bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification and Pedigree Verification of Tall Fescue Cultivars Utilizing the Prolamin Seed Protein Fraction
Authors: Abernethy R. H. , Steiner J. J. , Wofford D. S. , Thiel D. S.
Published: July 2010

Several techniques based on the electrophoretic separation of seed proteins have been developed that can be used to detect differences among cultivars of crop species. Little work has been done to statistically interpret these differences or to relate them to actual pedigrees. In this work, 16 cultivars of tall fescue (Festuca arundinacea, Schreb.) have been distinguished based on qualitative and/or quantitative differences in alcohol‐soluble prolamin seed protein banding patterns. Proteins were extracted from seed flour with an ethanolic solution containing dithiothreitol and polyvinylpyrrolidone. This improved the resolution of polypeptides using an acidic polyacrylamide gel electrophoresis system. The mobility of polypeptides relative to bovine serum albumin (Rm) and the staining intensity (band density) were determined for each cultivar. A series of cluster Q‐analyses were performed on the data as a statistical approach to definitively show relationships among cultivars. Only nonassociated independent bands were used in the analysis. After the initial grouping of cultivars, a subset of nine cultivars that were not separated by the initial Q‐analysis was re‐examined using those independent bands that were excluded from the initial analysis. The resulting clusters of cultivars from the two analyses compared closely with the known pedigrees of the cultivars. Use of cluster analysis of the prolamin polypeptides should be applicable to the development of databases for plant cultivar identification and variety protection.
Development and Characterization of Friable, Embryogenic Oat Callus
Authors: Bregitzer P. , Somers D. A. , Rines H. W.
Published: July 2010

Friable, embryogenic (FE) callus cultures are desired for genetic manipulations at the cellular level. The goal of this research was to develop and characterize such cultures for oat (Avena spp.). Nonfriable (NF) oat callus derived from immature embryos was plated on a modified MS medium containing 60 g L−1 sucrose and no hormones. This treatment resulted in the development of distinct somatic embryos that germinated to form complete plants when placed on a modified MS medium containing 20 mg L−1 sucrose and no hormones. Embryogenic sectors isolated from 26‐wk‐old NF callus were visually selected during repeated subculture on a modified MS medium containing 2 mg L−1, 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 20 g L−1 sucrose to produce FE callus. Transfer of FE callus to a modified MS medium containing 60 g L−1 sucrose and no hormones induced the maturation of somatic embryos. Subsequent transfer of this FE callus to modified MS medium containing 20 g L−1 sucrose and no hormones allowed the germination of some of these embryos. Plants were regenerated from FE callus lines for more than 78 wk after FE callus establishment. Friable embryogenic callus also was initiated directly from immature embryos of three genotypes and seedling mesocotyls of two genotypes. Genotypic variation in this response was noted. The FE oat cultures represent an improved callus type for in vitro genetic manipulation of oat.
Improvement of Anther Culture Methods for Haploid Production in Wheat
Authors: Zhou Huaping , Konzak C. F.
Published: July 2010

The yield of haploid production in wheat (Triticum aestivum L.) anther culture has been extremely low with the currently employed methods. The objective of this study was to determine whether variation in anther culture media would affect the yield of haploids. After a 48‐h cold pretreatment, anthers from six spring wheat cultivars and one winter wheat cultivar were cultured on liquid and agar‐solidified media, and in some cases the liquid medium was supplemented with Ficoll (Sigma Chemical Co., St Louis, MO). Liquid culture significantly increased callus induction, which averaged 98.3 calli per 100 anthers for the seven cultivars tested, compared with 5.1 calli per 100 anthers for agar culture. Although the calli from liquid media usually had lower plantlet regeneration than calli from agar‐solidified media, regeneration ability was improved by adding 200 g/L Ficoll 400 to the liquid induction medium, or by changing the plant growth regulator composition of the regeneration medium. By employing the liquid culture method and the modified regeneration medium, it is now more feasible to use doubled haploids in plant breeding practice and genetic research.
Inheritance of Partial Resistance to Blast in Indica Rice Cultivars
Authors: Wang Ziming , Mackill D. J. , Bonman J. M.
Published: July 2010

The blast fungus (Pyricularia oryzae Car.) is a major cause of yield loss in rice (Oryza sativa L.). Partial or field resistance has received much attention as a means of conferring durable blast resistance. Previous inheritance studies of partial resistance have used japonica rices. The primary objective of this study was to determine the inheritance of partial resistance to leaf blast measured by lesion number (LN) and lesion size (LS) in crosses involving two indica rice cultivars with high partial resistance (‘IR36’ and ‘Milyang 42’) and two with low partial resistance (‘IR50’ and ‘Milyang 57’). Greenhouse‐grown plants at the partially extended sixth‐leaf stage were inoculated with a conidial suspension derived from a monoconidial isolate. Broad‐sense heritability for selection based on a single plant ranged from 0.20 to 0.50 for LN and 0.35 to 0.67 for LS. The narrow‐sense heritability ranged from 0.18 to 0.38 for LN and 0.30 to 0.43 for LS. Significant (P < 0.01) differences between F3 families selected from the most resistant and most susceptible F2 plants were observed for crosses between resistant and susceptible parents for both LN and LS. The F2 populations also were grown in the field blast nursery under natural infection, and the area under the disease progress curve (ADPC) was calculated based on percent diseased leaf area from 22 to 39 d after seedling emergence. The broad‐sense heritability for ADPC was 0.40 and 0.30 for two resistant ✕ susceptible crosses and 0.14 for a resistant ✕ resistant cross. The results indicate that heritability for partial resistance to rice blast in these crosses is relatively low, and that selection for resistance should be effective if resistance levels can be assessed accurately.
Agronomic Evaluation of Latin American Maize Accessions
Authors: Castillo‐Gonzalez F. , Goodman M. M.
Published: July 2010

