bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Resources and Food Security
Authors: Ringler Claudia , Zhu Tingju
Published: July 2014

Agricultural water use includes a continuum from purely rainfed to fully irrigated systems. Growing pressures on limited water supplies from domestic, industrial, and environmental uses will likely lead to a decline in water availability for food production. Similarly, income growth and urbanization lead to dietary shifts that require more water resources per calorie consumed, putting further pressures on water supplies. As a result, semiarid and arid countries continue to increase net imports of food. Crop water use for sugarcane (Saccharum officinarum L.), maize (Zea mays L.), soybean [Glycine max (L.) Merr.], and fruits are expected to grow over time, whereas water use for wheat (Triticum aestivum L.) and rice (Oryza sativa L.) are expected to decline after 2030. These projections include substantial improvements in water use efficiency at the field, farm, and river basin scale over the coming decades in response to growing water scarcity. If these efficiency improvements are not achieved, future crop water demands would be even larger. Although water resources are a key limiting factor for future food security, policy and investment options to reduce agricultural water use exist on both the water supply and demand side; but political will and ingenuity are needed for their implementation.
Rps8, A New Locus in Soybean for Resistance to Phytophthora sojae
Authors: Burnham K. D. , Dorrance A. E. , Francis D. M. , Fioritto R. J. , St. Martin S. K.
Published: July 2014

Phytophthora root and stem rot caused by Phytophthora sojae M.J. Kaufmann & J.W. Gerdemann (=Phytophthora megasperma Drechs. f. sp. glycinea T. Kuan & D.C. Erwin) is the second leading cause of yield loss in soybean [Glycine max (L.) Merr.] in the USA. Currently, seven loci for resistance with 13 alleles have been identified in soybean. Populations of P. sojae exist in many soybean production regions that cause disease on plants with many, if not all, of these genes. Consequently, the need for new resistance loci is great. A number of plant introductions (PIs) from South Korea were identified in an earlier study that may contain novel resistance loci. The objectives of this project were to identify the allele(s) for resistance to P. sojae present in PI399073 and to map these allele(s) to a linkage group. PI399073 was crossed with ‘Williams’ and ‘S 19‐90’ to develop populations. These populations were assayed for disease resistance, single sequence repeats (SSR), restriction fragment length polymorphisms (RFLP), and isozyme markers. A new Phytophthora resistance locus, Rps8, was mapped to MLG (major linkage group) A2 in two different crosses with PI399073. This is the first locus for Phytophthora resistance that has been identified on MLG A2.
Inheritance of Increased Oleic Acid Concentration in High‐Erucic Acid Ethiopian Mustard
Authors: Velasco Leonardo , Fernández‐Martínez José M. , De Haro Antonio
Published: July 2014

In comparison with canola oil, zero‐erucic acid Ethiopian mustard (Brassica carinata A. Braun) oil is characterized by a low concentration of the monounsaturated oleic acid and high concentrations of the polyunsaturated linoleic acid and linolenic acid. Because of the low oxidative stability of oils rich in polyunsaturated fatty acids, the increase of oleic acid concentration in zero‐erucic acid Ethiopian mustard is needed. Increased oleic acid concentration is currently available only in high erucic acid backgrounds. The objective of the present research was to study the inheritance of increased oleic acid concentration in the high‐erucic acid Ethiopian mustard mutant N2‐3591. The mutant was reciprocally crossed with the high‐erucic acid line C‐101, with the standard composition of C18 fatty acids. Partial maternal and cytoplasmic effects for oleic acid concentration were observed in the analysis of F1 seeds and F1 plants, respectively, from reciprocal crosses. Standard oleic acid concentration in C‐101 was partially dominant over increased oleic acid concentration in N2‐3591. Oleic acid concentration of F2 seeds segregated following a 3:1 (standard–intermediate: increased) ratio, suggesting monogenic inheritance. This was confirmed in the BC1 to N2‐3591, which segregated following a 1:1 (intermediate: increased) ratio. The separation of the standard and intermediate oleic acid classes was not possible, probably because of the partial dominance of standard over increased oleic acid concentration. The monogenic inheritance of increased oleic acid levels in the high‐erucic acid N2‐3591 line will facilitate the transfer of this trait to zero‐erucic acid Ethiopian mustard germplasm.
Genetic Analysis of Seed‐Oil Concentration across Generations and Environments in Sunflower
Authors: Leon A. J. , Andrade F. H. , Lee M.
Published: July 2014

Seed‐oil concentration is a major consideration in sunflower (Helianthus annuus L.) breeding because it is an important component of oil yield. Seed‐oil concentration is a complex trait determined by the genotype and the environmental conditions. The objectives of this study were (i) to locate quantitative trait loci (QTL) for seed‐oil concentration across generations and environments, (ii) to compare QTL detected among individual F2 plants and their F3–generation progeny, and (iii) to assess the genetic relationship between seed‐oil concentration and days to flowering in an elite sunflower population. Two hundred thirty‐five F2 plants and F3 lines of a single‐cross population of two divergent inbred lines were evaluated in four environments. Detection of QTL was facilitated with a genetic map of 205 loci defined by restriction fragment length polymorphism (RFLP) and composite interval mapping. Eight QTL on seven linkage groups accounted for 88% of the genetic variation for seed‐oil concentration across environments. Gene action was additive for four QTL and dominant or overdominant at the others. In all environments, the QTL on linkage group G20cM had the most influence on seed‐oil concentration. Four of the eight QTL were detected in two or more environments and the parental effects were the same across generations and environments. The phenotypic correlation between seed‐oil concentration and days to flower (DTF) ranged from −0.05 to –0.29. QTL on two linkage groups (B and L) affected seed‐oil concentration and DTF. The highest LOD score for these two QTL associated with seed‐oil concentration was observed at the environment with the highest rate of decline of temperature and radiation during the grain‐filling period. Additive effects for higher values of DTF and lower values of seed‐oil concentration in linkage groups B and L were derived from the same parent.
Intercepted Solar Radiation during Seed Filling Determines Sunflower Weight per Seed and Oil Concentration
Authors: Aguirrezábal Luis A. N. , Lavaud Yorick , Dosio Guillermo A. A. , Izquierdo Natalia G. , Andrade Fernando H. , González Leila M.
Published: July 2014

