bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Methods of Measuring Thatch on a Creeping Bentgrass Green
Authors: Callahan Lloyd M. , Sanders William L. , Parham John M. , Harper Cynthia A. , Lester Lori D. , McDonald Ellen R.
Published: July 2010

Thatch accumulation continues to be a serious problem in densely grown close mowed turfgrass. Several methods are used to measure thatch, ranging from very rapid to very slow, with opinions differing concerning the reliability of the various methods. The objectives of these studies were to evaluate speed of use, precision, reliability, and the practicalities of two of the most commonly used methods of measuring thatch, which are slow, with those of a very rapid method. All three methods were evaluated as part of a field study to determine the effectiveness of mechanical and chemical treatments in controlling thatch on a creeping bentgrass (Agrostis palustris Huds.) green growing on a U.S. Golf Association (USGA) rootzone. Thatch control treatments were vertical mowing (4 and 8×/yr), coring (4×/yr), wetting agent (7×/yr), extra K (4×/yr), lime (4×/yr), and various combinations of these; and interactions of these with topdressing (3 and 6×/yr). Thatch measuring methods used were the ruler, total organic matter (OM) by loss‐on‐ignition, and a rapid surface sod compression instrument termed the Thatchmeter II. Treatments and measurements were conducted for 6 yr with results reported for the last 3 yr. The thatchmeter was easy to use, enabling a set of six readings per sub‐plot to be made much faster than one core sample could be cut and measured with a ruler. The OM method was tediously slow, taking days to complete, and measured only total OM by weight with no determination for depth. As a method relating to thatch depth, the thatchmeter and ruler methods correlated well with each other with the thatchmeter being more sensitive. The OM method did not correlate with either the thatchmeter or ruler. Based on data from this study, the thatchmeter appears to be the most reliable and practical of the three methods tested.
Molecular Tagging of the bc‐3 Gene for Introgression into Andean Common Bean
Authors: Johnson William C. , Guzmán Pablo , Mandala D. , Mkandawire A. B. C. , Temple S. , Gilbertson R. L. , Gepts P.
Published: July 2010

Alternative genes for resistance to Bean Common Mosaic Virus in common bean (Phaseolus vulgaris L.) are necessary as a result of the recent introduction of necrasis‐inducing strains of this virus into the USA. The recessive bc‐3 gene confers resistance against all known strains of this pathogen. We describe here experiments to develop a relatively easy‐to‐use procedure to introgress the bc‐3 gene into elite bean cultivars. First, we employedb ulked segregant analysis to identify RAPD markers linked to the bc‐3 locus. The ROCII/350/420 marker was codominant with the bc‐3 gene and the ROC20/460 marker was dominant and linked in trans. A survey of cultivated materials allowed us to identify the likely evolutionary origin of the bc‐3 resistance allele as a member of the Mesoameriean gene pool, probably of race Mesoamerica. Polymorphism of the RAPD markers in a Davis common bean mapping population (BAT93 ✕ Jalo EEP558) allowed us to map the markers and, by inference, the bc‐3 gene to linkage group D6. Second, we used sequence information from the cloned RAPD fragments to design longer, more reliable PCR primers that differentiate individuals homozygous for the resistance allele from susceptible genotypes in segregating populations of Andean origin. Third, we developed a marker tagging system that used a simplified DNAe xtraction technique and a PCR‐based assay to identify the genotype of common bean plants at the bc‐3 disease resistance locus. This simplified marker assisted selection system is expected to eliminate the need for costly quarantines and progeny tests in breeding programs for common be an of Andean origin.
Plant Breeding Progress and Genetic Diversity from De Novo Variation and Elevated Epistasis
Authors: Rasmusson D. C. , Phillips R. L.
Published: July 2010

Breeding programs in major crops normally restrict the use of parents to those improved for a variety of traits. Gain from utilizing these good × good crosses appears to be high, and improvements are sufficient to encourage continued breeding within narrow gene pools even though each cycle is expected to lead to reduced genetic variability. These finely tuned programs have gradually limited the amount of new diversity introduced into the breeding gene pool. This breeding strategy has led to a genetic gap where there is a large difference in the favorable gene frequency between the improved and unimproved lines and to a narrowing of genetic diversity within elite gene pools. At the same time, evidence has accumulated in plant breeding programs and long‐term selection experiments in several organisms that the genome is more plastic and amenable to selection than previously assumed. In the barley (Hordeum vulgare L.) case study reported here, incremental genetic gains were made for several traits in what appears, based on pedigree analysis, to be a narrow gene pool. Given this situation, we call for an examination of the generally held belief that the variation on which selection is based in elite gene pools is provided almost exclusively from the original parents. Classical and molecular genetic analyses have shown that many mechanisms exist to generate variation de novo, such as gene amplification and transposable elements. Accordingly, we put forward the hypothesis that newly generated variation makes an important contribution. We also hypothesize that gene interaction, epistasis, is more important than commonly viewed and that it arises from de novo generated diversity as well as the original diversity.
Cuphea viscosissima Mutants with Decreased Capric Acid
Authors: Knapp S. J. , Crane J. M. , Tagliani L. A. , Slabaugh M. B.
Published: July 2010

