bluuebunny/crossref_metadata_2025 huggingface dataset:
Models for Predicting the Lower Limit of the Canopy‐Air Temperature Difference of Two Cool Season Grasses
Authors: Martin D. L. , Wehner D. J. , Throssell C. S.
Published: July 2010

Estimation of the lower limit of the canopy‐air temperature differential, (Tc−Ta)LL, is required for calculation of an empirically‐based crop water stress, index. This research determined the complexity of model needed for accurate estimation of (Tc −T a)LL for several field grown cultivars of Kentucky bluegrass (Poa pratensis L.) and for creeping bentgrass (Agrostis stolonifera L. var. palustris (Huds.) Farw.). Regression models using vapor pressure deficit of the air (VRD), net radiation load (Rn), and wind speed (WS) were developed for predicting (Tc −T a)LL. The best one to three‐variable regression models for predicting (Tc −T a)LL used variable groups of VPD (r2 = 0.47); VPD and Rn (R2 = 0.66); and VPD, Rn, and WS (R2 = 0.82). Models developed for predicting (Tc −T a)LL on individual Kentucky bluegrass cultivars, across Kentucky bluegrass, and across both species were tested on a validation data set. Models using only VPD accounted for <2% of variation in actual (Tc −T a)LL of nonwater‐stressed turf. Models using VPD and Rn developed from pooled Kentucky bluegrass data, individual Kentucky bluegrass cultivars, or Kentucky bluegrass and creeping bentgrass data accounted for an average of 15, 13, and 14% of variation in actual (Tc −T a)LL, while models using VPD, Rn, and WS accounted for an average of 62, 62, and 64%, respectively. On creeping bentgrass, the Kentucky bluegrass model and dual species model introduced a large amount of bias to predicted (Tc −T a)LL. At sites where environmental conditions are highly variable, the effects of VPD, Rn, and WS must be taken into account to accurately predict (Tc −T a)LL of turfgrass. A single model appears appropriate for prediction of (Tc −T a)LL across Kentucky bluegrass cultivars; a separate model for creeping bentgrass is required.
RFLP Mapping in Maize: Quantitative Trait Loci Affecting Testcross Performance of Elite European Flint Lines
Authors: Schön Chris C. , Melchinger Albrecht E. , Boppenmaier Jürgen , Brunklaus‐Jung Elsbeth , Herrmann Reinhold G. , Seitzer Josef F.
Published: July 2010

The dissection of quantitative traits into their underlying Mendelian factors has become possible with the aid of molecular markers. In this study, we mapped and characterized quantitative trait loci (QTL) affecting testcross performance of maize (Zea mays L.) and discussed the consistency of these QTL across environments and testers. Two homozygous flint inbred lines were crossed to produce 380 F2 individuals which were genotyped at 89 restriction fragment length polymorphism (RFLP) marker loci. By selfing the F2 plants 380 F3 lines were produced and subsequently crossed to two diverse dent inbred testers (T1 and T2). Each series of testcrosses (TC) was evaluated in field trials with two replications in four environments. Three traits were analyzed: protein content, kernel weight, and plant height. Genotypic and genotype‐by‐environment interaction variances were highly significant for all traits in both TC series and heritabilities ranged between 0.71 and 0.85. Genotypic correlations between the two TC series were 0.80 (protein content), 0.88 (kernel weight), and 0.84 (plant height). The method of interval mapping was used for characterization of QTL. Protein content was significantly affected by four QTL in TC with T1 explaining 32% of the phenotypic variance () and five QTL in TC with T2 explaining 42% of . For kernel weight, eight putative QTL were found in TC with T1 and six were found for T2, explaining about 60% of . Seven QTL explained 52% and four 60% of for plant height. Results from QTL mapping agreed well across environments. Highly consistent results across testers were obtained for kernel weight and plant height but not for protein content. No significant evidence for epistasis among QTL was found.
Compensation Indices of Radiation‐Induced Wheat‐Agropyron elongatum Translocations Conferring Resistance to Leaf Rust and Stem Rust
Authors: Friebe B. , Jiang J. , Knott D. R. , Gill B. S.
Published: July 2010

Species belonging to the genus Agropyron are an important source of disease resistance for bread wheat. Several resistance genes have been transferred. C‐banding and in situ hybridization are the methods of choice for analyzing introgressed alien chromatin. Using these methods, we characterized radiation‐induced wheat‐Agropyron elongatum chromosome translocation lines carrying the rust resistance genes Sr26 and Sr25/Lr19. Data show that Sr26 is located on the translocation chromosome T6AS. 6AL‐6Ae#1L. The Ag. elongatum segment in this translocation has a length of 2.48 μm. The Sr25/Lr19 genes in cultivar ‘Agatha’ are located on a 2.55 μm long Ag. elongatum segment present in the translocation chromosome T7DS. 7DL‐7Ae#1L. The wheat‐Ag. elongatum translocation chromosome present in the ethyl methane‐sulfonate (EMS) treated derivative ‘Agatha‐28’ is similar to that present in Agatha. The Ag. elongatum segment present in the EMS treated derivative ‘Agatha‐235’ has a length of 1.99 pm and is inserted intercalary in the long arm of wheat chromosome 7D, resulting in the translocation chromosome T7DS‐7DL‐7Ae#1L‐7DL. A compensation (CI) index was calculated as the ratio of the length of the missing wheat segment as percent of the corresponding wheat arm divided by the length of the transferred alien segment as percent of the corresponding alien chromosome arm. The CIs in T6AS‐6AL‐6Ae#1L and T7DS‐7DL‐7Ae#1L are 1.15 and 0.95, respectively. These are close to the desirable value of I and indicate good compensation ability. The CI in T7DS. 7DL‐7Ae#1L‐7DL is 0.60 and indicates poor compensation ability. This index may allow the prediction of the performance of any compensating wheat‐alien chromosome translocation.
Inheritance in Soybean of Resistant and Necrotic Reactions to Soybean Mosaic Virus Strains
Authors: Chen P. , Buss G. R. , Roane C. W. , Tolin S. A.
Published: July 2010

