bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Water Use by Diploid and Tetraploid Russian Wildrye
Authors: Frank A. B. , Berdahl J. D.
Published: July 2010

Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski] is an important cool‐season forage grass for the Northern Great Plains, but it exhibits poor seedling vigor. Tetraploid (2n=4x=28) plants have improved seedling vigor over diploid (2n=2x=14) plants, but data is lacking on plant‐soil‐water relations. Objectives of this research were to compare water‐use efficiency (WUE), evapotranspiration (ET), roofing activity, and water extraction in relation to Haun stage for diploid and tetraploid Russian wildrye. A diploid and tetraploid entry were evaluated for 3 yr under two water treatments (50 and 150% of monthly average precipitation for 1 April to 1 November) and two fertilizer rates (10 and 134 kg N ha−1) in a rain shelter. The soil was a Parshall fine sandy loam (Coarse‐loamy, mixed, superactive, frigid Pachic Haplustoll). Cumulative ET averaged across the 50 and 150% water treatments was 138 and 141 mm for the diploid and tetraploid, respectively. Rate of root activity progression was linear with Haun to the 1.2‐m depth and ranged from 0.148 to 0.163 m per Haun stage for the diploid and tetraploid, respectively, at 50% water. Forage yield of the tetraploid was greater than the diploid at the 50%, but not at the 150% water treatment. Water‐use efficiency was higher for the tetraploid (3.8 g kg−1) than the diploid (3.1 g kg−1) at the 50% water treatment, but at 150% water the entries were not different. Overall, the tetraploid entry exhibited a more favorable WUE and other soil water relations than did the diploid entry.
Leafy Reduced‐Stature Maize Hybrids for Short‐Season Environments
Authors: Dijak M. , Modarres A. M. , Hamilton R. I. , Dwyer L. M. , Stewart D. W. , Mather D. E. , Smith D. L.
Published: July 2010

Development of maize (Zea mays L.) types that produce leaf area quickly and mature rapidly may increase maize yields in mid‐ to shortseason areas. The leafy (Lfy1) and reduced‐stature (rd1) traits each contribute to this objective; however, these two traits have not previously been combined. Our objective was to determine the effect of these traits, alone or in combination, on morphology, reproductive development, and yield of maize hybrids. A field experiment including 14 hybrids [two non‐leafy reduced‐stature (NLRS), four leafy reduced‐ stature (LRS), eight leafy normal‐stature (LNS)], and three commercial hybrid checks [non‐leafy normal‐stature (NLNS)] was conducted in 1992 and 1993. The following variables were recorded for each hybrid: plant height, internode length, ear height, above‐ear leaf number, above‐ear leaf area, corn heat units from planting to tasseling, corn heat units from planting to silking, days from tasseling to silking, grain yield (Mg ha−1), grain moisture content, husk dry weight, husk moisture content, cob dry weight, cob moisture content, kernel number per row, maximum ear circumference, and ear length. The normal stature hybrids were the tallest plants, with higher ear placement than reduced stature hybrids. The leafy trait was associated with shorter internodes, increased leaf number, and greater above‐ear leaf area. The reduced stature hybrids required fewer corn heat units to reach anthesis than the normal stature hybrids. The reduced stature hybrids had the lowest grain moisture (210‐270 g kg−1), husk moisture, and cob moisture contents at the time of harvesting. The LNS hybrids matured late and had grain moisture contents of 350 to 400 g kg−1 at harvest. In general grain yield, husk dry weight, cob dry weight, kernel number per row, ear length, and maximum ear circumference were higher for the normal stature hybrids than for the reduced stature hybrids. The earlier anthesis and lower grain, husk, and cob moisture contents indicated potential for successful grain production and harvest of leafy reduced‐stature hybrids in shorter growing season areas.
Application of the Normal Distribution for Testing the Potential of the Controlled Deterioration Test
Authors: Kruse M.
Published: July 2010

The idea of vigor testing by the controlled deterioration test is usually illustrated by nonlinear courses of germination loss during the aging period. The aim of this analysis was to estimate the discrimination power of the controlled deterioration test by applying the assumptions about the nonlinear course made for establishing the Ellis and Roberts seed viability equation. The calculations showed that during the aging period, the differences in germination between seed lots increase according to the assumed normal distribution, while the sampling error of the germination test increases according to the binomial distribution. A gain of discrimination power was achieved when initial germination was higher than 50% and the duration of the aging period was optimized to achieve an average germination after the aging period of 50%. Experimental errors of the aging tests impair the discrimination power, whereas deviations from the assumptions made for the seed viability equation show the potential to improve the discrimination power.
Assesing the Abundance and Polymorphism of Simple Sequence Repeats in Perennial Ryegrass
Authors: Kubik Christine , Meyer William A. , Gaut Brandon S.
Published: July 2010

Simple sequence repeats (SSRs) have proven to be useful genetic markers in a wide variety of plants, but have yet to be widely applied to turfgrasses. Here we describe a study of SSRs in perennial ryegrass (Lolium perenne L.). A library of perennial ryegrass genomic DNA was screened with (GA). and (GT). probes, and SSR‐containing clones were isolated and sequenced. On the basis of this screen, we estimated that there are roughly 5800 (GA)n, and (GT)n. SSRs in haploid perennial ryegrass genome. Polymerase chain reaction (PCR) primers were designed to amplify the isolated SSRs, and six polymorphic $SRs were identified. Polymorphism in the these six SSRs was sufficient to discriminate among 18 individuals representing I1 perennial ryegrass clones and seven other Lolium species. Half‐sibs could be distinguished with data from as few as three SSRs. The SSR genotype data was also used to infer genetic relationships among the individuals of our sample. The relationships were in broad agreement with those established by previous analyses, suggesting that SSR data will be usefni for exploring relationships among perennial ryegrass cultivars. In total, this study indicates that SSRs are sufficiently abundant and sufficiently polymorphic to be useful genetic markers in perennial ryegrass.
A Novel Means of Analyzing the Soluble Acidity of Rice Grains
Authors: Lii Lai‐Jiu , Wang Chang‐Ying , Lur Huu‐Sheng
Published: July 2010

