bluuebunny/crossref_metadata_2025 huggingface dataset:
Productivity and Tobacco Budworm Resistance of Cotton Developed between 1890 and 1986
Authors: Wharton Tommy F. , Jenkins Johnie N. , McCarthy J. C. , Parrott W. L.
Published: July 2010

There is a paucity of information on the relationships between modern (i.e., released in or after 1978) and historically obsolete cotton (Gossypium hirsutum L.) cultivars with respect to their ability to yield when grown in the presence of high levels of tobacco budworm (TBW), Heliothis virescens F. The objective of this study was to compare 18 cultivars of cotton developed between 1890 and 1986 for ability to yield when grown with and without TBW infestations. This comparison was accomplished by growing cultivars for 2 yr under two regimes: (i) artificial infestation with TBW (w/TBW) and (ii) complete control of all insect pests (w/o TBW). The regression equation for lint percentage w/o TBW on lint yield w/o TBW was Y = 26.8 + 0.0076 X, with an R2 of 0.58. Thus, lint percentage has increased 0.76% for every 100 kg ha‐1 increase in lint yield. Theregression equation for number of bolls w/o TBW on lint yields w/o TBW was y = 73,689 + 402 X, with an R2 of 0.83. The regression equation for lint yield w/TBW on lint yield w/o TBW was Y = ‐48.4 + 0.69 X, with an JP of 0.84. Thus, for every 1.00 kg of lint yield increase due to breeding during the 96‐yr period there was a corresponding lint yield increase under TBW infestation of only 0.6 kg. The newer cultivars yielded more than the older cultivars, with number of boils per unit area and lint percentage being the primary components involved in increased yields. Some of the newer cultivars yielded as much w/TBW as some of the older cultivars w/o TBW. In addition, the newest cultivar (DES 119; 1986) yielded significantly more than any other cultivar when grown w/o TBW. It also yielded significantly more when grown w/TBW than any cultivar developed before 1982.
Inheritance of Resistance to Race 4 of Downy Mildew Derived from Interspecific Crosses in Sunflower
Authors: Miller J. F. , Gulya T. J.
Published: July 2010

Race 4 of downy mildew, incited by Plasmopara halstedii (Farl.) Berl. & de Toni, was first reported in sunflower (Helianthus annuus L.) in the USA during 1985. Resistance to this race was found in lines derived from interspecific crosses of cultivated sunflower with three species of wild sunflower. The objectives of this investigation were to determine the genetic control of resistance found in the interspecific crosses and to determine if this resistance was conditioned by the same or different genes. Ratios tested utilizing a chisquare analysis for goodness of fit for F2 and BC1F1 generations indicated that resistance to Race 4 was conditioned by a single, dominant gene in all sources. Four lines (HA 335, HA 336, Charata R4, and Wild Ornamental) were determined to have the same resistance gene PI6. HA 335 and HA 336 were derived from wild H. annuus 423 and H. annuus 432, respectively. The resistance gene in HA 339, derived from H. praecox Engelm. & Gray ssp. runyonii, proved to be different and was designated PI7. The resistance gene in RHA 340, distinct from PI6 and PI7 and derived from H. argophyllus Torrey & Gray, was designated PI8. Using divergent resistance genes in sunflower commercial hybrids should decrease genetic vulnerability to changes in pathogenicity of downy mildew. However, additional wild species of sunflower should be collected and tested to identify new sources of resistance to downy mildew.
Lack of Relationship between Relative Maturity and Genome Size in Hybrid Maize
Authors: McMurphy Lisa M. , Rayburn A. Lane
Published: July 2010

Correlations between genome size and area of geographic adaptation have been reported in maize (Zea mays L.). Such correlations have been suggested to occur due to lower genome sizes being more favorable where shorter growing seasons exist. The objective of this study was to determine if genome size and relative maturity are correlated in hybrid maize. Thirty hybrids, obtained from Pioneer Hi‐Bred International, Inc. (Johnson, IA), were analyzed. Genome size determinations were made using flow cytometric techniques. No correlation between genome size and relative maturity was observed. Since the area of adaptation of these hybrids encompasses a wide range of latitudes, there appears to be no correlation between genome size and latitude as well. The lack of correlations among these characters may result from the breeding structure of hybrid maize.
Performance and Inbreeding Depression between a Synthetic and Three Improved Populations of Maize
Authors: Walters S. P. , Russell W. A. , Lamkey K. R. , White P. R.
Published: July 2010

