bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid Performance and Combining Ability for Yield and Malt Quality in a Diallel Cross of Barley
Authors: Hockett E. A. , Cook A. F. , Khan M. A. , Martin J. M. , Jones B. L.
Published: July 2010

Breeders of autogamous crop species such as barley (Hordeum vulgate L.) have long been interested in developing F1 hybrids as an alternative to pure‐line cultivars in order to capitalize on the benefits of heterosis. Hybrid barley might have most commercial potential because its groin is used in the malting and brewing industry where it commands a premium price. In addition to increased grain yield, hybrids might provide an added benefit in heterosis for malting traits. Our objective was to investigate heterosis and combining ability for malting and brewing traits in a sample of barley cultivars chosen to represent a range in malting and brewing quality. Barley cultivars Harrington, Klages, Menuet, Morex, and Piroline were intercrossed in diallel fashion to produce the 10 possible F1 hybrids. Reciprocals were produced except for Klages. Morex is six‐rowed, and the other four are two‐rowed cultivars. All but Menuet are or have been accepted malting cultivars in the USA. Parents plus the F1 were evaluated in hill plots in 2 yr and parents plus F2 bulks were evaluated in row plots in 1 yr at Bozeman, MT. Physical and chemical malting characteristics were measured on all groin samples. Analyses were performed to determine importance of heterosis and general combining ability (GCA) and specific combining ability (SCA) effects for yield and malting characteristics. The GCA effects were important for all traits in both years of the F1 trial and the F2 bulk trial, while SCA effects were important for malt protein and wort protein concentrations in both years of the Ft trial and for grain yield, kernel weight, and percent plump kernels in the F2 trial. Reciprocal differences were generolly not important; they accounted for a significant portion of the variation among cross means only for diastatic power in both of the F2 trials. Average heterosis (F1 mean minus mean of parents) was detected for grain yield, kernel weight, percent plump kernels, wort protein, and wort/malt protein ratio in both F1 trials. The heterosis for wort protein and protein ratio is undesirable for commercial use. Greatest heterosis for yield occurred between unrelated two‐rowed parents, but F1s with best malting quality were obtained from crosses of closely related parents with high malt quality.
In Vitro Nitrate Reductase Activity of Laboratory‐Grown Seedlings as an Indirect Selection Criterion for Maize
Authors: Feil Boy , Thiraporn Rachain , Stamp Peter
Published: July 2010

This study examines whether the predictive value of in vitro nitrate reductase (NR) activity of laboratory‐grown seedlings for grain yield, biomass yield, and N‐related traits (N uptake, grain N yield, grain N concentration, N harvest index) of field‐grown maize cultivars can be improved by changing the screening conditions. Seedlings of 12 tropical and 12 European cultivars were grown in growth cabinets under two temperature regimes (14 and 30 °C) and three levels of N supply (0, 0.128, and 0.384 g N kg−1 substrate, applied as NH4NO3) until the third leaf of 50% of the plants was fully expanded. The second leaf was assayed for in vitro NR activity and nitrate concentration. There were significant (P < 0.05) temperature × origin of eul tivar int eractions for both traits. At 14 °C, tropical cultivars had higher NR activity and lower nitrate concentration than the European cultivars, whereas at 30 °C, the situation was reversed. Field experiments were conducted with the tropical cultivars in Thailand and with the European cultivars in Austria and Germany. The NR activities of seedlings grown at 30 °C in the growth cabinet and grain yield of plants grown in the field in Thailand and Austria were correlated at r < +0.72 (P < 0.01) and +0.23, respectively. For plants harvested silage maturity in Germany, the correlation between NR activity and biomass was r < + 0.73 (P < 0.01). The correlations between seedling NR activity and N uptake were r = + 0.66 (P < 0.05), + 0.56 (P < 0.10), and +0.83 (P = 0.01) for Thailand, Austria and Germany, respectively. These results indicate that selection among laboratory grown seedlings for NR activity might accelerate progress in breeding for grain yield and acquisition of N.
Gas Exchange Differences and Comparative Anatomy among Cotton Leaf‐type Isolines
Authors: Pettigrew W. T. , Heitholt J. J. , Vaughn K. C.
Published: July 2010

Photosynthesis rate could be a selection criterion for plant breeders, especially if lines with superior photosynthesis could be identified and coupled with those lines with suitable partitioning of photosynthate between reproductive and vegetative growth. Establishing why certain lines may differ in photosynthetic rate could provide additional tools for selection. Photosynthesis and leaf anatomy of the youngest fully expanded leaf in field plots of the super okra, okra, and normal leaftype isolines of the cotton (Gossypium hirsutum L.) genotype ‘MD 65− 11’, which differ in leaf size and degree of Iobing, were compared with the normal leaf genotype ‘DPL 50’. Super okra and okra averaged 24 and 22% greater leaf CO2‐exchange rates (CER), respectively, than the normal leaf isoline in both 1989 and 1990. These differences were associated primarily with greater specific leaf weight (SLW) and leaf chlorophyll concentration of the super okra and okra leaf types. Water use efficiency [WUEg = CER/leaf stomatal conductance (gs)] was and 40% greater for super okra and okra, respectively, during 1990 compared to normal leaf. Leaves of the super okra and okra isolines were 42% thicker than normal leaf which contributed to this greater SLW. The relative tissue percentage of various cell types and mesophyil surface area per unit leaf volume did not differ among genotypes. Rubisco concentrations per unit stroma area were similar among chloroplasts of the different genotypes. Genotypic differences in CER are likely due to a greater concentration of photosynthetic apparatus per unit leaf area caused by leaf thickness differences, however the possibility of differences in the rate of dark respiration or photores piration cannot be discounted.
Sowing Date and Cutting Frequency Effects on Triticale Forage and Grain Production
Authors: Ramos J. M. , GarcÍa del Moral M. B. , Marinetto J. , GarcÍa del Moral L. F.
Published: July 2010