Five soybean [Glycine max (L.) Merr.] cultivars, PI96983, ‘Ogden’, ‘York’, ‘Marshall’, and ‘Kwanggyo’, were studied to determine the inheritance of their resistant (R) or necrotic (N) reactions to soybean mosaic virus (SMV) strains G4, G5, G6, G7, and G7A. Each parent was crossed reciprocally with a susceptible (S) cultivar (‘Essex’ or ‘Lee 68’) to determine the number of genes for resistance or necrosis. The R parents were also crossed with each other to test the allelism of the genes conditioning the R or N reaction. All the F2 populations from N × S crosses segregated in a 3:1 ratio with necrosis being dominant to susceptibility. The absence of S segregants in F2 populations of N × N and R × R crosses and the lack of segregation in S × S crosses indicate that the single dominant genes in the five non‐susceptible parents are alleles at a common locus. All R × S crosses produced a combination of R, N, and S plants and gave a good fit to a 3(R + N):1S ratio. Two different SMV‐strain × resistance‐gene interactions were observed to produce the N reaction: (i) alleles which are necrotic to specific strains in the homozygous state are dominant to alleles which are resistant or susceptible to the same strain, (ii) alleles which are resistant in the homozygous state to a strain often exhibit necrosis when they occur in a heterozygote with a susceptible allele.
Light Quality and Stem Numbers in Cool‐Season Forage Grasses
Authors: Frank A. B. , Hofmann L.
Published: July 2010

The number of stems produced by cool‐season forage grasses is a major factor in determining forage production. Knowledge of factors that influence stem numbers will be useful in developing proper management practices. Objectives of this study were to (i) determine total stem numbers and the amount of far‐red (FR) and red (R) light at the crown level in canopies of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schultes], western wheatgrass [Pascopyrum smithii (Rydb.) Gould], and smooth bromegrass (Bromus inermis Leyss.) that were hayed, grazed, or ungrazed; and (ii) evaluate the relationship between the FR/R ratio at plant crown level and stem numbers. The study was conducted during 1989,1990, and 1991 at Mandan, ND, USA. Management practices produced differences in both FR/R ratios and stem numbers. Treatment effects on stem numbers were consistent over years for smooth bromegrass whereas treatment × year interactions were significant for crested wheatgrass and western wheatgrass. Generally, stem numbers were greatest for all species that were hayed followed in order by grazed and ungrazed treatments. Grazed and ungrazed plants developed longer leaves and stem internodes than did hayed plants. The relationship between FR/R ratio and stem numbers for all treatments was consistent with previous reports that stem numbers of grasses may be influenced by the FR/R ratio at the crown. The decline in stem numbers of ungrazed stands suggests that to maintain vigorous stands of these species requires an appropriate level of management.
Light Intensity Effects on Meadowfoam Growth and Flowering
Authors: Seddigh Majid , Jolliff Gary D.
Published: July 2010

Date of flowering influences meadowfoam (Limnanthes alba Hartweg ex Bentham) adaptation, economic yield, and management. The objective of this experiment was to determine the effects of photosynthetic photon fluxes (PPF) before and after photoperiodic floral induction (PFI) on meadowfoam growth and flowering. ‘Mermaid’ growth and flowering responses to PPF of 150, 300, 450, 600, 750, and 900 μmol m−2 s−1 were investigated in a controlled environment. Treatments were initiated either 24 d before or at PFI. Increasing PPF, both before and at PFI, reduced days to first flower, flowering duration, total flowers produced per plant, flowers with bad stamens, and plant height and dry weight at maturity. More flowers were produced when PPF treatments were initiated 24 d before PFI compared with those initiated at PFI. Light intensities <450 μmol m−2 s−1 after PFI appeared to result in slow stem growth, increased potential number of flowering stems and flowers, and an exponential delay in flowering. Conversely, PPF >600 μmol m−2 s−1 after PFI enhanced flowering and maturity, and decreased plant size, flower number, and duration of flowering. After PFI, 450 to 600 μmol m−2 s−1 PPF appeared optimum for a balance of flower production and plant growth in controlled environments. Higher PPF before PFI, however, may increase the potential number of flowering stems and flowers, but it did not substitute for long daylength required for floral induction. Results suggest that in western Oregon low light intensity during fall and winter months may contribute to excessive vegetative growth of Mermaid meadowfoam at the expense of seed production.
Pedigree Selection for Improved Partial Resistance to Common Leaf Rust in Sweet Corn
Authors: Gingera G. R. , Davis D. W. , Groth J. V.
Published: July 2010