A reduction in intercepted photosynthetically active radiation (PAR) during a short period of seed filling could affect weight per seed and oil concentration in sunflower (Helianthus annuus L.) depending when the reduction occurs. The main objectives of this work were (i) to determine the period of time during which intercepted PAR most influences final weight per seed and oil concentration, and (ii) to establish and validate relationships between intercepted PAR during such a period and oil yield components. Intercepted PAR was modified by shading (0, 50, or 80%) field grown crops during different periods of seed filling. Data from published and unpublished field experiments, in which intercepted PAR per plant was changed during the entire seed filling period by shading, thinning to reduce plant population, or both, were also used. All experiments were performed under adequate water and nutrient conditions. A reduction in intercepted PAR during 7 to 10 d of seed filling affected weight per seed and oil concentration. The developmental interval during which final weight per seed and oil concentration were best accounted for by accumulated intercepted PAR (r2 > 0.805) began at 250°C d and ended at 450°C days after flowering (DAF). The established relationships were validated with independent data. The relationships obtained in this work help to explain the effects of environment and crop management (sowing date, location, year) on oil yield variation.
Genotypic Variation for Glycinebetaine in Sorghum
Authors: Yang Wen‐Ju , Rich Patrick J. , Axtell John D. , Wood Karl V. , Bonham Connie C. , Ejeta Gebisa , Mickelbart Michael V. , Rhodes David
Published: July 2014

Glycinebetaine (GB) accumulation has been suggested to be an adaptive response to several abiotic environmental stresses. Genetic and metabolic studies of GB accumulation in maize (Zea mays L.) indicate that recessive alleles of a single locus are responsible for the phenotype of GB nonaccumulation. The present study was undertaken to determine whether a similar genetically determined range of GB levels exists in the related C4 species Sorghum bicolor (L.) Moench. In a preliminary analysis of 240 sorghum genotypes, sampled at the postflowering stage, total quaternary ammonium compound (QAC) levels in the betaine fraction of the flag leaves were found to range from as low as 0.1 μmol g−1 FW to as much as 33 μmol g−1 FW. Stable isotope dilution desorption chemical ionization mass spectrometry of six genotypes with high QAC levels and five genotypes with low QAC levels confirmed that this variation could be attributed almost exclusively to genetic variability for GB level. GB‐nonaccumulating sorghum genotypes were confirmed to be GB‐non‐accumulating in a second year of field‐testing, and in greenhouse studies under salinized and non‐salinized conditions. GB levels increased with seedling age and/or salinization in GB‐accumulating genotypes. Also, GB levels were highest in the youngest leaves of GB‐accumulating sorghum genotypes. This work shows that GB is the major QAC in sorghum, that genetic differences in GB accumulation exist in sorghum as they do in maize, and that the level of GB in GB‐accumulating lines is developmentally and environmentally regulated. A list of GB levels of publicly available lines of sorghum is also provided.
Environmental Factors Determining Carbon Isotope Discrimination and Yield in Durum Wheat under Mediterranean Conditions
Authors: Araus J. L. , Villegas D. , Aparicio N. , del Moral L. F. García , El Hani S. , Rharrabti Y. , Ferrio J. P. , Royo C.
Published: July 2014

The effect of environment on the relationship between grain carbon isotope discrimination (Δ) and yield was studied for durum wheat (Triticum turgidum L. var. durum) under Mediterranean conditions. A group of 25 genotypes was grown under contrasting water regimes in two regions of Spain during three years. The first objective was to determine the environmental factors responsible for the strong positive relationship previously observed between Δ and yield across trials. Environmental factors tested were total water input (Wi), mean temperature, accumulated reference evapotranspiration (ET0), and the ratio Wi/ET0 during different periods of the crop cycle. Water input during grain filling was the variable most strongly correlated with grain Δ and yield across all the trials, as well as across the subset of trials in northeastern Spain. In southeastern Spain, the most drought prone of the two regions, Wi from sowing to heading explained the most variation in grain Δ and yield. The second objective was to study the effect of environment on the relationship between Δ and yield across genotypes. No significant correlation was found for trials with a mean yield up to about 2000 kg ha−1, but the strength of the relationship increased sharply and attained significance in trials yielding 2500 kg ha−1 When yield above 2500 kg ha−1 the correlation between Δ and yield remained relatively steady and positive, with an r value around 0.5. It is concluded that breeding to raise durum wheat yield in Mediterranean conditions could take advantage of selecting for higher Δ only in relatively wet years or under supplementary irrigation.
Tillage and Seeding Rate Effects on Wheat Cultivars: I. Grain Production
Authors: Carr Patrick M. , Horsley Richard D. , Poland Woodrow W.
Published: July 2014

