bluuebunny/crossref_metadata_2025 huggingface dataset:
Early Flower Bud Loss and Mepiquat Chloride Effects on Cotton Yield Distribution
Authors: Cook Donald R. , Kennedy Charles W.
Published: July 2010

Abscission or abortion of the initial cotton (Gossypium hirsutum L.) flower buds or bolls increases the importance of retaining fruit on adjacent or subsequent fruiting positions. Use of the plant growth regulator mepiquat chloride (MC) (N, N dimethylpiperidinium chloride) improves boll retention on lower reproductive branches (sympodia), reduces vegetative growth, and in some cases reduces upper sympodial productivity. Our objective was to determine the effect of doses and application timings of MC and different levels of early flower bud removal on within‐plant yield distribution. Zero or an average of two or four flower buds located at first positions on lower sympodia were removed from each plant prior to MC applications at two field locations in 1992. This bud loss resulted in higher retention at second positions on lower sympodia and on slightly higher sympodia. Two biweekly doses of 24.5 g ha−1 of MC applied at early bloom also enhanced compensation and yield on lower sympodial second positions. Primarily at one location, four weekly MC doses of 12.25 g ha−1 each beginning when buds were 1 cm long resulted in increased monopodial branch yield when there was moderate early bud loss. Depending on field location, one or the other of the MC treatments reduced the number of fruiting positions and yield on higher sympodia when fruit retention on lower sympodia was high. Loss of early buds, which resulted in small increases in vegetative growth, ameliorated this effect. The biological responses produced by early bud loss and MC treatments interacted positively. After early bud loss, plants treated with MC generally improved compensation on lower sympodia without negative effects on upper sympodia.
High Efficiency Transformation of U.S. Rice Lines from Mature Seed‐Derived Calli and Segregation of Glufosinate Resistance under Field Conditions
Authors: Jiang Junda , Linscombe Steve D. , Wang Jianlin , Oard James H.
Published: July 2010

Gene transfer techniques have been developed previously for certain model rice (Oryza sativa L.) cultivars, but problems persist in U.S. lines for low transformation rates and in vitro callus culture. Moreover, few studies have evaluated traits such as herbicide resistance in transgenic U.S. rice lines under field conditions. A rapid and efficient method was developed for production and field evaluation of transgenic herbicide‐resistant elite U.S. rice lines and cultivars. Six elite U.S. rice lines were transformed for glufosinate herbicide resistance by particle bombardment of mature seed‐derived embryogenic calli; resistance was confered by either the pat or bar gene. By utilizing optimized media for embryogenic callus induction and bialaphos or hygromycin B as a selection agent, an average transformation efficiency of 5% (258 independent events/5201 calli) was obtained across six lines. Southern blot analysis of genomic DNA isolated from primary R0 and R1 progeny plants demonstrated that the pat and hygromycin phosphotransferase (hph) genes were stably integrated into the rice genome. Glufosinate resistance in R0, R1, and R2 progeny was confirmed in the greenhouse and under field conditions. All R1 and a majority (79%) of R2 progeny exhibited one to two gene segregation patterns for glufosinate resistance. The high efficiency and reproducibility of the improved transformation system should make it possible to routinely introduce genes of interest into any elite U.S. rice breeding line.
Wheat Transformation Using Cyanamide as a New Selective Agent
Authors: Weeks J. T. , Koshiyama K. Y. , Maier-Greiner U. , Schäeffner T. , Anderson O. D.
Published: July 2010

There is a general need for additional selectable marker genes for plant transformation. Only a few have been reported in wheat (Triticum aestivum L.) transformation experiments, some of which are under patent restriction or have other disadvantages. A new selectable marker gene was identified which can be used to select resistant callus in tissue culture and regenerate transgenic wheat plants. A gene from the soil fungus Myrothecium verrucaria (Albertini & Schwein.) Ditmar:Fr., coding for the enzyme cyanamide hydratase which converts cyanamide into urea, was previously described. In our wheat transformation experiments, the gene conferred resistance to cyanamide at a tissue culture level and therefore cyanamide could be used to select for transformants. At the whole plant level, progeny of transformed wheat plants showed resistance to cyanamide, whereas sensitive plants expressed a lethal necrosis and yellowing when cyanamide was applied. This gene has several potential advantages when compared with other selectable marker genes. Transformed wheat plants can be selected at the tissue culture level and may be able to convert cyanamide into a useful nitrogen compound (fertilizer). The selectable marker gene could be introduced with other genes for value‐added traits in wheat and might also be applicable in other transformation systems.
Preliminary Analysis of Expressed Sequence Tags for Sugarcane
Authors: Carson Deborah L. , Botha Frederik C.
Published: July 2010

