bluuebunny/crossref_metadata_2025 huggingface dataset:
QTL Mapping in Tropical Maize: III. Genomic Regions for Resistance to Diatraea spp. and Associated Traits in Two RIL Populations
Authors: Groh S. , González‐de‐León D. , Khairallah M. M. , Jiang C. , Bergvinson D. , Bohn M. , Hoisington D. A. , Melchinger A. E.
Published: July 2010

The southwestern corn borer (SWCB, Diatraea grandiosella Dyar) and sugarcane borer (SCB, Diatraea saccharalis Fabricius) are two related insect species that cause serious damage in maize production in subtropical and tropical regions of Central and Latin America. We analyzed quantitative trait loci (QTL) involved in resistance to the first generation of both borer species in two recombinant inbred line (RIL) populations from crosses CML131 (susceptible) × CML67 (resistant) and Ki3 (susceptible) × CML139 (resistant). Resistance was evaluated as leaf feeding damage (LFD) in replicated field trials across several environments under artificial infestation. Leaf protein concentration and leaf toughness were evaluated in one environment as putative components of resistance. The method of composite interval mapping was employed for QTL detection with RFLP linkage maps derived for each population of RIL. Estimates of the genotypic and genotype × environment interaction variances for SWCB LFD and SCB LFD were highly significant in both populations. Heritabilities ranged from 0.50 to 0.75. In Population CML131 × CML67, nine and eight mostly identical QTL were found for SWCB LFD and SCB LFD, respectively, explaining about 52% of the phenotypic variance () for each trait. In Population Ki3 × CML139, five QTL for SWCB LFD were detected, explaining 35.5% of . Several of these QTL were found in regions containing QTL for leaf protein concentration or leaf toughness. A low number of QTL in common between the two RIL populations and between RIL and corresponding populations of F2:3 indicated that the detection of QTL depended highly on the germplasm and population type. Consequently, chances of successful application of marker‐based selection (MBS) for corn borer resistance are reduced when QTL are not identified in the germplasm in which the final selection will be carried out.
Twenty‐Seven Cycles of Divergent Mass Selection for Ear Length in Maize
Authors: Lopez‐Reynoso Jose de Jesus , Hallauer Arnel R.
Published: July 2010

Knowledge of the associations between yield and its components is fiseful in selection among and within progenies. Twenty‐seven cycles of divergent mass selection for ear length in maize (Zea mays L.) were completed in the Iowa Long Ear Synthetic (BSLE) cultivar determine the effect of ear length selection on grain yield. The original population, selected cycles, and their crosses were evaluated at five Iowa sites for 2 yr to estimate direct and correlated responses to selection. S1 lines from the original population and from the 24Th cycles of selection were evaluated to determine the effect of selection on the genetic variability for ear length and correlated traits. Divergent mass selection was effective to modify ear length: ear length increased 1.4% (b1 = 0.27 cm ± 0.03) cycle−1 of selection for longer ears and decreased 1.9% (b1 = −0.37 cm ± 0.03) cycle−1 of selection for shorter ears. Selection for shorter ears was accompanied by a significant decrease of grain yield of 1.7% (b1 = −0.08 Mg ha−1 ± 0.01) cycle−1 of selection, with no change in yield with selection for longer ears. Selection for shorter ears significantly increased kernel‐row number per cycle (b1 = 0.11 ± .01) and ear diameter (b1 = 0.10 cm ± 0.01); whereas, selection for longer ears significantly reduced kernel‐row number per cycle (b1 = −0.06 ± 0.01) and ear diameter (b1 = −0.20 cm ± 0.01). No heterosis was observed in the crosses between corresponding cycles of selection. There was some evidence that genetic variation had decreased with selection.
Effects of the Dt2 and S Alleles on Agronomic Traits of F1 Hybrid Soybean
Authors: Lewers K. S. , St. Martin S.K. , Hedges B. R. , Palmer R. G.
Published: July 2010

Agronomic evaluation of F1 hybrid soybean [Glycine max (L) Merr.] will be useful for germplasm evaluation, recurrent selection, and estimating heterosis. We anticipated that vegetative heterosis, commonly observed in soybean, could increase early lodging and pod abortion, reducing grain yield. Under these circumstances, observed hybrid grain yield would not reflect the true potential of the hybrid as expressed in later generations. The Dt2 (semideterminate stem type) and S (short internode stem type) alleles have been shown to reduce excessive vegetative growth and lodging in narrow‐row production of inbred soybean. Our objectives were (i) to determine the per se effects and effects on heterosis, for agronomic traits, of the semideterminate (Dt2_) and short (S_) stem types in hybrid soybean, (ii) to assess their potential in facilitating germplasm evaluation and recurrent selection, and (iii) to determine if either stem type would be agronomically desirable in commercial hybrid soybean production. Near‐isogenic inbred lines and hybrid (F1) lines were evaluated replicated three‐row plots. The Dt2 and S alleles affected agronomic traits of hybrids and inbreds similarly. The Dt2 and S alleles hastened maturity, decreased plant height and lodging, and increased harvest index per se values. The Dt2 allele decreased seed weight and protein content. Both the per se and heterosis data suggest that the Dt2 and S alleles would not be consistently beneficial to germplasm evaluation or recurrent selection. The per se data suggest that the S allele might be useful for both inbred and commercial hybrid soybean.
Detection of Quantitative Trait Loci for Grain Yield and Yield Components in Maize across Generations in Stress and Nonstress Environments
Authors: Austin David F. , Lee Michael
Published: July 2010