The range of medium‐chain oils produced by Cuphea viscosissima Jacq., a naturally rich source of capric acid (10:0), can be broadened by developing lines with increased caprylic (8:0), lauric (12:0), myristic (14:0) acid. Our objectives were to (i) describe the inheritance of a series of mutants with decreased 10:0 (CPR‐1, CPR‐2, CPR‐4, CPR‐5, and CLM‐1) and (ii) develop lines with fatty acid compositions different from other mutant lines. CPR‐1, CPR‐2, and CPR‐5 had ~310 g kg‐1 less 10:0 than the wild type (WT), whereas CPR‐4 had 62 g kg‐1 less 10:0 and CLM‐1 had 50 g kg‐1 less 10:0 than the wild type. We assayed the fatty acids of 100 progeny from 10 F2 populations segregating for one or more mutations. CPR‐1, CPR‐2, and CPR‐5 produced three non‐overlapping capric acid classes and segregated as single incompletely dominant mutations. CPR‐1 × CPR‐2 and CPR‐1 × CPR‐5 F2 progeny had continuous 8:0 and 10:0 distributions. The CPR‐1 × CPR‐5 cross produced several F2 progeny with atypical 8:0 and 10:0 phenotypes, while the CPR‐1 × CPR‐2 cross produced no F2 progeny different from either parent. CPR‐1 and CPR‐2 seem to be allelic mutations affecting the cpr locus. CPR‐5 could be an allele of the cpr locus or of a locus tightly linked to cpr. CPR‐4 × WT and CLM‐1 × WT F2 progeny had continuous 10:0 distributions. CPR‐1, CPR‐4, and CLM‐1 seem to be non‐allelic mutations. VS‐320, an F3 line developed from the CPR‐1 × CLM‐1 F2 population, had 334 g kg‐1 8:0 and 396 g kg‐1 10:0. VS‐321, an F3 line developed from the CPR‐4 × CPR‐5 F2 population, had 247 g kg‐1 8:0 and 361 g kg‐1 10:0. The 8:0 or 10:0 contents of these lines are lower or higher than previously reported for C. viscosissima.
Relationships between Seed Yield and Seed Protein in Determinate and Indeterminate Soybean Populations
Authors: Wilcox James R. , Guodong Zhang
Published: July 2010

The development of soybean [Glycine max (L.) Merr.] cultivars with high seed protein has been hampered by the inverse relationship between seed yield and seed protein concentration. Determinate and indeterminate near‐isolines of soybean are usually similar in seed protein but differ in growth type. This study was conducted to determine if relationships between seed yield and seed protein differed in populations of these two plant types. Determinate and indeterminate progenies were identified in two crosses between high‐protein indeterminate breeding lines and determinate strains with average seed protein. The F4‐derived progenies were evaluated for 2 yr in three‐replicate yield tests at West Lafayette, IN. Seed protein and oil concentration were determined on seed from individual entries in each replication. Mean seed protein concentrations were similar for the two plant types in each cross. Regression of seed protein on seed yield was not significant among determinate progenies in either cross. In contrast, negative slopes of regression lines were significant when seed protein was regressed on seed yield for indeterminate progenies in each cross. The three highest yielding determinate entries from one cross were similar in yield to the determinate cultivar Charleston and varied from 449 to 478 g kg−1 seed protein compared with Charleston with 420 g kg−1 protein. In the second cross, the three highest yielding determinate progenies were similar in yield to Charleston; two of these had higher seed protein than Charleston. The three highest yielding indeterminate lines in both crosses were similar in yield to the indeterminate check cultivars Edison and Flyer and varied in seed protein from 418 to 435 g kg−1 compared with 414 g kg−1 protein for Edison and 418 g kg−1 for Flyer. The data demonstrate that in these two crosses, determinate progenies were a better source of selections that combined high seed yield with high seed protein than were indeterminate progenies.
Effect of Salinity on Arginine Biosynthesis in Leaves of Phaseolus vulgaris L. P. acutifolius A. Gray
Authors: Lazcano‐Ferrat Ignacio , Lovatt Carol J.
Published: July 2010

The objective of this study was to quantify the effect of salinity on the capacity of leaves of Phaseolus vulgaris L. and P. acutifolius A. Gray to synthesize arginine de novo and to determine the relative ability of the two species to tolerate salinity during the vegetative growth phase. Research into the effect of salinity on P. acutifolius relative to P. vulgaris is limited. Plants were hydroponically cultured until age 5 d and then salinized for 16 d with 40 mM NaCl plus 20 mM CaCl2. Salination caused greater reduction (P < 0.05) P. acutifolius shoot dry weight (35 and 43% for two lines) than P. vulgaris [<25% for Linden and Ferry Morse 53 (FM 53) cultivars]. Root growth was unaffected in both species. Salt reduced the capacity of leaves of P. acutifolius to incorporate NaH14CO3 but not [14C]citrulline into arginine plus urea (ΣA + U) per gram fresh weight tissue (80% for both lines, P < 0.05). Arginine de novo synthesis in P. vulgaris was unaffected. Incorporation of NaH14CO3 into ΣA ÷ U was increased by added ornithine but remained lower (P < 0.05) in salinized P. acutifolius leaves than in control leaves, suggesting that ornithine availability was not the single factor limiting arginine de novo synthesis during salination. Salination reduced activities of glutamine synthetase and carbamylphosphaste synthetase per milligram protein in P. acutifolius (both lines, 50%) and FM 53 (20–40%) but not Linden. Thus,enzyme reaction(s) leading to the formation of citrulline in arginine de novo synthesis in leaves of P. acutifolius are more affected by salt than those in P. vulgaris.
Growth Analysis of Cotton Crops Infested with Spider Mites: I. Light Interception and Radiation‐Use Efficiency
Authors: Sadras Víctor O. , Wilson Lewis J.
Published: July 2010