Soluble acidity has been used as one of major indexes to reflect the changes of rice (Oryza sativa L.) grain quality during storage. The acidity is in general visually examined by pH dye indicators or directly measured by a pH meter. By combining the characteristics of pH dye indicator, 96‐well microplate, and microplate reader, we have developed a procedure capable of effectively measuring the pH value of rice grains at a single‐grain level. First, from a pH‐dye system prepared with methyl red and bromothymol blue, we scanned the spectral response to pH and determined that a wavelength of 630 nm showed the maximum response to pH changes with storage age of rice grains. By means of a 96‐well microplate and plate reader, a pH standard curve was then constructed with a series of pH standard buffers and absorbance at 630 nm. The pH value of a single grain in a microplate well can be measured by incubating the grain with dye solution and reading absorbance. The proposed procedure offers an efficient means of measuring the change of soluble acidity in rice grains during storage on an individual‐grain basis. The method may also rapidly detect the uniformity or blending status of fresh/old grains in a sample.
Digestibility Analysis of Undried, Unground, and Dry Ground Herbage by Near‐Infrared Reflectance Spectroscopy
Authors: Griggs T. C. , Lobos K. B. , Kingery P. E.
Published: July 2010

Analysis of herbage quality by near‐infrared reflectance spectroscopy (NIRS) usually involves dry ground samples. Costs might be reduced if samples could be analyzed without drying and grinding. Our objective was to test influences of herbage processing treatments on NIRS analytical accuracy. In Exp. 1, grass and legume samples were scanned in fresh or thawed coarse (unground) condition, then fresh subsamples were dried and scanned before and after grinding. In Exp. 2 samples were dried or frozen and thawed, then scanned in coarse condition. Dried samples were then ground and rescanned. In vitro dry matter digestibility (IVDMD) was determined in both experiments for ground samples that were dried without freezing, and in Exp. 2 for samples that were frozen and thawed before drying and grinding. Freezing and thawing reduced digestibility by 7 g kg−1 for grasses and 33 g kg−1 for legumes, but the reduction was inconsistent among grass species. Calibrations were developed for pooled and separate grass and legume populations. Analytical accuracy, represented by standard error of cross‐validation (SECV), was similar among grass treatments (SECV ≥ 27 g kg−1), but was higher for dry ground (SECV ≥ 16 g kg−1) than for coarse (SECV ≥ 21 g kg−1) treatments within legume and pooled populations. Coarse samples require less processing, but more replicate scans for spectral repeatability, than dry ground samples. Coarse sample analysis may be acceptable when processing is costly, rapid analyses are required, or when possible compositional alterations due to freezing or drying should be avoided.
Loci Controlling Resistance to High Plains Virus and Wheat Streak Mosaic Virus in a B73 × Mo17 Population of Maize
Authors: Marçcon A. , Kaeppler S. M. , Jensen S. G. , Senior L. , Stuber C.
Published: July 2010

High Plains disease has the potential to cause significant yield loss in susceptible corn (Zea mays L.) and wheat (Triticum aestivum L.) genotypes, especially in the central and western USA. The primary causal agent, High Plains virus (HPV), is vectored by wheat curl mite (WCM; Aceria tossicheila Keifer), which is also the vector of wheat streak mosaic virus (WSMV). In general, the two diseases occur together as a mixed infection in the field. The objective of this research was to characterize the inheritance of HPV and WSMV resistance using B73 (resistant to HPV and WSMV) × Mo17 (moderately susceptible to HPV and WSMV) recombinant inbred lines. A population of 129 recombinant inbred lines scored for 167 molecular markers was used to evaluate resistance to WSMV and to a mixed infection of WSMV and HPV. Loci conferring resistance to systemic movement of WSMV in plants mapped to chromosomes 3, 6, and 10, consistent with the map position of wsm2, wsm1, and wsm3, respectively. Major genes for resistance to systemic spread of HPV in doubly infected plants mapped to chromosomes 3 and 6, coincident or tightly linked with the WSMV resistance loci. Analysis of doubly infected plants revealed that chromosome 6 had a major effect on HPV resistance, consistent with our previous analysis of B73 × W64A and B73 × Wf9 populations. Quantitative trait loci (QTL) affecting resistance to localized symptom development mapped to chromosomes 4 (umc66), 5 (bnl5.40), and 6 (umc85), and accounted for 24% of the phenotypic variation. Localized symptoms may reflect the amount of mite feeding or the extent of virus spread at the point of infection. Identification of cosegregating markers may facilitate selection for HPV and WSMV resistance in corn breeding programs.
Ploidy Determination of Alfalfa Germplasm Accessions Using Flow Cytometry
Authors: Brummer E. Charles , Cazcarro Patricia M. , Luth Diane
Published: July 2010