Use of photoperiod‐sensitive tropical germplasm for breeding in temperate regions is hampered by several problems. The inability to accurately evaluate photoperiodically sensitive accessions under long‐day conditions leads to an inability to choose the best available materials. The use of short‐day seasons in Homestead, FL, and Weslaco, TX has been investigated for the screening of the available set of typical accessions of the Latin American maize (Zea mays L.) races. Nursery data were used to select about 400 better accessions from a set of some 1300 typical accessions. Replicated trials under short‐day conditions, which for maize act as day‐neutral conditions, were used to screen the selected accessions, with temperate and tropical hybrids used as standards for comparison. Yield distributions of the tropical accessions were symmetric under short‐day conditions (in Florida and Texas), but highly skewed toward zero under longday conditions (in North Carolina) for all but the earliest maturity group. When yields and differences in male and female flowering times were plotted against latitude, distinctly different patterns were observed under long‐ and short‐day conditions. Under long‐day conditions, yields were greatly depressed, and differences between male and female flowering greatly increased for accessions originally collected between 15 °C N and 15 °C S latitude, as compared to results under short‐day conditions, where both yields and male vs. female flowering differences had largely linear regressions on latitude, with slopes near zero. Under short‐day test conditions, it was possible to identify races of maize and specific geographic regions as promising sources of tropical maize germplasm for temperate breeding programs.
Morphological and Chemical Responses to Selection for in Vitro Dry Matter Digestibility in Smooth Bromegrass
Authors: Casler M. D. , Carpenter J. A.
Published: July 2010

Improved nutritional value of forage crops, through selection and breeding, can be due to changes in chemical composition or the relative amounts of tissues or organs with differing nutritional value, or both. The objective of this study was to evaluate morphological and chemical changes associated with divergent selection for in vitro dry matter digestibility (IVDMD) in smooth bromegrass (Bromus inermis Leyss.). Parents and progeny, selected for high or low IVDNID, werevaluated in replicated field trials for two harvests in each of 2 yr. Cell wall composition and IVDMD of stems (stem plus leaf sheath), leaves (leaf blade), and whole plants were determined. Several morphological traits of leaves and stems were also determined. Whole plant variation in IVDMD was due mainly to differences in stem IVDMD. Increased stem IVDMD was associated with reduced lignin and cellulose, but increased hemicellulose contefits, with overall reduced cell wall content. Increased leaf IVDMD was due to similar causes, but without reduced cell wall content. These results provide further evidence that IVDMD can be improved by genetic modification of cell wall composition, without reducing total cell wall content. Although differences were not always consistent, high IVDMD genotypes tended to have larger and heavier, but fewer leaves. Leaf/stem ratio changed slightly but not enough to explain differences in whole plant IVDMD. Selection for IVDMD did not appreciably affect plant growth and development in these environments.
Greenhouse Evaluation of Subterranean Clover Species for Susceptibility to Iron‐Defeciency Chlorosis
Authors: Gildersleeve Rhonda R. , Ocumpaugh W. R.
Published: July 2010

Subterranean clover (subclover) is the common name for three Trifolium species (T. brachycalycinum Katzn. and Morley, T. yahninicum Katzn. and Morley, and T. subterraneum L.), which show promise for use in winter pastures in the southeastern USA. On calcareous soils in Texas, ‘Mt. Barker’ subciover (T. subterraneum) often has Fe‐deficiency chlorosis, while ‘Clare’ subclover (T. brachycalycinum) appears to be resistant. Our objective was to screen 22 available subclover cultivars in the greenhouse for susceptibility to Fe‐deficiency chlorosis. Three replications of seven plants per cultivar were grown in Conetainers ® in two calcareous soils. At 4 wk of age, the plants were subjected to high soil moisture conditions to induce the chiorosis. Two weeks later, all plants were scored and leaf samples were analyzed for total chlorophyll content. Both parameters indicated a large difference among cultivars for susceptibility to Fe‐deficiency chlorosis. Visual chiorosis scores and leaf chlorophyll contents were inversely related (r2 = 0.69). Cultivars belonging to T. brachycalycinum had no chlorosis and had high leaf chlorophyll contents (> 1.2 mg g−1). Within the species T. yanninicum, three cultivars appeared to be only slightly susceptible, while ‘Yarloop’ had moderate chlorosis when grown in the Partita soil (Clayey, mixed, hyperthermic, shallow Petrocalcic Paleustoil). Cultivars of the species T. subterraneum had the greatest range of chlorosis scores. ‘Karridale’ was consistently most susceptible to Fedeficiency chlorosis, while ‘Woogenellup’ was the least susceptible. The variation among cultivars within the species T. subterraneum suggests that selection for resistance to Fe‐deficiency chlorosis maybe possible within this species.
Alternative Backcross Methods for Introgression of Variability into Triticle via Interspecific Hybrids
Authors: Barker T. , Varughese G. , Metzger R.
Published: July 2010

