bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyploid Stenotaphrum Germplasm: Resistance to the Polyploid Damaging Population Southern Chinch Bug
Authors: Busey Philip
Published: July 2010

‘Floratam’ St. Augustinegruss [Stenotaphrum secundatum (Walt.) Kuntze] has been widely used in lawns because of its resistance to the southern chinch bug (Blissus insularis Barber). The southern chinch bug adapted genetically to Floratam and seriously damaged this cultivar within 12 yr after release. The Floratam‐adapted southern chinch bug has been described as the polyploid damaging population (PDP), because polyploid germplasm had previously shown resistance. This study examined polyploid germplusm for resistance to the PDP southern chinch bug. Stenotaphrum clones were bioassayed by confining stolon cuttings with PDP southern chinch bugs from different regions. Resistant clones were detected based on reduced southern chinch bug longevity, oviposition rate, and excrement production, compared with Floratam. The most resistant clones were PI 365031, a pembagrass [S. dimidiatum (L.) Brongn.], and FX‐2, FX‐10, and FX‐33 (intercrusses of polyploid S. secundatum from Africa). They supported low PDP southern chinch bug oviposition (≤5 eggs female‐1 wk‐1 and ≤25 eggs lifetime‐1). Resistance of FX‐33 was verified against PDP southern chinch bugs (representing laboratory colonies and field recollections) in mated pairs and congregations, and against southern chinch bugs that had received different prior food sources. Both FX‐33 and FX‐10 typified the African polyploid St. Augustinegrass germplasm by having 2n = 30 chromosomes, bivalent pairing at metaphase I, good crossed seed set, and abundant laminar hairs.
Peanut Pod Development in Pegging and Rooting Zones Salinized with Sodium Chloride
Authors: Lauter D. J. , Meiri A.
Published: July 2010

Subterranean pods of ‘Shulamit’ peanut (Arachis hypogaea L.) absorb water and nutrients from the pegging zone. Therefore high concentrations of inorganic salts such as NaCI in the pegging zone may influence pod development. A greenhouse study was conducted to determine the levels of NaCI in the pegging and rooting zones that inhibit pod development and caused seed damage. Plants were grown in containers that had separate compartments for pegging media of sand and rooting media of solution culture. Different levels of NaCI were either present in the pegging zone, the rooting zone, or both zones. Application of 35 mM NaCI to only the pegging zone caused dark areas on the inner faces of the cotyledons of seed in mature pods but did not significantly affect the weight of the individual seed. Higher levels (70 and 105 mM NaCI) caused additional symptoms of seed damage prior to pod maturity and much lower seed weight, but did not affect pod area at the plane of dehiscence. Pod Na and CI had similar, linear relationships with pegging zone NaCI. Pod Ca was correlated negatively with pegging zone NaCI. Application of NaCI to both zones inhibited pod growth and promoted vegetative growth (in comparison to plants that only received NaCI in the rooting zone). Concentrations less than 40 mM NaCl in the rooting zone caused lower weights of individual pods and seed. Also plants with less than 40 mM NaCI in the rooting zone produced less vegetative weight and an increased percentage of small, immature pods was observed. Rooting zone NaCI did not result in symptoms of seed damage, as did pegging zone NaCl.
Reproductive Characteristics of Winter Wheat Cultivars Subjected to Postanthesis Shading
Authors: Grabau L. J. , Van Sanford D. A. , Meng Q. W.
Published: July 2010

High temperatures during reproductive development of soft red winter wheat [Triticum aestivum (L.) em Thell] reduce the length of the available grain filling period and may make cultivars grown in such environments more sensitive to short‐term reductions in light intensity. Therefore, short‐duration, postanthesis shading (63%) was applied to the cultivars Caldwell, Hart, and Wheeler (about 30, 38, and 45 mg kernel−1, respectively) to assess the impact of light intensity on kernel growth rate [(KGR) mg kernel−1 d−1 and other reproductive characteristics. Early shading [(ES) 1‐6 or 1‐8 after anthesis (DAA)] or midshading [(MS) 14‐21 or 15‐22 DAAI were used with Hart in 1986 to 1988 and the other cultivars in 1987 to 1988. Cultivars differed in relative response to shading with KGR of 1.55, 1.42, and 1.31 (Caldwell); 1.78, 1.75, and 1.59 (Hart); and 2.00, 1.89, and 1.79 (Wheeler) for control, ES, and MS, respectively. Yield reductions due to ES (8.6%) were related to depressed floret fertility (all coltivars) and kernels spike−1 (Hart only), while those due to MS (5.6%) resulted from lower KGR and kernel weight. Data from MS may support the conclusion that wheat yields are sourcelimited in some postanthesis environments, in contrast to a number of previous reports. A shortened reproductive period may be responsible for this observation.
Taproot Restriction Effects on Growth, Earliness, and Dry Weight Partitioning of Cotton
Authors: Ben‐Porath A. , Baker D. N.
Published: July 2010

