bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Number of Seed Bulked and Population Size on Genetic Variability When Using the Multiple‐Seed Procedure of SSD
Authors: Macchiavelli Raul , Beaver James S.
Published: July 2010

Single‐seed descent is used by grain legume breeders to maintain genetic variability in populations of advanced generation lines. To reduce labor costs, breeders often use a multiple‐seed procedure in which a single pod rather than a single seed is harvested from each plant and bulked. This paper studied the distribution of the proportion of original F2 plants represented after advancing populations ranging from 100 to 600 plants from the F2 to the F6 generation when the multiple‐seed procedure of SSD is used. Since the analytical solution to this problem is intractable, involving a 4‐fold convolution of a hypergeometric distribution, a simulation was run in SAS to estimate this probability distribution. An increase in the size of the population advanced from the F2 to the F6 generation did not influence significantly the mean proportion of F2 plants represented in the F6 generation but decreased its variability. An increase in the number of seed per pod from two to six reduced the mean proportion of F2 plants represented in the F6 generation from 0.45 to 0.35, but did not decrease significantly the standard deviations of the distributions. Using the multiple‐seed procedure, grain legume breeders could expect, on the average, that at least every third F6 line would be derived from a different F2 plant. This should generate considerable genetic variability for the selection for quantitatively inherited traits such as seed yield.
Mapping Resistance to Multiple Races of Heterodera glycines in Soybean PI 89772
Authors: Yue Pin , Sleper David A. , Arelli Prakash R.
Published: July 2010

Breeding soybean [Glycine max (L.) Merr.] cultivars for resistance to soybean cyst nematode (SCN) [Heterodera glycines Ichinohe] is the most efficient means to control this pest. Evaluating and developing new resistance germplasm sources for soybean breeding is very important to prevent SCN from race shifts and provide durable resistance in soybean. We evaluated a newly found germplasm, soybean plant introduction (PI) 89772, which is resistant to SCN Races 1, 2, 3, 5, and moderately resistant to Race 14. The objectives were to identify molecular markers associated with SCN resistance, investigate resistant allelic relationships, and evaluate marker‐assisted selection efficiency. The F2 and F2:3 populations were produced by crossing PI 89772 with the susceptible soybean cultivar Hamilton. Thirty‐nine restriction fragment length polymorphism (RFLP) and 54 simple sequence repeat (SSR) markers found to be polymorphic were used to anchor loci conferring resistance to SCN Races 1, 2, 3, and 5. Two to three loci were found to give resistance to each SCN race. We found that resistance loci for different races could be anchored within the same region on linkage group (LG) G. A region on LG B1 was also shared by loci providing resistance to SCN Races 1, 2, and 5. Our results indicated that no single locus could provide complete resistance to any one SCN race. The major loci combinations provided high levels of resistance. We conclude that these markers could be highly useful in marker‐assisted selection.
Inheritance of Medium Stearic Acid Content in the Seed Oil of a Sunflower Mutant CAS‐4
Authors: Pérez‐Vich Begoña , Garcés Rafael , Fernández‐Martínez Jose María
Published: July 2010

The sunflower (Helianthus annuus L.) line CAS‐4 obtained by mutagenesis has an increased stearic acid (C18:0) content in its seed oil (130 g kg−1), which is desired for some food products. The objectives of this study were to determine (i) the inheritance of medium C18:0 content in CAS‐4, (ii) the relationship between CAS‐4 and the high C18:0 mutant CAS‐3, and (iii) if recombinants with higher C18:0 content than CAS‐3 could be obtained. CAS‐4 was reciprocally crossed with its original parental line RDF‐1‐532 (80 g kg−1 C18:0), HA‐89 (standard low 50 g kg−1 C18:0), and CAS‐3 (250 g kg−1 C18:0). The fatty acid content of the F1, F2, BC1F1 to both parents, and F3 seeds was analyzed by gas‐liquid chromatography (GLC). Alleles controlling low C18:0 exhibited partial dominance to those for medium C18:0, and these were partially dominant to those for high C18:0. Segregation patterns fit a two‐loci model for the HA‐89 × CAS‐4 cross and one‐locus model for the RDF‐1‐532 × CAS‐4 and the CAS‐3 × CAS‐4 crosses. We concluded that medium C18:0 content of CAS‐4 was controlled by alleles at the Es1 and Es2 loci previously identified in CAS‐3, or at tightly linked loci. The CAS‐4 alleles at the Es2 locus are those present in CAS‐3 (es2es2), whereas the alleles at the Es1 locus are different from those of CAS‐3 (es1es1) and have been designated es1bes1b The proposed genotype (C18:0 content) of CAS‐4 is es1bes1bes2es2 The continuous distribution observed in the HA‐89 crosses with CAS‐4 indicated that minor genes and environmental effects also are important in the expression of C18:0 content in CAS‐4.
Genetic Distance among Selected Cotton Genotypes and Its Relationship with F2 Performance
Authors: Gutiérrez O. A. , Basu S. , Saha S. , Jenkins J. N. , Shoemaker D. B. , Cheatham C. L. , McCarty J. C.
Published: July 2010