Common leaf rust (Puccinia sorghi Schw.) of maize (Zea mays L.) can produce large yield losses in commercial sweet corn fields planted to susceptible hybrids. Greater levels of partial resistance could reduce the need for protective fungicides to control rust epidemics. Our objective was to determine whether pedigree selection was effective in improving partial resistance to common leaf rust. Three sugary (su sweet corn breeding populations were inbred to the F5 with selection for rust resistance in each generation. Plants grown from remnant seed from the F2 to F5 were examined in four field environments for disease severity at five weekly periods beginning one week before anthesis until anthesis + 21 d under artificial disease epidemics. before anthesis until anthesis + 21 under artificial disease epidemics. The F5 lines from each of the three populations developed 27, 19, and 49% lower mean disease severity than the original F2 populations three weeks after anthesis. There were significant correlations (r2 = 0.77‐0.95) between ratings of mean disease ratings for any two of the five sample periods. There was also a significant correlation (r2 = 0.72‐0.91) between mean disease severity and ratings derived rom the worst leaf in the plot over five disease sampling periods.
Inheritance of Greenbug Biotype G Resistance in Wheat
Authors: Porter D. R. , Webster J. A. , Friebe B.
Published: July 2010

Resistance to greenbug [Schizaphis graminum (Rondani)] Biotype G (GBG) has recently been identified in wheat (Triticum aestivum L.). Prior to this discovery, five sources of resistance to greenbug Biotypes B, C, and E were documented. Resistance in these five sources is controlled by five different genes (gbl, Gb2, Gb3, Gb4, and Gb5). The objectives of this study were to characterize the virulence of Biotypes G and H on sources of greenbug resistance in wheat, determine the inheritance of GBG resistance in GRS 1201 (a GBG‐resistant winter wheat), and determine whether the GBG resistance gene is different from other reported resistance genes. A combination of bioassays and previously reported data was used to characterize and summarize the virulence patterns of Biotypes B, C, E, F, G, H, and I on all known sources of greenbug resistance in wheat. ‘Largo’ (Gb3) was the only germplasm resistant to Biotype H. Largo, CI 17959, and GRS 1201 were resistant to Biotype I. GRS 1201 was the only germplasm resistant to Biotype G. Segregation ratios of GBG resistance ratings of an F2 population from a cross between GRS 1201 and ‘Tavern’ (GBG‐susceptible spring wheat) were analyzed to determine inheritance. GBG resistance in GRS 1201 is inherited as a single dominant gene, which is different from previously reported resistance genes. C‐banding analysis identified GRS 1201 as being a 1AL.1RS wheat‐rye translocation line. The C‐banding of the 1RS arm in GRS 1201 is identical to the 1RS arm present in ‘Amigo’ (Gb2). The gene symbol Gb6 has been assigned to the greenbug resistance gene in GRS 1201.
Maize Responses to a Severe Isolate of Maize Chlorotic Dwarf Virus
Authors: Pratt Richard C. , Anderson Robert J. , Louie Raymond , McMullen Michael D. , Knoke John K.
Published: July 2010

The results of incidence ratings to assess the host response of maize (Zea mays L.) to natural infection, or to controlled inoculation in either the field or the greenhouse, with maize chlorotic dwarf virus (MCDV) appear inconsistent for identification of resistant or tolerant responses. Our objective was to determine whether assessment of the severity of three symptoms on the leaves (veinbanding, chlorosis, and twisting of the leaf and tearing of the leaf margin) would consistently allow differentiation of the host responses of maize inbreds and hybrids to inoculation with two isolates of MCDV. Symptom severity was assessed using a 1 to 5 visual rating for each of the three symptoms at three to four time intervals after controlled inoculation with a severe isolate of MCDV in both greenhouse and field experiments. Analysis of the symptom severity assessments grouped genotypes into similar host response categories in both environments. Incidence ratings of genotypes in greenhouse studies were not significantly different, and field incidence ratings were inconsistent. Height reduction in greenhouse‐grown plants was most severe in genotypes with high levels of expression of the other symptoms but was of limited value in differentiating genotypic groups. Comparison of the average symptom severity assessments using the severe and type isolates indicated that symptom expression in field‐grown plants was more severe when inoculated with the severe isolate of MCDV. Regardless of virus isolate, symptoms of plants grown in the field were not as severe as those on plants grown in the greenhouse. A reduction in symptom severity was associated with hybrid vigor of field‐grown plants. In one field study, the level of symptom severity was correlated with both yield and plant height reduction of hybrids.
Frequency of Natural Out‐Crossing in Partially Cleistogamous Pigeonpea Lines in Diverse Environments
Authors: Saxena K. B. , Jayasekera S. J. B. A. , Ariyaratne H. P. , Ariyanayagam R. P. , Fonseka H. H. D.
Published: July 2010

Natural out‐crossing is the major cause of loss of varietal purity in pegeonpea [Cajanus cajan (L.) Millsp.]. The frequency of natural out‐crossing of partially cleistogamous mutant lines, characterized by a modified keel and filamentous anthers, was studied at two locations in Sri Lanka and three locations in India. Indeterminate growth habit and normal floral morphology were used as dominant markers and the frequency of anural out‐crossing was estimated as percentage of the observed hybrid plants. Natural out‐crossing in the mutant lines in Sri Lanka ranged from 0.14 to 1.33% in comparison to 6.34 to 19.64% in the controls. In the Indian environments, natural outcrossing ranged from 0.16 to 2.67%. The mutant was higly stable over diverse environments, and may be of considerable economic importance in pigeonpea improvement and seed‐production programs.
Silicon Concentration, Disease Response, and Yield Components of Rice Genotypes Grown on Flooded Organic Histosols
Authors: Deren C. W. , Datnoff L. E. , Snyder G. H. , Martin F. G.
Published: July 2010

