bluuebunny/crossref_metadata_2025 huggingface dataset:
Selection for Monogenic Pest Resistance Traits with Coupling‐ and Repulsion‐Phase RAPD Markers
Authors: Haley Scott D. , Afanador Lucia , Kelly James D.
Published: July 2010

The random amplified polymorphic DNA (RAPD) assay has recently provided a marker system that may be useful for indirect selection and pyramiding of monogenic pest resistance traits in crop species. Our objective was to investigate the efficiency of marker‐assisted selection with RAPD markers linked in coupling and in repulsion with a single resistance allele. Common bean (Phaseolus vulgaris L.) near‐isogenic lines differing for the recessive bean common mosaic virus (BCMV) resistance allele bc‐3 were screened to identify linked RAPD markers. Two cosegregating RAPD markers were identified and scored across an F2 population of 103 individuals segregating for the bc‐3 allele. One RAPD marker was linked in coupling (1.9. ± 1.4 cM) and one in repulsion (7.1 ± 2.6 cM) with the bc‐3 allele. Categorization of the bc‐3 genotypes in the F2 population revealed that selection against the repulsion‐phase RAPD, as opposed to selection for the coupling‐phase RAPD, provided a greater proportion of homozygous resistant (81.8 versus 26.3%) selections, and a lower proportion of both segregating (18.2 versus 72.5%) and homozygous susceptible (0.0 versus 1.2%) selections. Selection of individuals based on the phenotype of both RAPD markers (i.e., the plus form of the coupling‐phase RAPD and simultaneous with the minus form of the repulsion‐phase RAPD) was identical to selection based solely on the repulsion‐phase RAPD alone. The selection results obtained in our case study were consistent with the theoretical expectations, and both demonstrated that repulsion‐phase linkages provided greater selection efficiency than coupling‐phase linkages, even when the former have greater linkage distances from the pest resistance allele. Because repulsion‐phase RAPD markers are more useful in marker‐assisted selection for monogenic pest resistance traits, researchers will want to design their screening experiments in ways that will optimize the discovery of these.
Genetic Diversity among Latin American Andean and Mesoamerican Common Bean Cultivars
Authors: Voysest Oswaldo , Valencia Maria C. , Amezquita Maria C.
Published: July 2010

Knowledge of the relationship among existing crop cultivars helps broaden the genetic base of new cultivars, facilitates deployment of useful genes, reduces genetic vulnerability, and maximizes the use of available germplasm resources. In this study, our objective was to analyze the genetic base of common bean (Phaseolus vulgaris L.) cultivars released in Latin America from the onset of breeding activities until 1993. Each of the 203 cultivars of hybrid origin and their 194 ancestors were classified into one of six racial groups: Mesoamerica, Durango, Jalisco, Nueva Granada, Peru, or Chile. Genetic diversity was assessed, based on the pedigree, through the coefficient of parentage (r). The groups of 130 cultivars of Race Mesoamerica and 46 cultivars of Race Nueva Granada both received 79 and 76% of their genes, respectively, from ancestors of their same race. Furthermore, a 55% genetic contribution in the case of Race Nueva Granada cultivars and 41% for Race Mesoamerica was attributed to 12 and 10 ancestors of the same race, respectively. The 18 cultivars of Race Durango received 18% of their genes from Race Nueva Granada; the genetic contribution from their same race was as much as 43%. The three cultivars of Race Chile received half of their genes from Race Chile; the other half came from Races Nueva Granada, Mesoamerica, and Durango. Races Jalisco and Peru received little or no improvement and were used little in the improvement of cultivars of other races. When cultivars were grouped by different time periods, the increasing trend of using interracial hybridizations to broaden the genetic base of cultivars of Races Mesoamerica and Nueva Granada became evident.
Genetic Variability for Flooding Tolerance in Soybeans
Authors: VanToai T. T. , Beuerlein A. F. , Schmitthenner S. K. , St. Martin S. K.
Published: July 2010

The flooding tolerance of U.S. soybean [Glycine max (L.) Merr.] cultivars under field conditions has not been reported. In this study, 84 soybean cultivars of maturity groups II, III, and IV were grown at two locations, London and Lakeview, in Ohio. The cultivars differed in their resistance and tolerance to Phytophthora sojae M.J. Kaufmann & J. W. Gerdemann as determined in separate field and laboratory studies. While the production practices and historic yield potential at the two locations were similar, the nearly flat, slowly permeable Milford silty clay soil at Lakeview was saturated during most of July 1992 because of excessive rainfall (17 cm more than normal). The average yield of the 84 soybean cultivars at the flooded location (Lakeview) was 25% lower than at the non‐flooded location (London). Flooding tolerance can be defined as high yield under flooding stress. When the 84 soybean cultivars were ranked in their flooding tolerance according to this definition, many cultivars were found to exhibit both flood tolerance at Lakeview and high yield at London. Flooding tolerance was independent from Phytophthora tolerance, Phytophthora resistance, and plant relative maturity. This study documented that differences in flooding tolerance exist among U.S. soybean cultivars.
Test Site Allocation within and among Stages of a Sugarcane Breeding Program
Authors: Milligan S. B.
Published: July 2010