Effective recurrent selection for a quantitative trait will increase the frequency of favorable alleles in the maize population. As a result, fewer deleterious alleles are expressed for the quantitative trait when inbreeding. This study was conducted to compare performance and inbreeding depression in the original Iowa Stiff Stalk Synthetic (BSSSC0) maize (Zea mays L.) population, two improved Iowa Stiff Stalk populations [BSSS(R)C9 and BS13(S)C3], and the cross between the improved populations (C3 ✕ C9). The improved populations of BS13(S)C3 and BSSS(R)C9 yielded similarly to BSSSC0, whereas the S1 generation of BS13(S)C3 and BSSS(R)C9 yielded significantly greater than the S1 of BSSSC0. The C3 ✕ C9 population showed high‐parent heterosis at the S0 and S1 generation levels. Only the BS13(S)C3 population showed significantly less inbreeding depression than did BSSS. Differences among the three improved populations for inbreeding depression of grain yield were not significant.
Regrowth of Bermudagrass Infected with Spring Dead Spot Following Low Temperature Exposure
Authors: McCarty Lambert B. , DiPaola Joseph M. , Lucas Leon T.
Published: July 2010

Spring dead spot (SDS) (Gaeumannomyces graminis (Sate.) Arx & Olivier var. graminis) is a serious disease of intensively managed bermudagrass (Cynodon spp.) turf throughout much of the world. Research was undertaken in North Carolina to determine (i) if exposure of previously G. graminis infected turf to low temperatures would result in the reduced bermudagrass regrowth; and (ii) if shoot regrowth potential differed between healthy and G. graminis infected bermudagrass. Bermudagrass samples extracted October through April from healthy and previously afflicted SDS areas were exposed to temperatures of −3 or −5 °C in an artificial chamber. Samples were then allowed to regrow in the greenhouse for 30 d under light followed by 20 d under dark conditions in the greenhouse. Shoot regrowth following each time period was collected, dried, and weighed. The G. graminis infected bermodagrass had 48 to 68% less shoot regrowth during winter and spring sampling periods, respectively, compared with uninfected plugs. Compared with healthy bermudagrass, G. graminis infected turf also had regrowth reduction of 41 to 71% following exposure to −3 °C after January. Reduction of shoot regrowth for G. graminis infected compared with healthy turf was as great as 95% following exposure to −5 °C. For infected turf, exposure to ‐5 °C reduced regrowth 64% more than exposure to −3 °C. Turf carbohydrate reserves, measured as shoot regrowth under dark conditions, were 70% less for infected turf compared with healthy areas during fall and winter months. In conclnsion, turf injury to G. graminis infected bermudagrass increased as low‐temperature stress increased. Injury to G. graminis infected bermudagrass occurred following low‐temperature exposure. Injury in the field occurs most often after December, but can be induced earlier by earlier exposure to −5 °C for ≥1 h.
Soybean and Soybean Cyst Nematode Response to Soil Water Content in Loam and Clay Soils
Authors: Heatherly Larry G. , Young Lawrence D.
Published: July 2010

Soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) a major pest of soybean [Glycine max (L.) Merr.] in the southeastern USA. The objective of this study was to determine the effect of wet and dry silt loam and clay soils on SCN development and corresponding soybean yield response in a greenhouse study. ‘Tracy‐M’ soybean was grown in pots that contained either Dubbs silt loam(fine‐silty, mixed, thermic Typic Hapludalf or Sharkey clay (very fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) surface soils that were watered to maintain adequate soil water potential (SWP) (−30 kPa SWP, wet treatment), or had water added at onehalf the rate of the adequate treatment (dry treatment). Nematode treatments were either infested or noninfested. Experiments were conducted in 1987, 1988, and 1989, and new soil was infested each year. Number of cysts increased significantly with time in the wet silt loam treatment, stayed the same as the initial infestation in the dry silt loam treatment, and declined significantly in both the wet and dry clay treatments in all years of the study. Infestation by SCN caused a reduction in seed yields in both soils, but the decrease was less in the clay soil. Soil water content in each soil interacted with level of SCN infestation to influence soybean yield. The interaction was not dependent on similar SCN infestation levels between soils, or similar differences in SCN infestation between wet and dry soil treatments within soil. Yield declines associated with SCN infestation were highly correlated with number of seed. These results indicate that SCN will not maintain populations in fine‐textured clay soil under greenhouse conditions, nor result in the magnitude of yield decline that often is measured in coarse‐textured soil.
Isoenzymatic Identification of Quantitative Trait Loci in Crosses of Elite Maize Inbreds
Authors: Abler B. S. B. , Edwards M. D. , Stuber C. W.
Published: July 2010

This study was conducted to determine if, in crosses among elite inbred lines of maize (Zea mays L.) that are more similar morphologically than the lines used in previous studies, sufficient variation is present to detect quantitative trait loci (QTLs) using marker‐facilitated procedures and to compare elite lines for sources of superior genes. Twenty‐two isozyme loci and one additional locus (P), scored by glume color on the cob, served as genomic markers for detecting QTLs affecting 21 quantitative traits in six F2 populations derived from five elite inbred lines (B73, Mo17, Oh43, Tx303 and T232). A significant effect was found to be associated with at least one chromosomal region for every trait analyzed in the six elite‐cross F2 populations. Despite the greater morphological similarity of the elite lines compared with lines used in previous studies, the number of significant associations detected was similar to results of previous studies, after accounting for differences in population size. Up to 15% of the total phenotypic variation could be explained by factors linked to a single marker locus. The type of gene action at each significant association was determined and the results showed that broad generalizations can be made regarding the gene action for groups of traits. Comparisons made between populations showed that certain areas of the genome consistently affected specific traits: i.e., ear length and grain weight at Amp3 on Chromosome 5 and ear circumference at Glul on Chromosome 10.
Genetic Analyses of Male‐Fertility Restoration in Wheat: III. Effects of Aneuploidy
Authors: Du Hanlin , Maan S. S. , Hammond J. J.
Published: July 2010