On silicon‐deficient soils, fertilization with silicon (Si) has reduced disease severity and increased yield of rice (Oryza saliva L.). Breeding rice genotypes with greater Si concentration has been proposed, and some African and Asian rices have been evaluated for variability of Si concentration on upland and flooded mineral soils. This experiment investigated the variability and relation of Si concentration in rice plant tissue with disease severity and yield components of selected U.S. rice genotypes grown on flooded organic soils. Ten rice genotypes were grown at two Florida locations on Si‐deficient organic Histosols. Plots were replicated five times in each of two Si treatments: Siamended soil with silicon added at 2 Mg ha‐1, and an unamended control. Plots were rated for disease severity at growth stage 8 to 9 (dough to mature) and sampled for determination of Si concentration in plant tissue (leaves and straw). Genotypes differed for Si concentration and disease severity at each location and for each Si treatment. Among genotypes, disease severity was negatively correlated with Si concentration in plant tissue. Increases in yield with added Si were attributable to a greater number of grains per panicle, whereas weight per 100 seed and panicles per square meter exhibited less change. Results indicated that although Si concentration varies among genotypes and is negatively correlated with disease severity, the strength of this association is mitigated by other genotypic factors which also affect response to disease.
Plant Spacing, Density, and Yield of Wheat Subjected to Postanthesis Water Deficits
Authors: Turner Neil C. , Prasertsak Praphan , Setter Timothy L.
Published: July 2010

The optimum planting density for Gutha wheat (Triticum aestivum L. emend. Thell.) grown in mediterranean‐type environments varies with site and season. This study investigated the influence of postanthesis water deficits on the water relations and yield of wheat sown at different plant densities with even and uneven plant densities along the row. Unevenness of machine planting resulted in a yield reduction of 20% compared with evenly spaced plants in plants subjected to postanthesis water deficits, but no yield reduction was observed in irrigated wheat. Wheat at high densities (100 and 200 plants m‐2) developed lower leaf and ear water potentials than plants at low densities (25 and 50 plants m‐2) during postanthesis water deficits. The greater deficits, however, did not reduce yields. Grain yields were generally lower at densities of 25 and 50 plants per square meter than at 200 plants per square meter when postanthesis water deficits developed, but not when irrigated. The later‐formed tillers (Tillers 2, 3 and 4), which were only produced at low densities, had smaller thousand‐grain weights compared to those of the mainstem and the first tiller when water deficits were induced during the postanthesis period. The delay in anthesis in the later‐formed tillers was up to 20 d and this resulted in grain fill occurring at low leaf and ear water potentials. We conclude that reducing the density of palnts to reduce water use may decrease rather than increase wheat yield under water limited conditions.
Complementary Gene Interactions in Alfalfa are Greater in Autotetraploids than Diploids
Authors: Bingham E. T. , Groose R. W. , Woodfield D. R. , Kidwell K. K.
Published: July 2010

Greater complementary gene interaction in autotetraploid alfalfa (Medicago sativa L., 2n = 4x = 32) may explain differences in vigor and breeding behavior between diploids and autotetraploids. Complementary gene interaction is nonallelic gene interaction or epistasis where dominant alleles at heterozygous loci may complement each other by masking recessive alleles at respective loci. This paper describes how tetrasomic segregations of linkage blocks in linkage disequilibrium produce tetraploid individuals and populations with greater complementary gene interaction than is possible at the diploid level. This finding helps explain autotetraploid superiority and unique breeding behavior. Research on gene action in autotetraploid alfalfa has demonstrated that favorable alleles in linkage blocks underpin population improvement and increased heterosis. The individual favorable alleles with additive effects also contribute to non‐additive complementary gene interactions in linkage blocks. Apparent multiple allelic interaction (overdominance) effects discussed in earlier studies inbreeding depression and progressive heterosis in alfalfa are due mainly to linkage disequilibrium, which agrees with findings in maize. The severe inbreeding depression in autotetraploids is due mainly to the rapid loss of complementary gene interactions in the first few generations of inbreeding. Correspondingly, the progressive heterosis of autotetraploids is due mainly to a progressive increase in complementary gene interactions. Greater complementary gene interactions in tetraploid alfalfa also helps explain recent DNA research indicating that yield in tetraploids is more responsive to genetic diversity than in diploids. Many differences between diploid and autotetraploid alfalfa reported in earlier studies now may be explained by inherent differences in the levels of complementary gene interactions.
Grain Filling Parameters and Protein Content in Selected Winter Wheat Populations: II. Associations
Authors: Mou Beiquan , Kronstad Warren E. , Saulescu N. N.
Published: July 2010