Grain yield is the primary trait of interest in maize (Zea mays L.) breeding programs, but its evaluation is complicated by genetic heterogeneity, a complex biological basis, and genotype ✕ environment interactions. Genetic mapping studies of grain yield and yield components, with common sets of DNA marker loci and different populations evaluated across a range of environments, might identify regions of the genome associated with more or less consistent effects in different genetic and environmental contexts. Our objective was to evaluate the consistency of quantitative trait loci (QTL) detection for grain yield and four yield components in maize across stress and nonstress environments. One hundred eighty‐five F6:7 lines from a cross between inbred lines Mol7 and H99 were evaluated in two climatically diverse years at the same location. The stress environment was characterized by cool, wet conditions and a 56% reduction in grain yield relative to the nonstress environment. Over all five traits, 59 QTL were detected in at least one of the two environments with 10 being detected in both environments. Thirty‐two (54%) of the QTL were detected in the mean environment, and an additional eight QTL were detected in the mean that were not detected in either of the individual environments. Comparison of the F6:7 mean environment QTL with the mean environment (same location, different years) results from the F2:3 generation of the same population revealed 13 of 40 QTL detected in the F2:3 were verified in the F6:7 generation. Little evidence of cross‐over type QTL interactions was observed, and QTL ✕ environment interactions seem to be in the form of change in magnitude of effects.
Agronomic Performance of Quackgrass and Hybrid Wheatgrass Populations
Authors: Casler M. D. , Goodwin W. H.
Published: July 2010

Quackgrass [Elytrigia repens (L.) Nevski] is troublesome wed that has found recent use as a parent in interspecific hybrids with other Triticeae grasses. The objective of this research was to determine the potential of quackgrass and interspecific hybrid populations, involving quackgrass as a parent, for use as forage crops in the northcentral USA. Field experiments were conducted between 1988 and 1995 at Arlington and Marshfield, WI to compare six quackgrass and four hybrid wheatgrass populations to check cultivars of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leysser), timothy (Phleum pratense L.), tall fescue (Festuca arundinaceaSchreber), and reed canarygrass (Phalaris arundinacea L.). Under relatively normal to dry conditions, both quackgrass and hybrid wheatgrass had forage yields (7.56–7.77 Mg ha−1) in the middle of the range of most other species (5.03–8.94 Mg ha−1). However, on wetter soils, both quackgrass and hybrid wheatgrass had forage yields (6.28–6.39 Mg ha−1) similar to the means of the lowest yielding culfivars of the cultivated species (5.51–6.81 Mg ha−1). While quackgrass was reasonably adapted to mixtures with legumes, showing a mean grass concentration (492 g kg−1) within the range of cuitivars (355–563 g kg−1), hybrid wheatgrass was unadapted to mixtures with legumes, with grass concentration seldom greater than natural levels (43–75 g kg−1) and decreasing with age. Large genotype × environment interactions and differential adaptation of strains will limit the effectiveness of programs to recommend the use of either quackgrass or hybrid wheatgrass as cultivated forage crops in the north‐central USA.
Variation for Yield, Water‐Use Efficiency, and Canopy Morphology among Nine Alfalfa Germplasm
Authors: Ray Ian M. , Townsend M. Shaun , Henning John A.
Published: July 2010

Alfalfa (Medicago sativa L.) production under irrigated and rainfed conditions may benefit from improvements in water‐use efficiency (WUE), the amount of forage and root biomass produced per unit of water transpired. If benefits from improved WUE are to be realized, correlations between important agronomic traits and key physiological traits associated with WUE must be determined. This study characterized variation for dry matter yield, forage maturity, leaf‐to‐stem ratio (LSR), carbon isotope discrimination (Δ), canopy temperature, ash content, and specific leaf mass (SLM) in alfalfa. Associations between traits were also determined. Nine alfalfa germplasms representing eight of the nine historical genetic diversity groups, and a very fall‐dormant (YFD) population, were established in seeded, irrigated plots for 2 yr near Las Cruces, NM. Significant variation (P ≤ 0.10) was detected for all traits and was greatest for Δ and maturity, intermediate for yield, canopy temperature, ash content, and LSR, and least for SLM. The African, Peruvian, and Indian germplasms exhibited a higher Δ than either the Turkistan, YFD, M. varia Martyn., or Ladak germplasms. Carbon isotope discrimination was positively correlated with forage yield (r = 0.64; P ≤ 0.10; n = 9) and forage maturity (r = 0.66; P ≤ 0.05; n = 9). No association was detected between Δ and either canopy temperature, ash content, SLM, or LSR. The results indicate that differences in stomatal conductance or photosynthetic capacity exist among the nine populations, and that germplasms with low Δ tended to have slower growth and development rates under irrigated conditions. Neither canopy temperature, ash content, nor SLM provided suitable alternate measurements of A among the nine alfalfa germplasms.
Introgression of Day‐Neutral Genes in Primitive Cotton Accessions: II. Predicted Genetic Effects
Authors: McCarty J. C. , Jenkins J. N. , Zhu J.
Published: July 2010