Cotton (Gossypium hirsutum L.) is an indeterminate, woody perennial, whose primary axis remains vegetative throughout the life of the plant. During the boll‐filling period, the growing mainstem and taproot compete with reproductive organs for limited supplies of assimilates. In a series of experiments, the effects of taproot restrictions on growth and development of drip irrigated cotton plants were explored. Cotton (‘Stoneville 825’) plants were grown outdoors and in sunlit growth chambers. Taproots were restricted to various degrees by using different pot sizes (I, 2.5, 7, 12, and 18 L) during the years 1982 to 1983. The pots were arranged in a row crop configuration (10 plants m−1 of row, 1m between rows). Dry matter distribution was measured destructively. The restriction of the taproot apical dominance by small pots (I or 2.5 L) accelerated the formation of secondary and tertiary roots compared to roots in larger pots (7 L or more). Taproot‐restricted plants started to flower earlier and they flowered faster. Their heavier load of developing bolls caused a greater slowing of vegetative growth of the main axis. As a result, taproot‐restricted plants were more compact due to shorter internodes on fruiting branches and at the top of the plant. Taprootrestricted plants were earlier and higher yielding in short seasons because of better partitioning of assimilates into fruit rather than into storage organs.
Green‐Manure Legume Effects on Soil Nitrogen, Grain Yield, and Nitrogen Nutrition of Wheat
Authors: Badaruddin M. , Meyer D. W.
Published: July 2010

Knowledge of legume N production and legumeffects on subsequent crop yield and quality is necessary to encourage legume use instead of the traditional fallow on set‐aside land. Objectives of these studies were to: (i) compare seeding‐year herbage and N yields five forage legume species, (ii) determine soil NO3‐N status in the spring following green‐manure legume crops, and (iii) evaluate effects of green‐manure legumes on grain yield, grain yield components, and N nutrition of the subsequent wheat (Triticum aestivum L.) crop when fertilized with 0, 75, and 150 kg N ha−1. Field experiments were conducted on a Fargo silty clay (fine, montmorilloritic, frigid Vertic Haplaquoll) at Fargo and on a Perella‐Bearden silty clay loam (fine‐silty, mixed, frigid Typic Haplaquoll, fine‐silty, frigid Aeric Caiciaquoll) near Prosper, ND, during 1984 to 1986. All legume species had equal herbage and N yields across the four environments and were greater than the wheat‐straw check. Accumulated legume herbage and fall regrowth were incorporated into the soil in late fall. Spring soil NO3‐N following Terra Verde alfalfa (Medicago sativa L.) and hairy vetch (Vicia villosa Roth.) was equal to the fallow check and greater than the soil NO3‐N following the wheat check or other legume species. Grain yield, grain N, and N uptake of unfertilized wheat following the legume treatments generally were similar to those following fallow and wheat fertilized with 150 kg N ha−1. Increases in all grain yield components following legumes contributed to this yield advantage. Efficiency and utilization of N generally were greater following a green‐manure crop than following either fallow or wheat checks. This study suggests that green‐manure legumes should be considered as an alternative to fallow on set‐aside land in higher moisture areas.
Backcross‐Derived Progeny from Soybean and Glycine tomentella Hayata Intersubgeneric Hybrids
Authors: Singh R. J. , Kollipara K. P. , Hymowitz T.
Published: July 2010

Wild perennial species of the subgenus Glycine Willd, have not been exploited in soybean [Glycine max (L.) Merr.] breeding programs. This paper discusses wide hybridization in the genus Glycine and reports on the origin, identification, and breeding behavior of a synthesized amphiploid soybean ✕ G. tomentella Hayata hybrid and its backcross‐derived progeny. Amphiploid H213‐2a (2n = 118) plants showed almost normal meiotic pairing (0.711 + 57.9811 + 0.33IV), but later meiotic stages were abnormal, showing laggards and bridges, and the plants set only a few pods. The F2, F3, and F4 plants carried the expected 2n = 118 chromosomes, and thus were cytologically stable. A growth‐hormone solution containing 100 mg gibberellic acid (GA3), 25 mg naphthalene acetic acid (NAA) and 5 mg kinetin/L distilled water was sprayed onto the pollinated gynoecia to enhance pod retention (14.19%) in H213‐2a ✕ soybean crosses. Without daily hormone spray, only three pods of the 3417 florets pollinated were harvested 19 to 21 d after pollination. The BC1 plants were obtained in two cross combinations: (i) H213‐2a ✕ ‘Clark 63’ = H562, and (ii) H213‐2a ✕ ‘Essex’ = H564. The H562 plants contained 2n = 76, (BC1; expected 2n = 79), suggesting the loss of three chromosomes. The H564 plants contained 2n = 98 chromosomes and may have originated by the union of a female gamete (n = 59) and an unreduced male (n = 40) spore. All the BC1 plants were totally sterile, and attempts are being made to generate BC2 plants.
Wheat High Temperature Tolerance During Reproductive Growth. II. Genetic Analysis of Chlorophyll Fluorescence
Authors: Moffatt J. M. , Sears R. G. , Cox T. S. , Paulsen G. M.
Published: July 2010

Improvement of crop tolerance to high temperature is hindered by the lack of information on genetic control of the trait. Objectives of this research were to characterize inheritance of high temperature tolerance based on chlorophyll fluorescence measurements and to estimate combining ability effects in wheat (Triticum aestivum L.). A diallel cross, including reciprocals, of six wheat genotypes was analyzed for high temperature tolerance based on chlorophyll fluorescence. Vernalized F1 plants and parents were initially placed in controlled environment chambers at 25/20 °C day/night temperatures. One‐half of the plants were exposed to a high temperature stress of 40 °C (16‐h day)/27 °C (8‐h night) 10 d after the earliest genotypes flowered. Initial (Foe), variable (Fv), and maximum chlorophyll fluorescence (Fm) were measured on dark‐adapted flag leaves of plants 3 and 7 d after initiation of stress. Analysis revealed significant general combining ability effects and maternal effects. Significant specific reciprocal effects indicated cytoplasmic and nuclear interactions in the response to high temperature. The combination of positive specific reciprocal effects and high general combining ability effect for the female parent conferred a high level of stability for Fv in the stress environment. Recurrent selection may be an appropriate method of accumulating genes that favor high temperature tolerance based on chlorophyll fluorescence measurements in wheat.
Vital Staining of Root Hairs in 12 Warm‐Season Perennial Grasses
Authors: Oprisko Marianne J. , Green Robert L. , Beard James B. , Gates Charles E.
Published: July 2010