Determining the ploidy of germplasm is necessary before initiating breeding or genetic studies. This study was conducted to determine the ploidy of 263 accessions of Medicago sativa subsp. falcata Arcengeli and 20 accessions of M. sativa subsp. sativa (L.) L. & L. acquired from the USD A National Plant Germplasm System (NPGS). Ploidy was assessed using both flow cytometry and root tip chromosome counts. Approximately 68% of the subsp. falcata accessions were tetraploid and 32% were diploid. In all cases where ploidy determinations by root tip chromosome counting and flow cytometry differed, reanalysis of root tips from a new set of plants indicated the first counts were incorrect. The distribution of the accessions indicated that few diploids are available through the NPGS from the eastern range of the species distribution (Kazahkstan, Mongolia, China, and eastern Russia). Flower color variants were identified in many subsp. falcata accessions. Three of 20 subsp. sativa accessions were diploid, indicating they should be reclassified as M. sativa subsp. coerulea Schmalh. Flow cytometry allowed faster and more accurate ploidy determination than root tip chromosome counting. Ploidy determination will allow researchers to more accurately identify and request germplasm suited to their project.
Genetic Redundancy and Diversity among ‘Orange’ Accessions in the U.S. National Sorghum Collection as Assessed with Simple Sequence Repeat (SSR) Markers
Authors: Dean R. E. , Dahlberg J. A. , Hopkins M. S. , Mitchell S. E. , Kresovich S.
Published: July 2010

Plant genetic resources conservation is a challenge based on the need to balance acquisition priorities with the constrained level of financial support that is dedicated to long‐term maintenance of collections. As such, understanding how variation is partitioned among accessions is essential for effective management. It is generally recognized that most large collections exhibit varying levels of genetic redundancy. To address this issue, all of the sorghum [Sorghum color (L.) Moench] accessions identified as ‘Orange’ presently maintained by the U.S. National Plant Germplasm System (NPGS) were assayed with 15 simple sequence repeat (SSR) markers. Genotyping was performed with fluorescent primers with five primer sets in each of three multiplex polymerase chain reactions (PCRs) and automated allele sizing. A total of 96 individuals were analyzed, five plants from each of 19 Orange accessions and one individual from an elite inbred line, ‘RTx430’. The SSR markers provided substantial genetic resolution among the Orange entries. Average heterozygosity estimates were low, and phenetic analyses (neighbor‐joining dendograms) were generally consistent with known historical relationships among accessions. Most accessions were genetically distinct, but two redundant groups (involving a total of five entries) were found among the 19 Orange accessions evaluated. The molecular variance analysis (AMOVA) showed that 90% of the total genetic variation was partitioned among accessions, while one‐tenth of the variation resulted from genetic differences between individual plants within accessions. The variance analysis also indicated that it should be possible to reduce the number of Orange accessions held by NPGS by almost half without seriously jeopardizing the overall amount of genetic variation contained in these holdings. This study demonstrated that a limited number of $SR markers can be used in a cost‐efficient manner to rapidly assess variation in accessions of Orange sorghum.
Isozyme Diversity in Bambara Groundnut
Authors: Pasquet Rémy S. , Schwedes Sonya , Gepts Paul
Published: July 2010

Bambara groundnut [Vigna subterranea (L.) Verde.] is an important crop in many countries of tropical Africa. Compared with other leguminous crops, little is known about the organization of its genetic diversity. Our goal was to investigate its population structure and the partitioning of genetic diversity between domesticated and wild accessions. Seventy‐nine accessions of domesticated and 21 wild Bambara groundnut populations were evaluated for genetic diversity at 41 isozyme loci, representing 23 enzyme systems. Domesticated accessions were characterized by very low genetic diversity (Ht = 0.052) with only 7 polymorphic loci. Wild populations were characterized by higher genetic diversity (Ht = 0.087), with 14 polymorphic. This suggests a marked bottleneck between wild and domesticated forms. Intrapopulation diversity was comparatively high (Hs = 0.033 for domesticated and Hs = 0.025 for wild populations) despite the near absence of heterozygous individuals, which suggests a predominantly selfing mode of pollination in both wild and domesticated Bambara groundnut High genetic identity between wild and domesticated forms suggests that wild Bambara groundnut is the true progenitor of domesticated Bambara groundnut. Both morphological and isozyme data show a gradient between true wild and domesticated Bambara groundnut through weedy populations. The improved understanding of the organization of genetic diversity of Bambara groundnut provided by our data will allow a better conservation of its genetic resources.
A Method for the Efficient Management and Utilization of Large Germplasm Collections
Authors: Skinner D. Z. , Bauchan G. R. , Auricht G. , Hughes S.
Published: July 2010

To make efficient use of large germplasm collections, it is advisable to assemble a representative core collection and to evaluate the relationships among the traits studied. However, the assemblage of a core collection from very large germplasm collections is problematic. The computing resources needed to carry out genetic distance calculations and comparisons with commonly available programs is prohibitively large. The objects of this study were (i) to develop a method which assembles a core collection by maximizing the diversity (measured as mean Euclidean distance) from within groups of accessions defined by species, subspecies, and geographic origin and (ii) to test the effectiveness of the method on a collection of 20 997 annual Medicago accessions from the Australian Medicago Resource Center in Adelaide, South Australia, that had been evaluated for 27 agronomic characteristics. The method resulted in a core collection of 1705 accessions that represented 74% of the extremes of the 27 characters, indicating that the entire range of the characters was represented in most cases. Accessions representing the extremes easily could be added to the core collection. The method used requires relatively minor computing resources and should be useful to curators of large germplasm collections. To assess the relationships among the 27 measured traits, correlation coefficients of all possible combinations of traits were calculated. The most strongly associated traits were, as expected, such traits as grams of seed per plant and grams of pods per plant and indicated that some traits could be omitted from future evaluations with little loss of information, thereby increasing the efficiency with which germplasm evaluations can be carried out.
Discovery and Characterization of Polymorphic Simple Sequence Repeats (SSRs) in Peanut
Authors: Hopkins M. S. , Casa A. M. , Wang T. , Mitchell S. E. , Dean R. E. , Kochert G. D. , Kresovich S.
Published: July 2010