Two‐spotted spider mites (Tetranychus urticae Koch) are important pests of cotton (Gossypium hirsutum L.). The effects of mites on cotton photosynthesis have been investigated at the leaf and cytological levels but not at the canopy level. Our objective was to quantify the effects of timing and intensity of infestation by mites on cotton radiation‐use efficiency (RUE). Leaf area, light interception, RUE, canopy temperature, and leaf nitrogen concentration (LNC) were assessed during two growing seasons in crops artificially infested with mites between 59 and 127 d after sowing. Normal and okra‐leaf cultivars were compared. A mite index (MI = natural log of the area under the curve of mite number vs thermal time) was used to quantify the cumulative effects of mites on RUE, LNC, and canopy temperature. Crop growth reduction due to mites was greater in early‐ than in late‐infested crops. Growth reduction was primarily due to reductions in RUE, but in the more severe treatments accelerated leaf senescence and, hence, reduced light interception also contributed to reductions in crop growth. At a given date, infested okra‐leaf crops usually had greater RUE than their normal‐leaf counterparts. Both plant types, however, responded similarly to a given level of mite infestation. The ability of the okra‐leaf cultivar to maintain greater RUE levels can be attributed, therefore, to its relative in hospitality for the development of mite colonies rather than to an intrinsically greater capacity to maintain photosynthesis under mite damage. Canopy temperature, LNC, and RUE showed a similar, biphasic pattern of response to MI. In the first phase, response variables were almost unaffected by mites. In the second phase, there was a marked decline in RUE and LNC and a marked increase in canopy temperature with increasing MI. These results suggest (i) some degree of compensatory photosynthesis at low to moderate levels of mite infestation, and (ii) reductions in RUE mite‐infested cotton crops involved alterations in both canopy gas diffusion and metabolic activity. Quantitative relationships between RUE and MI were developed that could be used to link mite and crop growth models.
Comparing Cultivars of Three Cool‐Season Turfgrass for Soil Water NO−3 Concentration and Leaching Potential
Authors: Liu Haibo , Hull Richard J. , Duff D. T.
Published: July 2010

A field study to compare soil water NO−3‐N concentration and cumulative NO−3 losses by percolation of 10 cultivars each of Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) was conducted at the University of Rhode Island Turfgrass Research Station, Kingston, between March 1990 and April 1992. All turf plots were established in 1985, 1986, or 1987 on an Enfield silt loam (Coarse loamy over sandy skeletal, mixed, mesic, Typic Dystrochrepts) under moderate N fertilization of 149 kg N ha−1 y−1. Soil water was collected at a depth of 60 cm to determine NO−3‐N concentration and annual cumulative NO−3 losses through leaching were determined by a hydrological model which estimates soil water percolation. Significant differences among species and cultivars were identified in soil water NO−3‐N concentration and NO−3 leaching potential based on monthly and seasonal analyses. These results indicate that genetic differences exist among turfgrasses for NO−3 utilization at both interspecific and intraspecific levels and suggest that a screening program could be developed to identify turfgrass cultivars having superior capacity to remove NO−3 from the soil and minimize the potential for NO−3 leaching.
Affinity of Anti‐lysergol and Anti‐Ergonovine Monoclonal Antibodies to Ergot Alkaloid Derivatives
Authors: Hill N. S.
Published: July 2010

The monoclonal antibodies previously used to determine the role of ergot alkaloids in fescue toxicosis have higher affinity to iysergic acid amides than to ergopeptine alkaloids. The objective of this research was to find monoclonal antibodies with uniform affinity to all ergot alkaloid classes. Balb/C mice were immunized with ergonovine‐protein conjugates. Splenic hybridoma cell lines were compared with current antibodies for cross reaction with lysergic acid amide and ergopeptine alkaloids. Antibodies from two cell lines had more uniform affinity to both ergot alkaloid classes and should be useful for determining the role of ergot alkaloids in fescue.
RAPD Characterization of Heterogenous Perennial Ryegrass Cultivars
Authors: Huff David R.
Published: July 2010

The number of cultivars of perennial ryegrass has steadily increased since the early 1960s. Perennial ryegrass has a self‐incompatible, cross‐pollinated breeding system and thus, each cultivar is a heterogeneous population of individual genotypes. The ability to accurately distinguish large numbers of genetically heterogeneous populations from one another, based solely on morphological data and agronomic performance, is limited. Random amplified polymorphic DNA (RAPD) markers offer a nearly unlimited supply of molecular traits on which to base distinctive characterizations of plant populations. Analysis of molecular variance (AMOVA) provides a statistical tool which partitions molecular marker variation within and among populations and performs significance testing of differences. The objective of this research was to survey RAPD marker variation within and among populations of perennial ryegrass to characterize breeding germplasm and commercial cultivars using AMOVA. A range of genetic diversity was represented by choosing 18 grass populations that included related crosses, derived selections, and unrelated ecotypes. For each population, 10 individuals were examined for 33 RAPD markers produced with two primers. Markers present in all individuals of a particular population but not present in any other individual of another population (fixed marker difference) were not observed among the 18 grass populations, so characterizations were based on marker frequency differences among populations. RAPD markers analyzed with AMOVA closely reflected the breeding histories of the perennial ryegrass germplasm or commercial cultivars. This was particularly true for relationships structured on a population basis. Results indicated that high selection intensity substantially altered the distribution of RAPD markers between parent and progeny populations thereby obscuring measurements of genetic relatedness. Furthermore, this study observed a limited ability to separate closely related populations. Evidence for the narrow germplasm base of turfgrass cuitivars was observed; although, many perennial ryegrass populations appeared to retain levels of within population variability comparable with that of land race ecotypes. The methods of analysis presented should provide a supplement to traditional morphological and agronomic data for plant variety protection and for measuring genetic diversity within breeding programs.
Genetic Diversity among North American Spring Wheat Cultivars: I. Analysis of the Coeffecient of Parentage Matrix
Authors: van Beuningen L. T. , Busch R. H.
Published: July 2010