Knowledge of genetic diversity and relationships among breeding materials has a significant impact on crop improvement. Association between parental divergence and progeny performance has not been well documented in cotton (Gossypium hirsutum L.). The objectives of this study were to estimate genetic diversity among selected cotton genotypes on the basis of simple sequence repeat (SSR) markers, and to investigate the relationship between genetic diversity and F2‐bulk population performance. Five U.S. and four Australian cultivars, and two day‐neutral converted lines of G. hirsutum were genotyped by means of 90 SSR primer pairs providing 69 polymorphic marker loci. Genetic distance (GD) between genotypes ranged from 0.06 to 0.34 for the 11 parental genotypes. The highest GD (0.34) was observed between ST474 and the day‐neutral converted line B1388. The lowest GD (0.06) was detected between cultivars FM832 and FM975. The GD between day‐neutral converted lines and cultivars ranged from 0.26 to 0.34. Among the Australian cultivars, GD ranged from 0.06 to 0.19 while GD among U.S. cultivars varied from 0.10 to 0.22, indicating a narrow genetic base. Significant correlations between agronomic and fiber traits of F2‐bulk populations and GD ranged from negative to positive depending on the traits, genetic background, and environment. On the basis of SSR markers, GD revealed a lack of genetic diversity among all genotypes and it was a poor predictor of overall F2 performance. However, when genotypes with maximum range of GD were present, it was a better predictor for some traits.
Quantitative Trait Loci Controlling Leaf and Tassel Traits in a B73 × Mo17 Population of Maize
Authors: Mickelson S. M. , Stuber C. S. , Senior L. , Kaeppler S. M.
Published: July 2010

Light penetration into the canopy of maize (Zea mays L.) production fields is an important determinant of grain yield. Factors affecting light penetration include agricultural practices such as planting density and plant morphological factors such as leaf angle, leaf size, and tassel size. The objectives of this experiment were to identify genomic regions controlling the inheritance of leaf angle and tassel morphology in a B73 × Mo17 recombinant inbred population. Three quantitative trait loci (QTL) for tassel branch angle were detected which explained 35.6% of the phenotypic variation. Six QTL were detected for tassel branch number with three of these QTL on chromosome 2. Nine QTL were detected for leaf angle in one or more environments. Significant phenotypic correlations were detected between tassel branch angle and tassel branch number and between tassel branch number and leaf angle. Overlapping support intervals were identified between QTL detected for leaf angle and for tassel branch number on chromosome 2 near marker umc53a. Additionally, a QTL near marker bnl6.10 on chromosome 5 identified for tassel branch angle was in the same region as a QTL identified for leaf angle. The results of this study indicate that common genetic relationships exist between tassel traits and leaf angle.
Alignment of Lipid Bodies along the Plasma Membrane during the Acquisition of Desiccation Tolerance in Maize Seed
Authors: Cordova‐Tellez Leobigildo , Burris Joseph S.
Published: July 2010

The impairment of lipid body alignment along the plasma membrane during artificial drying of maize (Zea mays L.) seed has been associated with decreases in germination and vigor. In this study, we question further its potential functions as well as the alignment mechanisms. Ears of hybrid maize [B73 × (H99 × H95)] were harvested at about. 550, 500, 400, and 320 g H2O kg−1 fresh weight (fw) and subjected to preconditioning (PC) (ear drying at 35°C and 0.47 m s−1 airflow rate) for 0, 12, 24, 36, and 48 h before fast drying (shelled seed, 35°C and 5.10 m s−1 airflow rate) treatments to decrease seed moisture content (MC) to about 130 g H2O kg−1 fw. In a cross section of the embryo radicle, alignment of lipid bodies (LB) occurred first in the root cap, followed by outer quiescent center (QC) cells and inner QC cells. This alignment pattern was observed during PC and under field drying conditions. Cell plasmolysis and aberrations of the LB were evident in seed harvested at MC > 400 g H2O kg−1 fw and subjected to fast drying without PC. Lipid body aberrations decreased in severity with PC, seed development, and field drying. The alignment of LB coincided with changes in embryo‐drying rates. Decreases in lipid body aberrations coincided with decreases in cell solute leakage and shoot/root ratio and increases in germination percentage. We conclude that alignment of LB along the plasma membrane is a progressive process that occurs from the periphery to the inner QC cells of the embryo radicle. Alignment of LB along the plasma membrane may change cell water relations leading to a more organized dehydration during seed drying. High embryo drying rates may prevent alignment of LB along the plasma membrane and are associated with low germination and vigor.
Green Leaf Chemistry of Various Turfgrasses
Authors: Johnson Albert W. , Snook Maurice E. , Wiseman Billy R.
Published: July 2010