The Louisiana Sugarcane Variety Development Program (LSVDP) currently uses up to 13 yr from crossing to develop a new sugarcane (Saccharum sp. hyb.) cultivar. The outfield trials constitute the final testing stage. Recent changes in pre‐outfield testing warrant examination of resource allocation among and within these two testing stages. Sucrose yield variance components were obtained from outfield tests harvested from 1987 to 1990 and from a published report concerning pre‐outfield tests. Sucrose yield repeatability estimates for three crops were made with varying numbers of test locations and replications for the two test stages. Three replications at each of 10 locations resulted in 95.5% of the repeatability of using three replications at 13 plant‐cane outfield tests. Plant‐cane pre‐outfield results with eight locations and three replications effected 94.7% of the repeatability of using three replications and 13 locations. Repeatability slightly increased in the pre‐outfield tests and slightly decreased in the outfield tests with older crops for a given number of locations and replications. Correlation of genotype‐location mean yields among test locations indicated no redundancy of test sites. The outfield tests are customarily analyzed as either heavy or light textured soil tests. The efficacy of this soil classification was tested with three statistical models. The results did not support partitioning of the outfield tests by soil texture and indicated approximately as much genotype × location interaction within soil groupings as among the groupings. The conclusion was that a reduction in the number of outfield test sites coupled with an increase in pre‐outfield test number should render a more efficient breeding program.
Genetic Improvement in White Clover Representing Six Decades of Plant Breeding
Authors: Woodfield D. R. , Caradus J. R.
Published: July 2010

Improvements in white clover (Trifolium repens L.) performance during the past 60 yr can be attributed to increased use of fertilizer, better management practices, and development of genetically superior cultivars. The rate of genetic improvement during the past six decades was evaluated in New Zealand using a world collection of 110 white clover ecotypes and cultivars. Genetic differences were assessed by evaluating all cultivars in the same environment. Field trials conducted from 1985 to 1989 were managed using rotational grazing by sheep (Ovis aries L.) with an average of nine grazings per year. Cultivars were grouped according to decade of release, the climate in which they originated (cold, cool, or warm), and plant type (small‐leaved, medium‐leaved, large‐leaved non‐ladino, and large‐leaved ladino). Regression analyses were used to determine the rate of genetic improvement. In absolute units, white clover yield has increased at an annual rate of 1.44 g m−2, whereas the percentage clover by weight in the sward has increased at an annual rate of 0.14%. This equates to a genetic gain of 6% per decade for both traits, which is higher than rates reported for other forage crops. Genetic gains for clover yield and percentage clover in the sward have been greatest in small‐leaved (7.5 and 8.7% per decade) and large‐leaved, non‐ladino types (6.6 and 8.3% per decade), whereas cultivars originating in cool climates (8.3 and 8.1% per decade) have improved at a faster rate than those originating in either cold (3.5 and 3.2% per decade) or warm climates (1.5 and 2.6% per decade).
Comparison of Four Cotton Genotypes for Resistance to Heliothis virescens
Authors: Jenkins Johnie N. , McCarty J. C.
Published: July 2010

Heliothis spp. are major pests of cotton, Gossypium hirsutum L., in many cotton‐producing countries of the world. Two strains of cotton putatively resistant to Heliothis virescens Fab., tobacco budworm, and two adapted cultivars, Deltapine 50 and DES 119, were grown in plots infested with tobacco budworm and in plots free of tobacco budworm (paired plots) for 2 yr. The difference in lint yield between each genotype grown in tobacco budworm‐infested plots and in tobacco budworm‐free plots was used as the measure of resistance. LA 850082 was significantly more resistant each year than the other three. ST 69132 was significantly more resistant each year than DES 119 and more resistant than DPL 50 1 yr. Our results confirm the Heliothis resistance of strains LA 850082 and ST 69132. LA 850082 should be a good source of resistant germplasm to use in developing cultivars that resist infestations of tobacco budworm. In terms of agronomic characteristics, LA 850082 was significantly higher in yield than the two cultivars; however, it is known to have shorter and weaker fiber. Combining the δ‐endotoxin gene from Bacillus thuringiensis with the resistance of LA 850082 is suggested as a strategy for development of cultivars with multiple mechanisms for resistance to Heliothis spp.
Grain Legume Effects on Soil Nitrogen, Grain Yield, and Nitrogen Nutrition of Wheat
Authors: Badaruddin M. , Meyer D. W.
Published: July 2010

Cereal crop yields frequently are greater when grown after soybean [Glycine max (L.) Merr.] than after continuous cereal cropping. Information on other grain legumes is limited in eastern areas of the northern Great Plains. The objectives of this field study were to determine (i) soil nitrate‐N status in the spring following grain legumes, and (ii) grain legume effects on grain yield, grain yield components, and N nutrition of the subsequent hard red spring wheat (Triticum aestivum L. emend. Thell.) crop fertilized with 0, 75, and 150 kg ha−1. Two‐year crop sequences were evaluated on a Fargo silty clay (fine, montmorillonitic, frigid Vertic Haplaquoll) soil at Fargo, ND, and on a Perella‐Bearden silty clay loam (fine‐silty, mixed, frigid Typic Haplaquoll, fine‐silty, frigid Vertic Calciaquoll) soil at Prosper. Six grain legume species were harvested for grain, and aboveground residues were removed in 1984 and were uniformly spread and incorporated into the soil in 1985. Spring soil nitrate‐N level following legumes was 28% greater than that following N‐fertilized wheat across three environments but 43% lower than that following fallow. Unfertilized wheat grain yields following grain legumes were equivalent to or greater than that following a wheat crop fertilized with 75 kg N ha−1 and similar to fallow at the same fertility level. Total N accumulation by wheat following grain legumes was 9% greater than that following wheat but 13% lower than that following fallow. Nitrogen‐use efficiency for wheat following legumes, however, was up to 32% greater than that for wheat following fallow and up to 21% greater than that for continuous wheat. These studies indicate that grain legumes should be considered in cropping systems in higher moisture areas of the northern Great Plains to help maintain subsequent crop productivity.
Kernel and Spike Character Influence on Test Weight of Soft Red Winter Wheat
Authors: Schuler Steve F. , Bacon Robert K. , Gbur Edward E.
Published: July 2010