Cultivated peanut (Arachis hypogaea L), an important agronomic crop, exhibits a considerable amount of variability for morphological traits and for resistance to diseases and pests. In contrast, molecular marker assays have detected little variation at the nucleic acid level. Identification of molecular markers would be of great help to peanut breeders, geneticists, and taxonomists. The objectives of this work were to identify simple sequence repeat (SSR) markers in cultivated peanut and to test these markers for their ability to discriminate among accessions. Peanut total genomic DNA libraries were constructed and screened with 32P‐labeled dinucleotide repeats, (GT)10 and (CT)10. DNA sequences were obtained from the SSR‐containing clones and, when possible, primer pairs were designed on the basis of DNA sequences flanking the repeat motif. Primer pairs were tested in polymerase chain reaction (PCR) assays using a collection of 22 peanut DNAs, representing both cultivated peanut and wild species. In all, six SSR markers, five from the library screening procedure and one additional marker obtained from a search of publicly available DNA sequences, detected polymorphisms among the peanut DNAs. Discrimination power was high among the cultivated peanuts, with 17 unique genotypes represented among the 19 accessions tested. From two to 14 DNA fragments were amplified per SSR marker, and as a group, the six markers may amplify up to 10 putive SSR loci. The SSR markers identified in this study were more effective in detecting molecular variation in cultivated peanut than all other DNA‐based markers evaluated to date.
Associations among Forage Quality Traits, Vigor, and Disease Resistance in Alfalfa
Authors: Fonseca C.E.L. , Viands D.R. , Hansen J.L. , Pell A.N.
Published: July 2010

Major objectives for alfalfa (Medicago sativa L.) breeding include improving forage quality and levels of disease resistance. Little is known about the associations between forage quality characteristics, including pectin (the main component of neutral detergent‐soluble fiber [NDSF]), and disease resistance and vigor in alfalfa. Our objectives were to determine, in two alfalfa populations, the (i) correlations among NDSF and other forage quality traits; (ii) correlations of forage quality traits with plant persistence, vigor, and levels of resistance to diseases; and (iii) heritabilities and expected gains from selection for the aforementioned traits. Simple, phenotypic, and additive genetic correlation coefficients were estimated from half‐sib (HS) progeny tests of two alfalfa populations (NY9505 and NY9515). In both populations, NDSF was negatively correlated with acid detergent fiber (ADF), lignin, and neutral detergent fiber (NDF), and positively correlated with true in vitro dry matter digestibility (IVDMD). Vigor was positively correlated with ADF, lignin, and NDF, and negatively correlated with IVDMD and crude protein (CP) only in NY9515. Of 144 correlation coefficients computed between forage quality traits and resistances to five major alfalfa diseases, only six were significant, and they were low in magnitude (−0.22 ± 0.11 to 0.30 ± 0.14). In an alfalfa improvement program, selection for forage quality is not expected to indirectly affect levels of disease resistance, but it may reduce vigor.
Donor Inbred Lines for Enhancing the Performance of Single‐Cross Sunflower Hybrids
Authors: Cheres Mercy T. , Miller Jerry F. , Knapp Steven J.
Published: July 2010

The performance of single‐cross hybrids can only be enhanced by adding favorable alleles from donor inbred lines that are not present in either parent. The public inbred lines of cultivated sunflower (Helianthus annuus L.) have not been systematically screened as a source of new favorable alleles for enhancing hybrid performance. The objective of this study was to assess the merits of a sample of public inbred lines as donors of alleles for increasing the seed yield of three hybrids (HA383 × RHA373, HA372 × RHA377, and HA89 × RHA373). The net gain of favorable alleles and several other statistics were estimated from the seed yield means of 14 sterility maintainer (B) lines, four fertility restorer (R) lines, 81 B × B hybrids, and 42 B × R hybrids in field tests at Corvallis, OR and Casselton, ND in 1996 and 1997. HA383 × RHA373, HA372 × RHA377, and HA89 × RHA373 were the highest‐yielding hybrids from three heterotic patterns. HA383 × RHA373 had the highest seed yield across years and locations (3285 kg ha−1) among all hybrids. The most promising donors for increasing the seed yield of HA383 × RHA373 were HA822, HA851, and HA372. Similarly, the most promising donors for increasing the seed yield of HA372 × RHA377 were HA821 and HA384, and the most promising donors for increasing the seed yield of HA89 × RHA373 were HA383, HA384, and HA821. The elite gene pool of sunflower seems to be a rich source of favorable alleles for increasing hybrid seed yields.
Sensitivity of Peanut to Timing of Heat Stress during Reproductive Development
Authors: Prasad P.V.Vara , Craufurd P.Q. , Summerfield R.J.
Published: July 2010