Six grass species (zoysiagrass, bermudagrass, centipedegrass, tall fescue, St. Augustinegrass, and Kentucky bluegrass) were analyzed for polyphenols and flavonoids by high performance liquid chromatography. Each gave a characteristic leaf chemistry profile that allowed it to be differentiated from the other grasses. ‘Emerald’ zoysiagrass was characterized by the presence of chlorogenic acid and a group of luteolin‐glycosides containing glucose and/or arabinose. ‘Tifgreen’ bermudagrass contained no chlorogenic acid, and at least two of the flavonoids were apigenin‐glycosides in addition to several luteolin‐glycosides. Common centipedegrass and Ky 31 tall fescue both contained high levels of chlorogenic acid, but their flavonoid composition was different. Centipedegrass contained luteolin‐type flavonoid‐glycosides and maysin, an unusual luteolin‐diglycoside that possesses a unique keto‐sugar. Tall fescue contained quercetin‐type flavonoids rather than luteolin. Rutin was found as a major constituent of tall fescue. ‘Kenblue’ Kentucky bluegrass and ‘Raleigh’ St. Augustinegrass contained no chlorogenic acid. These two grasses contained several luteolin‐glycosides but not the broad, multiple flavonoid profiles of zoysiagrass and bermudagrass. Fall armyworm [FAW; Spodoptera frugiperda (J.E. Smith)] larval growth was significantly affected by the type of grass they fed upon in laboratory no‐choice tests. Fall armyworm larval weight reductions (as a percentage of the bermudagrasses) at 7 d after infestation were 90, 79, and 29% for zoysiagrass, centipedegrass, and St. Augustinegrass, respectively. Chlorogenic acid, luteolin, and the flavonoid‐glycosides rutin, maysin, and isoorientin were highly active in a laboratory bioassay in reducing FAW larval weights; however, no correlations could be made between FAW resistance and the levels of chlorogenic acid, flavonoids, or total phenolics extractable from the grasses evaluated.
Developing a Mini Core of Peanut for Utilization of Genetic Resources
Authors: Upadhyaya Hari D. , Bramel Paula J. , Ortiz Rodomiro , Singh Sube
Published: July 2010

Peanut (Arachis hypogaea L.) breeding programs with a goal of rapid cultivar development have used mainly elite breeding lines and cultivars, which has resulted in the development of breeding materials with a narrow genetic base. Utilization of exotic germplasm resources in breeding programs is needed to enhance the diversity of cultivars. Scientific plant breeding and its need for large variability, concern about potential loss of variability, and nonavailability of low cost tools to identify similarities or differences among accessions led genebanks to hold large germplasm collections. Core collections, generally contain about 10% of total accessions, represent the genetic variability of entire germplasm collection, and have been suggested as a way to enhance use of genetic resources in crop improvement. The objective of this study was to develop a peanut mini core subset. The peanut core subset was evaluated for morphological, agronomic, and quality traits in the rainy and postrainy seasons. Ward's method of clustering was used to separate core collection accessions into groups of similar accessions. A mini core subset consisting of 184 accessions was selected. Newman Keuls' test for means, Levene's test for variances, and chi‐square test for frequency distribution analysis for different traits indicated that the variation available in the core collection has been preserved in the mini core subset. This mini core subset will enhance exploitation of peanut genetic resources.
Application of fluorescence microscopy and image analysis for quantifying dynamics of maize pollen shed
Authors: Fonseca Agustin E. , Westgate Mark E. , Doyle Robert T.
Published: July 2010

The objective of this study was to develop a simple, rapid and accurate technique to quantify maize (Zea mays L.) pollen shed under field conditions, capitalizing on the capacity of pollen to fluoresce and recent improvements in microscopic methods for acquiring, processing, and analyzing fluorescence signals from biological systems. Pollen shed naturally by the tassels was captured daily on passive pollen traps placed at apical ear level. Fluorescence microscopy was used to generate digital images of the trapped pollen, and pollen density per unit area was counted using commercial imaging software. Visual confirmation of fluorescing pollen grains indicated high measurement accuracy (r2 = 0.99) for the entire range of pollen shed densities typically encountered in the field. Pollen was randomly distributed across the surface of the pollen trap, and six to eight images per trap provided greater than 95% confidence for the mean trap value. The entire process of sample preparation, image capture, and image counting required less than 6 min per trap. The accuracy and ease of use of this technique make it ideal for characterizing the pattern of maize pollen production and dispersal under field conditions.
Early Developmental Responses of White Clover Roothair Lengths to Calcium, Protons, and Aluminum in Solution and Soil Cultures
Authors: Brauer David , Staley Tom
Published: July 2010

Acidic soils tend to limit the nodulation of forage legumes and roothairs are important for Rhizobia binding and the initiation of nodule formation. This study examined the effects of Ca, pH, and Al on the length of roothairs in nutrient solutions and soils with white clover (Trifolium repens L., cultivar Huia) seedlings. The lengths of roothairs of 1‐ to 2‐d‐old seedlings was not affected by increases in solution Al up to 24 μM in nutrient solution experiments, but showed a pronounced optimum at a predicted root surface pH of 3.8. Roothair lengths of white clover seedlings 2 to 10 d after planting were also assessed in a Gilpin series silt loam collected from New, WV, and amended with various levels of lime. Soils ranged in pH from 4.6 to 5.3 and soil base saturation of Al from 46 to 8%. No significant differences in roothair lengths as a function of soil pH and/or soil available Al were observed. Previous results conducted under similar experimental conditions demonstrated that soil pH–soil‐available Al adversely affected on root elongation and nodulation. When results from this and the previous reports are considered together, the combined results suggest that root elongation and nodulation were more sensitive than roothair length to acidic soil conditions.
Genetic Control of Prolificacy and Related Traits in the Golden Glow Maize Population: I. Phenotypic Evaluation
Authors: de Leon N. , Coors J. G. , Kaeppler S. M. , Rosa G. J. M.
Published: July 2010