Understanding the relationship between grain filling (GF) characteristics, earliness, and N accumulation would aid in improving grain size and grain protein content in wheat (Triticum aestivum L.). significant association of early anthesis, long GF duration, low GF rate, and high protein concentration was found in a set of F1 hybrids and their parents from a 4 × 4 diallel cross involving Chinese and U.S. cultivars. This association was also found in an F2 population of a cross between an early hard red winter Chinese wheat and a late soft white winter U.S. cultivar. Expressing GF duration and rate on a temperature basis (degree days) removed the correlation between anthesis date and GF parameters and showed that the early parent with a longer GF duration in days actually required less degree days for GF than did the late‐heading parent. Regardless of the way of expressing GF parameters, a significant negative correlation was found between rate and duration of GF, suggesting a physiological barrier in combining high values for both traits. Kernel weight was significantly correlated with GF rate but not with GF duration, opening the possibility of breeding early maturing cnitivars with reduced GF period without sacrificing grain weight. Grain protein concentration was negatively correlated with GF rate and positively correlated with GF duration, regardless if GF parameters were expressed on a time or temperature basis. These results suggest that improvements in both grain size and grain protein concentration will be difficult but not impossible and that selecting for long GF duration might be beneficial in this respect. Expressing GF parameters on a temperature basis proved useful in removing the differential influence of temperature variation on plants of different earliness.
Identification of Quantitative Trait Loci Using a Small Sample of Topcrossed and F4 Progeny from Maize
Authors: Beavis W. D. , Smith O. S. , Grant D. , Fincher R.
Published: July 2010

Plant breeders have an interest in the identification of genomic regions associated with the expression of quantitative traits because they recognize that such information could be used to improve realized heritability and reduce time per cycle of selection. The development of molecular marker technologies may provide tools to accomplish these goals. Maize (Zea mays L.) breeders develop new inbred parents of hybrids through top‐crossed and per se evaluation of numerous quantitative traits in segregating progeny from planned breeding crosses. This study was conducted to determine if regions of the genome associated with variability of agronomicaily important traits could be identified by a small, but typical, sample of top‐crossed and F2:4 progeny from the cross B73×MO17. We identified genomic regions in 24 agronomic traits, using interval mapping and simultaneous estimation of multiple quantitative trait locus models. The estimated numbers of quantitative trait loci (QTL) identified per trait were about three five. Many of the identified QTL were the same for correlated traits. Interestingly, yield QTL were not in the same regions previously reported for B73×MO17. This comparison contains a number of potential confounding factors: source of parental inbreds, type of progeny, different genotype × environment interaction effects, and different small samples of progeny from the cross. Consideration of these factors and the power of the tests to identify QTL suggests that the sampling of progeny is the most likely explanation for the differences.
Effect of Awn Suppression on Grain Yield and Agronomic Traits in Hard Red Winter Wheat
Authors: Weyhrich Roger A. , Carver Brett F. , Smith Edward L.
Published: July 2010

Producers in the southern Great Plains who utilize wheat for grain, hay, or late‐season grazing would benefit from awnless hard red winter (HRW) wheat cultivars if yield potential is maintained relative to awned cultivars. The influence of awn suppression in contemporary cultivars in the southern Great Plains is unknown. Our objective was to determine the genetic effect of awn suppression on grain yield and agronomic traits measured in several HRW backgrounds and Oklahoma production environments. Experimental materials were derived by two methods from the same source populations: ‘TAM 107’*2/‘McNair 1003’, ‘Mustang’*2/McNair 1003, and ‘Century’*2/ McNair 1003. Bulk populations of lines were derived randomly from either homozygous awned or awnletted (spikes with one to three tip awns) F2 plants in each cross. The six bulk populations were evaluated in 11 environments. In a separate experiment, 78 pairs of awned and awnletted F3‐derived sib lines (26 pairs per cross) were evaluated in four environments. No differences in grain yield were detected between awned and awnletted bulk populations from Mustang or Century, but a significant decrease in yield was found for the awnletted TAM 107 population. Significant decreases in test weight were associated with the awnletted character in all backgrounds. The Century‐awnletted population had longer spikes, greater spike harvest index, and more kernels per spike than the Century‐awned bulk. In 69% of the sib‐pair comparisons, the awnletted sib did not differ significantly from the awned sib in grain yield. Where significant differences occurred, the awned sib was always higher yielding. It may be possible to develop awnletted lines with acceptable yield performance in the Great Plains, but close attention must be given to test weight to maintain current expectations of awned cultivars.
Germination and Early Seedling Development under Low Temperature in Canola
Authors: Nykiforuk Cory L. , Johnson‐Flanagan Anne M.
Published: July 2010

Canola is seeded when ambient temperatures are below the optimum. Therefore, we wished to determine whether certified seedlots displayed variation in low temperature germination potential and, thereafter, to study the effects of low temperature during germination and early seedling development. Canola (Brassiea napus L. cv. Westar) seed was tested for germination potential at 22, 10, 6, and 2 °C. Two seedlots, designated L and H, which represented the extremes in germination potential at 10 °C, were chosen for further study. Under the optimal conditions of 22 °C the two seedlots exhibited similar germination rates and early seedling growth. At 10 °C, L reached 95% germination within 8 d and displayed rapid seedling growth. This was associated with high isocitrate lyase activities and rapid mobilization of total lipid and protein reserves. Seedlot H, at 10 °C, did not reach a high percentage of germination until Day 12, and seedling growth was slow relative to that of L. Seedlot H had more gradual increases in isocitrate lyase activity, mobidization of storage lipid, and protein mobilization at 10 °C. Both seedlots germinated poorly at 6 and 2 °C. At 6 °C, L displayed higher isocitrate lyase activity and higher rates of lipid and protein mobilization than H. From these studies we have determined that low temperature has a deleterious effect on the germination of canola and this may be reflected in a loss or a delay of coordination in the mobilization of reserves. In addition, differences within the Westar cultivar exist with respect to germination under low temperature.
Effects of T2BS.2RL Wheat‐Rye Translocation on Breadmaking Quality in Wheat
Authors: Knackstedt M. A. , Sears R. G. , Rogers D. E. , Lookhart G. L.
Published: July 2010