Cereal production for both forage and grain is strongly influenced by environmental conditions, sowing date, and the frequency, as well as the growth stage(s) at which forage cuttings are made. To determine optimum sowing dates for, and cutting effects on, forage and grain production in a Mediterranean environment, triticale (× Triticosecale W., cv. Trujillo) was grown in 1989 and 1990 at two rainfed sites and one irrigated site in southern Spain. The best balance for forage and grain production in this environment was achieved by sowing during the last week of November or first week of December. Sowing before or after this period decreased forage yield by 22 to 44%, grain yield by 12 to 60%, and total useable biomass (i.e., forage + grain) by to 52%. The highest grain yield was obtained where forage was not cut. One cutting reduced grain yield by 26 to 60% at rainfed sites and by 18 to 20% with irrigation. Two cuttings reduced grain yield by 35 to 48% and by 45 to 70% with and without irrigation, respectively, but increased forage yield by 76% with, or 31 and 96% without irrigation. For a Mediterranean environment, these results demonstrate good forage and grain yields with irrigation or where moderate (~400 mm) rainfall is received during the growing season. Cutting triticale for forage does not appear to be advisable in areas with very low seasonal rainfall.
Lipoxygense Activity and C6‐Aldehyde Formation in Comparison to Germination and Vigor during Soybean Seed Development
Authors: Trawatha S. E. , TeKrony D. M. , Hildebrand D. F.
Published: July 2010

Developmental changes in lipoxygenase (LOX) activity have been observed during embryo maturation, which suggests that the LOX pathway may be involved in seed development. A study was designed to measure changes in LOX activity and C6‐aldehyde (hexanal and hexenal) formation during seed development and relate these changes to the attainment of maximum germination and vigor. Field grown soybean [Glycine max L. (Merr.) cv. Century] seeds were sampled at regular intervals starting at 31 d after flowering and continuing until maximum dry seed weight [physiological maturity (PM)] in 1990 and 1991. Axes and cotyledons from freshly harvested seeds were evaluated for LOX activity and C6‐aldehyde formation. The remaining seeds were air dried and tested for germination and vigor. Maximum germination occurred at 46 and 43 d after flowering in 1990 and 1991, respectively. Maximum vigor, as measured by accelerated aging, occurred at 54 and 48 d after flowering in 1990 and 1991, respectively, which was 18 d before PM. During seed development, maximum LOX activity occurred in both the axes and cotyledons during the linear phase of seed growth, but declined before PM. In the axes and cotyledons, maximum hexanal and trans‐2‐hexenal formation occurred at approximately 30% of final dry weight, which was before maximum LOX activity, except for axes in 1990. Maximum hexenal and hexenal formation coincided with the first maximum expression of germination, while maximum vigor was more closely related to maximum LOX activity in the axes (1991) and cotyledons. Maximum expression of seed quality (germination and vigor) and maximum LOX and C6‐aldehyde formation were correlated during soybean seed development.
Agronomic Evaluations of Maize Genotypes Selected for Extreme Fiber Concentrations
Authors: Wolf D. P. , Coors J. G. , Albrecht K. A. , Undersander D. J. , Carter P. R.
Published: July 2010

Maize (Zea mays L.) hybrids with good yields of grain and wholeplant dry matter are recommended for silage production. The stover can comprise more than 50% of the whole‐plant dry matter and, therefore, can influence dry matter yield and nutritive value of the whole plant. The objective of this study was to determine relationships between agronomic characteristics (stover and whole‐plant forage yield and moisture, grain yield and moisture, lodging, maturity, and ear percentage) and nutritional quality of maize forage in three populations. Twenty‐four S0.1 families (S0‐derived families in S1) exhibiting a range in neutral detergent fiber (NDF) and lignin at mid‐flower, were testcrossed to two commercial inbred lines (FR23 and LH74) to form two groups of F1 hybrids. A third experimental group was created by self‐pollinating the S0.1 families to form S0.2 families. This germplasm was evaluated at three environments in Wisconsin. for FR23 testcrosses, grain yield had a correlation coefficient of 0.53 with stover dry matter yield, 0.65 with whole‐plant dry matter yield, and −0.03 with whole‐plant in vitro true digestibility. For LH74 testcrosses, the similar correlation coefficients were 0.46, 0.54, and −0.02, respectively. Also for FR23 testcrosses correlation coefficients of stover yield with whole‐plant yield, NDF, and in vitro true digestibility were 0.89, 0.53, and −0.28, respectively. For LH74 testcrosses the coefficients were, 0.85, 0.40, and −0.48, respectively. The results of this study demonstrate that stover yield and nutritional quality are important factors influencing whole‐plant yield and nutritional quality of maize forage.
Assessment of Genetic Variation in Avena sterilis using Morphologicall Traits, Isozymes, and RFLPs
Authors: Beer S. C. , Goffreda J. , Phillips T. D. , Murphy J. P. , Sorrells M. E.
Published: July 2010

