bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversion of Male‐Sterile T‐Cytoplasm Maize to Male Fertility in Tissue Culture1
Authors: Umbeck Paul F. , Gengenbach Burle G.
Published: July 2010

This study was conducted to determine the inheritance of altered traits in plants regenerated from Texas male‐sterile cytoplasm (T) maize (Zea mays L.) tissue cultures. Plants were regenerated from AlSSTcms (rf1rf1;Rf2Rf2) tissue cultures grown on control media or on media containing different levels of streptomycin. Of 169 regenerated plants, eight expressed unexpected changes to male fertility and/or resistance to Helminthosporium maydis pathotoxin even though the cultures had not been selected for pathotoxin resistance. The male fertility and disease resistance traits had a cytoplasmic mode of inheritance. Two regenerated plants were male fertile and toxin susceptible, but their first generation progeny were either male fertile and resistant or male sterile and susceptible. Some regenerated plants apparently were chimeric for two cytoplasm conditions, one causing male fertility and toxin resistance and the other causing male sterility and toxin susceptibility. Mitochondrial DNA (mtDNA) was extracted from six variant lines and analyzed by restriction enzyme digestion and agarose gel electrophoresis. Five of the six variants were distinguishable from control A188Tcms (rf1rf1;Rf2Rf2) by virtue of an alteration(s) in a mtDNA sequence of about 6,600 base pairs (6.6 Kb). A 6.6 Kb fragment characteristic of A188Tcms (rf1rf1;Rf2Rf2) mtDNA was not detected in the five variant lines when mtDNA was digested with the restriction enzyme Xhol; however, no difference could be detected between the sixth variant line and A188Tcms (rf1rf1;Rf2Rf2). A possible relationship between the mtDNA changes and the cytoplasmically controlled changes to male fertility and toxin resistance is proposed.
Genetic Variability of Seed Yield and Reproductive Characters in Tall Fescue1
Authors: Nguyen H. T. , Sleper D. A.
Published: July 2010

Superior seed‐yielding ability in tall rescue (Festuca arundinacea Schreb.) is important during the seed multiplication phases of breeding new cultivars and under commercial seed production. Objectives of this study were to 1) determine genetic variability, genotype ✕ environment interactions, and heritabilities for seed yield and reproductive characters; 2) study interrelationships among those characters; and 3) predict genetic gain from selection. Fifteen parents were randomly chosen from a broad‐based population, and their half‐sib progenies were generated using a polycross mating design. All entries were evaluated for 10 seed production characters for 2 years at two locations. Genotype and genotype ✕ environment interactions were significant for most characters. Additive genetic variance accounted for a significant proportion of the total genetic variance for maturity score, number of panicles, panicle length, seed yield, and seed weight per panicle. Narrow‐sense heritability estimates on a phenotypic mean basis, using both variance component and genotypic parent‐offspring regression methods, were high for maturity score, number of panicles, panicle length, and seed yield; and medium for 100‐seed weight and seed weight per panicle. Predicted genetic gains per cycle of phenotypic family selection were 33, 45, 27, 34, and 14% of the population means for maturity score, number of panicles, panicle length, seed yield, and 100‐weight, respectively. Correlation analyses showed that early‐maturing plants had higher numbers of panicles with shorter panicles and higher seed yields. Increased seed yield and size could be expected as the result of selection for early maturity in this plant material.
Mixtures of Soybean Cultivars to Minimize Yield Loss Caused by Iron‐Deficiency Chlorosis1
Authors: Trimble M. W. , Fehr W. R.
Published: July 2010

Seed mixtures of soybean [Glycine max (L.) Merr.] Cultivars are an alternative to a pure stand of a high‐yielding susceptible or a lower‐yielding resistant cultivar for minimizing yield loss from iron‐deficiency chlorosis. Our objective was to determine the relationship between the yield of mixtures and the frequency of component cultivars that differ in their level of resistance to iron‐deficiency chlorosis. Seed of a highly resistant line A2 was mixed with each of four cultivars; ‘Weber’ (moderately resistant), ‘Wells’ (moderately susceptible), ‘Corsoy’ (susceptible), and ‘S1492’ (highly susceptible). The proportions varied by 10% increments from 90% A2 to 10% A2. The nine mixtures of each cultivar pair and a pure stand of each component were evaluated in Iowa on calcareous soil in replicated yield tests at seven environments. The cultivar pair ✕ component frequency interaction was highly significant because the yield of the mixtures varied with the amount of yield reduction sustained by the susceptible component. There were no significant differences in yield among frequencies for the A2‐Weber mixtures at any of the seven environments. The results indicate that there would not be a benefit from mixing a high‐yielding cultivar with moderate resistance and a lower‐yielding cultivar with a high level of resistance. The average percentage of A2 required in a mixture to obtain a yield within 10% of a pure stand of A2 was 20% for A2‐Wells, 33% for A2‐Corsoy, and 39% for A2‐S1492. Productivity of fields planted to a seed mixture, resistant cultivar, or susceptible cultivar depends on the percentage of calcareous area in the field, the yield difference between the resistant and susceptible cultivars on noncalcareous soil, and the level of chlorosis susceptibility for the cultivars being considered. Procedures are discussed for calculating when a cultivar or a mixture would be most productive.
Ontogeny of Lipid Bodies in Developing Soybean Seeds1
Authors: Adams Clifford A. , Norby Shong Wan , Rinne Robert W.
Published: July 2010

