bluuebunny/crossref_metadata_2025 huggingface dataset:
Spring Dead Spot Resistance and Quality of Seeded Bermudagrasses under Different Mowing Heights
Authors: Martin D.L. , Bell G.E. , Baird J.H. , Taliaferro C.M. , Tisserat N.A. , Kuzmic R.M. , Dobson D.D. , Anderson J.A.
Published: July 2010

Bermudagrass (Cynodon spp. L.C. Rich.) cultivars resistant to spring dead (SDS) caused by Ophiosphaerella herpotricha (Fr.) Walker and winter‐kill are important for residential and commercial use in transition zone climates. Field research was conducted on ‘Mirage’, ‘OKS 91‐11’, and ‘Jackpot’ seeded bermudagrasses [Cynodon dactylon (L.) Pers. var. dactylon] at Stillwater, OK, between 1996 and 1999 to determine their resistance to SDS. Plots were inoculated in 1996 with O. herpotricha isolate KS 188 and mowed to a height of either 1.3 cm or 3.8 cm. The SDS necrotic patch area of all cultivars increased each year and patch area was greater in turf at the higher mowing height. OKS 91‐11 had a smaller SDS necrotic patch area than the other cultivars. Mirage had necrotic patch area equal to Jackpot at 1.3 cm and less necrotic area than Jackpot at 3.8 cm. OKS 91‐11 had greater shoot survival density in necrotic patches than Jackpot or Mirage in 2 of 3 yr at 1.3 cm. Cultivars did not differ in shoot survival density at 3.8 cm. Higher overall quality was provided by OKS 91‐11, when compared with Mirage and Jackpot in 3 of 4 and 2 of 4 yr, respectively. Jackpot had better quality than Mirage in 2 of 4 yr. Early spring green‐up was negatively correlated with SDS patch size and positively correlated with shoot survival in SDS patches. Winter‐kill was positively correlated with SDS patch size and negatively correlated with shoot survival in SDS patches.
Forage Nutritive Value of Various Amaranth Species at Different Harvest Dates
Authors: Sleugh Byron B. , Moore Kenneth J. , Brummer E.Charles , Knapp Allan D. , Russell James , Gibson Lance
Published: July 2010

Complete information on forage quality characteristics of amaranth is unavailable. This study evaluated the forage quality of various amaranth accessions at different harvest dates. Seven accessions from the North Central Plant Introduction Station were established in June 1997 and June 1998 near Boone, IA. Subplots were harvested six times at 2‐wk intervals beginning 42 d after planting (DAP). In vitro dry matter digestibility (IVDMD), neutral detergent fiber (NDF), crude protein (CP), nitrate‐nitrogen, acid detergent fiber (ADF), acid detergent lignin (ADL), protein and fiber digestion, and undegradable intake protein (UIP) were determined. Averaged over accessions, IVDMD decreased (P < 0.05) from 780 g kg−1 at 42 DAP to 680 g kg−1 at 112 DAP. Digestibility ranged from 590 to 790 g kg−1 Averaged over accessions at 42 DAP, CP was 270 g kg−1 then decreased to 100 g kg−1 at 112 DAP. Neutral detergent fiber increased from 310 g kg−1 at 42 DAP to 430 g kg−1 at 112 DAP. Averaged over harvest date, Amaranthus cruentus (Zimbabwe) had the highest NDF (390 g kg−1), and A. hybrid (Puebla, Mexico) had the lowest (330 g kg−1). Amaranthus cruentus (Zimbabwe), A. cruentus (Rwanda), and A. hybrid (Puebla, Mexico) had UIP averaging 25, 22, and 16%, respectively, of total crude protein after 16 h of digestion. Forage quality of the accessions at most harvest dates was consistent with what would be expected for relatively good quality forage, although high nitrate levels are a concern.
The Naturally Occurring High Oleate Oil Character in Some Peanut Varieties Results from Reduced Oleoyl‐PC Desaturase Activity from Mutation of Aspartate 150 to Asparagine
Authors: Bruner Ann C. , Jung Sook , Abbott Albert G. , Powell Gary L.
Published: July 2010

Commercially important high oleate seed oils, meaning that they are low in polyunsaturated fatty acid content, are resistant to developing rancidity. A peanut cultivar (Arachis hypogaea L.) derived from a naturally occurring peanut has low oleoyl‐PC desaturase activity, the key enzyme in the production of linoleate, normally an abundant polyunsaturated fatty acid. Two genes for this enzyme are expressed in peanut seeds, and when they were separately expressed in yeast (Saccharomyces cerevisiae), one produced less linoleate than the other. Although the two cDNA encode similar sequence proteins, they differ by four amino acids. Aspartate at position 150 was asparagine in the low activity copy. An aspartate was present in many membrane desaturases and other related membrane enzymes at an equivalent location suggesting that the mutation at 150 was key to the low activity. In this work, site‐specific mutagenesis was used to change the aspartate in the high activity enzyme to asparagine and to change asparagine in the lower activity enzyme to aspartate. These changes, upon expression in yeast, resulted in nearly complete loss of activity of the previously more active desaturase and restored activity to the previously less active desaturase. This decrease in activity of the one gene, a consequence of mutation from aspartate 150 to asparagine, together with reduction in transcript level of the high activity gene in the mutant variety, suggest that these alterations are the molecular basis of the high oleate phenotype in some commercial varieties of peanut.
Host Plant Resistance Genes for Fusarium Head Blight: Mapping and Manipulation with Molecular Markers
Authors: Kolb F.L. , Bai G‐H. , Muehlbauer G.J. , Anderson J.A. , Smith K.P. , Fedak G.
Published: July 2010