Genetic patterns revealed by proximity coefficients may be affected by choice of traits, method of scoring, any subsequent transformations of scores, and choice of proximity coefficient. Our objective was to compare restriction fragment length polymorphism (RFLP), isozyme polymorphism, and variation in qualitative and quantitative morphological traits in a geographically stratified set of 177 accessions of a hexaploid wild oat, Avena sterilis L. Jaccard similarity coefficients (SJ) and Russell and Rao similarity coefficients (SRR) were calculated for all pairs of genotypes from restriction fragments and, separately, from isozymes. Standard taxonomic (DSZ), Mahalanobis, and Goodman distances were calculated from 26 morphological trait scores. Clustering of mean DSZ values or mean SJ(RFLP) values between pairs of countries produced similar dendrograms while SRR(isozymes) values resulted in different subgroups. Rankings of within‐country diversity were similar for different types of traits but were unrelated to geographic proximity of provenances of the accessions. Proximity coefficients based on the same type of trait (either RFLP, isozyme, or morphology) were highly correlated (Mantel statistic) (0.6‐0.9),while correlations for proximities based on different types of traits were ≤0.35. Isozyme‐ and RFLP‐based proximities were poorly correlated, and both were poor predictors of morphological relationships with the highest correlation being −0.35 between SJ(RFLP) and DSZ. while broad patterns of variation revealed by different types of traits were similar in this sample of A. sterilis, differences in pairwise estimates of relationship were sufficiently great to question the exclusive use of one type of trait for sampling and management of plant germplasm collections.
Stomatal and Photosynthetic Adjustment to Water Deficit as the Expression of Heterosis in Sunflower
Authors: Mojayad Fahima , Planchon Claude
Published: July 2010

Photosynthetic adjustment is a major mechanism of plant adaptation to drought. The objective was to determine the heterosis response to internal water deficit and to drought acclimation in sunflower (Helianthus annuus L.). Stomatal resistance, net photosynthesis, and water use efficiency were analyzed in relation to the leaf water potential reduction in acclimated and non‐acclimated plants for two F1 hybrids (Flamme and Viki) and their homozygous parent lines. The experiments were carried out in a controlled growth chamber on two series of plants previously acclimated or not acclimated to a 6‐d drought period with a water deficiency resulting in leaf water potentials of −2 MPa. The tolerance to internal water deficit in nonacclimated plants is a genotypic trait, but Stomatal and photosynthetic adjustment appeared as a heterosis response shown by delayed Stomatal closure from −1.50 to −1.91 MPa of the F1 hybrid Viki and from −1.52 to −1.95 MPa for the F1 hybrid Flamme. These F1 hybrids were also characterized after acclimation by higher net photosynthesis and water use efficiency over a wide range of leaf water potentials during the leaf water deficit. Thus, Stomatal adjustment appears to be closely associated with heterosis in sunflower which can develop a tolerance to internal water deficit in F1 hybrids; the tolerance is at least equal to that of the best homozygous lines. The parental line performance thus cannot provide decisive information on the F1 hybrid performance for this trait in breeding programs.
Control for Rate of Seed Development and Seed Yield Potential in Soybean
Authors: Hanson W. D. , Burton J. W.
Published: July 2010

Selecting for increased weight per seed among male‐sterile soybean plants [Glycine max (L.) Merr.] increased seed weight and seed yield for male‐fertile progeny but had minimal effects on seed number per ha. Assimilate availability to the seed during selection was essentially nonlimiting for an extended period, since male‐sterile plants have few seeds per plant. For the observed range, seed weight has shown no association with seed yield potential. This study tested two alternate hypotheses to explain the increased seed yield potential: (i) selection identified genotypes with increased seed sink activity per plant or (ii) selection identified genotypes with reduced seed maturation rates. Dry matter accumulation rate (DMAR) per unit seed dry weight, DMAR per unit seed coat area, and rate of increase in seed density were determined for greenhouse‐grown plants using a 7‐d period during mid‐seed development. The following observations led to the acceptance of the reduced seed maturation rate hypothesis: (i) When assimilates were made essentially nonlimiting to the seed by partial pod removal, selected and nonselected populations had similar DMAR per unit seed coat area and per unit seed dry weight, (ii) Selection for seed weight on male‐sterile plants reduced the rate of increase in seed density. (iii) DMAR per unit seed coat area did not increase with selection. Selected and nonselected populations, had similar DMAR per unit seed dry weight. Apparently, selection had occurred against the reduction in rate of dry matter uptake by the seed. This reduction is normally associated with reduced seed maturation rate. Selection for seed weight on male‐sterile plants can be completed during the early generations of a breeding program and used to identify genotypes that have longer seed‐filling durations and more efficient systems for assimilate utilization.
Severity of Phomopsis Seed Decay, Seed Quality Evaluation, and Field Performance of Soybean
Authors: Zorrilla Gonzalo , Knapp Allen D. , McGee Denis C.
Published: July 2010