Sugarcane (Saccharum spp. hybrids), with its complex polyploid genome, is not well understood at the genetic level. Partial sequencing of anonymous cDNA clones is a widely used technique for gene identification. These partial cDNA sequences, or Expressed Sequence Tags (ESTs) have potential application for the identification of important genes for genetic manipulation. This study aimed to initiate the preliminary development of an EST database for sugarcane and thereby gain some potentially useful information on sugarcane gene sequences. A nondirectional cDNA library has been constructed from sugarcane leaf roll (meristematic region) tissue. Two hundred fifty clones have been randomly selected, subjected to single‐pass sequencing from the 5′ end of the vector, and identified by sequence similarity searches against gene sequences in international databases. Of the 250 leaf roll clones, 26% exhibit similarity to known plant genes, 50% to non‐plant genes, while 24% represent new gene sequences. Analysis of the identified clones indicated sequence similarity to a broad diversity of genes encoding proteins such as enzymes, structural proteins, and regulatory factors. A significant proportion of genes identified in the leaf roll were involved in processes related to protein synthesis and protein modification, as would be expected in meristematic tissues. These results present a successful application of EST analysis in sugarcane and provide a preliminary indication of gene expression in leaf roll tissue.
Genetic Diversity Patterns in Chinese Soybean Cultivars Based on Coefficient of Parentage
Authors: Cui Zhanglin , Carter Thomas E. , Burton Joseph W.
Published: July 2010

China released 651 soybean [Glycine max (L.) Merr.] cultivars from 1923 to 1995. However, their diversity is not well characterized. The objective of this study was to quantify genetic diversity in Chinese cultivars via coefficient of parentage (CP), and the relative importance of geographical growing region, province of origin, intended cropping system, era of release, and breeder preferences in determining that diversity. A very low mean CP of 0.02 was found in Chinese soybean cultivars, suggesting the presence of a potentially high level of genetic diversity in Chinese soybean breeding. Cultivar pools from each of the three growing regions of China were almost completely unrelated to each other and exhibited low within‐region mean CP values (<0.06). Similarly, mean CP values within‐ and between‐provinces were low (0–0.2). Cropping systems and release eras also exhibited low within‐ and between‐CP relationships (all <0.07). The low CP values detected here for Chinese soybean breeding resulted from Chinese breeder initiatives to introduce new germplasm into applied Chinese breeding since the 1970s and from a strong tendency to avoid the mating of related parents. Half‐ and full‐sib matings and backcrossing are almost absent from Chinese pedigrees. Although mean CP for cultivars was low, cluster analysis proved to be a surprisingly effective discriminator of diversity patterns. This analysis assigned 270 cultivars to 20 clusters explaining 41% of the total variability in CP. Clusters were almost completely unrelated to each other and could be used as a basis for selection of parents for breeding. Pedigree analysis revealed that more than 30 cultivars grown currently in China trace to U.S. stocks. This successful use of U.S. germplasm in China may provide an important example for future U.S. breeding strategy.
Reflectance indices with precision and accuracy in predicting cotton leaf nitrogen concentration
Authors: Tarpley Lee , Reddy K. Raja , Sassenrath-Cole Gretchen F.
Published: July 2010

Diagnostic methods assaying leaf optical properties can aid rapid site‐specific screening of crop nitrogen status. A set of calibration curves relating many 1.5‐nm band reflectance ratios to cotton (Gossypium hirsutum L.) leaf N concentration was established from plants grown in sunlit growth chambers and at a range of nitrogen levels. Predicted and actual concentrations were compared by regression for a validation set of field‐grown leaf samples from diverse genotypes. Only those ratios that combined a red‐edge measure (700 or 716 nm) with a waveband of high reflectance in the very near infrared region (755–920 and 1000 nm) provided good precision (correlation) and accuracy (one‐to‐one relationship between predicted to actual values). Other indices that included a chlorophyll‐based reflectance feature also had good precision but were less accurate than those obtained from the red‐edge/very‐near‐infrared reflectance ratios.
Sixty Years of Improvement in Publicly Developed Elite Soybean Lines
Authors: Wilcox James R.
Published: July 2010

Publicly supported soybean [Glycine max (L.) Merr.] breeders evaluate their elite breeding lines in cooperative tests across the northern soybean production area of the USA and Canada. These cooperative tests have been conducted for 60 yr, and virtually all publicly released cultivars have been evaluated in these tests. However, the progress made has not been reported. The objective of this research was to determine progress in elite line improvement in soybean adapted to northern soybean production areas across this 60‐yr period. Two‐year performance data for the three highest‐yielding entries in these tests were regressed on years that entries appeared in maturity group (MG) tests across a 60‐yr period. Rates of yield improvement in kg ha−1 yr−1 were 21.6 (MG 00), 25.8 (MG 0), 30.4 (MG I), 29.3 (MG II), 30.6 MG (III), and 29.5 (MG IV). In general, check cultivars were consistent in performance across years in which the checks were included in the tests. Plant height increased slightly for elite lines in MG I, but decreased significantly for elite lines in MGs II to IV. Plant lodging decreased significantly for elite lines in every MG test except MG I. Seed protein concentration decreased significantly for elite lines only in MG I (−0.29 g kg−1 yr−1) and II (−0.27 g kg−1 yr−1). Seed oil increased significantly in MG 00 (0.19 g kg−1 yr−1) and decreased significantly in MG III (−0.11 g kg−1 yr−1). The data demonstrate that soybean breeders have increased seed yield of cultivars by ≈1.0% yr−1, while significantly increasing resistance to plant lodging. Rates of yield improvement during the past 20 yr have been equal to or greater than rates of improvement in earlier years.
Genetic Background and Environment Influence Palmitate Content of Soybean Seed Oil
Authors: Rebetzke G. J. , Pantalone V. R. , Burton J. W. , Carter T. E. , Wilson R. F.
Published: July 2010