Prolificacy (the potential to produce ear shoots at multiple nodes on the main stalk) has been under selection since the early domestication of maize (Zea mays subsp. mays) from teosinte (Z. mays subsp. parviglumis). Until the early part of the 20th century, before mechanization, human selection may have favored single‐eared maize because it facilitated hand‐harvesting. Prolificacy, however, has the potential to increase stress tolerance under intensive management. Our objectives were (i) to assess variation for prolificacy and 15 related morphological traits in a population of 194 F3 families derived from inbred line A679 and a highly prolific S1 plant from the cultivar Golden Glow after 23 cycles of mass selection for prolificacy; and (ii) to determine relationships among traits and to infer which ones appear to be controlled by similar genetic factors. Traits were evaluated with two replications in three field environments. The population varied significantly for all traits and most traits had relatively high heritabilities (>0.80). Some traits were highly correlated, and two main groups were identified. These groups involved traits mostly associated with either the activity of axillary meristems, or intercalary meristems. In general, the correlations of traits across these two groups were insignificant or of lesser magnitude than within groups, suggesting that common genetic factors might be influencing some of these morphological traits.
Putative Quantitative Trait Loci for Physical and Chemical Components of Common Bean
Authors: Guzmán‐Maldonado Salvador H. , Martínez Octavio , Acosta‐Gallegos Jorge A. , Guevara‐Lara Fidel , Paredes‐López Octavio
Published: July 2010

In common bean (Phaseolus vulgaris L.), some nutritional traits such as proteins and mineral content are lower in the cultivated form as compared with the wild counterpart. To assess the feasibility of wild bean as the putative source of desirable traits such as minerals or tannins, this study was performed to identify quantitative trait loci (QTL) associated with seed mass, Ca, Fe, Zn, and tannin content in bean seed. Two‐hundred‐ninety‐one amplified fragment length polymorphism (AFLP) markers were scored in 120 F2:3 segregating individuals derived from a cross between cultivated ‘Bayo Baranda’ and wild common bean accession G‐22837. Seed weight and minerals and tannin contents were quantified on the seed harvested from the 120 individual plants. Significant transgressive segregation was observed among the F2:3 individuals for some characteristics. A total of 57 AFLP markers were distributed among five linkage groups with a coverage of 497 centiMorgans (cM). Five putative QTL were significantly associated with seed mass, two with Ca, two with Fe, one with Zn, and four with tannin content in the seed. These QTL explained ≈42, 25, 25, 15, and 42% of the phenotypic variance, respectively. Due to known environmental effect on most nutritional traits, the use of QTL with larger effects could be used to screen segregating populations that include wild genotypes, wild populations, and ancestral landraces from the region where outstanding wild populations are identified.
The PCR‐Based Marker MWG2018 Linked to the RDG2A Leaf Stripe Resistance Gene Is a Useful Tool for Assessing Barley Resistance in Breeding Programs
Authors: Arru L. , Faccini N. , Govoni C. , Cattivelli L. , Pecchioni N. , Delogu G. , Stanca A. M. , Valè G.
Published: July 2010

Leaf stripe, caused by the fungus Pyrenophora graminea Ito et Kuribayashi [anamorph Drechslera graminea (Rabenh. ex. Schlech.) Shoemaker], is an important seed‐borne disease of barley (Hordeum vulgare L.). The objective of this study was to verify the reliability of a PCR‐based marker (MWG2018) associated with the resistance gene Rdg2a and to assess the leaf stripe resistant phenotype in barley breeding programs. A large number of barley cultivars and accessions were thus evaluated for their reaction to a highly virulent monoconidial isolate (Dg2) of the pathogen and genotyped for the allele of the molecular marker. Several resistant genotypes were identified and four were shown to possess the same allele as the cultivar Thibaut (the resistant parent of the original mapping population in which Rdg2a was identified) at the marker locus. One of them, cv. Rebelle, is being used as a source of leaf stripe resistance in winter barley breeding programs. The allelic composition at the MWG2018 locus was verified in several resistant lines bred from five crosses, in which Rebelle acted directly or indirectly as donor of the resistance. The results showed that the resistant phenotype of the lines was always associated with the resistance allele of the molecular marker, thereby demonstrating its reliability for selecting leaf stripe resistance. The MWG2018 PCR‐based marker can therefore be proposed as a tool to assess the resistant phenotype.
Inheritance of Resistance to Tobacco Cyst Nematode in Flue‐Cured Tobacco
Authors: Crowder Barbara J. , Wilkinson Carol A. , Johnson Charles S. , Eisenbach Jon D.
Published: July 2010

The tobacco cyst nematode [Globodera tabacum solanacearum (Miller and Gray) Behrens] is an important pathogen affecting flue‐cured tobacco (Nicotiana tabacum L.) in Virginia and North Carolina and type 32 tobacco in Maryland. The objective of this study was to determine the mode of inheritance of resistance to G. t. solanacearum in the flue‐cured tobacco cultivars Coker 371 Gold and Kutsaga 110. Each cultivar was crossed to the susceptible cultivar K 326 and F1 progeny were backcrossed to each parent. Plants from each parent and F1, F2, BC1Ps, and BC1Pr progeny were evaluated for G. t. solanacearum resistance in the greenhouse. Six‐week‐old transplants were inoculated with 6000 G. t. solanacearum eggs from crushed cysts. Eight weeks after inoculation, a 1‐g sample of fibrous root was stained and vermiform, swollen, pyriform, and adult nematodes were counted. The number of cysts and eggs per 400 000 mm3 of soil were counted from each transplant. Generation means analyses were performed. Additive and dominance gene action play an important role in resistance to G. t. solanacearum in Coker 371 Gold and Kutsaga 110. F2 progeny data from the Coker 371 Gold cross fit a 3:1 (resistant:susceptible) segregation ratio and BC1Ps generation data fit a 1:1 segregation ratio, indicating that resistance to G. t. solanacearum is conferred by a single dominant gene. A continuous range of variation was observed among the F2 progeny for the K 326 × Kutsaga 110 cross, indicating resistance in Kutsaga 110 is quantitative. Globodera tabacum solanacearum resistance in Coker 371 Gold and Kutsaga 110 may be derived from different sources.
Evaluation of Spring Wheat Quality Traits and Genotypes for Production of Cantonese Asian Noodles
Authors: Davies John , Berzonsky William A.
Published: July 2010