Cells of developing soybean, cultivar ‘Wells’ (Glycine max (L.) Merr.), cotyledons contained plastids and lipid bodies at the earliest stage investigated, 15 days after flowering. Lipid bodies seemed to arise directly in the cytoplasm and their proximity to plastids maybe coincidental. By 34 days after flowering lipid bodies increased dramatically accompanied by a massive proliferation of rough endoplasmic reticulum. In some instances this rough endoplasmic reticulum was closely associated with lipid bodies but in other cases there was no close association. In maturing seeds, plastids were frequently seen to contain lipid bodies which may indicate a loss of plastid integrity. Mature seeds contained numerous discrete lipid bodies which stained uniformly and had a half‐unit membrane border. A possible route for lipid body ontogeny consistent with the ultrastructural observation is that fatty acids are just synthesized in the plastids. Possibly then the fatty acids are transported and assembled into triglyceride molecules by the rough endoplasmic reticulum and released into the cytoplasm. Also the proteinaceous material associated with the lipid body membrane probably originate from the endoplasmic reticulum.
Genotype ✕ Environment Interaction Analysis for Yield in Alfalfa1
Authors: Hill R. R. , Baylor J. E.
Published: July 2010

A trial with 49 entries of alfalfa, Medicago sativa L., was evaluated for total season yield under two harvest managements for 3 years at two sites. Data from the trial series formed a base for which methods of analysis of genotype ✕ environment interaction for perennial forage crops were compared. The methods of analysis included: a) routine multifactor analysis of variance with sites, managements, years, and entries as the main effects; b) linear regression of individual entry means on the mean of all entries in each environment as well as linear regression with the ith entry eliminated from the environmental mean; and c) an orthogonal contrast analysis that partitioned the variation over environmentfso r each entry into sources duet o years, sites, and managements and all possible interactions between these factors. Entries, all the two‐factor interactions, and the site ✕ management ✕ entry interaction were significant sources of variation in the analysis of variance. There was significant variation in correlations among pairs of entries, and regression analysis did not provide a simple interpretation of the observed responses of genotypes to different environments. The orthogonal contrast analysis revealed that entries varied in their response to years (age of stand), sites, and managements. Entries that increased in yield relative to the average of all entries in the trial as the stand aged all had moderate or higher levels of resistance to Colletotrichum trifolii Bain (anthracnose) and Fusarium oxysporum Schlect. f. medicaginis (Welmer) Snyd. & Hans. (Fusarium wilt). We concluded that the orthogonal contrast analysis was easier to interpret than regression on environmental means for analysis of genotype ✕ environment interactions in perennial crops such as alfalfa, especially when a pattern such as the response to age of stand was present and could not be detected by the regression analysis.
Heterosis in Testcrosses of 27 Exotic Peanut Cultivars1
Authors: Isleib T. G. , Wynne J. C.
Published: July 2010

A study was conducted to determine the extent of and genetic basis for heterosis in crosses between 27 exotic peanut (Arachis hypogaea L.) cultivars and an adapted virginia breeding line. Because their subspecific taxonomy was not always clear, principal components were used to cluster the exotic parents into five morphologically distinct groups roughly corresponding to the botanical divisions of the species. Heterosis (measured as the deviation of F1 performance from the midparent) was observed for pod yield, pod size parameters, seed yield and other traits. Heterosis up to 19% above the higher parent occurred for pod size and length. A significant portion (27 to 68%) of the variability in heterotic effects was attributable to difference among the parental groups with generally higher levels expressed in intersubspecificcrosses. Heterotic deviations were broken into two components reflecting the relative contributions of dominance and epistasis to nonadditive genetic variation. For pod and seed yield and pod length, dominance was the more important source while epistasis was more important for pod and seed number and meat content. The two sources made approximately equal contributions to heterosis for pod and seed size. The degree of genetic divergence between exotic parents and the adapted line was estimated by a Euclidean distance based on the vegetative and reproductive characters used in the principal component analysis. For characters exhibiting more dominance, the relationship of heterosis to divergence between parents was linear and increasing. The relationship was curvilinear for traits largely influenced by epistasis. An optimum level of divergence was detected for pod number only.
Differences Between Reciprocal Crosses of Maize for Kernel Growth Characteristics1
Authors: Poneleit C. G. , Egli D. B.
Published: July 2010

Measurement of the length of the grain filling period may become a useful estimator of the yield potential of maize (Zea mays L.) breeding selections, but differences between reciprocal crosses could confound early generation evaluations. The objective of our study was to determine the existence and nature of reciprocal effects for effective filling period (EFP) and kernel growth rate. Four inbred lines were self‐ and cross‐pollinated in all possible combinations and their progenies were self‐pollinated to provide reciprocal genotypes for evaluation. The genotypes were grown in randomized complete block designs near Lexington, Ky. for 2 years. Reciprocal differences among the F1 kernel genotypes were found for both EFP and kernel growth rate. Maternal effects of inbred plants on F1 kernel genotypes were indicated for EFP but not for kernel growth rate where dosage and dominance effects were present. The F2 generation kernel analysis indicated that the observed reciprocal differences were not of cytoplasmic origin. Measurements of pericarp weight indicated that the kernel pericarp did not restrict kernel size. EFP's of F1 kernel genotypes were often greater than those of homozygous kernel genotypes and may have resulted from greater potential of the F1 genotypes or genetic restrictions of the homozygous genotypes. Dominance, as a result of gene dosage in the endosperm, was observed for kernel growth rate and could have been interpreted as maternal influences had all genotypes not been examined. Genetic analysis of F2 means showed that EFP and kernel growth rate expressed heterosis in the F2 kernel generation. Our data suggested that maternal influences are possible on the expression of EFP and that reciprocal differences for kernel growth rate can be caused by dosage effects in the kernel endosperm. Either effect dictates that control of pollination is needed for accurate evaluation of EFP.
Stem Diameter Variations in Cotton under Field Conditions1
Authors: Gensler W. , Diaz‐Munoz F.
Published: July 2010