Tillage is declining in wheat production systems in the Great Plains. Our objective was to determine if a tillage × cultivar interaction occurred for grain yield, protein concentration, kernel weight, and test weight for hard red spring wheat (Triticum aestivum L. emend. Thell.) in a wheat–fallow monoculture. We also wanted to know if seeding rate × cultivar and tillage × seeding rate × cultivar interactions occurred for these grain traits. The cultivars AC Minto, Amidon, Bergen, Grandin, and Norm were seeded at 123, 247, and 371 live kernels m−2 in conventional‐till (CONT), reduced‐till (RT), and no‐till (NT) systems in a randomized complete block with a split split‐plot arrangement in southwestern North Dakota during 1995–1998. Tillage × cultivar, seeding rate × cultivar, and tillage × seeding rate × cultivar interactions did not occur for any grain trait (P > 0.05). Grain yield, protein concentration, kernel weight, and test weight were unaffected by tillage system. A positive quadratic response in grain yield occurred as the seeding rate was increased. Grain test weight increased from 577 to 586 g m−3 as the seeding rate increased from 123 to 371 kernels m−2, but grain protein concentration and kernel weight were unaffected. Grain yield ranged from 2473 to 3063 kg ha−1, crude protein from 141 to 154 g kg−1, kernel weight from 30 to 32 g (1000 kernels)−1, and test weight from 572 to 590 g m−3 among the five cultivars. Results of this study suggest that cultivar recommendations under CONT can be extended to RT and NT systems in a wheat‐fallow monoculture.
Genotype × Environment Interaction for Grain Color in Hard White Spring Wheat
Authors: Matus‐Cádiz M. A. , Hucl P. , Perron C. E. , Tyler R. T.
Published: July 2014

Improvement of grain color in hard white spring wheat (Triticum aestivum L.) breeding programs depends on understanding the influences of genotype (G), environment (E), and their interaction (G × E). The objectives of this study were to quantify genetic variability for grain color and assess the nature of the G × E interaction in determining grain color in 79 spring wheat genotypes. Twelve check cultivars [seven hard red (HR), four hard white (HW), and one soft white (SW)] and 67 white‐seeded Australian (AUS) accessions were grown at two locations across 2 yr. Wheat genotypes differed significantly in agronomic traits, grain protein, and kernel hardness. Grain and meal color were quantified using Hunterlab colorimeter values. Whole grain color values without (L = 40.9–50.4 units; a = 7.0–8.3; b = 13.6–19.1) and with NaOH treatment (L = 22.7–38.1; a = 7.7–9.7; b = 9.2–17.9) varied among genotypes. Using ground meal, color values (L = 80.1–84.9; a = 1.8–2.6; b = 8.9–11.8), yellow pigment content (2.5–4.8 μg g−1), and lutein content (1.8–3.7 μg g−1) varied among genotypes. Genotype × location (L) interactions were not significant for colorimetric and pigmentation variables. The Azallini and Cox test detected one crossover G × year (Y) interaction for grain a‐value (without NaOH), one for grain b‐value (without NaOH), and 12 for lutein content. Genetic variation exists for grain color among HW genotypes. The noncrossover nature of G × E interactions for grain color indicates that white‐seeded genotypes selected as superior in one environment will be superior in other environments.
Plant Growth Regulator and Daylength Effects on Preanthesis Main Shoot and Tiller Growth in Conventional and Dwarf Oat
Authors: Peltonen‐Sainio Pirjo , Rajala Ari , Simmons Steve , Caspers Roger , Stuthman Deon D.
Published: July 2014

Plant growth regulators (PGRs) alter tiller growth in cereals. This response may be dependent on daylength (DL). Standard height (HE) and dwarf oat cultivars were grown at 14‐ and 18‐h DLs. Foliage was sprayed with chlormequat chloride (CCC) and ethephon at early growth stages to evaluate PGR effects on the growth of the main shoot and tillers. Two successive experiments with 10 replicates were arranged in two growth chambers (14‐h and 18‐h DL) at the University of Minnesota. Preanthesis main shoot and tiller HEs and dry weights (DWs) were measured. In Exp. 1, the numbers of leaves and green leaves were counted. Relative growth rate (RGR), relative elongation rate (RER), and shoot DW:HE ratio were measured. Plant growth regulators retarded growth of the main shoot in conventional oat cultivars without stimulating growth of T1 and T2 tillers. Response of the dwarf cultivar to PGRs was modest. Only ethephon enhanced T1 tiller growth at 18‐h DL. However, PGR‐treated plants had up to five more green leaves per plant at preanthesis due to stimulated leaf emergence on T3 and T4 tillers especially at the 18‐h DL. In Exp. 1, PGR treatments reduced the DW to HE ratio, that is, shortened rather than strengthened the stem. In Exp. 2, measurements were made more frequently and ethephon first increased this ratio followed by a decrease. Thus, even though long‐day conditions somewhat enhanced DW accumulation and stem elongation, few marked differences in oat response to PGR treatments were noted when comparing short‐ and long‐day conditions.
Identification of Soybean Cultivars That Yield Well at Low Plant Populations
Authors: Rigsby Brian , Board James E.
Published: July 2014