Cantonese noodles are a possible end‐use product for spring wheat (Triticum aestivum L.). This product may provide an export opportunity for growers and be an alternative to the pan bread market. It might also be possible to produce dual‐use spring wheat for both markets. Knowledge of genotype and environment effects on spring wheat quality characteristics relating to Cantonese noodle discoloration will assist breeders in developing cultivars. Nine spring wheat genotypes were grown at four North Dakota locations in 2000 and 2001. Samples were analyzed for kernel polyphenol oxidase (PPO) activity, flour protein content, kernel brightness, and flour ash content. Yellow alkaline Cantonese‐style noodle sheets were made from flour milled from each sample and brightness (L*) and yellowness (b*) color measurements taken at 0 and 24 h to evaluate noodle discoloration. Genotypes having low kernel PPO activity, moderate flour protein content, bright kernels, and low flour ash concentrations produced Cantonese noodle sheets having high brightness and yellowness after 24 h. Genotype by environment interactions were significant for wheat quality characteristics related to noodle quality, due in part to rank changes in genotype means across environments. Genotype IDO 470 was identified as having desirable wheat quality characteristics for Cantonese noodle color, indicating that spring wheat genotypes with acceptable noodle quality can be produced for the region. The development of dual‐use spring wheat genotypes may be possible if breeders select for traits that maximize noodle quality but are neutral or have no significant impact on pan bread quality.
Establishment and Seedling Growth of Big Bluestem and Switchgrass Populations Divergently Selected for Seedling Tiller Number
Authors: Smart Alexander J. , Moser Lowell E. , Vogel Kenneth P.
Published: July 2010

Selection at the seedling stage in grass breeding would be extremely useful if seedling traits are correlated to desired agronomic traits. The objective of this study was to evaluate seedling morphological development, plant growth, and field establishment of big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) populations that were developed by divergent selection for seedling tiller number while selecting for high shoot weight. Six populations were evaluated: (i) ‘Pawnee’ big bluestem base, (ii) ‘Pathfinder’ switchgrass base, (iii) big bluestem multiple tiller, (iv) big bluestem single tiller, (v) switchgrass multiple tiller, and (vi) switchgrass single tiller. Field plots were seeded in spring 1999 and 2000 in a Kennebec silt loam (fine‐silty, mixed, superactive, mesic Cumulic Hapludolls). Plants were excavated and evaluated during the growing season for shoot weight, root weight, and morphological stage of shoot and root systems. There were no major population differences in shoot weight, root weight, and morphological root stage. Shoot stage was higher for multiple tiller populations than single tiller populations 6 wk after emergence. Stand counts for all populations exceeded 10 seedlings per linear m of row, which is considered an acceptable stand density, and there were no consistent differences among populations. Populations divergently selected for seedling tiller number did not differ in ability to become established under field conditions because root systems apparently were not altered by the selection for seedling tiller number and weight. These results suggest that selection for high shoot weight did not improve seedling vigor in the field.
Identification of QTLs and Environmental Interactions Associated with Agronomic Traits on Chromosome 3A of Wheat
Authors: Campbell B. T. , Baenziger P. S. , Gill K. S. , Eskridge K. M. , Budak H. , Erayman M. , Dweikat I. , Yen Y.
Published: July 2010

Genetic analyses of complex traits in wheat (Triticum aestivum L.) are facilitated by the availability of unique genetic tools such as chromosome substitution lines and recombinant inbred chromosome lines (RICLs) which allow the effects of genes on single chromosomes to be studied individually. Chromosome 3A of ‘Wichita’ is known to contain alleles at quantitative trait loci (QTLs) that influence variation in grain yield and agronomic performance traits relative to alleles of ‘Cheyenne’. To determine the number, location, and environmental interactions of genes related to agronomic performance on chromosome 3A, QTL and QTL × environment analyses of 98 RICLs‐3A were conducted in seven locations across Nebraska from 1999 through 2001. QTLs were detected for seven of eight agronomic traits measured and generally localized to three regions of chromosome 3A. QTL × environment interactions were detected for some QTLs and these interactions were caused by changes in magnitude and crossover interactions. Major QTLs for kernels per square meter and grain yield were associated within a 5‐centimorgan (cM) interval and appeared to represent a single QTL with pleiotropic effects. This particular QTL displayed environmental interactions caused by changes in magnitude, wherein the positive effect of the Wichita QTL allele was larger in higher yielding environments.
Use of A3 Cytoplasm to Reduce Risk of Gene Flow through Sorghum Pollen
Authors: Pedersen J. F. , Marx D. B. , Funnell D. L.
Published: July 2010