Stem diameter variations are a potentially useful indirect measure of the water status of the cotton (Gossypium hirsutum L.) plant under field conditions. The object of this study was to determine the information content in the stem diameter variations and the effects of irrigation and rainfall on these variations. The diameter was measured on a continuous basis for extended time periods for three seasons using linear variable differential transformers. The results indicate that the maximum differential diameter is closely correlated with the shape of the diameter‐time curve. The maximum and minimum diameters occur at −5.76 ± 0.29 h and +2.93 ± 0.41 h relative to solar noon. The diameter varied from 10 to 25% of its maximum contractile value during an extended measurement period. A temporary positive expansion followed rainfall and a long term positive expansion followed irrigation.
Pearl Millet and Sorghum Pollen Tube Growth in Pearl Millet Gynoecia of Different Ages1
Authors: Reger Bonnie J. , Sprague Jacqueline James
Published: July 2010

The primary barrier to hybridization of pearl millet [Pennisetum americanum (L.) Leeke] with sorghum [Sorghum bicolor (L.) Moench] is arrest of pollen tube growth within the gynoecium. However, pollen tube growth in this cross is variable. This paper reports the effect of gynoecium age of pearl millet on pearl millet and sorghum pollen tube growth. Pearl millet stigmas were receptive to pollen immediately upon emergence and remained receptive to pollen germination and pollen tube penetration until abscission. Pearl millet pollen tubes grew normally in gynoecia having stigmas emerged for less than 4 days (younger gynoecia) at pollination, and fertilization occurred. Pollination of stigmas emerged for more than 4 days (older gynoecia) resulted in inhibition of pollen tube growth within the gynoecium. In contrast, sorghum pollen tube growth increased significantly in older vs. younger gynoecia. Sorghum pollen tubes in the ovary increased from 4% in younger to 22% in older gynoecia. Apparently the internal environment of pearl millet gynoecia changes with age. These changes appear to alter the pollen tube transmitting tract in the gynoecium making it inhibitory to pearl millet pollen tubes and less inhibitory to sorghum pollen tubes.
Duration and Inheritance of Leaf Initiation, Spike Initiation, and Spike Growth in Barley1
Authors: Kitchen Boyd M. , Rasmusson Donald C.
Published: July 2010

Three preanthesis growth periods were studied in barley (Hordeum vulgare L.) in order to identify genetic variation and estimate heritability for the three periods. Duration of the three periods, leaf initiation, spike initiation, and spike growth, was determined in a field experiment by dissecting and observing shoot apices. In a comparison of 10 cultivars, mean duration of the leaf initiation, spike initiation, and spike growth periods was 10.2, 9.6, and 20.6 days, respectively. Genetic diversity was found for each of the three periods with cultivar means ranging from 4.9 to 13.6, 7.3 to 12.2, and 17.1 to 23.5 days. Cultivars with similar duration of the vegetative period exhibited modest but significant differences in duration of the three periods. Cultivar means for rate of spike initiation ranged from 1.8 to 2.5 nodes per day; these differences were not significant. Duration of leaf initiation was correlated with leaf number; duration of spike initiation with leaf area, spikelet primordia number, and kernel number; and duration of spike growth with leaf area, height, spikelet primordia number, spikelet primordia survival, and kernel number. Parent‐offspring heritability estimates were 0.43, 0.60, and 0.68 for duration of the leaf initiation period in three segregating populations. Inconclusive evidence was obtained for a major gene affecting duration of the leaf initiation period in two of the three populations. Genetic variation was nonsignificant for duration of the spike initiation period in the three populations and heritability estimates were not different from zero. Estimates of heritability for duration of the spike growth period were 0.59, 0.23, and 0.74. The correlations involving leaf and kernel number with duration of two of the growth periods indicate possible benefits from breeding for optimum duration. While conjecture on the optimum duration of the three growth periods is probably not warranted, genetic variation in duration of the growth periods might be used in breeding for increased yield via obtaining durations better suited to specific environments.
Phosphorus Fertilizer Response in Experimental Alfalfas selected for Different Phosphorus Concentrations1
Authors: Hill R. R. , Lanyon L. E.
Published: July 2010

Six alfalfa, Medicago sativa L., synthetics from parents selected for high P concentration (HP synthetics) and four from parents selected for low P concentration (LP synthetics) were evaluated for first harvest forage yield and mineral concentration at two soil P levels at each of two locations. The experiment also included four synthetics from parents selected for low lignin concentration and four check cultivars. Seed of the experimental synthetics were produced by intermating a sample of plants from full‐sib families that had been selected for forage P or lignin concentration in a previous generation. The experiment was conducted to determine if the two‐parent synthetics from the selected full‐sib families would maintain their relative ranking for P concentrations and if an interaction with soil P level could be detected. Yields of all entries in the experiment were less than normally observed for first harvest alfalfa in the region. The synthetics differed significantly for yield, but average yield of the HP synthetics was not different from that of the LP synthetics. Average forage P concentration of the HP synthetics was significantly greater than that of the LP synthetics at both soil fertility levels. Differences between the HP and LP synthetics were less than between their respective parental groups. Interactions between synthetics and P soil fertility level were not detected. The HP synthetics had a forage P concentration much less than that recommended for the diet of a moderately producing dairy cow. Thus successful selection for increased P concentration in the forage may not result in forage (hat meets animal requiremnts for P.
Breeding Low‐Tannin Sericea. III. Variation in Forage Quality Factors Among Lines1
Authors: Donnelly E. D. , Anthony W. B.
Published: July 2010