Although genotype affects test weight in wheat (Triticum aestivum L.), little is known about how physical kernel characteristics affect this quality parameter. The influence of seed and spike characteristics on test weight was investigated in 24 soft red winter wheat (SRWW) cultivars grown in six environments. Seed characters and test weight were measured using gram samples from which shriveled kernels had been removed. Removal of the shriveled kernels increased test weight an average of 36 kg m−3 and reduced the total variation in test weight due to environment and environment by cultivar interaction. Of the seed and spike characters measured, only flour protein content and the average number of seed within a spike were significantly correlated to test weight (r = 0.56 and r = −0.41, respectively) at P = 0.05. Average kernel length and width and the average number of seed per spikelet showed weak negative correlations with test weight (r = −0.38, r = −0.35 and rs = −0.35, respectively) at P = 0.10. Increasing kernel density was weakly associated with increasing test weight (r = 0.39, P = 0.10). Thousand‐kernel weight, diversity of seed size, kernel length to width ratio, spike length, number of spikelets per spike, and spike density were not directly related to test weight. Results of this study indicate that among the characters measured, the amount of shriveling and the protein content of the grain were the most important determinants of test weight in SRWW cultivars.
Nitrogen Fertilizer Effect on Breadmaking Quality of Hard Red Spring Wheat in Eastern Canada
Authors: Ayoub M. , Guertin S. , Fregeau‐Reid J. , Smith D. L.
Published: July 2010

The production of bread‐quality wheat (Triticum aestivum L.) in eastern Canada might be possible through correct fertilizer management. Field experiments were conducted for 2 yr at each of two sites in Québec. The influence of N fertilizer level and timing on breadmaking quality and grain ash of four hard red spring wheat cultivars (Columbus, Katepwa, Max and Hege 155‐85) known to have potential as bread wheat was investigated. The soil types were fine, mixed, non‐acid, frigid Humaquept at Ste‐Anne‐de‐Bellevue and typic, non‐acid, frigid Humaquept at Ste‐Rosalie. Four rates of N (0, 60, 120, and 180 kg N ha−1) were applied at seeding time or 60% at seeding and 40% at anthesis, resulting in a 4 × 4 × 2 factorial experiment with four replications. Increasing N reduced gram and flour ash concentrations and increased flour protein concentration, Hagberg falling number and flour absorption of water. Splitting the N application increased flour protein concentration and bread loaf volume. Cultivar by N level interactions often occurred for farinograph variables. Farinograph readings for Max and Hege 155‐85 were unproved with N fertilizer addition, but this was generally not the case for Katepwa and Columbus. In general, all cultivars tested could produce flour suitable for bread wheat production in eastern Canada but the N management required for this varied with cultivar. Despite its high grain and flour yield, Hege 155‐85 may not be economical to produce because high N fertilizer applications are required to achieve the appropriate protein concentrations and flour might have to be supplemented with gluten to achieve the required protein concentration.
Growth and Transpiration Efficiency of Near‐Isogenic Lines for Height in a Spring Wheat
Authors: Ehdaie B. , Waines J. G.
Published: July 2010

The two most commonly used dwarfing genes of bread wheat (Triticure aestivum L.) are Rhtl and Rht2. The Rht3 gene is also a potent dwarfing gene. Information in the literature is limited as to the comparative effects of these genes on transpiration efficiency (TE) and wateruse efficiency (WUE). Carbon isotope discrimination (Δ) has proposed as a criterion to select for improved TE. Four near‐isogenic lines, rhtrht, RhtlRhtl, Rht2Rht2, and Rht3Rht3, in ‘Maringa’ bread wheat background and four of their near‐isogenic F1 hybrids derived from crossing the original lines were used to determine the effects of dwarfing genes on plant height, root dry matter, shoot dry matter including grains, grain yield, total dry matter (TDM), TE (TDM/water transpired), WUE (grain yield/water used), and Δ in well‐watered droughted pot experiments in the glasshouse. The near‐isogenlc lines and their six F1 hybrids were also grown in well‐watered and droughted field conditions. Plant height ranged from 60 to 124 cm and from 53 to 121 em in well‐watered and droughted pot experiments, and it varied from 50 to 94 cm and from 49 to 90 cm in well‐watered and droughted field experiments, respectively. Total dry matter, grain yield, TE, and WUE declined with plant height in well‐watered glasshouse conditions. No significant relationships were found between plant height and these traits in droughted glasshouse conditions. Carbon isotope discrimination was negatively correlated with TE, but significantly so only in the well‐watered pot experiment. Plant height was negatively associated with Δ in both well‐watered and droughted pot and field experiments. Grain yield and shoot dry matter also declined with plant height in field conditions. Negative correlations were observed between Δ and grain yield and Δ and shoot dry matter in well‐watered field conditions. In most cases, the dwarfing genes reduced shoot dry matter more than grain yield and, therefore, harvest index of the semidwarf and dwarf lines was higher than that of the tall standard fine. The dwarfism caused by RhH, Rht2, and Rht3 genes had, in general, depressing effects on TE, WUE, TDM, and grain yield.
Selection for Rind Puncture Resistance in Two Maize Populations
Authors: Dudley J. W.
Published: July 2010