Genetic diversity constitutes the raw material for plant improvement, and it can provide protection against genetic vulnerability to biotic and abiotic stresses. Our objectives were to determine patterns of relatedness using the coefficient of parentage (COP) matrix among 270 spring wheat (Triticum aestivum L.) cultivars and to compute mean COP values for major regional breeding programs. The collection included most important cultivars released during this century from Canada (47), the USA (133), and Mexico (90). Cluster analysis, based on the COP matrix, resulted in 20 major clusters of four or more entries and six small clusters of two cultivars each. The first three axes from a principle coordinate analysis of the interclnster COP matrix showed (i) group ofseven clu sters inc luding most har d red spring cuitivars (HRS) from the USA, and Canada (CWRS), based mainly on a ‘Marquis’ background, (ii) group ofnine int errelated clusters including most cultivars from CIMMYT (Mexico), (iii) interrelated clusters including mostly white wheats, and (iv) two small clusters including mostly old Canadian cultivars. Mean COP values were computed among cuitivars released during three successive time periods for major regional breeding programs. The CWRS cuitivars have become progressively more interrelated based on a Thatcher background. Average COP values (0.58 among modern cultivars) for this class were higher than values reported for winter wheat, barley (Hordeum vulgare L.), and oat (Avena sativa L.) gene pools. The HRS wheats showed a fairly high but slowly decreasing interrelatedness (COP= 0.22) among modern cultivars, with some regional differences. CIMMYT cultivars were less interrelated (COP = 0.15–0.20) and comparable to levels reported for soft red winter wheat and barley. Quality requirements and kernel type have probably been major factors in maintaining relatively high COP in the CWRS but somewhat less in the HRS in the USA. CIMMYT cultivars, in general, do not have quality restrictions, allowing the introduction of more diversity.
Evaluation of Tobacco Accessions for Resistance to Tobaco Cyst Nematode and Wildlife
Authors: Hayes A. J. , Wilkinson C. A. , Johnson C. S.
Published: July 2010

Control of tobacco cyst nematode (Globodera tabacum solanacearum Miller and Gray) is of major concern to growers of flue‐cured tobacco (Nicotiana tabacum L.) in Virginia. A diverse geographic array of accessions including cultivars of several classes of tobacco, flue‐cured type tobacco introductions, and Nicotiana species were evaluated during 1993 and 1994 in the greenhouse to identify new sources of resistance to tobacco cyst nematode (TCN). Six‐week‐old transplants were inoculated with 6000 TCN eggs from crushed cysts. An average of eight weeks after inoculation, a 1‐g sample of root was stained and vermiform, swollen, pyriform, and adult nematodes were counted. Accessions were also evaluated for response to wildfire (Pseudomonas syringae pv. tabaci Wolf and Foster) to determine if resistance to these two pathogens was correlated. The underside of a single 10‐ to 15‐cm leaf from 6‐wk‐old transplants was inoculated with a suspension of wildfire bacteria by means of a CO2 air brush. Leaves were rated for disease severity 5 d after inoculation. Several accessions had significantly reduced nematode reproduction including TI 1597, TI 1625, ‘Burley 64’, ‘MD 40’, ‘Pennbell 69’, and ‘Kutsaga Mammoth 10’. Although wildfire resistance was highly correlated with TCN resistance, some accessions had no resistance relationship to the two pathogens. Nicotiana miersii Ramy was susceptible to wildfire while supporting very low nematode populations and both TI 551 and ‘KY 190’ were resistant to wildfire but were susceptible to TCN. Evaluation of accessions for wildfire resistance may not be a reliable method of screening for TCN resistance and would result in alternate sources of TCN resistance being overlooked.
Gene Pool Classification of Common Bean Landraces from Chile Based on RAPD and Morphological Data
Authors: Johns Mitrick A. , Skroch Paul W. , Nienhuis James , Hinrichsen Patricio , Bascur Gabriel , Muñoz‐Schick Carlos
Published: July 2010

