bluuebunny/crossref_metadata_2025 huggingface dataset:
Seed Production in Tall Fescue as Affected by Fungal Endophyte
Authors: Rice J. S. , Pinkerton B. W. , Stringer W. C. , Undersander D. J.
Published: July 2010

Relative seed yields should be an important measure of the effects of the endophytic fungus Acremonium coenophialum Morgan‐Jones & Gams on relative fitness in tall fescue (Festuca arundinacea Schreb.). Two field experiments were conducted on Cecil sandy‐loam soils (clayey, kaolinitic, thermic Typic Kanhapuldults) to investigate the effects of endophyte infection on seed production and associated traits. The studies used endophyte‐infected and uninfected clones of the same plant genotypes. In Exp. I and II, endophyte infection resulted in 79 and 32% more total seed by weight, 60 and 33% more seeds per plant, 20 and 34% more panicles per plant, and 32 and 4% more seeds per panicle, respectively. The 300‐seed wt. was greater for infected plants in Exp. I but not in Exp. II. Plant genotype ✕ fungal status interactions occurred for all traits except for seeds per plant and seeds per panicle in Exp. II. These interactions occurred largely because the effect of the endophyte varied from no or small increases to significant increases in trait expression for different plant genotypes. The results indicate that endophyte‐infected tall fescue plants have much higher relative fitness for seed production than uninfected plants. Populations with low fungal incidence could rapidly shift toward high levels of infestation during seed increase or in pastures when seed production is allowed, leading to establishment of volunteer plants.
Tolerant and Root‐Resistant Soybean Cultivars: Reactions to Phytophthora Rot in Inoculum‐Layer Tests
Authors: Thomison P. R. , Thomas C. A. , Kenworthy W. J.
Published: July 2010

Race specificity may be involved in the reactions of certain soybean [Glycine max (L.) Merr.]cultivars previously characterized as tolerant to Phytophthora megasperma f. sp. glycinea Kuan & Erwin (Pmg). The objectives of this study were to determine if an inoculumlayer procedure could be used to differentiate race‐specific reactions among soybean cultivars characterized as tolerant to Pmg and to distinguish root resistance reactions associated with tolerance from those conditioned by the Rps2 gene. An inoculum‐layer procedure was used in the greenhouse to determine the reactions of 21 soybean cultivars to Races 1 and 10 of Pmg. Some cultivars characterized as tolerant to Pmg and the cultivar CNS with the Rps2 gene, which conditions race‐specific root resistance to these Pmg races, were included to provide a comparison between various levels of seedling tolerance and root resistance. Seeds were planted 2.5 or 5.0 cm above an inoculum layer of lima bean agar cultures. Cultivar reaction to Pmg was recorded as percent survival of emerged seedlings 14 d after planting. Cultivars exhibited different levels of survival with Races 1 and 10, with variation also at the 2.5‐ and 5.0‐cm inoculum layer depths. Seedling survival with Race 10 was significantly (P < 0.05) higher at the 5.0‐cm compared with the 2.5‐cm inoculum layer, whereas there was no consistent difference in survival with Race 1 among cultivars at the two depths. Nine cultivars exhibited high levels of seedling survival with Race 1 that were comparable with CNS. Only CNS and 'Emerald' survived both Races 1 and 10. Since the reactions of Emerald closely resemble those of CNS, they may be conditioned by the Rps2 gene. Results of the experiments indicate that it is difficult to distinguish between race‐specific root resistance and high levels of tolerance when using the inoculum‐layer test with certain cultivar/race/inoculum depth combinations. Limited information is available concerning differences in the expression of root infection between cultivars with race‐specific root resistance and those with high levels of tolerance. The results emphasize the need for improved techniques to differentiate tolerance and root resistance, and to characterize precisely soybean lines or cultivars lacking major resistance genes.
Genetics Basis of Resistance in Maize to Five Maize Dwarf Mosaic Virus Strains
Authors: Louie Raymond , Findley W. R. , Knoke J. K. , McMullen M. D.
Published: July 2010

Maize dwarf mosaic (MDM) is a widespread viral disease of maize (Zea mays L.) in the southern U.S. Corn Belt. An understanding of the genetics for resistance to maize dwarf mosaic virus (MDMV) will provide a rational basis for effective selection. Our objective wast o determine the genetic basis of resistance in inbred Pa405 to Strains A, B, D, E, and F of MDMV by examining the association between host symptomr esponses, and chromosomal translocation and morphologicaol r molecularm arkers. Twenty‐six translocation markers and the morphological marker yl were incorporated into inbred MI4. Linkage relationships with molecular markersw ere determinedb y restriction fragment length polymorphism (RFLP) analysis, using molecular markers UMC85, BNL6.29, UMC59a,n d UMC21T. he three approachesa ll indicated a gene or genes on either the short arm or the proximal region of the long arm( proximal to YI) of Chromosom6e i n inbred Pa405 controlling resistance to all five strains of MDMV.
Inheritance of Test Weight and Its Relationship with Grain Yield of Oat
Authors: Pixley K. V. , Frey K. J.
Published: July 2010