Dietary concerns over high saturates contained in edible vegetable oils has stimulated development of soybean [Glycine max (L.) Merr.] cultivars with reduced palmitate content. Little is known of factors that might influence phenotypic expression of palmitate content among soybean populations varying for presence of a major reduced palmitate allele. The objective of this study was to investigate how environment and genetic background influence palmitate content when introducing the reduced palmitate trait into adapted backgrounds. Crosses were made between reduced palmitate germplasm, N87‐2122‐4 (53 g kg−1 palmitate) and normal palmitate cultivars, A3733, Burlison, Kenwood, P9273, and P9341 (103–123 g kg−1 palmitate). For each cross, F4:6 lines homozygous for major reduced or normal palmitate alleles were bulked separately into Maturity Groups (MG) II, III, IV, and V, and evaluated in 10 contrasting field environments during 1993. Palmitate content varied between 82 and 90 g kg−1 across southern U.S. and Puerto Rican environments. Much of this environmental variation was associated with changes in minimum temperature during the growing season. Genetic background effects were highly significant (P < 0.01) with cross means for palmitate content ranging between 81 and 93 g kg−1 Across different maturity groups, palmitate content of the progeny was correlated (r = 0.94–0.99, P < 0.05) with mean content of the normal palmitate parent, such that for every 1 g kg−1 palmitate increase in the normal palmitate parent there was a 0.32 to 0.51 g kg−1 palmitate increase in the progeny. Genetic background effects were presumed to be associated with action of minor alleles transmitted from the normal palmitate parent. Presence of the reduced palmitate allele was associated with significantly (P < 0.01) lower stearate (−6 to −13%) and higher oleate (+4 to +10%) contents across all maturity groups. Selection of low palmitate, high‐yielding parents should further decrease palmitate content and produce correlated improvements in stearate and oleate contents to improve overall oil quality in progeny containing reduced palmitate alleles.
Deletion Mapping of a Nematode Resistance Gene on Rye Chromosome 6R in Wheat
Authors: Dundas Ian S. , Frappell Deirdre E. , Crack Donna M. , Fisher John M.
Published: July 2010

Four deletion mutants of rye chromosome 6R were identified in progeny of wheat (Triticum aestivum L.) lines of ph1bph1b genotype and monosomic for chromosome 6R. The rye chromosome carried a resistance gene against the cereal cyst nematode (CCN) (Heterodera avenae Woll.) and this chromosome originated in triticale line T‐701 (× Triticosecale Witt.). The deletion mutants were selected on the basis of dissociation of three isozyme loci on the long arm of the rye (Secale cereale L.) chromosome. Three plants and their progeny showed expression of the rye genes α‐Amy‐R1 and Got‐R2 but lacked the gene PgdR2 The other plant and its progeny showed expression of the α‐Amy‐R1 gene while the genes Got‐R2 and PgdR2 were absent. The four deletion chromosomes displayed long‐arm terminal deficiencies of different sizes which enabled mapping of the rye isozyme genes and the CCN resistance gene. The distal to proximal order of the 6R isozyme loci was found to be: PgdR2, Got‐R2, and then α‐Amy‐R1 Bioassay tests demonstrated that the CCN resistance gene (CreR) was located on an interstitial section of the long arm of 6R adjacent to Got‐R2
Crop Sequence Effects on Soybean Cyst Nematode and Soybean and Corn Yields
Authors: Chen Senyu , Porter Paul M. , Reese Curtis D. , Stienstra Ward C.
Published: July 2010

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a destructive pest of soybean, Glycine max (L.) Merr. Field research was conducted at Waseca and Lamberton, MN, from 1996 through 1999 to evaluate the effect of crop sequence on SCN population density and on crop yields. Cropping sequence treatments were (i) monocultures of corn (Zea mays L.), SCN‐resistant soybean, and SCN‐susceptible soybean; (ii) susceptible soybean rotated with 1, 2, or 3 yr of corn; (iii) resistant soybean rotated annually with corn; and (iv) rotation of corn–resistant soybean–corn–susceptible soybean. Egg density was determined at sowing and harvest, and crop yields were determined each year. In general, yields of resistant soybean were higher than susceptible soybean. Resistant soybean in annual rotation with corn produced the highest yield, and susceptible soybean in monoculture produced the lowest yield among all treatments. A longer period of corn in rotation resulted in higher yield of subsequent susceptible soybean in most instances. Yields of corn following corn were lower than following soybean. Egg density at the start of the study was 6994 and 14 000 eggs 100 cm−3 soil at Waseca and Lamberton, respectively. Average Pf/Pi (egg density at harvest/egg density at sowing) was 0.59 (0.23–0.86) for corn, 0.49 (0.21–0.73) for resistant soybean, and 3.3 (0.74–9.91) for susceptible soybean for all treatments at the two sites across the 4‐yr period. After 3 yr of corn, egg density decreased to 889 and 3695 eggs 100 cm−3 soil at Waseca and Lamberton, respectively. Annual rotation of resistant soybean and corn resulted in the lowest SCN population density and produced the highest yield of both crops.
Plant Growth Regulator and Mowing Height Effects on Seasonal Root Growth of Penncross Creeping Bentgrass
Authors: Fagerness Matthew J. , Yelverton Fred H.
Published: July 2010