In order to transfer genetic variability from bread wheat (Triticum aestivum L. em. Thell) to triticale (X Triticosecale Wittm.), interspecific hybrids are made and then backcrossed to triticale to recover desired phenotypes. The interspecific F1'S are normally used as females in the backcrosses, but a high rate of aneuploidy is transmitted to the BC1 through the hybrid ovules. A study was conducted to evaluate backcrosses using the F1 as female vs. the reciprocal crosses using triticale as female. Data from two sets of crosses were collected on number of seedset per spike, percent recovery of viable plants, percent recovery of 42‐chromosome plants, mean seed yield per plant, and number of plants selected. Using the F1 as male parent and triticale as the female resulted in 58.0 to 81.7% recovery of viable plants vs. 3.8 to 34.0% for the TCL‐male backcrosses. The percentage recovery of 42‐chromosome plants ranged from 31.9 to 35.6% from Frmale backcrosses vs. 0.3 to 18.6% from TCL‐male backcrosses. However, the difference in number of seeds set per spike and the per‐plant seed yield increase for F1‐male crosses were not statistically significant. The F1‐male mating system, which utilizes pollen screening (elimination of inviable gametes), appears permit recovery of more viable plants and a higher proportion of euploid triticales following a single backcross.
Canopy Temperature, Seed Yield, and Vapor Pressure Deficit Relationship in Soybean
Authors: McKinney N. V. , Schapaugh W. T. , Kanemasu E. T.
Published: July 2010

Drought stress frequently limits soybean production. Thirty soybean [Glycine max (L.) Merr.] lines in a field trial in 1982 were tested for canopy temperatures and response to vapor pressure deficit (VPD) as criteria for yield and drought tolerance. Lines were monitored for canopy temperature differential (Td = canopy temperature — air temperature), and wet and dry bulb temperatures determined the VPD of the air. The five warmest and five coolest lines based on seasonal mean Td, or , were monitored for in 1983 and 1984 under irrigated and nonirrigated environments. Soil type was (Umucic Hapiustoll) a Muir silt loam (fine‐silty, mixed, mesic in 1982 and 1984) and a Eodora silt loam soil (coarse‐silty, mixed, mesic) Fluventic Hapludoll) in 1983. Differences for among the lines were negatively correlated with seed yield. Warm genotypes were not more productive under dryland conditions, nor was the ratio of dryland yield to irrigated yield (yield stability) greater than for cool genotypes. Neither nor the ratio of dryland to irrigated ( stability) was significantly correlated with yield stability. Lines did not differ significantly in their Td response to VPD (measared as the Td — VPD regression slope) on a seasonal basis. On 5 d with maximum VPD greater than 3 kPa, however, Td response to VPD differed significantly in the irrigated environment. These differences were not related to , yield, or yield stability. Indirect selection for yield using canopy temperature may be effective; however, warm genotypes are not more drought tolerant or yield stable than cooler selections.
Daily Flower Production, Rate of Seed, and Fiber Flax Cultivars as Related to Seed Yield
Authors: Dybing C. Dean , Lay C.
Published: July 2010

Flower production of flax (Linum usitatissimum L.) should be directly related to the yield component fruits per area, but past studies have shown that neither total flowers nor length of bloom was as effective as daily flower production rate for modeling seed yield of one cuitivar. The objective of this study was to develop procedures relating flower production to seed yield and its components for a number of other cultivars of diverse yield, maturity, and utilization types. Total flowers, duration of bloom, and seed yield were estimated from daily flowering for 18 cultivars and experimental lines grown 4 yr in the field. Relationships between flowering and components of yield were evaluated by path coefficient analysis. Two previously developed equations estimated total flowers within ± 20% of observed values, six estimate duration of bloom within ± 10%, and none estimated yield within ± 50%. Yield estimates were improved when the data set was limited to plots with yield levels above 1000 kg ha‐1. New equations were derived that related maximum daily flower production rate (slope at the inflection point of cumulative flower count plotted over time) and flower count on the 14th day of the bloom period to yield for six types of flax. Path coefficient analysis showed that seed yields from fiber and low yield seed flax were more directly affected by total flower production and flower abortion than were yields of high yield seed flax cultivars. Duration of bloom was negatively correlated to seed yield for most types of flax. We conclude that maximum daily flower production rate may be a growth function that relates vigor during flowering to seed yield at harvest.
DNA Amplification among Anther‐Derived Doubled Haploid Lines of Tobacco and Its Relationship to Agronomic Performance
Authors: Reed Sandra M. , Wernsman E. A.
Published: July 2010

