bluuebunny/crossref_metadata_2025 huggingface dataset:
AFLP Analysis of Opium Poppy
Authors: Saunders James A. , Pedroni Monica J. , Penrose Lindsay D. J. , Fist Anthony J.
Published: July 2010

Amplified restriction fragment length polymorphic (AFLP) DNA analysis was performed on leaf samples of 40 accessions of opium poppy (Papaver somniferum L.) and two other control genera (Papaver bracteatum Lindley and Papaver setigerum DC.) from a commercial breeding collection held in Tasmania, Australia. A similarity dendrogram was produced on the basis of the analysis of all AFLP bands that ranged between 66 and 367 base pairs (bp) seen on an autoradiogram from denaturing polyacrylamide sequencing electrophoretic gels with three different primer pairs. It was necessary to combine the analysis of all three primer pairs into a single dendrogram to ensure that replicate analyses of related populations were grouped together. It was necessary to use more than one primer pair to resolve clearly the genetic relationship between the closely related plants described in this study; however, even a single primer pair could easily distinguish between populations of different poppy species. The application of AFLP DNA analysis for cultivar identification represents an efficient, reliable procedure for identifying opium poppy breeding lines in a definitive manner. This procedure required only a small amount of leaf material for analysis and the degree of the genetic relatedness was performed on autoradiographic banding patterns with commercially available software. These data were used to generate a similarity dendrogram depicting the predicted genetic relationship of the opium poppy cultivars. Opium poppy accessions sharing common parental lines could be distinguished unambiguously from poppy accessions of more distant genetic background. The banding patterns were reproducible, consistent within a genotype, and the DNA polymorphisms were frequent enough to be useful in characterizing genetic diversity in even closely related breeding lines.
Patterns of Variation in a Collection of Timothy Accessions
Authors: Casler M. D.
Published: July 2010

Cultivated timothy (Phleum pratense L.) is an important grass for hay production in temperate North America. It is under utilized in management‐intensive rotational grazing systems because of its poor persistence when frequently defoliated. The objective of this study was to evaluate the USDA‐NPGS collection of timothy accessions for agronomic traits, including persistence under frequent defoliation. Unlike previous reports for infrequent harvest systems, diploid and tetraploid species of Phleum were similar in forage yield to hexaploid P. pratense, suggesting their potential value in livestock agriculture. Cultivated accessions tended to have fewer, but larger leaves; longer and narrower panicles with a greater number of smaller seeds; lower survival under frequent defoliation; and higher forage yield than natural accessions. A considerable amount of phenotypic variation among accessions was explained by geographic source of the accessions. Twenty‐one unique phenotypic clusters were formed to account for 50% of the phenotypic variability among accessions, providing the basis for development of a core collection for P. pratense Clusters were highly differentiated on the basis of geographic origin of the accessions, underscoring the potential importance of the relationship between phenotype and geography in hexaploid timothy.
DNA Content and Ploidy Determination of Bromegrass Germplasm Accessions by Flow Cytometry
Authors: Tuna Metin , Vogel Kenneth P. , Arumuganathan K. , Gill Kulvinder S.
Published: July 2010

Species of the genus Bromus represent ploidy states from diploid to decaploid. Ploidy determination of Bromus germplasm is necessary before it can be effectively used in breeding or genetic studies. The objective of this study was to characterize the ploidy of 322 accessions of four Bromus species [Bromus inermis Leyss, B. riparius Rehm, B. biebersteinii Roem and Schult., and B. inermis ssp. pumpellianus (Scribn) Wagnon] that are in the USDA National Plant Germplasm System (NPGS). Flow cytometry was used to determine DNA content of 10 plants of each accession. Mean DNA contents were correlated to ploidy level with root tip chromosome counts on selected accessions whose DNA content indicated that they represented different ploidy levels. On the basis of DNA content (pg 2C−1 = DNA content of a diploid somatic nucleus) and chromosome counts, mean DNA content and chromosome number was 22.62 pg 2C−1 for octaploid B. biebersteinii (2n = 8x = 56), 26.07 pg 2C−1 for decaploid B. biebersteinii (2n = 10x = 70), 11.74 pg 2C−1 for tetraploid B. inermis (2n = 4x = 28), 22.28 pg 2C−1 for octaploid B. inermis (2n = 8x = 56), 22.72 pg 2C−1 for octaploid B. inermis ssp. pumpellianus (2n = 8x = 56), 26.5 pg 2C−1 for decaploid B. inermis ssp. pumpellianus (2n = 10x = 70), 6.14 pg 2C−1 for diploid B. riparius (2n = 2x = 14), 22.15 pg 2C−1 for octaploid B. riparius (2n = 8x = 56), and 26.64 pg 2C−1 for decaploid B. riparius (2n = 10x = 70). Standard deviations of the mean values were 0.88 pg 2C−1 or less. Most B. inermis and B. inermis ssp. pumpellianus accessions were octaploid (93.75%), while the majority of the B. riparius and B. biebersteinii were decaploid (92.30%). The B. inermis and related species in the USDA NPGS were collected primarily from areas in the former USSR. The NPGS bromegrass germplasm could be enhanced by collections from western and central Europe, the Middle East, and China.
Incompatibility Systems in Switchgrass
Authors: Martínez‐Reyna J. M. , Vogel K. P.
Published: July 2010