Test weight is a measure of grain quality and market value of oat (Avena saliva L.). This study was conducted to evaluate the degree of genetic variability for test weight among elite oat germplasm, and to assess the feasibility of breeding oat cultivars with increased test weight. Variance components and heritability of test weight were estimated by evaluating 50 random F2:3 lines from each of 13 singlecrosses. Evaluations were conducted in a trial with four replications at each of three locations in Iowa. Significant genetic variance (P≤ 0.01) occurred for test weight in all populations. Heritabilities for test weight, calculated on a line‐mean basis, ranged from 63 to 91%. Transgressive segregation occurred in 10 populations, but lowtest‐weight segregates were more frequent than high transgressive lines. High heritabilities, the general concurrence between mating means and midparent values, and normality of the distributions of segregating lines suggest that gene action for test weight is primarily additive. Correlations between test weight and grain yield were positive for eight populations, negative for one, and not significant for four. We found significant genetic variance and high heritability for test weight and grain yield. Because test weight and grain yield were typically positively correlated, breeding high‐yielding oats with improved test weight should be possible.
Russian Wheat Aphid Reaction and Agronomic and Quality Traits of a Resistant Wheat
Authors: Quick J. S. , Nkongolo K. K. , Meyer W. , Peairs F. B. , Weaver B.
Published: July 2010

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has caused significant losses to wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in Canada, Mexico, and the USA during 1986 to 1990. Resistance is not available in adapted cnltivars. We conducted this study to determine levels of resistance to the Russian wheat aphid in 19 wheat, 2 barley, 1 oat (Avena safiva L.), 1 triticale (× Triticosecale Wittmack), and 1 Triticum monococcum L. (einkorn wheat) genotype in greenhouse seedling screening tests. All adapted wheat cultivars and advanced breeding lines and barley cultivars were susceptible. The triticale (TX33000) and T. monococcum (PI 266844) genotypes were moderately resistant, while wheat introduction PI 372129 and ‘Colorado 37’ oat were resistant. Correlations (r) among 7–, 12–, and 17–d rating times for 7 and 24 genotypes in two experiments were highly significant (+0.83 to +0.98). Seedling survival, after RWA removal and with or without 8 wk of vernalization and transplanting, was not correlated with RWA damage ratings. Although vernalization and transplanting reduced survival of most genotypes, survival of PI 372129 seedlings was excellent in both tests. PI 372129 is the first wheat genotype showing significant resistance to the U.S. RWA populations. PI 372129 (‘Turcikum 57’) is an introduction from the USSR and possesses several undesirable traits for a hard red winter wheat breeding program, including late maturity, tallness, weak straw, white grain, and soft milling endosperm.
Moving‐Mean Analysis of Field Tests for Iron Efficiency of Soybean
Authors: Diers B. W. , Voss B. K. , Fehr W. R.
Published: July 2010

Soil heterogeneity reduces the effectiveness of selection of soybean [Glycine max (L.) Merr.] genotypes for Fe efficiency on calcareous soils. A study was conducted to determine if the moving‐mean analysis procedure would reduce the error variance in Fe‐efficiency tests and improve selection among genotypes. Chlorosiscores were obtained from the Iowa Soybean Yield Test (ISYT), which included 620 entries replication−1 in 1987 and 660 entries replication−1 in 1988, and from the Uniform Soybean Test (UST), which included 80 entries replication−1 in both years. The data from the tests were analyzed using an analysis of covuriance in which the eovariate for each plot was the mean of its adjacent plots. The use of the analysis of covariance reduced the error variance for the ISYT by 33% in 1987 and 14% in 1988, and for the UST by 21% in 1987 and 7% in 1988, compared with a conventional analysis of variance (ANOVA). Gains from selection were calculated for selection among entries common to both years in the ISYT by using moving‐mean adjusted and unadjusted entry means. No significant differences (P > 0.05) between the two types of means were obtained for gains from selection. These results show that, although the moving‐mean analysis reduced the error variance, it did not adjust means in a way that would have resulted in improved selection compared with unadjusted means.
Genetic Variability of Seed Yield and Agronomic Characters in Festuca Hybrids and Amphiploids
Authors: Burner D. M. , Eizenga G. C. , Buckner R. C. , Burrus P. B.
Published: July 2010

Wide hybridization is a useful tool for crop improvement, but there is little empirical data concerning effects of amphiploidy on genetic variances of agronomic characters. The objective of this study was to determine genetic variances and broad‐sense heritabilities of seed yield components and winter vigor for sterile F1 hybrids and partially fertile, meiotically unstable amphiploid derivatives. Fifteen reciprocal hybrids (2n = 6x = 42) of giant fescue [Festuca gigantea (L.) Vill.] × tall fescue (F. arundinacea Schreb.), and 75 amphiploid derivatives (2n = 48 to 84), were tested. Amphiploids were chosen from five successive generations of predominantly maternal half‐sib progeny. Entries were clonally propagated, space planted, and evaluated during 2 yr for culm number, culm height, anthesis date, winter vigor score, seed yield per plant, and seed yield per panicle. Amphiploids produced an average of 70% fewer culms plant−1 than F1 hybrids. Mean seed yield of amphiploids (6.5 g plant−1) was markedly less than expected in tall fescue. Seed yield per plant and seed yield per panicle tended to change quadratically with amphiploid generations, but the response was strongly influenced by years. Genetic variances were significant (P < 0.05) for most characters in hybrid and amphiploid populations. Estimates of broad‐sense heritabilities were significant in the amphiploid population and ranged from 46% for seed yield per panicle to 81% for culm height. These results indicate that genetic variation in the amphiploids is probably sufficient for improving agronomic characters; however, aneuploidy might negate potential genetic advance of seed yield.
Resistance to Anthracnose Protects Forage Quality of Alfalfa
Authors: Lenssen A. W. , Sorensen E. L. , Posler G. L. , Stuteville D. L.
Published: July 2010