Because stalk lodging is an important problem in maize (Zea mays L.) production, improved methods of breeding for stalk lodging resistance are important. The objective of research reported in this paper was to determine the influence of six cycles of selection for rind puncture resistance, measured just prior to anthesis, on postanthesis rind puncture resistance, grain yield, grain moisture, and stalk rot reaction in two maize synthetics, RSL(MPEN) and RSSSC(MPEN), which represent two different heterotic groups. Response to selection was measured in the populations, per se, testcrosses of each cycle of each population to an appropriate inbred tester, and in crosses between cycles of the two synthetics. In all cases, selection significantly increased postanthesis rind puncture resistance. Stalk lodging was significantly reduced for all cases except RSL(MPEN) per se. Stalk rot incidence was significantly reduced in RSSSC(MPEN) per se. Few adverse effects were noted for other traits. Measuring rind puncture resistance just before pollination allowed effective improvement in stalk lodging resistance using a selection scheme which requires only one generation per cycle.
Pedigree Analysis of Elite Soybean Lines
Authors: Sneller Clay H.
Published: July 2010

The reported genetic diversity of North American soybean [Glycine max (L.) Merr.] cnitivars is low. Public and industry breeders have initiated programs to expand the diversity. This paper assesses the impact of diversification efforts on the extent and pattern of diversity among elite lines and estimates the impact of industry on diversity. Coefficient of parentage (CP) analyses were performed with 122 lines from the northern and southern regions of the USA. The average CP was 0.173: this value was 0.233 among northern lines, 0.261 among southern lines, and 0.100 between lines from different regions. These values, and an analysis of the number of ancestors and their contribution of parentage to the elite population, were similar to values in previous reports, thereby indicating that recent efforts of public and proprietary breeders have had little impact on diversity among current elite lines. Minor differences in genetic diversity were noted between lines from public or proprietary sources. Industry has affected diversity by introducing parentage from PI 257.435, and the development of ‘A3127’ has served as a genetic bridge between regions. Cluster analysis distinctly separated northern lines from Maturity Group V and V1 lines and suggested four clusters within each region. Principal component analyses interpreted the clusters as groups of lines with genetic similarity to recently developed parents that were used extensively to generate the elite population. Genetic diversity within and between regions could be exploited by crossing pairs of lines that have a low CP. The effectiveness of this approach could be enhanced by using cluster patterns to achieve a more thorough sampling of the genetic diversity.
Alfalfa Maturity and Cultivar Effects on Chemical and In Situ Estimates of Protein Degradability
Authors: Griffin T. S. , Cassida K. A. , Hesterman O. B. , Rust S. R.
Published: July 2010

The relationships among plant maturity or genotype and forage quality and ruminal in situ degradability of alfalfa (Medicago sativa L.) are inadequately understood. A 2‐yr experiment was conducted to study the effects of cutting (spring or summer), plant maturity (six sampling dates), and cultivar (Vernal, Arrow, WL‐320, and Target II or Legend) on chemical composition and in situ degradability of alfalfa. Plant maturity was quantified by the mean stage weight (MSVO system. Herbage cell wall, cell‐wall bound N, and in situ escape protein CEP) increased significantly with MSW; crude protein (CP) and situ dry matter degradability (ISDMD) decreased. Forage nutritive quality declined less with increasing MSW in summer than in spring cuttings. In 1991, the cultivar Target II had lower ISDMD than Vernal, Arrow, or WL‐320, while summer growth of Arrow contained less EP than other cultivars. In 1992, Vernal had higher EP than Arrow, WL‐320, or Legend. High EP related to increasing maturity or cultivar differences was negatively correlated with other measures of nutritive quality. Differences in chemical composition and in situ degradability among alfaffa cultivars exist, but are dependent on growing conditions. Usefulness of the MSW system to predict alfalfa nutritive quality is limited to within cuttings, and cell‐wall bound N measures were better predictors of alfalfa EP than was MSW.
Elongation of the Grass Leaf and its Relationship to the Phyllochron
Authors: Skinner R. H. , Nelson C. J.
Published: July 2010