Switchgrass (Panicum virgatum L.), a cross‐pollinated perennial, produces very little or no seed when self‐pollinated, indicating the presence of self‐incompatibility mechanisms. Knowledge of self‐incompatibility mechanisms is required to use germplasm effectively in a breeding program. The objective of this study was to characterize features of the incompatibility systems in switchgrass. Seed set and seed characteristics of reciprocal matings of tetraploid, octaploid, and tetraploid × octaploid plants were used as measures of incompatibility. Both bagged mutual pollination and manual emasculation and pollination methods were used to make crosses. The percentages of self‐compatibility in the tetraploid and octaploid parent plants were 0.35 and 1.39%, respectively. Prefertilization incompatibility in switchgrass is apparently under gametophytic control, since there were significant differences in percentage of compatible pollen as measured by percentage of total seed set between reciprocal matings within ploidy levels. Results indicated that the prefertilization incompatibility system in switchgrass is similar to the S‐Z incompatibility system found in other members of the Poaceae. A postfertilization incompatibility system also exists that inhibits intermatings among octaploid and tetraploid plants. In these interploidy crosses, two very distinctive types of abnormal seed were found. When the female parent was the tetraploid plant, the resulting seed was small and shriveled, while when the female parent was the octaploid, small seed with floury endosperm was obtained. These results are similar to those obtained for endosperm incompatibility due to the endosperm balance number system found in other species.
Analysis of Combining Ability for Ergot Resistance in Grain Sorghum
Authors: Reed J. D. , Tuinstra M. R. , McLaren N. W. , Kofoid K. D. , Ochanda N. W. , Claflin L. E.
Published: July 2010

Ergot caused by Claviceps africana Frederickson, Mantle & de Milliano has become an important constraint to F1 hybrid seed production in North and South America. Identification and utilization of sources of host‐plant resistance would contribute to the effective control of this disease. A Design II mating scheme was used to test the combining ability of four reported sources of ergot resistance in sorghum [Sorghum bicolor (L) Moench]—IS8525, IS14131, IS14257, and IS14357. Male‐sterile hybrids of these accessions and a susceptible check, TxARG1, were produced using five cytoplasmic‐genetic male‐sterile seed parents—A3Tx430, A3Tx436, A3Tx7000, A3KS70, and A3Tx2737. Parent lines and hybrids were planted in three replications at three locations and were evaluated for ergot resistance following artificial inoculation at flowering. Differences in ergot severity and ergot breakdown point (EBP) were used to quantify differences in resistance. The combined analysis of variance showed that the expression of ergot resistance was not stable with significant entry × location interaction. The analyses from two locations showed significant differences among hybrids, while the third location showed no differences. Regression analyses were performed to determine the relationship between weather variables at flowering and observed ergot severity. These analyses indicated a strong relationship between maximum daily temperature and ergot severity. Ergot infection was higher in cooler environments regardless of genetic background. IS8525 appeared to have the highest expression of ergot resistance in male‐sterile genetic backgrounds on the basis of EBP and ergot severity ratings; however, the expression of resistance was only effective within a limited temperature range.
Stability of Grain Yield, Endosperm Modification, and Protein Quality of Hybrid and Open‐Pollinated Quality Protein Maize (QPM) Cultivars
Authors: Pixley Kevin V. , Bjarnason Magni S.
Published: July 2010

Quality protein maize (Zea mays L.) (QPM) can help alleviate human malnutrition and reduce costs of animal feed because it contains the opaque‐2 mutation, which results in increased lysine and tryptophan concentrations and a higher biological value as a food than normal maize. To be commercially successful, however, QPM cultivars must be agronomically competitive with normal‐endosperm alternatives while consistently achieving expected protein quality and endosperm modification (i.e., translucent or near‐normal phenotype) standards. To assess stability of grain yield, protein content and quality, and endosperm modification of QPM cultivars, we evaluated 18 single‐cross, 18 three‐way, and 18 double‐cross hybrids, and eight open‐pollinated cultivars (OPCs) grown at 13 tropical locations on four continents. Hybrids averaged 13% higher grain yield than OPCs (5.97 and 5.17 Mg ha−1), whereas protein concentration in grain was 2% greater for the OPC relative to hybrid cultivars (94.6 and 92.4 g kg−1). Endosperm modification score and tryptophan concentration in protein were similar for all cultivar types. Genotype × environment interactions and sums of squares for deviations from linear regression S2d for grain yield and protein concentration in grain were largest (indicating least stability) for single‐cross hybrids, followed by three‐way, double‐cross, and open‐pollinated cultivars (OPCs), successively. The reverse trend was observed for endosperm modification score, suggesting that more homogeneous cultivars had greater stability for this trait. Additive main effects and multiplicative interactions (AMMI) analysis indicated that genotype × environment interaction effects for grain yield and endosperm modification score were different for hybrids than OPCs; certain environments favored either hybrids or OPCs. In conclusion (i) protein quality and endosperm modification score were always within expected values for QPM and (ii) tryptophan concentration in protein was the most stable trait, followed by protein concentration in grain, then endosperm modification score and finally grain yield.
Genetic Variation in Physiological Discriminators for Cold Tolerance—Early Autotrophic Phase of Maize Development
Authors: Lee E. A. , Staebler M. A. , Tollenaar M.
Published: July 2010