Anthracnose, caused by Colletotrichum trifolii Bain, decreases forage yield and stand persistence of alfalfa (Medicago sativa L.) throughout much of the USA. Little is known about the effects of anthracnose or host‐plant resistance on forage quality, including phenolic monomer concentrations. In a controlled environment, we compared forage quality, including phenolic monomers, of alfalfa cultivars Saranac (susceptible) and Saranac AR (resistant) with and without anthracnose (Race 1). In the absence of inoculation, leaves of the two cultivars did not differ significantly for any parameter measured. Leaves had more total phenolics than did stems. Forage quality of inoculated leaves of Saranac often was lower than that of inoculated Saranac AR. Inoculated leaves had higher concentrations of the substituted benzoic acids (p‐hydroxybenzoic, vanillic, and syringic) but concentrations of the substituted cinnamic acids (p‐coumaric, ferulic, and sinapic) were not altered by the disease. Forage quality of uninoculated stems of Saranac and Saranac AR differed only for neutral detergent fiber. Conversely, infection of Saranac slowed phenological development of shoots, with a concomitant increase in stem protein and digestibility. Inoculated stems of Saranac, however, had significantly more p‐hydroxybenzoic, and syringic acids, p‐hydroxybenzaldehyde, vanillin, and total phenolics than did stems of inoculated Saranac AR or controls. The presence of resistance to anthracnose in Saranac AR did not affect forage quality, including monophenolic profiles, of uninoculated leaves and stems. Mechanisms of resistance of Saranac AR maintained forage quality of leaves inoculated with C. trifolii.
Lysine and Protein Content of Normal and Opaque‐2 Maize Grain as Influenced by Irrigation and Nitrogen
Authors: Kniep K. R. , Mason S. C.
Published: July 2010

Increasing soil N fertility has been found to have detrimental effects on the nutritional quality of maize (Zea mays L.) grain; however, little research has evaluated the effects of irrigation on these factors. Most previous work has been done with inbred lines rather than high‐yielding commercial hybrids. This study was conducted to determine how irrigation and soil N levels would affect the content of protein and lysine plus the quality of maize protein as measured by the lysine in protein (LP). Two water regimes and five soil N levels were applied to two normal and two opaque‐2 commercial hybrids grown on a Sharpsburg silty clay loam soil (fine, montmorillinitic, mesic Typic Argiudoll). The hybrid ✕ year interaction indicated that in 1985 and 1987 the short‐season opaque‐2 hybrid (SO) had a greater yield than the short‐season normal hybrid (SN) by ≈8%, whereas the long‐season normal hybrid (LN) had a greater yield than the long‐season opaque‐2 hybrid (LO) by 4 to 12%. In 1986, normal and opaque‐2 hybrids produced similar yields. Irrigation increased yield, decreased protein content (PT) 5 to 7 g kg‐1, and increased LP by 1 to 2 g kg−1 in 1985 and 1986. Irrigation also decreased lysine in sample (LS) 0.3 g kg−1 for opaque‐2 grain. Conversely, increasing soil N levels increased yield, PT, and LS, while LP decreased quadratically from 0.39 to 0.36 % kg−1. Grain yield was maximized by production of LN hybrids with irrigation and high soil N levels. The highest PT levels were produced with normal hybrids with high soil N levels without irrigation. Grain produced by opaque‐2 hybrids under low soil N conditions without irrigation had the best protein quality as indicated by LP. Results from the study indicate that both grain yield and nutritional quality are influenced by hybrid selection, irrigation, and N fertilization, which should be considered by producers of nonruminant livestock.
Errors in Forage‐Quality Data Predicted by Near Infrared Reflectance Spectroscopy
Authors: Buxton D. R. , Mertens D. R.
Published: July 2010

Near infrared reflectance spectroscopy (NIRS) is rapidly being accepted for routine prediction of forage quality and chemical constituents. Accurate predictions require calibration with samples analyzed by reference methods. This study was conducted to determine whether deviations between values predicted by NIRS and those determined by conventional techniques are random. In all, 108 samples from the basal 150 mm of immature and mature stems of replicated, field‐grown cultivars of alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), smooth bromegrass (Bromus inermis Leyss.), and orchardgrass (Dactylis glomerata L.) were studied. Residuals were obtained from calibration equations developed on all 108 samples. The overall accuracy with which 12 forage‐quality and chemical traits were predicted by NIRS was similar to that reported in the literature. When residuals were tested by analyses of variance, significant differences were identified. Significant sources of variation were associated with field replicate, year, entry ✕ year interaction, and cultivars within species. Three traits with the most significant deviations were in vitro true digestibility, acid‐detergent fiber, and cellulose, whereas the traits with the least significant deviations were neutral‐detergent fiber, hemicellulose, glucose from the cell wall, and vanillin from nitrobenzene oxidation of core lignin. Unless NIRS results are checked for bias in subsets and verified by conventional analyses, erroneous conclusions can be drawn when NIRS is used to predict for management, physiology, and breeding studies.
Basic Alfalfa Germplasms Differ in Nutritive Content of Forage
Authors: Lenssen A. W. , Sorensen E. L. , Posler G. L. , Harbers L. H.
Published: July 2010

