bluuebunny/crossref_metadata_2025 huggingface dataset:
Labeled‐Nitrate Assimilation and Nitrogen‐15 Export from Leaves of Burley Tobacco
Authors: MacKown C. T.
Published: July 2010

At harvest, burley tobacco (Nicotiana tabacum L.) leaves frequently contain undesirably high levels of NO3, which are usually greater in older leaves lower in the canopy than in the younger leaves of the upper canopy. Substantial NO3 uptake occurs during the 4‐ wk period between topping (apical bud removal) and harvest. To evaluate N use characteristics of leaves differing in stalk position during this period, the 4th or 10th leaf from the top of field‐grown plants received 15N‐NO3 solution (99 atom % 15N). The 15N‐NO3 was fed to one half of the leaf through a lateral vein in the middle of the leaf. Plants were sampled 1, 3, and 7 d later and separated by leaf position for N analysis. Xylem exudate was collected from the base of the plant at 3 and 7 d after labeling. The 15N‐NO3 was readily reduced at both leaf positions. Reduced 15N accumulation by the uppermost three leaves and stalk was greater in plants fed 15N‐NO3 at the 10th leaf than at the fourth leaf position; however, the amount accumulated was small relative to the amount of reduced 15N retained in labeled leaves. Reduced N in the xylem exudate of plants fed 15N at either leaf position was enriched to 0.16 and 0.078 atom % 15N excess at 3 and 7 d, respectively. These results indicate that, after topping, both upper‐ and mid‐canopy leaves had similar NO3‐reduction capacities and a portion of the newly reduced N was cycled through the root system. Differences in leaf NO3 accumulation may be related to greater N supply and uptake during early plant growth rather than to differences in NO3 assimilation potential of leaves late in the season.
Water‐Use Efficiency and Carbon Isotope Discrimination in Wheat
Authors: Ehdaie B. , Hall A. E. , Farquhar G. D. , Nguyen H. T. , Waines J. G.
Published: July 2010

Drought stress is one of the most limiting factors to crop production in semiarid regions. Improved water‐use efficiency (WUE) could provide breeding programs with a means to improve adaptation to drought‐prone environments. Carbon isotope discrimination (Δ) has been proposed as a criterion to select for improved WUE. This study evaluates differences in total dry matter (TDM), WUE (TDM/transpiration), and Δ of flag leaves of landrace and modern wheat (Triticum aestivum L.) genotypes grown in pots in a well‐watered (wet) and in a drought‐stressed (dry) experiment for 2 yr. The wheat genotypes were also grown in wet and dry field conditions. In the pot experiments, average WUE of the genotypes varied from 2.85 to 4.41 g dry matter kg−1 water in the wet experiment and from 3.08 to 4.53 in the dry experiment. The mean values of Δ were 21.7 ✕ 1O−10 for the wet pot experiment and 21.6 ✕ 10−3 for the dry pot experiment. The tall landrace genotypes had greater TDM and WUE, but were later in maturity than the modern dwarf and semi‐dwarf genotypes. Values of Δ associated with different genotypes were negatively correlated with WUE. Broad‐sense heritabilities for WUE and Δ were 93 and 90%, respectively, in the pot experiments. In the dry field experiments, Δ was positively associated with above‐ground dry matter and grain yield in both years. In the wet field experiments, there was a positive correlation between Δ and grain yield only in 1988. Broad‐sense heritabilities for Δ were 72% for wet field conditions and 74% for dry field conditions. These observations indicate that selection for C isotope discrimination, under either wet or dry conditions, can improve water use efficiency in wheat.
Digestibility of Structural Carbohydrates in Cool‐Season Grass and Legume Forages
Authors: Buxton D. R. , Brasche M. R.
Published: July 2010

Structural carbohydrates of forages are not completely digestible by ruminants. The nature of the limitation and interrelationships among digestibility of structural carbohydrates are poorly understood. This field study was conducted to determine digestion kinetics of cell‐wall carbohydrates to better understand these interrelationships. Leaves and stems of alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), smooth bromegrass (Bromus inermis Leyss.), and orchardgrass (Dactylis glomerata L.) were sampled in late May, and stems were again sampled 6 wk later. Plant samples were incubated in buffered rumen fluid for 0, 6, 12, 24, 48, and 72 h, and digestion kinetics were determined for neutral‐detergent fiber (NDF) and cell‐wall carbohydrates. Potentially digestible cellulose as a proportion of total cellulose decreased to a greater extent with age in grass (53%) than in legume (22%) stems. Hemicellulose often was more digestible than cellulose. However, cell‐wall glucose, the principal component of cellulose, was more digestible than xylose, the principal component of hemicellulose. Conversely, the remaining neutral sugars associated with hemicellulose generally were more digestible than glucose. Xylose had the lowest digestibility of the neutral sugars, which was as low as 17% in legume stems. Arabinose digestibility was >60%, even in highly lignified stems, suggesting that not more than a small portion is bonded to lignin. Across plant parts, a close relationship existed between glucose and xylose digestibilities with coefficients of determination of 0.94, suggesting that they may mutually limit each other's digestibility. With stem aging of grass, NDF rate of digestion was reduced from 0.076 to 0.042 h−1 by a decrease in hemicellulose rate of digestion from 0.146 to 0.060 h−1.
Geographical Patterns of Variation in the USDA Soybean Germplasm Collection: I. Morphological Traits
Authors: Perry M. C. , McIntosh M. S.
Published: July 2010