Landraces of common bean (Phaseolus vulgaris L.) from Chile are a phenotypically diverse group whose relationship to the two major gene pools (Andean and Mesoamerican) is unclear. The genetic composition of 69 Chilean landraces, 15 commercial cuitivars grown in Chile, and 11 previously characterized check accessions was examined using RAPDs (random amplified polymorphic DNA). The 25 primers used generated 106 polymorphic bands. A genetic distance (GD) matrix based on simple matching of RAPD phenotypes was converted to a two dimensional plot using multidimensional scaling (MDS). Two major clusters, encompassing most of the accessions, were apparent on the resulting plot and were identified with the Andean and the Mesoamerican gene pools. No obvious signs of introgression or hybridization between gene pools were observed. Clustering analysis using bootstrap samples of the RAPD bands showed that as few as 20 randomly chosen bands could classify the accessions into the correct gene pools nearly as well as all 106 bands. In general, the Andean landraces were collected at more northerly latitudes and higher altitudes than the Mesoamerican landraces. Morphological data were collected for 63 landraces for seven numerical traits and 13 categorical traits. The morphological data used were to create a distance matrix and analyzed as with the RAPD data, but no clear separation of the groups was seen. Accessions from the two groups identified by RAPDs differed significantly for 11 of the 20 traits examined. It was concluded that by RAPDs, the Chilean landraces could be readily classified into the Andean and Mesoamerican gene pools. Morphological traits were less effective at classification.
Application of Multiplex PCR and Flourescence‐Based, Semi‐Automated Allele Sizing Technology for Genotyping Plant Genetic Resources
Authors: Mitchell Sharon E. , Kresovich Stephen , Jester Christopher A. , Hernandez C. Javier , Szewc‐McFadden Amy K.
Published: July 2010

For future progress, effective conservation of plant genetic resources will require the integration of technologies and protocols that provide for the acquisition of large quantities of genetic information for improved gene and genotype identification. As a contribution to this integration, simple sequence repeat (SSR) marker analysis in Brassica spp. was evaluated as a prototype system for establishing the potential of multiplex polymerase chain reactions (PCRs) coupled with fluorescence‐ based DNA detection and semi‐automated sizing technology for mass genotyping of plant genetic resources. Consistent results were achieved for multiplex PCRs (simultaneous amplification of several genetic markers in a single reaction) with 11 fluorescently labeled primer pairs. Comparison of computer‐derived estimates of fragment sizes between gels demonstrated that automated sizing was accurate enough to achieve reliable and repeatable plant genotypes. To establish a genetic basis for putative SSR loci previously identified in Brassica spp., segregation data were analyzed. Three polymorphic SSRs in Brassica napus L. (canola and rapeseed) exhibited simple Mendelian inheritance and were not linked. One of these potymorphic loci was duplicated, i.e., a single copy marked each of the “aa” and “cc” genomes originating from progenitor species B. rapa and B. oleracea, respectively. Technologies that provide for high genetic resolution and throughput at reasonable costs will find ready application in plant genetic resources conservation. In addition, these same tools and marker systems can be applied to questions of pedigree analysis and intellectual property rights.
RFLP Genetic Similarity Estimates and Coefficient of Parentage as Genetic Variance Predictors for Soybean Yield
Authors: Manjarrez‐Sandoval P. , Carter Thomas E. , Webb D. M. , Burton J. W.
Published: July 2010

RFLP genetic‐similarity estimates (RFLP‐GS) and coefficient of parentage (CP) have been used as measures of genetic similarity within crop species. However, practical application of these measures in plant breeding remains uncertain. This study was designed to probe the utility of RFLP‐GS and CP in predicting genetic variance (GV) for seed yield among inbred soybean [Glycine max (L.) Merr.] lines. achieve this goal, five single seed descent populations were studied, representing a range of RFLP‐GS and CP between the parents from 57 to 75% and 0.06 to 0.5, respectively. The GV for yield was estimated for each population through field evaluation of 30 inbred lines per population, in two North Carolina field locations during 1994. Both RFLP‐GS and CP correctly identified the population with the highest GV; however, CP predicted GV for yield more efficiently (rCP.RFLP‐GS = 0.91*; rCP.GV = −0.81*; and rRFLP‐GS.GV = −0,58). The GV was near zero when the CP between parents was larger than 0.27 or when RFLP‐GS was larger than 75%. Neither genotype × environment interaction nor low field precision were factors for the lower predictive value of RFLP‐GS. Expected gains from selection agreed partially with RFLP‐GS results but closely matched CP and the actual fate of populations in a USDA breeding program. These results indicated that caution should be taken in an applied soybean breeding program when crossing parents with a relationship larger than half‐sib or when the RFLP‐GS is larger than 75% when yield improvement is the main breeding objective.
Nitrogen Effects on Striga hermonthica Infestation, Grain Yield, and Agronomic Traits of Tolerant and Susceptible Maize Hybrids
Authors: Kim Soon‐Kwon , Adetimirin V. O. , Akintunde A. Y.
Published: July 2010

A phytoparasite, Striga hermonthica (Del.) Benth., infests millions of hectares of cultivated fields of cereal crops in sub‐Saharan Africa. Yield losses are often 70 but can be as high as 100% and farmers often abandon infested fields and move to new areas. The objectives of this study were to investigate the effects of nitrogen on S. hermonthica infestation and the subsequent grain yield and agronomic traits of tolerant and susceptible maize hybrids (Zea mays L.). Two tolerant and two susceptible hybrids were grown under six levels of N (0–150 kg ha−1), with and without Striga seed infestation. The trials were conducted for 3 yr at Mokwa, Nigeria. Each plant was infested with approximately 3000 germinable Striga seeds, and the density of Striga that emerged, Striga damage on the host plant, plant height, stalk lodging, and grain yield were measured. Striga infestation (emergence and host damage), maize grain yield, and plant height were significantly affected by N rates. Two tolerant hybrids showed significantly lower Striga emergence and host plant damage symptoms than the susceptible hybrids (P< 0.001). Interactions between infested and uninfested plots and hybrid (tolerant vs. susceptible) for grain yields and stalk lodging were significant (P < 0.001). Striga infestation reduced grain yields of two susceptible hybrids by 49%, and of two tolerant hybrids by 24%. The two tolerant hybrids produced on average 87% greater grain yields than the two susceptible hybrids under low N rates (0– 60 kg ha−1) and 51% greater yields under high N (90–150 kg ha−1). Among the plant traits measured, Striga damage score had the highest correlation with grain yield (r = − 0.60**).
Inheritance of Latent Period of Puccinia recondita in Wheat
Authors: Shaner Gregory , Buechley George , Nyquist Wyman E.
Published: July 2010