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)], or scab, causes severe reductions in yield and quality of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Evaluation of FHB resistance is laborious and subject to environmental influence; therefore, molecular markers for FHB resistance genes will greatly enhance selection for FHB resistance. This review seeks to summarize information on molecular markers associated with quantitative trait loci (QTL) for resistance to FHB in wheat and barley and the use of those markers for marker assisted selection. Our goal is to summarize the current state of knowledge on the genetics of FHB resistance, the map locations of QTL for FHB resistance, and the future directions and potential applications of this research. In wheat, five types of resistance have been described, and Type II resistance (expressed in Chinese wheat cultivar Sumai 3) is the easiest type to assess. Several research groups are developing molecular markers associated with genes for FHB resistance from Sumai 3, a widely used source of Type II resistance in wheat breeding programs worldwide. In four different populations, each having Sumai 3 or a derivative as one parent, one to four QTL have been identified that explain up to 63% of the variation in resistance. QTL were identified on chromosomes 3BS and 6BL in three or more populations. Recently, in barley, restriction fragment length polymorphism (RFLP) markers associated with genes for FHB resistance, deoxynivalenol (DON) accumulation, and kernel discoloration were identified on all seven chromosomes. Three regions, located on chromosomes 2, 3, and 5 were identified in several mapping populations. Comparing the QTL locations between wheat and barley shows that the barley chromosome 3 QTL is located in a syntenous region in wheat. The following areas of research on molecular markers associated with FHB resistance should be emphasized: (i) identifying and mapping better resistance sources in wheat and barley; (ii) validating QTL in additional populations; and (iii) developing markers that can be easily used in breeding programs and across populations.
Transgenic Approaches to Combat Fusarium Head Blight in Wheat and Barley
Authors: Dahleen Lynn S. , Okubara Patricia A. , Blechl Ann E.
Published: July 2010

Fusarium head blight (FHB) and contamination with deoxynivalenol (DON) produced by the primary pathogen Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)] have caused devastating losses to wheat (Triticum aestivum L.), durum (Triticum turgidum L. ssp. durum Desf.Husr.), and barley (Hordeum vulgare L.) growers across the USA since the early 1990s. Evaluation of barley, wheat, and related germplasm yielded only a few accessions with partial resistance. This resistance appears, in most cases, to be under polygenic control, making the development of resistant cultivars with suitable agronomic and quality traits a challenge. The insertion of individual antifungal and antitoxin genes via genetic transformation has the potential to aid in development of resistant wheat and barley cultivars. Although wheat and barley transformation has been achieved in several laboratories, the development of a high throughput wheat and barley transformation systems has been slowed by genotype effects on plant regeneration, low transformation efficiencies, somaclonal variation, and problems with transgene inheritance and stability of expression. Among the antifungal genes targeted to combat FHB are coding sequences for proteins that degrade fungal cell walls, disorganize fungal membranes, bolster the host defense response systems, and interfere with fungal protein synthesis, pathogenesis, and/or accumulation of DON. Promoter sequences have been selected that confer high levels of expression to the antifungal constructs, particularly in the spike tissues which are susceptible to FHB. As more antifungal genes are inserted into wheat and barley, field and greenhouse evaluation will show whether transgenes achieve their potential in the fight against FHB.
Seeding Date Alters Carbohydrate Accumulation in Winter Wheat
Authors: Gaudet D.A. , Laroche A. , Puchalski B.
Published: July 2010

Early seeding and accumulation of soluble carbohydrates is critical for the full expression of snow mold [caused principally by Typhula incarnata Lasch ex. Fr., Typhula ishikariensis Imai, Sclerotinia borealis Bub. & Vleug., Microdochium nivalis (Ces. ex Berl. & Vogl.) Samuels and Hallet] resistance in winter wheat (Triticum aestivum L. em Thell). Experiments were conducted during two growing seasons in the field at Lethbridge, AB, to study how early seeding affects the quantity of simple sugars and fructan, and degree of fructan polymerization in both resistant and susceptible cultivars. Different planting dates were employed to obtain plants at different developmental stages prior to winter dormancy. Leaf and crown tissue samples were collected from 14 winter wheat cultivars differing in snow mold resistance throughout the autumn, winter, and early spring. Snow mold resistant cultivars accumulated moderate levels of simple sugars and high levels of fructans across seeding dates and maintained a higher degree of polymerization of fructans compared with snow mold susceptible cultivars. Early seeded treatments generally accumulated lower levels of simple sugars and higher levels of more highly polymerized fructan in the autumn and winter than did late seeded treatments. The closest correlations between snow mold resistance and fructan content (r = 0.87) or degree of polymerization (r = 0.74) were observed in the later seeded treatments, suggesting that early seeding masked the expression of genotypic snow mold resistance. These results demonstrate an association between early seeding and fructan accumulation in relation to snow mold resistance in winter wheat and provide a physiological basis for the higher level of snow mold resistance among early seeded treatments.
Row Spacing and Weed Management Systems for Nonirrigated Early Soybean Production System Plantings in the Midsouthern USA
Authors: Heatherly Larry G. , Elmore C.Dennis , Wesley Richard A. , Spurlock Stan R.
Published: July 2010