Root hairs have been shown to absorb water and nutrients; thus, it may be important to characterize their quantity, size, and viability when studying components of drought resistance. The first objective was to find the most effective and precise vital stain for root hairs of warm‐season perennial grasses. Sprigs of 12 genotypes representing six species were grown in sand culture in the greenhouse. Vital stain effectiveness in 0.05 M PO4 buffer (pH 7.0) was established by the percentage of genotypes in which vitality could be determined using the live/dead color difference. The five vital stains, with their percentage effectiveness over the 12 genotypes and their average absolute color difference values (none = 1, greatest = 4), were: 0.5 g/L Evan's blue, 100%, 3.3; 0.1 g/L methylene blue, 67%, 1.9; 1 g/L Congo red, 58%, 1.8; 0.1 g/L phenosafranin, 50%, 1.7; and 0.1 g/L neutral red, 25%, 1.4. Evan's blue was the best stain, in terms of greatest precision and least variability.
Relationship between Seed Vigor Tests and Field Performance of ‘Regar’ Meadow Bromegrass
Authors: Hall R. D. , Wiesner L. E.
Published: July 2010

The standard seed germination test often overestimates actual field emergence. Several physiological and biochemical tests have been developed for evaluating seed vigor in various crops, but the relationship between vigor testing and field performance has not been studied extensively in grasses. The objective of this study was to evaluate several laboratory vigor tests to determine their relationship to field performance of ‘Regar’ meadow bromegrass (Bromus biebersteinii Roem & Schult.). Standard germination and accelerated aging tests were used to evaluate four seed lots during the 1985 studies. Field performance of these lots was evaluated by determining speed of emergence, total emergence, and forage yield. Only total emergence was correlated with standard germination, while both total emergence and forage yield were correlated significantly with accelerated aging. In 1986, standard germination, seedling growth rate, accelerated aging, electrical conductivity, respiration rate, and adenosine triphosphate (ATP) content were used to evaluate 10 seed lots that were field performance tested. Accelerated aging, respiration rate, and ATP content were correlated significantly with forage yield. Multiple stepwise regression selected accelerated aging and respiration rate as the best model for predicting first‐year forage yield. Field performance of Regar meadow bromegrass can be determined using accelerated‐aging test and seed respiration.
Potential of Field Corn Germplasm for the Improvement of Sweet Corn
Authors: Tracy W. F.
Published: July 2010

In corn (Zea mays L.), sweet corn has not benefited from yield gains due to genetic improvement as field corn has. Possible reasons include the narrowness of the genetic base of sweet corn, the lack of defined heterotic groups, and the greater effort devoted to improving yield in field corn. The objectives of this study were to measure the combining ability of certain field and sweet inbreds, the potential contributions of field corn to sweet corn, and whether or not heterotic groups exist within sweet corn as in field corn. Seven adapted sweet inbreds of different genetic backgrounds were crossed with four Corn Belt Dent inbreds and were included in a diallel sweet corn series. Three of the inbreds were from the stiff stalk synthetic group; one was a Lancaster type. The experiment was grown in two years at Arlington, WI. Data were collected on ear weight, yield, number of usable ears, number of ear shoots, plant and ear height, tillers, ear diameter and length, maturity, ear shape, tipfill, and row configuration. The field‐sweet hybrids resulted in high general combining ability effects for both field and sweet parents for all traits. The field‐sweet hybrids had higher yields, more ears, taller plants, fewer tillers, longer ears, and better ear tipfill, shape, and row configuration than the diallel series of sweet hybrids. Specific combining ability was not important in the field‐sweet hybrids. Although field corn inbreds offer a potential source of desirable genes for sweet corn improvement, no specificity of sweet inbreds for field corn heterotic groups was found. for the sweet hybrids in the diallel series, highly significant general and specific combining ability effects were observed for most traits, although, as for the field‐sweet hybrids, no clear combining ability groups emerged based on ancestry.
Chromosomal Location of Genes for Grain Protein Content of Wild Tetraploid Wheat
Authors: Joppa L. R. , Cantrell R. G.
Published: July 2010

The improvement of grain‐protein content is an important goal of durum wheat (Triticum turgidum L.) and other wheat breeding programs. The objective of this study was to determine the chromosomal location of genes for high grain‐protein content in an accession of wild tetraploid (emmer) wheat (T. turgidum L. var. dicoccoides) having seeds with high grain‐protein content. The method was to substitute each of the dicoccoides (DIC) chromosomes into ‘Langdon’ (LDN) durum by crossing and backcrossing with a set of LDN D‐genome disomic substitution lines. All of the Langdon‐dicoccoides, LDN(DIC), substitution lines were vigorous and fertile except the LDN(DIC‐2B), lines, which were low in vigor and partially sterile. The substitution lines for each of the other 13 chromosomes, the 1D(1A), 4D(4B), and 7D(7A) D‐genome disomic substitutions, and the cultivars LDN, Ward, Monroe, and Vie were grown in field experiments with four replicates at two locations in each of two years and were evaluated for grain‐protein content. The following lines had significantly higher grain‐protein content than LDN: LDN(DIC‐6B) > LDN(DIC‐2A) > LDN(DIC‐SB) = LDN(DIC‐3A) = LDN(DIC‐6A). Lines with significantly less grain protein than the recurrent parent LDN were LDN(DIC‐3B), LDN(DIC‐4B), and LDN(DIC‐7B). The high grain‐protein content of the LDN(DIC‐2A) lines may have been related to their low grain yield. The consistently high grain‐protein content of the LDN(DIC‐6B) lines suggests that this DIC chromosome has one or more important genes affecting this character. These LDN(DIC) substitution lines should prove useful in breeding improved durum wheat cultivars with increased grain‐protein content.
Haploid Oat Plants Produced by Application of Maize Pollen to Emasculated Oat Florets
Authors: Rines H. W. , Dahleen L. S.
Published: July 2010