Peanut (Arachis hypogaeaL.) crops grown in the semi‐arid tropics are commonly exposed to damaging hot temperatures of above 40°C. The objectives of this research were to identify the time(s) during reproductive development when hot days reduce yield, and to examine relations between flower production and sensitivity to heat stress. At start of flower bud initiation (21 d after planting, DAP) plants of the cvs ICGV 86015 and ICGV 87282 were grown either at 28/22°C (optimum temperature, OT) or at 38/22°C (high temperature, HT) or were reciprocally transferred at 3‐d intervals between the OT to HT regimes and vice versa, until 46 DAP. Transferred plants remained in the new temperature regime for 6 d before being returned to their original regime. All plants were harvested at 67 DAP. In cv. ICGV 86015, transfers between 6 d before and 15 d after flowering (DAF) significantly (P< 0.001) affected total number of pegs (i.e., pegs and pods) and reproductive (peg and pod) dry weight, with the greatest effect occurring at 9 DAF. In cv. ICGV 87282, number of pegs and reproductive dry weights were also significantly reduced by transfers at 9 and 12 DAF. Heat stress had no effect on flower production or the proportion of pegs forming pods, but did significantly reduce the proportion of flowers producing pegs. Data presented suggest that it is heat stress during floral bud development that determines peg number.
Quantitative Trait Loci for Tassel Traits in Maize
Authors: Berke T.G. , Rocheford T.R.
Published: July 2010

The inheritance of tassel traits in maize (Zea mays L.) is not well understood. This study was conducted to estimate the chromosomal location and magnitude of effect of major quantitative trait loci (QTL) affecting tassel branch angle (ANGLE), branches per tassel (BRANCH#), and tassel weight (TASSWT) in 200 S1 lines derived from a single F1 plant from a cross of Illinois High Oil (IHO) by Illinois Low Oil (Early Maturity) [ILO(EM)]. The restriction fragment length polymorphism (RFLP) genotypes of the 200 S1 lines were determined at 80 polymorphic loci. These lines were measured for ANGLE, BRANCH#, and TASSWT in replicated field trials during 1992 and 1993 at Urbana, IL. Composite interval mapping using selected markers as cofactors detected several QTL for each tassel trait. Six QTL located on chromosomes 2, 3, 5, 6, and 10 were significantly associated with ANGLE. They showed primarily dominant gene action and explained 43.1 and 50.7% of the phenotypic and genetic variance, respectively. Three QTL located on chromosomes 2, 4, and 7 were significantly associated with BRANCH#. They showed primarily additive gene action and explained 44.3 and 49.3% of the phenotypic and genetic variance, respectively. The QTL for BRANCH# on chromosome 7 explained 35.3% (R2) of the phenotypic variance. Seven QTL located on chromosomes 1, 2, 3, 4, and 7 were significantly associated with TASSWT. They showed primarily negative dominant gene action and explained 35.1 and 43.4% of the phenotypic and genetic variance, respectively. Most of the major QTL detected for these tassel traits were not associated with anthesis date (ANTH) in this population.
Increasing Yield of Spring Oilseed Rape Hybrids through Introgression of Winter Germplasm
Authors: Butruille D.V. , Guries R.P. , Osborn T.C.
Published: July 2010

Yields of spring oilseed rape (Brassica napus L.) hybrids are generally higher if derived from crosses of more distantly related spring cultivars. Winter cultivars are genetically very distinct from spring cultivars; however, it is not practical to use them directly as parents with spring cultivars for F1 hybrids because of their noncoincident flowering times, and the excessively delayed maturity of the F1 Thus, we tested whether the introgression of winter germplasm into spring‐type oilseed rape could further increase the yields of spring hybrids. Nineteen doubled‐haploid lines, derived from a cross between a spring canola (‘Stellar’) and a winter rapeseed (‘Major’) cultivar, were selected based on early‐flowering phenology and having a range of germplasm from Major estimated to be 21 to 74% by screening with 480 molecular marker loci. These lines were test‐crossed to two spring cultivars and evaluated for yield in 1994, 1995, and 1996 in Madison or Arlington, WI. The mean yield of the experimental hybrids was higher than the yields of cultivars, inbreds, and spring by spring hybrids in every year. The oil content was similar in all categories of germplasm. A slight delay in maturity may have contributed to the yield advantage of the experimental hybrids; however, there was no significant correlation between flowering time and yield among these hybrids. This study indicates that winter rapeseed may be a valuable source of germplasm for spring hybrid breeding.
AFLP Fingerprinting of Phaseolus lunatus L. and Related Wild Species from South America
Authors: Caicedo A.L. , Gaitán E. , Duque M.C. , Chica O. Toro , Debouck D.G. , Tohme J.
Published: July 2010

The taxonomic classification of the wild Lima bean complex needs to be assessed to select species for use in breeding programs and to identify genetic resources for conservation. The objectives of this study were to determine the genetic relationships among, and the phylogeny of, wild Lima bean (Phaseolus lunatus L.) and related species (P. augusti Harms, P. bolivianus Piper, P. pachyrrhizoides Harms, and P. rosei Piper) from South America and to identify specific genetic reserves for conservation. These relationships were investigated by means of amplified restriction fragment length polymorphism (AFLPs) on total genomic DNA. The 122 accessions formed a cluster that was distant from common bean (P. vulgaris L.), confirming earlier morphology and hybridology data. Two gene pools of wild Lima beans were confirmed. One was widely distributed in neotropical lowlands, while the other was restricted to the western Andes, in Ecuador and northern Peru. The study also revealed the existence of a third group of wild Lima bean distributed in the Departments of Boyacáand Cundinamarca, Colombia. The three species P. augusti, P. bolivianus, and P. pachyrrhizoides differed very little, certainly not sufficiently to merit a separate taxonomic ranking at the species level. The accessions could be grouped instead according to four geographic origins: Ecuador and northern Peru; Department of Junín, Peru; Departments of Cuzco and Apurímac, Peru; and Bolivia and northwestern Argentina. Results from this study should result in a better selection of parental materials in breeding programs and point to areas where germplasm collections and conservation are needed.
Yield Potential: Its Definition, Measurement, and Significance
Authors: Evans L. T. , Fischer R. A.
Published: July 2010