In order to use, maintain, and increase germplasm collections efficiently and effectively, it is important to characterize the diversity of the collection. Our objective was to describe phenotypic diversity of a large sample (2250 accessions from 78 countries) of the USDA soybean [Glycine max (L.) Merr.] germplasm collection. Accessions were characterized for 17 morphological traits to determine variation within and among geographical regions. Phenotypic variation was found within all regions for most characters. The Shannon‐Weaver diversity index was relatively even across regions, bet varied widely among characters scored. Canonical discriminant analysis and clustering of the canonical means delineated four regional clusters: (i) India and Africa; (ii) China, Europe, New World, and Southeast Asia; (iii) Korea and Japan; and (iv) Southwest Central Asia. clusters containing the Korean and Chinese accessions were the most diverse. Based on the diversity and number of accessions, Africa, India, and Southeast Asia seem underrepresented in the collection.
Genotypic Differences in Cotton Root Penetration of a Compacted Subsoil Layer
Authors: Kasperbauer M. J. , Busscher W. J.
Published: July 2010

Roots able to penetrate through compacted subsoil might result in better use of soil water. This study was conducted to determine whether roots of cotton (Gossypium hirsutum L.) genotypes differ in ability to penetrate through compacted soil and, if so, to develop a system for early identification of superior rooting. Sixteen genotypes were compared without irrigation in Norfolk loamy sand (fine‐loamy siliceous, thermic Typic Kandiudult) overlying a compacted subsoil layer near Florence, SC. Some remained turgid, while others wilted. Roots of the turgid genotypes penetrated the compacted layer, whereas few roots of the wilted genotypes did. One line that remained turgid and one that wilted in the field were then studied over artificially compacted soil cores. Roots of the turgid (but not the wilted) genotype penetrated bulk densities of 1.4 g cm−3. Artificially compacted cores can provide a tool to evaluate genotypes for root penetration as an early part of cultivar development for sandy soils that overlie compacted subsoil.
Nuclear and Cytoplasmic Control of Anther Culture Response in Wheat: II. Common Wheat ✕ Alloplasmic Lines
Authors: Ekiz Hasan , Konzak C. F.
Published: July 2010

This study was conducted to evaluate the roles of nuclear and cytoplasmic gene control of anther culture responses in wheat, Triticum aestivum L. Two groups of reciprocal crosses were used; One, between alloplasmic lines of T. aestivum L. cultivars Selkirk, Siete Cerros 66, and Penjamo 62 and other T. aestivum cultivars; and the other, between several alloplasmic lines and their nucleus‐donor cultivars. Anther donor plants were grown in a greenhouse. Anthers were placed on liquid potato‐4 medium for callus induction, and calli were transferred to agar solidified 190‐2 media for plant regeneration. Significant reciprocal differences were observed in both groups for all components of anther culture response. Most differences were for callus induction. Reciprocal differences were considered due to cytoplasmic effects rather than maternal effects based on earlier studies. Reciprocal differences observed for one cross of an alloplasmic line and its nuclear donor source indicated that selection of nuclear genes favoring compatibility with the alien cytoplasm had occurred during the backcross process by which the alloplasmic lines were developed. However, in two combinations, heterosis due to nuclear genetic interactions was observed. The results provide substantial supporting evidence for cytoplasm and cytoplasm ✕ nuclear genetic controls of the response of wheat genotypes to anther culture.
Predicted and Actual Yield and Nitrogen Concentration of Alfalfa in Different Nitrogen Environments
Authors: Teuber L. R. , Phillips D. A. , Geng S. , Lehman W. F.
Published: July 2010

Glasshouse studies with alfalfa (Medicago sativa L.) have shown that improving both forage dry weight (DW) and N concentration (NC) requires selection under N2‐ and NH4NO3‐dependent conditions. The objectives of the present study were to (i) determine genetic variances of forage DW and NC in the field under different levels of N fertilization, (ii) use the genetic variances to predict selection gain for DW and NC at each level of N, (iii) select for increased DW and NC under field conditions and compare actual gains with predicted values, and (iv) compare the efficiencies of field and glasshouse selections for DW and NC. Twenty‐five randomly chosen half‐sib families from ‘Moapa 69’ were planted in each of 2 yr at four locations using a split‐plot design with four levels of N fertilizer (0, 33, 66,100 kg N ha‐1). Forage DW and NC of plants were measured at each location, and individual plants were selected at one location for both DW and NC in each N level using independent culling levels. Genetic variance and predicted gain per cycle for DW were maximized with 100 kg N ha‐1 (118 g kg‐1), while those for NC were greatest without N fertilizer (64 g kg‐1). Selection for either DW or NC alone under these N levels predicted negative correlated responses in the unselected character. Theoretical selection response using independent culling levels for DW followed by NC was greatest under the 33 kg N ha‐1 fertilization level (197 g kg‐1 and 61 g kg‐1 per cycle, respectively). Results of actual selection tests agreed closely with predicted gains and indicate that effective selection for forage DW and NC can be conducted in the field with a low level of N fertilization.
Genetics of Resistance to Verticillium Witl in ‘Vertus’ Alfalfa
Authors: Miller P. R. , Christie B. R.
Published: July 2010