Effects of aneuploidy and modifier genes on the expression of male‐fertility restoring (Rf) genes were studied in five sets of monosomics from crosses involving male‐sterile ‘Chris’ monosomics and five R‐lines of wheat, Triticum aestivum L. Two lines were RflRfl, two were Rf4Rf4, and one (the progenitor of the other four lines) was RflRfl Rf4Rf4 and had other unidentified Rf genes. Rf1 and Rf4 are located on Chromosomes 1A and 6B, respectively. The fertility of the F1 monosomics within and between the five sets of crosses indicated that one RflRfl and one Rf4Rf4 line had additional recessive male‐fertility restoring genes. Also, the fertility was significantly enhanced in some of the F1 monosomics of homoeologous Groups 1 and 7, greatly reduced in the F1 monosomics of Groups 3 and 6, and substantially reduced in five other monosomics: 2A, 2B, 4B, 5B, and 5D. Thus, male fertility in this material is evidently conditioned by interactions among genes located on at least 17 chromosomes of wheat. The enhanced fertility of the F1 monosomics of homoeologous Groups 1 and 7 is attributed to the action of homoeoalleles in those groups which function better in five doses than in the normal six.
Sex Ratios and Inheritance of Anther and Stigma Color in Diploid Buffalograss
Authors: Huff David R.
Published: July 2010

The lack of genetic information on buffalograss [Buchloë dactyloides (Nutt.) Engelm.] may be due to the high ploidy level (2n = 40 and 2n = 60) of all reported U.S. germplasm. This study was conducted to confirm the existence of a Mexican diploid (2n = 20) race and to initiate genetic analysis in buffalo‐grass by examining male‐to‐female sex ratios and inheritance of anther and stigma color. Cytological investigation confirmed the existence of the diploid race (2n = 20). Sex ratios were 1:1 at the population level, but were significantly (P < 0.01) male biased for particular parents. A polygenic sex determining mechanism was hypothesized. Anther color was either red or blue and stigma color was either purple or clear (absence of pigmentation), and were found to be readily observable and consistently expressed. Blue anther color was controlled by a single recessive allele that was assigned the symbol b. Clear stigmas were inherited as a bifactorial double recessive trait
Reduction in Insecticide Use Associated with Cotton Resistant to Pink Bollworm
Authors: Wilson F. Douglas , Flint Hollis M. , Bariola Louis A. , Chu Chang Chi
Published: July 2010

Cotton (Gossypium hirsutum L.) growers use significant quantities of insecticides to control pink bollworm (PBW), Pectinophora gossypiella (Saunders). The germplasm line WC‐12NL (nectariless, okra leaf, and early maturing) and ‘Deltapine 61’ (nectaried, normal leaf, and later maturing) were grown at Maricopa, AZ, and Brawley, CA, for three seasons. Irrigation water was terminated and plots were defoliated earlier than normal, a practice that favored the early maturing line. Insecticides were applied as needed, based on PBW egg infestations of cotton bolls. The major objective was to determine whether insecticide use can be reduced or eliminated by growing WC‐12NL. Other objectives were to compare WC‐12NL with Deltapine 61 for PBW resistance, yield, earliness, and fiber properties; to study location and seasonal effects; and to determine whether the growth‐regulating chemical ethephon (2‐chloroethylphosphonic acid) would cause bolls to open earlier. The mean number of insecticide applications was 41% lower for WC‐12NL than for Deltapine 61. First and last application dates averaged 21 d later and 10 d earlier, respectively, for WC‐12NL. WC‐12NL had significantly less seed damage caused by PBW, yielded significantly more lint, was significantly earlier, but had inferior fiber properties compared with Deltapine 61. Ethephon treatment increased earliness of Deltapine 61 but did not affect that of WC‐12NL, probably because it was applied too late. Location and seasonal effects and numerous interactions occurred, but did not alter the main conclusion that a cotton line such as WC‐12NL (but with improved fiber properties) could be valuable in areas where PBW is a problem.
Visualizing Differences in Plant Water Dynamics with a Simulation Model
Authors: Fernández C. J. , McCree K. J.
Published: July 2010