An experiment was conducted to determine forage quality in elite low‐tannin sericea lespedeza [Lespedeza cuneata ( Dumont) G. Don.] lines that had shown field resistance to Rhizoctonia foliar blight. Results given below are based on means of three hay cuttings. The range in tannin and crude protein (CP) content for 54 low‐tannin lines was 2.5 to 3.2%, and 15.2 to 18.4%, respectively. The range in in vitro digestible dry matter (IVDDM) for 75 low‐tannin lines was 36.8 to 67.0%. Some low‐tannin lines (2.7% tannin) were as low in IVDDM as the high‐tannin control line which averaged 4.9% tannin and 38% IVDDM. This indicated the presence of a factor or factors in addition to tannin affecting IVDDM. Conversely, the low‐tannin line highest in CP (18.4%) was among the highest in IVDDM(63%). The IVDDM was significantly correlated with CP for 54 low‐tannin lines, indicating that IVDDM increased as CP increased. Sugar content varied among 27 low‐tannin lines from 7.6 to 13.0%. Data indicate that forage quality of sericea can be increased by developing low‐tannin lines that are high in CP, sugars, and IVDDM.
New Sources of Resistance to Root‐Knot Nematodes among Primitive Cottons1
Authors: Shepherd Raymond L.
Published: July 2010

Presently, Auburn 634 RNR and related cottons are the only germplasm in upland cotton (Gossypium hirsutum L.) with extremely high resistance to root‐knot nematodes (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood]. Genetic vulnerability could result from using only this one source for breeding resistant cultivars. The purpose of this study was to evaluate primitive race stocks of G. hirsutum to identify new, genetically diverse sources of RKN resistance, and to compare the new sources with those now in upland cottons. Of 471 primitive race stocks evaluated, 18 (3.8%) were resistant. None were as resistant as Auburn 634 RNR, although several approached it. Number of eggs produced on the eight race stocks having the highest resistance ranged from 2.8 to 5.5 times fewer than were used initially to inoculate them. Resistance was widely distributed among stocks of different races (originating from the same and different geographic areas), indicating the potential diversity of the resistant germplasm. Evidence is presented that RKN resistance should be relatively stable over time and should control RKN across many geographic regions of the world.
Leaf and Tiller Identification on Wheat Plants1
Authors: Klepper Betty , Rickman R. W. , Belford R. K.
Published: July 2010

Identification of leaves and tillers on wheat (Triticum aestivum L. em. Thell.) plants and determination of their relative stage of leaf development is useful in detecting environmental stresses in seedlings. This paper describes a number of criteria which can be used to identify leaves, tillers, and subtillers on cereals when lower leaves have been lost.
Fossil Energy Requirement of Protein Produced by Dry Beans1
Authors: Williams William A. , Bluestein Claudia , Tucker Carl L. , Lyons James M.
Published: July 2010

Fossil energy cost of the cultural inputs for production of dry beans (Phaseolus vulgaris L.), a cheap source of food protein, were highest for fertilization followed in declining order by crop establishment, machinery, irrigation, harvesting, weed control, insect control, transportation, and disease control. The average energy requirement was 20.6 GJ ha−1 and 10.4 MJ kg−1 of beans produced, and protein energy output/energy input equalled 0.38. Dry beans grown in California compared favorably in protein produced per hectare and fossil‐energy use efficiency with other crops widely grown in the USA.
Genetic Improvement in Malting Barley Cultivars Since 19201
Authors: Wych R. D. , Rasmusson D. C.
Published: July 2010

The constraints imposed by the requirement of acceptable malting and brewing quality in new barley(Hordeum vulgare L.) cultivars, and the resultant use of a narrow germplasm base make the genetic gains in breeding of Midwestern malting barleys of special interest. In this study cultivars which have dominated the malting barley acreage in the tri‐state area of Minnesota and North and South Dakota since 1920 were evaluated to determine the amount of genetic gain which has been made in yield, agronomic and quality traits. Six cultivars were evaluated for 18 traits in seven trials conducted at Crookston and St. Paul, Minn. during the years 1978 to 1982. Four of the six cultivars—‘Kindred’ ‘Traill,’ ‘Larker,’ and ‘Morex’—were in turn the dominant cultivar in the tri‐state malting barley area. Cultivars differed significantly for 15 of the 18 traits. Grain yield of Morex was 51% greater than that of ‘Manchuria,’ the oldest cultivar; the average annual increase in grain yield measured from Manchuria to Morex was 0.9%. However, regression analysis indicates that for the past 40 years, the time period in which serious breeding efforts have been made in the tri‐state area, yield gains have been nearly linear with an average annual increase of 2%.During this time grower yields have nearly doubled and 73% of this increase can be attributed to improved cultivars or genetic improvement. Increases in grain yield of the cultivars were attributed to improvements in lodging resistance, an increase in harvest index( HI) from 0.31 to 0.40, and increases kernel weight and spike number. Significant improvements were achieved for plump kernels, malt extract, alpha amylase, diastatic power and disease resistance. Nitrogen harvest index also was higher in the newer cultivars. The results indicate that sizable yield gains, as well as gains for other traits, can be made within a relatively narrow germplasm base.
Evaluation of Avena sativa L./A. fatua L. Progenies for Agronomic and Grain Quality Characters1
Authors: Luby J. J. , Stuthman D. D.
Published: July 2010