Summer decline of creeping bentgrass [Agrostis palustris Huds. (=Agrostis stolonifera var. palustris (Huds.) Farw.] root growth is an annual concern in many regions of the USA. A 2‐yr field study was conducted to investigate the effects of mowing height and plant growth regulator (PGR) treatments on root biomass (RB) patterns in ‘Penncross’ creeping bentgrass, grown on a Wakulla sand (sandy, siliceous, Thermic Psammentic Hapludults) with 94% sand, 4% silt, 2% clay, 24 mg g−1 organic matter, and a pH of 6.1. Plots were maintained at 3.2, 4.0, or 4.8 mm throughout the experiment. Plant growth regulator treatments were trinexapac‐ethyl, [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxo‐cyclohexane carboxylic acid ethyl ester] applied at 0.05 kg a.i. ha−1 and paclobutrazol, {(±)‐(R*,R*)‐β‐[(4‐chloro‐phenyl)methyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol} applied at 0.14, 0.28, or 0.56 kg a.i. ha−1 Plant growth regulator treatments initially were applied in April 1997 and were reapplied monthly for 24 mo. Annual variation in air and soil temperature accounted for variable RB across years. Root biomass declined 76% from a May maximum to a minimum in September; however, RB increased between September and January. Turf mowed to a height of 3.2 mm consistently had lower RB than turf maintained at 4.0 or 4.8 mm, and had slower early autumn RB recovery. When averaged across mowing heights, only paclobutrazol (0.56 kg a.i. ha−1) reduced RB and no PGR increased rooting when compared with nontreated turf. From September to January of each year, a PGR by mowing height interaction showed that paclobutrazol applied at 0.56 kg a.i. ha−1 delayed RB recovery in turf mowed to a height of 4.8 mm, while no PGR delayed RB recovery in turf maintained at the 3.2 mm mowing height. Slower RB recovery in turf mowed to 3.2 mm following the September minimum RB was attributed to reductions in turf quality and density, rather than the effects of PGRs. Paclobutrazol only reduced Penncross RB when applied at twice the labeled rate and with greater application frequency than is typical for most PGR use patterns. These results showed that labeled rates of paclobutrazol and trinexapac‐ethyl did not adversely affect root growth under putting green conditions.
Factors Modifying Frost Tolerance of Legume Species
Authors: Badaruddin M. , Meyer D. W.
Published: July 2010

Variability in seedling death of legumes because of spring frost in the USA and Canada is associated with several factors. Experiments were conducted to evaluate factors that modify frost tolerance of seedling legumes. Experiment 1 was comprised of two hardenings, three freezing temperatures, eight legume species, and four growth stages. Experiment 2 had three temperatures, four durations of temperature, and four legume species. Experiment 3 included three soil types, two soil water levels, and two legume species. At each growth stage, legume seedlings were placed in a programmable freezing chamber at 3°C and temperature decreased/increased 1°C h−1 to and from a minimum freezing temperature. Duration of minimum freezing temperature was 1 h for Experiments 1 and 3 and varied according to the treatment in Experiment 2. Hardening increased seedling survival up to 40% over unhardened seedlings across growth stages and species. Forage legumes were more frost tolerant than soybean [Glycine max (L.) Merr.] and field pea (Pisum sativum L.) at all temperatures. Increase in duration of freezing temperature decreased the frost tolerance of all species when freezing temperature was near the LT50 (temperature that kills 50% of seedlings). Seedling survival of both alfalfa (Medicago sativa L.) and soybean was greater in light‐textured soil than the heavy‐textured soil with soil water at field capacity. However, one‐third of field capacity soil water allowed greater seedling survival in the heavy‐textured than the light‐textured soil. The results suggest that the factors studied should be considered to assess the frost tolerance of legume seedlings.
Comparative Bread Quality of White Flour and Whole Grain Flour for Hard Red Spring and Winter Wheat
Authors: Bruckner P. L. , Habernicht D. , Carlson G. R. , Wichman D. M. , Talbert L. E.
Published: July 2010

Superior bread‐making quality is a primary objective for most hard red wheat (Triticum aestivum L.) breeding programs. Milled white flour is traditionally used to measure quality. There is increasing demand in the domestic market for whole grain bread products. The objective of this research was to determine the relationship of bread quality parameters based on white flour versus whole wheat flour in a set of hard red spring and hard red winter wheat genotypes. Quality evaluations were conducted on sets of genotypes grown in four environments for both wheat classes. Correlations of genotype performance for white flour versus whole meal varied with the traits. Protein levels were highly correlated, but correlations tended to decrease as dough was processed into a final product. This was especially true for hard red spring wheat genotypes. Mixograph tolerance of white flour versus whole meal was correlated highly for both spring and winter wheat, while water absorption was correlated poorly for both classes of wheat. Correlations for final loaf volume of whole wheat versus white flour was significant in two environments, and ranged from 0.08 to 0.72 for spring wheat genotypes. Correlations for loaf volume were significant in all environments, and ranged from 0.76 to 0.92 for winter wheat genotypes. In general, our data indicated that quality measured on white flour could be used as an estimate of whole wheat performance, but that identification of the best genotypes for whole wheat performance may require separate quality analysis.
Genetic Mapping of a Macromutation and Quantitative Trait Loci underlying Fatty Acid Composition Differences in Meadowfoam Oil
Authors: Katengam Sureeporn , Crane Jimmie M. , Slabaugh Mary B. , Knapp Steven J.
Published: July 2010