Anther culture in tobacco (Nicotiana tabacum L.) has been associated with yield losses and DNA amplification without chromosome number changes among doubled haploid lines. The objectives of this study were to confirm the amplification phenomenon and to determine if increases in DNA are correlated with yield losses. Total nuclear DNA was determined for two cultivars, ‘NC95’ and ‘Coker 139’ (C139), and six doubled haploid (DH) lines derived from cultivar. The DHs were selected so that approximately equal increments of yield losses would be present among the array. The DNA analysis was performed via flow cytometry on isolated nuclei stained with the DNA‐specific fiuorochrome propidium iodide. Agronomic data also were collected on the DH lines. Results indicated that genotypic effects for nuclear DNA were highly significant. While the DNA increases observed among the NC95 genotypes were not statistically significant, doubled haploids derived from C139 had significantly more DNA per nucleus than C139. Coker 139 DHs also sustained greater yield reductions from the parental cultivar than did the NC95 DH lines. Regression analyses of meanuclear DNA values of C139 genotypes on mean leaf yields resulted in a correlation coefficient of ‐0.69; this was significant only at the 0.1 probability level. While DNA amplification among anther‐derived doubled haploids of tobacco was confirmed in one cultivar, DNA amplification and yield losses do not appear to be strongly correlated. The lack of a linear relationship between these two variables may be caused by different chromosomal amplification sites among the doubled haploid lines.
Grain Sorghum Resistance to Midge by Yield Loss vs. Visual Scores
Authors: Peterson G. C. , Ali A. E. B. , Teetes G. L. , Jones J. W. , Schaefer K.
Published: July 2010

Biology of the sorghum midge, Contarinia sorghicolà (Coquillett), necessitates testing of sorghum, Sorghum bicolor (L.) Moench, cultivars in field plots in multiple locations and/or years to identify resistant genotypes. Using converted exotic sorghum cultivars, this study was conducted to compare visual damage scores across locations and years vs. indirect resistance measurements (percentage yield loss and number of midge per panicle) in a single location and year with two planting dates. Visual damage ratings were made at physiological maturity on the percentage of blasted kernels per panicle in replicated, randomized‐complete‐block field experiments at three locations in 1983 through 1985. In 1985, indirect measurements and visual damage ratings were made at one location. A significant positive relationship was found between visual midge damage rating and percentage yield loss (r = 0.347), and between visual midge damage rating and midge number (r = 0.220). Percentage yield loss did not increase the reliability of identification of resistant cultivars. Cultivars identified with resistance by both methods were IS8232C, IS8237C, IS8112C, IS2740C, IS3390C, IS7132C, IS2685C, IS957C, IS7193C, IS2144C, and IS12572C. The correlation between percentage yield loss and midge number (r = 0.090) was nonsignificant. Both methods depend on high midge density to differentiate resistant and susceptible genotypes. When midge were not abundant good differentiation was not obtained. Indirect resistance measurements were more time consuming than a single visual rating at maturity, and when multiple years or locations were required, the visual damage rating was a more effective method of germplasm evaluation.
Response from Phenotypic Recurrent Selection for Root Regeneration after Taproot Severing in Alfalfa
Authors: Hansen J. L. , Viands D. R.
Published: July 2010

Alfalfa (Medicago sativa, S.) can regenerate secondary roots after taproot severing by biotic and abiotic factors. The research objectives were to: (i) determine progress from three or four cycles of selection of plants with many large secondary roots regenerated after taproot severing, (ii) compare techniques to evaluate plants for root regeneration capability, and (iii) determine whether alfalfa populations selected for higher root regeneration capability differed in stand and forage yield after frost heaving compared to nonselected populations. Six‐wk‐old plants, established in the greenhouse, were cut to taproot length of 3 cm and transplanted to two fields (artificial taproot severing). Over locations, four of five populations showed improvements for number of secondary roots regenerated per plant. The selected populations averaged 27% more regenerated secondary roots (P < 0.01), 25% larger taproots (P < 0.01), and 10% higher seedling weight (P < 0.05) than the original populations. Correlations were significant between field and greenhouse evaluations for secondary root number (r = 0.82, P < 0.01) and taproot size (r = 0.73, P < 0.01) after artificial taproot severing. Greenhouse experiments revealed that number of secondary roots regenerated after artificial taproot severing was positively correlated with that after severing by Phytophthora megasperma Drechs. f. sp. medicaginis (r = 0.85, P < 0.01). In the second production year of a yield trial severely injured by frost heaving, two selected populations averaged 50% higher stand during the spring and 13% (0.90 Mg ha−1) more forage at the first harvest than did two unselected populations. Selection and evaluation for root regeneration capability in the greenhouse after taproot cutting is the most efficient method studied since the CV's and experimental resources were lowest.
Field Response of Tobacco after Ten Generations of Selection for Seedling Weight
Authors: Matzinger D. F. , Wernsman E. A.
Published: July 2010

Indirect selection may be a viable technique in certain situations for improving correlated traits. This study was designed to evaluate the efficacy of seedling selection as a means of improving mature plant performance. Field evaluations were conducted on nine generations of a Black Shank Resistant Synthetic tobacco (Nicotiana tabacum L.) population that had been selected 10 generations for 19‐d seedling weight on regular or stress nutrient agar. Linear increases in mean yield cycle−1 were 1.43 g plant−1 for the population selected on stress nutrient agar and 0.99 g plant−1 when selection was on regular nutrient agar. The only other significant change detected was a decrease in total alkaloids of 0.65 mg g−1 cycle−1 for the regular nutrient agar selections. The lack of a decrease in total alkaloids accompanying the increase in yield of the stress agar selections suggests indirect selection of root modifications that increased the efficiency of total alkaloid synthesis. The increase in yield from 10 cycles of indirect seedling recurrent mass selection on stress agar was equivalent to about 1.5 cycles of direct recurrent mass selection for yield in other field experiments.
Water Use by Legumes and its Effect on Soil Water Status
Authors: Badaruddin M. , Meyer D. W.
Published: July 2010