The phyllochron (interval between appearance of successive leaves) in grasses is determined by timing of leaf initiation at the stem apex and duration of leaf tip elongation through the whorl of mature sheaths. Primordia in tall fescue (Festuca arundinacea Schreber) are initiated and enlarge to ⊄ 1.5 nun in length by production of cells that remain ⊄ 20 um long. As a young leaf continues to grow, epidermal cells beyond 1.5 nun from the base elongate to form a cell elongation zone of 7 to 40 mm, depending on genotype and environment, which pushes older tissue through the whorl. Leaf elongation rate is a function of length of the elongation zone and segmental elongation rate of positions within the zone. This zone constitutes a major sink for carbohydrate, N, and water deposition in the leaf. Ligule formation occurs in the cell division zone when the blade is ⊄20% of its final length. Blade and sheath elongation take place simultaneously thereafter with their relative proportion depending on position of the ligule in the elongation zone. Initiation of leaf elongation from a resting primordium at a given node is coordinated with ligule initiation in the next‐older leaf one node below and with cessation of cell division in the sheath and commencement of tiller elongation at the axillary bud two nodes below. Duration of leaf tip elongation through the whorl depends on elongation rate and sheath length. The importance of these factors in determining the phyllochron is often overlooked due to calculation procedures that assume a constant phyllochron when in fact the phyllochron often changes for each leaf.
Factors Affecting Rate of Leaf Emergence in Barley and Wheat
Authors: Kirby E. J. M.
Published: July 2010

Rate of leaf emergence of wheat (Triticum aestivurn L.) and barley (Hordeum vulgare L.) changes with sowing date and temperature and appears to be set early in the plant's life cycle. Four models that advance different hypotheses to explain this variation are examined. None is completely satisfactory, partly because of a nonlinear response to thermal or photothermal time. Soil strength, N nutrition, and depth of sowing affect rate of leaf emergence, as may sub‐zero temperature or ontogeny. An alternative hypothesis proposes that leaf emergence rate depends on daylength and acclimation to temperature. Potential rate of leaf emergence may be determined by factors acting on leaf primordia, which are initiated early in the life cycle.
Shoot and Root Development in Rice Related to the Phyllochron
Authors: Nemoto Keisuke , Morita Shigenori , Baba Tadashi
Published: July 2010

In grasses, construction of a growing plant is determined primarily by the rate of leaf development in the shoot apex and the timing of tillering and rooting of individual phytomers relative to leaf development. Our purpose is to review shoot and root growth in relation to emergence of leaves in rice (Oryza sativa L.). Development of the leaf, tiller bud, and adventitious roots of each phytomer proceeds in order, at a rate that depends on leaf initiation rate at the shoot apex. Consequently, initiation, leaf emergence, tillering, and rooting of each tiller are closely synchronized with leaf emergence on the main stem. Leaves that emerge simultaneously are similar in size. Tillers whose leaf emergence is retarded from this synchronization will generally die before anthesis. Inflorescence development is closely correlated with development of the subtending leaves in each tiller, resulting in a highly predictable phenology in relation to leaf emergence. Because of these relationships, the leaf number concept provides researchers with an effective index for studying development of shoot and root systems in rice, including the prediction of tiller morphology, the estimation of potential tiller increase, and analysis of root system dynamics.
Quantifying Developmental Morphology of Perennial Grasses
Authors: Moore K. J. , Moser L. E.
Published: July 2010

Perennial forage grasses can be viewed as modular organisms. The phytomer is usually considered the basic unit of the grass plant and consists of a leaf blade and sheath, the internode, the node, and the associated auxiliary bud below the point of sheath attachment. The tiller is a collection of phytomers differentiated from a single apical meristem. The grass plant is a group of tillers that ultimately arise from a single zygote and are of the same genotype. A grass sward is a population of individual plants, often genetically related, but usually of unique genotypes. The developmental morphology of perennial grass swards is dynamic and is a function of the spatial and temporal distribution of growth stages within the population of tillers comprising the sward. Management practices are applied to forages at the sward level. Systems for quantifying developmental morphology of perennial grasses that are to be used for management purposes must be applicable at the sward, or population, level. The phyllochron concept, which is widely used in studies of cereals, has been employed in only a limited number of studies on forage management. Numerical indices have been used successfully to quantify grass morphology, but have some inherent limitations when used for predictive purposes. The principles of population ecology, particularly plant demography, provide a framework for studying the developmental morphology of perennial grass populations and can be used in conjunction with numerical indices to describe tiller populations.
Heritabilities, Genetic Parameters, and Response to Selection in Pearl Millet × Elephantgrass Hexaploid Hybrids
Authors: Diz D. A. , Schank S. C.
Published: July 2010

Seeded pearl millet [Pennisetum glaucum (L.) R.Br.] × elephantgrass (Pennisetum purpureum Schum.) allohexaploids possess many desirable attributes for forage and biomass production. Estimation of genetic parameters would be useful in developing appropriate selection strategies. This study was conducted to obtain single‐plant heritability estimates; genetic, phenotypic, and environmental correlations; and expected responses to selection for several vegetative and reproductive characteristics. Data were collected in 1990 and 1992 from a factorial experiment containing seven S1 (selfed) families which were grown on a Sparr fine sand (sandy siliceous, hyperthermic Grossarenic Paleudult). Fewer plants were evaluated in 1992 because of lack of persistence. Due to significant year effects, and because 1992 data was affected by plant loss, years were analyzed separately. Heritability estimates differed among the 11 traits and were very low to moderate. Leaf width had the highest heritability for vegetative traits (0.16 in 1992). Heritabilities for reproductive characters were moderate in 1990, being highest for 100‐seed weight (0.30) and seeds per panicle (0.29). In 1992, lack of significance among families for most reproductive characters reduced heritability estimates. Some correlations were consistent over years. Number of tillers was negatively associated genetically with plant height and leaf characteristics. Days to flowering was negatively associated with vegetative and reproductive traits. Seed‐related traits were highly correlated among themselves. Despite moderate to low heritabilities for seed characters in 1990, expected responses to selection were high (17‐43% increase) due to large phenotypic variation. For improving seed yield per plant, selecting indirectly for days to flowering or other seed‐related traits would be more efficient. Improvement through phenotypic selection should be satisfactory in several traits.
Selection for Water‐Stress Tolerance in Interracial Populations of Common Bean
Authors: Singh Shree P.
Published: July 2010