Long latent period, a major component of slow leaf‐rusting resistance in wheat (Triticum aestivum L.), was studied in the progeny of a cross between cultivars CI 13227 and Suwon 92. F2 plants and F3‐and F6‐derived F7 families, each derived from a different F2 plant by single‐seed descent, were evaluated for latent period of infection by Puccinia recondita Roberge ex Desmaz. There was a wide range in latent period among F2 plants and highly significant differences in latent period among families. The distributions of latent period for F2 plants and F3 and F7 family means were skewed to the right, and population means were significantly below midparental values. The data suggested that four loci with epistatic effects controlled latent period. Because approximately three‐fourths of the F7 families had values below the midparental value, it appeared that a gene at one of the four loci exerted a major effect on latent period. Although latent period is a quantitative trait, narrow‐sense heritability of an F2 individual was fairly high, ranging from 0.64 to 0.98, and the trait could be measured with acceptable precision by visual estimation of the percentage of infection sites that had erupted into pustules at each day after inoculation. Selection for the trait could begin in the F2 generation, but desirable phenotypes will continue to segregate in later generations from somewhat susceptible plants, so it may be advisable to carry bulk populations for several generations from which fairly homozygous, slow rusting plants may be selected.
Heritability of Resistance to Web Blight in Five Common Bean Populations
Authors: Montoya C. A. , Beaver J. S. , Rodríguez R. , Miklas P. N. , Godoy‐Lutz G.
Published: July 2010

Common bean (Phaseolus vulgaris L.) production in the humid tropics would benefit from the selection of cultivars with greater levels of resistance to web blight, a devastating disease caused by Rhizoctonia solani Kühn. This will require screening techniques that are sensitive enough to detect moderate levels of resistance. Greenhouse experiments evaluated the effectiveness of a droplet inoculation technique for screening five F5:6 segregating populations for resistance to web blight. Another objective was to estimate the heritability of resistance to web blight in five common bean populations. Significant differences in lesion size were detected among F6 lines within each population. Lines with less web blight infection than the resistant parent MUS83 were observed in each population. This suggests that both parents contributed to the resistance of the progeny. Narrow sense heritability estimates for web blight reaction ranged from 0.61 to 0.79. These relatively high heritabilities suggest that selection for smaller lesion size may be effective in earlier generations when MUS83 is used as a source of resistance to web blight. Physiological resistance to web blight, as measured by lesion size by means of the droplet inoculation technique, will need to be combined with disease avoidance traits such as erect architecture to obtain effective resistance in the field. Five lines from the MUS83 × DOR483 population with smaller lesion sizes in the greenhouse had moderate to low levels of web blight infection in field experiments conducted in Puerto Rico and the Dominican Republic.
Dry Matter Allocation and Fruiting Patterns of Cotton Grown at Two Divergent Plant Populations
Authors: Jones Michael A. , Wells Randy
Published: July 2010

Reduced plant populations frequently occur in the northern Cotton Belt of the USA because of poor seed germination and early seedling damage. A field study was conducted at Clayton, NC, on a Dothan sandy loam (fine‐loamy, siliceous, thermic Plinthic Paleudult) to investigate the response of cotton (Gossypium hirsutum L.) vegetative and reproductive development to two plant populations. Cotton plants, grown at 2 and 12 plants m−2 in 1.0‐m rows had every flower tagged with week‐specific, color‐coded tags. Dry matter partitioning, flower development, flower retention, and boll development patterns were determined. Plants at the low population exhibited large increases in the vegetative dry weight of individual plants at maturity; however, all parameters of vegetative growth were reduced on a land area basis. Reproductive development of the 2 plants m−2 treatment was prolonged because of fewer early fruiting sites per unit land area and there was an average 16‐d delay in flowering maxima. No differences in total flowers per meter or flower retention occurred between treatments at final harvest. Slight differences in total bolls per meter occurred in 1993 (13% fewer bolls at 2 plants m−2); however, the low population plants had more bolls on monopodia, more late‐season flowers, and greater retention of these late bolls. Replanting low populations would not be advisable because the delay in maturity would probably be more injurious to boll production than the low population per se.
Floral Bud Removal from Specific Fruiting Positions in Cotton: Yield and Fiber Quality
Authors: Heitholt J. J.
Published: July 2010