The F4‐derived lines from eight Avena sativa L./A. fatua L. crosses were evaluated with their parents and check cultivars to determine whether A. fatua might contribute useful variation for improving agronomic and grain quality characters in cultivated oats. Certain A. fatua lines should be able to contribute genes for increased grain yield to A. sativa All crosses produced lines that equaled or exceeded A. sativa parents or check cultivars. Progeny means for grain yield were related to the heading date and grain yield of A. fatua parents. High groat oil percentage in A. fatua parents( 9.1 to 11.5%a) and progenies, and high heritability estimates(88 to 98%), indicated A. fatua could be used to increase oil levels in cultivated oats. Though parents did not differ for groat protein percentage, all crosses had variation among lines indicating A. fatua may have different genes for this trait than A. sativa. Groat oil percentage and groat protein percentage tended to be negatively correlated. However, crosses with high means for botht raits were identified. In contrast to the relationships of their parents, progeny lines with dark seed color or shattering habit were earlier, shorter, and higher for harvest index, and lower in groat oil percentage than light‐colored or nonshattering lines. Dark seed color and shattering were also associated with lower groat percentage and lower groat protein percentage. Few, if any, A. sativa/A. fatua progeny were even minimally acceptable for seed quality, height, maturity, and crown rust (Puccinia coronata Cda.f.sp. avenae Fraser and E. Led.)resistance. Further crossing to appropriate A. sativa genotypes would help alleviate these deficiencies.
Response of an F1 Interspecific (Gossypium Hirsutum L. ✕ G. Barbadense L.) Cotton Hybrid to Plant Density in Narrow Rows1
Authors: Palomo Arturo , Davis Dick D.
Published: July 2010

The production of cotton hybrids and the narrow‐row high plant population cultural system are two approaches to counteract increasing costs of cotton production. We conducted research during the 1979 and 1980 seasons to evaluate the yield response of an adapted high yielding prototype interspecific cotton hybrid (NX‐1) to three plant densities 40,000, 80,000 and 120,000 plants/ha) in 68‐cm rows. A fertile isoline (B.line) the higher yielding parent and ‘Acala 1517‐75’ were included as checks. Field treatments were distributed in a split‐plot arrangement with four replications on a soil classified primarily as a fine, montmorillinitic, thermic typic torrert. NX‐1 and the Bline commenced blooming 9 days earlier than Acala 1517‐75. Cumulative flower production curves for the first 3 weeks of blooming showed NX‐1 and the B‐line were significantly superior in blooming rate to Acala 1517‐75. Flower production also increased with increasing plant density. Independently of year or plant density, lint yields of the hybrid were significantly superior to those of the check genotypes. On the average, NX‐1 yielded 41 and 56% more lint than the B‐line and Acala 1517‐75, respectively. The highest yield was obtained with 120 000 plants/ha and the lowest with 40 000 plants/ha. The genotype ✕ plant density and year ✕ plant density interactions were not significant. The maximum yield potential of this hybrid was not necessarily obtained with 120 000 plants/ha. Boll traits and fiber properties were not influenced by plant densities. Compared to the checks, NX‐1 is characterized by smaller bolls with fewer seeds, lower lint percentage, and by a higher seed index. NX‐1 fiber is equal to that of Acala 1517‐75 in fineness, but is longer and stronger.
Indications from a Diallel Study for Interracial Maize Hybridization in the Corn Belt1
Authors: Gerrish E. E.
Published: July 2010

Yields and yield heterosis were investigated in a diallel study involving six six‐line maize (Zea mays L.) synthetics consisting of three Corn Belt dents, a Cateto flint, and an adapted version each of Mexican dent (predominantly Tuxpeno) and Carribean flint/dent (Coastal Yellow Flint‐ETO‐Costeno). The three exotic synthetics yielded significantly less than the three Corn Belt dent synthetics (5.56 to 6.69 Mg ha−1 vs. 7.01 to 7.36 Mg ha−1, respectively). Crosses among synthetics ranged in yield from 7.31 to 8.27 Mg ha−1. Significant general combining ability effects indicated that additive effects were of major importance. Heterotic responses of these crosses (relative to midparent) were in the range of 112 to 115% within Corn Belt dent, 111 to 117% between the three Corn Belt synthetics and the Mexican and Caribbean synthetics, and 112% between the Mexican and Caribbean synthetics. Cateto differed from the other synthetics with a heterotic range of 123 to 128%. This pattern suggested a rather close affinity among Corn Belt, Mexican, and Carribean germplasms. The exotics lacked sufficient heterotic responses in their hybrid combinations to excel, and very seldom to equal, Corn Belt ✕ Corn Belt combinations. Little support was offered for maintaining Corn Belt dent and the other three major exotic racial complexes separately for use in interracial combinations. Rather, this evidence, plus considerations of Corn Belt dent origins, supported an incorporation approach where distinctly diverse races, such as Cateto, are combined separately with the more diverse elements of Corn Belt dent, whose derived forms can serve in recurrent selection programs.
Recurrent Selection for Grain Protein Percentage in Hard Red Spring Wheat1
Authors: Löffler C. M. , Busch R. H. , Wiersma J. V.
Published: July 2010