The seed oil of meadowfoam (Limnanthes alba Hartw. ex Benth.) is a rich source of very long‐chain fatty acids (VLCs), primarily 20:1Δ5, 22:1Δ5, 22:1Δ13 (erucic acid), and 22:2Δ5Δ13 (dienoic acid). Wild‐type L alba ssp. versicolor populations produce more erucic and less dienoic acid than wild‐type L. alba ssp. alba populations, phenotypic differences that are caused by the macromutation E and possibly by quantitative trait loci (QTL). The aim of this study was to map the E locus and QTL affecting fatty acid concentrations among intersubspecific backcross progeny. The segregation ratio for the E locus (94 Ee to 86 ee progeny) was not significantly different from one to one (P = 0.84). The E locus was associated with 94 and 77% of the phenotypic variance for erucic and dienoic acid concentration, respectively. Erucic acid varied from 42 to 151 g kg−1 among Ee and 185 to 269 g kg−1 among ee progeny, while dienoic acid varied from 151 to 318 g kg−1 among Ee and 66 to 209 g kg−1 among ee progeny. The E locus mapped to Linkage Group 4 and pleiotropically affected every VLC. Composite interval mapping, performed with the E locus and 18 background markers as cofactors, was used to search the genome for QTL. Two significant QTL peaks were found for erucic and dienoic acid on Linkage Group 4. One QTL was centered on the E locus and produced a massive peak. The other QTL produced a marginally significant peak 30.4 cM downstream of the E locus and was associated with less than 1% of the phenotypic variance. The segregation of additional QTL in this population affecting dienoic acid cannot be ruled out.
What If We Knew All the Genes for a Quantitative Trait in Hybrid Crops?
Authors: Bernardo Rex
Published: July 2010

Plant genomics programs are expected to decipher the sequence and function of genes controlling important traits. Most of the important traits in crops are quantitative and are controlled jointly by many loci. What if we knew all the genes for a quantitative trait in hybrid crops? Will genomics enhance hybrid crop breeding, which currently involves selection on the basis of phenotypes rather than gene information? With maize (Zea mays L.) as a model species, I found through computer simulation that gene information is most useful in selection when few loci (e.g., 10) control the trait. With many loci (≥50), the least squares estimates of gene effects become imprecise. Gene information consequently improves selection efficiency among hybrids by only 10% or less, and actually becomes detrimental to selection as more loci become known. Increasing the population size and trait heritability to improve the estimates of gene effects also improves phenotypic selection, leaving little room for improvement of selection efficiency via gene information. The typical reductionist approach in genomics therefore has limited potential for enhancing selection for quantitative traits in hybrid crops.
Straw Production and Grain Yield Relationships in Winter Wheat
Authors: Donaldson Edwin , Schillinger William F. , Dofing Stephen M.
Published: July 2010

Winter wheat (Triticum aestivum L.) –fallow is the predominant cropping system in low‐precipitation regions (<250 mm annually) of the inland Pacific Northwest (PNW) in the USA. Wind erosion is a recurrent problem during and after fallow periods when inadequate crop residue amounts are retained on the soil surface. Management options that optimize both grain yield and straw production are needed. A 3‐yr field study was conducted to determine sowing rate and sowing date effects on straw and grain yield, and grain yield components of winter wheat cultivars with semidwarf, standard height, or tall growth habit. Four winter wheat cultivars were evaluated at three sowing rates (65, 130, and 195 seeds m−2) and three sowing dates in August, September, and October. A split plot design was used, with sowing dates as main plots and sowing rate × cultivar combinations as subplots. The greatest effect of sowing date was on straw production. Straw biomass from mid‐August sowing averaged 6.70 Mg ha−1 compared with 4.65 and 2.78 Mg ha−1 from mid‐September and mid‐October sowing, respectively. Grain yield was highest for mid‐August sowing during two years and lowest for mid‐October sowing all years. Averaged across years, the semidwarf cultivar produced the highest grain yield on all sowing dates and was equal to the standard height and tall cultivars for straw production. Path coefficient analysis showed that variation in grain yield was due primarily to differences in spikes per unit area (SPU) and kernels per spike (KPS). Late sowing resulted in a large reduction in SPU and, therefore, grain yield. For cropland susceptible to wind erosion in east‐central Washington, early sowing results in increased wheat straw production and generally higher grain yield compared with mid‐to‐late sowing dates.
Effect of Drought on Growth, Carbohydrates, and Soil Water Use by Perennial Ryegrass, Tall Fescue, and White Clover
Authors: Karsten H.D. , MacAdam J.W.
Published: July 2010