The model Plant Water Dynamics makes it possible to visualize the dynamic interactions of water fluxes and water potential gradients in plants. Inputs to the model were systematically varied until the outputs closely matched published data for three species that showed contrasting responses to water stress under controlled environment conditions. The analysis revealed that cowpea [Vigna unguiculata (L.) Walp.] plants minimized dehydration and maintained relatively high leaf water potentials by closing their stomates, while sugarbeet (Beta vulgaris L.) and sorghum [Sorghum bicolor (L.) Moench] plants became dehydrated because their stomates were relatively insensitive to decreases in leaf water potential, and because osmotic adjustment delayed stomatal closure. The observation that leaf water potentials were generally lower in sugarbeet than in sorghum was explained by a lower xylem conductance. Stomatal conductance was lower in sorghum than in sugarbeet under well‐watered conditions. This conservative behavior allowed sorghum to delay the onset of a plant water deficit by producing more xylem vessels.
Comparative Salinity Responses among Pigeonpea Genotypes and Their Wild Relatives
Authors: Subbarao G. V. , Johansen C. , Jana M. K. , Rao J. V. D. K. Kumar
Published: July 2010

Soil salinity can be a major constraint to pigeonpea (Cajanus cajan (L.) Millsp.) in the regions where it is predominantly grown. This study was conducted to assess the extent of genetic variation for salinity tolerance in the germplasm of pigeonpea and its wild relatives. Solution culture experiments in a greenhouse and controlled environment chamber were conducted to screen a range of cultivated pigeonpea genotypes for ability to germinate and grow up to 60 d under saline conditions. Several wild relatives of pigeonpea were screened for salinity response in a sand culture system in a greenhouse. Among cultivated pigeonpea genotypes, ICPL 227 was one of the most tolerant and HY 3C one of the most sensitive genotypes tested. None of the pigeonpea genotypes tested were able to survive beyond 30 d at 8 dS m−1 or higher salinity levels. The extent of variation in salinity response among cultivated pigeonpea genotypes appeared too limited to warrant genetic enhancement of salinity tolerance. Among the wild relatives of pigeonpea, various species of Atylosia, Rynchosia, and Dunbaria showed a wide range of variation in their salinity tolerance (critical levels from 4 to 12 dS m−1): A. albicans (W. & A.) Benth., and A. platycarpa could grow in a sand culture system at 12 dS m−1 and Rynchosia albiflora could not tolerate salinity levels above 4 dS m−1. These results suggest that using wild relatives for genetic improvement may increase salinity tolerance of pigeonpea.
Visual Markers of Maximum Grain Dry Weight Accumulation in Winter Wheat
Authors: Smith D. H. , Donnelly K. J.
Published: July 2010

Visual indicators that coincide with the time of maximum grain dry weight accumulation (tmax) in hard red winter wheat (Triticum aestivum L.) have not been confirmed. Our objective was to evaluate various potential visual markers of tmax for a range of cultivars in typical Great Plains environments. Spikes of uniform maturity from five hard red winter and one soft white winter wheat cultivars were harvested throughout grain filling and divided into upper, middle, and bottom portions to determine grain dry weights. For each cultivar‐year combination, tmax values for each spike portion and the entire spike were calculated using polynomial models derived from splined regression analysis. These values were compared with various visual traits observed at each harvest. There was no significant variation in tmax among the three spike portions. Complete loss of green color from the flag leaf blade and sheath preceded tmax by several days in all cultivars; green color in the node below the peduncle persisted 2 to 6 d beyond tmax. Complete loss of green color from the rachis, glumes, and the crease of kernels occurred within 1 d of tmax in all cases. The same was true for loss of awn color, except for the soft white winter cultivar, in which green color loss from awns occurred 2 d before tmax. Thus, color loss from most portions of the spike should serve as accurate indicators of tmax for hard red winter wheat in central Great Plains environments.
Rapid Isolation and Measurement of Adenosine Triphosphate Levels in Corn Embryos Germinated at Suboptimal Temperatures
Authors: Schell L. P. , Danehower D. A. , Anderson J. R. , Patterson R. P.
Published: July 2010

The trend towards earlier planting dates and conservation tillage systems in corn (Zea mays L.) production has prompted interest in accurate methods for predicting cold tolerance in germinating seedlings. Measurement of nucleotide phosphate levels in germinating seed has been proposed as one such method, but has proven to be a tedious procedure to apply to plant materials. A nucleotide extraction technique was combined with high performance liquid chromatography (HPLC) and applied to the measurement of adenosine triphosphate (ATP) in germinating corn embryos. Embryo ATP concentrations were determined for seed lots of two corn hybrids imbibed over a 96‐h period at two temperatures, 10 and 20 °C. The lower temperature reduced ATP levels and accumulation rates for both cultivars. Differences in the embryo ATP concentrations of the respective hybrids were apparent after 32 h of imbibition at 10 °C. Differences in the ATP accumulation rate of those embryos were detectable 4 to 16 h into the germination process. Significantly lower quantities of ATP in one hybrid (Dekalb‐Pfizer XL 72B) germinated at 10 °C for 64 h were associated with a corresponding reduction in cold‐test germination percentage of that seed. Measurement of embryo ATP levels for six additional hybrid seed lots after 64 h of germination at 10 °C revealed significant variations in ATP concentration. Correlation of embryo ATP levels and cold‐test germination percentages with the field performance of these hybrids indicated that embryo ATP levels were a more reliable predictor of cold tolerance than the cold germination test.
Population Definition, Sample Selection, and Calibration Procedures for Near Infrared Reflectance Spectroscopy
Authors: Shenk J. S. , Westerhaus M. O.
Published: July 2010