Two cycles of recurrent selection for grain protein percentage were evaluated, and direct response in grain protein percentage and correlated responses for other traits were determined. Ten hard red spring wheats selected for grain protein percentage and other traits were intermated to form the initial population (C0). Selection for grain protein percentage was applied on F3 lines in C0 and Cl, and 20 to 25 lines were selected for intercrossing to initiate the next cycle. The proportion of each population selected for Cl and C2 were 7.5 and 4% respectively. The C0 and C2 bulks were grown with the original parents in four environments to evaluate gain. Also, 80 F3‐derived F5 lines from C0 and 80 F3‐derived F7 lines from C2 were evaluated at two locations to provide an estimate of gain from selection. Grain protein percentage increased 0.5 percentage points per cycle as measured by the lines, and 0.35 percentage points per cycle when measured on the bulks. Among the 160 lines tested, the highest 20 for grain protein percentage were from C2. Heritabilities for all traits varied only slightly from C0 to C2. Generally, other traits were unaffected by the selection procedure, with the exception of plant height of the bulks and mean grain yield of the lines, both being reduced from C0 to C2. Recurrent selection was effective in increasing grain protein percentage in this population, and thus could be used in germplasm development. multiple trait selection or selection for correlated traits might result in gains in grain protein percentage while maintaining grain yields.
Resistance of Hordeum spontaneum Collected in Israel to Infection with Erysiphe graminis hordei1
Authors: Moseman J. G. , Nevo E. , Zohary D.
Published: July 2010

The progenitor of barley, Hordeum spontaneum C. Koch, is being used extensively for developing improved barley (H. vulgare L.) cultivars. In this study, sites in Israel were identified with H. spontaneum plants resistant or moderately resistant to Erysiphe graminis DC Ex Merat. f. sp. hordei. (Em. Marchal), which incites the disease barley powdery mildew. The sites represent the range of ecological and environmental conditions and of genetic diversity and morphology of plants in Israel. The three cultures of E. graminis hordei, 64.54, 59.11, and R1, used to screen the accessions, possessed the virulence genes corresponding to most of the known resistance genes to that pathogen in barley. Eighty‐nine accessions were identified as resistant to all three cultures, and 180 accessions as at least moderately resistant. Sixty‐three accessions were resistant to one set of the cultures and moderately resistant to the other cultures suggesting that those accessions may have more than one gene conditioning their resistance. All of the accessions collected in sites in the Galilee, Northern Coastal Plains and Judean Highlands where the pathogen is usually present were resistant or moderately resistant to all three cultures of the pathogen. No resistant or moderately resistant accessions were obtained from sites in the Negev or on Mt. Hermon where the pathogen is seldom observed. Relationships between resistance to E. graminis hordei; genetic diversity and morphology of H. spontaneum plants, and the ecological and environmental conditions at specific sites are being analyzed to identify sites with plants having the maximum disease resistance and genetic diversity. The information will be used in planning future plant germplasm explorations.
Effect of Wheat Vernalization on Rhopalosiphum padi L. Survival1
Authors: Chen B. H. , Foster J. E. , Ohm H. W.
Published: July 2010

Four wheats, three Triticum aestivum L. em. Thell. and one T. turgidum L., vernalized and nonvernalized, were evaluated for response by the bird‐cherry oat aphid, Rhopalosiphum padi L. Results showed that aphids on both vernalized and nonvernalized ‘Abe’ seedlings had better survival rates, higher fecundity, and more nymphs molting to adults than those of ‘Caldwell’ wheat seedlings. Abe was susceptible to R. padi and Caldwell had moderate resistance. Resistance rankings of these two cultivars were not affected by vernalization, whereas the rankings of‘Elmo’ and CI 17647 changed. Because the aphid performance on Elmo and CI 17647 seedlings was not consistent, these two wheats could not easily be classified as resistant or susceptible to R. padi.
Comparative Fertility and Seed Yields of Parental Bermudagrass Clones and their Singlecross F1 and F2 Populations1
Authors: Kenna M. P. , Taliaferro C. M. , Richardson W. L.
Published: July 2010

Seed increase of hybrid Cynodon dactylon (L.) Pers. varieties could be facilitated if the F1 or subsequent generations were used as intermediate classes in a conventional increase system. A 2‐year study was conducted to 1) ascertain the feasibility of utilizing F1 or F2, or both, generations as pedigreed classes in a seed increase system by comparing their seed yield and fertility with parental clones, and 2) compare F1 singlecross populations with a five‐parent synthetic (Syn‐1) for fertility and seed yield. Plant materials included: five Oklahoma clonal bermudagrass accessions (9945, 9959, 12156, SS‐16, and SS‐21), three F1 singlecross combinations (9945 ✕ 12156, 9959 ✕ 12156, and SS‐16 ✕ SS‐21), and an F2 of each F1. A five parent syn‐1 generation polycross of clones 9959, 10978‐b, 12156, and F1 plants of the respective crosses 9959 ✕ 10978‐b and 9959 ✕ 12156) was also included in the test. The percentages for self‐pollinated (SP) seed set (range 0.4 to 3.6%) further demonstrate the relatively high degree of self‐incompatibility for bermudagrass plants. The percentages for open‐pollinated (OP) seed set (range 4.7 to 44.6%) and OP seed yields (range 20.8 to 337.8 kg ha−1) were significantly correlated (r = 0.52) and lower than values reported previous studies. Seed yields and percent OP seed set of the 9945 ✕ 12156 and 9959 ✕ 12156 F1 and F2 populations equaled or exceeded the yields of their respective clonal parents during each of the 2 years. The LCB Syn‐1 population had relatively high OP seed set and seed yields but its performance did not exceed that of the best clonal parent (9959) or singlecross F1 population (9959 ✕ 12156). The results indicate that F1 singlecross combinations such as 9945 ✕ 12156 and 9959 ✕ 12156 can be used for the establishment of foundation seed increase plantings without sacrifice of seed yields.
Measurement of Short‐Term Root Growth by Prestaining with Neutral Red1
Authors: Schumacher T. E. , Smucker A. J. M. , Eshel A. , Curry R. B.
Published: July 2010