The new paradigm for soybean [Glycine max (L.) Merr.] production in the midsouthern USA is the Early Soybean Production System (ESPS), which involves planting early‐maturing cultivars in April. Field studies were conducted for 3 yr at Stoneville, MS, on Sharkey clay (very‐fine, smectitic, thermic chromic Epiaquert) with a MG IV soybean cultivar grown in 0.5‐m‐wide rows (NR) and a MG V cultivar grown in 1‐m‐wide rows (WR), both with varying weed management inputs, to determine the most profitable system for nonirrigated ESPS plantings. Weed management in NR consisted of broadcast application of herbicides. Weed management in WR included band (0.5‐m‐wide) application of herbicides plus two to three between‐row cultivations. Total weed cover at harvest in all treatments was below 10% in the first 2 yr. In the third year, browntop millet [Brachiaria ramosa (L.) Stapf.] plus pitted morningglory (Ipomoea lacunosa L.) percentages exceeded 10% in 3 of 10 treatments in NR and in 1 of 10 treatments in WR, but these treatments were among those producing the highest yield and net return. Soybean treated for preemergence (PRE) broadleaf management, PRE broadleaf plus PRE grass management, PRE broadleaf plus postemergence (POST) grass management, and PRE and POST broadleaf plus PRE and POST grass management were among the highest yielding treatments, but only the treatment of PRE broadleaf management provided the highest net return across both NR and WR. Soybean with PRE and POST broadleaf plus PRE grass management provided the lowest net returns across both NR and WR. These results indicate that only a broadcast PRE broadleaf herbicide in NR and a PRE banded broadleaf herbicide plus POST cultivation in WR in an ESPS planting that is not irrigated will produce yield and net return that are among the highest, and weed management cost that is among the lowest of ≤$62 ha−1
Creeping Bentgrass Response to Inorganic Soil Amendments and Mechanically Induced Subsurface Drainage and Aeration
Authors: Bigelow Cale A. , Bowman Daniel C. , Cassel D.Keith , Rufty Thomas W.
Published: July 2010

Creeping bentgrass (Agrostis stolonifera var. palustris Huds. Farw.) golf greens often decline under the hot, humid summer conditions of the southeastern USA. Factors associated with this decline may be poor soil aeration, excessive soil wetness, high temperatures, and turfgrass diseases. A field study evaluated a mechanical forced air system for its ability to modify the soil water content and oxygen (O2) status of newly constructed sand‐based rootzones, and its effects on turfgrass quality (TQ) and seasonal bentgrass rooting. Three drainage situations were studied: gravity drainage (control treatment) and gravity drainage supplemented by two mechanically induced drainage treatments, water evacuation (WE) or WE followed by air‐injection (AI). In addition, the effects of peat moss and several inorganic soil amendments on bentgrass establishment and growth were studied. Compared with gravity drainage, WE significantly decreased water contents (0.01–0.05 m3 m−3) averaged across the 0‐ to 27‐cm depth, with the greatest change occurring near the bottom of the rooting media. Seasonal fluctuations in soil O2 and CO2 concentrations were observed, but O2 remained high, 0.19 m3 m−3, and CO2 was low, <0.01 m3 m−3, regardless of drainage treatment. Drainage treatments had no effect on TQ or root mass density (RMD). However, both TQ and RMD increased from 1998 to 1999, possibly becaue of greater turfgrass density. Amendments had significant effects on establishment and TQ in the following order: peat moss > Ecolite = Profile > Greenschoice ≥ unamended sand. This response was probably due to improved water and nutrient retention of the amended rootzones. Although the forced air–vacuum technology provided little benefit in these newly constructed greens, it may be useful on mature putting greens that suffer from poor soil aeration or drainage.
Combining Ability of Binary Mixtures of Native, Warm‐Season Grasses and Legumes
Authors: Springer T.L. , Aiken G.E. , McNew R.W.
Published: July 2010

Growing complementary plant species is an alternative approach to enhancing pasture production. Our objective was to estimate combining ability for native, warm‐season grasses and legumes grown in binary mixtures in the field using a combining ability analysis of variance. Six monocultures and 15 binary mixtures of the following species were studied: big bluestem, Andropogon gerardii Vit.; Illinois bundleflower, Desmanthus illinoensis (Michx.) MacM.; roundhead lespedeza, Lespedeza capitata Michx.; slender lespedeza, L. virginica (L.) Britt.; switchgrass, Panicum virgatum L.; and indiangrass, Sorghastrum nutans (L.) Nash. General combining ability (GCA) effects were found for forage dry matter yields (DMY, P ≤ 0.05) of Illinois bundleflower (−1240 kg ha−1), roundhead lespedeza (−3460 kg ha−1), slender lespedeza (−3300 kg ha−1), and switchgrass (8370 kg ha−1). Specific combining ability (SCA) effects were found for DMY (P ≤ 0.1) of switchgrass‐legume mixtures (1360 kg ha−1) and indiangrass‐Illinois bundleflower mixtures (1230 kg ha−1). General combining ability and SCA effects were found for crude protein concentration (CPC) of all species and mixtures (P ≤ 0.1), respectively. General combining ability effects were found for in vitro dry matter digestibility (IVDMD) for switchgrass and the three legume species (P ≤ 0.05). The compatibility of these species could not be predicted solely by DMYs. Compatible mixtures, however, were identified with greater confidence when other variables, such as CPC, IVDMD, and visual observations, were taken into account. On the basis of total forage protein (DMY times CPC), the only compatible grass‐legume mixture was indiangrass‐Illinois bundleflower (SCA effect = 100 kg ha−1, P ≤ 0.05).
Partial Resistance of Transgenic Peas to Alfalfa Mosaic Virus under Greenhouse and Field Conditions
Authors: Timmerman‐Vaughan Gail M. , Pither‐Joyce Meeghan D. , Cooper Pauline A. , Russell Adrian C. , Goulden David S. , Butler Ruth , Grant Jan E.
Published: July 2010