Crop cultivars that tolerate water stress would stabilize and expand production in drought endemic environments. They would require less irrigation and help conserve water, an essential natural resource. My objectives were to (i) compare, in water‐stressed and nonstressed environments, the performance of inbred lines from interracial populations of common bean (Phaseolus vulgaris L.), involving water‐stresstolerant parents, (ii) identify lines that out‐yielded the parents, and (iii) determine heritability and expected gains from selection. Eighty‐five Fs‐derived Fs random lines, a population bulk, and four parents from each of two populations (TR 7790 and TR 7791) were evaluated between 1991 and 1993 at Palmira, Colombia. The TR 7790 population involved crosses between common bean races Mesoamerica and Durango, and TR 7791 involved races Mesoamerica and Nueva Granada. Water stress reduced seed yield and 100‐seed weight and accelerated maturity. The mean seed yield for population bulk, inbred lines, and parents of TR 7790 in both water‐stressed and nonstressed environments were higher than those of TR 7791. In population TR 7790, eight lines yielded higher (by an average of 52%) than the mean of parents and six lines yielded higher (by an average of 41%) than the highest yielding parent under water stress. In population TR 7791, eight lines yielded higher than the mean of parents and one line yielded higher than the best parent under water stress. For seed yield, heritability was low for TR 7791 (0.26 ± 0.18 to 0.38 ± 0.17) and high for TR 7790 (0.66 ± 0.15 to 0.80 ± 0.15). Expected gains from selection ranged from 10 to 48%. These results justify searching for and using more germplasm highly tolerant to water stress from races Durango and Mesoamerica.
Breeding Cottons for Conventional and Late‐Planted Production Systems
Authors: Lloyd May O. , Bridges Bill C.
Published: July 2010

Cotton (Gossypium hirsutum L.) growers in South Carolina are replacing some of their soybean [Glycine max (L.) Merr.] hectareage planted after wheat (Triticum aestivum L.) with cotton. A breeder must decide whether a small but expanding hectareage of late‐planted (LP) cotton will require a breeding scheme separate from one for the conventional (CN) full‐season production system. The objective of this study was to assess selection strategies that will result in cottons with improved lint yield and fiber quality for CN and LP production systems. Twenty‐five unselected Pee Dee cotton genotypes, along with a full‐season and an early maturing cultivar, were evaluated in a 2‐yr experiment conducted at Florence, SC, in two production systems: CN, planted approximately the first week of May, and LP, planted 8 June. Lint yield, fiber, and spinning properties were determined. Significant (P < 0.05) genotypic variation existed for all traits, but there was no significant genotype × production system interaction. Heritability of each trait plus the genetic correlation between production systems was used to compare predicted and observed direct and correlated response in each production system. Predicted gain in LP yield when selection was conducted in the CN production system was a 2.1% increase in the population mean compared with a 3.1 % observed response. Selection for 2.5% span length and yarn strength in the CN system resulted in gains in both production systems. Antagonistic genetic correlations between some of the fiber traits and lint yield will make concurrent improvements in both production systems difficult. Use of a low selection intensity in the CN production system in the initial round of replicated yield testing was found to be an efficient method to improve lint yield or yarn strength.
Nitrogen and Carbon Accumulation and Remobilization during Grain Filling in Maize under Different Source/Sink Ratios
Authors: Uhart Sergio Adolfo , Andrade Fernando Héctor
Published: July 2010

The relative flow and remobilization of carbon (C) and nitrogen (N) to the grain during the grain filling period depends on the particular source/sink ratio of the crop. The objective of this work was to analyze the C and N accumulation and remobilization patterns of maize (Zea mays L.) under a wide range of source/sink ratios. The experiment was conducted at Balcarce, Argentina, during 2 yr with both a shortand long‐season hybrid. The treatments consisted of two levels of source reduction (45 and 55% shading during the grain filling period), two levels of reproductive sink reduction (45 and 55% shading during a 30‐d period bracketing silking), and an unshaded control. The shading treatments had a variable duration (30=38 d) to ensure constant incident radiation. The source limitation produced increases in remobilization rates of leaf + stem reduced N (Nred) and stem nonstructural carbohydrates (CH) compared with the control. The sink limitation generated greater stem CI‐I accumulation and less Nred remobilization from the leaf and stem. Sink‐limited treatments had greater postanthesis N absorption and grain N concentration than the sourcelimited treatments. As the source/sink ratio decreased, N flow to the grain per unit of C flow decreased suggesting that N becomes more limiting for grain yield with increasing source limitation. Linear quantitative relationships between source/sink ratio and CH remobilization, N remobilization, relative C‐N fluxes to the kernel, and kernel N concentrations have been established.
Rapid, Inexpensive Method for Determining Glucose Concentrations in Cotton Bolls and Other Plant Tissues
Authors: Timpa Judy D. , Striegel Andre M. , Abellanosa Alan L. , Triplett Barbara A.
Published: July 2010