Detrimental effects on hard wheat (Triticum aestivum L.) bread baking quality have been shown in previous studies on wheat‐rye translocations involving chromosome Group 1. A new wheat‐rye translation (T2BS.2RL, Hamlet), which contains a single dominant gene (H21) for Hessian fly [Mayetiòla destrúctor (Say)] resistance, should not affect wheat storage proteins found in chromosome Groups 1 and 6. The objective of this study was to determine if the T2BS.2RL translocation modifies milling and baking properties. Backcross4F4‐derived lines were grown in 1991 near Manhattan and Hutchinson, KS, in replicated plots. Grain from the 5 translocation lines and 11 nontranslocation lines were compared for several breadmaking quality traits. Test weight, flour yield, and kernel hardness were reduced in the translocation lines but could be overcome by selection. Mixograph‐mixing time and bake‐mixing time also were reduced, but the small differences would not adversely affect breadmaking quality. No significant differences were found for flour protein, mixograph mixing tolerance, loaf volume, and crumb grain score. However, statistically significant small improvements were found for flour color and water absorption. Overall, the translocation did not have a large effect (either positive or negative) on milling or baking quality.
Extracting Volatile Compounds from Single Plants using Supercritical Fluid Extraction
Authors: Henning John A. , Core Robert J. , Gardea‐Torresdey Jorge L.
Published: July 2010

Analysis of plant volatile compounds typically requires large amounts of plant tissue, thus preventing sampling from specific morphological regions of individual plants. We used supercritical fluid extraction (SFE), with CO2 as the solvent, to extract plant volatiles from 1.5 g of fresh alfalfa germplasm tissue (Medicago sativa L. and M. glandulosa David). More than 100 volatile and semi‐volatile compounds were detected by gas chromatography‐mass spectrometry (GS‐MS); most of the these (>80) were in sufficient quantity for accurate spectral analysis. SFE is an efficient microextraction technique for volatile compounds contained within single plants.
Genetics of Heat Tolerance during Reproductive Development in Common Bean
Authors: Shonnard Gisela C. , Gepts P.
Published: July 2010

Common bean (Phaseolus vulgaris L.) is grown in regions where high temperatures during reproductive development reduce yields. The purpose of this study was to identify sensitive growth stages during reproductive development and to investigate the genetics of heat tolerance during these stages. Exposure to high temperatures during two reproductive growth stages, namely flower bud formation and pod filling, resulted in particularly severe damage. This damage was evaluated by scoring two corresponding traits‐flower bud abortion and reduced pod fill. For each trait, two tolerant and two susceptible large‐seeded dry bean genotypes were chosen and crossed in all combinations, including reciprocals. The parents and control cultivars were evaluated under heat stress conditions at two locations in the Central Valley of California; this allowed us to determine that genotype × environment interactions were present for both traits. Genetic studies included parents, F1 and F2 progenies, and control cultivars at one of the above locations. Both traits displayed continuous variation, indicating quantitative inheritance. Generation means analyses demonstrated that additive genetic effects were significant for both heat tolerance traits, but were more important for tolerance to bud abortion. Significant dominance effects for tolerance to bud abortion were attributed to either linkage or pleiotropy of the single dominant gene conferring indeterminate growth habit. Both generation means and diallel analyses demonstrated the presence of cytoplasmic effects including interactions of cytoplasmic with nuclear genes. The significant additive effects observed indicate that gain from selection for improved heat tolerance should be possible for both traits.
Genetic Aspects of Starch Granule Traits in Barley
Authors: Oliveira A. B. , Rasmusson D. C. , Fulcher R. G.
Published: July 2010

Starch, the main constituent of barley (Hordeum vulgare L.) kernels, is accumulated as granules classified as large, Type A, and small, Type B. The objectives of this research were to assess the importance of genotype and environment in determining starch granule morphology, to estimate heritability for these traits, and to investigate the association between granule traits and malting quality. Fourteen genetically diverse barley genotypes were evaluated in four environments, and four populations were evaluated in a parent‐offspring study. Data were obtained using digital image analysis of starch granules. Significant differences were found among the 14 barley genotypes for five of six granule traits. Environment had a significant effect on four granule traits, but genotype by environment interactions were not significant. Type‐A granules accounted for 94% of total starch by volume, with a range of 92 to 96% for the 14 genotypes. Genotype means for A granule volume ranged from 1720 to 2164 μm3 and for surface area, from 773 to 944 μm2. On the number basis, the small B granules accounted for 93% of all granules in the 14 genotype set. Malting and six‐row genotypes had larger A‐granule surface area and volume than feed and two‐row types, although some overlapping of genotypes occurred. There was little evidence of association between starch granule morphology traits and malting quality traits. Heritabilities were encouraging on a genotype mean basis in the 14 genotype study, but were low in the parent‐offspring heritability evaluation. It appears that greater genetic variability in granule traits is needed before considering selection for starch granule traits to improve grain quality.
Genes for Short Stature in Barley
Authors: Mickelson Harold R. , Rasmusson Donald C.
Published: July 2010