Transformed pea (Pisum sativum L.) lines were produced with two chimeric gene constructs encoding the coat protein (CP) of alfalfa mosaic virus (AMV) strain NZ1. To determine whether transformed lines have improved AMV resistance, progeny of independently derived transgenic lines were tested in the greenhouse and five lines with improved virus resistance were identified. Resistance was observed only in individual plants that accumulated detectable CP product from the transgene, suggesting that resistance is CP mediated. Plants that accumulated detectable amounts of transgene CP product yet were susceptible to AMV were found among the progeny of most lines, indicating that these lines are only partially resistant to the challenging AMV strains, 425 and NZ1(Lincoln). A field test was conducted with the progeny of four independently derived transgenic lines. To test for improved virus resistance under field conditions, plots of transgenic lines and nontransgenic controls were inoculated with two AMV strains, NZ1(Lincoln) and NZ34. Analysis of disease severity in seedlings in inoculated plots confirmed that partial virus resistance can be produced by genetically modifying peas with AMV CP sequences.
Diversity and Origin of Andean Landraces of Common Bean
Authors: Beebe S. , Rengifo J. , Gaitan E. , Duque M.C. , Tohme J.
Published: July 2010

Landraces of common bean (Phaseolus vulgaris L.) pertaining to the Andean gene pool are remarkably diverse in plant and grain morphology and agroecological adaptation. The objectives of this study were to determine the genetic structure of a large sample of Andean landraces, and to establish a correspondence between Andean landraces and wild bean populations that might have served as the source of domesticated bean. A total of 182 landraces representing the three recognized races of Andean bean and including many popping bean types were analyzed using amplified fragment length polymorphism (AFLP) technology with multiple correspondence analysis (MCA) and unweighted pair group method with arithmetic mean (UPGMA). Twenty‐nine wild bean accessions representing the diversity of wild bean in South America and Middle America were also included. Two sets of primers were used to generate 189 polymorphic AFLP. The graph of the results of MCA indicated that most landrace accessions formed a single undifferentiated group, and analysis by UPGMA combined with bootstrapping confirmed this. A small number of outliers presented bands that suggested introgression from Mesoamerican beans. Among wild bean populations from South America, those from Bolivia graphed in closest proximity to the cultivated bean, suggesting that Bolivia might have been an important primary domestication site. The narrow genetic base of Andean beans emphasizes the need to broaden the genetic base of the Andean gene pool.
The Case for Multiple‐Use Plant Germplasm Collections and a Strategy for Implementation
Authors: Greene S.L. , Morris J.B.
Published: July 2010

Germplasm collections are viewed as a source of genetic diversity to support crop improvement and botanical research, as well as support conservation efforts. The United States Department of Agriculture's National Plant Germplasm System (NPGS) is responsible for managing plant genetic resources in the USA. Despite patterns of use that indicate that gene source and wild species are requested as frequently as cultivated species in NPGS collections that are taxonomically diverse, the contents of most NPGS collections continue to reflect the historic objectives of plant introduction. Narrow germplasm collections are restricted in their ability to meet the needs of diverse users and have limited function conserving plant biodiversity. This article outlines a model that can be used to diversify germplasm collections so they effectively serve users and contribute to conservation, yet remain a size that ensures effective maintenance of accessions. The model is developed by first carefully defining the overall scope of the collection. A taxonomically broad collection that falls within the scope is then defined with relatively few accessions. However, accession representation is increased for characters or species that are of specific interest to users, or that require protection. Accession representation in areas of interest would be dynamic, reflecting the changing needs of users and conservation. A diverse group of stakeholders is charged with the task of working together to establish priorities that can be used to guide the development of a multiple‐use collection that contains a manageable number of accessions.
Genetic Relationships of Crown Rust Resistance, Grain Yield, Test Weight, and Seed Weight in Oat
Authors: Holland J. B. , Munkvold G. P.
Published: July 2010

Integrating selection for agronomic performance and quantitative resistance to crown rust, caused by Puccinia coronata Corda var. avenae W.P. Fraser & Ledingham, in oat (Avena sativa L.) requires an understanding of their genetic relationships. This study was conducted to investigate the genetic relationships of crown rust resistance, grain yield, test weight, and seed weight under both inoculated and fungicide‐treated conditions. A Design II mating was performed between 10 oat lines with putative partial resistance to crown rust and nine lines with superior grain yield and grain quality potential. Progenies from this mating were evaluated in both crown rust‐inoculated and fungicide‐treated plots in four Iowa environments to estimate genetic effects and phenotypic correlations between crown rust resistance and grain yield, seed weight, and test weight under either infection or fungicide‐treated conditions. Lines from a random‐mated population derived from the same parents were evaluated in three Iowa environments to estimate heritabilities of, and genetic correlations between, these traits. Resistance to crown rust, as measured by area under the disease progress curve (AUDPC), was highly heritable (H = 0.89 on an entry‐mean basis), and was favorably correlated with grain yield, seed weight, and test weight measured in crown rust‐inoculated plots. AUDPC was unfavorably correlated or uncorrelated with grain yield, test weight, and seed weight measured in fungicide‐treated plots. To improve simultaneously crown rust resistance, grain yield, and seed weight under both lower and higher levels of crown rust infection, an optimum selection index can be developed with the genetic parameters estimated in this study.
Selection for Greater β‐Glucan Content in Oat Grain
Authors: Cervantes‐Martinez C. T. , Frey K. J. , White P. J. , Wesenberg D. M. , Holland J. B.
Published: July 2010