It is difficult to bread alfalfa (Medicago sativa L.) cultivars with >50% resistance to Verticillium albo‐atrum Reinke & Berthier. The objectives of this study wre to determine if selecion for resistance to V. albo‐atrum within the alfalfa cultivar Vertus reduces general combining ability (GCA) compared to specific combining ability (SCA) and to compare disease evaluation in a controlled environment based on foliar symptoms and stem colonization. Two populations of Vertus were studied, one selected on the absence of foliar symptoms after repeated inoculation, the other selected at random. Correlations between stem colonization and foliar symptoms in both populations were low. Seedling height, stem colonization, and first and second‐regrowth foliar symptoms were analyzed for GCA and SCA. Estimates of GCA variances for these characters were three to five times greater in the random population than in the resistant population. Estimates of SCA variances were similar for both populations, with one exception. Estimated GCA/SCA ratios were 4.7:1 and 5.0:1 for foliar symptom evaluation of two regrowth periods in the random population. Corresponding estimated GCA/SCA ratios in the resistant population were 2.9:1 and 1.9:1 This suggests that additive genetic variance will provide limited improvement of resistance levels and nonadditive genetic variance will not be a source of higher levels of resistance to verticillium wilt in this cultivar.
Laboratory and Field Resistance to the European Corn Borer in Maize Germplasm
Authors: Reid L. M. , Arnason J. T. , Nozzolillo C. , Hamilton R. I.
Published: July 2010

There is a continuing need to screen maize (Zea mays L.) germplasm for sources of resistance to the European corn borer, Ostrinia nubilalis (Hübner). This study was conducted to determine the resistance characteristics to a univoltine strain of the European corn borer of six groups of maize germplasm and to examine the relationship among resistance characteristics. The groups of germplasm consisted of (i) a latitudinal series of inbred lines; (ii) a set of the indigenous landraces of Mexico; (iii) two Argentina landraces; (iv) two inbred lines used as controls. In addition, a multiple borer resistance population was studied. All germplasm was evaluated for seedling DIMBOA [2,4‐dihydroxy‐7‐methoxy(2H)‐1,4‐benzoxazin‐3(4H)‐one] content, susceptibility to leaf‐feeding (both laboratory and field) and to stalk tunneling by the European corn borer, susceptibility to Gibberella zeae (Schwein.) Petch (stalk rot) and Ustilago zeae (Beckm.) Unger (corn smut), and their ability to mature in the climatic conditions prevailing at Ottawa, ON. The inbred lines were characterized by high resistance to leaf feeding, but susceptibility to stalk tunneling, whereas the indigenous Mexican land races found among the various parameters, including validation of the relation of seedling DIMBOA levels and laboratory leaf‐feeding test with the field resistance to European corn borer. This study confirms the importance of examining broad groups of germplasm when searching for sources of resistance to the European corn borer.
Quality Characteristics of the Langdon Durum‐dicoccoides Chromosome Substitution Lines
Authors: Joppa L. R. , Hareland Gary A. , Cantrell R. G.
Published: July 2010

The introduction of genes from wild relatives of wheat Triticum aestivum L. em. Thell., can improve certain quality characteristics such as grain protein content, but these alien genes may affect some of the desirable quality traits. The objective of this study was to determine the chromosomal location of genes affecting quality traits of the ‘Langdon’ durum T. turgidum L.‐ T. turgidum var. dicoccoides chromosome substitution lines. Each chromosome of var. dicoccoides was represented by five substitution lines and 13 of the 14 chromosomes were included, for a total of 65 lines. The substitution lines, the recurrent parent Langdon, and three check cultivars were grown in replicated field experiments at two locations in 1989. The quality evaluation included kernel, milling, semolina, and spaghetti characteristics. Differences between lines were significant for all traits studied. Dicoccoides chromosomes 3A and 3B produced semolina high in specks. The substitution lines and Langdon were deficient for yellow pigments in the semolina and in the spaghetti. Several substitution lines had significantly more pigment than Langdon, but none were equal to the other check cultivars. The dicoccoides 6B chromosome substitution lines were superior to Langdon for semolina protein content, mixogram score, spaghetti firmness, cooked weight, and cooking residue. The 1B substitution lines were equal to Langdon in protein, but were superior for traits associated with strong gluten.
Inheritance of Male‐Sterile Mutant ms13 in American Pima Cotton
Authors: Percy Richard G. , Turcotte E. L.
Published: July 2010

Morphological mutants of cotton (Gossypium spp.) have been used extensively as markers in genetic mapping studies and in several instances have proven usedul in agronomic improvement efforts. This investigation was conducted to determine the inheritance, allelism, and linkage associations of a spontaneous, male‐sterile mutant found in plants of American Pima (G. barbadense L.) cotton. Analyses of F1, F2, and BC populations of the mutant indicate that it is inherited as a single, recessive gene. Tests for allelism of the new gene with three previously descirbed recessive male‐sterility genes (ms1, ms2, crosses to 23 mutant marker stocks produced no evidence of linkage associations. Expression of the new male sterility gene was stable and complete in the field and greenhouse environemtns of Maricopa, AZ. We propose that the male sterility mutant be designated male sterile‐13 and be given the gene symbol ms13.
Water Status Measurements of Excised Wheat Leaves: Position and Age Effects
Authors: McCaig T. N. , Romagosa I.
Published: July 2010