Near infrared spectroscopy relies heavily on the collection of an appropriate population of samples for calibration and the best mathematical procedure to obtain the most accurate calibration. The purpose of this study was to evaluate two algorithms (CENTER and SELECT) for defining the population and selecting samples for calibration. The selected samples were used to compare modified partial least squares regression (MPLSR) with modified stepwise regression (MSR) calibration method. The algorithms were developed to (i) establish the boundaries of a population of samples in terms of the standardized Mahalanobis distance (H) from the mean and (ii) select a small, structured set of samples for calibration using the standardized H distance between sample pairs. Two diverse populations of samples were used to test these approaches. Calibrations were performed using MPLSR and MSR. A standardized H distance of 3.0 from the mean was used as a boundary for excluding spectral outliers from a population, and a minimum standardized H distance between samples of 0.6 provided an adequate number of calibration samples for accurate predictions. Both regression methods provided acceptable validation statistics for crude protein, acid detergent fiber, and in vitro dry matter disappearance. The MPLSR calibration method gave an overall 18% improvement in standard error of performance (SEP) compared with the MSR calibration method.
Cross‐Pollination Technique for Spontaneously Self‐Pollinated Sweetclover
Authors: Miller J. E. , Viands D. R. , LaRue T. A. , Gorz H. J.
Published: July 2010

There is increased interest in using a dwarf, spontaneously self‐pollinated accession (U389) of annual, white‐flowered sweetclover (Melilotus alba Desr.) for studying N2 fixation and for characterizing the photosynthetic apparatus. Genetic analysis of this accession may therefore be required. In a study of the inheritance of 10 nonnodulating U389 mutants > 2000 crosses made in the late bud stage were unsuccessful probably because florets were mishandled during the crossing procedure. Development of an improved crossing technique resulted in production of hybrid seed from 20% of the emasculated and pollinated florets. This successful technique is described in detail for future use by researchers making crosses with spontaneously self‐pollinated sweetclovers similar to U389.
Genetic Parameters for Oil Yield in a Population of Cuphea lanceolata
Authors: Webb D. M. , Knap S. J.
Published: July 2010

Cuphea lanceolata Ait. f. is a new oilseed crop being developed as a source of capric acid. Little is known about genetic variation for economically important traits in this or other Cuphea species. Our objectives were to estimate genetic parameters for oil yield, seed yield, seed oil content, and seed weight using half‐sib families in two diverse environments and to devise a selection scheme for oil‐yield improvement in C. lanceolata. In 1987, we derived 160 half‐sib families from a broad‐based synthetic population (LN‐43). These families were grown in a replications‐in‐incomplete‐blocks experiment design at Corvallis and Medford, OR in 1988. There were significant (P ≤ 0.05) additive genetic variances for all traits based on individual‐location analyses and for all traits except seed yield based on combined‐location analyses. Family ✕ location variances were significant (P ≤ 0.05) for oil and seed yields. Family‐mean heritabilities for oil yield, seed yield, oil content, and seed weight were 0.24, 0.20, 0.46, and 0.58, respectively. Additive genetic correlations of oil yield with seed yield, oil content, and seed weight were 0.93, 0.91, and 0.85, respectively. The significant additive genetic variances, moderate heritabilities, and positive expected selection responses observed in LN‐43 for oil yield suggests this population has adequate genetic variation for increasing the mean oil yield per unit area of C. lanceolata. Selections for oil‐yield improvement should be by direct selection based on results at Medford where the environment was more appropriate for the commercial production of C. lanceolata.
selection for Groat‐Oil Content in Oat Grown in Field and Greenhouse
Authors: Schipper H. , Frey K. J.
Published: July 2010

Selection for quantitative traits of oat (Avena sativa L.) usually is based on field experiments. The objective of this study was to determine whether a greenhouse could be utilized to select for greater groat‐oil content in oat. Forty‐eight oat lines from the C0 to C3 of a recurrent selection program to increase groat‐oil content were evaluated in the field and greenhouse in 1987 and 1988. Groat‐oil contents of large and small samples of oat groats were determined for each entry in each environment except for small samples from the greenhouse in 1987. The genetic correlation between groat‐oil contents of field‐ and greenhouse‐grown plants was 0.87, and between groat‐oil contents of large and small samples 1.14. Estimates of heritabilities, variances, and genetic correlations were used to compute the predicted genetic gains, expressed under field conditions, from one cycle of each of three recurrent selection regimes. A regime that utilized selection among S0 plants in the field followed by selection among and within selected S0:1 progenies in the greenhouse gave annual predicted gains in groat‐oil content that were 38 and 186% greater than predicted gains from phenotypic recurrent selection regimes with selection among field‐ and greenhouse‐grown S0 plants, respectively. Thus, selection for groat‐oil content in oat on the basis of data from the greenhouse can be successfully incorporated into a recurrent selection program.
Salinity Resistance, Water Relations, and Salt Content of Crested and Tall Wheatgrass Accessions
Authors: Johnson Richard C.
Published: July 2010