Oat (Avena sativa L.) β‐glucan lowers serum cholesterol in humans. Development of oat cultivars with greater groat (caryopsis) β‐glucan content would increase the nutritional and economic value of the crop. The objectives of this experiment were to evaluate the response to phenotypic selection among individual S0 plants for greater groat β‐glucan content in two genetically broad‐based populations; to compare selected experimental lines to standard check cultivars; and to estimate genetic variances and heritabilities and to test for nonadditive genetic variance for β‐glucan content. We measured groat β‐glucan contents of check cultivars and parental lines and random S0:1 lines from initial and selected generations of each population grown in field experiments in 1996 and 1997 at two Iowa locations. Mean β‐glucan content increased from 53.9 to 59.9 g kg−1 in one population, and from 63.5 to 66.0 g kg−1 in the other, following selection. Genetic variance of β‐glucan content decreased by 9 to 22% following selection, but heritability for β‐glucan content did not change significantly. Heritability estimates ranged from 0.80 to 0.85 on a line mean basis. Additive variance was the only substantial component of genetic variance. Some experimental lines had significantly greater β‐glucan content than the best check cultivars and lines. Phenotypic selection for greater groat β‐glucan content will be effective for developing cultivars with elevated β‐glucan contents.
Effect of Crop Rotation and Cultivar Resistance on Seed Yield and the Soybean Cyst Nematode in Full‐Season and Double‐Cropped Soybean
Authors: Long J. H. , Todd T. C.
Published: July 2010

Soybean cyst nematode (Heterodera glycines Ichinohe) can cause considerable damage to soybean [Glycine max (L.) Merr.], especially in western USA growing areas that are newly infested. The objective of this study was to find cultural practices that reduce cyst nematode effect on soybean in this region. Four management systems, one having continuous susceptible soybean, a second consisting of a 3‐yr rotation with 2 yr of a nonhost crop followed by susceptible soybean, and two 4‐yr rotations alternating a susceptible and resistant cultivar with non‐host crops, were investigated at nematode‐infested and noninfested locations. One 4‐yr rotation had full‐season soybean while the other had double‐crop soybean. Data included soybean seed yield, yield components, and cyst nematode egg density. Grain yields of full‐season, SCN‐susceptible ‘Stafford’ were similar in all rotations at each location. Nonhost crops reduced nematode densities from 4000 eggs 100 cm−3 in continuously cropped SCN‐susceptible plots to 1000 and 500 eggs 100 cm−3 in 3‐ and 4‐yr rotations, respectively. However, nematode numbers rapidly increased to more than 5000 eggs 100 cm−3 by seasons end when susceptible soybean was grown. The SCN‐susceptible cultivar produced 33% less grain and pods than did the SCN‐resistant cultivar, Manokin, at the infested location while the cultivars yielded similarly at the noninfested site. Full‐season and double‐cropped soybean reacted similarly to SCN. Crop rotation reduced cyst nematode numbers, but this benefit did not reduce yield losses on subsequent SCN‐susceptible soybean as numbers rapidly climbed to damaging levels.
Dollar Spot and Brown Patch Fungicide Management Strategies in Four Creeping Bentgrass Cultivars
Authors: Settle Derek , Fry Jack , Tisserat Ned
Published: July 2010

New creeping bentgrass (Agrostis palustris Huds.) cultivars should be thoroughly evaluated for disease resistance and fungicide application strategies for inclusion in integrated pest management plans. Our objectives were to evaluate dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kühn) severity, and turf quality of ‘L‐93’, ‘Penncross’, ‘Providence’, and ‘Crenshaw’ creeping bentgrass managed using preventive, curative, and weather model‐based fungicide application strategies. This field study was conducted on a sand‐based putting green in Manhattan, KS, from 1997 through 1999. Nonfungicide‐treated L‐93 exhibited greatest resistance to dollar spot; Penncross and Providence were intermediate; and Crenshaw was most susceptible. Crenshaw exhibited greater brown patch susceptibility than other cultivars in 1998, but was similar to L‐93 in 1999. Greater flexibility in imposing a disease control strategy was afforded by using a disease‐resistant (i.e., L‐93), rather than a disease‐susceptible (i.e., Crenshaw) cultivar. Dollar spot was controlled in L‐93 using preventive fungicide applications on 14‐ or 28‐d intervals, preventive low‐rate applications of chlorothalonil (tetrachloroisophthalonitrile, 3.5 kg a.i. ha−1) every 7 d, or a curative fungicide application when an increase in the disease was observed. In Crenshaw, only the 14‐d preventive fungicide regime effectively controlled dollar spot. Considering all cultivars across the 3‐yr period, fewer fungicide applications were made using a curative (n = 11–17) than a preventive (n = 30) strategy. The curative strategy was effective when dollar spot, but not when brown patch was the primary disease.
Penman Monteith Crop Coefficients for Use with Desert Turf Systems
Authors: Brown Paul W. , Mancino Charles F. , Young Michael H. , Thompson Thomas L. , Wierenga Peter J. , Kopec David M.
Published: July 2010