Only six haploids in oat (Avena sativa L.) have been previously reported, five of spontaneous origin and one from anther culture. Our objective was to develop more efficient methods for producing oat haploids to use in selecting mutants, recovering aneuploids, and producing doubled‐haploid lines for genetic and breedings tudies. In a series of experiments, pollen from maize (Zea mays L.) was applied to previously emasculated oat florets. Twelve to 15 d later excised ovaries/caryopses, or embryos taken from them, were placed onto an amino acid‐supplemented Murashige and Skoog medium containing 7% sucrose for embryo rescue. Recovered plantlets were potted in soil and grown to maturity. Root tips and meiotic tissues were sampled for cytological analyses. Overall, 14 haploid oat plants were recovered by embryo rescue following application of maize pollen to approximately 3300 emasculated oat florets. Root tip cells in each of the recovered plants had the oat haploid chromosome number of 21. Presumably these oat haploids originated from interspecies hybrid zygote formation followed by elimination of maize chromosomes during initial cell divisions, as has been described in haploid wheat (Triticum aestivum L.) formation in wheat ✕ maize hybridizations. In the initial experiment, which involved combinations of various oat and maize genotypes, each of the four oat haploids recovered was from a different oat cultivar and each involved a different source of maize pollen; thus, indicating that the process is not genotype unique. Meiotic cells of the recovered haploid plants were characterized by aberrant chromosome behavior and numerous micronuclei, as expected in a haploid. Occasional seed were set on haploid plants and both euploid (2n) and aneuploid (2n‐1 and 2n‐2) progeny were obtained. The use of maize pollinations provides a new approach for obtaining haploid oat plants for genetic and breeding studies.
Photosynthesis and Productivity during High‐Temperature Stress of Wheat Genotypes from Major World Regions
Authors: Al‐Khatib Kassim , Paulsen Gary M.
Published: July 2010

Photosynthetic rates and thylakoid activities are adversely affected by high temperatures in wheat (Triticum aestivum L.), but their role in determining productivity during stress is uncertain. Our objectives were to ascertain relationships and genotypic variability among single‐leaf photosynthesis, thylakoid activity, and productivity during high‐temperature stress at vegetative and reproductive stages. Ten genotypes from major world wheat‐producing regions were grown under moderate (22/17 °C day/night) and high (32/ 27 °C day/night) temperatures for 2 wk as seedlings or from anthesis to maturity. Net photosynthesis, chlorophyll variable fluorescence (Fv), and productivity were measured at both stages. High temperature decreased mean photosynthetic rates 32 and 11%, mean Fv 42 and 11%, and mean total biomass 32 and 15% in seedling and maturing plants, respectively. The regime also reduced mean kernel weight 20% and mean grain yield 23% relative to the moderate temperature. Decreased photosynthetic rates and diminished productivity of plants were highly significantly correlated at both growth stages. Relative grain yields were strongly influenced by decreased duration of photosynthetic activity, which ranged widely in the 10 genotypes. Thylakoid membranes from seedlings of the 10 genotypes were heated at 20 to 35 °C, and uncoupled electron transport and Fv were determined. Thylakoid stability to heating varied similarly to whole‐plant responses to high temperature by seedlings, but not by maturing plants. Genotypes that were most tolerant of high temperature had stable rates and/or long durations of photosynthetic activity, high kernel weights, and high harvest indices, which are potential selection criteria.
Resistance to Whitebacked Planthopper in Elite Lines of Cultivated ✕ Wild Rice Crosses
Authors: Ye Z. H. , Saxena R. C.
Published: July 2010

Wide hybridization is an important breeding tool for incorporating alien genetic variation and transfer of useful traits from wild species of Oryza to commercial rice (‘O. sativa’ L.) cultivars. Wevaluated two elite lines, ‘IR54742‐23‐1‐29‐18’ (hereafter called IR54742) and ‘IR54751‐2‐41‐10‐5’ (hereafter called IR54751), selected from 243 lines derived from BC2F6 progenies of crosses between cultivated rice and wild rice (O. officinalis Wall) for resistance to the whitebacked planthopper Sogatella furcifera (Horvàth). The insect's behavioral and physiological responses were tested on the two elite lines and their parents ‘IR31917‐45‐3‐2’ (hereafter called IR31917) and wild rice. ‘IR2035‐117‐3’ (hereafter called IR2035) was the resistant check, while ‘Taichung Native 1’ (TN1) was the susceptible check. Insect food intake and assimilation, growth, longevity and fecundity, and population increase were least on wild rice. The level of insect resistance of IR54751 was comparable to that of IR2035, but insect growth was significantly more on IR54751. IR54742 was comparably less resistant than IR54751. There was no significant difference in insect responses to IR31917 and TNI. The interspecific transfer of gene(s) for planthopper resistance from wild rice to cultivated rice was confirmed.
Spike and Leaf Development of Sal‐Stressed Wheat
Authors: Maas E. V. , Grieve C. M.
Published: July 2010