Salinity is a significant factor in reducing stand establishment and productivity of grasses on certain rangeland sites. Research was undertaken to identify crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] accessions potentially useful in breeding salt‐resistant populations and to determine physiological factors associated with the superior salinity resistance of tall wheatgrass [Thinopyrum ponticum (Podp.) Barkw. & Dewey] compared to crested wheatgrass. Forage production under saline (irrigation with −0.6 MPa NaCI solution) and nonsaline conditions was examined in plants grown in sand culture. Consistent differences in forage salinity resistance (forage dry wt. of salinity stressed plants/forage dry wt. of unstressed plants) were not detected, but crested wheatgrass accessions were identified with both high salinity resistance at germination and high forage production under saline and nonsaline conditions. High forage‐producing crested wheatgrass accessions under salinity stress showed certain physiological responses similar to salt‐resistant tall wheatgrass. Tall wheatgrass and high producing crested wheatgrass maintained average leaf turgor of 1.0 MPa over a range of NaCI irrigation solutions from 0 to −1.8 MPa, but turgor of low‐producing crested wheatgrass was reduced by −1.2 and −1.8 MPa solutions. In −0.6 MPa solutions, tall wheatgrass and high forage‐producing crested wheatgrass accessions had higher concentrations of K, lower Na, and lower Na/K ratios in leaves than low‐producing crested wheatgrass. Concentrations of K, Na, and CI in root tissue did not differ in crested wheatgrass. Tall wheatgrass, however, had consistently higher root K, Na, CI, and lower Na/K ratios than crested wheatgrass. The results suggest that high forage production under saline conditions was related to turgor maintenance, lower Na/K ratios, and mechanisms for partial exclusion of Na in leaves.
Ethanolic Fermentation in Hypoxic Cotton Seed
Authors: Lehle Fredric R. , Zegeer Abreeza M. , Ahmed Omar K.
Published: July 2010

Cotton (Gossypium hirsutum L.) roots die within a few hours in the total absence of O2, but can continue growing for several hours at a reduced rate very low at O2 concentrations, even <10 mmol O2 mol−1. The physiology of this adaptive response has not been well characterized. The objective of this study was to determine if ethanolic fermentation occurs in cotton seeds under hypoxic conditions that inhibit but do not prevent radicle growth. Germinating seeds, after 23 h imbibition at 32 °C, were incubated for ≤4.5 h at 28 °C in sealed flasks. Hypoxic conditions (6‐9 mmol O2 mol−1) were imposed by gassing flasks with either N2 or CO2. Fermentation was measured as the production of ethanol and acetaldehyde, which were quantified by gas‐liquid chromatography. Both ethanol and acetaldehyde were readily produced during hypoxia at an average rate of 439 and 9.69 nmol h−1 seed−1, respectively, at 28 °C. Acetaldehyde‐and ethanol‐forming capacity increased substantially during the first 16 h following onset of imbibition. Seeds imbibed under hypoxia for only 3 h produced little ethanol or acetaldehyde. Small amounts of acetaldehyde and ethanol were produced by hydrated seeds imbibed in air. Ethanol produced during fermentation was rapidly assimilated if O2 stress was relieved. During a 2‐h hypoxic stress that promoted fermentation, radicle growth was halted, but resumed at a reduced rate. Inhibition was short‐lived and radicle growth recovered fully in air. Results indicate that ethanolic fermentation is a major metabolic response to hypoxia in germinating cotton seeds.
Principal Component and Cluster Analyses of Cotton Cultivar Variability across the U.S. Cotton Belt
Authors: Brown J. Steven
Published: July 2010

Though few examples of multivariate analyses of agronomic trials exist in the literature, such analyses can provide useful additional information as a supplement to normal univariate analyses. In this study, data from the Regional Cotton Variety Tests were used to study the interrelationships of cotton (Gossypium hirsutum L.) cultivars based on agronomic and fiber trait measurements. The study of agronomic variability among cultivars was reflective, in part, of genetic variability, and gave graphical, nonnumerical assessments of genetic variability. Principal component, hierarchical (Ward's minimum variance) cluster, and nonhierarchicai (k‐means) cluster analyses were computed on data from seven of the nine regions of the tests. Check cultivars were common across regions, enabling comparisons of results within and across regions. Three‐dimensional plots displayed results of the principal component and k‐means duster analyses, while results from Ward's minimum variance clustering were presented as dendrograms. Cultivars in the Mississippi Delta, Central, and Texas High Plains regions did not duster tightly, whereas cultivars in the Eastern, New Mexico, and San Joaquln Valley regions clustered comparatively tightly. This implies greater intercultivar differences in the first three regions than in the latter three, which shows the genetic bases of the first three to be broader. New Mexico Aeala cultivars clustered less tightly than Acala cultivars in the San Joaquin Valley, likewise implying a broader genetic base in the New Mexico cultivars. Check cultivars tended to cluster as outliers outside their region of adaptation.
Heterosis in Crosses between American and Spanish Populations of Maize
Authors: Ordás A.
Published: July 2010