Yield potential is defined as the yield of a cultivar when grown in environments to which it is adapted, with nutrients and water non‐limiting and with pests, diseases, weeds, lodging, and other stresses effectively controlled. As such, it is distinguished from potential yield, which we define here as the maximum yield which could be reached by a crop in given environments, as determined, for example, by simulation models with plausible physiological and agronomic assumptions. Several implications of the definitions given above are considered, particularly those arising from cultivar interactions with agronomic practices and with the biotic and abiotic environments. We then discuss both direct and indirect methods of measuring progress in yield potential. Continuing progress in yield potential through conventional breeding is apparent in many crops, and is significant for yield progress at the farm level under a wide range of conditions. Among the small grain cereals, greater yield potential has derived mainly from the rise in harvest index associated with dwarfing, whereas in maize (Zea mays L.), it has come from increased tolerance to closer planting. The duration of photosynthetic activity has been extended in several crops but there is little evidence of increases in photosynthetic capacity or maximum crop growth rate. The rise in genetic yield potential in wheat and maize cultivars has been associated with progressive widening of their genetic background, and there is little sign of this slowing down.
Soybean Maturity Genes Associated with Seed Coat Pigmentation and Cracking in Response to Low Temperatures
Authors: Takahashi Ryoji , Abe Jun
Published: July 2010

Exposure of soybean [Glycine max (L.) Merr.] to chilling temperatures (≈15°C) at flowering induces browning around the hilum region and cracking of the seed coats. Both pigmentation and cracking degrade the external appearance of soybean seeds and reduce their commercial value. An earlier study showed that one of the genes responsible for pigmentation is closely associated with a maturity gene. The objective of this study was to evaluate the effect of five soybean maturity genes (E1–E5) on the intensity of seed coat pigmentation and cracking. Soybean cv. Harosoy (e1e2E3E4e5) and its near‐isogenic lines (NIL) for E1 to E5 loci were exposed to 15°C for 2 wk beginning 8 d after anthesis. Control plants were grown in a greenhouse throughout their life cycle, whereas treated plants were transferred from the greenhouse to a phytotron for the chilling treatment. Intensity of pigmentation was not affected by e3, slightly reduced by E2 and e4, and profoundly reduced by E1 and E5 Degree of cracking was slightly increased by e3 and drastically reduced by e4, E1, and E5 The results suggest that some of the soybean maturity genes have inhibitory effects on the intensity of seed coat pigmentation and cracking in response to low temperatures. Dominant alleles E1 and E5 are most effective in suppressing both pigmentation and cracking. Therefore, these two genes may be useful to ensure tolerance to chilling stress in cultivars with e3 and e4, which jointly condition the insensitivity to long daylength, an adaptive trait in high latitude regions.
Isolation and Characterization of Two Promoters from Linseed for Genetic Engineering
Authors: Jain Ravinder K. , Thompson R. Gail , Taylor David C. , MacKenzie Samuel L. , McHughen Alan , Rowland Gordon G. , Tenaschuk Don , Coffey Maxine
Published: July 2010

Linseed (Linum usitatissimum L.) is an important oilseed crop worldwide and is cultivated for the high level of linolenic acid (18:3) in its seed oil. Currently, there is a concerted effort to improve linseed by genetic engineering. This will require appropriate transgenes and tissue‐specific or constitutive promoters. We report the isolation and characterization of two linseed promoters from a two‐member gene family encoding the enzyme stearoyl‐acyl carrier protein desaturase (SAD). The SAD1 and SAD2 gene promoter were each fused transcriptionally with the reporter gene for β‐glucuronidase (uidA; GUS) and were transferred to linseed to study their expression pattern. In transgenic linseed, GUS activity mediated by the SAD2 promoter appeared to be constitutive and was detected in leaves, apices, stem, roots, flower buds, flowers, and seeds. In contrast, GUS activity mediated by the SAD1 promoter appeared to be root‐ and seed‐specific. In developing seeds, both the promoters exhibited a temporal expression pattern concomitant with protein and lipid biosyntheses. The GUS activity could be detected as early as 4 days after pollination (dap) and in mature seeds (∼50 dap) with the highest activities around mid‐development. The first pair of linseed promoters will be useful for manipulating the expression of indigenous as well as transgenes in linseed to create value‐added cultivars.
Heat Stress during Grain Filling in Maize: Effects on Kernel Growth and Metabolism
Authors: Wilhelm E. P. , Mullen R. E. , Keeling P. L. , Singletary G. W.
Published: July 2010