Little information is known concerning cultivar differences for optimal plant population (minimal plant population for best yield) in soybean [Glycine max (L.) Merr.]. Development of cultivars or genotypes having low optimal plant population would reduce seeding costs, avoid some diseases, and minimize lodging. The objectives of this study were to determine cultivar variability for optimal plant population, determine quantitative relationships between yield and other parameters as affected by plant population–cultivar treatment combinations, and to develop a regression model for identifying cultivars that have low optimal populations. The study was planted near Baton Rouge, LA (30° N Lat) on a commerce silt loam soil (fine‐silty, mixed, nonacid, thermic, Aeric, Fluvaquent) in a randomized complete block experimental design in a split plot arrangement with four replications and two years (1997 and 1998). Main plots were14 cultivars and split plots were low (95 000 plants ha−1) and normal (250 000 plants ha−1) plant populations. Cultivars that optimized yield at low plant population were ‘NKRA452’ and ‘A6911’. Yields were optimized for cultivar–plant population treatment combinations achieving a total vegetative dry matter at R5 of 500 g m−2 or greater. Partitioning of dry matter into branches was the most important parameter accounting for cultivar yield differences within low plant populations (r2 = 0.56), and with the addition of a few other parameters a regression model was developed (r2 = 0.83) that could rapidly and easily identify cultivars with low optimal plant population. In conclusion, genotypic differences in low optimal plant population exist and are influenced by dry matter partitioning into branches.
Seasonal Changes in Carbohydrate Accumulation for Two Creeping Bentgrass Cultivars
Authors: Xu Qingzhang , Huang Bingru
Published: July 2014

Controlled‐environment studies suggest that turf quality decline of creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.] under heat stress is associated with decreases in carbohydrate availability in plants. The study was designed to examine and compare seasonal changes of carbohydrate status and C allocation pattern for two creeping bentgrass cultivars, ‘Penncross’ and ‘L‐93’, that differ in heat tolerance under field conditions. The experiment was conducted from May to November in 1999 and 2000. Grasses were managed under putting green conditions with daily irrigation and mowing at a 4‐mm height. Turf quality of both cultivars declined from May and reached the lowest level in August and September, and recovered in October. The content of total nonstructural carbohydrates (TNC), sucrose, and fructans in shoots and roots exhibited a similar seasonal pattern as turf quality for both cultivars in both years. Reducing sugar content decreased during the summer, but did not recover in October, except in shoots of L‐93 in 2000. The decreases in carbohydrate content were more pronounced in roots than in shoots for both cultivars. Carbon allocation to roots also decreased during summer for Penncross. Cultivar differences in carbohydrate content were not consistent between fractions of carbohydrate and times of the year. The decline in carbohydrate availability, particularly in roots, and limited C allocation to roots during summer could contribute to quality decline under field conditions; however, cultivar variation in carbohydrate content was not related to the differences in turf quality decline between two cultivars.
Effect of Irrigation Frequency on Turf Quality, Shoot Density, and Root Length Density of Five Bentgrass Cultivars
Authors: Jordan J. E. , White R. H. , Vietor D. M. , Hale T. C. , Thomas J. C. , Engelke M. C.
Published: July 2014

The culture of creeping bentgrass (Agrostis palustris Huds.) at low mowing heights on putting greens in the hot humid region of the USA presents numerous water management problems. Frequent irrigation of greens to prevent water stress has been credited with producing shallow rooted turf with reduced tolerance to environmental stress. The present study was conducted to determine the relationship between irrigation frequency and turf quality, shoot density, and root length density for five cultivars of creeping bentgrass grown on a sand‐based root zone and maintained to putting green standards. A total of 81 plots, 1.5 by 1.5 m each, were established on a USGA‐type root zone mixture and organized into nine irrigation cells of nine plots each. Each irrigation cell could be irrigated individually. One plot in each irrigation cell was planted to the following bentgrass cultivars: A‐4, Crenshaw, Mariner, L‐93, and Penncross. The remaining four plots in each irrigation cell were also planted with bentgrass but were not a part of this study. Irrigation frequency treatments of 1‐, 2‐, and 4‐d were imposed on three irrigation cells each. After establishment, measurements of turf quality, shoot density and root length density were made over a 2‐yr period. In both years, Crenshaw and L‐93 had the best turf quality. At the end of the study, shoot densities for Crenshaw, L‐93, and A‐4 were 37 to 42% greater than Mariner and Penncross. Because of frequent rainfall events in 1997, there were no significant (P ≤ 0.05) effects of irrigation frequency on shoot density or root length density. However, in 1998, turf was more dependent on irrigation and bentgrass irrigated every 4 d had significantly greater turf quality, shoot density, and root length density than that watered every 1 or 2 d. The data show that even under putting green management conditions, reduced irrigation frequency of bentgrass produces a larger and deeper root system resulting in greater overall plant health, turf quality, and shoot density.
Identification and Validation of Markers Linked to Broad‐Spectrum Stem Rust Resistance Gene Sr2 in Wheat (Triticum aestivum L.)
Authors: Spielmeyer W. , Sharp P. J. , Lagudah E. S.
Published: July 2014