Most maize (Zea mays L.) crosses in te mperate zones use the heterotic pattern Reid ✕ Lancaster, but in western Europe the pattern U.S. dent ✕ European flint has also been used. This study was undertaken to determine the heterotic relationships between Spanish and U.S. Corn Belt germplasm to identify a heterotic pattern for a comprehensive system of breeding. Four early U.S. Corn Belt and five Spanish populations were crossed in a diallel series that was tested for three years at two locations. Using heterosis for yield as the measure of dissimilarity, a phenogram showed the existence of three groups of populations: U.S. Corn Belt, northern Spain, and southern Spain. Two composites were formed, one with germplasm from northern Spain (EPS6) and the other with germplasm from southern Spain (EPS7), that were subjected to one cycle of S1 recurrent selection. The yield gains were 10.4 and 9.4% for EPS6 and EPS7, respectively. The mid‐parent heterosis was 32.7%, much greater than predicted (17.7%). Spanish germplasm can be a useful addition to maize breeding programs of temperate zones, enhancing the genetic base of the material being used.
Fractional Integrated Stomatal Opening to Control Water Stress in the Field
Authors: Fiscus Edwin L. , Mahbub‐Ul Alam A. N. M. , Hirasawa Tadashi
Published: July 2010

The usefulness of totally automated irrigation control systems is well established. Mass‐flow porometers can be used as the sensing and feedback elements to implement such a system for the experimental control of water stress in the field. This study was conducted to determine if consistent relationships could be established between the mass‐flow readings and other water‐related physiological parameters. A range of stress conditions were imposed on plots of corn (Zea mays L.) by the system during the 1986 and 1987 field seasons in Greeley, CO. Midday leaf xylem water potential, leaf diffusive conductance, and year‐end grain yields were measure during both years. In 1987, additional measurements were made of the infrared canopy temperature for calculating the Crop Water Stress Index (CWSI), and individual kernel weights and numbers, to determine the components of the grain yield predictions observed in 1986. Reductions in the number of kernels produced per unit land area were associated with stress‐induced delays of silking relative to pollen shed. Additional yield reductions in some treatments were attributable to reduced weight per kernel. Significant correlations were found between the mass‐flow sensors and grain yield and CWSI. The relationship between grain yield and stomatal conductance was consistent over both years, suggesting that the cumulative mean conductance may be useful as a yield predictor.
Detoxification and Evaluation of Foam Supports for Aeroponically Grown Soybean
Authors: Wagner R. E. , Wilkinson H. T.
Published: July 2010

Polyurethane‐based foam plugs used as supports for aeroponically grown soybean plants [Glycine mu (L.) Merr.] contain a phytotoxic compound. Plugs were detoxified after soaking in 1.0 M NaOH for 1 h and then in 950 mL L−1 ethanol for 12 h. Five additional foam materials were evaluated as substitutes for polyurethane foam plugs. Four of the five foams tested (reticulated ether‐based foam, etbafoam, Dowstrand foam, and L/C 200 foam) were nontoxic to soybean plants. Of these, reticulated ether‐based foam (39.4 or 31.4 pores cm−l) had physical properties similar to polyurethane foam and is recommended as a substitute for this material.
Recurrent Mass Selection Based on Selfed‐Plant Evaluation in Allogamous Species
Authors: Dhillon B. S.
Published: July 2010

Plant breeders need to develop methods having higher genetic gains than those available. The objective of this study is to propose recurrent selfed‐plant mass (SPM) selection, derive its expected genetic gain (ΔGS), and to compare ΔGS with that of mass selection (ΔGM). In SPM selection, S1 plants are evaluated and recombined, and a cycle is completed in a year if an off‐season nursery is available. The ΔGS per cycle was 18 to 34% higher than ΔGM for degree of dominance ranging from none to complete dominance and the frequency of favourable alleles from low to intermediate (0.1–0.5). The SPM selection has another advantage, in that deleterious recessive alleles are exposed.
Genotypic Variation for Cold Tolerance in Winter and Facultative Barley
Authors: Kolar S. C. , Hayes P. M. , Chen T. H. H. , Linderman R. G.
Published: July 2010