Little information is available regarding comparative forage quality of alfalfa (Medicago sativa L.) leaves and stems of the nine germplasms from which most North American cultivars have been developed. In a greenhouse trial, forage quality of leaves and stems of the nine germplasms was compared when grown in a common environment and harvested at the same phenological stage. Germplasm sources (and representative cultivar) tested were: Indian (Sirsa #9), African (African), Peruvian (Hairy Peruvian), Flemish (DuPuits), Turkistan (Lahontan), Chilean (Kansas Common), M. varia Martin (Grimm), Ladak (Ladak), M. falcata L. (Anik). Leaves of germplasm sources differed for concentrations of neutral detergent fiber, cellulose, crude protein, true in vitro digestible dry matter, and p‐hydroxybenzaldehyde, vanillic, p‐coumaric, ferulic, and sinapic acids. Stems of germplasm sources differed for concentrations of NDF, hemicellulose, CEL, TIVDDM, and p‐hydroxybenzoic, syringic, p‐coumaric, and ferulic acids. Results indicate that alfalfa germplasm sources differ in nutritive value of leaves and stems.
Genotypic Variation in Soybean Nodule Number and Weight
Authors: Sinclair T. R. , Soffes A. R. , Hinson K. , Albrecht S. L. , Pfahler P. L.
Published: July 2010

Environment and genetics influence the process of nodulation in soybean [Glycine max (L.) Merr.]. To select for increased N2 fixation in soybean, plant breeders need to identify those morphological traits associated with the fixation process. The objectives of this study were to classify cultivars (Maturity Groups V through IX) and breeding lines for nodule weight, nodule number, and shoot and root weight at the R3 to R4 stage of development under field conditions in Gainesville, FL. Of the 100 soybean genotypes screened in 1983, 17 were selected for more detailed study in 1984 and 1985. ‘Hardee’, ‘Centennial’ and F81‐7313 ranked among the genotypes with the greatest nodule weight and number; and these rankings were consistent across years and locations tested. Environmental stability analyses showed that those lines with the greatest mean nodule weight also had the greatest positive response to favorable environments. Nodule weight and number were highly correlated traits (r > 0.84). Root and shoot weight had moderately positive correlations with nodule number and nodule weight.
Morphology of Leaf Surface Trichomes and Its Influence on Egglaying by Heliothis virescens
Authors: Navasero Rufina C. , Ramaswamy Sonny B.
Published: July 2010

Structure, color, growth habit, and pubescence of plants, in addition to chemical characteristics, affect acceptability of plants as potential food, refuge, or oviposition sites for insects; however, the impact of physical characteristics of plants on egglaying by the tobacco budworm moth, Heliothis virescens (F.), is poorly understood. This study was undertaken to determine the physical attributes, especially trichome types and growth habit, that may influence oviposition by gravid H. virescens females on several species of plants. The types and densities of trichomes found on the leaves of eight plant species, pigeonpea [Cajanus cajan (L.) Huth], crimson clover (Trifolium incarnatum L.), Texas bluebonnet (Lupinus texensis Hooker), cotton (Gossypium hirsutum L.), velvetleaf (Abutilon theophrasti Medikus), rose‐scented geranium (Pelargonium graveolens L'Her.), tobacco (Nicotiana tabacum L.), and groundcherry (Physalis angulata L.) were investigated using light and scanning electron microscopy. Simple or branched, hairlike (nonglandular) trichomes and capitate or club‐shaped (glandular) trichomes were found. Greater densities of trichomes occur on the abaxial surfaces than adaxial surfaces of leaves of most species. Heliothis virescens laid more eggs on the under surfaces of leaves, although the difference in oviposition rate was significant only for tobacco. Trichome type did not influence oviposition. In choice tests in laboratory and field cages, moths preferred to oviposit on tobacco and velvetleaf. In field cages, plants with erect growthabit were more acceptable to females than plants with procumbent growth habit.
Vegetative Growth of the Common Bean in Response to Phosphorus Nutrition
Authors: Lynch Jonathan , Läuchli André , Epstein Emanuel
Published: July 2010

Common bean (Phaseolus vulgaris L.) is often grown in soils of low P availability. It has been proposed that P deficiency may reduce crop growth by inhibiting leaf expansion and photosynthesis. Our objective was to determine how P applied to the root medium or leaves influences vegetative growth, leaf urea development, and photosynthesis of bean. Plants were grown in solid‐phase‐buffered sand culture at 0.4, 1.0, and 27.0 μM P with or without foliar P (ammonium polyphosphate) and with or without mycorrhizal inoculation. Leaf area development was very sensitive to P supply. Phosphorus deficiency primarily reduced leaf area by diminishing the number of leaves through effects on the number of nodes, branching, and relative leaf appearance rate, and secondarily by reducing leaf expansion. The effects of mycorrhizae and increased root P availability were similar. Foliar P application stimulated leaf area development in P‐deficient plants by increasing leaf appearance rate, branching, the number of mainstem nodes, and overall shoot growth, although expansion of individual leaves was reduced slightly. Mycorrhizal and foliar P effects were most pronounced at low root P availability. Although severe P deficiency decreased leaf photosynthesis in nonmycorrhizal plants, intermediate P stress in nonmycorrhizal plants did not reduce photosynthesis, and photosynthesis in mycorrhizal plants was inversely correlated with P stress. Root P availability influenced leaf photosynthesis largely by influencing leaf P concentration. We conclude that P availability affects bean growth primarily through effects on leaf appearance and biomass partitioning between photosynthetic and respiring organs, rather than through effects on leaf photosynthesis.
Crop Growth Rate and Seeds per Unit Area in Soybean
Authors: Egli D. B. , Zhen‐wen Yu
Published: July 2010