To make informed decisions on whether to include legumes in cropping systems, information is needed on water use by legumes and its effect on soil water availability to subsequent crops. The objectives of this study were to determine the water use, water use efficiency (WUE), and soil water depletion pattern of four grain legumes and three green‐manure or forage legumes. Field studies were conducted on a Fargo silty clay (fine, montmorillonitic, frigid Vertic Haplaquoll) at Fargo and on a Perella‐Bearden silty clay loam (fine‐silty, mixed, frigid Typic Haplaquoll; fine‐silty, frigid Aeric Calciaquoll) at Prosper, ND in 1986 and 1987. Soil water to a depth of 2.2 m was determined by the neutron attenuation method at 15‐d intervals. Legume crops used 10 to 25% more seasonal water than wheat (Triticum aestivum L.) across environments, but WUE (kg dry matter ha−1 mm−1 of water) of legumes was 0 to 25% greater than that of wheat. Green‐manure and forage legumes generally had greater water use and WUE than grain legumes, and this was associated with their longer growing season and higher dry matter production. Cumulative water depletion during June to September by green‐manure, forage, and grain legumes was 70, 63, and 43 mm greater, respectively, than that of a fallow check, and was not significantly different from that of wheat in two of four environments. However, an increase in soil water content occurred at the 0‐ to 0.3‐m soil depth for all treatments in the following spring across three environments. Soil water content in the spring following a legume was not significantly different from that following wheat and was only about 30 mm greater than that of fallow across environments. These results indicate that growing some legumes in cropping systems may not substantially affect the soil water content compared to continuous cereal cropping or to fallow.
Nutrio‐Physiological Evaluation of the Polyethylene Glycol Test of Cell Membrane Stability in Maize
Authors: Premachandra G. S. , Saneoka H. , Ogata S.
Published: July 2010

Cell membrane stability (CMS) of maize (Zea mays L.) was measured by the polyethylene glycol (PEG) test and compared with the nutrio‐physiological characteristics to examine the relationship of plant processes involved in differential ion leakage. Two pot experiments were conducted in the glasshouse under three soil moisture levels (MPa 0 to −0.05, −0.3 to −0.9, and −1.2 to −1.5) using three cultivars (P‐3358, G‐4578, and FFR‐677) of maize. Leaf water potential, osmotic potential, stomatal resistance, cuticular resistance, excised‐leaf water retention capability, degree of leaf rolling, total plant weight, and total root length as well as the CMS by the PEG test were measured when the plants were 60 d old. Nutrient concentrations in leaf tissues, cell sap, and cell leachate were analysed. Cell membrane stability measured by the PEG test was well related to the other physiological measurements. It was highly or very highly correlated with leaf water potential (r = −0.869**), (significant at P = 0.01) osmotic potential (r = −0.946**), excised‐leaf water retention capability (r = 0.767**), K concentration in leaf tissues (r = 0.757*) (significant at P = 0.05) and cell sap (r = 0.690*), and the degree of leaf rolling. Cell membrane stability appears to be influenced by osmotic potential of leaf tissues. Sugar and K were the major osmotic contributors. In conclusion, we find the PEG test to be a useful measure of drought tolerance in maize.
Carbohydrate Partitioning and Nodule Function in Common Bean after Heat Stress
Authors: Hernandez‐Armenta R. , Wien H. C. , Eaglesham A. R. J.
Published: July 2010

Previous work has shown that daily temperature maxima of 38 °C eliminate N2‐fixing activity in common bean (Phaseolus vulgaris L.) in less than 3 d. The purpose of this work was to (i) determine if this response is related to diminished supply of C to nodules and (ii) investigate the recovery of nodule function following short‐term heat stress. ‘Jutiapa’ was grown in sand culture at 26/22 °C (day/night) until 16 d after planting, then transferred to 38/22 °C for 6 d. Acetylene reduction activity (ARA) was eliminated at 38 °C, but nodule concentrations of sucrose and glucose at that temperature were equal or higher than at 26 °C throughout the 6‐d period. Stressed nodules and controls had 127 ± 12 and 90 ± 10 mg of starch per g of dry weight, respectively, after 3 d of treatment, which was the largest difference observed. Treated plants tended to have higher levels of sucrose, glucose, and starch in shoots, particularly in stems, than did controls. In a similar experiment, cells of stressed nodules showed loss of cytoplasm and rupture of peribacteroid membranes after 6 d of heat. Recovery of ARA started 1 wk after the removal of the stress; at that point, treated plants and controls had shoot N contents of 30 and 118 mg plant−1, respectively. This N deficiency caused long‐lasting alterations of plant growth and development. The inhibition of nodule function by high temperature was not related to availability of carbohydrate, but to the breakdown of the bacteria‐infected cells.
Cell‐Wall Carbohydrates in Leaves, Stems, and Herbage of Alfalfa and Red Clover
Authors: Hornstein J. S. , Buxton D. R. , Wedin W. F.
Published: July 2010

