Ae. tauschii backcross populations. A total of 385 BC2F2‐derived lines were grown at locations in North Carolina and Virginia for two seasons. Grain quality evaluations were conducted at the USDA‐ARS Soft Wheat Quality Laboratory. Fifty‐four percent of lines did not differ significantly from their recurrent parent, averaged over all eight traits. In general, distributions were negatively skewed for grain yield and test weight and positively skewed for heading date, plant height, flour protein concentration, and alkaline water retention capacity. Line distributions for flour yield and softness equivalent were population dependent. Twenty‐three lines were significantly superior to their recurrent parent for one or more grain quality traits and similar to the recurrent parent for all remaining traits. Researchers who generate interspecific T. aestivum × Ae. tauschii populations for pest‐resistant germplasm development can identify lines with beneficial alleles governing other traits in an acceptable cultivated background if the progeny undergo additional screening.
Prediction of Maize Hybrid Silage Performance Using Marker Data: Comparison of Several Models for Specific Combining Ability
Authors: Charcosset A. , Bonnisseau B. , Touchebeuf O. , Burstin J. , Dubreuil P. , Barrière Y. , Gallais A. , Denis J.‐B.
Published: July 2010

Methods that could predict F1 maize (Zea mays L.) hybrid performance with some accuracy prior to field evaluation are of particular interest. This study was conducted to evaluate the efficiencies of the conventional additive model based on the general combining ability (GCA) as control and of three different predictions of the specific combining ability (SCA). The first approach was based on the hypothesis that the degree of SCA expressed by a single‐cross is related to the marker distance between its parental lines. The second approach was based on a factorial regression model of interaction, where markers were used by means of principal component analysis to generate covariates for SCA. The third approach was adapted from the best linear unbiased prediction (BLUP) of SCA, where covariances between hybrid SCAs were estimated with marker data. Efficiencies were evaluated by means of a cross‐validation procedure for silage performance of a 21 by 21 half‐diallel population among maize inbreds. This procedure was applied to (i) all hybrids and (ii) hybrids between unrelated parents only. In situation (i), introducing a distance term in the model accounted for up to 73.6% of the variation in the hybrid performance observed, whereas the corresponding efficiency of the GCA model was 63.4%. The introduction of a distance term did not modify prediction efficiency in situation (ii) whereas the use of the factorial regression model or the BLUP approach led to moderate improvements. These results suggested that efficient approaches can be proposed to predict hybrid silage yield and that prediction of SCA is mostly justified in situations where coancestry among inbreds is unknown or only suspected.
Growth Analysis of Crambe
Authors: Kmec P. , Weiss M. J. , Milbrath L. R. , Schatz B. G. , Hanzel J. , Hanson B. K. , Eriksmoen E. D.
Published: July 2010

Growth analysis of crambe (Crambe abyssinica Hochst. ex R. E. Fries) is important for the use of proper production practices and adequate pest management strategies. This study evaluated the heat unit requirements and quantitative characteristics of crambe growth [leaf area index (LAI), leaf area duration (LAD), yield, and total biomass] and the impact of defoliation on yield using artificial infestation with diamondback moth (Plutella xylostella L.) (DBM) in 1993and 1994 and manual defoliation in 1995. The heat unit accumulation from planting to physiological maturity was approximately 1350 degree‐days (DD) above 2.5 °C. The maximum LAI and generally the maximum daily increase of biomass occurred at the onset of flowering. The yield was proportional to LAD: 238 g m−2 versus 1187 DD in 1993, 190 g m−2 versus 1010 DD in 1994, and 117 g m−2 versus 774 DD in 1995. No reduction in yield or thousand seed weight was observed in any of the infestation or defoliation experiments. The artificial defoliation experiment showed that crambe can withstand substantial injury after the start of anthesis (25–50% of leaf area lost) without a significant yield loss.
Influence of Ozone Stress on Soybean Response to Carbon Dioxide Enrichment: II. Biomass and Development
Authors: Miller J. E. , Heagle A. S. , Pursley W. A.
Published: July 2010