In irrigated pastures of the semiarid, high‐elevation western USA, perennial ryegrass (Lolium perenne L.) persistence is poor, and over time white clover (Trifolium repens L.) often dominates mixtures. Irrigation is often not available during autumn, when these perennial plants store carbohydrate reserves for spring regrowth. Our objective was to compare the effect of water stress on growth, carbohydrates, and soil water use of perennial ryegrass, white clover, and tall fescue (Festuca arundinacea Schreb.) in a greenhouse study. These three species were grown separately in a Kidman fine sandy loam, in 15‐cm‐diam, 1‐m‐deep pots and irrigated for 81 d (4 plants/pot). Paired pots were then either irrigated or subjected to water deficit (drought) for 30 d, followed by 10 d of recovery with irrigation. At 10‐d intervals, four paired pots of each species were destructively sampled to determine leaf and storage organ dry matter and carbohydrate and simple sugar concentrations in storage organs. Root length density and soil water content were also sampled at 20‐, 60‐, and 90‐cm soil depths. Leaf dry matter was lower in water‐stressed plants than in irrigated plants by the end of the drought, but did not differ among species. After 10 d of recovery, storage carbohydrate concentration in droughted perennial ryegrass was lower than in white clover, and the ratio of simple sugars (droughted:irrigated) in perennial ryegrass was higher than in white clover. Tall fescue performed similarly to both species. Before the drought, grasses had similar, extensive root systems that withdrew more soil water from the 90‐cm soil depth than did white clover. By the end of the 30‐d drought, white clover had reduced soil water at all depths as much as the grasses. White clover survived drought and conserved carbohydrate reserves after 10 d of recovery better than did perennial ryegrass and similarly to tall fescue.
Identification and Characterization of Near‐Isogenic Hard and Soft Hexaploid Wheats
Authors: Morris Craig F. , King Garrison E. , Allan Robert E. , Simeone Marco C.
Published: July 2010

A complete understanding of the physical–chemical mechanism and underlying genetic control of wheat (Triticum aestivum L.) endosperm texture will contribute to defining optimal grain utilization while assisting the breeding and development of new cultivars. World trade in wheat grain primarily is based on the two main market classes, “soft” and “hard,” which are mostly determined by the expression of the puroindoline genes at the Hardness (Ha) locus. Here we identify and characterize new genetic stocks (near isogenic lines, NILs) in four different genetic backgrounds (20 NILs total, nine hard and 11 soft). Methods included identifying homogenous or mixed texture lines by Single Kernel Characterization System and Near‐Infrared Reflectance Spectroscopy. Puroindoline genes and Ha alleles were determined through nucleic acid sequence analysis. The four different genetic sources for NILs were (i) accessions of ‘Gamenya’ cultivar which were physical mixtures of hard and soft types, (ii) existing near‐isogenic lines from the cultivars Heron and Falcon, (iii) advanced‐generation backcross lines involving ‘Paha’ and ‘Early Blackhull,’ and (iv) ‘Nugaines’ and ‘Early Blackhull Derivative’. The NILs reported here provide new genetic materials for the study of wheat grain texture and the effect of puroindolines and the Hardness gene on end‐use quality. Two of the four sets of NILs possess the Gly‐46 to Ser‐46 Pinb‐D1b hardness allele which has not been previously available in NILs. The results corroborate a model of wheat grain texture that identifies two major hardness classes, as opposed to one that accommodates intermediate texture classes such as “semi‐hard” and “medium‐soft.” A direct role of the puroindoline proteins in conferring soft grain phenotype is supported; conversely, no genetic basis for intermediate hardness was found. Rather, intermediate hardness resulted from mixtures of the soft and hard classes.
Trinexapac‐ethyl effects on kentucky bluegrass evapotranspiration
Authors: Ervin E.H. , Koski A.J.
Published: July 2010

Many researchers have reported that trinexapac‐ethyl [4‐(cyclopropyl‐hydroxy‐methylene)‐3,5‐dioxo‐cyclohexane‐carboxylic acid ethylester] effectively reduces turfgrass leaf elongation and subsequent clipping production. Our hypothesis is that trinexapac‐ethyl (TE) induced canopy growth and conductance reductions may also reduce turfgrass evapotranspiration (ET) rates. This study was conducted to determine if application of TE to mature, field‐grown Kentucky bluegrass (Poa pratensis L. ‘NuStar’) would result in reduced weekly ET rates as measured by weighing bucket lysimeters. A randomized complete block design was used to compare the weekly ET rate (mm week−1) of Kentucky bluegrass (KBG) treated or not with TE (0.27 kg ha−1). Weighing bucket lysimeters containing KBG were treated with TE three times per year at 6‐wk intervals in 1995, 1996, and 1997. Trinexapac‐ethyl reduced KBG weekly ET in 5 wk out of a total of 34 wk sampled over 3 yr. Higher ET rates were not correlated with weekly clipping production for either untreated or TE‐treated KBG. Possible ET reductions, coupled with reduced clipping production, indicate TE is an effective tool for managing numerous turfgrass systems.
Responses to Divergent Selection for Fiber Concentration at Two Disease Potentials in Smooth Bromegrass
Authors: Han L.X. , Casler M.D. , Grau C.R.
Published: July 2010

Neutral detergent fiber (NDF) concentration is related to intake potential of forages but might also be related to plant reaction to pathogens. Three smooth bromegrass (Bromus inermis Leyss.) populations from these cycles of uniparental mass selection for low NDF, one cycle of biparental mass selection for high NDF, and the base population were evaluated at high and low disease potentials at three locations for 2 yr and three harvests each year. High disease severity, measured as proportion of foliage diseased, was associated with high NDF and high lignin concentration (on a dry‐matter basis and a cell‐wall basis). Nevertheless, disease potentials did not affect the relative performance of selection cycles on any traits measured. On average, NDF was reduced 3.5 g kg−1 DM per cycle (P < 0.001) by selection for low NDF, and increased 11.1 g kg−1 DM in one cycle (P < 0.001) by selection for high NDF. For the spring harvest, the response in NDF could partially be attributed to a change in heading index. A positive correlated response in acid detergent lignin was found in the spring (P < 0.001) while a negative correlated response in cell wall lignin was detected in the summer and fall (P < 0.001). Selection for NDF modified the composition of NDF, as cell wall hemicellulose changed in the opposite direction of NDF. Lower dry matter yield per plant appeared to be associated with lower NDF and higher inbreeding. Selection for low NDF, accompanied by slight selection pressure on disease resistance, resulted in a reduction of NDF without an increase in disease susceptibility.
Developing Genetic Coefficients for Crop Simulation Models with Data from Crop Performance Trials
Authors: Mavromatis T. , Boote K.J. , Jones J.W. , Irmak A. , Shinde D. , Hoogenboom G.
Published: July 2010