Our objective was to develop a rapid, specific, and inexpensive method for measuringg lucose concentrations in bolls of cotton (Gossypium hirsutum L.). A new procedure was developed, based on a reagent strip for measuring blood glucose in diabetic patients, and compared with three other glucose methods by assaying glucose standard solutions. The strip results were significantly correlated (r = 0.948) with known concentrations of glucose and comparable to other methods in both precision and accuracy. For aqueous extracts of locules (lint and seed) from 15 days‐post‐anthesis (DPA) cotton bolls, glucose levels were −10 mg g−1 fresh weight. The reagent strip strongly correlated to glucose hexokinase, glucose oxidase, and anthrone methods with correlation coefficients (r) of 0.983, 0.994, and 0.974, respectively. Thus, the strip technique should be useful for routine glucose determinations in cotton bolls considering the time (−2 rain/sample), cost (−.70/sample), and portability.
Using Best Linear Unbiased Predictions to Enhance Breeding for Yield in Soybean: I. Choosing Parents
Authors: Panter D. M. , Allen F. L.
Published: July 2010

In serf‐pollinated crops, choosing parents typically is accomplished by calculating parental performance from historical data and then calculating the midparent value (MPV) for potential crosses. When limited or no data exist for parents of interest, precise predictions are difficult or impossible to obtain. Best linear unbiased prediction (BLUP), has been used to determine paired matings in dairy cattle under conditions described above. The objectives of this study were to compare the elficiencies of two methods of parental selection, MPV and BLUP, for identifying superior soybean [Glycine max (L.) Merr.] cross combinations when (i) equal and unequal amounts of yield data on all potential parents were available, and (ii) unequal amounts of yield data were available for some parents and no data were available for others. F4–F6 bulks and F5:6 lines from 24 soybean crosses were evaluated to estimate the mean yield performance of each cross. Historical yield records on the parents of each cross were used to predict the performance of the 24 crosses. Numbers of records on the parents were restricted to provide simulated situations of balanced and unbalanced parent data availability. The performance of each cross was predicted with MPV and BLUP for each situation. Standard errors of the predicted differences (SE) and rank correlations between the actual and the predicted performances were calculated to determine the relative efficiencies of MPV and BLUP. In every case, predictions from BLUP provided higher rank correlations, lower SE, and identified higher percentages of the superior crosses than MPV.
Integration of the Soybean Molecular and Classical Genetic Linkage Groups
Authors: Shoemaker R. C. , Specht J. E.
Published: July 2010

To initiate the process of map integration, we used data from a Glycine max × G. max mapping population that had segregating markers at seven pigmentation (D1 D2 G 1 L1 T Y9), six morphological (Dt1 E2 Lf1 Ln P1 Pd1), and seven isozyme (Aco4 Enp 1dh1 Mdh Mpi Pgi Pgm1) loci (underscoring indicates marker members of the classical map). The parents of this population were two multi‐marker strains, one a near‐isogenic line (NIL) of the cultivar Clark, and the other a NIL of the cultivar Harosoy. Sixty F2.3 progeny lines were characterized for allelic status at the 20 classical loci, 8 RAPD loci, and 110 RFLP loci; the latter previously mapped in the G. max × G. soja mapping population. The computer program JoinMap was used to pool the linkage data obtained in both populations and to build consensus linkage groups. As a result of these analyses, marker T of classical linkage group 1 (CLG‐1) was assigned to molecular linkage group c2 (MLG‐C2), marker P1 of CLG‐2 to MLG‐k, markers Dt1 and L1 of CLG‐5 to MLG‐1, marker Y9 of CLG‐14 to MLG‐e, and marker Mpi of CLG‐18 to MLG‐g. Probes A702 and B219, which had detected two MLG‐bl markers (i.e., A702‐1 and B219‐1) in the G. max × G. soja population, detected two different (homoeologous?) markers (i.e., A702‐2 and B219‐4) in the Clark × Harosoy population, and these were linked to markers G, D1, and Pd1 of CLG‐3. Markers Ln and Enp of CLG‐4 were linked to two RFLP markers, but the MLG association was ambiguous because in the G. max × G. soja map one of the RFLP markers mapped to MLG‐f and the other mapped to MLG‐i. With the CLG to MLG assignments made in this study, plus others that can be inferred from the recent literature, about half of the 19 soybean CLGs can now be associated with a corresponding MLG.
Tall Fescue Development in Response to Acremonium coenophialum and Soil Acidity
Authors: Belesky D. P. , Fedders J. M.
Published: July 2010

The fungal endophyte Acremonium coenophialum Morgan‐Jones & W. Gams can modify productivity and stress tolerance of tall fescue (Festuca arundinacea Schreber). Clonal populations of five tall fescue genotypes were used in a glasshouse experiment to assess the effect of endophyte infection and soil pH on plant yield, demography, and development. Genotypes differed for most measured parameters, and a general lack of interactions among endophyte infection, genotype, and lime allowed use of treatment means to identify trends that may be reflected in larger populations. Infected plants had 13% greater shoot mass and 11% greater root mass than uninfected plants due primarily to increased tiller size. Larger size may increase tiller longevity and competitive ability. Endophyte did not affect relative tiller appearance rate as reduced relative leaf appearance rates were compensated by increased site usage. Liming of an acid soil (pH 4.3 for unamended soil) resulted in a 32% increase in dry matter production and increased root to shoot ratios of high‐yielding genotypes. Root to shoot ratio was affected by the interaction of lime and genotype; high‐yielding genotypes had greater root to shoot ratios when limed compared with nonlimed genotypes, while low‐yielding genotypes were not affected by liming. This increase was associated with greater site usage and tiller production; relative leaf appearance rate and tiller mass were unaffected. Endophyte modified the resource allocation patterns with resultant increase in phenotypic plasticity and potential competitive ability.
An Efficient Method for Measuring Sod Reserves for Greenhouse and Field Studies
Authors: Burton Glenn W.
Published: July 2010