Previous research has shown that elevated CO2 concentrations can increase plant growth, whereas the air pollutant O3 is phytotoxic. Because elevated concentrations of these gases will co‐occur, the objective of our experiment was to determine if estimates of plant growth response to future levels of CO2 and O3 require experiments to test the gases in combination. Soybean plants [Glycine max (L.) Merr. cv. Essex) were exposed in open‐top chambers to combinations of O3 and CO2 from plant emergence through physiological maturity. Ozone treatments were charcoal‐filtered air (CF), nonfiltered air (NF), and NF with O3 added for 12 d−1 (NF+) (seasonal mean 12 d−1 O3 concentrations of 20, 50, or 79 nL L−1, respectively). Carbon dioxide exposures were for 24 h d−1 giving seasonal mean 12 d−1 concentrations of 370, 482, 599, or 713 μL L−1. Over the season, elevated CO2 usually stimulated growth and O3 suppressed growth. Elevated CO2 usually increased partitioning of biomass to branches, decreased partitioning to pods, increased specific leaf weight, and decreased leaf area ratio. Ozone suppressed leaf and root weight ratios, increased pod weight ratios, and decreased specific leaf weight. Toward the end of the season, both O3 and CO2 accelerated reproductive development. Elevated CO2 moderated suppression of growth by O3, and the highest CO2 concentration completely ameliorated O3 effects on main stem biomass, root biomass, and leaf area. Ozone, however, limited some positive growth responses to CO2, especially at less than a doubling of CO2 concentrations. These results indicate that in order to understand the future impacts of atmospheric gases such as elevated CO2 and O3 on crop growth, their combined effects should be determined.
Bermudagrass Growth, Total Nonstructural Carbohydrate Concentration, and Quality as Influenced by Nitrogen and Potassium
Authors: Trenholm L. E. , Dudeck A. E. , Sartain J. B. , Cisar J. L.
Published: July 2010

Hybrid bermudagrass cultivars (Cynodon dactylon L. × C. transvaalensis Burtt‐Davy) ditfer in their responses to N and K for growth, total nonstructural carbohydrate (TNC) concentration, and turf quality scores. This 1995 research was conducted in Florida to compare responses of two bermudagrass cultivars to N and K under long‐day (>13 h) and short‐day (<13 h) conditions in a glasshouse. Evaluations were made concerning shoot and root growth, TNC concentration, and quality scores of ‘FloraDwarf’ and ‘Tifdwarf’ bermudagrass during establishment in a coarse sand medium. Experimental design under each photoperiod was a randomized complete block with factorial treatments consisting of two cultivars, four rates of N, four rates of K, and four replications. Data were analyzed by fitting multiple regression equations starting with a second order polynomial model. Growth of FloraDwarf was highly responsive to photoperiod, in that decreased daylengths reduced growth. No growth differences were found in Tifdwarf due to daylength. Growth increased in response to N in both cultivars, while growth response to K varied by cultivar. Both cultivars accumulated higher levels of TNC under short day conditions, with higher levels in FloraDwarf. Nitrogen fertilization reduced TNC levels in FloraDwarf under short days and in Tifdwarf under long days, while K fertilization reduced TNC levels in Tifdwarf under short days. Quality scores in both cultivars increased in response to N under long days, and in response to both N and K under short days. Results of these studies indicated that growth, TNC accumulation, and quality differed due to cultivar, photoperiod, and rates of N and K.
Cultural and Chemical Controls of Thatch and Their Influence on Rootzone Nutrients in a Bentgrass Green
Authors: Callahan Lloyd M. , Sanders William L. , Parham John M. , Harper Cynthia A. , Lester Lori D. , McDonald Ellen R.
Published: July 2010

Thatch accumulation is a serious problem in densely grown turfgrass maintained under low mowing heights. Opinions differ concerning effectiveness of cultural and chemical controls of thatch. The objectives of these studies were to determine the effectiveness of mechanical and chemical treatments in controlling thatch and their influence on soil nutrient retention and pH in a creeping bentgrass (Agrostis palustris Huds.) green growing on a U.S. Golf Association (USGA) rootzone. Thatch control treatments were vertical mowing (VM 4 and 8×/yr), coring (core 4×/yr), wetting agent (Wet Ag 7×/ yr), extra K (4×/yr), lime (L 4×/yr) and various combinations, and interactions of these with topdressing (Tpd 3 and 6×/yr). Rootzone nutrients determined were Ca, K, and P and rootzone pH levels were determined. Thatch measurements were determined with a rapid surface sod compression instrument termed the Thatchmeter II. Treatments and measurements were conducted for 6 yr with results reported for the last 3 yr. Lowest non‐significant levels of thatch resulted following VM 4× or 8×/yr and VM + coring. Tpd 3× or 6×/yr also effectively prevented thatch buildup. When combining mechanical and chemical methods with Tpd, lowest non‐significant levels of thatch resulted following VM 4× or 8×/yr, VM + coring, and VM + L, all combined with Tpd 6×/yr. Extra K (VM + K + L, K + L, K) and Wet Ag resulted in increased thatch. Lime did not influence thatch depth. Loss of rootzone K was 94% and increased with mechanical and chemical treatments. Loss of rootzone P was 86% but extra K and L treatments reduced P loss, especially under pH 7.3 following L treatments. Loss of rootzone Ca was 56% but L and extra K treatments under pH 7.3 reduced this loss.
Response of Nonirrigated Maturity Group V Determinate Soybean to End‐Trimming
Authors: Heatherly Larry G. , Tyler Jeffrey. M.
Published: July 2010