Drought or salt stress while the shoot apex is in vegetative stage can markedly affect spike development and decrease yields of cereal grains. This study was conducted to determine the effects of salinity on shoot apex differentiation, particularly spike and spikelet development, and the number of tillers per plant on two wheat species (Triticum aestivum L. ‘Probred’ and T. turgidum L. ‘Aldura’). Plants were grown in greenhouse sand cultures that were irrigated four times daily with modified Hoagland's solution. Two saline treatments with osmotic potentials (Ψs) of −0.45 and −0.65 MPa were imposed beginning 4 d after planting by adding NaCI and CaCI2 (5:1 molar ratio) to the base nutrient solution and were compared to a nonsaline control treatment at −0.05 MPa. Salt stress accelerated development of the shoot apex on the mainstem and decreased the number of spikelet primordia in both species. Terminal spikelet stage occurred 12 and 18 d (≈280 and 420 thermal units) sooner Aidurand Probred plants, respectively, stressed at −0.65 than at −0.05 MPa. Anthesis also occurred earlier, but tillering was delayed 3 to 4 d. Compared with −0.05 MPa, Ψs of −0.45 and −0.65 MPa decreased seed yield 38 and 54% in Aldura and 7 and 43% in Probred, respectively. These decreases resulted from fewer spikes per plant and fewer kernels per spike. Salt stress increased the phyllochron and reduced the final number of leaves initiated on the main stem. In sam, salt stress prior to and during spikelet development significantly decreased the yield potential of individual spikes of Aldura, but not of the more tolerant Probred. Salt stress decreased the yield potential of both species most by reducing the number of tiller spikes.
Heterosis and Combining Ability among Subtropical and Temperate Intermediate‐Maturity Maize Germplasm
Authors: Beck D. L. , Vasal S. K. , Crossa J.
Published: July 2010

Information about combining ability and heterotic patterns among CIMMYT's maize (Zea mays L.) gene pools and populations should assist research programs in their hybrid development activities. A nine‐parent diallel was formed to (i) study the combining ability of CIMMYT's subtropical and temperate intermediate‐maturity maize gene pools and populations and (ii) evaluate the potential of CIMMYT's subtropical and temperate materials as exotic germplasm sources for temperate breeding programs. Parents and crosses were evaluated in 5 environments in Mexico and 11 in the USA. Highly significant, positive general combining ability (GCA) effects for yield were observed with Populations 42, 47, and 34 in Mexico. The Population 42 × Population 47 cross ranked first in yield (7.87 Mg ha−1, with 9.1% high‐parent heterosis). Population 33 x Population 45 was the only cross with a significant, positive specific combining ability (SCA) effect for yield. Average yields in U.S. environments were low (3.49 Mg ha‐I), due partially to adaptation problems and late plantings. Only Pool 41 had a significant, positive GCA effect for yield in the USA. The four highest yielding combinations included Pool 41 with Populations 42, 47, 34, and 45. In Mexican subtropical environments, superior crosses included Population 42 × Population 47 (white grain) and Population 33 × Population 45 (yellow grain). Though the CIMMYT materials did not generally perform well in U.S. environments, Pool 41 and Population 42 showed the best potential as exotic germplasm sources for temperate breeding program
Genetic Diversity in Cultivated Common Bean: I. Allozymes
Authors: Singh Shree P. , Nodari R. , Gepts P.
Published: July 2010

Previous studies using phaseolin seed protein as a marker have revealed that cultivated common bean (Phaseolus vulgaris L.) resulted from multiple domestications in Mesoamerica and in Andean South America. Because these studies were based on variation at a single locus, confirmation was sought by analyzing patterns of diversity at nine polymorphic allozyme loci, all unlinked to the phaseolin locus: ribulose bisphosphate carboxylase, shikimate dehydrogenase, cathodal peroxidase, malic enzyme, malate dehydrogenase (two loci), diaphorase (two loci), and leucine aminopeptidase. A total of 227 landraces representing geographical regions from Mexico to Argentina and Chile were analyzed for these enzyme systems. A crude homogenate of primary leaf or root tissue (depending on enzymes assayed) from five seedlings of each landrace grwon in vermiculite was used for starch gel electrophoresis. A cluster analysis based on Nei's genetic distance (D) was performed according to the unweighted paired group method of Sneath and Sokal. Our results confirm the existence of two major groups in cultivated common bean, Mesoamerican vs. Andean American; provide indications of gene flow from wild to cultivated beans; and suggest at least five subgroups within Mesoamerican and four within Andean cultivar groups.
Genetic Diversity in Cultivated Common Bean: II. Marker‐Based Analysis of Morphological and Agronomic Traits
Authors: Singh Shree P. , Gutiérrez J. A. , Molina A. , Urrea C. , Gepts P.
Published: July 2010