A root staining procedure is described for measuring root growth during short term treatment periods. The vital stain, neutral red chloride, was used to stain roots in vivo. White root growth occurring after the staining period was easily differentiated from the stained portion of the pretreated root system. The staining treatment did not significantly alter plant growth or root respiration rates. The neutral red was primarily confined to cell walls of the cortex for the short term studies reported. Use of this or similar staining techniques combined with image processing equipment promises to provide a suitable method for rapid, inexpensive, and quantitative measurements of root responses to short term treatments.
Differential Recovery Among Cotton Genotypes Following Early‐Season Defoliation1
Authors: Smith C. Wayne , Varvil J. J.
Published: July 2010

An objective of many cotton (Gossypium hirsutum L.) breeding programs is the development of faster fruiting or earlier maturing cultivars. Such cultivars may allow producers to avoid production problems associated with early planting or late harvest as well as aid in disrupting the parallel buildup of certain pests with increased fruit load. Three cotton genotypes exhibiting different genetic maturities were evaluated over a 3‐year period to determine degree and speed of recovery from earlyseason defoliation, simulating stress due to hail damage. Arkugo 4, a fast‐fruiting strain; ‘DES 56’, a moderately early‐maturing, mid‐South cultivar; and ‘Deltapine 61’ (DPL 61), a full‐season, mid‐South cultivar were defoliated immediately above the first true‐leaf node when at the V5 and R2 stages of growth. A nondefoliated control of each genotype was included. When compared as a percent of nondefoliated controls (to remove the confounding effects of yield potential), the faster fruiting Arkugo 4 was not significantly lower yielding than its control when defoliated at the V5 stage in 1980 and 1981. Defoliation of DES 56 and DPL 61 at stage V5 caused a significant decrease in yield each year. Defoliation of all genotypes in all years at the R2 stage, except for Arkugo 4 in 1982, reduced or further reduced yield below that of defoliation at the V5 stage. Arkugo 4 also recovered more rapidly than DES 56 or DPL 61 following defoliation at both growth stages in 1980 and 1981, but not in 1982. These data indicate that yield‐competitive, fast‐fruiting cultivars have the potential to recover from early‐season stress more rapidly and to a greater degree than moderately early‐season or full‐season, mid‐South cultivars.
Reproductive Characteristics of Hexaploid Alfalfa Derived From 3x ✕ 6x Crosses1
Authors: Smith S. E. , Murphy R. P. , Viands D. R.
Published: July 2010

Fertility and cytology were studied in hexaploid alfalfa (Medicago spp., 2n=6x=48) derived from 3x ✕ 6x crosses. The 3x and 6x parents originated from Medicago saliva ssp. sativa L. (4x), M. sativa ssp. caerulea Schmalh. (2x) and M.falcata L, (2x). A higher percentage of hexaploid plants was produced in 3x ✕ 6x crosses where the 6x parent was derived from a presumably spontaneous hexaploid than in those crosses where the 6x parent was produced by colchicine treatment. All hexaploids derived from 3x ✕ 6x crosses were less fertile than tetraploid checks, but modest improvements in fertility were observed after two cycles of recurrent selection for hexaploidy. However, selection for hexaploidy had no significant effect on chromosomal stability. Hexaploid plants had a higher percentage of pollen mother cells (PMC) with laggards and more laggards within those PMC's than did tetraploids. When laggard frequencies were standardized relative to ploidy, no difference was observed between 6x and 4x materials for the mean number of laggards present in those PMC's having laggards. Hexaploid meiotic irregularity was positively associated with low fertility. The possibility was discussed that low levels of heterozygosity may be associated with meiotic irregularity and reduced fertility in the hexaploids studied.
Potential of Breeding for Ethanol Fuel in Sugarbeet1
Authors: Doney Devon L. , Theurer J. Clair
Published: July 2010