Digestion of herbage by ruminants is largely dependent on composition and organization of polysaccharides in plant cell walls (CW). This study was conducted to determine the concentration of CW neutral sugars from polysaccharides in maturing alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) leaves, stems, and total herbage and to determine their relationship to digestibility. Field‐grown plants were sampled during seven harvests over two growth periods. At each harvest, plants were divided into three‐node (red clover) or six‐node (alfalfa) stem segments, and leaves were removed. Total neutral‐sugar (TNS) concentration increased with maturity in stem and total herbage samples of both species and was greater in alfalfa than in red clover. In both species, TNS concentration in stems was nearly twice the concentration found in leaves. Furthermore, rhamnose, arabinose, and galactose proportions in TNS generally decreased in stems and total herbage with increasing maturity, whereas xylose and glucose proportions increased. Leaves of both species had greater rhamnose, arabinose, mannose, and galactose proportions than stems. Cell‐wall, CW lignin, and TNS concentrations were common variables in stepwise regression for both total herbage and stem models and accounted for nearly 95% of the variation of in vitro digestible dry matter (IVDDM). In leaves, TNS concentration explained more than half the variation in IVDDM. Compared with alfalfa leaves, red clover leaves had higher TNS concentrations and lower IVDDM. Relationships between individual neutral sugars and digestibility were inconsistent between leaves and stems. The high TNS concentration was more important in explaining the low digestibility of red clover leaves relative to alfalfa leaves than was lignin or CW concentration.
Genetic Models for F2 ✕ F2 and BC1 ✕ BC1 Interpopulation Crosses
Authors: Bernardo Rex , Johnson G. R. , Dudley J. W. , Meghji M. R.
Published: July 2010

Broadbase germplasm may be used to improve parents (I1 and I2) of an elite single cross. Composites (C1 and C2) may be crossed to each parent, followed by reciprocal selection either between the [I1 ✕ C1]F2 and the [I2 ✕ C2]F2 or between the [I1(I1 ✕ C1)]BC1 and the [I2(I2 ✕ C2)]BC1. To compare F2 and BC1 generations as foundation populations, expectations of F2 ✕ F2 and BC1 ✕ BC1 interpopulation means, half‐sib covariances (CovHS), and specific combining ability variances (VarSCA) were derived for a one‐locus, two‐allele model with partial and complete dominance. Whereas means are expected to be higher in the BC1 than in the F2 interpopulation cross, CovHS and VarSCA are expected to be two to seven and two to three times greater, respectively, in the F2 than in the BC1 interpopulation cross. In studies considering introgression of broadbase germplasm to improve the elite maize (Zea mays L.) single cross B73 ✕ Mol7H, grain moisture and plant and ear height data were consistent with these expectations. But for grain yield, VarSCA estimates in the F2 were inordinately small relative to those in the BC1 interpopulation cross. Because VarSCA is due to nonadditive genetic effects, more complex models involving unequal effects of multiple alleles, two‐locus epistasis, and modification of dominance were investigated. Grain yield data were consistent with a model in which dominance at a quantitative trait locus is expressed only in the presence of a modifier allele at a modifier locus. In this model, the modifier allele is fixed in both parents of the elite single cross but present in near‐zero frequencies in the composites.
Recurrent Selection for Groat Oil Content in Oat
Authors: Branson C. V. , Frey K. J.
Published: July 2010

An improvement in the groat (caryopsis) oil content of oat (Avena sativa L.) may lead to the development of oat as an oilseed crop. Three cycles of phenotypic recurrent selection for high groat oil content were conducted in an introgressed oat gene pool, constructed by combining high‐oil alleles from A. sativa with those of its wild progenitor, A. sterilis L Selection for groat oil content was applied to individual So plants, with recombination among progenies from the highest 10% to form an improved population. One year was required to complete each cycle of selection. Gain from selection was evaluated by field testing 100 random and 100 selected lines from each of the C0, C1, C2, and C3 populations. Selection increased groat oil content linearly at a rate of 9.26 g kg−1 per cycle, which resulted in a linear increase in oil yield of 21 kg ha−1 per cycle. The largest gain from selection for both traits occurred in the first selection cycle. Broad‐sense heritability and genotypic variance remained high and significant in all cycles, which suggests continuing gains in groat oil content from additional cycles of recurrent selection. Realized heritability for groat oil content was 0.68 ± 0.05. Of the 400 random lines evaluated, the top 10 lines for groat oil content were from the C3 population, the highest individual line having a groat oil content of 144.8 g kg−1. That some high oil oat lines were equivalent to check cultivars for all agronomic traits suggests selection for oil content had little effect on those traits.
Genetic Diversity among Peanut Cultivars
Authors: Knauft D. A. , Gorbet D. W.
Published: July 2010