The ability of excised leaves to retain water has been implicated as an indicator of drought resistance, and considerable genetic diversity exists for this characteristic; however, genotypic differences are often not consistent throughout the growing season and are confounded by maturity differences. The objectives of this study were to determine the specific effects of leaf position and age on water status measurements of excised leaves and assess the potential relevance to sampling in a large‐scale breeding program. Initial water content (IWC) (kg H2O kg‐1 dry wt.) at the time of excision and rate of water loss (RWL) ( g H2O kg‐1 dry wt. min‐1) following stomatal closure were measured on leaves of four tetraploid wheat (Triticum turgidum L.) genotypes grown in two controlled‐environment experiments. Genotypic differences in RWL were more pronounced at early growth stages and were more consistent between experiments than were differences in IWC. The RWL of leaves 3, 4, and 5 of ‘Hercules’ and ICD1385 underwent considerable fluctuations during aging; the RWL for ‘Pelissier’ and ICD 2627 leaves were low and much more constant during leaf maturation. The flag leaves did not display the same fluctuations in RWL as were evident in the earlier leaves. Higher specific leaf weights (SLW) of flag leaves were responsible for lower RWL values of flag leaves compared to earlier leaves. Genotypic differences and fluctuations of RWL associated with leaf aging could not be attributed to differences in SLW. Decreasing RWL associated with higher leaf insertion levels and changes in RWL associated with leaf aging may lead to misclassification of genotypes unless considerable care is exercised during sample selection. It is suggested that RWL may be influenced by reversible changes in the leaf surface associated with aging.
Avenin Banding Pattern Variation in Tissue Culture‐Derived Oat Lines
Authors: Dahleen L. S. , Rines H. W. , Stuthman D. D.
Published: July 2010

Plant tissue culture generates genetic variation in crop plants. Biochemical variation from culture has not been examined in oat (Avena sativa L.) regenerants. The objectives of this study were to examine avenin (prolamine) variation in R5 generation oat lines derived from R1 progeny of tissue‐culture regenerated plants (R0) that had no detectable karyotypic aberrations, and to test for associations between avenin and agronomic trait variation. Avenins extracted from seed of 56 R4 ‘Lodi’ lines and 147 R4 ‘Tippecanoe’ lines were separated on horizontal isoelectric focusingels (pH 5‐8). The Lodi lines had no variant patterns. Three variant Tippecanoe patterns were observed. One (V1) was identified as the probable product an outcross and two as culture‐generated variant patterns. Variant V2 was found in one line and had a new band at pI 7.85. The third variant (V3) was found in 23 of the 147 Tippecanoe lines and occurred in regenerants from three independent embryo‐derived cultures. Two‐dimensional gel electrophoresis indicated that one of the band differences in these variants came from production of a new 27‐kDa protein. The 23 lines with the V3 avenin variant pattern were further characterized by agronomic trait comparisons. These V3 lines were shorter and later than controls, had increased seed weight, seed number, grain yield, and bundle weight, and they had decreased seed protein and flag leaf area. These results indicate that biochemical variation is generated in oat tissue cultures and that some variant types occur at high frequencies. Avenin banding pattern evaluation should be useful in identifying the products of outcrosses and may provide molecular markers for agronomic traits.
Polymerase Chain Reaction Used for Monitoring multiple Gene Integration in Agrobacterium‐Mediated Transformation
Authors: Blake Nancy K. , Ditterline Raymond L. , Stout Richard G.
Published: July 2010

Characterizing plants following Agrobacterium‐mediated transformation has become an important consideration in the creation of transgenic plants. As an alternative to Southern blot analysis, polymerase chain reaction (PCR) was used to screen for the simultaneous integration of two foreign genes for neomycin phosphotransferase II (NFT II) and β‐glucuronidase (GUS) in alfalfa (Medicago saliva L.) transformed with Agrobacterium tumefaciens. We were able to distinguish between plants that contained only the NFT II gene and those that had both the NFT II and GUS genes. Of our putative transformants selected on kanamycin, 28% contained only the NFT II gene and apparently had lost the GUS gene during the transformation process. Requiring only nanogram amounts of DNA, PCR provided a rapid method to determine which genes had been integrated to our putative transformants much earlier in the plant regenerative process than was feasible by Southern analysis.
Correlation between Water‐Use Efficiency and Carbon Isotope Discrimination in Diverse Cowpea Genotypes and Isogenic Lines
Authors: Ismail Abdelbagi M. , Hall A. E.
Published: July 2010

Breeding cultivars with improved water use efficiency (WUE = total biomass production/water use) has been limited by the lack of suitable screening criteria. Theory has predicted an association between WUE and Δ (leaf discrimination against 13C) that could be used in indirect selection for WUE in C3 plants. Several studies have provided empirical evidence supporting this theory but with some exceptions. Earlier studies showed genotypic and drought‐induced variation in Δ in cowpea (Vigna unguiculata (L.) Walp.) and expected associations with leaf gas exchange for drought‐induced effects but not for genotypic effects. Studies were conducted to evaluate directly the association between seasonal WUE and Δ in cowpea. Five contrasting genotypes and two isogenic lines were grown in the field either in pots or under natural soil conditions and subjected to well‐watered or drought treatments. Genotypic rankings for Δ in leaves were consistent in the wet and dry pot and natural soil conditions. Seasonal WUE was measured in the pot‐experiments. Significant genotypic and drought‐induced effects on WUE were found, and drought increased WUE by 29% due to biomass being reduced less than water use. Total genotypic variation in WUE was 19 and 23% under wet and dry conditions, respectively, and was not associated with differences in plant vigor. Significant genotypic and drought‐induced effects on Δ were present which were strongly correlated with WUE in a manner expected based on theory; Δ should therefore be useful for indirectly selecting genotypes with greater WUE.
Performance of Obsolete and Current Cultivars and Pee Dee Germplasm Lines of Cotton
Authors: Culp T. W. , Green C. C.
Published: July 2010