Inheritance of height in barley (Hordeum vulgare L.) was studied with the objective of finding genes for short stature and understanding height inheritance. Segregation for height was visually classified in F3 populations derived from crosses of 11 short‐stature genotypes to two testers, tall cultivar Robust and M62 (a Minnesota semidwarf line containing the ‘Jotun’ derived sdw gene). Populations were classified in the field from 1987 to 1991. Height in the short‐stature genotypes was hypothesized to be controlled by one, two, or three recessive genes. The seven genotypes which have only one short‐stature gene, ‘Diamant’ (‘Triumph’ and ‘Cheri’), ‘Gus’, ‘Kombar’, NK41558, and SMAI6W41428, appear to contain sdw or an alternative allele at that locus. We hypothesize that two genotypes, E295 and ‘Poco’, contain one short‐stature gene in addition to the sdw gene, and that Apam Dwarf contains two short‐stature genes as well as sdw. ‘UC476’, the only short‐stature genotype in this study that appears not to contain sdw, likely has two other short‐stature genes. Heights of the parents and F2.3 progenies fell roughly into four classes, which we hypothesized corresponded to genotypes with no, one, two, or three recessive shortstature genes. Height differences in all populations and among the parents indicated that modifying genes play an important role in determining height. This study revealed that the sdw gene is wide‐spread, occurring in 10 of the 11 short‐stature genotypes. Putative new genes for short‐stature were found in E295, UC476, Poco, and Apam Dwarf.
Inheritance of Rust Resistance in a Source of MC29 Sunflower Germplasm
Authors: Lambrides C. J. , Miller J. F.
Published: July 2010

Sunflower rust, incited by Puccinia helianthi Schw., is a significant disease problem in sunflower (Helianthus annuus L.) production areas of North America, Argentina, and Australia and has been identified on sunflower grown in all regions of the world. Five races of rust presently have been identified in the USA. Recently, a new rust isolate gave a previously unreported virulence reaction pattern and was designated North American Race 6. A genetic study was conducted to determine the inheritance of resistance to Race 6 found in MC29 (AUS), a germplasm line introduced from Australia. F1, F2, and testcross progeny were produced from two crosses following hand pollinations: HA89/MC29 (AUS) and MC29 (AUS)/MC69. A multiple race inoculation technique was utilized under greenhouse conditions to evaluate the resistance or susceptibility of each plant to North American Races 1, 3, and 6. Chi‐square tests for goodness of fit and heterogeneity were utilized to test each F2 and testcross family. A single, dominant gene in MC29 (AUS) was found to confer resistance to North American Races 1, 3, and 6. The gene was independent and nonallelic to the genes R1 and R2, and was designated R10. Identification of resistance to Race 6 has increased the genetic diversity of resistance to sunflower rust in North America.
Phenology of Sorghum Flowering
Authors: Pendleton Bonnie B. , Teetes George L. , Peterson Gary C.
Published: July 2010

Understanding the phenology of flowering, the time when sorghum, Sorghum bicolor (L.) Moench, is vulnerable to oviposition by the sorghum midge, Contarinia sorghicola (Coquillett), would improve the capability of managing this key sorghum insect pest and aid in developing control recommendations. Daily number of flowering spikelets per individual panicle of ‘DeKalb 50’, and per panicle in field populations of ‘WAC 715DR’, ‘Funk 522DR’, and ‘DeKalb 59E’ sorghum, were calculated from measurements of centimeters of panicle in flower. The rate of flowering of individual panicles of sorghum increased from Days 1 to 3 and then declined, with each panicle completing flowering in approximately 8 d. The most spikelets (1300) per panicle flowered the third day after flowering began on a panicle. Panicles in a uniformly growing field were flowering approximately 13 d irrespective of hybrid, with most spikelets (388 per panicle) flowering the seventh day after flowering began in the field. Almost 48% of the variability in the number of spikelets per panicle was due to sorghum hybrid and length of panicle. Panicle length and number of spikelets were positively correlated, with 42% of the variability in the number of spikelets attributable to panicle length. Mean panicle length was 26.9 cm. Mean number of spikelets was 2725 per panicle. Accurate assessment of the flowering duration of sorghum is critical to understanding the relationship between sorghum midge abundance and sorghum grain loss.
Effect of Tiller Trimming on Phyllochron and Tillering Regulation during Tall Fescue Development
Authors: Skinner R. H. , Nelson C. J.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) seedlings grown in controlled‐environment chambers experience a rapid decrease in the rate of leaf and tiller appearance about 30 to 35 d after planting (DAP). A tiller‐trimming experiment was conducted to determine the cause of this decrease and to examine the interrelationship between leaf and tiller appearance and growth. Each primary tiller from three tall fescue populations differing in tillering capacity was trimmed 5 d following its appearance, then regrowth was removed twice weekly. Trimming tillers increased the number of tillers per plant by 29 to 134%. Plants with trimmed tillers had higher leaf appearance and elongation rates than controls after 30 to 37 DAP. Higher leaf appearance rates increased the potential number of tillers per plant by 185 to 273%. Tiller trimming did not affect the proportion of potential sites which produced tillers (site usage) in two of the three populations, but reduced site usage from 0.66 to 0.58 in the population with the highest tillering capacity. Increased tiller production was primarily due to increased production of potential tiller sites. Leaf appearance rate depended on duration of leaf tip elongation within the whorl, and on the timing of leaf initiation. Increasing the duration of leaf elongation increased the interval between initiation of successive leaves and decreased leaf appearance rate. The main stem was apparently able to support initiation of all tillers on the plant while maintaining high leaf elongation rates, suggesting that competition with main stem leaves was not limiting tiller appearance.
Identification of Glutenin Alleles in Wheat and Triticale Using PCR‐Generated DNA Markers
Authors: Smith Rex L. , Schweder M. E. , Barnett R. D.
Published: July 2010