Earlier spring planting to maximize the duration of the growing season has increased the importance of early‐season cold tolerance in maize (Zea mays L.). The objectives of this study were to assess the response of several physiological parameters associated with cold tolerance in maize during early autotrophic development and to quantify variability in the response to cold stress among 49 maize inbred lines. At the 7‐leaf tip stage, maize inbred lines were subjected to two day/night temperature regime treatments, 25/15°C (control) and 15/3°C (cold). Carbon exchange rate (CER), leaf chlorophyll content, quantum efficiency of Photosystem II, leaf conductance, dry weight, root/shoot ratio, and rate of development were measured at the 8‐leaf tip stage for genotypes under both treatments. The cold treatment effects were significant for all parameters except root/shoot ratio. Genetic diversity for most traits investigated was observed for the response of the inbred lines to cold stress. Results of this study show that leaf CER and rate of development are good discriminators of cold tolerance during early phases of development.
Nitrogen Application and Critical Shoot Nitrogen Concentration for Optimum Grain and Seed Protein Yield of Pearl Millet
Authors: Kennedy Charles , Bell Paul , Caldwell David , Habetz Bob , Rabb Jim , Alison M. A.
Published: July 2010

Pearl millet [Pennisetum glaucum (R) Br.] is a promising alternative grain crop for the Southeast and mid‐South regions of the USA, but additional N fertility information is needed to optimize its production. Identification of a critical tissue N level at early growth stages is necessary to determine the need for subsequent applications of N. Field experiments were conducted to determine the response of hybrid ‘HGM 100’ grain yield, protein yield, and shoot N concentration to N application rate and to determine the relationship of grain yield and protein yield with shoot N concentration at different growth stages. Grain yield response to N fertilizer applications from 0 to 168 kg ha−1, in 34‐kg increments, varied among five field environments ranging from sandy loam to silty clay loam soils and resulted in a moderately low correlation (r2 = 0.36). Relative total protein yield was more consistent (r2 = 0.67). Tissue N concentration of shoots harvested 44 ± 4 d after seeding [early boot(EB)] was related to relative grain yield (r2 = 0.65). A critical N concentration of 31 g kg−1 dry matter (dm), determined by regression and “old” Cate–Nelson procedures, resulted in optimum grain yield. On a per hectare basis, total relative protein yield also correlated moderately high with shoot tissue N concentration at EB (r2 = 0.70). The use of Cate–Nelson procedures determined a critical N concentration in shoot tissue at EB of 32 g kg−1 dm. Determination of a critical N level at an earlier growth stage resulted in low correlations with yield parameters. On the basis of critical values at the EB stage, N amendments could possibly be applied in time to enhance some yield components, although the effective application window is narrow.
Effect of Priming Temperature on Storability of Primed sh‐2 Sweet Corn Seed
Authors: Chiu K. Y. , Chen C. L. , Sung J. M.
Published: July 2010

Priming offers a means to raise seed performance in many crop species, but the longevity of primed seed is generally decreased. The exact causes of the more rapid deterioration of primed seed are still not established. This study evaluated the effects of priming and storage temperatures on germination and antioxidative activities of sweet corn seed (Zea mays L.) carrying the shrunken‐2 (sh‐2) gene. Seed were solid‐matrix primed in moistened vermiculite at 10, 15 or 20°C for 36 h, then air‐dried to near original moisture level. Primed seed were stored at 25, 10, or −80°C for up to 12 mo. Solid‐matrix priming improved germination, reduced lipid peroxidation, enhanced antioxidative activities, and increased seedling growth. Seed longevity was decreased when 20°C‐primed seeds were stored at 25°C for 12 mo. Seed primed at 10 and 15°C had superior viability and vigor responses compared with nonprimed control seeds when they were stored at 25°C for 12 mo. Reduced storability of the 20°C‐primed seeds was attributable to enhanced peroxidation and decreased antioxidative activities. Storage at 10 or −80°C extended the storability of matrix primed sh‐2 seed for at least 12 mo. Enhanced antioxidative activity plays a role in maintaining the viability and vigor responses of solid matrix primed seed stored at cool (10°C) or subzero (−80°C) temperatures. Moreover, 10 or 15°C‐primed sh‐2 seed can retain viability for 12 mo, provided that the primed seed is stored at 10°C.
Tall Fescue Performance Influenced by Irrigation Scheduling, Cultivar, and Mowing Height
Authors: Richie W. E. , Green R. L. , Klein G. J. , Hartin J. S.
Published: July 2010

Prudent water management on turfgrass is an important issue. There is a need to define best management practices (BMPs), including optimal irrigation frequency for tall fescue (Festuca arundinacea Schreb.) when irrigated at a level that would be less than a typical industry practice of ETcrop/irrigation uniformity, where ETcrop = crop evapotranspiration = reference evapotranspiration (ETo) × crop coefficient (Kc). A 2‐yr field study was conducted in Riverside, CA, to determine if the visual quality of tall fescue could be improved during the warm season by altering irrigation frequency (two, three, or four irrigation events per week), cultivar selection (a dwarf cultivar, ‘Shortstop’ or a turf‐type cultivar, ‘Jaguar III’), and mowing height (3.8 or 6.4 cm) when irrigated at 80% ETcrop/irrigation uniformity. Volumetric soil water content at the 30‐, 61‐, and 91‐cm depths was also measured on each Jaguar III sub‐subplot. During the first year, visual quality was significantly higher for Jaguar III and the lower mowing height. During the second year, overall visual turfgrass quality was significantly highest for plots irrigated twice per week. Visual turfgrass quality was significantly correlated with soil water content. In summary, data from this study support recommendations for deeper, less frequent irrigation of established tall fescue grown on sandy loam soils in southern California interior valleys with an irrigation budget of 80% ETcrop/irrigation uniformity.
Relative NaCl Tolerance of Kentucky Bluegrass, Texas Bluegrass, and Their Hybrids
Authors: Suplick‐Ploense M. R. , Qian Y. L. , Read J. C.
Published: July 2010