Stem rust resistance in wheat (Triticum aestivum L.) conferred by the Sr2 gene has remained effective against Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn. worldwide for more than 50 yr. Sr2 resistance is associated with variable levels of disease symptoms; it shows recessive inheritance and is expressed primarily during the adult‐plant stage. A genetic and physical interval for the Sr2 gene was determined on the short arm of chromosome 3B of wheat. Flanking microsatellite markers were identified and one tightly linked marker (gwm533) was shown to be associated with presence of Sr2 This marker was validated in a wide range of germplasm and can now be implemented in marker‐assisted breeding to facilitate selection for this durable, broad‐spectrum but difficult to score rust resistance gene.
Spatiotemporal Genetic Structure within White Clover Populations in Grazed Swards
Authors: Gustine David L. , Elwinger Gerald F.
Published: July 2014

White clover (Trifolium repens L.) populations exhibit high genetic and clonal diversity, but often exist for many decades in grazed swards at northern midlatitudes. This study was conducted to determine whether genetic structure exists within rapidly changing populations and is a factor in creating genetic diversity. Trifoliate leaf samples were taken monthly in 1997 and 1998 from up to 37 specific points in four 1.2‐ by 1.2‐m quadrats from May to September on two central Pennsylvania farm sites. Random amplified polymorphic DNA (RAPD) profiles of population samples from 67 quadrats were tested by spatial autocorrelation analysis based on a multivariate nonparametric approach. Significant (P < 0.05) overall spatial autocorrelation was found in 26 populations that had clones and in seven populations without clones, while nonsignificant autocorrelation was found in 27 and seven populations with and without clones, respectively. Frequencies of significant autocorrelation for populations on one site in 1997 and 1998 were 0.5 and 0.2, respectively, and the frequencies for the other site were 0.8 and 0.4, respectively. The ratio of populations lacking significant autocorrelation to those with significant autocorrelation changed little from zero to six clones, but increased dramatically for seven or eight clones. The estimated patch size (overall mean 66 cm; SE = 8) for two years and two sites did not change significantly over the growing season. Number of clones and patch size was less important in determining genetic structure than variable existence of spatial autocorrelation.
Mapping QTL for Bacterial Brown Spot Resistance under Natural Infection in Field and Seedling Stem Inoculation in Growth Chamber in Common Bean
Authors: Jung G. , Ariyarathne H. M. , Coyne D. P. , Nienhuis J.
Published: July 2014

Bacterial brown spot (BBS), caused by Pseudomonas syringae pv. syringae van Hall (Pss), is an important bacterial disease of common bean (Phaseolus vulgaris L.). The objective of this study was to identify random amplified polymorphic DNA (RAPD) molecular markers linked to quantitative trait loci (QTLs) for BBS resistance. Resistance was assessed by three methods: (i) stem inoculations of plants grown in a greenhouse evaluated by a 1‐to‐5 rating scale for stem symptoms, (ii) percentage of BBS infected leaves per plot in noninoculated field trials, and (iii) Pss population sizes, on noninoculated field grown plants determined by a leaflet freezing assay (LFA). F8:9 recombinant inbred lines derived from the Mesoamerican cross of Belneb RR‐1 (susceptible to BBS) × A 55 (resistant to BBS) were grown in replicated experiments in two years (1996, 1998) in Wisconsin. In addition, two separate experiments were performed in the greenhouse in a randomized complete block design with two replicates for seedling stem inoculation with Pss strain Bs191. One genomic region on linkage group (LG) 2, from a previously published genetic linkage map, was significantly associated with QTLs for BBS resistance measured by three assays over two years. Phenotypic reactions were significantly correlated with the measurement of freezing temperatures as determined by LFA under a favorable environment for the growth of epiphytic bacterial populations. Marker assisted selection for resistance to BBS using molecular markers found during this study may improve selection efficiency for resistance because of the low heritability of the reaction to BBS, and the independent QTLs for resistance to different bacterial diseases. Furthermore, disease screening solely dependent upon natural field inoculations is not reliable because of genotype × environment interactions. The leaflet freezing assay method could be utilized to screen progenies or breeding germplasms, even when no distinct phenotypic disease symptoms are present on the plants.
Towards a Saturated Molecular Genetic Linkage Map for Cultivated Sunflower
Authors: Yu Ju‐Kyung , Tang Shunxue , Slabaugh Mary B. , Heesacker Adam , Cole Glenn , Herring Martin , Soper John , Han Feng , Chu Wen‐Chy , Webb David M. , Thompson Lucy , Edwards Keith J. , Berry Simon , Leon Alberto J. , Grondona Martin , Olungu Christine , Maes Nele , Knapp Steven J.
Published: July 2014

The density and utility of the molecular genetic linkage map of cultivated sunflower (Helianthus annuus L.) has been greatly increased by the development and mapping of several hundred simple sequence repeat (SSR) markers. Of 1089 public SSR markers described thus far, 408 have been mapped in a recombinant inbred line (RIL) mapping population (RHA280 × RHA801). The goal of the present research was to increase the density of the sunflower map by constructing a new RIL map (PHA × PHB) based on SSRs, adding loci for newly developed SSR markers to the RHA280 × RHA801 RIL map, and integrating the restriction fragment length polymorphism (RFLP) and SSR maps of sunflower. The latter was accomplished by adding 120 SSR marker loci to a backbone of 80 RFLP marker loci on the HA370 × HA372 F2 map. The map spanned 1275.4 centimorgans (cM) and had a mean density of 6.3 cM per locus. The PHA × PHB SSR map was constructed from 264 SSR marker loci, spanned 1199.4 cM, and had a mean density of 4.5 cM per locus. The RHA280 × RHA801 map was constructed by adding 118 new SSR and insertion–deletion (INDEL) marker loci to 459 previously mapped SSR marker loci. The 577‐locus map spanned 1423.0 cM and had a mean density of 2.5 cM per locus. The three maps were constructed from 1044 DNA marker loci (701 unique SSR and 89 unique RFLP or INDEL marker loci) and supply a dense genome‐wide framework of sequence‐based DNA markers for molecular breeding and genomics research in sunflower.
Inheritance and Expression of the Naked‐Grained and Fatuoid Characters in Oat
Authors: Hoekstra G. J. , Burrows V. D. , Mather D. E.
Published: July 2014