Quality in wheat (Triticum aestivum L. em Thell.) is a very complex trait; however, the water insoluble gluten proteins are responsible for the elasticity and cohesiveness (strength) of dough and are important determinants of breadmaking quality. High molecular weight glutenin subunits encoded by genes on the long arms of Group 1 chromosomes have been associated with gluten strength, and a portion of the variability between cultivars can be attributed to glutenin subunit composition. Of the glutenins, Subunits 5 + 10 encoded by the D genome have been found to have the largest positive effect on dough strength, whereas the allelic Subunits 2 + 12 have a negative effect. Therefore, it has been important to incorporate the genes for the 5 + 10 subunits into bread wheats. There has been considerable interest in improving the dough strength and quality of soft wheats and triticale (X Triticosecale Whittm.) to use them in bread‐like products. Glutenin subunit screening is accomplished using electrophoresis (SDS‐PAGE). In this paper, we report the development of an alternative screening method based on the glutenin genes themselves, using the polymerase chain reaction (PCR). Primers designed from computer analyses were synthesized and tested on the cloned subunit 10 gene (Glu‐D1‐2b), 10 wheat cultivars of known subunit composition, and six triticales. Although the Glu‐D1‐2b (Dy10) and Glu‐D1‐2a (Dy12) genes have 98.9% DNA sequence similarity, marker fragments capable of consistently identifying those genotypes were amplified. Fragments correlating with glutenin subunit composition offering possibilities of extending the PCR screening system to other subunits were noted.
New Fertility Restoration Genes from Wild Sunflowers for Sunflower PET1 Male‐Sterile Cytoplasm
Authors: Seiler Gerald J. , Jan C. C.
Published: July 2010

Cultivated hybrid sunflower (Helianthus annuus L.) production depends on a single male‐sterile cytoplasm, PET1, derived from H. petiolaris Nutt. and a few fertility restoration genes. This study was conducted to locate new restoration genes for the PET1 cytoplasm from the wild species of the genus Helianthus. Ten wild species populations from the USA were grown in a field nursery and crossed with cytoplasmic male‐sterile inbred line cmsHA 89 to determine the presence and inheritance of restoration genes in wild annual and perennial species. Standard sunflower breeding techniques were used to obtain F1 and B1CF1 seed, whereas F2 seed was produced by sibbing F1 plants instead of selfing due to the low self‐compatibility. All H. annuus L., H. argophyllus T. & G., H. praecox ssp. runyonii Heiser, and H. tuberosus L. populations possessed dominant fertility restoration genes at high frequencies, varying from 57 to 100%. Segregation ratios of male‐fertile to male‐sterile plants in the BC1 (1:1) and F2 (3:1) generations of nine crosses suggested a single dominant gene for fertility restoration. Other segregation ratios suggested that three genes were involved in one cross of H. argophyllus and that fertility was restored when at least two dominant alleles were present at any of the three loci. The new sources of fertility restoration genes from wild sunflowers will be valuable for sunflower breeding and selection programs by providing additional genetic diversity.
Root and Shoot Growth of Wheat Genotypes in Response to Hypoxia and Subsequent Resumption of Aeration
Authors: Huang Bingru , Johnson Jerry W. , NeSmith D. Scott , Bridges David C.
Published: July 2010

Understanding plant responses to hypoxiand subsequent resumption of aeration is important for breeding tolerant genotypes. The growth response of six wheat genotypes (Triticum aestivum L.) to hypoxiand subsequent recovery was evaluated. Plants were grown for 14 and 21 d in nutrient solutions flushed with air (aerated control) or with a mixture of 02 and N2 (hypoxia) or hypoxia for 14 d followed by aeration for 7 d (recovery). Shoot and root growth was inhibited by hypoxia, with roots being more sensitive. Stomatal conductance (gs) was reduced beginning 5 to 7 d after hypoxia. The adverse effect of hypoxia was most severe for Bayles and FL302, intermediate for BR34 and Coker‐9766, and least for Gore and Savannah. Hypoxia enhanced formation of aerenchyma in roots, to a greater extent for Gore and Savannah. Aerenchyma became more conspicuous with duration of hypoxia. Seven days after resumption of aeration, shoot growth recovered completely for Gore and Savannah but only partially for Bayles, FL302, BR34, and Coker‐9766. The number and length of crown roots increased to the value of the controls for all genotypes, whereas seminal root length was restored only in Bayles, Gore, and Savannah. Stomatal conductance recovered within 5 d for Savannah and 10 d for Gore but never recovered for Bayles, FL302, BR34, and Coker‐9766. Breeding for hypoxia tolerance could be facilitated by selecting genotypes that develop more crown roots and more aerenchyma in those roots, maintain stomatal opening under hypoxic conditions, and resume seminal root growth and opening of stomatafter termination of hypoxia.