Knowledge of patterns of genetic diversity enhances the efficiency of germplasm conservation and improvement. This study examined the organization of diversity for morphological and agronomic characteristics in 306 landraces of cultivated common bean (Phaseolus vulgaris L.) from Latin America and its relationship with phaseolin seed protein and allozyme diversity of the landraces. Data on pigmentation, growth habit, and leaflet, pod, seed, and phenology traits, as well as reaction to four important diseases and an insect pest, obtained from field evaluations at three locations in Colombia during the 1987‐1988 cropping season, were analyzed by multivariate statistical analyses. In addition, these same 306 landraces were characterized by electrophoresis for phaseolin seed protein and nine allozymes. Results permitted separation of these landraces into Mesoamerican and Andean groups, confirming prior phaseolin and allozyme data. A marker‐based multivariate analysis, using phaseolin or allozymes as an initial classification criterion, followed by a corroborating analysis of morpho‐agronomic traits, suggested the existence of subgroups within each of the major Andean and Mesoamerican groups, with distinctive morphology, adaptation, and disease resistances. Molecular analyses in conjunction with morphological and agronomic evaluations of gene bank accessions are recommended, because these provide complementary information and increase the resolving power of genetic diversity analyses.
Screening for Resistance to Russian Wheat Aphid in Triticale
Authors: Scott R. A. , Worrall W. D. , Frank W. A.
Published: July 2010

Resistance to Russian wheat aphid (Diuraphis noxia Mordvilko)(RWA) remains scarce in hexaploid wheat (Triticum aestivum L. em. Thell.) and has been identified only in unadapted wheats. Introduction of resistance from related species is a viable alternative. A greenhouse study was conducted to identify possible sources of resistance to RWA, and to examine RWA screening techniques. After screening 133 triticale (✕ Triticosecale Wittmack) lines in replicated flat screening tests, 11 resistant lines were identified and evaluated along with 3 susceptible lines and 1 susceptible wheat for antibiosis, antixenosis, and tolerance. In preliminary screening trials, correlations of 0.50 (P ≤ 0.05) to 0.58 (P ≤ 0.01) were found between plant damage ratings and plant heights. Plant damage ratings and antibiosis values also were correlated (r = 0.55, P ≤ 0.05). Antixenosis time periods of 24, 48, and 72 h were compared. There were significant differences between resistant and susceptible lines for antibiosis and tolerance, but not for antixenosis. Number of nymphs per adult ranged from 0 to 9 in antibiosis tests. Plant stunting ranged from 0 to 16.5 cm among resistant lines and from 8 to 21.5 cm among susceptible lines in tolerance tests. Correlations among all three antixenosis evaluation times were significant. We concluded that excellent sources of RWA resistance exist in triticale, and that resistance is expressed primarily as antibiosis and tolerance.
Agronomic Trait Variation in Oat Lines Derived from Tissue Culture
Authors: Dahleen L. S. , Stuthman D. D. , Rines H. W.
Published: July 2010

Tissue culture may generate agronomic variation that is potentially useful in plant improvement. This somaclonal variation, if extensive, could pose problems when tissue culture is a component of genetic transformation or when in vitro selection procedures are used. The objective of this study was to analyze agronomic trait variation in R4 and R5 generation oat (Avena sativa L.) lines derived from R1 progeny of tissue‐culture regenerated plants (R0) that had been previously classified as having no karyotypic aberrations. Fifty‐six R4 and R5 ‘Lodi’ lines tracing to 11 R0 plants, and 213 R4 and 147 selected R5 ‘Tippecanoe’ lines tracing to 45 R0 plants were evaluated. Lines were planted in hill plots in radomized complete‐block designs with six replicates and evaluated for 2 yr at two locations. Traits analyzed were height, heading date, seed protein, flag leaf area, seed weight, seed number, grain yield, and bundle weight. Significant variation (P < 0.05) was detedted for all traits both within families (lines derived from the same R0 plant), and when lines and families were compared with the parental cultivars. Eighty‐two percent of the Lodi families and 93% of the Tippecanoe families had significant changes for at least one of the eight traits measured. Although agronomically less desirable changes were more frequent than desirable changes, liens with increases and lines with decreases were found for each trait. One cycle of successful bidirectional selection among culture‐derived lines demonstrated that the trait changes were heritable and that individual lines could be selected for use in plant improvement programs. The variation observed also demonstrates that materials produced by using directed genetic manipulation involving tissue culture should be tested extensively for possible quantitative trait variation.
Shade Effects on Growth of Tall Fescue: II. Leaf Gas Exchange Characteristics
Authors: Allard G. , Nelson C. J. , Pallardy S. G.
Published: July 2010