In both hulled and naked oat (Avena sativa L.), aberrant “fatuoid” plants can occur; these can be recognized by their prominent twisted and geniculate lemma awns. Fatuoids of hulled oat cannot be used as cultivars because their grain shatters from the plant. In contrast, fatuoids of naked oat do not shatter and can be used as cultivars. In naked oat, occasional hulled grains may occur, detracting from grain quality and consistency. Some fatuoid lines of naked oat have been observed to produce few hulled grains. Here, we used crosses involving two fatuoid naked oat lines and three nonfatuoid oat cultivars (one hulled and two naked) to study the inheritance of the naked‐grained and fatuoid characters. Phenotypic ratios observed in the F2 generation were not consistent with codominant single‐gene models for either character. Dominant single‐gene models in which the hulled and fatuoid alleles are recessive, and for which the expression of the dominant gene is variable, were satisfactory in some, but not all, crosses. Within F2 populations, true‐breeding fatuoids could be quite reliably selected on the basis of the presence of two or more geniculate lemma awns per spikelet, while true‐breeding nonfatuoids could be quite reliably selected on the basis of the absence of geniculate lemma awns. In naked oat, fatuoid plants tended to produce fewer hulled grains than nonfatuoid plants, suggesting that the fatuoid condition may enhance the expression of the naked‐grained character. Despite the lack of a complete understanding of the genetic control of the naked‐grained and fatuoid characters, it should be possible and useful to develop fatuoid naked oat lines for use as cultivars.
Selection for Stem Rust Resistance in Tall Fescue and Its Correlated Response with Seed Yield
Authors: Barker R. E. , Pfender W. F. , Welty R. E.
Published: July 2014

Genetic resistance to stem rust (caused by Puccinia graminis Pers.:Pers. subsp. graminicola Z. Urban) could reduce the need for fungicides to control the disease in tall fescue [Lolium arundinaceum (Schreb.) Darbysh. (=Festuca arundinacea subsp. arundinacea)] grown for seed. Two populations from 14 resistant forage‐type plants (F) and 20 turf‐types (T) were developed using polycross (PX) and open pollination (OP) progenies. A two‐stage controlled environment inoculation was used for screening and selection for two cycles. Direct selection response was determined after two artificial inoculations in a controlled environment. Indirect selection response for seed yield was measured, using the same plants as the direct selection study, in the field using natural inoculation for 4 yr. Plants with resistant reaction, based on pustule type, increased from 5 to 54% in the F population and from 6 to 50% in the T after two cycles of PX selection and from 5 to 63%, and from 6 to 50% in the F and T populations, respectively, after one cycle of OP followed by one cycle of PX selection. In each selection scheme, the largest increase came from the first PX cycle. Seed yield of tall fescue with improved stem rust resistance was higher than for susceptible populations or cultivars with heavy stem rust presence (1998), but yields were similar with no rust pressure (1999). These results indicate that seed yields in tall fescue can be maintained using genetic resistance to stem rust sufficient to slow or eliminate disease epidemic development.
Background of U.S. Hybrid Corn II
Authors: Troyer A. Forrest
Published: July 2014

Understanding the history of a crop helps plant breeders select. This paper supplements and corrects Background of U.S. Hybrid Corn (Zea mays L., Crop Sci. 39:601–626). I explain which open‐pollinated cultivars and landmark inbreds persisted into today's hybrids and attempt to explain how and why. I briefly discuss human (artificial) selection, natural selection, and food production. Pedigree background frequencies from 33 elite, 1990s era inbreds directly estimate about 40% of U.S. hybrid corn hectarage and indirectly estimate the rest. I've searched historical records to trace the succession of cultivars and inbreds. Reid Yellow Dent is 51% of the documented U.S. hybrid corn background (Iodent Reid, 13%; Troyer Reid, 12%; Osterland Reid, 11%; Stiff Stalk Synthetic, 8%; Reid per se, 4%; and Funk Reid, 3%). Minnesota 13 is 13%, Lancaster Sure Crop is 13%, Northwestern Dent is 5%, and Leaming Corn is 5%. Five widely adapted, century‐old, open‐pollinated cultivars surpassed in use tens of thousands of genetically divergent cultivars to account for 87% of the known background of today's U.S. hybrid corn. Adaptedness mattered; U.S. corn breeders are adapting a tropical crop to a temperate climate. New, diverse background sources will probably be better adapted to longer daylengths, cooler minimum temperatures, drought, shorter seasons, and improved crop production practices. Selecting for adaptation to these conditions and to improved agronomic production practices will continue to increase yield. Traditional corn breeding methods will continue to accommodate climate change. Plant breeding and crop production research provides plentiful food in the USA.
SSR and Pedigree Analyses of Genetic Diversity among CIMMYT Wheat Lines Targeted to Different Megaenvironments
Authors: Dreisigacker S. , Zhang P. , Warburton M. L. , Van Ginkel M. , Hoisington D. , Bohn M. , Melchinger A. E.
Published: July 2014