Government regulations to force water conservation have escalated the use of secondary water high in soluble salts for turfgrass irrigation in the arid and semiarid western USA, thus increasing the need for more salt‐tolerant turfgrasses. This study was initiated to determine the variability in salt tolerance within and among two Poa species and their hybrids. Two experiments were conducted during 2000 in the greenhouse at Fort Collins, CO, in solution culture to examine the effects of NaCl on leaf firing and shoot and root growth reduction of nine Kentucky bluegrass (KBG; Poa pratensis L.) cultivars representing three ecotypes, three Texas bluegrass (TBG; P. arachnifera Torr.) accessions, and five of their hybrids (P. pratensis × P arachnifera). In Exp. I, conducted during late winter through spring 2000, overall salt tolerance based on leaf firing and electrical conductivity (EC) of 50% shoot growth reduction (ECshoot 50) placed seven KBG cultivars in the most tolerant group. In Exp. II, conducted during summer though early fall 2000, overall salt tolerance rankings placed 4 KBG and 3 TBG cultivars in the most tolerant group. On the basis of percentage leaf firing and the salinity levels that caused 25 and 50% shoot growth reduction, compact (low, compact growth habit) and aggressive (aggressive, lateral growth habit) KBG ecotypes showed more salt tolerance than common ecotypes in both Exp. I and II. A broad range of variability in leaf firing and shoot and root growth reduction in response to salinity was found to exist within and among these Poa species and their hybrids, indicating that improvement in the salt tolerance of bluegrasses may be possible. Additionally, differences in salt tolerance of KBG and TBG between Exp. I and Exp. II suggested that environmental conditions could affect bluegrass salt tolerance expression.
Modified Rapid DNA Extraction Protocol for High Throughput Microsatellite Analysis in Wheat
Authors: Hill‐Ambroz Kristi L. , Brown‐Guedira Gina L. , Fellers John P.
Published: July 2010

New technology is allowing marker‐assisted selection to fulfill the promise of increasing efficiency of cultivar development. However, these techniques depend upon the ability to extract DNA from large populations of plants. The objective of this project was to develop a high‐throughput DNA extraction procedure without the need for greenhouse space or growing wheat (Triticum aestivum L.) plants. A sodium hydroxide rapid DNA extraction was modified for a 96‐well format to reduce costs. Seeds were germinated in 8‐well tissue culture plates, and 4‐d‐old seedling tissue was used to extract DNA by means of sodium hydroxide methodology. Approximately 1 μg of genomic DNA per 10 mg of tissue was isolated at a cost of about $0.10. The DNA quality was verified by amplification of microsatellite markers. Results were consistent with either fresh or stored tissue extracts. This technique allows one person to extract nearly 1000 storage‐stable DNA samples daily, while keeping costs at a minimum.
Variation of Condensed Tannins in Roundhead Lespedeza Germplasm
Authors: Springer T. L. , McGraw R. L. , Aiken G. E.
Published: July 2010

Roundhead lespedeza, Lespedeza capitata Michx., is a deep‐rooted, perennial legume native to the eastern and central USA and is relatively common on remnant upland prairies throughout the Midwest. Information on condensed tannin (CT) concentrations from different plant parts is needed for cultivar development and also to provide data for developing management and feeding strategies. The objectives of this study were to determine variation of CT concentrations in roundhead lespedeza leaves, stems, and inflorescences; evaluate genotype variation over environments; and select germplasm lines that could be used for breeding parents and/or bulked into a synthetic variety. Thirty‐nine roundhead lespedeza plant introductions (PI) were sampled from replicated nurseries grown in two environments in 1996. Plant shoots were collected at flowering and seed filling. Each plant shoot sample was divided into leaf, stem, and inflorescence. Condensed tannin concentrations were determined by means of a modified vanillin–HCl method. We found that variation due to the environment was low, variation due to genotype was high, and variation due to genotype × environment interaction was high. Of these 39 plant introductions, we selected eight that were common to both environments and had low CT concentrations in leaves at flowering. The CT content of these plant introductions, however, was still relatively high when compared with sericea lespedeza [Lespedeza cuneata (Dumont) G. Don] that was bred for low tannin content. Collections should be made from a larger geographical region to look for germplasm with lower CT concentrations.
Salinity Tolerance in Phaseolus Species during Early Vegetative Growth
Authors: Bayuelo‐Jiménez Jeannette S. , Debouck Daniel G. , Lynch Jonathan P.
Published: July 2010