Lint from cotton (Gossypium hirsutum L.) bolls produced on proximal fruiting positions (FP) is often longer and more mature than lint from distal FP sites. The objective of this research was to quantify the effects of proximal or distal floral bud removal on yield, yield distribution, yield components, and fiber properties. Cotton (cv. Deltapine 5415) was grown in the field near Stoneville, MS, in 1993 and 1994. From first square to late bloom, young squares (floral buds) were removed from selected positions twice weekly. The most proximal FP was designated FP1, the second most proximal FP was designated FP2, etc. The three treatments were (i) check (no removal), (ii) P1 (FP2, FP3, and greater squares removed), and (iii) P2, (FP1 and FP3 and greater squares removed). Averaged across years, a greater percentage of bolls (82 vs. 68%) and larger bolls (1.61 vs. 1.50 g lint boll−1) were found at FP1 on the P1 treatment than on the check. A greater percentage of bolls (42%) were found at FP2 on the P2 treatment, than in other treatments (10‐24%). Lint yield (all bolls) the check (1090 kg ha‐−1) was 11 and 28% greater than the P1 and P2 treatment, respectively. In contrast to yield, composite fiber micronaire, maturity, and wall thickness were significantly greater (5‐6%) in the P1 and P2 treatments than the check treatment. Fiber length and strength were unaffected by treatment. These results suggest that cotton may not be able to achieve its full yield potential if limited to one boll per main stem node. The increases in fiber properties were small and probably not economically important.
CIMMYT's Genetic Progress in Wheat Grain Quality under Four Nitrogen Rates
Authors: Ortiz‐Monasterio J. I. R. , Peñna R. J. , Sayre K. D. , Rajaram S.
Published: July 2010

Wheat (Triticum aestivum L.) breeders often try to simultaneously improve grain yield and bread‐making quality. This study examined changes in CIMMYT's wheat germplasm with respect to grain protein concentration (GPC)‐ and grain protein quality (GPQ)‐related parameters and assessed the importance of these parameters in determining bread‐making quality, when wheat cultivars were grown with 0, 75, 150, or 300 kg N ha−1. A 3‐yr field study was established with 10 cultivars representing breeding progress from 1950 to 1985. Flour protein concentration (FPC), sodium dodecyl sulfate‐sedimentation (SDS‐S), alveogram W (ALVW), alveogram P/G (ALVPG), bread loaf volume (LV), and GPC were evaluated. At low N (0 and 75 kg ha−1), there was no difference in GPC among cultivars. In contrast, at higher N (150 and 300 kg ha−1), there was a linear reduction GPC with respect to the year of release. However, when the two tall, older cultivars and cv. Siete Cerros 66, an outlier, were removed from the analysis, there was a negative trend between GPC and year of release but only at the 300 kg N ha−1 level. There was no linear trend in year of release for GPQ parameters or LV. Loaf volume was most consistently correlated with SDS‐S across the different levels of N compared with GPC, FPC, ALVW, or ALVPG. However, GPC and LV showed a highly significant correlation only when the two soft wheat cultivars were removed from analysis. Use of semidwarf germplasm in CIMMYT's wheat breeding program initially resulted in increased grain yield and reduced GPC. However, during the period of semidwarf improvement, increasing grain yield was possible while maintaining GPC, except under high levels of N application.
Genetic Progress in Wheat Yield and Nitrogen Use Efficiency under Four Nitrogen Rates
Authors: Ortiz‐MonasterioR J. I. , Sayre K. D. , Rajaram S. , McMahon M.
Published: July 2010

The adaptation and performance of CIMMYT's bread wheat germplasm (Triticum aestivum> L.) under conditions of low N fertility have been questioned because they were developed under medium‐high levels of N fertility. The objectives of this research were to (i) compare the performance of a set of tall vs. semidwarf cultivars developed by CIMMYT that were widely grown by farmers in the Yaqui Valley of Mexico at low and high N fertility, (ii) measure the genetic progress in grain yield and N use efficiency (NUE), and (iii) evaluate the contribution of N uptake efficiency (UPE) and utilization efficiency (UTE) to NUE. Ten wheat cultivars, two tall and eight semidwarf, produced by CIMMYT and released in the Yaqui Valley of Sonora, by the Mexican government from 1950 to 1985 were grown with 0, 75, 150, or 300 kg N ha−1 in a 3‐yr field study at Ciudad Obregon, Sonora, Mexico. Genetic gains in both grain yield and NUE during 1950 to 1985 were 1.1, 1.0, 1.2, and 1.9% yr−1 on a relative basis or 32, 43, 59, and 89 kg ha−1 yr−1 on an absolute basis, when provided 0, 75,150, and 300 kg ha−1 N, respectively. Progress in NUE resulted in an improvement of both UPE and UTE. However, the relative importance of these two components was affected by the level of applied N. These results contradict the belief that modern semidwarf cultivars require more N than older cultivars. Instead, they respond more to N, which translates into higher economic rates and higher returns when N fertilizer is available.
Phytic Acid in Triticale Grains As Affected by Cultivar and Environment
Authors: Feil Boy , Fossati Dario
Published: July 2010