Improved bread wheat (Triticum aestivum L.) cultivars for diverse agroecological environments are important for success in the effort to increase food production. In the 1980s, CIMMYT introduced the megaenvironment (ME) concept to breed wheats specifically adapted to different areas. Our objective was to analyze the genetic diversity among 68 advanced CIMMYT wheat lines targeted to different MEs by using 99 simple sequence repeats (SSRs) and the coefficient of parentage (COP). The average number of alleles detected was higher for the 47 genomic SSRs (5.4) than for the 52 SSRs derived from expressed sequence tags (EST) (3.3), but gene diversity between MEs was similar for both types of markers. No significant differences among the five MEs were observed for the means of SSR‐based genetic similarities (GS), calculated as 1 − Rogers' distance, and COP values. Both measures showed a low correlation (r = 0.43). High levels of genetic diversity were found within the germplasm targeted to each ME. However, principle coordinate analysis based on modified Rogers' distances did not separate the genotypes according to their targeted MEs. We conclude that presence of a single core germplasm can reflect large phenotypic differences. A sufficient number of diverse breeding lines for each ME is required because MEs generally combine various production areas. SSRs represent a powerful tool to quantify genetic diversity in wheat, but genotypic differentiation for adaptation to specific MEs in the CIMMYT program could not be proven.
Inheritance and QTL Mapping of Antibiosis to Green Leafhopper in Rice
Authors: Wang Chunming , Yasui Hideshi , Yoshimura Atsushi , Zhai Huqu , Wan Jianmin
Published: July 2014

Nephotettix virescens Distant (green leafhopper: GLH) is one of the major insect pests of rice (Oryza sativa L.) in the temperate rice growing region of Asia. The objective of this study was to determine the chromosome locations of some GLH‐resistance genes and conduct genetic analysis of GLH resistance. From a cross between the japonica cultivar Taichung65, which is susceptible to GLH, and indica cultivar ARC10313, which is resistant to GLH, 125 recombinant inbred F10 lines (RIL) were developed. Quantitative trait loci (QTLs) for antibiosis to GLH were detected on chromosomes 3, 5, 11, and 12. The QTL near XNpb292 on chromosome 12 for GLH mortality was from the japonica cultivar, while the other three QTLs on chromosomes 3, 5, and 11 were from the indica cultivar. The percentages of observed phenotypic variance attributable to the major QTLs on chromosomes 3 and 11 were 25.3% and 56.8%, respectively. These two QTLs were close to two green rice leafhopper (GRH, Nephotettix cincticeps Unler) resistance genes, Grh4 and Grh2, respectively. Using NILs (near isogenic lines) of Grh4 and Grh2, we determined that the interaction of these two GRH resistance genes expressed strong resistance to GLH. Four GLH‐resistance QTLs, including two major QTLs linked to XNpb144 on chromosome 3 and G1465 on 11, respectively, were identified in this study, and these two major QTLs were located close to Grh2 and Grh4 It may be possible to pyramid these genes to improve resistance to both GRH and GLH.
Dinitrogen Fixation in Illinois Bundleflower
Authors: Byun Jaehyun , Sheaffer Craig C. , Russelle Michael P. , Ehlke Nancy J. , Wyse Donald L. , Graham Peter H.
Published: July 2014

Symbiotic N2 fixation capacity may affect productivity of the perennial legume Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald]. Our objective was to estimate N2 fixation of three Illinois bundleflower accessions managed for forage. Herbage yield ranged from 1.02 Mg ha−1 to 3.69 Mg ha−1 in Year 1, and 2.99 Mg ha−1 to 8.27 Mg ha−1 in Year 2. Accessions differed in herbage yield, aboveground N yield, and N2 fixed at certain locations in Year 1, but not in Year 2. Percentage of N derived from the atmosphere (%Ndfa) varied with location but not with accession in either year. The 15N natural abundance method gave lower estimates of %Ndfa than the 15N enrichment method. In yr 1, N2 fixation ranged from 0 to 30 kg ha−1 N (15N natural abundance method), 11 to 43 kg ha−1 (15N enrichment method), and 0 to 50 kg ha−1 N (total N difference method), and in Year 2 these estimates at two locations were 60 to 67 kg ha−1 N, 79 to 127 kg ha−1 N, and 67 to 142 kg ha−1 N, respectively. Differences in N2 fixation among locations could have been due to rhizobial strains. At the high‐yielding location with the greatest N2 fixation, over one‐half of the nodules were occupied by indigenous rhizobial strains, whereas at other locations, strains from commercial inoculant accounted for most nodules. Symbiotic N2 fixation by Illinois bundleflower could be enhanced by new rhizobial inoculums.
Comparison of Uptake and Distribution of Cadmium in Different Cultivars of Bread and Durum Wheat
Authors: Greger Maria , Löfstedt Martina
Published: July 2014