The number of seeds per unit area is an important yield component in soybean [Glycine max (L.) Merr.]; however, the mechanisms responsible for the regulation of this yield component are not well understood. Field experiments were conducted at Lexington, KY (3 yr), and at Taian, China (1 yr), to investigate the relationship between net canopy photosynthesis and seeds per unit area using genotypes with differences in individual seed growth rates (SGR). At Lexington, shades (30 and 63% reduction in insolation) were placed over plots from growth stage Rl until maturity to create differences in canopy photosynthesis. Planting dates (early and late) and row spacing (wide and narrow) were used at Taian to create differences in canopy photosynthesis. Crop growth rate (CGR) was measured between growth stage Rl and RS as an estimate of net canopy photosynthesis. Yield, seeds per m2, and SGR were also measured. Within each genotype, there was a linear relationship between CGR and seeds per m2 across treatments and years. Within an experiment, seeds per m2 at a constant CGR was inversely related to genotypic differences in SGR. A partitioning coefficient (γ) was estimated by dividing the total sink demand (seeds per m2 ✕ SGR) by CGR. There were no apparent genotypic differences in γ however, γ decreased linearly as CGR increased. The data suggest that the model proposed by Charles‐Edwards, which describes seeds per m2 as a direct function of canopy photosynthesis and a partitioning coefficient and an inverse function of assimilate flux to individual seeds, accurately describes the regulation of seeds per m2 in soybean.
Nitrogen, Potassium, and Irrigation Effects on Water Relations of Kentucky Bluegrass Leaves
Authors: Carroll Mark J. , Petrovic A. Martin
Published: July 2010

Transpiration and expansive growth in leaves are turgor‐dependent processes. Solute concentration and osmotic potential are inextricably linked to turgor maintenance. An empirical equation predicting stomatal resistance (Rs) from bulk leaf turgor (ψt) would be useful in developing computer simulations for turfgrass management. A growth‐chambers study was conducted to quantify the relationship between Rs and ψt in Kentucky bluegrass (Poa pratensis L. cv. A‐34). The effects of N, K, and irrigation frequency on bulk leaf osmotic potential at full turgor (ψπ100) and apoplastic water fraction (AWF) also were examined, using psychrometric techniques. Treatments consisted of two rates of N and K and two irrigation frequencies. An exponential model was used to describe the relationship between Rs and ψt. The least squares prediction equation was Rs = 581 + 2500 exp(−6,99ψt), r2 = 0.69, where ψt and Rs. are expressed in units of MPa and s m−1, respectively. Increasing the time between rewatering containers to −0.02 MPa from 1 to 5 d did not influence ψπ100. For plants watered dally, increasing the amount of N supplied every 30 d from 35 to 175 kg ha−1 increased ψπ100 0.22 MPa, while increasing K from 17.5 to 175 kg ha−1 for the same application interval caused ψπ100 to decline 0.20 MPa. Altering the supply of N or K did not affect ψπ100 when the containers were watered every 5 d. Increasing the irrigation interval from 1 to 5 d caused AWF to decline from 22 to 12%; however, AWF estimates were highly variable. Results indicate the combined influences of N and K fertility practices can have a significant impact on the concentration of osmotically active solutes within Kentucky bluegrass bulk leaf tissue.
Proteolysis in Ensiled Forage Legumes That Vary in Tannin Concentration
Authors: Albrecht K. A. , Muck R. E.
Published: July 2010

Extensive protein hydrolysis after harvest and during fermentation is characteristic of forage legumes preserved as silage. Differences in proteolysis among species have been observed, but plant characteristics associated with these differences have not been well defined. This study was conducted to determine if tannins play a role in modifying N transformations associated with the preservation of forage legumes as silage. In 1987, 12 legume genotypes (representing six species) were field grown and analyzed for tannin concentrations pre‐ and post‐ensiling dry matter (DM), pH, and N forms. In 1988, 18 genotypes (representing seven species) were evaluated in a similar manner. Tannin concentrations range from 0 to 27 g tannic acid equivalents kg−1 DM in 1987 and 0 to 31 g in 1988. Dry matter concentration pH, and concentration of total N, soluble nonprotein N (SNPN), free amino acid N, and ammonia N of fresh and ensiled herbage were within the range of previous literature reports for forage legumes. The proportion of total N in the form of SNPN after 35 d ensiling ranged from 32 to 73% in 1987 and 26 to 69% in 1988 and was negatively related to tannin concentration (r2 = 0.75). Within sericea lespedeza [Lespedeza cuneata (Dum‐Cours) G. Don], the only species with substantial variation for both tannin and silage SNPN concentrations r2 values were 0.81 in 1987 and 0.88 in 1988. Red clover(Trifolium pratense L.) and cicer milkvetch( Astragalus cicer L.) did not contain measurable levels of tannins, but exhibited lower proteolysis than alfalfa (Medicago sativa L.). These results suggest that tannins play a major role in limiting proteolysis some legumes during ensiling, but other factors also are involved.
Relationships among 70 North American Oat Germplasms: I. Cluster Analysis Using Quantitative Characters
Authors: Souza E. , Sorrells M. E.
Published: July 2010