Primitive accessions of cotton, Gossypium hirsutum L., may provide useful traits for cultivar development. Genetic effects for yield, yield components, and fiber traits were analyzed for five generations of day‐neutral progenies. The genetic material was derived from introgressing day‐neutral genes from ‘Deltapine 16’ into 16 primitive accessions with single and multiple backcrosses creating 80 populations representing one to four doses of the unadapted accession. Yield and fiber traits were determined from field plot studies conducted for 3 yr. Significant accession effects were detected for all the traits studied. Significant generation main effects were found for three yield traits and one fiber trait. As expected, yield was predicted to decrease with more cycles of backcrossing to the accession. Accessions × generation interactions were detected for some traits which indicated that not all generations were having equal effects. This genetic analysis provides useful information when utilizing these accessions.
Expected Inbreeding with Recurrent Selection in Maize: I. Mass Selection and Modified Ear‐To‐Row Selection
Authors: Márquez‐Sánchez Fidel
Published: July 2010

Maize breeders reduce inbreeding either by increasing the number of selected units or by intermating unrelated selection units. To determine optimal sample size for selection, one needs explicit functions to estimate the expected inbreeding in recurrent selection. The objectives of this study were to develop functions for mass (MS) and modified ear‐to‐row selection (METRS) in maize (Zea mays L.). By considering the number of half‐sib families and the number of plants per family, the initial inbreeding of the base population, and the intraand inter‐family coancestries, I obtained a basic equation to calculate in breeding. Knowledge of the basic population origin permitted me to extend inbreeding and coancestries of this population to any randomly mated advanced cycle of selection. Then the actual number of plants in the selection plot was transformed into the variance effective number for MS and METRS, proposed for sampling half‐sib families from an open‐pollinated population. The actual number of plants was also transformed into inbreeding effective number proposed for absence of selfing in both MS and METRS, and proposed for different numbers of males and females in METRS. Since the variance effective population size is a function of selection pressure, it was possible to obtain a general equation that included the numbers of sampled families, plants per family, and selected plants for any cycle of selection. for commonly used numbers of families, and plants per family,and selection pressures, inbreeding due to fixation by the variance effective number was very low; less than 7% for both selection methods even with 100 cycles of selection.
Inheritance of Ear Resistance to European Corn Borer in ‘Apache’ Sweet Corn
Authors: Warnock D. F. , Davis D. W. , Gingera G. R.
Published: July 2010

European corn borer, Ostrinia nubilalis (Hǖbner), can severely affect commercial sweet corn (Zea mays L.) quality during years of heavy infestation. Greater ear resistance in sweet corn could reduce the need for insecticide application. A generation mean analysis was used to determine the inheritance of ear resistance and silk‐channel length (SCL) in two crosses containing germplasm from the resistant sweet corn hybrid ‘Apache’. Three inbred parents, F1, F2, and the first backcross populations were manually infested and visually evaluated in field experiments. For each cross, ear damage, SCL, and number of surviving larvae differed (P ≤ 0.05) among generations. The genetic effects affecting the variation for ear resistance ranged from epistatic (Cross 1) to additive‐dominance (Cross 2). Silk‐channel length was controlled by epistatic (Cross 1 and Cross 2) effects. Inheritance of these traits is complex, probably involving multiple genes. As the silk channel often is the point of larval entry, SCLs were hypothesized to be important in ear resistance. The low to moderate correlations (P ≤ 0.01) across generations within each cross between ear damage and SCL (r = −0.18 and −0.75), surviving larvae (r = 0.78 and 0.79), and number of larvae in each third of the ear (r = 0.64−0.84) suggest that extending the SCL is not the sole component responsible for ear resistance.
Ancestral Origins and Genetic Diversity of Cultivated Sunflower: Coancestry Analysis of Public Germplasm
Authors: Cheres Mercy T. , Knapp Steven J.
Published: July 2010

Cultivated sunflower (Helianthus annuus L.) seems to have originated from a small number of ancestral germplasm sources. The number of key ancestors and how much each ancestor has contributed to the genetic diversity of public inbred lines is not known. We used coancestry analysis to assess this. The pedigrees of publicly released inbred lines were traced as far back as possible. Coancestries were estimated among 106 oilseed and 50 confectionery inbred lines and 157 ancestral germplasm sources. Cluster and principal component analyses of the coancestry matrix separated lines into broad market (oilseed versus confectionery) and fertility restorer (restorer versus maintainer) classes. There were four subgroups among oilseed maintainer lines (B‐lines) and three subgroups among oilseed restorer lines (R‐lines); however, the R‐line subgroups were heterogeneous and the boundaries between them were not sharp. These B and R subgroups may constitute heterotic groups. Sixty‐eight percent of oilseed R‐line diversity traced to seven germplasm sources, while 73% of oilseed B‐line diversity traced to eight germplasm sources. Seventy‐three percent of confectionery R‐line diversity traced to two germplasm sources, while 65% of confectionery B‐line diversity traced to four germplasm sources. The mean coancestry between oilseed R‐lines was 0.25, between oilseed B‐lines was 0.10, between confectionery Rlines was 0.31, and between confectionery B‐lines was 0.25; thus, the genetic diversity among oilseed B‐lines seems to be wider than among lines within other groups. Pedigree analysis created a nearly complete framework of heterotic groups for public germplasm developed in the USA, even though some lines could not be assigned to heterotic groups because of incomplete pedigree data. By combining pedigree and DNA fingerprint data, a more comprehensive picture of heterotic groups should emerge for cultivated sunflower.
Resistance to Southwestern Corn Borer in Corn after Anthesis
Authors: Williams W. Paul , Davis Frank M. , Buckley Paul M.
Published: July 2010