A critical impediment to field testing and deployment of transgenic sorghum [Sorghum bicolor (L.) Moench] is the threat of gene flow to weedy relatives through pollen. A technique using sorghum with A3 cytoplasmic male sterility to control transgene flow through pollen while using nontransgenic pollinators is described and an experiment was designed to evaluate the risk of viable pollen flow using A3 hybrids under field conditions. Seed set under pollinating bags (an indicator of fertile pollen) was evaluated at the University of Nebraska Field Laboratory at Ithaca, NE, in 2001 and 2002 on selfed F2 progeny grown from open pollinated seed of 12 F1 hybrids produced in A1 and A3 cytoplasm. The F2 seed was produced in hybrid yield trials in 1997 and 1998 at Ithaca, NE. In each evaluation year, the experimental design was a split‐split plot with seed production year the main plot factor, hybrid as the subplot factor, and cytoplasm as the sub‐subplot factor. Cytoplasm effects were highly significant, with percent seed set on A1 F2 individuals averaging 74%, and on A3 F2 individuals averaging 0.04%. Upper confidence limits (P = 0.05) for percent seed set were 1.32% or less for the progeny from all A3 hybrids. Polymerase chain reaction (PCR) analysis confirmed that four male fertile individuals (from a population of 1007) were detected with A3 cytoplasm. These results support the hypothesis that gene flow through pollen can be severely restricted but not eliminated in sorghum by the use of A3 cytoplasmic male sterility.
RAPD Marker Variation among Smooth Bromegrass Cultivars
Authors: Diaby Mamady , Casler Michael D.
Published: July 2010

The level of genetic diversity within and among smooth bromegrass (Bromus inermis Leyss.) cultivars and land races is unknown. The objective of this study was to investigate and characterize genetic diversity of smooth bromegrass cultivars and selected populations on the basis of random amplified polymorphic DNA (RAPD) markers. Variation among 277 individual plants from 40 smooth bromegrass cultivars was evaluated by means of RAPD markers. Nineteen primers evaluated amplified 97 informative amplicons. Several RAPD marker bands showed unique patterns of mean frequency differences among germplasm groups. A dendrogram constructed from average linkage cluster analysis did not indicate any clear pattern of division on the basis of discrete or putative climatype or adaptation zones. There was considerable correspondence to known pedigree relationships revealed from a previous smooth bromegrass morphological clustering analysis, particularly for lines that are closely related to each other. The two interspecific hybrids between B. inermis and B. pumpellianus Schribner (Polar) and B. riparius Rehm. (S‐9183‐H) did not exhibit any species‐specific markers. All groups of smooth bromegrass germplasm were found to have high within‐population genetic variation that ranged from 84 to 96% of the total, reflecting the outcrossing reproduction and probably the complex inheritance of smooth bromegrass. Analysis of molecular variance showed the largest interpopulation genetic variation for contemporary germplasm sources, supporting morphological studies for the existence of genetic variability among contemporary smooth bromegrass germplasms. These results suggest that landrace cultivars likely remain useful for germplasm improvement and cultivar development.
Sequential Path Model for Determining Interrelationships among Grain Yield and Related Characters in Maize
Authors: Mohammadi S. A. , Prasanna B. M. , Singh N. N.
Published: July 2010

Knowledge of interrelationships between grain yield and its contributing components will improve the efficiency of breeding programs through the use of appropriate selection indices. Previous path analyses studies in maize (Zea mays L.) treated yield components as first‐order variables. The present study, based on evaluation of 90 experimental maize hybrids (comprising one diallel and one line × tester set) at two locations in India, utilizes a sequential path model for analysis of genetic associations among grain yield and its related traits by ordering the various variables in first‐, second‐, and third‐order paths on the basis of their maximum direct effects and minimal collinearity. The sequential path model showed distinct advantages over the conventional path model in discerning the actual effects of different predictor variables. Two first‐order variables, namely 100‐grain weight and total number of kernels per ear, revealed highest direct effects on total grain weight (p = 0.74 and p = 0.78, respectively), while ear length, ear diameter, number of kernel rows, and number of kernels per row were found to fit as second‐order variables. All direct effects were found to be significant, as indicated by bootstrap analysis. Test for the goodness‐of‐fit revealed that the sequential path model provided better fit to various datasets analyzed in the study. Correlations between the predicted values of various response variables in the second season dataset based on the path coefficients of the first season were high, except for ear length and number of kernels per row. The applicability of the model has been confirmed through analysis of two additional datasets during 2000. The results indicated the utility of the sequential path model for determining the interrelationships among grain yield and related traits in maize.
Nutritive Value of Chicory and English Plantain Forage
Authors: Sanderson Matt A. , Labreveux Maria , Hall Marvin H. , Elwinger Gerald F.
Published: July 2010