The ability of seed quality tests to predict field performance of soybean seed lots with different incidences of infection by the causal agents of phomopsis seed decay (PD), was evaluated. Different seed infection levels were induced in one ‘Corsoy 79’ soybean seed lot by exposing naturally infected pods to 0, 3, 4, or 5 d at >95% relative humidity and 25 °C. Seeds were then removed from pods and dried. Seed quality wase valuated by germination tests on creped cellulose wadding (Kimpac), rolled towel, and sand and by cold, accelerated aging (A.Aging), tetrazolium (TZ), and conductivity tests. Field emergence of these seeds was evaluated at two locations and two 1991 planting dates in Iowa. Differences between laboratory germination test results for seeds with low (6.4 and 11.5%) infection levels were minor. At higher infection levels (18.2 and 32.4%), test differences were as large as 23%.P homopsis‐diaporthine fection was located primarilyin the seed coat with lesser infection levels in cotyledons. Cotyledonary infection was not associated with variation in test results, but seed coat infection was, as evidenced by greater numbers of infected‐abnormal seedlings in Kimpac and towel tests than in other tests. Field emergence declined with increasing PD seed infection at all sites and planting dates. Kimpac, towel, sand, A.Aging, and cold tests gave good estimates of field emergence at seed infection levels to 18.2%, but at 32.4% infection, Kimpac and towel tests underestimated field emergence. Tetrazolium and conductivity tests overestimated seed quality at low and high infection levels.
Consumptive Water Use of Three Intensively Managed Bermudagrasses Growing under Arid Conditions
Authors: Garrot D. J. , Mancino C. F.
Published: July 2010

In order for turfgrass managers to meet government mandated irrigation water requirements, conserve limited water resources, and still provide aesthetically appealing and functional turf, field measured consumptive water use requirements of intensively managed bermudagrass (Cynodon sp.) turfs growing in arid regions must be determined. Because bermudagrasses produce deep and extensive root systems, the incorporation of a more infrequent irrigation regimen might result in an acceptable turf while significantly reducing water use. To field‐test this hypothesis, we measured the consumptive water use, water use by soil depth, and the turf quality of C. dactylon (L.) Pers. × C. transvaalensis Davy cv. ‘Tifgreen’ and ‘Midiron’ and C. dactylon cv. ‘TexTurf‐10’ bermudagrasses growing on a Gila loam (coarse‐loamy, mixed (calcareous), thermic Typic Torrifluvent) maintained with a deep and infrequent irrigation regime under fairway conditions. Irrigations were applied only when turf showed symptoms of wilt. Total annual consumptive water use values were ≈60% of reference crop evapotranspiration (ETo), but daily values typically ranged from 70 to 90% of ETo following irrigation or rain to <10% when turf began to wilt. Wetter soil conditions promoted water use from the shallower depths. Turf extracted water from the soil to pressures equivalent to <−1.5 MPa. Overall turf quality, stand density, color, and percent groundcover were considered better than acceptable. Our data shows that bermudagrass growing in an arid environment can be maintained under fairway conditions without a loss in overall turfgrass quality, stand density, color, and groundcover with 834 to 930 mm H2O annually, depending upon variety and ETo.
Sources of Resistance to Pathotype QCC of Puccinia graminis f. sp. tritici in Barley
Authors: Jin Yue , Steffenson Brian J. , Fetch Thomas G.
Published: July 2010

The occurrence of a wheat stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) pathotype (Pgt‐QCC) with virulence for the Rpg1 gene in barley (Hordeum vulgare L.) necessitated the search for resistant barley germplasm. From preliminary screenings of over 18 000 barley accessions, 13 lines were identified as possessing resistance to pathotype QCC: ‘Diamond’, ‘Hietpas 5’, Q21861, PC 11, PC 84, PC 249, PC 250, CI 5541, PI 452406, PI 452421, PI 477843, PI 477854, and PI 477860. This study was conducted to further characterize the reaction of the selected lines to pathotype QCC. The reaction was assessed by evaluating infection types at the seedling stage and infection responses at the adult plant stage in the greenhouse, and by evaluating disease severity and infection responses at the adult plant stage in the field compared to susceptible cultivars. Most lines exhibited low to intermediate infection types at the seedlings stage and moderately resistant to moderately susceptible infection responses at the adult plant stage in the greenhouse experiments. Among the selected lines, Q21861 exhibited the highest level of resistance at both the seedling and adult plant stages. These lines may provide an adequate level of resistance to pathotype QCC for cultivar development.
Simulating Natural Drainage under Turfgrass in Chemical Fate Studies
Authors: Horst Garald L. , Powers William L. , Miller Daniel R. , Shea Patrick J. , Wicklund Eric A.
Published: July 2010