The intent of this study was to investigate whether high levels of cadmium (Cd) in the grains of high Cd‐accumulating cultivars is caused by a high Cd uptake in the roots, a high translocation of Cd from roots to shoot, or a redistribution of Cd between the shoot and the grains. High and low accumulators, with respect to the grain accumulation of Cd, of spring and winter bread wheat (Triticum aestivum L.) and of durum wheat (T. durum Desf.) were selected from field studies. The selected cultivars were grown in nutrient solution containing 0.5 mM Cd in a climate chamber for (i) 19 d and (ii) until maturity. The concentration of Cd in roots, shoot, flag leaves, grains, and grain coats was measured by atomic absorption. The results indicated that there are differences among the cultivars in the ability to accumulate Cd in grains. The biggest differences were found among the durum wheat cultivars. Different Cd accumulation in grains was related to variations in the translocation from root to shoot and to the Cd concentration in shoot, flag leaf, and grain coats, but not to the uptake of Cd by roots.
Soybean Growth and Development in Various Management Systems and Planting Dates
Authors: Pedersen Palle , Lauer Joseph G.
Published: July 2014

Soybean [Glycine max (L.) Merr.] has the ability to produce similar yields across a broad range of management systems and planting dates. Our objective was to better understand growth factors affecting yield component compensation in the upper Midwest under different management systems. An older cultivar, Hardin, and two newer cultivars, DeKalb CX232 and Spansoy 250, were grown in five management systems during four growing seasons from 1997 to 2000. Four of the five management systems were located near Arlington, WI, on a silt loam soil consisting of conventional and no‐tillage systems with and without irrigation. The fifth management system was located near Hancock, WI, on a conventionally tilled, irrigated sandy loam soil. Yield component compensations gave similar grain yield among cultivars, planting dates, and management systems. At R6, CX232 and Spansoy 250 averaged greater dry matter (DM) accumulation, leaf area index (LAI), and crop growth rate (CGR) than Hardin. Early planted soybean had more total DM than the late‐planted soybean. No‐tillage systems produced more total DM, LAI, and CGR after R3 than the two conventional tillage systems at Arlington. Irrigated systems had higher LAI than the nonirrigated systems. These results indicate that the compensatory growth and alterations in plant development among cultivars, management systems, and planting dates had no impact on soybean yield.
Vigor Tests Used to Rank Seed Lot Quality and Predict Field Emergence in Four Forage Species
Authors: Wang Y. R. , Yu L. , Nan Z. B. , Liu Y. L.
Published: July 2014

Laboratory and field tests were conducted in 1999 and 2000 in Gansu Province, China, to investigate the suitability of various laboratory vigor tests, to rank quality of commercial seed lots, and to predict seedling field emergence (FE) of four forage species. Species used included two legumes, purple vetch (Vicia benghalensis L.) and alfalfa (Medicago sativa L.), and two grasses, sudangrass [Sorghum bicolor (L.) Moench subsp. drummondii (Steud.) de Wet ex Davidse] and Siberian wild ryegrass (Elymus sibiricus L.). Results showed that among all tests, the electrical conductivity (EC) test provided the best estimate of seed vigor for the two legume species, both for ranking seed lots quality and predicting FE, but gave the worst indication of seed lot vigor for the two grass species. The EC result was not only poorly related to FE, but also poorly related to the standard germination (SG) of a wide range of seed lots of the two grass species that varied in viability. The controlled deterioration (CD) test generally better indicated seed lot vigor for test species than did SG, except that it lacked sensitivity in ranking seed lot quality of alfalfa and was not significantly related to Siberian wild ryegrass FE. The germination index (GI) better indicated seed lot quality and predicated FE than SG of sudangrass over the 2‐yr results, but not consistently better than SG for other species. Initial count of standard germination (SGi) generally performed more poorly than the other vigor tests. From this study and previous work on forage species, we conclude that EC test for forage legumes and CD tests for both forage legumes and grasses have the potential to be developed as improved vigor tests for ranking seed lot quality and predicting seeding performance.
Breeding Perennial Ryegrass for Resistance to Gray Leaf Spot
Authors: Bonos Stacy A. , Kubik Christine , Clarke Bruce B. , Meyer William A.
Published: July 2014

Gray leaf spot, caused by the fungus Pyricularia grisea (Cooke) Sacc. [teleomorph Magnaporthe grisea (T.T. Herbert) Yaegashi & Udagawa], can be a devastating disease on perennial ryegrass (Lolium perenne L.). The identification and utilization of perennial ryegrass cultivars with improved resistance to gray leaf spot would reduce the need for fungicide applications. The objectives of this study were to: (i) evaluate cultivars, experimental selections, and single‐plot progenies of perennial ryegrass for resistance to gray leaf spot, (ii) develop populations from selected resistant parents to determine improvements in the next generation, and (iii) determine heritability and the response to selection for gray leaf spot resistance in perennial ryegrass populations. Two perennial ryegrass field experiments consisting of commercial cultivars and experimental selections, were established in 2000 and 2001 at Adelphia, NJ. Susceptibility of germplasm to gray leaf spot was evaluated following ephemeral natural outbreaks of the disease that occurred three to four weeks post seeding. Parents with improved resistance to gray leaf spot were selected based on progeny turf plot evaluations in 2000, inter‐pollinated and seeded into turf plots in the 2001 experiment. Most cultivars and selections evaluated in both experiments had greater than 50% gray leaf spot disease. The high broad‐sense heritability estimate (0.92) and similar response of progeny compared to selected parents indicated that parent selection based on progeny tests was a good selection method to predict the combining ability of the parents. It also proved successful in improving gray leaf spot resistance in the next generation, which will be important for the development of more disease resistant cultivars.