Nonstructural carbohydrates and other reserves in roots, rhizomes, stolons, crowns, or stubble determine regrowth by grass sod after defoliation. Traditionally, these reserves have been estimated by collecting and growing 15‐cm sod plugs with optimum water and temperature in a darkroom and measuring etiolated mass per unit area. An improved sampling tool and mini‐darkrooms made by taping an inverted no. 10 (15‐cm diam.) can over a similar can containing sod plug at or near field capacity are described. A slight depression in the top of the can allows for air exchange but minimizes water loss. Dry matter reserves of 1.18 g for ‘Coastal’, 2.26 g for ‘Titian 78’, and 3.62 g for ‘Tifton 44’ bermudagrass [Cynodon dactylon (L.) Pers.], were measured with approximately one‐fourth less time needed to harvest, water, and retape the covers than for traditional methods.
Mutant Sunflowers with High Concentration of Saturated Fatty Acids in the Oil
Authors: Osorio J. , Fernández‐Martínez J. , Mancha M. , Garcés R.
Published: July 2010

Development of cultivars of sunflower (Helianthus annuus L.) with increased levels of saturated fatty acids could increase the utility of the oil for specific edible purposes. The primary objective of this research was to induce variability for these traits by using mutagenesis. Four sunflower mutants with altered seed fatty acid compositions have been isolated by screening single M2 and M3 seeds from plants obtained from mutagenized seeds utilizing ethyl methanesulfonate, sodium azide, and x‐rays. The mutant lines included CAS‐5, which has an oil with a fivefold increase (252 g kg−1) in palmitic acid (16:0) and the appearance of palmitoleic acid (16:1; 37 g kg−1); and CAS‐3, CAS‐4, and CAS‐8, which have from two to six times (99–260 g kg−1) the stearic acid (18:0) content normally observed in the oil of cultivated sunflower. The dramatic increase in levels of either 16:0 or 18:0 were at the expense of oleic (18:1) and linoleic (18:2) acids. The relative proportion of 18:1 to 18:2 varied with the mutants. All showed variation in fatty acid composition among the seeds of the original plant, which indicated that the fatty acid changes were controlled by the genotype of the embryo. The bimodal distribution in fatty acid composition of CAS‐3 and CAS‐5 seeds suggested that major recessive genes are involved in the control of these characters.
Confirmation of Nonsuppressor Mutation of Stem Rust Resistance in ‘Canthatch’ Common Wheat
Authors: Kerber E. R. , Aung T.
Published: July 2010

A mutation induced in the common wheat cultivar Canthatch (Triticum aestivum L.) results in resistance to several races of stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) to which Canthatch is susceptible. Previous evidence indicated the mutation behaved as a nonsuppressing allele on chromosome arm 7DL, which permitted the expression of resistance normally inhibited by a suppressor also located on 7DL. However, to eliminate the possibility that the improved resistance resulted from a mutation to a resistance gene, additional experiments were undertaken. Chromosome 7D of the susceptible caltivar Chinese Spring was substituted by the corresponding chromosome of the resistant mutant, Canthatch‐NS, and of Canthatch. Also, pentaploids were produced from crosses of susceptible tetraploids ‘Pelissier’ durum wheat and Tetraprelude with the resistant Canthatch mutant. The 7D substitutions of Canthatch‐NS and Canthatch, as well as the pentaploids, were fully susceptible. Consequently, the mutation induced in Canthatch‐NS was not of a resistance gene, thus confirming the previous conclusion that it behaves as a nonsuppressing allele.
Improvement of Winter Hardiness in Oat from 1935 to 1992
Authors: Livingston David P. , Elwinger Gerald F.
Published: July 2010

The Uniform Oat Winter Hardiness Nursery was initiated in 1926 to improve the probability of selecting more winter‐hardy oat (Avena sativa L.) germplasm under field conditions. The nursery has been grown at 141 locations in 31 U.S. states and four Canadian provinces and 986 cultivars and experimental lines have been tested. Survival data from 1935 to 1992 was used to (i) summarize nursery information, and (ii) evaluate progress in winter hardiness improvement. Analysis of variance (ANOVA) for 10 check cultivars revealed four hardiness categories. Analysis of the same 10 checks by the method of pairwise rank superiority confirmed the relative rankings from the ANOVA results. Regression analyses from more than 1000 location‐years in which differential winter killing occurred indicated significant genetic improvement in average winter hardiness of entries submitted for testing during the first 35 yr (1935 to 1970); the hardiness of elite entries has improved throughout the period of analysis (1935 to 1992) at an estimated rate of 0.26% per year. The decreased progress in average hardiness of entries since the mid1970s may be a result of reduced effort in breeding for winter hardiness due to lack of funding and/or exhaustion of genetic potential.