Cluster analysis can be used to identify cultivars with similar adaptation, which can be useful for sampling in subsequent studies and parental selection in breeding programs. To test these applications in oat (Avena sativa L. and A. byzantina C. Koch), relationships among 70 current and historically important North American oat cultivars and germplasm accessions were measured using cluster analysis of 13 quantitative characters. Cultivars were planted in replicated field trials at two locations for 2 yr and evaluated for heading date, maturity date, height, tillers per mete row, aboveground biomass, grain weight, test weight, 100‐kernel weight, and culm diameter. Four derived characters (harvest index, growth phase index, grain‐filling period, and a straw stiffness index) were also estimated for each germplasm. Heading date was the most important source of variation among genotypes. Cluster analysis produced four large groups that generally corresponded to latitude of origin or adaptation with significant differences between groups for all characters. Three late‐heading spring oat cultivars (Banner, White Tartar, and Cornellian) were placed together with five late‐heading winter cultivars (Hairy Culberson, Winter Turf, Walken, Norline, and Wintok), despite crop history and pedigrees indicating that these two groups of cultivars are divergent. The importance of heading date as a source of variation and the false grouping of divergent, lateheading oats as genetically similar sugges that clusters based on quantitative characters are derived from a biased genetic‐relationship measure. Clustering by morphology may, however, be valuable for identification of genotypes with similar adaptations for breeding and agronomic research programs.
Inheritance of Resistance to Helminthosporium carbonum Race 3 in Maize
Authors: Halseth D. E. , Pardee W. D. , Viands D. R.
Published: July 2010

Since the early 1970s, several reports of a new helminthosporium leafspot disease of maize (Zea mays L.) caused by Helminthosporium carbonum Ullstrup (syn. Bipolaris zeicola (Stout) Shoemaker) (teliom. Cochliobolus carbonum Nelson) Race 3 indicate that it has become widespread in the eastern USA and can cause heavy yield losses. This pathogen inflicts a range of symptoms on maize, depending on pathogen isolate and host genotype, confounding the development of screening techniques to identify plant genotypes resistant to this pathogen. The objective of our study was to determine if adequate progress from selection for resistance could be accomplished against a range of polymorphic symptoms by a field breeding program. An eight‐parent diallel analysis and a generation mean analysis were used to evaluate the potential for genetic improvement. Inbred maize parents (resistant A239, Ay499, Mo17, and R181; susceptible B8, Co109, W64A, and W182BN) and their F1's, F2's and backcrosses were grown in the field during two seasons and artificially inoculated. Lesion area was subjectively classified into a numerical disease rating scale. The results of the diallel analysis indicated that only general combining ability (GCA) effects, or additive genetic effects, were highly significant. The generation mean analysis confirmed that the additive component was the most important factor, accounting for 52 to 75% of the variation in the models. Dominance and digenic interaction components were occasionally significant. Broad‐sense and narrow‐sense heritabilities ranged from 58 to 77% and 57 to 67%, respectively, for two seasons. Field screening techniques to select inbred parents and to evaluate their progeny were found to be satisfactory, but growth chamber evaluations were not always an accurate or reliable predictor of field responses, particularly regarding intermediate disease reaction.
Genetic Variation for Nitrogen Use in Soft Red ✕ Hard Red Winter Wheat Populations
Authors: May L. , Van Sanford D. A. , MacKown C. T. , Cornelius P. L.
Published: July 2010

Hard red winter (HRW) wheat (Triticum aestivum L. era. Thell.) cultivars are genetically distinct from soft red winter (SRW) wheat cultivars and thus provide new sources of germplasm for SRW wheat breeding programs. Previous research has shown that HRW ✕ SRW wheat crosses can generate segregates with acceptably low grain protein concentration (GPC). This study was conducted evaluate genetic variation of traits related to N uptake, partitioning, and utilization in HRW ✕ SRW wheat populations. The F3 and F4 generations of three HRW ✕ SRW crosses were grown in 1985 and 1986, respectively, on a Maury silt loam soil (fine, mixed, mesic Typic Paleudalf) near Lexington, KY. Significant differences among F4 families were observed for N harvest index (NHI), GPC and use efficiency for yield (NUEY) and protein (NUEP) in all populations. The correlation between N partitioning (NHI) and GPC varied among crosses, ranging from r = −0.57 (P < 0.01) to near zero. Highly significant differences for NUEY and NUEP were observed among F4 families of each cross. A path analysis indicated that the direct effect of N uptake efficiency accounted for as much as 91% of the variation in NUEY and 88% in NUEP. Indirect effects were of little consequence. The data demonstrate that N‐use traits are strongly influenced by the environment, and would be difficult to modify in a breeding program.
Direct and Indirect Selection for Small Seed of Soybean in Temperate and Tropical Environments
Authors: LeRoy A. R. , Cianzio S. R. , Fehr W. R.
Published: July 2010