Yield and fiber quality comparisons of modern vs. obsolete cultivars and Pee Dee (PD) germplasm lines represent a measure of genetic gain for these traits and can be used to establish a base for estimating future breeding accomplishments. We evaluated 29 commercial cultivars and PD germplasm lines of cotton (Gossypium hirsutum L.), 12 modern and 17 obsolete, in two tests per year for a 3‐yr period (1979, 1980, 1981). The soils were a Norfolk fine sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudult) and a Norfolk loamy sand at Florence, SC. We sought to determine what genetic improvements the new cultivars and germplasm lines had compared with the obsolete ones. Two modern cultivars, McNair 235 and SC‐1 (a PD cultivar with extra fiber strength genes) produced 399 kg ha−1 more lint than the obsolete cultivar, Earlistaple 7, and 522 kg ha−1 more than the PD germplasm Line F. The rate of gain in yield of modern compared with obsolete cultivars and PD germplasm lines was 10.5 and 15.1 kg ha−1 yr−1, respectively. The actual rate of gain in related PD germplasm lines was 20.6 kg ha−1 yr−1. A regression analysis of the average yields in South Carolina and the South Atlantic states from 1961 through 1987 showed that yields have significantly increased at the rate of 8.0 and 9.4 kg ha−1 yr−1, respectively. These data show that cotton breeders have made continuous progress in improving lint yield, without sacrificing fiber quality. This trend can be expected to continue. Simultaneous improvements in lint yield and fiber strength can be expected if emphasized in breeding programs.
Natural Selection on Winter Barley Composite Cross XXVI Affects Winter Survival and Associated Traits
Authors: Hensleigh P. F. , Blake T. K. , Welty L. E.
Published: July 2010

Winterhardiness of winter barley (Hordeum vulgare L.) has not been improved greatly during the last 40 yr. Explanations range from a presumed lack of genetic variance for hardiness to a lack of effective selection in winter barley improvement programs. Previous research in Montana utilized recurrent selection in composite crosses containing male sterility to increase genetic recombination and improve winterhardiness. Composite Cross XXVI (CCXXVI) was subjected to winter selection pressure at various Montana locations from 1966 to 1984. This research evaluated the effectiveness of natural selection on winter survival and various agronomic and morphological traits in CCXXVI. Field trials at 10 Montana locations from 1985 to 1987 were used to measure winter survival and agronomic traits. Changes in morphological traits were studied in field and controlled‐environment studies. Natural selection appeared to favor taller and later‐heading plants. No significant change in population grain yield over time was detected in CCXXVI. Natural selection improved winter survival in CCXXVI, but the selection was not uniform over generations and maximum population hardiness occurred midway through the experiment. The hardiest CCXXVI generation was lower in winter survival than a hardy winter wheat (Triticum aestivum L.) and the same as a nonhardy winter wheat and a hardy winter barley cultivar. No significant correlation was found between seedling leaf width, seedling leaf number, or subcrown internode and mean winter survival. Shorter seedling leaf length was associated with enhanced winter survival.
Pollinator Effects on Crossing and Genetic Shift in a Three‐Flower‐Color Alfalfa Population
Authors: Steiner J. J. , Beuselinck P. R. , Peaden R. N. , Kojis W. P. , Bingham E. T.
Published: July 2010

Understanding insect pollinator preference for different alfalfa (Medicago sativa L.) flower colors is important to maintain the genetic composition of plant introductions, germplasms, genetic stocks, and cultivars. This study was conducted to determine whether crossing and the relative proportion of hybrids in a model three‐flower‐color marker system were affected by kind or combination of insect pollinators [honey bees (Apis mellifera L.), leafcutter bees (Megachile rotundata F.), or both bee species combined). A secondary objective was to determine whether actual expression of compatibility between flower color lines, as determined by hand crosses in the greenhouse, was altered by insect pollinator behavior in the field. Noninbred (S0) and slightly inbred (S1) populations of cream‐ (CRM), white‐ (WHT), and yellow‐ (YEL) colored flower markers were grown at Fresno, CA, and Prosser, WA. When self‐ or sib‐pollinated, the flower colors of all parental strains were reproduced, while hybrids among the parental strains produced unique‐colored progeny that allowed determination of the flower color parentage of each line. All pollinator treatments showed similar preferences for flower color (CRM > WHT > YEL) at both locations. Slight inbreeding resulted in more hybrids with WHT seed parents (P ≤ 0.001), and increased hybrid production by CRM and WHT with pollen from YEL (P ≤ 0.06 and 0.08, respectively). Bee behavior altered the proportion of hybrids produced in the mixed flower‐color population from the expected line‐cross compatibility. The location of seed production also interacted with bee preference for CRM and WHT flowers. Level of inbreeding, insect pollinator behavior, and location of production may interact and change the described levels of different flower‐colored lines and result in genetic shifts in plant introductions, germplasms, genetic stocks, and cultivars.
Nonlinear Regression with Variance Components: Modeling Effects of Ozone on Crop Yield
Authors: Gumpertz Marcia L. , Rawlings John O.
Published: July 2010