Forage production in midsummer is a challenge for graziers in the northeastern USA. Domesticated cultivars of chicory (Cichorium intybus L.) and English plantain (Plantago lanceolata L.) are available in the USA as perennial herbs for pastures. These species have been touted as having good summer production and relatively high nutritive value. We conducted two field‐plot experiments at Rock Springs, PA, during 1997 to 2001 to evaluate the nutritive value of chicory and plantain under clipping. ‘Grasslands Puna’, ‘Lacerta’, and ‘Forage Feast’ chicory and ‘Ceres Tonic’ and ‘Grasslands Lancelot’ grazing plantain were sown in field plots in May 1997 and 1999 and harvested multiple times in 1998 (Exp. 1) and 2000 (Exp. 2). Herbage from three harvests in 1998 and two harvests in 2000 was analyzed for in vitro true digestibility (IVTD); neutral detergent fiber (NDF); and the minerals P, K, Ca, Mg, Mn, Cu, B, and Zn. Averaged for cultivars, chicory had 11% higher (P < 0.05) IVTD and 6 to 20% lower (P < 0.05) NDF than plantain. Concentrations of all minerals, except for Ca, were 17 to 48% higher (P < 0.05) in chicory than in plantain. There were few meaningful differences in nutritive value among cultivars within chicory or plantain. Chicory and plantain are of relatively high nutritive value and could enhance the nutritional profile of mixed species pastures. The nutritive value benefits, however, must be balanced against the lack of persistence of chicory and plantain.
Sulfur Assimilation in Soybean
Authors: Chronis Demosthenis , Krishnan Hari B.
Published: July 2010

Soybean [Glycine max (L.) Merr.] is a good protein source for both humans and livestock. However, soybean seed proteins are deficient in the sulfur‐containing amino acids cysteine and methionine. This deficiency has stimulated efforts to improve the amino acid composition of soybean seed proteins. Our overall goal is to improve the sulfur amino acid content of soybean seed proteins by genetic manipulation. The objective of this study was to isolate and characterize O‐acetylserine (thiol) lyase (OAS‐TL), a key enzyme that catalyzes the last step in the production of cysteine. A full‐length cDNA clone encoding a cytosolic isoform of OAS‐TL was isolated by screening a soybean seed cDNA library with a 32P‐labeled expressed sequence tag (EST). Nucleotide sequence analysis of the cDNA revealed a single open‐reading frame of 978 base pairs (bp) encoding a 34‐kDa protein. The authenticity of the isolated cDNA was confirmed by the functional complementation of an Escherichia coli cysteine auxotrophic mutant. Reverse transcriptase polymerase chain reaction (RT‐PCR) analysis revealed that OAS‐TL mRNA was abundant at early stages of seed development. Western blot analysis using antibodies generated against the recombinant soybean OAS‐TL demonstrated that the abundance of this protein gradually declined during later stages of seed development. The OAS‐TL activity peaked in young developing seeds and declined steadily during the time period when the bulk of seed storage protein accumulation occurred. Thus, elevating the specific activity of OAS‐TL during later stages of seed development could lead to an increase in cysteine synthesis in soybean seeds.
Additional Sources of Soybean Germplasm Resistant to Two Species of Root‐Knot Nematode
Authors: Harris Donna K. , Boerma H. Roger , Hussey Richard S. , Finnerty Steven L.
Published: July 2010

Root‐knot nematodes (Meloidogyne spp.) can significantly reduce seed yield in soybean [Glycine max (L.) Merr.]. Identification of soybean germplasm with unique genes for resistance to root‐knot nematodes would allow development of cultivars with high levels of resistance. The objective of this study was to identify additional sources of resistance to root‐knot nematodes. We evaluated 608 recently imported soybean PIs from the southern provinces of the People's Republic of China for resistance to M. incognita (MI) and M. arenaria (MA). After three sequential levels of greenhouse screening, seven resistant PIs were identified for MI and seven for MA. In a fourth screening level to determine their level of resistance, PI 594753A and PI 594775A had MI gall resistance equal to the highly resistant check PI 96354. Three other PIs had more galls than PI 96354, but produced fewer galls than ‘Haskell’, the resistant check. However, the numbers of MI eggs produced on PI 594753A and PI 594775A were equal to the highly susceptible ‘Bossier’. The MA screening identified PI 594427C and PI 594403 with the same number of galls as the resistant check Haskell, but they had more galls than the highly resistant PI 200538. The number of MA eggs produced by PI 594427C was equal to the highly resistant check PI 200538, and PI 594403 produced fewer eggs per plant than PI 200538. These new sources of MA resistance may possess previously unidentified genes.
Introduction of Australian Diploid Cotton Genetic Variation into Upland Cotton
Authors: Ahoton L. , Lacape J.‐M. , Baudoin J.‐P. , Mergeai G.
Published: July 2010

Genetic barriers often prevent exploiting diploid cotton germplasm for the improvement of tetraploid cotton. The objective of this study was to investigate mating schemes to achieve introgression of Gossypium sturtianum J.H. Willis and G. australe F. Muell diploid cottons into tetraploid G. hirsutum L. Gossypium hirsutum × G. sturtianum and G. hirsutum × G. australe hexaploids were backcrossed to G. hirsutum to produce BC1 pentaploids and BC2 and BC1S1 euploid and aneuploid plants. The use of G. hirsutum × G. australe pentaploids as male parent in backcrosses with G. hirsutum allowed the production of an important progeny of BC2 self fertile plants that were euploid or carried one chromosome of G. australe in addition to the 52 chromosomes of G. hirsutum The only two BC2 fertile plants issued from G. hirsutum × G. sturtianum hybrids were monosomic addition materials. Both of them were obtained with the pentaploid as female parent in the backcross to cv. Stam F. These results confirm that cotton male gametes are more limited than female gametes in the number of supernumerary chromosomes they can carry. This provides a means of developing alien monosomic addition lines in the G. hirsutum background from all the diploid species of Gossypium whose chromosomes do not carry genes preventing their individual male transfer. The analysis of the monosomic addition plants produced from the G. hirsutum × G. australe hexaploid with simple sequence repeat (SSR) markers allowed us to distinguish seven lines carrying different single chromosomes of G. australe These lines constitute valuable materials with which to carry out fundamental and applied genetic investigations.
Shade and Airflow Restriction Effects on Creeping Bentgrass Golf Greens
Authors: Koh K. J. , Bell G. E. , Martin D. L. , Walker N. R.
Published: July 2010