Southwestern corn borer, Diatraea grandiosella Dyar, is an important pest of corn, Zea mays L., in the southern USA and Mexico. Germplasm with resistance to attack by southwestern corn borer in the vegetative stages has been released; however, resistance to attack after anthesis has not yet been identified. The objectives of this investigation were to evaluate a diallel cross among a group of inbred lines, some of which appeared to exhibit resistance in laboratory and preliminary field tests, and to evaluate the effectiveness of visual ratings of leaf sheath and husk damage in identifying resistant hybrids. The nine‐parent diallel cross was grown for 2 yr and plants were infested with southwestern corn borer larvae 7 d after anthesis. Leaf sheaths and husks were visually rated and larvae recovered, counted, and weighed 14 d after infestation. Husks were also collected from an additional planting of the diallel cross within 3 d after silk emergence, lyophilized, and used in preparation of laboratory diets. Larvae were fed on the diets for 21 d and then weighed. Leaf sheath and husk ratings were not significant among hybrids; however, differences in number of larvae, mean larval weight, and total weight of larvae collected from a plant in the field test and mean larval weight in the laboratory among hybrids were significant. General combining ability (GCA) was a significant source of variation among hybrids for all traits. Estimates of general combining ability effects indicated that the parental inbreds, Mp305 and SC213, contributed to resistance of their hybrids.
Comparison of Determinate and Indeterminate Soybean Near‐Isolines and Their Response to Row Spacing and Planting Date
Authors: Robinson Stephen L. , Wilcox James R.
Published: July 2010

Determinate (DET) and indeterminate (IND) soybeans [Glycine max (L.) Merr.] differ in growth habit and have responded differently to planting date and row spacing. The purpose of this study was to compare DET and IND near‐isolines for phenoiogical and agronomic traits and to determine similarity of response of the isolines to planting date and row width. Thirty‐eight F5‐derived DET and IND near‐isolines were randomly selected from six soybean populations. The lines were evaluated in three replications of a split (planting date), split (row spacing), split (isoline) plot design over a 2‐yr period. Data were recorded on the days to first flowering, days to maturity, length of the reproductive period, and on plant height, lodging, and seed yield. Lines within growth habits responded similarly to row spacing, but the interactions of planting dates with lines within growth habits were significant for all traits measured. The DET lines were very similar to their IND isoline counterparts for phenological traits measured at two planting dates (r = 0.84** and 0.90**), less similar for plant height (r = 0.71**), and even less similar for plant lodging (r = 0.53** and 0.64**). There was no association between DET and IND isolines for seed yield at the early planting date and a weak association at the late planting date. This suggests that the two plant types responded differently to environmental factors that affect seed yield. However, the highest yielding DET and IND isolines averaged over both years, planting dates, and row spacings were derived from the same F5 plant, providing evidence that loci affecting superior seed yield could be expressed in either plant type.
Postanthesis Dry Matter Accumulation and Redistribution in Spring Wheat Mulched with Plastic Film
Authors: Niu J. Y. , Gan Y. T. , Zhang J. W. , Yang Q. F.
Published: July 2010

Spring wheat (Triticum aestivum L.) grown in semiarid climates shows a remarkable increase in grain yield when mulched with plastic film. Information on dry matter (DM) accumulation and redistribution in mulched plants is needed to understand the mechanisms of the yield improvement. A 2‐yr field study was conducted to determine DM of various vegetative (leaves, stems) and nongrain (rachises, glumes, lemma and palea, and sterile florets) organs and final grain yield for spring wheat grown on a Yellow Mein sandy loam (Aridic Haplustoll) with and without plastic mulches. Dry matter of vegetative and nongrain organs in both treatments reached a maximum 3 wk after anthesis and then decreased rapidly. Grain DM increased from 190 mg plant −1 at anthesis to an average of 2115 mg plant−1 in mulched wheat and 1726 mg plant−1 in unmulched wheat, by the fifth week after anthesis. The second internode from the spike contributed the greatest proportion (22‐25%) to the total DM lost from the vegetative and nongrain organs, followed by the flag leaf (21‐23%), the peduncle (11‐15%), and the leaves below the flag leaf (8‐10%). Basal leaves and stem segments, and nongrain organs contributed only 5 to 7% of the total DM mobilized. Compared with unmulched plants, the mulched plants accumulated greater (26%) DM at anthesis, mobilized a larger percentage of DM to grains after anthesis, and produced 36% more grain yield. Application of plastic mulches to spring wheat effectively increased dry matter production and mobilization from vegetative organs to grains.
Genetic Variation and Selection for Shoot and Rhizome Growth Traits in a Naturalized Quackgrass Population
Authors: Casler M. D. , Greub L. J. , Carlson S. K. , Collins M.
Published: July 2010