Some food items made from soybean [Glycine max (L.) Merr.] require small seeds. The wild soybean, G. soja Sieb. & Zucc., has been used as a source of genes for small seed size for development of high‐yielding cultivars for specialty markets. The objective of this study was to determine the effectiveness of direct and indirect selection for small seed in three interspecific crosses of soybean (G. max ✕ G. soja) based on seed weight and pod width measurements. Indirect selection was based on pod width. Forty random BC2F2‐derived lines from each of three crosses were evaluated for seed weight and pod width at two environments in Iowa and two environments in Puerto Rico. Broad‐sense heritability estimates among the three crosses based on variance component estimates for seed weight were 35% on a plant, 52% on a plot, and 89% on an entry‐mean basis, and for pod width were 35% on a plant, 51% on a plot, and 87% on an entry‐mean basis. The actual genetic gain averaged across environments and crosses for direct selection of seed weight was 6 mg seed−1 on a plant, 6 mg seed−1 on a plot, and 7 mg seed−1 on an entry‐mean basis. Indirect selection by pod width resulted in an actual genetic gain of 6 mg seed−1 on a plant, 7 mg seed−1 on a plot, and 8 mg seed−1 on an entry‐mean basis. Selection in Puerto Rico was as effective as selection in Iowa. The results indicate that both direct and indirect selection for small seed are effective in the temperate and tropical environments that were studied.
Grain Yield of Composite Cross Populations of Barley: Effects of Natural Selection
Authors: Soliman K. M. , Allard R. W.
Published: July 2010

The effects of natural selection on grain yield of composite cross population of barley (Hordeum vulgare L) was investigated to determine the relationship between the amount of genetic diversity and yield and stability of yield. Yield test data for five commercial cultivars of spring barley and early, intermediate, and late generations of three composite cross populations were analyzed by regression methods. Deviations from regression were generally larger for the commercial cultivars. Deviations from regression were particularly large for the commercial cultivar Sutter, indicating instability, which was consistent with its ability to perform well in only one limited geographical area. Deviations from regression for the widely adapted cultivar Atlas 68 were small, and similar to those of the composite crosses. The composite crosses continued to show a marked yield increase over generations, perhaps as a result of increased adaptation. As indicated by cluster analyses, the commercial cultivars (with the exception of Sutter) were more similar to one another than they were to the composite crosses, and vice versa. Stability was associated with rainfall, evidently through the effect of rainfall on the prevalence of foliar diseases, especially scald [Rhynchosporium secalis (Oudem.) J.J. Davis] and net blotch (Pyrenophora teres Drechs.), and on lodging. It was concluded that the composite cross populations offer an opportunity to produce cultivars that show small or no genotype‐environment interaction.
Screening Durum Wheat Germplasm for Dry Growing Conditions: Morphological and Physiological Criteria
Authors: Clarke J. M. , Romagosa I. , DePauw R. M.
Published: July 2010

To utilize germplasm resources effectively in breeding it is necessary to characterize and evaluate genotypes for desirable traits. In the case of factors related to grain yield under drought, it must be determined whether simply measured morphological or physiological characters can be used to identify genotypes worthy of further evaluation. To that end, 4300 durum wheat (Triticum turgidum L. var. durum) genotypes were studied under rainfed conditions on a Swinton loam soil (Aridic Haploborall) at Swift Current, SK, Canada. Heading date, visual scores of leaf rolling, leaf size, glaucousness, maturity, agronomic suitability, and residual (cuticular) transpiration rate (Rt) of excised leaves were measured in 1984. Selected subsets of genotypes were studied further in 1985 through 1987. Superior agronomic score in 1984, a dry season, was most effective for selection of genotypes with high grain‐yield potential in 1985 (very dry), but not in 1986 (above average precipitation). Mean yield of genotypes selected on the basis of agronomic score and on agronomic score plus heading date was 18 and 27% greater (P < 0.01), respectively, than the mean of the unselected population. Elimination of genotypes with high Rt was associated with improved yield potential in 1985, while low Rt was associated with low yield potential in 1986. Screening for Rt was not worthwhile, given that most of the high‐Rt genotypes could be effectively eliminated on the basis of poor agronomic score. Glaucousness was not a useful selection criterion since ≈93% of the genotypes were glaucous. It was concluded that visual rating of germplasm collections under dry growing conditions would be an effective means of identifying genotypes worthy of further study.
Response of Western Corn Rootworm‐Infested Corn to Nitrogen Fertilization and Plant Density
Authors: Spike Barbara P. , Tollefson Jon J.
Published: July 2010

Growth response of corn (Zea mays L.) to corn rootworm (Diabrotica spp.) infestation is poorly understood and may be influenced by management practices and environmental conditions. The objectives of this 2‐yr experiment were to determine the effect of three N rates (0, 168, and 336 kg ha−1) and three plant density treatments (39 000 [1984 only], 63 000, and 87 000 plants ha−1 on dry‐matter accumulation and partitioning of corn plants infested with three levels of western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) [0, 1967, and 3934 eggs m−1 row]. Plant dry weight, taken periodically and subdivided into vegetative and reproductive fractions, was used to calculate the harvest index and mean relative growth rates (R1). In 1985, leaf area was measured and leaf area index (LAI), mean net assimilation rate (NAR), and leaf area ratio (LAR) were calculated. In 1985, a dry year, rootworm‐injured plants had significantly reduced dry weight, leaf area, harvest index, R1, and NAR. Dry‐matter accumulation of injured plants was greater in low plant‐density and applied‐N treatments. In comparison with parameters of healthy plants, dry weight, R1 and NAR of injured plants were reduced in high‐N treatments at the time of rootworm feeding. This significant rootworm ✕ N interaction did not occur after feeding ceased. Rootworm infestation significantly reduced the harvest index only in 1985, suggesting that dry conditions increase the impact of root injury on ear development and yields.
Soybean Flowering Date: Linear and Logistic Models Based on Temperature and Photoperiod
Authors: Sinclair T. R. , Kitani S. , Hinson K. , Bruniard J. , Horie T.
Published: July 2010