The average temperature in the U.S. Corn Belt during the grain‐filling period of maize (Zea mays L.) is above optimum for maximum grain yield. The objectives of this study were to determine the effects of an extended period of high temperature during grain filling on kernel growth, composition, and starch metabolism of seven maize inbreds. Plants were exposed to heat stress (33.5/25°C) or control (25/20°C) day/night temperature treatments in a greenhouse from 15 d after pollination (DAP) until maturity, and the experiment was conducted in triplicate over time. Root zone temperature was maintained at 25/20°C in both treatments. No significant interaction occurred between genotype and temperature treatments for nine grain traits. Heat stress lengthened the duration of grain filling on a heat unit (HU) basis, but an overcompensatory reduction in kernel growth rate per HU resulted in an average mature kernel dry weight loss of 7% (P = 0.06). Proportionally similar reductions occurred for starch, protein, and oil contents of the kernel. Heat stress also reduced kernel density. A survey of 11 enzymes of sugar and starch metabolism extracted from developing endosperm revealed that ADPglucose pyrophosphorylase, glucokinase, sucrose synthase, and soluble starch synthase were most sensitive to the high temperature treatment. However, upon adjusting enzyme activities with measured temperature coefficients (i.e., Q10), only ADPglucose pyrophosphorylase exhibited reduced activity. Results indicate that chronic heat stress during grain filling moderately restrains seed storage processes and select enzymes of starch metabolism to similar degrees across multiple maize inbreds.
Carbon and Nitrogen Reserve Remobilization Following Defoliation: Nitrogen and Elevated CO2 Effects
Authors: Skinner R. Howard , Morgan Jack A. , Hanson Jon D.
Published: July 2010

Early regrowth following defoliation of forage species often depends on remobilization of nitrogen and non‐structural carbohydrate (TNC) reserves stored in roots and crowns. The degree to which TNC and N remobilization contribute to regrowth can depend on internal concentrations and on external CO2 and N supplies. We studied the effect of CO2 and N supply on reserve remobilization during the first 20 d following defoliation of 9‐wk‐old alfalfa (Medicago sativa L.), western wheatgrass [Pascopyrum smithii (Rydb) A. Love], and blue grama [Bouteloua gracilis (H.B.K.) Lag ex Steud]. plants. Reserve remobilization was studied in controlled‐environment chambers set at either ambient (350 μmol mol−1) or elevated (700 μmol mol−1) CO2 Plants were fertilized twice weekly with Hoaglands solution containing either 0 mg L−1 (low N) or 400 mg L−1 N (high N). Elevated CO2 increased the total amount and percent of available TNC that was remobilized in alfalfa, and the amount of remobilized TNC in western wheatgrass, but reduced TNC remobilization in blue grama. Nitrogen fertilization had little effect on TNC remobilization at ambient CO2, but increased remobilization in alfalfa and reduced remobilization in the two grasses under elevated CO2 Alfalfa remobilized a greater percentage of its root and crown N reserves than either grass species. Nitrogen remobilization was highest under high N and ambient CO2 conditions for all species. Nitrogen deficiency and elevated CO2 reduced N remobilization and the contribution of remobilized N to shoot regrowth.
A Diagnosis of Yield‐Limiting Factors on Probe Genotypes for Characterizing Environments in Winter Wheat Trials
Authors: Brancourt‐Hulmel Maryse , Lecomte Christophe , Meynard Jean‐Marc
Published: July 2010

Genotype × environment interaction is fully analyzed when genotypes and environments are well characterized. Probe genotypes were studied in a simplified crop diagnosis to show how variates of yield components can strengthen characterization of environments by usual indicators of yield‐limiting factors. The objective of this study was to determine the main limiting factors of yield and to analyze their effects in wheat (Triticum aestivum L.) trials. Fixed genotypes (Talent, Soissons, Camp‐Rémy, and Arminda) were studied as probe genotypes at five experimental stations of the Institut National de la Recherche Agronomique (I.N.R.A.) (Rennes, Mons, La Miniére, Dijon, and Ondes) during 1991 and 1992. Two important variates, the reduction of kernel number and the reduction of thousand kernel weight, were analyzed to characterize the environments during the formation of yield. The former described the time‐period until flowering and the latter the grain‐filling period. In addition, factors that limit yield were determined through indicators such as water deficits, the ratio between nitrogen absorbed and kernel number, radiation, temperature, development of diseases (powdery mildew, strike rust, leaf rust, leaf and glume blotch), and lodging. Our study resulted in providing critical values for grain yield, kernel number, and thousand kernel weight for the four probe genotypes. Then reductions of yield components could be determined and analyzed. They provide useful information for characterizing environments subjected to numerous yield‐limiting factors. Our study also revealed that the biological variates (essentially susceptibility to powdery mildew and to lodging) affected yield more than the climatic variates.
Agronomic Performance of Root Chicory, Jerusalem Artichoke, and Sugarbeet in Stress and Nonstress Environments
Authors: Schittenhelm Siegfried
Published: July 2010