Quackgrass [Elytrigia repens (L.) Nevski; Agropyron repens (L.) Beanv.; Elymus repens (L.) Gould] is a perennial grass that has colonized much of the world's temperate cropland. Its persistence, perenniality, high nutritional value, and tolerance to several stress factors make it a potentially useful forage crop. This research was undertaken to assess the breeding improvement potential of quackgrass for direct use as a forage crop. Thirty‐five quackgrass parent clones were grown in a series of four greenhouse experiments (growth periods) between November 1981 and March 1984, and in a field experiment from July 1984 to June 1985. A random sample of their polycross progeny was grown in a field experiment from September 1982 to June 1984. Parent means, family means, and progeny means within families varied (P < 0.01) for all traits determined. Greenhouse traits had moderate repeatability (0.50–0.72), high clone × growth period interaction, and low correlation coefficients with field traits (r = −0.50–0.32). Thus, selection should be conducted in the field. There were large amounts of additive genetic variation for all three field traits (forage yield, plant diameter, and maturity). Realized gains from one cycle of selection were between expected gains for disomic and tetrasomic inheritance models. Late maturity was associated with low plant diameter during selection. Forage yield responded to selection, but appeared to be governed primarily by inbreeding because of small effective population sizes. Quackgrass plants that thrive in pastures and croplands still contain hidden alleles for low‐rhizome‐spreading phenotypes.
Low Cell‐Wall Extensibility Can Limit Maximum Leaf Growth Rates in Rice
Authors: Lu Zhongjin , Neumann Peter M.
Published: July 2010

The aim of this research was to clarify physiological mechanisms underlying slower leaf growth rates in rice(Oryza sativa L.) as compared with maize (Zea mays L.) and barley (Hordeum vulgare L). Seedlings were grown under controlled‐environment conditions with adequate supplies of water and mineral nutrients. The growth rates of emerging first leaves in both paddy and upland rice were low by comparison with maize and barley genotypes. The possibility that differences in mature cell size, comparative cell production rates, osmotic potentials, or extensibility characteristics of growing cell walls were involved in regulating these species differences were investigated. The lower growth rate of the rice leaves was not associated with comparatively lower rates of epidermal cell production but was associated with the production of smaller mature cells. The smaller size of the rice leaf cells was not associated with less negative osmotic potentials in the cell‐expansion zone. However, the comparative extensibilities of the growing leaf tissues and cell walls decreased in the order barley > maize > rice and gave good linear correlations with leaf relative‐growth rates (r = 0.87** and 0.97**, respectively). The data suggest that exceptionally low cell‐wall extensibility is involved in limiting maximum leaf growth rates in rice. Future introduction of increased wall extensibility in paddy rice might lead to increases in leaf growth potential and conceivably to improved yields.
Field Performance of Cell Suspension‐Derived Tall Fescue Regenerants and Their Half‐sib Families
Authors: Stadelmann F. J. , Kölliker R. , Boller B. , Spangenberg G. , Nösberger J.
Published: July 2010

The application of biotechnology to forage grass has the potential to complement and speed up conventional breeding. To ascertain the suitability of regenerants for improvement programs, primary regenerants of tall fescue (Festuca arundinacea Schreb.) cv Tacuabé and their progenies were investigated in a field experiment located in Eschikon near Zürich (Switzerland). Thereby, the following two aspects were focused on. First, do regenerated plants and their progenies perform similar to seed‐grown plants; and second, do different regeneration systems have an effect on the performance of the regenerants? Two sets of plants, regenerated from different single‐genotype derived embryogenic suspension cultures (ESC) of tall fescue, were evaluated for agronomic traits in a replicated field experiment for three growing seasons. Embryogenic suspension cultures were either routinely subcultured or cryopreserved and re‐established. Seed from the primary regenerated and seed‐grown plants were harvested to evaluate morphological and phenological traits of corresponding halfsib progenies in a further field experiment. When compared with seed‐grown plants of the same cultivar, primary regenerants showed reduced vegetative growth and fertility. The performance of plants regenerated from cryopreserved‐reestablished ESC was not inferior to corresponding plants regenerated from routinely subcultured ESC. The performance of progenies of regenerated plants did not differ from those of seed‐grown plants and was within the range of the cultivar. There was no effect of the regeneration system on the performance of corresponding progenies; thus, suggesting that the weak growth of the primary regenerants was most likely of epigenetic origin. Therefore regenerated plants can be integrated into breeding programs without major restrictions.
Relational Database System for Summarization and Interpretation of Hard Winter Wheat Regional Quality Data
Authors: Haley Scott D. , May Rod D. , Seabourn Bradford W. , Chung Okkyung K.
Published: July 2010