An assessment of the genetic diversity among peanut (Arachis hypogaea L.) cultivars released in the USA would be useful to scientists working with this crop. This study was conducted to determine contributions from ancestral lines and coefficients of parentage (r) for peanut cultivars released in the USA. Pedigrees were constructed and examined to determine relative contributions of ancestral lines. In addition, r values were calculated for 820 pairwise combinations of 41 cultivars and mean genetic contributions of the ancestral lines were determined. Among runner market‐type peanuts, ‘Dixie Giant’ was a germplasm source in all pedigrees, ‘Small White Spanish‐l’ occurred in over 90% of the pedigrees, and the two lines contributed nearly 50% of the germplasm of runner cultivars. The r values among seven of the eight runner eultivars developed since the release of ‘Florunner’ in 1969 averaged 0.32. Inclusion of the eighth cultivar, Tifrun, which is only distantly related to the other seven, lowered the r value to 0.20. The Virginia market‐type cultivars had a more diverse genetic background, with only Dixie Giant and ‘Jenkins Jumbo’ contributing more than 10% of the germplasm. The r values for the Virginia cultivars released since 1969 averaged 0.21. The average r value for crosses between runner and Virginia market types was 0.16, while Spanish cultivars, with the exception of Tifspan, were unrelated to either runner or Virginia cultivars. The coefficients of parentage can be used by researchers conducting breeding, genetic, or physiological studies where knowledge of the genetic diversity of peanut cultivar backgrounds is important.
Terpenoid Aldehydes in Upland Cottons. II. Genotype‐Environment Interactions
Authors: Altman David W. , Stipanovic Robert D. , Benedict John H.
Published: July 2010

Cotton (Gossypium hirsutum L.) has unique secondary natural products, sesqui‐ and sesterterpenoid aldehydes, that have the potential to control phytophagous insect pests, but information on their inheritance has been limited to only one compound, gossypol (G). The objective of this study was to determine genetic and environmental variances and interactions, heritability, and genotypic stability for the major nonvolatile terpenoids in foliar pigment glands. A genotype‐by‐environment experiment, which included 14 genotypes having from normal to very elevated terpenoid content, was conducted at five diverse Texas locations over 2 yr. Flower buds at the third‐grown square stage and first nonglossy terminal leaves were sampled 3 wk after first bloom and analyzed by high performance liquid chromatography (HPLC) for G, p‐hemigossypol quinone (HGQ), and the heliocides H1, H2, H3, and H4. Aniline‐reaction measurements were made for total flower bud terpenoids. The HPLC data for location means showed differences between the high and low values ranging from eightfold for leaf HGQ to less than twofold for flower bud H2. Genetic ✕ environment variance components were less than genetic variance components in all instances and were generally very small. Error variance exceeded genetic variance only for HGQ, G, and H4 in leaves and for H4 in flower buds. Broad‐sense heritabilities averaged 0.46, 0.94,0.61, and 0.93 for leaves on a plotbasis, leaves on an entry mean‐basis, flower buds on a plot‐basis, and flower buds on an entry mean‐basis, respectively. Stability analyses gave regression coefficients from 0.06 to 2.11 (1.00 defined a stable genotype.) for high‐terpenoid lines, whereas commercial cultivars had values from 0.11 to 1.05. Our results indicated that plant breeders and geneticists can select for higher terpenoid levels if this goal is considered desirable in the broad context of increasing cotton host‐plant resistance.
Assessment of Barley Accessions PI 382313, PI 382474, PI 382915, and PI 382976 for Stem Rust Resistance
Authors: Jedel P. E. , Metcalfe D. R. , Martens J. W.
Published: July 2010

New sources of resistance to Puccinia graminis Pers. f. sp. tritici Erikss. and Henn. in barley(Hordeum vulgare L.) should be identified and incorporated into breeding programs to ensure the continued resistance of barley to this pathogen. The objective of this study was to identify resistance to stem rust in barley accessions from the USDA Wiebe collection and determine the relationship of this resistance to resistance conferred by the T gene. Four accessions, PI 382313, PI 382474, PI 382915, and PI 382976, were selected as having good field resistance at the Winnipeg Agriculture Canada Research Station, Glenlea rust nursery in 1986. The field resistance of these four accessions was reconfirmed in the 1987 rust nursery and was found to be as effective as, or more effective than, that conferred by T. Seedling and adult plant tests were conducted in controlled environments with six races (C5, C10,C 17,C 25,C 35, and C53). In seedling tests, PI 382313 was resistant or moderately resistant to all six races. Both PI 382474 and PI 382915 were moderately susceptible to C35 and susceptible to the other five races. The PI 382976 was moderately resistant to C35 and C53, and moderately susceptible or susceptible to the other races. In adult plant tests, PI 382474 was resistant to C35 and PI 382313 was resistant to C17. Both PI 382915 and PI 382979 displayed little resistance as adults to the six races. Genetics studies with PI 382313 indicated that the field resistance of this accession was conferred by a single dominant gene that was different from T.
Meiotic Instability of Tall Fescue ✕ Giant Fescue Amphiploids
Authors: Burner D. M. , Eizenga G. C. , Buckner R. C. , Burrus P. B.
Published: July 2010