Successful uses of crop models in technology transfer and decision support tools require that coefficients describing new cultivars be available as soon as the cultivars are marketed. The objectives of this study were (i) to develop an approach to estimate cultivar coefficients for the CROPGRO–Soybean model from typical information provided by crop performance tests, (ii) to evaluate the suitability of yield trial data for deriving genetic coefficients and site‐specific soil traits for use in crop models, and (iii) to explore the extent to which our approach allowed the crop model to reproduce observed genotype × environment (GE) interactions, cultivar ranking, and year‐to‐year yield variability. Crop performance tests typically record harvest maturity date, seed yield, seed size, height, and lodging. A stepwise procedure using data on 11 cultivars grown at five sites in Georgia over 4 to 10 yr efficiently decreased the root mean square error (RMSE) between observed and predicted data. For ‘Stonewall’, a maturity group VII cultivar, the RMSE of 769 kg ha−1 between the actual and modeled seed yield, estimated initially by means of the existing general maturity group coefficients, was reduced to 404 kg ha−1 For the same cultivar, the initial RMSE of 5.3 and 9.3 d between the actual and simulated anthesis and harvest maturity dates, respectively, estimated by means of the existing general maturity group coefficients, were reduced to 2.9 and 5.8 d. In addition to deriving useful information on site characteristics and cultivar traits, our approach has enabled CROPGRO to satisfactorily mimic the genotypic yield ranking and much of observed genotype × environment interactions. Across all environments, the difference in genotype ranking based on yield between measured and predicted values was one or less for 61% of the environments.
Inheritance of Septoria Tritici Blotch Resistance in Winter Wheat
Authors: Zhang X. , Haley S.D. , Jin Y.
Published: July 2010

Septoria tritici blotch (STB), a fungal foliar disease of wheat (Triticum aestivum L.) caused by Septoria tritici Rob. ex Desm., is a major constraint to wheat production worldwide. Understanding the inheritance of resistance in known resistant genotypes would potentially lead to more efficient deployment of host plant resistance. In our study, inheritance of seedling STB resistance was evaluated by an eight‐parent full diallel set of crosses. Parents, F1, and reciprocal F1 were planted in a greenhouse on three different dates. Within each planting date, three to five seeds of each entry were planted in a randomized complete block design with three replicates. Plants at the second‐leaf stage were inoculated with a bulk of six S. tritici isolates. Significant general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were observed in the analysis of variance. The ratio of GCA sum of squares relative to SCA sum of squares suggested that GCA was more important than SCA. Additive gene effects played a major role in host response to STB, while nonadditive gene effects were also detected. General combining ability effects of individual genotypes were in a close agreement with parental performance. ‘KS94U338’, a genotype with putative resistance derived from Aegilops tauschii Coss., had the lowest STB score and the highest general combining ability. Our results suggested that KS94U338, which possesses resistance thought to be distinct from other known sources, should prove useful in breeding efforts to improve STB resistance in wheat.
Relative Sensitivity of Spring Wheat Grain Yield and Quality Parameters to Moisture Deficit
Authors: Guttieri Mary J. , Stark Jeffrey C. , O'Brien Katherine , Souza Edward
Published: July 2010

Moisture stress influences both yield and end‐use quality of wheat (Triticum aestivum L.). Previous studies assessed stability of yield and yield components to moisture stress. This study evaluated the stability of spring wheat quality parameters relative to the stability of grain yield and its components under moisture stress. Sixteen spring wheat cultivars were produced under two moisture‐deficit regimes in 1995 and 1996 to determine the effects of moisture‐deficit severity on grain yield and its components, test weight, flour protein, flour extraction, dough‐mixing characteristics, and alkaline noodle color. Moisture deficit differentially and significantly influenced cultivar test weight and yield. The overall moisture‐deficit‐induced reduction in yield was due primarily to reduction in kernel weight; effects of moisture deficit on yield of specific cultivars were due largely to effects on kernels per spike. Drought‐sensitivity indices (DSIs) for yield were correlated to cultivar yield potential. Yield reduction by moderate moisture deficit was not predictive of yield reduction by severe moisture deficit. Effects of moisture‐deficit severity on flour extraction and mixograph peak time varied with cultivar. Moisture deficit reduced initial noodle brightness and enhanced noodle yellowness. However, the color of noodles produced by the cultivars included in this study responded similarly to moisture deficit, suggesting that evaluation of noodle color may not require testing across moisture‐deficit environments. Test weight and flour extraction DSIs were correlated with DSIs for grain yield. Therefore, identifying drought‐tolerant genotypes based on yield stability under moisture stress also will identify genotypes having stable test weight and flour extraction.
Responses of Tall Fescue Cultivars to an Irrigation Gradient
Authors: Asay Kay H. , Jensen Kevin B. , Waldron Blair L.
Published: July 2010