Simulation of field conditions is important when conducting solute movement research in the greenhouse. A study was initiated to develop and test a solute movement system with intact turf‐soil columns subjected to suction approximating field capacity and typical irrigations. Intact soil columns from a Sharpsburg soil (fine montmorillonitic, mesic Typic Argiudoll) planted to Kentucky bluegrass (Poa pratensis L.) were encased in concrete, excavated, and brought to the greenhouse. Porous ceramic plates were attached to some column bottoms and suction (50 kPa) was applied to simulate soil water matric potentials at field water capacity and eliminate perched water tables. Under 2.5‐cm irrigations, evapotranspiration (ET) was 15% greater (P = 0.09) from columns without suction than from columns with suction. Drainage was 460% greater (P = 0.08) from columns under suction receiving 2.5‐cm irrigation. Volume of drainage water and total bromide collected was significantly greater (P = 0.01 and 0.02) from columns under suction receiving 5.0‐cm irrigations than from columns receiving 2.5‐cm irrigations. Averaged bromide concentrations in the drainage did not differ among treatments. Water and solute movement may be underestimated in greenhouse studies using containers without suction plates to eliminate perched water tables.
A Modified Soil Monolith Technique for Characterizing Root Systems
Authors: Buman R. A. , Schumacher T. E. , Riedell W. E.
Published: July 2010

A soil and root system sampling technique that accurately measures root distribution within the soil profile without causing excessive damage to experimental plots would improve the efficiency of root system research. A monolith mapping root sampling technique is described that combines the positive attributes of the soil monolith and profile wall methods with a less destructive hand tool sampling protocol. The objective of this field study was to compare monolith mapping with a standard monolith washing technique for the purpose of measuring root distribution in the upper 30 cm of the root zone. Root systems of maize (Zea mays L.) (V6 stage of development) from plots (Vienna loams oils; fine‐loamy, mixed Udic Haploborolls) treated with broadcast or banded P were sampled using the modified monolith method. The roots present in the soil monolith were mapped (monolith mapping method), and the maps used to represent two‐dimensional root distribution. The soil monolith was then grid‐sectioned into 5.1 by 5.1 by 7.6 cm rectangular blocks and washed to separate roots from the soil. Root length was then measured using a line‐intersect method (monolith washing method). Monolith mapping and monolith washing methods both detected differences in root system distribution in the soil profile. A significant linear relationship (r = 0.87) between root length density and root number as measured by the two methods allows conversion of the numerical data collected by the monolith mapping method into root length density values. We conclude that monolith mapping works well for determining the spatial differences in root distribution in the upper 30 cm of the root zone. The relative time requirements, accuracy, and less destructive nature of the technique (compared with the trench profile and framed monolith methods) result in more efficient collection of data on root system characteristics.
Genetic Control of Reduced Palmitate Content in Soybean
Authors: Horejsi Thomas F. , Fehr Walter R. , Welke Grace A. , Duvick Dan N. , Hammond Earl G. , Cianzio Silvia R.
Published: July 2010

Reduced palmitate content in soybean [Glycine max (L.) Merr.] is controlled by two major alleles, fap1 and fap3. This study was conducted to determine the role that modifying genes may have on the reduced palmitate trait in lines homozygous for the major alleles. Two lines homozygous for fap1 and fap3, AX5152‐34 and AX5152‐105, were each crossed as donor parents to a high‐yielding cultivar with normal palmitate, ‘Kenwood’ or ‘Marcus’. The F1 plants were backcrossed to the high‐yielding cultivar. Two experiments were grown in randomized complete‐block designs at three locations in Iowa with two replications per location. The Kenwood experiment consisted of 14 F4:6 lines from the cross AX5152‐105 × Kenwood, 83 BC1F3:5 lines from five BC1 families from the backcross Kenwood × (AX5152‐105 × Kenwood), Kenwood and AX5152‐105. The Marcus experiment contained 14 F4:6 lines from the cross AX5152‐34 × Marcus, 69 BC1F3:5 lines from the backcross Marcus × (AX5152‐34 × Marcus) among six backcross families, Marcus and AX5152‐34. All lines, except Kenwood and Marcus, were homozygous for both fap1 and fap3. The influence of modifying genes on palmitate content was evident in both experiments. There were significant differences in palmitate content among single‐cross lines, among backcross lines, and among lines within individual backcross families. The palmitate content of each donor parent was significantly different from the means of the corresponding single‐cross and backcross populations. Lines with reduced palmitate were obtained that had higher yield than the recurrent parents, which indicated that reduced palmitate is not detrimental to yield. Lines with reduced palmitate generally had reduced oil content.
Absence of Residual Effects of Defeated Resistance Genes on Phytophthora Rot of Soybean
Authors: Young B. A. , St. Martin S. K. , Schmitthenner A. F. , Buzzell R. I. , McBlain B. A.
Published: July 2010

Defeated resistance genes are genes conferring race‐specific resistance that have been overcome by compatible pathogenic races. Such genes display residual effects if they increase the host's level of either rate‐reducing resistance or tolerance to compatible races. The objective of our research was to investigate residual effects of defeated resistance genes on phytophthora rot [caused by Phytophthora sojae (Kauf. and Gerde.)] of soybean [Glycine max L. (Merr.)]. We used near‐isogenic lines of soybean (cv. ‘Harosoy’) carrying resistance genes Rps1, Rps3, Rps4, Rps5, and Rps6 to develop additional soybean genotypes carrying combinations of two, three, and four resistance genes. We evaluated these genotypes for rate‐reducing resistance and tolerance to phytophthora rot by assessing extent of root lesions, plant height, and plant dry weight after 28‐d growth in the greenhouse in pots with and without inoculum. Race 7 of P. sojae was used because this race was compatible with all resistance genes present. In one experiment, 28 genotypes carrying zero to four resistance genes in either homozygous or heterozygous condition were evaluated with two replications; in a second experiment, 13 genotypes homozygous for zero, one, or two resistance genes were evaluated with six replications. Genotypes carrying Rps5 showed significantly more root rot than rps5 genotypes, possibly due to linkage of Rps5 with a gene or genes for susceptibility. No other significant effects of Rps genes were detected. These results indicate that residual effects cannot be exploited in this pathosystem.
Variation for Water‐Use Efficiency in Alfalfa Germplasm
Authors: Johnson R. C. , Tieszen L. L.
Published: July 2010