Achieving acceptable end‐use (milling and baking) quality is a fundamental objective of wheat (Triticum aestivum L.) breeding programs throughout the U.S. hard winter wheat region. Numerous analytical methods have been developed to measure quality. Few tools are available to assist in the decision‐making process when faced with a large number of parameters from comprehensive milling and baking tests. Our objective was to develop a relational database system for summarization and interpretation of wheat end‐use quality data from the USDA‐ARS Hard Winter Wheat Quality Laboratory. The database system uses a graphical interface with a series of “layouts” that require input from the user, guide the user to a successive layout, or provide a data report. The database system provides simultaneous assessment of multiple quality traits on a standardized scale, userspecified prioritization of end‐use quality traits for numerical and qualitative ratings of genotypes, tabulation of major quality deficiencies of genotypes, and summarization of quality ratings for a genotype across multiple nurseries. The database system has specific application to the hard winter wheat regional testing program; however, the basic principle and design could be readily extended to nursery‐based enduse quality testing programs in other wheat regions and market classes.
Seedling Growth Comparison of Arrowleaf, Crimson, Rose, and Subterranean Clovers
Authors: Evers G. W.
Published: July 2010

Cool‐season annual clovers are a critical component of profitable pasture systems in the southeastern USA; however, there are little data comparing seedling development of major species. Arrowleaf (Trifolium vesiculosum Savi.), crimson (T. incarnatum L.), rose (T. hirtum All.), and subterranean (subclover) (T. subterraneum L.) clovers were planted in September for 3 yr in northeast Texas. Clovers were sampled biweekly during October and November, and plant density, leaves per seedling, leaf area index (LA1), shoot weight, nodules per seedling, root weight, root length, and root/shoot ratio were determined. Rainfall amounts and distribution caused differences among years (P < 0.05) for plant density, leaves and nodules per seedling, LAI, and root/shoot ratio. Averaged across years, crimson clover had the greatest number of leaves and nodules per seedling, and the greatest shoot weight, root weight, root length, and LAL. Subterranean clover was intermediate, and arrowleaf and rose clovers had the lowest values. Sampling date did not affect plant density and root/shoot ratio, but the other seedling parameters increased with succeeding sampling dates. The greater seedling vigor of crimson clover is due in part to its larger and faster‐expanding LAI and tolerance of cooler temperatures. Subterranean clover was the largest seeded species but is not as well adapted to cooler winter temperatures as the other species. The slower seedling vigor of arrowleaf clover was due to its smaller seed size. Poor nodulation may be responsible for the slow seedling growth of rose clover. Good seedling vigor of cool‐season annual clovers was primarily dependent on large seed size, rapid leaf area expansion, and early nodulation
Growth and Photosynthetic Responses of Groundnut Genotypes to High Temperature
Authors: Talwar H. S. , Takeda H. , Yashima S. , Senboku T.
Published: July 2010

Among abiotic factors, high temperature is one of the major constraints to adaptation of groundnut (Arachis hypogaea L.) in tropical and subtropical areas. The aims of this study were (i) to evaluate three genotypes (ICG 1236, ICGS 44, and Chico) of groundnut for their heat acclimation potential (HAP), and (ii) to examine whether the growth, yield, and photosynthetic responses of these genotypes to temperature related to the HAP. We defined HAP as the change in leaf heat tolerance based on plasmalemma thermostability at 40 to 60°C measured by electrolyte leakage after acclimation at 35/30°C day/night temperature. Initially, plants were raised in a glasshouse maintained at 25/25°C day/night temperature. One half of the plants were shifted to another glasshouse maintained at 35/30°C after the appearance of the third leaf. Heat killing time (HKT), defined as the time required to cause 50% relative injury, indicated that the three genotypes acclimated to high temperature stress, with significant variations in HAP. All genotypes maintained greater vegetative growth and higher photosynthetic rates when grown under the higher temperature regime and genetic differences in photosynthetic rate were related to HKT. The higher temperature regime affected the reproductive growth adversely by increasing flower abortion and decreasing seed size, however. Differences in chlorophyll fluorescence and membrane thermostability between growth temperature were found only after incubating the leaf tissue at temperatures of 50°C or higher. Genetic differences in HAP were small and unrelated to growth differences.
Genetic Modification of Cotton Fiber Properties as Measured by Single‐ and High‐Volume Instruments
Authors: May O. Lloyd , Jividen Gay M.
Published: July 2010

Improved cotton fiber properties for the textile industry depends largely on genetic progress. Progress towards better fiber quality could be enhanced if breeders knew whether choice of fiber property measurement instrument affects direct and correlated responses to selection. The objectives of our study were to (i) compare heritability of a fiber property measured by single‐instrument (fibrograph, micronaire, stelometer), that measure one or a few related properties, with the same fiber property measured by the integrated high volume instrument (HVI), capable of measuring multiple fiber properties, and (ii) compare direct and correlated selection response of fiber strength measured by the stelometer single instrument with that measured by the HVI. Other fiber properties important to textile processing including neps, short fiber content, immature fiber content, and fineness were measured by the Advanced Fiber Information System (AFIS). Heritability and selection response were estimated in two populations derived from mating the excellent fiber quality germplasm lines PD‐3‐14 and PD 5363 with the lesser fiber quality germplasm LA 870222. Heritability of micronaire reading (by micronaire instrument) and length (2.5% span length by fibrograph measurement) by single‐instrument was similar to that measured by HVI. Heritability of fiber strength was greater when measured with stelometer than HVI, but the subpopulations with highest fiber strength by stelometer or HVI measurement differed little for fiber strength when evaluated with either instrument. Heritability of short fiber content averaged about 0.2, fiber fineness about 0.5, and immature fiber content about 0.6, indicating the potential for genetic progress. Overall, early generation selection for fiber strength by HVI measurement resulted in desirable fiber profiles.
Annual and Biennial Flowering Habit of Kentucky Bluegrass Tillers
Authors: Sylvester Anne W. , Reynolds James O.
Published: July 2010