The genus Phaseolus includes important cultivated species as well as wild species with diverse ecological adaptations. Characterization of the ecological adaptations of the wild species would be useful for improved understanding, conservation, and utilization of these genetic resources. Salinity tolerance during vegetative growth was evaluated for 132 accessions for 14 wild Phaseolus species (P. acutifolius A. Gray, P. angustissimus A. Gray, P. carteri Freytag & Debouck, P. filiformis Bentham, P. glabellus Piper, P. leptostachyus Bentham, P. lunatus L., P. micranthus Hook & Arnold, P. microcarpus Mart, P. mcvaughii A. Delgado, P. oligospermus Piper, and P. vulgaris L.) and 11 accessions representing five cultivated species (P. acutifolius, P. coccineus L., P. lunatus L., P. polyanthus Greenman, and P. vulgaris) in nutrient solution containing 0 and 180 m M sodium chloride for 21 d. When plants were salinized after the emergence of the first trifoliate leaf, wild accessions of P. acutifolius, P. filiformis, P. lunatus, and P. vulgaris showed a wide range of variation in their salinity tolerance as defined by total dry weight reduction (PR) as a percentage of the unsalinized controls, salt susceptibility index (SSI), and root: shoot ratio (RSR). SSI and PR were correlated positively, indicating either trait could be used to select salt‐tolerant accessions. Cluster analysis revealed substantial intraspecific and interspecific variation in salinity tolerance. Salinity tolerance was observed in wild P. micranthus, P. mcvaughii, P. lunatus, cultivated P. coccineus, and several accessions of wild P. filiformis, and P. vulgaris Of these, P. filiformis was noteworthy in having 9 of 11 accessions rated as highly tolerant. Wild P. vulgaris was more salinity tolerant than the three cultivated P. vulgaris accessions included in the study. Many tolerant accessions originated in arid, coastal, or saline areas. We conclude that the genus Phaseolus has substantial diversity in salinity tolerance.
Heat Stress Effects on Protein Accumulation of Maize Endosperm
Authors: Monjardino Paulo , Smith Alan G. , Jones Robert J.
Published: July 2010

Heat stress is a major factor limiting crop yield in many agricultural regions. During the early stage of kernel development, heat stress is particularly detrimental to subsequent dry matter accumulation since it causes disruption of cell division, sugar metabolism, and starch biosynthesis in the endosperm. The effects of heat stress on protein accumulation, however, is less well understood. Therefore, the objective of this study was to determine the mechanisms by which heat stress decreases protein accumulation and alters composition of developing maize (Zea mays L.) kernels. In this study, maize ears were heat stressed for 2 and 4 d at continuous 35°C starting at 5 d after pollination (DAP). Endosperms were analyzed for the relative proportion of each Osborne protein solubility class fraction and for individual zein proteins. The 2‐ and 4‐d heat stress (DHS) treatment caused a 20 and 48% reduction in kernel final dry weight, respectively, and protein content was similarly reduced. Specifically, zein content was reduced by an average of 53%, but zein composition was only mildly affected. The concentrations of glutelin and albumin plus globulin tended to increase throughout most of 4‐DHS kernel development. L‐[35S]‐methionine incorporation in the zein fraction was delayed by the 4 DHS when compared to control and 2‐DHS treated kernels. Therefore, we concluded that heat stress during early stages of endosperm development repressed zein accumulation at the synthesis level. In contrast, later in development, zein accumulation appeared to be repressed mainly by protein degradation, which appears to be a part of the natural progression of kernel development since there was no apparent significant effect of heat stress treatments on this process.
Sh and Sc—Two Complementary Dominant Genes that Control Self‐Compatibility in Buckwheat
Authors: Wang Yingjie , Scarth Rachael , Campbell Clayton
Published: July 2010

Fagopyrum homotropicum Ohnishi, a wild diploid (2n = 2x = 16) species with self‐compatibility expressed by homostylic flowers, has been used for improving cultivated buckwheat, F. esculentum Moench, a self‐incompatible diploid (2n = 2x = 16) species with heterostylic pin and thrum flowers. Four crosses were made between F. homotropicum and F. esculentum pin flowers, assisted by ovule rescue in vitro, to study the inheritance and interaction of the two breeding systems in the genus Fagopyrum. The presence of homostylic or pin flowers was used to determine the expression of self‐compatibility or self‐incompatibility, respectively. The segregation ratios of the F2 progeny derived from F1 single plants, the BC1F1 generation and the F3 progeny derived from homostylic plants were used to study the inheritance of self‐compatibility. Five F2 populations fit a one‐gene 3:1 segregation ratio and did not fit a 9:7 ratio, while the other three F2 populations fit a two‐gene 9:7 ratio and did not fit a 3:1 ratio. The BC1F1 and F3 progeny segregation confirmed these observations. These results support a two‐gene model with three alleles at the first locus S and two alleles at the second locus Sc The proposed model has S for self‐incompatible thrum, Sh for self‐compatible homostyly, and s for self‐incompatible pin, with the intrallelic interaction S > Sh > s at the first locus and Sc for homostyly and sc for pin (Sc > sc) at the second locus. The two complementary dominant genes Sh and Sc control self‐compatibility (homostyly) in F. homotropicum. The one gene or two gene segregation patterns are the result of interspecific crosses with different F. esculentum genotypes.
Localization of a Quantitative Trait Locus Providing Brown Stem Rot Resistance in the Soybean Cultivar Bell
Authors: Patzoldt M. E. , Grau C. R. , Stephens P. A. , Kurtzweil N. C. , Carlson S. R. , Diers B. W.
Published: July 2010