Carbon isotope discrimination (Δ) shows promise for estimating water‐use efficiency (WUE, grams dry weight/gram water transpired) in C3 crop species. The objective of this study was to determine if variation for Δ is present in diverse alfalfa (Medicago sativa L.) germplasm, and if Δ is correlated with direct measurements of WUE. Eighteen alfalfa accessions originating from 13 countries were established in 1990 in irrigated and dryland environments at Central Ferry, WA, in a fine‐silty, mixed, mesic Typic Natrixeroll soil. Significant differences among accessions for leaf Δ were observed with no significant environment × accession interaction. Based on 1990 results, high Δ (PI 420400, 20.3‰), middle Δ (P1 522242, 19.7‰), and low Δ (PI 434600,18.9%o) accessions were selected for additional field evaluation in 1991. For the dryland environment in 1991, leaf Δ of PI 434600 was lower than PI 420400, but accession differences were not observed in the irrigated environment. In greenhouse pot studies, accessions did not differ for total plant WUE. But shoot WUE values all differed significantly, and were 2.43,2.09, and 1.73 g dry wt./kg transpiration for the low, middle and high Δ accessions, respectively. Total plant WUE was correlated with Δ only under drought stress (r = −0.55**, n = 30), but shoot WUE and Δ were correlated within well watered (r = −0.63**, n = 30) and drought‐stressed (r = −0.73**, n = 30) treatments. Correlations between shoot WUE and root:shoot values were negative and significant at P = 0.01, suggesting that root/shoot carbon partitioning influenced shoot WUE. Results show reproducible variation for Δ in alfalfa germplasm, and that Δ is potentially useful for evaluating alfalfa germplasm for WUE.
Soybean Flower Production as Related to Plant Growth and Seed Yield
Authors: Dybing Dean C.
Published: July 2010

Flowers are directly related to seed yield through the fruits that form from flowers, but the physiological factors that regulate flower production after induction of the flowering state are not well understood for soybean [Glycine max (L.) Merr.], where the connection of flowering to yield is complicated by abortion of potential fruits. The objectives of this research were to (i) evaluate methods of obtaining flower count data and characterizing flowering in terms of rate of flower production (FRATE), duration of flowering (FPERIOD), and total flowers (FTOTAL) in soybean genotypes differing in numbers of flowers and levels of reproductive abortion; (ii) determine relationships between these characteristics and seed yield; and (iii) measure effects of plant factors on the flowering characteristics when both plant growth and flowering are altered by variation in planting date. Growth and flowering were measured in five plantings during 2 yr at Brookings, SD in Vienna (fine‐loamy, mixed Udic Haploboroll) soil, using cultivars Dassel and Corsoy 79, which have few flowers per raceme, and the many‐flowered lines SD87001 and IX93‐100. Flowering was measured by counting blossoms three times weekly throughout the bloom period (Method I) and by counting fruits and abscission scars for aborted flowers 2 wk after final blossoming (Method U). Cumulative flowering curves determined by Method I were closely fit by the logistic function. Total flowers by Method I was lower than by Method II, but only minor differences were observed between methods for detecting flowering differences caused by planting date or genotype. Flowering traits measured by Method I accounted for 60 to 77% of the variation in seed yield. Genotypes differed markedly in the relationship of plant characteristics to flowering traits, but rate of increase in height in vegetative stage generally had significant negative correlation to FPERIOD, had positive correlation to FTOTAL and FRATE, and was identified as one of several factors that had major influence on flowering traits. It is concluded that large and rapidly growing soybean plants tend to have short FPERIOD with high FRATE and FTOTAL, but genotypes also may have additional traits that determine flower production characteristics.
Effects of Glutenin Protein Polymorphisms on Breadmaking Quality of Winter Wheats
Authors: Graybosch Robert A. , Peterson C. James , Lee Jai‐Heon , Shelton David R.
Published: July 2010

Wheat (Triticum aestivum L.) end‐use quality variation often is attributed to variation in glutenin protein composition. The magnitude of this relationship was tested through analysis of wheat lines containing within‐line glutenin protein polymorphisms. One hundred winter wheat lines of diverse origin were screened for the presence of withinline glutenin protein polymorphisms through sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). Fourteen percent of the tested lines were found to be polymorphic (composed of two or more distinct biotypes). Biotypes, defined as groups of individuals with the same genotype within a polymorphic line, were selected from six wheat lines of diverse quality. Analysis of dough‐handling and breadmaking characteristics of the biotypes found in six polymorphic lines demonstrated significant biotype‐dependent responses for numerous quality attributes. Biotypes, however, rarely exceeded the source line for any one specific quality attribute and never exceeded the source line for all quality variables. The presence of biotypes of diverse quality potential may contribute to within‐line quality variation with time or across the geographic range of cultivation. However, the magnitude of such variation is slight compared with that observed between cultivars. Biochemical variation in single or few glutenin proteins contributed little to total genetic variation for quality.
Leaf Characteristic Variation in Hybrid Lovegrass Populations
Authors: Voigt P. W. , Tischler C. R.
Published: July 2010