The irradiance environment during development affects the elongation rate and photosynthetic capacity of leaves. Our objective was to determine the effect of shade during development on stomatal and nonstomatal factors affecting photosynthesis. Vegetative plants of tall fescue (Festuca arundinacea Schreb.) were grown outdoors in pots during summer of 1986 and autumn of 1987. Irradiance treatments were provided by shading the plants with neutral‐density screencloth during a 10‐wk growth period. Gas exchange characteristics of the youngest fully expanded leaf blades were measured. Irradiance required for saturation of CO2 exchange rate (CER) at 340 µL L‐1 ambient CO2 was 1000 to 1200 µmol m2 s−1 of photosynthetic photon flux density when plants were grown at low irradiance (30% full sun) compared with 1500 µmol m−2 s−1 when grown at high irradiance (full sun). The CER per unit leaf area, measured at irradiance saturation, was 25% lower in 1986 and 14% lower in 1987 for leaves grown in low irradiance compared with leaves grown in high irradiance. Stomatal conductance to CO2 decreased similarly, causing internal CO2 concentration at irradiance saturation to be similar among treatments. When CER was expressed per unit dry weight or per mesophyll cell volume, no difference was observed between treatments. The adaptation to low irradiance of both leaf anatomical and physiological processes affecting photosynthesis was well coordinated; net CO2 uptake was decreased, but relative stomatal and nonstomatal limitations were not altered.
Competitiveness of Tall Fescue as Influenced by Acremonium coenophialum
Authors: Hill N. S. , Belesky D. P. , Stringer W. C.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) is a common pasture grass adapted to a wide range of environmental conditions. An endophyte, Acremoninm coenophialum Morgan‐Jones & Gams, growing in association with tall fescue is known to produce ergopeptine alkaloids that are thought to be detrimental to animal health. Endophyteinfection changes how tall fescue plants grow and may be involved in the adaptability of tall fescue to environmental extremes. The objective of this study was to determine whether plant‐endophyte associations that had previously tested as high and low ergopeptine alkaloid producers varied in competitive ability when their endophytes were removed. Two identical field studies were conducted on a Cecil sandy clay loam and a Pacolet sandy clay loam soil (both clayey, kaolinitic, thermic Typic Hapluduits) in 1987 and 1988, respectively. In each study, a modified Nelder's design was used to test the competitiveness between infected and noninfected forms of two tall fescue genotypes. Endophyte‐infected plants were larger and, generally, more competitive in mixtures with noninfected plants. When infected with endophyte, the high ergopeptine alkaloid‐ producing genotype of tall fescue had similar or reduced competitiveness than the low‐alkaloid genotype when compared with their noninfected forms. We conclude that if ergopeptine alkaloids can be genetically removed from tall fescue‐endophyte associations, the competitiveness of the plant would be unaffected in nongrazed conditions. Reduction or elimination of ergopeptine alkaloids would help improve animal health when consuming endophyte‐infected tall fescue forage.
Genetics of Adult‐Plant Leaf Rust Resistance in ‘Chinese Spring’ and ‘Sturdy’ Wheats
Authors: Dyck P. L.
Published: July 2010

The common wheat (Triticum aestivum L.) cultivars Chinese Spring and Sturdy have adult‐plant resistance to leaf rust caused by Puccinia recondita Rob. ex Desm. To study the genetics of this resistance both cultivars were crossed and backcrossed to ‘Thatcher’, a leaf rust susceptible cultivar. The two cultivars or resistant selections from the above crosses were also crossed with backcross lines having Lrl2, Lr13, and Lr34 genes for adult‐plant leaf rust resistance. The backcross F2 families and F2 populations were grown in a field rust nursery artificially inoculated with a mixture of P. recondita isolates. The segregation for rust reaction of adult plants indicated that both cultivars have a combination of genes Lrl2 and Lr34. To assist in the identification of Lr34 in these cultivars, adult‐plant leaf rust resistance from each cultivar was transferred into Thatcher.
Leakage of Intracellular Substances as an Indicator of Freezing Injury in Alfalfa
Authors: Sulc R. Mark , Albrecht Kenneth A. , Duke Stanley H.
Published: July 2010

Alfalfa (Medicago sativa L.) freezing tolerance is commonly determined by measuring ion leakage (by electrical conductivity) after freezing. This study was conducted to evaluate other measurements of freeze‐induced leakage of intracellular substances as indicators of freezing tolerance in alfalfa cultivars varying in fall dormancy and winterhardiness. Alfalfa crowns and roots were harvested in late fall of the seeding year and subjected to a −8 °C freezing treatment. Freezing injury was determined by measuring electrical conductivity, ultraviolet (UV) light absorbance, and oxidized nicotinamide‐adenine dinucleotide (NAD+)‐malate dehydrogenase (MDH) activity of leakage from roots after freezing. The optimal wavelength for determining freeze‐induced leakage of intracellular substances and for delineating differences in leakage among cultivars was 265 nm (A265). Percent electrical conductivity was linearly related to A265 (r2 = 0.92). Quadratic relationships were found between MDH activity and percent electrical conductivity (R2 = 0.88) and A265 (R2 = 0.90). Differences among cultivars were significant and cultivar rankings were similar for all leakage measurements. These data demonstrate that A265 and MDH activitiy of plant leakage after freezing are useful indicators of freezing injury, and that cellular rupture results from the −8 °C freezing treatment commonly used in alfalfa freezing tolerance tests. The MDH assay is more timeconsuming and variable than A265 or electrical a conductivity and is probably most useful when absolute measures of cellular rupture are important. Measuring A265 was quick and provided a good alternative to measuring electrical conductivity.
Leaf Expansion Rate Effects on Yield and Yield Components in Early‐Maturing Maize
Authors: Cross H. Z.
Published: July 2010

Assimilate supply (source) reportedly limits grain yields of early‐maturing maize (Zea mays L.) hybrids. We studied combining abilities of S2 lines with extremes in average leaf expansion rate (ALER) values to test for genetically correlated responses for grain yield, ear moisture, stalk lodging, yield components, and yield stability parameters. The S2 hybrids were selected to represent a 2 ✕ 2 factorial arrangement of ALER types (HER = high and LER = low ALER). Two groups of lines (GI and GII) were selected from S2 lines previously rated using the formula ALER = (leaf number ✕ length ✕ width ✕ 0.75)/(d to pollination). Four sets of lines with extremes for ALER ratings were paired by source population, year of evaluation, and silking date. Within each set, the four S2 lines from GI were crossed to the four S2 lines from GII to produce 16 hybrids representing a 2 ✕ 2 factorial arrangement of four hybrids each of HER ✕ HER, HER ✕ LER, LER ✕ HER, and LER ✕ LER classes. Maize hybrids were grown in field experiments arranged in simple lattice designs with two replicates in seven environments. Across all environments, hybrids from HER parents yielded 8.5 and 6.9% more than LER hybrids for GI and GII, respectively. for both GI and GII, the HER hybrids produced kernel weights 0.06 g heavier than LER hybrids. The HER parents produced hybrids with ears 33 g kg−1 lower in moisture at harvest in GI. Our data support the theory that source limits yield of early maize. We suggest that selecting for HER should be a simple, effective means of increasing the source without increasing ear moisture at harvest.
Disease Resistance and Morphologic Traits of Pearl Millet Landraces from South Burkina Faso
Authors: Wilson J. P. , Burton G. W. , Zongo J. D. , Dicko I. O.
Published: July 2010