Many soybean [Glycine max (L.) Merr.] genotypes that carry resistance to soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) from plant introduction (PI) 88788 also carry resistance to brown stem rot (BSR) caused by the soilborne fungus Phialophora gregata (Allington & Chamberlain) W. Gams f. sp. sojae Kobayashi, Yamamoto, Negishi, and Ogoshi. The objectives of our research were to map and localize BSR resistance quantitative trait loci (QTL) from Bell, a BSR resistant cultivar with SCN resistance from PI 88788. Initial mapping was done with a population of 93 F4–derived lines developed from a cross between Bell and the SCN and BSR susceptible cultivar, Colfax. Lines were evaluated for BSR resistance in two field environments, a greenhouse, and with genetic markers from linkage group (LG) J. To confirm and further localize a resistance QTL, three near isogenic line (NIL) populations were created using an F4–derived line from the Bell × Colfax population. In the F4 population, markers on LG J were significantly (P < 0.001) associated with BSR resistance in both the field (R
2 = 45%) and greenhouse (R
2 = 51%). Data from the NIL populations indicates the QTL is near the closely linked markers 21E22.sp1, 21E22.sp2, and 35E22.sp1, which is the same genetic region where Rbs1, Rbs2, and Rbs3, the three named BSR resistance genes, were previously mapped. In addition, the genetic region is tightly linked to a previously identified SCN resistance QTL from PI 88788. These results explain why many SCN resistant cultivars also carry BSR resistance and should assist breeders when selecting for resistance to both diseases.
Mapping of QTL for Embryo Size in Rice
Authors: Dong Yanjun , Tsuzuki Eiji , Kamiunten Hiroshi , Terao Hiroyuki , Lin Dongzhi
Published: July 2010

The development of molecular genetic maps has accelerated the identification and mapping of genomic regions controlling quantitative trait loci (QTL) in rice (Oryza sativa L.). Minimizing embryo size in rice would increase proportion of edible endosperm. This study was conducted to determine the genetic basis controlling embryo size of rice grains in a recombinant inbred (RI) population derived from cross of a japonica cultivar, Asominori, with an indica cultivar, IR24, by means of 289 restriction fragment length polymorphism (RFLP) markers. Two parameters, embryo length and embryo width, which represent embryo size in rice, were estimated for each RI line and their parental varieties. Continuous distributions and transgressive segregations of embryo length and embryo width in rice were observed in the RI population, suggesting that embryo size was quantitative in grains of conventional varieties. Three QTL for embryo length were detected on chromosomes 1, 2, and 3 and explained 17.9, 25.7, and 9.2%, respectively, of the total phenotypic variation. Three QTL for the embryo width were observed on chromosome 2, 8, and 10 and accounted for 13.5, 15.7, and 15.0% of total phenotypic variation, respectively. In addition, alleles with increasing and decreasing effects were detected from the both parents. The results and the tightly linked molecular markers that flank the QTL will be useful in breeding for embryo improvement in rice.
Residue Management, Seed Production, Crop Development, and Turf Quality in Diverse Kentucky Bluegrass Germplasm
Authors: Johnson R. C. , Johnston W. J. , Golob C. T.
Published: July 2010

Field burning has traditionally been used to stimulate Kentucky bluegrass (Poa pratensis L.) seed production, but air quality issues are making this practice untenable. Our objectives were to determine agronomic and crop developmental responses of 45 diverse Kentucky bluegrass entries under burned, mechanically removed, and residue‐retained management systems, assess the scope for improving yield under nonthermal residue management, and relate seed yield and turf quality factors. Compared with burned treatments, yield was reduced 27% when residue was mechanically removed from plots, and 63% when residue was retained. Higher yield was promoted by a long heading‐to‐anthesis period, a relatively short anthesis‐to‐harvest period, and an early harvest date (maturity). Although both seeds per panicle and fertile panicles per square meter were positively correlated with yield, lower yield with nonthermal residue management was closely associated with panicles per square meter. For six of the 15 highest‐yielding entries, no significant difference was found between yield in the burned and residue‐removed treatments, showing the dependence of yield on genotype under different residue management systems. Turf quality was negatively correlated with yield (r = −0.48, P < 0.01, n = 44) and seeds per panicle (r = −0.55, P < 0.01, n = 44). However, panicles per square meter were not significantly correlated with turf quality, so indirect selection for yield through genotypes with high panicles per square meter in the absence of high seeds per panicle should have minimal impact on turf quality. Sufficient variation for seed production appears available to encourage development of germplasm for nonthermal management systems.
Resistance to Tomato spotted wilt virus and Root‐Knot Nematode in Peanut Interspecific Breeding Lines
Authors: Holbrook C. Corley , Timper Patricia , Culbreath Albert K.
Published: July 2010

The peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] and Tomato spotted wilt virus (TSWV), genus Tospovirus, are economically significant pathogens of peanut (Arachis hypogaea L.) in the USA. Peanut cultivars are available that have resistance to either the peanut root‐knot nematode (PRN) or TSWV, but no cultivars are available that have resistance to both pathogens. The objective of this research was to identify peanut breeding lines that have resistance to both pathogens. We crossed interspecific peanut germplasm with two cultivars that are susceptible to both PRN and TSWV. Progenies were examined in a greenhouse screening system to measure resistance to PRN. Subsequently, this material was evaluated for resistance to TSWV in field plots. Ten breeding lines were identified which exhibited a reduction in nematode reproduction in comparison to the nematode susceptible check ‘Georgia Green’. These breeding lines also exhibited a reduction in incidence of TSWV in comparison to the TSWV susceptible check ‘COAN’. When grown in a field with pressure from both pathogens, these breeding lines had higher yield than cultivars with resistance to only one pathogen. This is the first report of peanut germplasm with resistance to both TSWV and the peanut root‐knot nematode and the first report of resistance to TSWV in interspecific peanut germplasm.
Selection of Cowpea Genotypes in Hydroponics, Pots, and Field for Drought Tolerance
Authors: Ogbonnaya C. I. , Sarr B. , Brou C. , Diouf O. , Diop N. N. , Roy‐Macauley H.
Published: July 2010

The evaluation of cowpea (Vigna unguiculata [L.] Walp.) for drought tolerance in the field is slow, laborious, and provides variable results. The objectives of the study were to assess the differences in the growth of cowpea genotypes in hydroponics, and to determine whether such differences could be associated with drought tolerance in pots and field. Four cowpea genotypes varying in drought tolerance were evaluated for differences in height, collar diameter, leaf area, shoot and root biomass, root‐shoot ratio, and root volume in hydroponics. On the basis of these results, selection of cowpea for vigorous growth under well‐watered conditions could be conducted by means of hydroponics; however, rapid selection of cowpea for drought tolerance could not be made by this technique.
Postulation of Leaf Rust Resistance Genes in Selected Soft Red Winter Wheats
Authors: Kolmer J. A.
Published: July 2010

Leaf rust, caused by the fungus Puccinia triticina Eriks., is a major disease nearly wherever wheat (Triticum spp.) is grown in the USA. Soft red winter wheat (T. aestivum L.) cultivars with varying degrees of leaf rust resistance are grown in the southern USA. The objective of this study was to characterize the seedling leaf rust resistance present in a group of 35 soft red winter wheat cultivars and 17 breeding lines. Leaf rust infection types (ITs) produced on the cultivars and lines by 16 P. triticina isolates were compared with the ITs produced on a standard set of ‘Thatcher’ near‐isogenic lines that differed for single leaf rust resistance genes. Seedling resistance genes Lr1, Lr2a, Lr9, Lr10, Lr11, Lr18, and Lr26 were postulated to be present in the soft red winter wheat cultivars and lines. Adult plant leaf rust resistance for the cultivars and lines was assessed in field plots at two locations in North Carolina in 2000. Wheat cultivars postulated or genetically determined to have the adult plant resistance genes Lr12 and Lr34 had effective leaf rust resistance in the field plots. The soft red winter wheat cultivars and lines that had seedling resistance genes Lr2a, Lr9, and Lr26 combined with adult plant resistance were highly resistant to leaf rust. Cultivars and breeding lines that had seedling resistance genes Lr1, Lr10, Lr11, and Lr18 combined with adult plant resistance had moderate to low levels of leaf rust resistance.
Yield Adjustment by Canola Grown at Different Plant Populations under Semiarid Conditions
Authors: Angadi S. V. , Cutforth H. W. , McConkey B. G. , Gan Y.
Published: July 2010

Establishing a good canola (rapeseed; Brassica napus L.) stand is difficult in the semiarid prairie region of Canada where low temperature, water stress, and soil crusting could result in poor seed bed conditions. A field study was conducted from 1999 to 2001 at Swift Current, SK, Canada, to determine the effect of a range of uniform (5 to 80 plants m−2) and nonuniform (seedlings from 1‐m lengths from two adjoining rows were removed and retained alternatively; 10 to 40 plants m−2) plant populations on yield and yield components of canola. Canola adjusted seed yield across a wide range of plant populations, although it did not compensate completely for the decreasing populations. Environmental conditions played a significant role in the expression of plasticity of canola. For example, in 2000, with slightly above‐normal growing season precipitation, canola maintained similar yield levels across a wide range of populations (20 to 80 plants m−2), while in 2001, with well below normal precipitation, seed yield declined as populations dropped below 40 plants m−2 Reducing plant population by half from 80 to 40 plants m−2 did not reduce seed yield when the reduced plant population was uniformly distributed, but reduced yield when the population was nonuniformly distributed. The primary response of canola to lower plant population was increased pods per plant through increased branching and increased pod retention at each node. The number of pods formed on primary and secondary branches increased as population decreased. Seeds per pod and seed weight were stable across populations.
Optimizing Manganese Fertilization for the Suppression of Take‐All Patch Disease on Creeping Bentgrass
Authors: Heckman J. R. , Clarke B. B. , Murphy J. A.
Published: July 2010