Apomictic plant breeding is being practiced in several turf and forage grasses. Variation released during apomictic breeding has been discussed, but few reports have quantified this variation. Our objectives were to characterize variation among lovegrass, Eragrostis curvula (Schrad.) Nees, hybrids and their parents, compare parents and hybrids, and determine interrelationships among the characteristics studied. Twenty‐nine hybrids from each of two populations, A and B, resulting from the cross of two sexual plants [full‐sibs with low levels of epicuticular wax (wax) and narrow leaves] with an apomictic plant (high levels of wax and wide leaves) were studied in separate experiments conducted in 1989 and 1990. Leaf width and wax, moisture content (weight) per leaf area, and specific leaf weight (dry weight per leaf area) were studied. Parents differed and variation among hybrids was significant (P < 0.01) for all four characteristics in both studies. The range of the hybrids exceeded that of the parents in all cases. Transgressive segregation was observed only for greater wax, leaf width, and weight and could have resulted in part from extra chromosomes transmitted from the male parent, a plant with 2n = 7x = 70 chromosomes, compared to the 20 chromosomes expected from the tetraploid female parents. Hybrids that were recombinants, e.g., high wax and narrow leaves or low wax and wide leaves, were frequently observed. Both extreme individuals (transgressive segregants) and hybrids with less extreme but new combinations of characteristics (recombinant individuals) were available for selection even within these relatively small populations. Release of genetic variation during apomictic plant breeding can be extensive.
Agronomic Evaluation of Non‐Nodulating and Hypernodulating Mutants of Soybean
Authors: Pracht J. E. , Nickell C. D. , Harper J. E. , Bullock D. G.
Published: July 2010

Enhanced nodulation and dinitrogen fixation by soybean [Glycine max (L.) Merr.] has been proposed to increase yield relative to normal nodulating types. This study was conducted to determine if two hypernodulating soybean mutants (NOD4 and NODI‐3) were capable of increased yield, compared with normal nodulating cultivars Williams 82 and Hobbit 87, and a non‐nodulating cheek (NNS). Performance data were collected in 1990 and 1991 from a replicated design using two row‐widths, 18 and 76 cm, at three locations in east central Illinois, Dwight, Champaign and Urbana. No significant differences in yield were found between the hypernodulating mutants and the nonnodulating cheek. Yields of the normal nodulating cultivars were significantly higher than for the nodulation mutants. A highly significant year to location interaction was noted for all parameters measured, but row width did not significantly affect seed yield. Protein concentration was significantly greater for NOD4 than for Williams 82, but lower seed yield resulted in less total N accumulation in seed of NOD4. The hypernodulated mutants (NOD4 and NOD1‐3) were agronomically inferior to Williams 82 and Hobbit 87, suggesting that these mutants likely have other deleterious mutations that override any possible benefit of enhanced nodulation.
Spring Wheat Diversity in Irrigated Areas of Two Developing Countries
Authors: Souza E. , Fox P. N. , Byerlee D. , Skovmand B.
Published: July 2010

Crop genetic diversity may not be apparent from plant phenotypes. Coefficients of parentage were used to examine genetic diversity and compare trends in spring wheat cultivars grown in the Yaqui Valley of Mexico (1972–1991) and the Punjab of Pakistan (1978–1990). Coefficients of parentage estimate probabilities of retaining latent diversity rather than focusing on the apparent diversity of highly heritable traits (e.g., rust resistance alleles). A small trend towards increased genetic diversity was found in the Pakistani Punjab. In the Yaqui Valley, large oscillations in diversity occurred without significant trends. In comparing the two regions, the latent genetic diversity in the Yaqui Valley based on parentage and area of production in a given year (weighted diversity) was 20% less than in the Punjab. However, the lower diversity was partially offset by rapid turnover in germplasm in the Yaqui Valley. The rate of change in germplasm (temporal diversity) was 22% lower in the Pakistani Punjab than in the Yaqui Valley. The temporal diversity of cultivars used by growers in the Yaqui Valley was greater than among cultivars recommended for use by the research services, indicating that growers replace germplasm faster than the changes in recommended cultivars. The opposite was found in the Punjab. In the Yaqui Valley, individual cultivars dominated production for 1 to 3 yr, while in the Punjab, one cultivar, ‘Yecora’ dominated production for 7 yr. We conclude that (i) cultivar improvement programs did not erode genetic diversity in production areas currently growing improved cultivars and (U) patterns of cultivar use by farmers were more important than the composition of recommended cultivars in determining genetic diversity.
Electrophoretic Identification of Cross‐Pollinated Bentgrass Species and Cultivars
Authors: Yamamoto Ikuko , Duich Joseph M.
Published: July 2010