A stand of Kentucky bluegrass (Poa pratensis L.) consists of a collection of leafy tillers at various stages of development. Tiller morphology over 2 yr of growth was studied by sampling 3‐yr‐old dryland fields to determine tiller ages and to test whether burned and nonburned fields show different proportions of tiller types. Three classes of tillers were identified and named (i) small newly emerging nonleafy D tillers, (ii) leafy F tillers that grow directly from D tillers, and (6) leafy C tillers that have persisted for at least a year before flowering. On the basis of measurable floral features, C tillers are larger, more robust, can be induced sooner in the fall, and produce panicles of greater production potential than F tillers. Our results show that bluegrass tillers can be annual or biennial in flowering habit. Dense populations in burned fields produce higher proportions of D tillers in mid‐fall than non‐burned fields, but similar proportions of C and F tillers throughout the growing season. Fall regrowth may thus influence stand composition over a 2‐yr growth cycle. Assessment of tiller density should be a useful tool for grass seed growers when they are designing new management strategies, since annual F and biennial C tillers are found in all of the cultivars examined. Given pressures to avoid open‐field burning, alternative methods can be tested by determining changing proportions of C to F tillers. Manipulation of the balance between annual and biennial tillers may contribute to improving yield in the absence of open‐field burning.
Near Infrared Reflectance Spectroscopy Prediction and Heritability of Neutral Detergent‐Soluble Fiber in Alfalfa
Authors: Fonseca C.E.L. , Hansen J.L. , Thomas E.M. , Pell A.N. , Viands D.R.
Published: July 2010

Increasing neutral detergent‐soluble fiber (NDSF) concentration has been considered a strategy for breeding alfalfa (Medicago sativa L.) with improved quality. Pectin is the main component of NDSF and is highly digestible, but the assay for NDSF is time‐consuming. The objectives were (i) to determine the potential use of near infrared reflectance spectroscopy (NIRS) to predict NDSF concentration in alfalfa and (ii) to estimate NDSF heritability and gain from selection. Herbage was sampled five times across 2 yr from two populations of half‐sib (HS) progeny tested at Ithaca, NY. Calibration equations were developed by multiple linear regression of laboratory values of NDSF on NIRS spectra. Samples from one harvest were assayed twice to compare extraction methods. Means of NDSF from 90‐ and 80%‐ethanol extractions were 213.1 ± 7.21 and 179.5 ± 5.89 g kg−1, respectively. Assay standard deviations were low for both ethanol concentrations. Because a better calibration equation was obtained with the 80%‐ethanol assay, all remaining samples were assayed by that technique. Standard errors of calibration were small, ranging from 4.71 to 7.54 g kg−1. Coefficients of multiple determination (R2) ranged from 0.72 to 0.97. Most heritability estimates for NDSF were significantly greater than zero, ranging from −0.03 ± 0.20 to 0.56 ± 0.17 and averaging 0.41. Expected gain from selection of parents based on HS progeny ranged from 4.6 to 19.0 g kg−1 and averaged 10.3 g kg−1. Selecting parents with higher NDSF concentrations predicted by NIRS evaluations of HS progenies may improve forage quality of alfalfa.
Maize Morphology and Shoot CO2 Assimilation after Root Damage by Western Corn Rootworm Larvae
Authors: Riedell Walter E. , Reese R.Neil
Published: July 2010

Knowledge of the physiological stress mechanisms triggered by corn rootworm larval feeding damage may suggest new ways of maintaining maize (Zea mays L.) productivity in plants damaged by this important insect pest. Western corn rootworm [Diabrotica virgifera virgifera (LeConte)] larval feeding damage to maize root systems causes complex changes in leaf CO2 assimilation. The objective of our study was to further explore the relationships between plant morphology and CO2 assimilation in rootworm‐damaged maize. The effects of moderate or severe root damage caused by larval feeding or by mechanical damage on root system morphology, shoot dry weight, leaf area, stomatal conductance, and CO2 assimilation were investigated in greenhouse experiments. Rootworm larval feeding, which removed about 75% of the total root system volume, or mechanical cutting treatments imposed at the V12 leaf stage, which removed about 30% of the total root system volume, had no effect upon leaf CO2 assimilation but significantly reduced stomatal conductance when measured at the tassel development stage. During the time when larvae were damaging root systems or when specific root node axes were mechanically cut, however, leaf CO2 assimilation was less in root‐damaged plants than in undamaged plants. Larval‐damaged root systems had accelerated adventitious root axis growth and development in the nodes located immediately above the damaged nodes. This compensatory root growth was more pronounced under the moderate root feeding damage treatments than in the severe root damage treatments. Total leaf area and shoot CO2 assimilation were less in plants with severe larval feeding damage than in plants with moderate damage or in control plants. Thus, the severity of root damage plus the level of root compensatory growth play important roles in mediating shoot growth and CO2 assimilation responses to stress imposed by rootworm larval feeding.
Structural Responses to Selection for Reduced Fiber Concentration in Smooth Bromegrass
Authors: Casler M.D.
Published: July 2010