Seasonal availability of water is a major consideration in the management and selection of plant materials for irrigated pastures in the Intermountain West, USA. Objectives were to evaluate the forage yield of 10 tall fescue (Festuca arundinacea Schreb.) strains and cultivars across five irrigation levels and to elucidate the effects of the endophytic fungus Neotyphodium coenophialum (Morgan‐Jones & Gems) Glenn, Bacon & Hanlin on productivity and trends. A line‐source irrigation system was used in a 2‐yr study. Significant differences were detected among the tall fescue entries for dry matter yield (DMY), and differences were relatively consistent across water levels (WL) as indicated by the nonsignificant cultivar × WL interaction and significant correlations among WL. Trends in DMY across WL were largely curvilinear; however, linear trends were much more predominant during the late summer and fall. Stability parameters, based on regression of cultivar × WL × year means on their respective WL × year means, differed among cultivars in analyses including all harvests but were relatively uniform (b ≈ 1.0) for most cultivars later in the season. Differences in DMY between ‘Ky 31’ tall fescue infected with the Neotyphodium endophyte and its endophyte‐free counterpart confirms earlier reports of the positive effect of this fungal organism on forage yield in tall fescue, particularly in water‐limited environments. Seasonal distribution of yield was primarily determined by water availability during the late summer and fall. The relative consistency in DMY of the cultivars across WL indicates that annual yield averaged across levels of water stress would be a logical criterion for selection of germplasm for irrigated pastures in the Intermountain Region.
Incorporating Radiation and Nitrogen Nutrition into a Model of Kernel Number in Wheat
Authors: Demotes‐Mainard Sabine , Jeuffroy Marie‐Hélène
Published: July 2010

Wheat (Triticum aestivum L.) kernel number per square meter (KN) depends on radiation, temperature, and crop N nutrition. Some models of KN using climatic data or N nutrition characteristics as input variables account for variations either in radiation and temperature or in N nutrition, but not for both. Our objective was to produce a model of KN that accounts simultaneously for variations due to radiation, temperature, and crop N nutrition, and that has input variables that are simple to measure or to simulate. Field experiments were conducted over 3 yr with ‘Trémie’ winter wheat. Treatments involved the application of N fertilizer at different dates and rates to achieve various N deficiencies and the use of shading nets for various periods during spike growth to reduce incident radiation. Crop N status was assessed by determining N nutrition index (NNI) at anthesis. The KN was counted, it ranged from 9420 to 31 036 kernels m−2 Two characteristics of N nutrition (NNI at anthesis and IDD, the duration of deficiency before anthesis multiplied by its intensity) and three characteristics of radiation and temperature (photothermal quotient calculated from 45 d before anthesis to anthesis, from 30 d before anthesis to anthesis and from 20 d before anthesis to 10 d after anthesis) were used as input variables. Six relationships combining one characteristic of N nutrition and the photothermal quotient over one period were estimated. The best fit was obtained for a relationship between KN and the logarithm of NNI at anthesis and photothermal quotient over the 45 d preceding anthesis (R2 = 0.883, n = 19). This relationship could be useful for estimating KN in crop models, as its input variables are simple to simulate.
Freezing Tolerance and Carbohydrate Changes during Cold Acclimation of Green‐Type Annual Bluegrass (Poa annua L.) Ecotypes
Authors: Dionne Julie , Castonguay Yves , Nadeau Paul , Desjardins Yves
Published: July 2010

Winterkill is recurrently observed on annual bluegrass (Poa annua L.) golf greens in northern climates. Although annual bluegrass susceptibility to freezing temperatures has been pointed out as a major factor responsible for winter damages, little information exists on freezing tolerance and cold hardening of green‐type annual bluegrass. This study was conducted to assess freezing tolerance and carbohydrate changes occurring during cold acclimation of green‐type annual bluegrass ecotypes cold hardened under both environmentally controlled and simulated winter conditions in an unheated greenhouse. The 50% killing temperatures (LT50), levels of fructans, and mono and disaccharides were determined during cold acclimation in three annual bluegrass ecotypes originating from Western Pennsylvania (OK), Coastal Maryland (CO) and Central Québec (CR). The ecotypes differed significantly with regard to their freezing tolerance (LT50 ranking: OK < CO < CR) and maintained their relative ranking under both environmentally controlled and simulated‐natural winter conditions. Maximum freezing tolerance was observed after exposure to nonlethal subfreezing temperatures and annual bluegrass achieved high levels of freezing tolerance with LT50 of −31.2°C for OK, −24.6°C for CO, and −22.8°C for CR. High molecular weight fructans (DP>6) were the most abundant carbohydrates found in plants cold‐acclimated under low, nonfreezing temperature with levels up to 170 mg g−1 dry weight as compared with 60 to 70 mg g−1 dry weight in nonacclimated plants. Sucrose levels in crowns of annual bluegrass markedly increased at temperatures below freezing and maximum sucrose concentration coincided with maximum freezing tolerance of annual bluegrass. However, variations in fructan and sucrose levels were not related to differential freezing tolerance among the three annual bluegrass ecotypes tested.