Temperature and photoperiod are important determinants of the time from emergence to flowering in soybean [Glycine max (L.) Merr.]. A linear and a logistic model have been developed independently for describing the development rate to flowering (a high development rate means a short time to flowering). Field experiments on Arredondo fine sand soil (loamy, siliceous hyperthermic Grossarenic Paleudult) at Gainesville, FL, during 3 yr using a range of sowing dates in each year provided data to evaluate each model. In the first 2 yr, 13 cultivars were grown from 17 sowing dates. The linear model was found to represent adequately these 2 yr of data, but the logistic model was somewhat superior for 12 of the 13 cultivars. The coefficients derived for each model from the first 2 yr of study were used to predict flowering date in the 3rd yr. Both models gave accurate predictions of flowering date, although the larger discrepancies between predictions and observations were obtained with the linear model. Assuming an adequate data base to evaluate the coefficients in each model, either model was able to predict soybean flowering date.
Relationship of Seed Vigor to Crop Yield: A Review
Authors: TeKrony Dennis M. , Egli Dennis B.
Published: July 2010

Seed viability and vigor directly affect the performance of seeds planted to regenerate the crop. Although seed quality can influence many aspects of performance (e.g., total emergence, rate of emergence), the objective of this review was to examine the relationship of seed vigor to one aspect of performance: crop yield. Reductions in yield can be indirectly related to low seed vigor if plant populations are below a critical level. Thus, we have reported only on the direct effects of seed vigor on yield in the absence of population differences. Only those references where seed vigor was measured or where seed lots were evaluated following natural or artificial storage (both reduce seed vigor) were included. Annual crops were subdivided into those harvested during vegetative growth (eight species), early reproductive growth (four species) or full reproductive maturity (nine species). Seed vigor affects vegetative growth and is frequently related to yield in crops that are harvested vegetatively or during early reproductive growth. However, there is usually no such relationship in crops harvested at full reproductive maturity, because seed yields at full reproductive maturity are usually not closely associated with vegetative growth. The use of high‐vigor planting seed can be justified for all crops, however, to ensure adequate plant populations across the wide range of field conditions that occur during emergence.
Isolation of Parenchyma and Sclerenchyma Cell Types from the Plant Parts of Grasses
Authors: Grabber J. H. , Jung G. A.
Published: July 2010

A simple and rapid mechanical method is reported for the isolation of parenchyma and sclerenchyma from the leaf blade, leaf sheath, and stem of grasses. Parenchyma and sclerenchyma cells were isolated by wet‐sieving homogenized plant parts of orchard‐grass (Dactylis glomerata L.) and switchgrass (Panicum virgatum L.). Parenchyma cells were collected in a fraction <150 μm in diameter, while sclerenchyma cells were retained in a fraction >1180 μtm in diameter. The purity of parenchyma was very high from the leaf blade and leaf sheath (>95%) and moderate from the stem (70‐ 85%). Sclerenchyma preparations contained >80% sclerenchyma fibers, with the balance consisting primarily of vascular tissue. This method provides a means of isolating parenchyma and sclerenchyma for studies of the chemical, digestion, and physical characteristics of their cell walls. This technique, however, cannot be used to estimate the proportions of cell types contained in grass herbage.
Sixteen Cycles of Recurrent Full‐Sib Family Selection for Grain Weight in Two Maize Populations
Authors: Moll Robert H.
Published: July 2010

Full‐sib family selection for greater grain weight per plant is expected to increase the frequency of favorable alleles for this trait in random‐mating populations of maize (Zea mays L.). This study was undertaken to assess responses to selection and changes in genetic variances accumulated during 16 cycles in (i) the open‐pollinated population Jarvis Golden Prolific, and (ii) the population descended from the F2 generation of the single cross NC7 ✕ CI21. Selection responses were measured in replicated experiments that included Cycle 0 and several advanced selection cycles, and by estimates of accumulated gains through all 16 cycles of the selection experiments per se. In addition to increases in mean grain weight, changes in responsiveness to environmental effects were evaluated by regression analysis. The selection experiments were designed to provide estimates of genetic variances from progeny test data of each selection cycle. Gains due to selection were linear for 16 cycles at a rate of 2.4% cycle−1 for the Jarvis population and 4.5% cycle−1 for the NC7 ✕ CI21 population. Advanced selection cycles were more responsive to environments than the original populations. Additive genetic variance showed no trend associated with selection in the Jarvis population, but declined with selection in the NC7 ✕ CI21 population. Accumulated gains were greater in the NC7 ✕ CI21 population, even though the genetic variance in that population was smaller initially and has decreased in later selection cycles.