Creeping bentgrass (Agrostis stolonifera L.) golf greens are often shaded by trees and surrounded by shrubs or brush that restrict airflow. The objective of this study was to compare and independently evaluate turfgrass responses to light reduction and airflow restriction in ‘L93’ and ‘SR1020’ creeping bentgrass. Artificial structures (122 by 122 cm) were assembled from polyvinyl chloride (PVC), and covered with black, woven polyester shade cloth (80% light reduction) to provide treatment effects. Shade cloth was applied to the structures to reduce irradiance and allow airflow or reduce airflow and allow irradiance. Plots were rated monthly for canopy, soil, and air temperature, visual color, density, and disease, soil moisture, root mass, and root glucose and fructose. Canopy and soil temperatures were lower in shade than in airflow restriction and uncovered, unsurrounded control turf. Canopy temperature was higher in airflow restriction than control but soil temperatures did not differ. Both shade and airflow restriction had a negative effect on turf color in L93. Airflow restriction caused a greater reduction in mean color rating than shade in SR1020 but shade color did not differ from control. Turf density declined in both cultivars due to both airflow restriction and shade compared with control. Air restriction reduced density more than shade in SR1020 but not in L93. The severity of brown patch (caused by Rhizoctonia solani Kühn) and dollar spot (caused by Sclerotinia homoeocarpa F.T. Bennett) in shade was less than in airflow restriction in both cultivars and less than control in SR1020. Soil moisture did not differ among treatments. Root mass was affected by both shade and airflow restriction in both cultivars and declined more rapidly in shade than in airflow restriction. Root glucose and fructose were not significantly affected by treatments.
Growth and Complexity of White Clover Stolons in Response to Biotic and Abiotic Stress
Authors: Sanderson M. A. , Byers R. A. , Skinner R. H. , Elwinger G. F.
Published: July 2010

White clover (Trifolium repens L.) persists in pastures mainly by stolon growth. Morphologically complex (i.e., highly branched stolons) plants of white clover generally persist longer. We hypothesized that biotic and abiotic stresses limit white clover production on grazing lands by fragmenting plants into smaller, less competitive individuals. We measured changes in the size and structure of plants in a white clover–orchardgrass (Dactylis glomerata L.) sward during a drought (1999) and a favorable growing season (2000) in grazed pastures on a southeastern Pennsylvania farm. A natural infestation of clover root curculio [Sitona hispidulus (Fabricus)] and blue clover weevil [Ischnopterapion virens (Herbst)] provided an opportunity to examine the interaction of abiotic and biotic stress on stolon structure. White clover plants were dug from two orchardgrass (‘Pennlate’)–white clover (‘Will’) pastures during April to November 1999 and 2000. Stolon structure and damage from blue weevil and curculio larvae were determined monthly. Drought in 1999 reduced stolon production, branching, and rooting in white clover. Stolon length (cm m−2) in 1999 was 50% of that in 2000. Clover root curculio damaged up to 25% of clover roots and 20 to 40% of stolons were damaged by weevils. Insect damage was greatest on primary stolons. With favorable rainfall during late 1999 and in 2000, white clover recovered from fragmentation and produced nearly twice the stolon length, mass, and density in the next grazing season despite insect damage levels of 10 to 30%. Climate and biotic stresses are the major factors controlling oscillations of white clover stolon density in pastures of the northeastern USA.
Cultivar × Environment Interactions in Switchgrass
Authors: Casler M. D. , Boe A. R.
Published: July 2010

Switchgrass (Panicum virgatum L.) is a widely adapted warm‐season perennial that has potential as a bioenergy feedstock. The objectives of this study were to estimate the effect of harvest date on switchgrass cultivars at two locations in the north central USA and to determine the relative importance of cultivar × environment interactions for agronomic and biofuel traits of switchgrass. Six switchgrass cultivars were grown in southern Wisconsin and eastern South Dakota for 4 yr and harvested each year at three harvest dates (August, September, and October). Cultivars differed widely in biomass yield, but interacted with all environmental factors. Biomass yield did not respond consistently to harvest date, varying with cultivar, location, and year. Despite these interactions, cultivar rankings for biomass yield was consistent across harvest dates and years, but not locations. There was some preferential adaptation to either Wisconsin or South Dakota, related to longitude of the original germplasm collection site, also reflected by ground cover data. Reduced stands and biomass yields for the August harvest date in later years suggested that harvests delayed to late summer or early autumn may be beneficial in the long term. Mean dry matter, forage fiber, and lignin concentrations also varied among cultivars, consistently across locations and years. These three traits all increased with later harvest consistently across locations and years, but inconsistently among cultivars. It should be possible, through selection and breeding, to develop switchgrass germplasm with increased fiber and decreased lignin and ash, increasing the availability of fermentable sugars and decreasing the unfermentable and/or incombustible residues.