Take‐all patch, caused by Gaeumannomyces graminis (Sacc.) Arx. & D. Olivier var. avenae (E.M. Turner) Dennis, is a destructive disease of creeping bentgrass (Agrostis stolonifera L.). Previous research has shown that Mn fertilization can reduce the severity of take‐all patch, but further research is needed to assess the impact of Mn rate and the time of its application on disease development and on the extended residual impact of Mn fertilization on disease suppression. The objective of the current study was to determine the best rate and time of Mn application for the suppression of foliar symptoms of take‐all patch on creeping bentgrass. On a golf course fairway naturally infested with G graminis var. avenae, Mn (as MnSO4) treatments were applied as single applications in either October or April of 1998, 1999, or 2000 at 0, 2.25, 4.50, 6.75, or 9.00 kg ha−1 of Mn. The severity of take‐all patch was assessed each year during May and June when foliar symptoms were apparent. Throughout the study, compared with untreated turf, Mn effectively reduced disease severity when applied either in April or in October. Moreover, the 2.25 kg ha−1 Mn application rate was generally as effective in suppressing the disease as were higher application rates, except in the third year of the study when higher rates were more effective. Findings also suggest that across time previous applications of Mn fertilizer were less effective in suppressing take‐all patch than were the most recent applications of Mn.
Nitrogen Selection and Growth Regulator Applications for Improving Shaded Turf Performance
Authors: Steinke K. , Stier J. C.
Published: July 2010

Managing turf for shaded golf course tee boxes is difficult due to few species to choose from and a lack of defined management practices. Supina bluegrass (Poa supina Schrad.) is a novel cool‐season turfgrass with good shade tolerance at mowing heights above 2 cm. This study compared the suitability of supina bluegrass, Kentucky bluegrass (Poa pratensis L.), and creeping bentgrass (Agrostis stolonifera L.) for golf course tees under 80% shade. Treatments included three application timings of trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxo‐cyclohexane‐carboxylic acid ethyl ester] (TE) and two N types, liquid and granular. Supina bluegrass provided the best overall turf quality among the three species tested. Liquid urea (foliar uptake) improved turf quality of creeping bentgrass while Kentucky bluegrass responded better to granular urea (root uptake). Supina bluegrass response to fertilizer type was seasonally dependent. Both monthly and bimonthly applications of TE (0.05 kg ha−1) significantly improved turf quality, density, and chlorophyll levels of all species, though visual effects of bimonthly applications dissipated before subsequent applications. Creeping bentgrass divot recovery was faster than for either Kentucky bluegrass or supina bluegrass. Divot recovery was not influenced by TE or N source. Supina bluegrass had significantly greater growth rates during late autumn through spring than either Kentucky or creeping bentgrass. The best turf quality was achieved using supina bluegrass, treated monthly with TE, and fertilized with granular N in the spring and liquid N in the summer and autumn.
Nitrogen Removal by Orchardgrass and Smooth Bromegrass and Residual Soil Nitrate
Authors: Singer J. W. , Moore K. J.
Published: July 2010

Nitrogen removal by cool‐season grasses may aid in capturing excess N from animal confinement operations or phytoremediation. Limited information exists on the N dynamics of these grasses near the asymptote of the N response curve. The objectives of this study were to evaluate N removal, residual soil NO3–N, and apparent N recovery in orchardgrass (Dactylis glomerata L.) and smooth bromegrass (Bromus inermis Leyss.) at annual N rates of 224, 448, and 672 kg ha−1 Species × harvest interactions were observed in both years, but no species × N rate interactions occurred. Orchardgrass removed 352 and 505 kg N ha−1 yr−1 at the 448 N rate compared with 207 and 371 in smooth bromegrass in 1999 and 2000, respectively. In a dry year, orchardgrass (r2 = 0.41) and smooth bromegrass (r2 = 0.31) exhibited linear N uptake. In a year with adequate rainfall, a quadratic relationship was observed for orchardgrass (R2 = 0.92), while smooth bromegrass had linear uptake (r2 = 0.66). Greater N removal was observed in orchardgrass partly because of superior fall growth, when 99 and 82 kg N ha−1 were removed in 1999 and 2000 at the 448 N rate compared with 23 and 15 kg N ha−1 in smooth bromegrass. These removal rates accounted for 28 and 16% of the seasonal total in 1999 and 2000 in orchardgrass and 11 and 4% in smooth bromegrass. Orchardgrass N removal exceeded smooth bromegrass in a three‐cut system, and this difference was enhanced by utilizing the fall growth period to capture residual soil N.
Root Physiology of Less Fall Dormant, Winter Hardy Alfalfa Selections
Authors: Haagenson D. M. , Cunningham S. M. , Volenec J. J.
Published: July 2010

The physiological mechanisms causing fall dormancy (FD)‐induced differences in alfalfa (Medicago sativa L.) shoot growth in autumn and winter hardiness are not understood. The objective of this research was to examine root physiology of experimental germplasms selected for decreased FD that also were selected simultaneously for high winter hardiness. Dormant and semi‐dormant cultivars and germplasms had high root sugar concentrations that were positively associated with winter hardiness. Root amino N and protein levels in December were greater for germplasms selected for decreased FD and increased winter hardiness than for cultivars with comparable levels of winter hardiness. Among the five most fall dormant cultivars Vernal incurred the greatest amount of winter injury and it had lower root amino‐N concentrations when compared with three of the other four dormant cultivars and germplasms. Germplasm 98‐132 with an intermediate FD, incurred relatively low winter injury, similar to that of fall dormant Vernal, when compared with other intermediate dormancy cultivars and germplasms. This germplasm had root sugar concentrations that were similar to plants with FD ratings of 1 to 3. Creation of even less FD germplasms that possess high winter hardiness would facilitate our understanding of the physiological and molecular mechanisms controlling these two very important agronomic traits of alfalfa.