Split‐plot experimental designs are common in studies of the effects of air pollutants on crop yields. Nonlinear functions such as the Weibull function have been used extensively to model the effect of ozone (O3) exposure on yield of several crop species. The usual nonlinear regression model, which assumes independent errors, is not appropriate for data from nested or split‐plot designs in which there is more than one source of random variation. The nonlinear model with variance components combines a nonlinear model for the mean with additive random effects to describe the covariance structure. We propose an estimated generalized least squares (EGLS) method of estimating the parameters for this model. This method is demonstrated and compared with results from ordinary nonlinear least squares for data from the National Crop Loss Assessment Network (NCLAN) program regarding the effects of O3 on soybean [Glycine max (L.) Merr.]. In this example, all methods give similar point estimates of the parameters of the Weibull function. The advantage of estimated generalized least squares is that it produces proper estimates of the variances of the parameters, estimated yields, and relative yield losses, which take the covariance structure into account. Model selection, hypothesis testing, and construction of confidence intervals are also demonstrated. A computer program that fits the nonlinear model with variance components by the EGLS method is available from the authors.
Competitive Turgor Maintenance in Tall Fescue
Authors: White R. H. , Engelke M. C. , Morton S. J. , Ruemmele B. A.
Published: July 2010

Economical, rapid methods are needed to identify drought‐tolerant turfgrasses. Objectives of this study were to (i) examine water relations of three tall rescue (Festuca arundinacea Schreb.) selections, (ii) determine the relationship between these characteristics and recovery from water deficit under greenhouse conditions, and (iii) assess the feasibility of using a competitive soil moisture extraction technique to select tall rescue germplasm with superior drought tolerance. Three tall rescue selections were vegetatively propagated and grown together in 38‐L weighing lysimeters to allow interplant competition for available soil moisture. Adequate irrigation and fertilizer were applied for 12 wk after planting; irrigation was then withheld for 8 wk. Tiller survival among selections ranged from 2 to 37% and plant survival ranged from 22 to 76% at 4 wk after irrigation was resumed. Survival was associated with low basal osmotic potential before stress and osmotic adjustment, prolonged positive turgor maintenance, and delayed leaf rolling during stress. Leaf rolling scores, and tiller and plant survival during competitive soil moisture extraction were easily assessed indicators of tall fescue germplasm drought tolerance.
Differentiating Soybean Responses to Heterodera Glycines Races
Authors: Schmitt D. P. , Shannon G.
Published: July 2010

Physiological variation among populations of Heterodera glycines Ichinohe, the soybean cyst nematode, has been a problem for soybean [Glycine max (L.) Merr.] growers and scientists. These populations have been classified into 16 races, but the system still leaves ambiguity, especially in the characterization of resistance. Two schemes are proposed: one to classify the nematoder aces and the other to designate the soybean response to the nematode. The existing race system by Riggs and Schmitt still serves as a basis for differentiating populations of H. glycines, but with soybean PI 437654 added as an additional nematode response parameter. A practical system using a popular resistant cultivar as the type for resistance is proposed for advisory purposes. Soybean reactions to parasitism by the nematode are denoted by four levels of resistance: resistant, moderately resistant, moderately susceptible, and susceptible.
Inheritance and Allelism of Mitomycin C‐ and Streptomycin‐Induced Recessive Genes for Male Sterility in Cultivated Sunflower
Authors: Jan C. C.
Published: July 2010

Nuclear male sterility (NMS) conditioned by recessive genes provides a useful tool for sunflower (Helianthus annuus L.) breeding and genetics programs. The objectives of this study were to evaluate seven induced NMS mutants derived from inbred line HA 89 and two lines, B11A3 and P21, for their mode of inheritance, allelic relationships, and agronomic characteristics. Self‐pollinated F2 progenies from heterozygous F1 male‐fertile (MF) plants and BC1F1 progenies from crossing male‐sterile (MS) with F1 heterozygous MF plants segregated in ratios of three MF to one MS and one MF to one MS, respectively, indicating single recessive gene control of male sterility. Half‐diallel crosses of MS with heterozygous F, MF plants indicated that the seven NMS mutant lines represented mutations at four loci that differ from that of P21 or B11A3. Male‐fertile segregates had normal pollen production, as that of HA 89, and MS segregates lacked anther extrusion and pollen production in both field and greenhouse evaluations. B11A3 had a few partially fertile florets at the center of the heads in summer greenhouse plantings, perhaps due to high temperature. The shorter plant height and associated female sterility in NMS 747 (ms8) make it less useful. B11A3 (mslO) and P21 (msll) are agronomically less desirable because of their taller height and lower self‐compatibility. NMS 360 (ms9), 552 (ms7), and 872 (ms6), representing three of the four mutant genes, performed similarly to agronomically adapted HA 89, were completely male‐sterile, and should be considered for use in future genetics and breeding programs as replacements for B11A3 and P21.
Inbreeding Cultivated Alfalfa at the Diploid Level by Selfing and Sib‐mating
Authors: Ray I. M. , Bingham E. T.
Published: July 2010