Obtaining accurate seed yield information from soybean[Glycine max (L.) Merr.] field research environments and concurrently conserving valuable field space is desirable. The purpose of this study was to determine the effect of plot length and alley width on the response of short‐ and tall‐statured Maturity Group(MG) V soybean cultivars to end‐trimming after maturity. Experiments were conducted in 1995 and 1996 at the Delta Research and Extension Center at Stoneville, MS, (lat.33°26′). ‘Hutcheson’ (relatively shorts stature) and ‘DP3 3589’ in 1995 and ‘DP 3588’ in 1996 (both relatively tall stature) were planted on 9 May 1995 and 15 May 1996 Treatments were plot length (6.10 or 15.25m ), alley width (0.90 or 2.45m ), and end‐trim length (0, 0.45, or 0.90m ). Average height of Hutcheson at maturity was 52 cm in 1995 and 55 cm in 1996, while average height of DP 3589 in 1995 and DP 3588 in 1996 was 88 cm. All cultivars responded similarly in yield to all factors in this experiment. End‐trim length was the only factor that significantly affected average yields. Not end‐trimming resulted in an average yields of 2573k g ha−1, while end‐trimming either 0.45 or 0.90 m resulted in average yields that were nearly identical (2356 and 2 337k g ha−1, respectively). Contrary to our hypothesis, increasing plot length from 6.10 to 15.25m and decreasing alley width from 2.45 to 0.90 m did not negate the end‐of‐plot effect on yield of soybean grown in nonirrigated field plots. These results indicate that soybean grown in plots with row lengths and alley widths that are within the confines of the dimensions used in our experiment should be end‐trimmed to eliminate end‐of‐plot effects. Also, field space can be conserved by using the 6.1‐m plot length and the 0.90‐m alley width.
Historical Changes in Harvest Index and Crop Nitrogen Accumulation
Authors: Sinclair Thomas R.
Published: July 2010

Plant harvest index, the ratio of grain weight to total plant weight, is an important trait associated with the dramatic increases in crop yields that have occurred in the twentieth century. Harvest index reflects the partitioning of photosynthate between the grain and the vegetative plant and improvements in harvest index emphasize the importance of carbon allocation in grain production. The objective of this review is to examine from an historical perspective some of the changes that have occurred in crop harvest index and to consider the importance of crop nitrogen accumulations asociated with changing this trait. In modern times, harvest index has generally increased. Priort o the twentieth century,t here is evidencet hat plants elections also resulted in changes in harvest index. One factor that may have influenced these changes was the relative value of grain, compared with straw. Historically, straw production was a high priority, making low harvest index a desirable trait. Another factor wast he level of nitrogena vailabilef or the productionof highg rain yields. Accumulation of high levels of nitrogen is essential for high grain yields, and thus, high levels of nitrogen are commonly associated with crops having high harvest indices. Under conditions where nitrogen is limiting, a low harvest index crop is advantageous. Limited nitrogen can be partitioned into the low nitrogen concentration vegetative tissue, which results in high total production of plant mass. However, increasing grain yield and crop harvest index with high nitrogen grain requires a concomitant increase in crop nitrogen accumulation.
Genetic Control of Insect Resistance in Soybeavvvvn Germplasm PI 417061
Authors: Kilen T. C. , Lambert L.
Published: July 2010