Irrigation scheduling systems which estimate actual evapotranspiration (ETa) by adjusting reference evapotranspiration (ETo) with crop coefficients (Kcs) have been suggested as a means of improving irrigation management of turfgrass in the desert southwest. The objective of this study was to develop turfgrass Kcs for use with ETo computed by the Penman Monteith Equation recommended by the United Nations Food and Agricultural Organization (FAO). Crop coefficients were developed for fairway quality ‘Tifway’ bermudagrass (Cynodon dactylon L. × C. transvaalinsis Davy) in summer and overseeded ‘Froghair’ intermediate ryegrass (Lolium perenne × L. multiflorum) in winter by relating daily measurements of ETa obtained from weighing lysimeters to ETo computed with meteorological data. Monthly and seasonal Kcs were developed by (i) computing the mean of individual daily Kcs, (ii) dividing cumulative ETa by cumulative ETo for the period, and (iii) computing the slope of least squares regression lines relating ETa to ETo. The three computation procedures did not greatly affect the resulting Kc value. Bermudagrass Kcs ranged from 0.78 in June to 0.83 in September, with monthly variation related to turf growth rate. Use of a constant Kc of 0.80 would suffice for estimating ETa in summer. Monthly Kcs for intermediate ryegrass ranged from 0.78 in January to 0.90 in April and varied in relation to mean air temperature. Increased bulk surface resistance resulting from chill‐induced reductions in stomatal conductance and/or a reduction in turf growth rate and leaf area index may lower ETa and Kcs during the colder winter months, making use of a constant seasonal Kc less suitable in winter. An inverse linear relationship was obtained between the coefficient of variation of mean monthly Kc and the ratio of measured to theoretical clear sky solar radiation, indicating Kcs are less reliable during periods of cloudy weather.
Severity of Gray Leaf Spot in Perennial Ryegrass as Influenced by Mowing Height and Nitrogen Level
Authors: Williams D. W. , Burrus P. B. , Vincelli P.
Published: July 2010

Gray leaf spot [Pyricularia grisea (Cooke) Sacc.] has become a great concern for turf managers. Large losses of perennial ryegrass (Lolium perenne L.) turf caused by P. grisea epidemics have occurred in recent years. This field study was conducted to investigate the effects of two maintenance practices on the severity of gray leaf spot in perennial ryegrass managed as golf course fairways and roughs. The study was initiated in 1998 and repeated in 1999 at Lexington, KY. Treatments were two mowing heights (1.9 and 6.4 cm) with a split‐plot treatment of monthly applications of water‐soluble nitrogen (N) fertilizer between April and August at rates of 0, 36.6, and 73.2 kg N ha−1 Disease severity was rated visually as the percent of plot area blighted, and areas under disease progress curves (AUDPC) were compared statistically. There were no significant interactions (P ≥ 0.05) between mowing heights and N rates in either year. In both years, AUDPC data showed no significant differences (P ≥ 0.05) due to the effects of mowing heights. The effect of N fertility was significant (P ≤ 0.05) for both years. Plots treated with the highest N rate had significantly more gray leaf spot than those treated with the lowest N rate. Data indicated that turf managers may expect gray leaf spot to be equally severe between 1.9‐ and 6.4‐cm mowing heights, and that applications of water‐soluble N prior to or during environmental conditions conducive for gray leaf spot development should be avoided.
Analysis of Genetic Diversity in Theobroma cacao with Emphasis on Witches' Broom Disease Resistance
Authors: Marita J. M. , Nienhuis J. , Pires J. L. , Aitken W. M.
Published: July 2010

To facilitate the identification of Theobroma cacao L. that possess desirable traits to meet changing production and market conditions, there is a need to understand the genetic relationships among T. cacao germplasm. In addition, new cultivars are needed to provide more broadly based resistance to devastating diseases such as witches' broom disease [Crinipellis perniciosa (Stahel) Singer]. A subset of 270 T. cacao accessions based on (i) witches' broom disease resistance data, (ii) genetic characterization experiments, and (iii) a random sampling of recently acquired accessions was selected from the extensive germplasm collection at the Centro de Pesquisa do Cacau (CEPEC; Itabuna, Bahia, Brazil) in collaboration with Fazenda Almirante, a division of M&M Mars Incorporated in Itajuipe, Bahia, Brazil. Estimates of genetic distance based on random amplified polymorphic DNA (RAPD) markers were used to evaluate the genetic diversity among the selected accessions. Incorporation of recently acquired accessions (Accessions 181–270) did not increase the breadth of the distribution of genetic diversity already present within the “original” group sampled (Accessions 1–180) suggesting new accessions collected from already sampled geographic regions do not increase the existing genetic diversity in the germplasm collection. In addition, differences in RAPD marker frequencies were associated with accessions that had a high threshold of tolerance to witches' broom disease. Most accessions exhibiting tolerance to witches' broom disease were from the Upper Amazon region, with the exception of SGU 26, a hybrid from Guatemala. This suggests that the Upper Amazon is not the only region to have genes for resistance to witches' broom disease and stresses the need for further collection and examination of germplasm from other regions.
Evaluation of Marker‐Assisted Introgression of Yield QTL Alleles into Adapted Soybean
Authors: Reyna N. , Sneller C. H.
Published: July 2010