Information on phytic acid in triticale (× Triticosecale Wittm.) grains is scarce; reports on triticale and the triticale parent wheat (Triticum aestivum L.) are conflicting. The present paper attempts to answer the following questions: (i) How are the concentrations of phytic acid‐phosphorus (PA‐P) and total phosphorus (TP) related among triticale cultivars? (ii) To what extent do triticale cultivars differ in their PA‐P percentage of TP? (iii) Are cultivar differences in the proportion of PA‐P to TP consistent across sites and years? (iv) Do environmental conditions (locations and years) affect the fraction of PA‐P in TP? To answer these questions, 10 hexaploid winter triticale cultivars‐lines were grown in western Switzerland. Using cultivar means of 2 yr, we observed positive relationships between the concentrations of TP and PA‐P among five short (r = 0.74; P = 0.15) and five tall (r = 0.92; P < 0.05) cultivars‐lines. Cultivar‐line means of the fraction of PA‐P in TP ranged from 65.2 to 70.8% (short cultivars) and from 67 to 70.9% (tall cultivars). Pooled across the 10 cultivars‐lines and 2 yr, 68.7% of TP was present as PA‐P. Two lines were grown at two additional locations for 2 yr. Line differences in the proportion of PA‐P to TP were consistent across the six environments. The share of PA‐P in TP was significantly affected by cropping year but unaffected by location and the year × location interaction.
Convergent‐Divergent Selection for Seed Production and Forage Traits in Orchardgrass: III. Correlated Responses for Forage Traits
Authors: Casler M. D. , Berger C. C. , Carlson I. T. , Sleper D. A.
Published: July 2010

Most orchardgrass (Dactylis glomerata L.) cultivars are developed in a two‐stage selection protocol. Stage 1 involves selection for agronomic traits among spaced plants and Stage 2 involves selecting among a limited number of clones based on their polycross progeny performance, usually in sward plots. The objective of this study was to quantify genetic progress in sward‐plot forage yield and related traits of four orchardgrass populations subjected to two cycles of recurrent phenotypic selection for agronomic traits of spaced plants. Selection was conducted at four locations, using either a regional approach (convergent‐divergent) or selection for local adaptation at one location. Selection criteria varied among locations, depending on the local environment and each breeder's goals. Convergent‐divergent selection led to a 7 and 8% increase in forage yield of the MO2 and WO11 populations, respectively, averaged over all evaluation locations. Local selection did not lead to forage yield improvement for any population. Both selection methods led to decreased rust reaction in at least two of the four populations and later maturity in all four populations. The improvements in forage yield appeared to be due partly to populational buffering among progeny of plants selected at different locations, a phenomenon not possible within the local populations because of single‐location selection. These results indicate that selection for agronomic traits of spaced plants in orchardgrass can lead to improved sward‐plot forage yield across a wide range of environments when multiple‐location selection is applied to some germplasms.
Identification of Field Corn Inbreds Adapted to Europe to Improve Agronomic Performance of Sweet Corn Hybrids
Authors: Malvar R. A. , Cartea M. E. , Revilla P. , Ordás A.
Published: July 2010

Elite American and European field corn inbreds (Zea mays L.) could improve the agronomic value of sweet corn for European conditions. The choice of field corn inbreds for improvings weet corn performance can be accomplished by a variety of methods. Our objectives were to identify American and European field corn inbreds adapted to European conditions as potential donors for improving yield and agronomic performance of sweet corn hybrids, and to provide additional information on the relationships among different estimators of favorable alleles when the donor lines show better performance than the inbred lines to be improved. Eleven field corn inbreds were crossed to seven sweet corn inbreds that were parents of seven sweet corn hybrids. The field × sweet corn hybrids and inbreds were evaluated separately in field trials at two locations in northwesternS paini n 1993 and 1994. Yield and four agronomic traits were recorded. Estimates of the relative number of alleles at six classes of loci (B, C, D, E, F, and G) were computed, and the methods for identifying field corn inbreds with favorable alleles were an estimate of favorable dominant alleles present in the donor but not in the hybrid (μG’), predicted threeway cross (PTC), minimum upper bound (UBND), net improvement (NI), probability of net gain of favorable alleles given complete dominance (PNGg)and given partial dominance or complementarye pistasis (PNGceg), and general combining ability (GCA). Correlations between μG’, UBND, PTC, NI, and GCA were very high for all traits. The field corn inbreds A632, EP42, and EP29 were identified as the best potential donors for improving yield and several yield components of sweet corn hybrids. European flint inbreds offer new possibilities for improving the agronomic value of sweet corn and its adaptation to cold areas with short growing seasons.
Genotype × Environment Interactions for Resistance to Common Scab in Tetrapioid Potato
Authors: Haynes K. G. , Goth R. W. , Young R. J.
Published: July 2010

Common scab of potato (Solanum tuberosum L.), caused by the soil‐borne bacterium Streptomyces scabies (Thaxter) Lambert & Loria, is an economically important potato disease. Tubers from susceptible plants may have superficial, raised, or pitted lesions. Quantitative methods to evaluate tubers for the amount of surface area covered (AI) and the type of lesion (LI) have previously been developed. The purposes of this study were to (i) estimate broad‐sense heritability on a mean basis for scab resistance in a tetraploid population of Solanum tuberosum for AI and LI, (ii) determine the importance genotype × environment interactions on AI nd LI, and (iii) determine the stability of potato genotypes for scab resistance. In 1992 and 1993, 23 potato clones were grown in replicated scab‐infested field plots in Presque Isle, ME, and Cranesville, WV, and rated for AI and LI. There were significant environment, genotype, and genotype × environment efftects for AI and LI. Broad‐sense heritabilities on a mean basis and their exact 95% confidence intervals for AI and LI wer estimated as 0.89 (0.78, 0.95) and 0.93 (0.86, 0.97), respectively. Shukla's stability‐variance statistics indicated that the most scab resistant genotypes were the most unstable, whereas, the most susceptible genotypes were the most stable. Thus, disease pressure was intense. Moderate levels of scab resistance were found. However, to obtain genotypes with high levels of scab resistance that are stable across environments will probably require development of populations incorporating new sources of scab resistant germplasm.