Selection for reduced neutral detergent fiber (NDF) concentration has been practiced as a mechanism of increasing voluntary intake potential of forage crops. Because selection is usually conducted on the basis of whole‐plant samples, there exists the potential for structural shifts in plant composition. The objective of this study was to quantify structural changes due to selection for reduced NDF concentration in smooth bromegrass (Bromus inermis Leyss). Three cycles of phenotypic selection led to reduced whole‐plant NDF concentration, primarily due to reductions in NDF of stems (−5.7 to −5.8 g kg−1 cycle−1) and leaf sheaths (−3.1 to −4.9 g kg−1 cycle−1). Selection at both the vegetative growth stage (primarily leaf blades) or heading growth stage (all shoot components present) led to similar changes in shoot‐component NDF concentrations. Selection on the basis of vegetative samples did not lead to structural changes. Conversely, selection on the basis of headed samples led to an average reduction of −7.5 % cycle−1 in stem component concentration, which was compensated largely by increases in leaf blade and sheath component concentrations. Increases in leaf:stem ratio may partially explain reductions in forage yield associated with reduced NDF concentration. Future selection efforts should attempt to avoid this response by using samples composed of a single shoot component. The NDF concentrations in various shoot components of smooth bromegrass appear to be positively correlated with each other.
Post–Green Revolution Trends in Yield Potential of Temperate Maize in the North‐Central United States
Authors: Duvick D. N. , Cassman K. G.
Published: July 2010

This paper addresses the question of whether there has been an increase in yield potential of maize (Zea mays L.) hybrids released in the north‐central United States since the advent of the “Green Revolution” that began in the late 1960s. Because there are few published data about hybrid growth rates and yield‐determining plant traits when grown at yield potential levels, we attempt to address this issue indirectly by evaluation of maize breeding efforts, changes in plant traits of commercial hybrids, and by comparison of statewide average yield trends and yield trends in sanctioned yield contests. On the basis of these sources of information and a definition of yield potential as the yield that can be achieved with an adapted hybrid when grown without obvious stress of any kind, we found that there is conflicting evidence to support the hypothesis that maize yield potential has increased. We recommend experimental approaches to quantify and investigate the determinants of maize yield potential in the north‐central United States and for use in breeding hybrids with greater yield potential.
Influence of Nitrogen Availability on Seed Nitrogen Accumulation in Pea
Authors: Lhuillier‐Soundélé Annabelle , Munier‐Jolain Nathalie G. , Ney Bertrand
Published: July 2010

The final seed nitrogen concentration (the ratio of seed N and dry matter content) is highly variable in pea (Pisum sativum L.) and N remobilization during seed filling may limit yield by restricting the seed filling period. This study was conducted to determine how seed N accumulation is regulated in pea. The effect of N availability and distribution on individual seed N accumulation rate at different nodes was investigated in three genotypes grown in the field and glasshouse under various levels of N fertilizer, depodding, and defoliation. The N content of vegetative plants parts (stems, leaves, podwalls) and seeds from three mainstem nodes were regularly recorded. Plant N available to the seeds at a given time was assessed as the sum of the amount of N still available for remobilization in vegetative parts and the amount of N accumulated by the plant. The results indicate that the N available in a plant at a given time can be considered as one common pool accessible to all seeds and equitably divided among them. Thus, the rate of individual seed N accumulation was unaffected by intra‐plant position of seeds. This rate increased with the amount of N available per seed until a maximum rate of individual seed N accumulation (43 μg seed−1 degree‐day−1) was reached. The relationship established between the rate of individual seed N accumulation and the plant N available per seed will be useful to improve models simulating yield and final seed N concentration in legumes.
Regrowth of White Clover after Chilling: Assimilate Partitioning and Vegetative Storage Proteins
Authors: Corbel G. , Robin Ch. , Frankow‐Lindberg B. E. , Ourry A. , Guckert A.
Published: July 2010

Under temperate climates, grassland species are subjected to overwintering which may significantly influence their early spring growth capacity. In white clover (Trifolium repens L.), it is known that overwintering capacity can differ among cultivars. Ability of this forage legume to recover from winter damage will, therefore, have a great influence on its persistence in grass–clover associations. Experiments were undertaken with two different white clover cultivars (Huia and AberHerald). Leaf appearance rate, dry matter distribution, 14C assimilate partitioning, and vegetative storage protein accumulation were determined in plants subjected to a 4‐wk chilling period (5/0°C, day/night) and subsequent warmer temperatures (15/10°C), and compared with control plants (20/15°C). Chilling treatment decreased leaf appearance rate, with AberHerald producing more leaves than Huia. This can be considered as a major aspect of cold adaptation strategy because leaf appearance rate controlled carbon acquisition. Low temperature increased dry matter partitioning to below‐ground tissues. AberHerald allocated more assimilates to stolons than Huia. Accumulation of a 17.3‐kDa protein, believed to act as a vegetative storage protein, also increased after the chilling treatment. Regrowth was characterized by rapid mobilization of the 17.3‐kDa protein in stolons and by preferential carbon allocation to stolon apices. AberHerald showed a higher regrowth potential than Huia in view of its morphological and physiological characters which include carbon acquisition and assimilate partitioning patterns, favoring shoot regrowth and acquisition of stolon reserves.