Soybean [Glycine max (L.) Merr.] germplasm lines PI 171451, 227687, and PI 229358 have been reported to be resistant to several insect species. Further studies suggest that each line carries at least one gene for resistance that is different from the other sources. A later introduction, PI 417061, has also been reported to be resistant to several insect species. The genetic relationship of PI 417061 and the other three germplasm lines is unknown. The objective of this study was to determine if the genes for resistance in PI 417061 are different from those in PI 171451, PI 227687, and PI 229358. Parents and F3 lines from crosses between PI 417061 and the other three resistant lines were rated visually for feeding damage by soybean looper (Pseudoplusia includens Walker) in a greenhouse or field cage. F3 lines from crosses PI 417061 ✕ ‘Davis’ and PI 417061 ✕ ‘Sharkey’ were also evaluated in a field cage. In previous studies, the cultivars Davis and Sharkey have been very susceptible to foliar feeding insects. In these two crosses, the distribution of F3 lines for leaf feeding ratings was continuous, but skewed toward the susceptible parent. This suggests the insect resistance of PI 417061 is controlled by multiple genes, similar to that found in the other three germplasm lines. Ratings of F3 lines from resistant ✕ resistant crosses suggest that genetic control of resistance to soybean looper in PI 417061 is different from that found in PI 171451 and PI 227687, but that the major genes for resistance in PI 417061 are probably the same as those found in PI 229358.
Genetic Progress in Reducing Losses to Leaf Rust in CIMMYT‐Derived Mexican Spring Wheat Cultivars
Authors: Sayre K. D. , Singh R. P. , Huerta‐Espino J. , Rajaram S.
Published: July 2010

Leaf rust, caused by Puccinia recondita Roberge ex Desmaz., is an important disease of wheat (Triticum aestivum L.) worldwide. To estimate the genetic progress in reducing grain yield losses through breeding for resistance to leaf rust, replicated trials including 15 popular CIMMYT germplasm‐derived wheat cultivars released between 1966 and 1988 in northwestern Mexico were sown in that same area; normal and late planting dates were used for four and two seasons, respectively. Leaf rust epidemics were established by inoculating spreader rows planted adjacent to plots of the cultivars which were not protected by fungicide. Average losses in grain yields of the cultivars due to leaf rust ranged between 6.6 and 62.7% and were highly correlated with final disease severity (r = 0.898, P < 0.01) and relative area under the disease progress curve (r = 0.917, P < 0.01). The losses in grain yield were mostly due to reductions in kernel weight, kernels per square meter, and grain fill rate. Grain yield losses (7.7–10.4%) in slow rusting cultivars Cocoraque 75, Nacozari 76, Opata 85, and Bacanora 88 were similar to those observed in the immune ‘Oasis 86’ (6.6%) or resistant ‘Ciano 79’ (10.2%). The average annual progress in grain yield potential achieved through breeding averaged over the six trials was estimated to be 0.48% (r2 = 0.38, P < 0.01) for fungicide protected and 2.21% (r2 = 0.47, P < 0.01) when not protected by fungicide. We conclude that while the grain yield potential of CIMMYT‐derived cultivars has increased significantly over the years, progress in protecting this yield potential through the incorporation of genes that confer slow rusting resistance has been more dramatic.
Relationship between Soybean Sudden Death Syndrome Disease Measures and Yield Components in F6‐Derived Lines
Authors: Njiti V. N. , Shenaut M. A. , Suttner R. J. , Schmidt M. E. , Gibson P. T.
Published: July 2010

Soybean [Glycine max (L.) Merr.] sudden death syndrome (SDS), caused by Fusarium solani (Mart.) Sacc. f. sp. glycines Roy can cause substantial yield loss. To determine the relationship between SDS and yield components, 16 F6‐derived lines from the cross ‘Pyramid’ ✕ ‘Douglas’ were tested in two southern Illinois locations (Cora and Ridgway) with natural infestation by the SDS pathogen. Plots were rated for disease incidence (DI), disease severity (DS), and reproductive development stage (R). DI and DS were standardized to R6. Disease index (DX) was calculated as DI×DS/9. Individual plant data collected on three plants per plot were DS, total flowers, total pods at R5.5 (mid‐pod‐fill) and R8, total empty and partially filled pods at R8, total seeds, seeds per pod, seed weight per plant, and 100‐seed weight. Seed quality was rated only at Ridgway. The among genotypes (genetic) covariance and the within genotype (environmental) covariance detected significant reductions in yield per unit of DS and DX (whole plot data). The genetic covariance with individual plant DS detected a significant reduction per unit of DS in total seed weight per plant. The environmental covariance with DS detected significant reductions in all yield components except flowers, empty pods, and seed per pod. There was a significant correlation of G✕E effects of most yield components and DS. Generally, genetic and environmental covariances were similar in magnitude and direction, suggesting that test genotypes were similar in the components affected and the degree of yield loss associated with a given level of disease.