Analysis of isoenzyme phenotypes as an identification method has been used mainly in apomictic and vegetatively propagated species and/or cultivars. This study was conducted to demonstrate an improvement in the use of electrophoresis for cross‐pollinated Agrostis cultivar identification. A bulk leaf sample extract of approximately 200 seedling plants from each of 32 cultivars and/or seed lots from four Agrostis species was examined for phosphoglucose isomerase (PGI), triosephosphate isomerase (TPI), glutamate oxaloacetate transaminase (GOT), and peroxidase (PRX) isoenzyme activities by starch gel electrophoresis. Isoenzyme activities at PGI‐2 region showed the most distinctive polymorphism, and we could identify 24 of 26 tested cultivars (twelve A. palustris Huds, 10 A. capillaris L., one A. castellana Boiss. and Reut., two A. gigantea Roth., and one A. canina L.) based on PGI‐2 banding patterns. A. palustris cultivars were separated into four groups by both TPI and GOT banding patterns. Ten cultivars of A. capillaris L. and one A. castellana Boiss. and Reut. were separated into four groups by TPI. Peroxidase banding patterns were predominantly effective for species separation only. Our results demonstrated that the electrophoresis technique is a quick, accurate, and repeatable identification method for cross‐pollinated Argostis cultivars.
Analysis of Heat Shock Response in Perennial Ryegrass using Maize Heat Shock Protein Clones
Authors: DiMascio J. A. , Sweeney P. M. , Danneberger T. K. , Kamalay J. C.
Published: July 2010

Evidence suggests that heat shock proteins (HSP) may be involved in differences in thermal tolerance among perennial ryegrass (Lolium perenne L.) cultivars. It seems possible that HSP could be useful in developing laboratory assays for thermal tolerance in perennial ryegrass. To evaluate the possibility of using HSP genes or gene products to screen for thermal tolerance, thermal‐tolerant and thermal‐sensitive cultivars were germinated and heat treatments were conducted in a dry germinator in constant light. The two cultivars exhibited differences in root, shoot, and total seedling length when briefly subjected to high temperatures (55 °C) following an initial acclimation period (40 °C). In vitro translation products of total RNA indicated that different messenger RNA (mRNA) populations were present in seedlings exposed to stress temperatures. Hybridizations of two maize (Zea mays L.) heat shock clones, pMON9501 (HSP 70) and pZmHSP26 (HSP 26), to genomic DNA indicated a high degree of homology between the two perennial ryegrass cultivars and the HSP 70 clone and a moderate homology of the cultivars with HSP 26. The HSP 70 clone revealed restriction fragment length polymorphisms between the cultivars. Hybridizations of the two maize heat shock clones to Northern blots with perennial ryegrass total RNA showed that HSP 70 and HSP 26 mRNA were heat inducible. There were detectable differences in the levels of heat‐induced HSP 26 mRNA between the two cultivars. Our findings indicated that analysis of HSP could provide the basis of a rapid and reliable characterization of thermal tolerance in perennial ryegrass.
Applications of Molecular Methods and Statistical Analyses for Discrimination of Accessions and Clones of Vetiver Grass
Authors: Kresovich Stephen , Lamboy Warren F. , Li Rugang , Ren Jianping , Szewc‐McFadden Amy K. , Bliek Sharon M.
Published: July 2010

Because (i) origins and genealogies of vetiver grass have been poorly documented, and (ii) morphological uniformity and infrequent flowering precluded accurate identification of selected clones, an investigation was undertaken to link molecular methods with rigorous biometric analysis to discriminate accessions and clones. Successful DNA profiling is highly dependent on the reproducibility of the assay. Our ability to generate consistent results may have been a result of (i) genomic DNA quality, (ii) rigorous oligonucleotide primer selection, and (ill) DNA amplification protocol stringency. Because of the low level of replicate variability, we were able to bring a high level of resolution to the analysis of identity. Though genetic redundancy may be more difficult to establish than genetic uniqueness, the data support with a high degree of certainty that the accessions ‘Huffman’ and ‘Boucard’ were essentially the same genotype. A contrasting case to the Huffman‐Boucard example was found among the putative clones of ‘PI 196257’. Our analysis indicated that each clone of PI 196257 was genetically unique.
Effect of Growth Habit on Yield and Agronomic Characteristics of Late‐Planted Soybean
Authors: Ouattara Sohédjié , Weaver David B.
Published: July 2010

Seed yield of double‐cropped soybean [Glycine max (L.) Merr.] in the southeastern USA is reduced compared with full‐season soybean, and most agronomic traits are affected. This study was initiated to determine the effects of determinate (dr1) and indeterminate (Dt1) growth habit genes on yield and agronomic characteristics of late‐planted near‐isogenic soybean lines (near‐isolines) in the southeastern U.S. Twenty‐three determinate and 23 indeterminate near‐isogenic soybean lines from three populations were compared in the field at two locations (Brewton and Tallassee, AL) in 1991 and three locations (Shorter, Tallassee, and Brewton, AL) in 1992. Growth habit had no effect on seed yield, but growth habit × location effects were large. At Brewton, indeterminate lines yielded more than determinate lines; at Tallassee, both types yielded equally; and at Shorter, determinates yielded more. Flowering and reproductive periods were longer for indeterminates than for determinates at all locations. Determinates were shorter at Growth Stages R1 and R8 and produced fewer mainstem nodes per plant after initiation of fiowering than did indeterminates. Seed oil percentage was lower and protein content higher for indeterminates than for determinates. We concluded that growth habit × location interactions play a large role in determining the yield advantage of either growth habit in double‐cropped, late‐planted cropping systems.