It has been proposed that inbreeding and selection in cultivated alfalfa (Medicago sativa L.) may increase the frequency of alleles with favorable effects. Inbred lines of cultivated alfalfa at the diploid level (CADL, 2n = 2x = 16) were developed by selfing (S), sib‐mating (SM), and composite S1 sib‐mating (S1SM). Dry matter yield of field grown spaced‐plants from the F1, S1, S2, SM1, SM4, and S1SM3 generations was harvested twice in a single year to determine inbreeding effects and if favorable alleles were accumulated while inbreeding. Plant vigor and fertility declined significantly (P < 0.01) in most advanced generations. Inbreeding depression under selfing was equal to or less than the percent change in the coefficient of inbreeding, F. One family survived five generations of self‐pollination (F = 0.97). Inbreeding depression under sib‐mating often exceeded the percent change in F by as much as twofold. The average rate of inbreeding depression, expressed as the percent change in yield for each percent change in F, was less under selfing (−0.80) than under sib‐mating (−1.91) although exceptions to the general trend did occur. Phenotypic improvement was never noted under exclusive selfing. Two sib‐mated generations tended to outperform earlier, less‐inbred generations, indicating that favorable alleles were accumulated while inbreeding.
Inbreeding and Yield Prediction in Synthetic Maize Cultivars Made with Parental Lines: I. Basic Methods
Authors: Márquez‐Sánchez Fidel
Published: July 2010

Yield of synthetic cultivars is determined by their inbreeding, besides other factors. In turn, the inbreeding depends on the number of parents, their inbreeding, and the coaneestry among them. Previous studies have not considered the number of individuals per parent, which has an effect on the inbreeding of the synthetics and thus on their yield. A method of calculation of the inbreeding coefficient in the first and second generation of a syntheticultivar made with parental lines is presented. The inbreeding coefficients in the two generations vary inversely with n, the number of lines, and m, the number of plants per line. The inbreeding coefficient in the second generation is the same whether the first generation is obtained by intererossing the lines or by randomly mating the plants from a seed bulk of the lines. Thus, the yield prediction of the two synthetic populations is the same. Wright's formula for predicting inbreeding in a synthetic cultivar is valid only when homozygous parents are used either as single plants or as lines. If other factors that determine yield (e.g., gene frequency, imbalance in the crossing in the first and second generations of synthetic development, multiallelism and epistasis) are excluded, then, for the same level of inbreeding, synthetics are expected to yield more when using parentalines than when using individual parental plants.
Selection for Spring‐Habit Clones of Hordeum bulbosum
Authors: Furusho Masahiko , Yoshino Minoru , Yoshida Tomohiko
Published: July 2010

Haploids of barley (Hordeum vulgare L.) can be produced from the interspecificross with H. bulbosum L. Usually, H. bulbosum requires vernalization to produce pollen because of its winter habit. The objective of this study was to select spring‐habit clones of H. bulbosum to facilitate the crossing of H. vulgare with H. bulbosum. The efficiency of embryo formation (number of embryos obtained/number of florets pollinated) and haploid production (number of haploids obtained/number of florets pollinated) of clones selected as spring habit were also evaluated. Twenty‐three out of 183 clones flowered without a vernalization treatment. These clones produced sufficient pollen. Efficiencies were 26.3 to 86.5% for embryo formation and 8.2 to 41.9%, for haploid production, and some clones were superior to a conventional winter‐habit type clone. These clones can be used to improve a barley haploid production program.
Photoperiod, Leaf Number, and Interval from Tassel Initiation to Emergence in Diverse Cultivars of Maize
Authors: Ellis R. H. , Summerfield R. J. , Edmeades G. O. , Roberts E. H.
Published: July 2010

Photoperiod has substantial effects on phenology in many cultivars of maize (Zea mays L.). This study investigated if photoperiod sensitivity ends at tassel initiation (TI) by considering whether photoperiod influences the duration from TI to tassel emergence (TE). In the first experiment, five diverse cultivars were grown in 12 different controlled environments until TI, and were then transferred to either short (11 h d−1) or l ong (16‐18 h−1) days. In the second experiment, these five and seven more cultivars were grown in four different controlled environments until TI, and were then transferred to either short or long days. Leaf numbers per plant were influenced by the photo period experienced before TI (P < 0.01), but not thereafter (P > 0.25); the former effect varied considerably among cultivars (P < 0.01). Durations from TI to TE also differed among cultivars (P < 0.01) and were positively correlated with the photo period experienced after TI (P < 0.01); the effect of a 4 to 7 h d−1 increase varied (P < 0.05) from 0 in some cultivars to > 5 d in others. A significant negative effect of photoperiod before TI on TI to TE duration was also detected (P < 0.01)o This photo periodic response varied among cultivars (P < 0.01) from negligible to a reduction of > 10 d in TI to TE durations for a 5 h d−1 increase in photo period between sowing and TI. Thus, photo period‐sensitive maize cultivars can be affected by photo period after TI in a way that may tend to cancel out the effect on TI to TE duration of the photo period experienced before TI. Assumptions that the photo period experienced after tassel initiation has no effect on the timing of tassel emergence for the purposes of crop modeling or genetic characterization are consequently unlikely to cause serious errors.
Response of Soybean to Inoculation with Efficient and Inefficient Bradyrhizobium japonicum Variants
Authors: Champion Rebecca A. , Mathis James N. , Israel Daniel W. , Hunt Patrick G.
Published: July 2010