Disease resistance and morphologic traits of 106 landraces of pearl millet [Pennisetum glaucum (L.) R. Br.] collected in south Burkina Faso were evaluated to distinguish potentially different sources of resistance. Selfed (S1) plants were inoculated with isolates of Pyricularia grisea (Cooke) Sacc. (leaf spot), Puccinia substriata Ellis & Barth. var. indica (rust), and Moesziomyces penicillariae (Bref.) Vánky (smut) collected in Georgia. Height and flowering dates of greenhouse‐grown S0 plants, S1 seed characteristics, and frequencies of chlorophyll‐deficient S1 seedlings were evaluated. Among landraces, the frequency of plants resistant to Py. grisea ranged from 51.9 to 99.1% (x = 82.5%). Frequencies of plants resistant to Pu. substriata ranged from 0 to 44.2% (x = 10.1%). Differences in resistance to M. penicillariae existed among the landraces. Percent smutted florets ranged from 0.8 to 8.4% (x = 4.2%). Seed set in the smut evaluation averaged 24.3% and was correlated with smut infection. In the greenhouse, S0 plant height and days to flowering averaged 2.3 m and 60.4 d, respectively. Seed color was generally light gray; seeds were typhoides shaped, with a mean 100‐seed weight of 1.20 g. Five clusters of phenotypic diversity were identified among the landraces by principal component and cluster analyses, and several potentially different sources of disease resistance were identified. Nine pairs of the landraces and an additional landrace clustered with one of the pairs may be duplicate accessions.
Diversity and Relationships among U.S. Maize Inbreds Revealed by Restriction Fragment Length Polymorphisms
Authors: Melchinger A. E. , Messmer M. M. , Lee M. , Woodman W. L. , Lamkey K. R.
Published: July 2010

Restriction fragment length polymorphisms (RFLPs) have been proposed as molecular markers for characterizing the genetic diversity in maize (Zea mays L.). The objectives of this study were to evaluate the usefulness of RFLP data for (i) elucidating heterotic patterns among maize inbreds and (ii) assessing genetic similarity among related and unrelated lines. Thirty‐two maize inbreds from the U.S. Corn Belt were analyzed for RFLPs with two restriction enzymes and 83 DNA probes distributed over the maize genome. Eighty‐two probes detected polymorphisms with at least one enzyme. On average, 4.3 variants were found per probe‐enzyme combination across all 32 inbreds. Genetic distances among lines, estimated from RFLP data as Rogers' distance (RD), revealed considerable diversity among lines from Iowa Stiff Stalk Synthetic (BSSS), Reid Yellow Dent (RYD), and Lancaster Sure Crop (LSC). Lines from different heterotic groups had a slightly greater RD mean than unrelated lines from the same heterotic group, yet differences were small when compared with the wide range of RDs for individual lines combinations within each group. RDs between related lines agreed well with expectations based on coancestry coefficients determined from pedigree data with few exceptions. Principal component analyses of RFLP data resulted in a separate grouping of lines from BSSS/RYD and LSC. Dispersion of lines of miscellaneous origins was generally consistent with expectations based on known breeding behavior and pedigrees. Results from this study suggest that RFLP data can be used for assigning inbreds into heterotic groups and quantifying genetic similarity between related lines, but it seems that a large number of probe‐enzyme combinations are required to obtain reliable estimates of genetic distance.
Soybean Growth Response to Plant Density: Relationships among Canopy Photosynthesis, Leaf Area, and Light Interception
Authors: Wells Randy
Published: July 2010

Plant spacing greatly affects leaf area, light interception, and canopy apparent photosynthesis (CAP) in soybean [GLycine max (L.) Merr.]. This study examined relationships among these variables in four population‐density and row‐width treatment combinations for two seasons. Wide‐row (0.96 m) treatments were 3,11, and 18 plants m−2 in 1988 and 3, 15, and 24 in 1989; narrow‐row (0.43 m) treatments were 12 plants m−2 in 1988 and 13 in 1989. Narrow‐row treatments tended to have greater CAP rates during early growth in 1988, but not 1989, when rates lagged behind the wide‐row, high population. The reduction in CAP by the narrow‐row treatment in 1989 corresponded to its reduced light interception as measured parallel to the row base. Both total radiation (300‐2500 nm wavelengths) interception measured in 1988, and average photosynthetically active radiation (400‐700 nm) interception measured in 1989, were linearly related to CAP prior to, but not after, canopy closure. Similarly, leaf area indices (LAI) were curvilinearly related to percent light interception until canopy closure. After canopy closure, light interception did not decline at a rate commensurate with the loss of leaf area, indicating abscission of leaves not involved in light interception. Canopy photosynthesis was not different for any treatment after Reproductive Stage R5 in either year; however, significant differences were evident between Rl and R5 in 1989. These differences corresponded to the significantly lower yield of the low population in that year. Yield differences between the medium populations of the wide and narrow rows were not explained by CAP during reproductive growth. The data indicate that when LAI is above critical levels in post‐anthesis soybean canopies, factors other than photosynthesis may be involved in the response of seed yield to variation in plant density.