Genetic diversity is limited in southern elite soybean [Glycine max (L.) Merrill]. Introgression of diverse alleles for yield may increase the rate of yield improvement. Beneficial yield alleles at three quantitative trait loci (QTL) from the northern cultivar Archer have been tagged with molecular markers. The objective of this research was to assess the value of the three Archer alleles for increased yield in southern environments and genetic backgrounds. Four sets of near isogenic lines (NIL) for each quantitative trait locus (QTL) were derived from heterozygous F6 plants identified from the crosses of Archer × Asgrow A5403 and Archer × Pioneer 9641. The NIL sets were tested at four environments across 2 yr. Data was collected on yield, height, and maturity. None of the marker effects were significant for any of the three QTL for any trait, when averaged over all sets or for individual sets. The results suggest that the Archer alleles are not superior to the southern alleles when tested in southern environments. Archer has low relative yield in the South, while in the original mapping study Archer was the high‐yield adapted parent. The superior genetic value assigned to the Archer yield QTL may not be readily transported to populations or environments where Archer is inferior. Recombination and epistasis may also have affected the ability of the Archer markers and QTL to improve yield. Our results indicate that it may be difficult to capture the value assigned to QTL alleles derived from diverse parents with variable relative genetic value when the alleles are introgressed into populations with different genetic backgrounds, or when tested in different environments.
Molecular Genetic Analysis of U.S. and Chinese Soybean Ancestral Lines
Authors: Li Zenglu , Qiu Lijuan , Thompson Jeffery A. , Welsh Molly M. , Nelson Randall L.
Published: July 2010

Most of the U.S. soybean [Glycine max (L.) Merr.] ancestral lines were introduced from China, but nothing is known of the genetic relationships among the ancestors of modern U.S. and Chinese cultivars. The objectives of this research were to measure the variation among the major ancestors of U.S. and Chinese cultivars, to establish the genetic relationships among these U.S. and Chinese soybean ancestral lines, and to determine the relationship between geographical origin and genetic diversity. Genomic DNA from these lines was characterized by random amplified polymorphic DNA (RAPD) with 35 selected decamer primers. On the basis of the presence or absence of amplified DNA fragments, simple matching coefficients were used to calculate genetic similarities between pairs of lines. Cluster analyses generally separated the ancestral gene pools of the USA and China. Clusters reflected the geographical origin of the lines. Large differences exist between northern U.S. and Chinese ancestral lines and central and southern Chinese ancestral lines. The pattern of diversity found within the U.S. and Chinese ancestors can aid breeders in selecting parental lines to more efficiently exploit the diversity found in these two major gene pools.
Genetic Analysis of Seedling Growth under Cold Temperature Stress in Grain Sorghum
Authors: Yu Jianming , Tuinstra Mitchell R.
Published: July 2010

Planting of grain sorghum [Sorghum bicolor (L.) Moench] earlier in the season should contribute to a longer growing season and more effective utilization of late spring and early summer rainfall, but early planting is hindered by poor seedling vigor under cold temperature conditions. Sources of cold tolerance have been identified, but little is known about the inheritance of this trait. This study was conducted to determine combining ability for seedling growth characteristics under cold temperature conditions in genetically diverse sorghum lines using a Design‐II mating scheme. Parental lines and hybrids were evaluated under early and normal planting conditions in the field. The traits measured included emergence, emergence index, leaf number, vigor, and dry weight. Significant differences were observed among entries. Among hybrids, these differences were primarily due to effects of general combining ability. These results indicate that general combining ability is more important than specific combining ability in breeding for seedling vigor in sorghum. Heterosis had favorable effects on all seedling traits measured.
Latitudinal and Longitudinal Adaptation of Smooth Bromegrass Populations
Authors: Casler M. D. , Vogel K. P. , Balasko J. A. , Berdahl J. D. , Miller D. A. , Hansen J. L. , Fritz J. O.
Published: July 2010

Breeding progress has been slow in smooth bromegrass (Bromus inermis Leyss) since its introduction to North America. Much of the variability among cultivars appears to have arisen by natural selection and adaptive responses. The objective of this study was to determine if smooth bromegrass cultivars differ in latitudinal or longitudinal adaptation, as measured by forage yield, and if that variability relates to their breeding or selection history. The target region was defined as the Great Plains to the East Coast of the USA, from 38 to 47°N latitude. Twenty‐nine cultivars and experimental populations were evaluated for forage yield at up to seven locations ranging from central to eastern USA. Populations were classified according to pooled population main effect and population × location interaction effect (G+GL deviations). Cluster analysis resulted in eight clusters that explained 90% of the variation among G+GL deviations. One cluster consisted of populations average in adaptation, four clusters consisted of populations that were largely unadapted across the entire region, and three clusters consisted of populations that were specifically adapted to the entire region or a large part thereof. Much of the grouping and adaptation characteristics could be explained by similar pedigrees, selection history, and selection location. However, the phenotypic similarity of some superior, but divergent‐pedigree populations suggested that alleles for high and stable forage yield in smooth bromegrass probably exist in numerous germplasm sources. Despite a history of little to no gains in forage yield, these results suggest unrealized potential for future improvement of forage yield of smooth bromegrass across a broad geographic region.
Detection and Mapping of a Major Locus for Fusarium Wilt Resistance in Common Bean
Authors: Fall A. L. , Byrne P. F. , Jung G. , Coyne D. P. , Brick M. A. , Schwartz H. F.
Published: July 2010