Soybean [Glycine max (L.) Merr.] plants are grown in soils containing large indigenous bradyrhizobial populations. Individual strains within these populations differ in symbiotic efficiency and competitiveness for nodule occupancy. The purpose of this study was to determine the effect of mixed inocula of an efficient and an inefficient variant of Bradyrhizobim japonicum on symbiotic performance in soybean. Lee soybean was initially inoculated with either an efficient or an inefficient USDA II0 colony morphology variant. The opposite variant was then applied after 0, 2, 4, 8, or 13 d. Delayed inoculation with the efficient variant following the inefficient variant resulted in progressively decreased symbiotic performance. In a subsequent competition experiment, soybean cultivars Lee and Ransom were inoculated with efficient and inefficient variants at ratios of 1:1, 1:10 and 10:1. More nodules were formed by the efficient variant than were expected by chance. Significantly reduced dry weight and whole plant N contents were noted when the inefficient variant was present in more than 50% of the nodules. Split‐root experiments were conducted and either type of variant was capable of inhibiting the other after a 7‐d delay in inoculation. In contrast, when both sides of the split‐root were simultaneously inoculated, nodule numbers were similar; however, nodules formed by the efficient variant were larger. This increase in size indicated a preferential partitioning of photosynthate to the nodules formed by the efficient variant. These results together indicate that N2 fixation is enhanced with increased nodule occupancy by superior variants due to more effective strain‐cultivar interactions.
Digestion Kinetics of Orchardgrass As Influenced by Leaf Morphology, Fineness of Grind, and Maturity Group
Authors: Lentz E. M. , Buxton D. R.
Published: July 2010

Fine grinding of plant material, as commonly done for forage quality evaluation, may mask effects of variation in plant morphological traits on plant digestibility. Moreover, late‐maturity genotypes are more digestible than early‐maturity genotypes when harvested on the same date, but the reason for this difference in digestibility is not known. This study was conducted to determine if fineness of grind, leaf size, or maturity group affects rate or extent of digestion of orchardgrass (Dactylis glomerata L.). Plants from two maturity groups (anthesis differed by 8 d) were selected for short, long, narrow, or wide leaf blades. Plants were harvested from a field planting on common dates in spring (near anthesis) and summer (after 5 wk of regrowth), and from 5 wk of regrowth in a greenhouse. Stem + sheaths from spring growth, and leaves from summer and greenhouse regrowth were ground to pass an 8‐ or 1‐mm screen. Samples were incubated in rumen fluid, and digestion kinetics determined. Generally, there were no leaf size × fineness of grind interactions, and digestibility of the plant genotypes ranked the same regardless of fineness of grind and leaf size. Variation in digestibility remained the same regardless of grind size. The indigestible residue was 12% greater in leaves and 49% greater in stem + sheaths of early than of late maturing clones. There was no significant difference in digestion rates of leaves from the early and late groups (0.076 and 0.079 h−1, respectively), but stem + sheaths of the early group digested at 0.068 h−1, and those of the late group digested at 0.087 h−1. Therefore, maturity group had a greater effect on digestion kinetics of stem + sheaths than of leaves.
Evaluation of Theory for Identifying Populations for Genetic Improvement of Maize Hybrids
Authors: Pfarr David G. , Lamkey Kendall R.
Published: July 2010

The ability to identify populations with the greatest chance for breeding success may increase the use of unadapted populations by concentration of resources on favorable germplasm. This study was conducted to evaluate the effectiveness of a method (estimates of ′)for identifying maize (Zea mays L.) populations with the greatest number of dominant alleles at loci that are homozygous recessive in a single cross. This study also evaluates the effectiveness of a relationship estimator for detecting similarities between a population and the inbreds of a single cross. Estimates of ′ and the relationship estimator were calculated by using donor populations of known composition and relationship to the recipient single cross. Six recipient single crosses were formed from the diallel cross of maize inbreds B73, B79, B77, and Mo17o Donor populations were composed of various proportions of inbreds B79 and B77. Estimates of ′ correctly identified the population expected to have the largest number of unique dominant alleles in three of five single crosses (60%) for grain yield. for ear height, ′ correctly identified the population expected to have the largest number of unique dominant alleles in four or five single crosses (80%). Estimates of ′ did not identify populations expected to contain dominant alleles for earlier silking, suggesting that additive gene action or epistasis were important for siiking date. The relationship estimator for yield correctly identified the known relationship between the populations and the inbred parents of the single crosses. The successful application of ′ to exotic populations is uncertain because of a low frequency of favorable dominant alleles contained by exotics for important economic traits.
Genes for Resistance to Stripe Rust in ‘Tres’ Wheat
Authors: Chen Xianming , Line Roland F.
Published: July 2010

The genetic basis of stripe rust (Puccinia striiformis Westend.) resistance in the club wheat (Triticum aestivum L.) ‘Tres’ was not previously known. This greenhouse, growth chamber, and field study was conducted to determine the inheritance of resistance in Tres and the relationship of genes for resistance in Tres to genes in other wheat cultivars. Tres was crossed with 20 wheat cultivars with genes Yr1, yr2, Yr3a, Yr4a, Yr4b, Yr5 through Yr10, and 18 other genes for stripe rust resistance not officially named, and with ‘Michigan Amber’, which is susceptible to all identified stripe rust races in North America. Seedlings of parents and F1 and F2 progeny from all crosses, backcrosses of ‘Chinese 166’/Tres, and F3 progeny from Tres/‘Lemhi’ were tested for response to selected races. Genetic analyses showed that Tres has two genes for stripe rust resistance; one was dominant, and the other either dominant or recessive depending on the cultivar crossed with Tres. The results indicate that epistasis is involved in genetic control of the resistance. The two genes for resistance in Tres are different from the 29 genes in the other cultivars. One of the resistance genes in Tres may be allelic or closely linked to a gene in ‘Yamhill’.