Introduction of the fructan crops root chicory (Cichorium intybus L.; RC) and Jerusalem artichoke (Helianthus tuberosus L.; JA) into agricultural production systems is desirable to diversify crop rotation. Field experiments were conducted to compare the agronomic performance of RC and JA with sugar beet (Beta vulgaris L.; SB). One set of cultivars during 1995, 1996, and 1997 and an additional set in 1997 were grown on a sandy loam soil (Haplic Luvisol) at Braunschweig, Germany. Crops were cultivated with and without supplemental irrigation, complete and no weed control (1995 and 1996), and N fertilization rates of 0, 60, and 120 kg ha−1 Severe water stress caused significant but similar storage organ yield losses in all crops, whereas mild water stress mainly affected JA yields. Averaged across years and N levels, storage organ yield losses through weed competition under irrigation amounted to 70, 47, and 8% in SB, RC, and JA, respectively. Averaged across years, in the absence of water and weed stress, SB, RC, and JA at their respective optimal N levels gave root and tuber dry matter yields of 14.8, 15.0, and 11.5 Mg ha−1, and sugar yields of 11.5, 11.2, and 8.1 Mg ha−1, respectively. Maximal SB and JA yields generally were achieved at the highest N rate, while RC peak yields were attained at 60 kg N ha−1 With the same amount of N taken up, RC in 1995 and SB in 1996 and 1997 produced the highest sugar yields.
Protein Degradation and Fermentation Characteristics of Red Clover and Alfalfa Silage Harvested with Varying Levels of Total Nonstructural Carbohydrates
Authors: Owens V. N. , Albrecht K. A. , Muck R. E. , Duke S. H.
Published: July 2010

Extensive degradation of protein during fermentation of high‐protein crops reduces efficiency of dietary N utilization in ruminants. Evidence suggests that enhanced levels of fermentable carbohydrates can reduce proteolysis. Our objective was to evaluate whether delaying daily cutting time, to allow total nonstructural carbohydrates (TNC) to accumulate, would inhibit protein degradation by way of greater acid production in the silo. Red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) were harvested at 0600, 1000, 1400, and 1800 h in 1993, 1994, and 1995 and wilted to a dry matter (DM) content of 350 g kg−1 before ensiling. The level of TNC in fresh forage of both species increased throughout the day. Starch accounted for most of the daily change in TNC in fresh alfalfa, whereas in red clover, quantitative increases in sugar and starch impacted TNC similarly. Level of TNC at initiation of ensiling did not consistently affect protein degradation during fermentation as confirmed by generally insignificant correlation coefficients. The extent of proteolysis in the silo was consistently greater in alfalfa than red clover. Silage pH typically decreased and starch increased as cutting time was delayed from 0600 to 1800 h. While the extent of proteolysis was largely unaffected by inherent increases in TNC, lower silage pH and higher starch concentrations indicate that silage from the afternoon cuttings may be better preserved and higher in quality.
Genotype × Region Interaction for Two‐Row Barley Yield in Canada
Authors: Atlin G. N. , McRae K. B. , Lu X.
Published: July 2010

Barley (Hordeum vulgare L.) breeding programs recognize eastern and western Canada as separate target regions, but the extent of local adaptation to regions and subregions within them has not been studied. Genotype × region and subregion interactions were estimated in 145 lines from the two‐row barley cross Harrington/TR306 in 22 trials in 1992‐1993. The trials were grouped into five subregions (Maritimes–Quebec, Ontario, Manitoba–North Dakota, Saskatchewan, and Alberta) and two regions (eastern Canada and western Canada plus North Dakota). Variance components were estimated by a model in which the genotype × location (σ2GL) variance was subdivided into a genotype × region (or subregion) variance (σ2GS), and a within‐region or ‐subregion σ2GL No σ2GS was observed within the eastern or western regions, and genotypic correlations across subregions within regions approached 1.0. Significant σ2GS was observed for eastern versus western Canada, but the correlation between genotypic effects across these regions was 0.83. In a selection experiment, subdivision of the eastern or western regions did not increase response. Selection in the east produced greater yields in both the east and west. The same genotype ranked first for yield in both regions. There was little specific adaptation to subregions, and two‐row barley genotypes were broadly adapted across northern North America. Further subdivision of the regions is unwarranted, and selection in either region is likely to result in response in the other. The lack of local adaptation indicates that breeding programs that test broadly are likely to outperform ones that are narrowly targeted.
Crop Improvement and the Accumulation and Partitioning of Biomass and Nitrogen in Lentil
Authors: Whitehead S. J. , Summerfield R. J. , Muehlbauer F. J. , Coyne C. J. , Ellis R. H. , Wheeler T. R.
Published: July 2010

Domestication and subsequent genetic enhancement in lentil (Lens culinaris Medik.) have involved changes in plant structure and DM distribution. These changes were examined using a “genetic gradient” comprising three representatives each of Lens orientalis (Boiss.) progenitors, landraces, pre‐1980 cultivars, and modern germplasm. All 12 genotypes were sown at Pullman, WA, in 1996 and 1997, and at Reading, UK, in 1997. The biomass (all genotypes) and N concentration (four genotypes) of above‐ground tissues were measured at 50% flowering (leaf and stem) and at reproductive maturity (leaf, stem, pod wall and seed). The progenitors produced meager biomass (averaging 0.72 Mg ha−1) and poor HI (0.19), and consequently small seed yields (0.11 Mg ha−1). Productive landraces had substantially higher biomass (3.52 Mg ha−1), improved HI (0.34), and larger seed yields (1.13 Mg ha−1). Biomass and seed yield were increased further by the selection of cultivars (5.11 and 1.32 Mg ha−1, respectively). The development of modern germplasm by hybridization further increased seed yields (1.95 Mg ha−1). Consistent seed yield improvements have not been associated with consistent increases in HI. Instead a strong, positive correlation between seed yield and biomass has persisted. NHI increased more rapidly than HI and is unlikely to increase further in the future. Future seed yield improvement will therefore depend on increased N accumulation. Reliance on N2 fixation must be supported by increased photosynthetic capacity and therefore by vegetative biomass. An advantageous correlation between seed yield and residue production seems likely to persist as crop improvement continues.