Fusarium oxysporum Schlectend. Fr. f. sp. phaseoli J.B. Kendrick and W.C. Snyder (FOP) is a vascular pathogen that causes Fusarium wilt in common bean (Phaseolus vulgaris L.). This disease is an increasing problem in the western U.S., and exploitation of genetic resistance is considered the most feasible control method. The objective of this study was to detect quantitative trait loci (QTL) for Fusarium wilt resistance in a population derived from an interracial cross between FOP‐susceptible Belneb RR‐1 (race Durango) × FOP‐resistant A55 (race Mesoamerica). Seventy‐six F6‐derived recombinant inbred lines (RILs) were screened for disease severity in greenhouse inoculations and rated on a scale of 1 (resistant) to 9 (susceptible). The phenotypic data were compared to existing random amplified polymorphic DNA (RAPD) marker data using single‐factor analysis of variance. Marker U20.750 on linkage group (LG) 10 accounted for 63.5% of the phenotypic variance for this trait. Lines exhibiting the A55 banding pattern at this locus had disease severity scores that averaged 3.6 points lower than lines with the Belneb RR‐1 pattern. Two additional markers, AD4.450 on LG 3 and K10.700 on LG 11, were significant (P < 0.01) in single‐factor analysis of variance, but only marker U20.750 on LG 10 remained significant when composite interval mapping (CIM) was conducted. The tight linkage between the putative QTL and U20.750, as indicated by CIM, makes this marker a promising candidate for conversion to a sequence‐characterized amplified region (SCAR) for use in marker‐assisted selection in Fusarium wilt resistant common bean cultivar development.
Major and Minor Genes for Stimulation of Striga hermonthica Seed Germination in Sorghum, and Interaction with Different Striga Populations
Authors: Haussmann B. I. G. , Hess D. E. , Omanya G. O. , Reddy B. V. S. , Welz H. G. , Geiger H. H.
Published: July 2010

The parasitic angiosperms Striga hermonthica (Del.) Benth. and S. asiatica (L.) Kuntze severely constrain cereal production in sub‐Saharan Africa. A resistance mechanism to these root parasites in sorghum [Sorghum bicolor (L.) Moench] is low exudation of striga seed germination stimulants. The trait is controlled by a single recessive gene in the sorghum × S. asiatica interaction, but information is lacking for S. hermonthica Objectives of this investigation were to study the inheritance of stimulation of S. hermonthica seed germination in three F2 and two F3:5 recombinant inbred populations of sorghum, and to determine the effects of striga populations from Mali, Niger, and Kenya on the effectiveness of the low‐stimulant character. An agar‐gel assay was employed for this purpose. In this laboratory assay, the maximal distance between sorghum rootlets and germinated striga seed (“maximal germination distance”) reflects the magnitude of germination stimulation. Bimodal frequency distributions supported the hypothesis of one recessive gene with a major effect for low maximal germination distance in progenies from crosses of low‐stimulant lines (Framida, IS 9830) with a high‐stimulant line (E 36‐1), tested with striga from Mali or Niger. However, low‐ versus high‐stimulant classes were not always clearly distinct, indicating that additional minor genes modified maximal germination distance in the progenies. The Kenyan striga population led to higher maximal germination distances and larger overlap of low‐ and high‐stimulant classes than striga from Mali or Niger. Minor genes seemed therefore more important with Kenyan striga seed. The general involvement of minor genes in stimulating S. hermonthica seed germination was also evident from the heritable, quantitative variation observed in F3:5 lines derived from a cross of the high‐stimulant lines N 13 and E 36‐1. Because of the higher sensitivity of Kenyan striga to germination stimulation, the low‐stimulant character may be less effective in Kenyan fields.
Effects of Spontaneous Heating on Estimates of Ruminal Nitrogen Degradation in Bermudagrass Hays from Two Harvests
Authors: Coblentz W. K. , Turner J. E. , Scarbrough D. A. , Coffey K. P. , Kellogg D. W. , McBeth L. J.
Published: July 2010

Estimates of rumen degradable or escape N are an important component of current nutritional models for feeding livestock, but attempts to estimate these fractions for bermudagrass [Cynodon dactylon (L.) Pers.] have been limited, and the relationship between concentrations of these fractions and spontaneous heating during bale storage has not been evaluated. The objectives of this study were to (i) assess the relationship between rumen escape or degradable N and spontaneous heating in bermudagrass hays harvested from the same site during 1998 and 1999 and (ii) correlate estimates of rumen escape and degradable N with other measures of forage nutritive value that are evaluated commonly. A preparation of Streptomyces griseus protease was utilized in an in vitro laboratory procedure to quantify rumen degradable N in hays that heated spontaneously during storage in small haystacks. Maximum temperatures in these bales ranged from 37.1 to 69.8°C over 2 yr. Rumen escape N for 40 hays ranged from 407 to 613 g kg−1 N and increased linearly (P < 0.05) with all indices of spontaneous heating in both 1998 and 1999; however, r2 statistics were highest for bales made in 1998 (r2 ≥ 0.588). Similar results were observed when ruminal escape N was expressed as a proportion of plant DM. Rumen degradable N expressed as a proportion of plant DM was related to indices of heating (P < 0.0001) when harvest years were evaluated together, but the slopes were not significant (P > 0.05) for specific harvest years.