Amphiploids of tall fescue (Festuca arundinacea Schreb.) and giant fescue [F. gigantea (L.) Vill.] have high forage quality but are meiotically irregular and have low seed yield. The objective of this study was to evaluate effects of generation advance and cytoplasm on meiotic behavior of tall fescue ✕ giant fescue amphiploid derivatives. Chromosome number and pairing, frequency of micronuclei, and pollen stainability were analyzed in 75 amphiploids developed from reciprocal hybrids of giant fescue ✕ tall fescue (including derivatives of annual ryegrass [Lolium multiflorum Lam.] ✕ tall fescue). Amphiploids represented five generations (C1–C5) of maternal half‐sib progenies in three cytoplasmic backgrounds (annual ryegrass, giant fescue, and tall fescue). Chromosomes were lost and meiotic irregularity increased over generations. Chromosome number at C1 averaged 2n = 83.5 (range 2n = 81 to 84) and at C5 averaged 2n = 74.9 (range 2n = 48 to 84). The frequencies univalents and trivalents increased linearly from C1 to C5 generations, as did the frequency of micronuclei at telophase (T) I and II. Conversely, ring bivalents, frequency of chiasmata, and percentage of daughter cells without micronuclei decreased linearly from C1 to C5 generations. Pollen stainability was relatively constant across generations despite chromosomes loss. Effects of cytoplasm were negligible, as significant differences were detected only for frequency of TII micronuclei. The population will probably regress to the hexaploid level (2n = 6x = 42) where it may be possible to select meiotically regular genotypes for cultivar improvement.
Grain Growth of Tall and Short Spring Wheat Genotypes at Different Assimilate Supplies
Authors: Winzeler M. , Monteil Ph. , Nösberger J.
Published: July 2010

The degree to which grain growth of wheat (Triticum aestivum L.) is influenced by environmental factors differs among genotypes. Two growth chamber experiments investigated the influence of assimilate supply on grain size in spring wheats. In Exp. 1 with two tall and two short genotypes, assimilate production of single plants was varied after anthesis by CO2 concentrations (1000 and 200 μL CO2 L−1) and by removing 56% of the flag leaf. Treatments had a greater effect on final grain size in the short than in the tall genotypes (range 30.4‐47.2 and 37.8‐42.4 mg/grain, respectively). Under high CO2, photosynthates accumulated as total nonstructural carbohydrates (TNC) in the stems of tall genotypes, indicating that the supply exceeded the demand of the growing grains. Experiment 2 tested the hypothesis that restricted grain growth in tall genotypes is due to a lack of assimilates, either during the last stages of floret development or the early stages of grain growth, resulting from sink competition of stem growth. The CO2 level varied during the 15 d preceding anthesis and the first 20 d after anthesis (1000 and 200 μL CO2 L−1). In plants grown at 1000 μL CO2 L−1 thereafter, the assimilate supply during floret development or early grain growth had no significant influence on final grain size. The TNC accumulated in the stem up to maturity, suggesting that grain growth was restricted by factors other than assimilates. It is concluded that the ability to increase grain weight under a high assimilate supply differs between spring wheat genotypes. In short genotypes, grain growth was less restricted as compared with the tall genotypes. Grain growth in tall genotypes was not limited by lack of assimilates during floret development or early grain growth.
Breeding Diploid Alfalfa for Regeneration from Tissue Culture
Authors: Ray I. M. , Bingham E. T.
Published: July 2010

Plant regeneration is necessary for most agricultural applications of tissue culture. Regeneration of alfalfa (Medicago sativa L.) from tissue culture has focused primarily on tetraploid genotypes (2n = 4x = 32). The simplified genetics of the diploid (2n = 2x = 16), however, is desirable for many aspects of alfalfa biotechnology. This study reports on the development of a diploid alfalfa population, Regen‐2x, that contains a high frequency of regenerable genotypes. Genes controlling regeneration were originally identified in five tetraploid individuals and were transferred to the diploid level using haploidy and triploid bridge crosses. The frequencies of alleles controlling regeneration were then increased by two cycles of recurrent selection. The original seed‐derived plants, which had served as donors for tissue culture and were capable of regeneration, were recombined in each cycle. This breeding strategy prevented the accumulation of somaclonal variation in the population while increasing the frequency of individuals able to regenerate from tissue culture. Ten percent of the base diploid population (Cycle 0) regenerated. Recurrent selection significantly (P < 0.025) increased the frequency of regenerating individuals to 33% and then 66% in Cycle 1 and 2, respectively. These data support the results of other studies that indicate regeneration from tissue culture is controlled by relatively few genes.
Quantitative Genetic Components Within Restricted Populations
Authors: Jiang Chang‐jian , Cockerham C. Clark
Published: July 2010

Breeders often work with populations with a restricted genetic base either from the maintenance of varieties as small finite populations or from the initiation of populations with a few individuals or inbred lines. It is important to know the consequences of these restrictions on quantitative variation in comparison to that for large noninbred populations. To accomplish this the quantitative genetic variation within restricted populations is formulated in terms of the quantitative genetic components in the noninbred ancestral population. Required to treat an additive, dominance and additive by additive model are six components: σ2a‐additive variance, σ2d‐dominance variance, d1‐covariance of additive and homozygous dominance effects, d2‐variance of homozygous dominance effects, h2‐ square of the inbreeding effect, and σ2aa‐additive by additive variance. Comparable components (starred, e.g. σ2a*) for restricted populations, as an average over replicates, are expressed as linear functions of the components in the ancestral population with coefficients of identity by descent measures. These results from operating directly on the effects and variances within populations for all the components confirm previous results from covariances of relatives for σ2a* and σ2d*. Examples of further self‐fertilization and of a few inbred founders are considered in some detail. In the latter case considerable simplification occurs in that all coefficients are functions of the coancestry coefficient. While it is informative to relate the quantitative genetic components in restricted populations to those in ancestral populations, there is no practical advantage over just defining the components for a specific population when attention is to be confined to that population.