Sugarbeet (Beta vulgaris L.) has been considered as a prime candidate for ethanol fuel production. Breeding for ethanol fuel might be quite different than breeding for sucrose crystallization. Quality (high sucrose concentration and low amino N, sodium, and K concentration), which is essential for sucrose crystallization, is unimportant in the fermentation process. Increases in total sugar production might be more easily and rapidly achieved if selection were for fermentable sugars rather than for sucrose crystallization. This research was undertaken to evaluate the potential of breeding for ethanol fuel production in sugarbeet. Selections were made in a genetically broadbase population developed from the world collection of sugarbeet maintained at Ames, Iowa. One new polycross selection, g241, made for total fermentable sugar yield, ignoring quality factors, produced as much or more fermentable sugar (potential alcohol) a widely grown commercial sugarbeet hybrid, Mono‐Hy D2. This new population was low in sucrose concentration and high in impurities (amino N, sodium, and K), which would make it unacceptable for sucrose crystallization but promising as germplasm for the development of beets for ethanol fuel. This high fermentable sugar yield, achieved with minimal breeding effort in a highly heterozygous population, suggests that continued progress is possible. Higher fermentable sugar yields must, however, be sufficient to offset the cost of handling the additional root yields to be economically practical.
CO2 Fixation in Alfalfa and Birdsfoot Trefoil Root Nodules and Partitioning of 14C to the Plant1
Authors: Maxwell C. A. , Vance C. P. , Heichel G. H. , Stade S.
Published: July 2010

Nonphotosynthetic CO2 fixation by root nodules of legumes may provide carbon skeletons for assimilation of symbiotically fixed N2. However, the products formed by this process and their physiological significance in perennial legumes is poorly understood. Therefore, the objectives of this study were to determine if nonphotosynthetic CO2 fixation by root nodules contributes carbon for the assimilation of fixed N2 in alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.) and if assimilation products are partitioned to different plant organs. Effective alfalfa nodules excised from or attached to roots had apparent 14CO2 fixation rates of 50 to 80 μg CO2 kg‐1 s‐1 (dry weight) at 0.0012 to 0.0038 mole fraction CO2. Nodule CO2 fixation rates increased six‐ to seven‐fold as ambient CO2 was raised from 0.0038 to 0.0663 mole fraction. These rates were double to triple those of comparably treated nodules of ineffective alfalfa and those of birdsfoot trefoil. Respiration rates of nodules (3 to 4 mg CO2 kg‐1 s‐1) were 10 to 100‐fold higher than 14CO2 fixation rates of nodules. This finding suggests that attached nodules normally function at saturating CO2 levels and may fix up to 1600 μg CO2 kg‐1 s‐1 when concurrent 14C export to roots and shoots is accounted for. Pulse chase experiments with 14CO2 combined with nodule and xylem sap analysis demonstrated the initial products of root and nodule CO2 fixation were organic acids. However, the export of fixed 14C from effective nodules was primarily in the form of amino acids. In contrast, nodule and/or root fixed 14C in ineffectively nodulated alfalfa and denodulated effective alfalfa and birdsfoot trefoil was transported primarily as organic acids. Aspartate, asparagine, alanine, glutamate, and glutamine were the most heavily labeled compounds in the amino acid fraction of both effective alfalfa and birdsfoot trefoil nodules exposed to 14CO2. By contrast, asparate, asparagine, and glutamine were the predominantly labeled amino acids in xylem sap collected from nodulated effective roots exposed to 14CO2. The occurrence of nodule CO2 fixation in alfalfa and birdsfoot trefoil and the export of fixed carbon as asparagine and aspartate to roots and shoots is consistent with a role for CO2 fixation by nodules in providing carbon skeletons for assimilation and transport of symbiotically fixed N2.
Movement and Metabolism of Sucrose in Developing Barley Kernels1
Authors: Lingle Sarah E. , Chevalier Peggy
Published: July 2010

Sucrose metabolism in developing barley (Hordeum vulgare L.) kernels was studied from anthesis to physiological maturity. To follow the fate of sucrose entering the developing barley kernel, 14C‐sucrose was introduced to specific kernels through the awn of the subtending lemma. After 2 h, kernels were removed and dissected into vascular tissue, outer pericarp, inner pericarp, and endosperm. Leachable sugars were extracted by incubating the tissues in an osmoticum for 1 h at 0 to 1°C. The tissue was transferred to 80% (v/v) ethanol to extract nonleachable sugars. Starch was determined in the residual tissue. Simple sugars in the teachable and nonleachable fractions were separated by paper chromatography. Radioactivity in all fractions and incorporated into starch was determined. Throughout kernel development, the tissue containing the largest percentage of 14C fed to the kernel from the subtending awn was the endosperm. The pericarps contained a pool of 14C‐sucrose which was easily leached from the tissue. The specific activity of this pool was similar to the specific activity of the teachable pool of 14C‐sucrose of the endosperm. Incorporation of 14C‐sucrose into starch during the 2‐h period of the experiment declined with kernel age. These data support the hypothesis that the rate and duration of starch synthesis in barley endosperm are limited by processes within the endosperm, possibly the conversion of sucrose to starch, and not by availability of sucrose to the endosperm.
Genetic Analysis of Resistance to Barley Yellow Dwarf Virus in Hybrids between Avena sativa ‘Lamar’ and Virus‐Resistant Lines of Avena sterilis1
Authors: Landry B. , Comeau A. , Minvielle F. , St‐Pierre C.‐A.
Published: July 2010

Seven lines of Avena sterilis L. were compared to one of A. sativa L. as sources of resistance to the barley yellow dwarf virus (BYDV), in crosses with the susceptible A. sativa ‘Lamar’ on the basis of visual symptoms under conditions of artificial virus inoculation in the field. Additive gene action explained most of the genetic variability observed, and heritability estimates were generally high. According to East's formula, four or fewer segregating factors were involved, so the classification of plants on a symptom basis was tested against simple genetic models. Three simple models explained the variation observed in the F2 generation of four crosses. Two crosses conformed to a model with one dominant and three additive resistance genes, and the other two fit models with only two and three additive genes, respectively.