Improved winter survival of barley (Hordeum vulgare L.) may be achieved by developing genotypes that maintain an acceptable level of cold tolerance despite fluctuations in air and soil temperature. The cold tolerance of eight winter and facultative barley cultivars, a spring barley and a winter wheat (Triticum aestivum L.) was measured in controlled freeze tests of field‐grown material. The temperature lethal to 50% of each genotype population (LT50) was calculated from survival data. The LT50 values for each genotype were determined at multiple sampling dates at two locations over a 2‐yr period. Sampling dates were considered environments and these data were used to identify genotypes showing stable, or full‐season, cold tolerance. Genotypes were grouped according to patterns of comparable LT50 response across the six environments. The significant genotype group ✕ environment interaction detected in the analysis of groups and environments was due to changes in magnitude of response rather than changes of rank. Averaged across all environments. ‘Norstar’ winter wheat was significantly more cold tolerant than the barley germplasm, and there was little variation for cold tolerance among winter barley genotypes. Winter barley cultivars were more cold tolerant than facultative cultivars. Two joint regression stability parameters, the regression coefficient (b) and squared deviations from regression (S2d), revealed genotypic variation for full‐season cold tolerance.
Ontogenetic Approach to Grain Production in Spring Barley Based on Path‐Coefficient Analysis
Authors: García del Moral L. F. , Ramos J. M. , García del Moral M. B. , Jiménez‐Tejada M. P.
Published: July 2010

Grain yield of barley (Hordeum vulgare L.) is influenced by several yield components and also by the duration of the vegetative and grain‐filling periods. Path‐coefficient analyses, based on an ontogenetic diagram, were conducted to study the relationships among grain yield, yield components, and duration of the vegetative and grain‐filling periods. Nine genotypes (including seven near‐isogenic lines) of spring barley varying in heading dates and several morphological traits were grown during the 1987 and 1988 seasons in two environments in the province of Granada in southern Spain. Grain‐yield variations between environments and from year to year depended mainly on two yield components, the number of spikes per square meter and the number of kernels per spike. The average kernel weight had a negligible effect on grain yield. The number of spikes per square meter had a considerable negative influence on kernels per spike but contributed positively to both the length of the grain‐filling period and the average kernel weight. The duration of the vegetative period had a positive influence on the kernels per spike and a negative influence on the length of the grain‐filling period. A lengthening of the grain‐filling period induced an increase in kernels per spike but did not significantly modify the average kernel weight. The path diagram also indicated that variations in the kernels per spike do not significantly influence kernel weight.
Quantification of Abscisic Acid in Wheat Leaf Tissue by Direct Enzyme Immunoassay
Authors: Tahara Makoto , Guenzi Arron C. , Read John J. , Carver Brett F. , Johnson Richard C.
Published: July 2010

The plant growth hormone abscisic acid (ABA) modulates plant responses and adaptations to environmental stress. The objective of this study was to develop a procedure which would facilitate broad‐scale screening of wheat (Triticum aestivum L. em. Thell.) germplasm in which ABA content or rate of accumulation in leaf tissue is the selection criterion. The effects of extraction time, C18 reverse‐phase chromatography, solvent volatilization, and dilution of sample extract on quantification of ABA by direct enzyme immunoassay (EIA) were investigated. Results showed that complete volatilization of extraction solvent did not affect ABA determination. Extraction of ABA from wheat leaves, using 800 mL L−1 methanol (MeOH), was complete after 24 h. Interference to EIA due to MeOH was eliminated when MeOH was diluted to ≤80 mL L−1. No apparent inhibitors to EIA were detected by a parallelism test of dilution curves or by partial purification of leaf extract using C18 reverse‐phase chromatography. Simplified and effective procedures are proposed which facilitate the preparation of a large number of leaf samples at minimal expense and labor without sacrificing accuracy of ABA estimation.
Maize Kernel Set at Low Water Potential: II. Sensitivity to Reduced Assimilates at Pollination
Authors: Schussler J. R. , Westgate M. E.
Published: July 2010

Plant water deficits at pollination decrease kernel set in maize. An important component of this kernel loss is developmental failure after fertilization. This study was undertaken to determine if zygotic abortion in water‐deficient plants results primarily from a decrease in assimilate supply daring the critical period around pollination. Plants were grown in soil/sand media in a controlled environment, and photosynthesis was inhibited by water‐deficit or low‐light treatments. Plants were hand‐pollinated when silk water potential of control, low‐light, and water‐deficient plants was −0.4, −0.4, and −1.0 MPa, respectively. Corresponding leaf water potentials were −0.3, −0.3, and −1.7 MPa. The water deficit decreased ovary water potential, osmotic potential, and turgor by 0.6, 0.3, and 0.3 MPa, respectively, compared with values in well‐watered plants. Treatments were terminated 2 d after pollination, and leaf photosynthesis recovered to control values within 24 h. Kernel numbers per ear were 598 ± 17 for control, 222 ± 72 for low light, and 15 ± 6 for water‐deficit treatments. The brief inhibition of photosynthesis had little impact on C and N accumulation in vegetative sinks, but severely reduced assimilate movement to reproductive sinks. At pollination, concentrations (mg g−1 dry wt.) of fructose, glucose, and sucrose in ovaries were similar for all treatments. The high levels of these soluble sugars in both setting and aborting ovaries suggests that kernel set depends on the rate of movement of assimilates into the ovaries, rather than the concentration of soluble sugars per se. Sucrose uptake by isolated ovaries was inhibited at low water potential, suggesting a direct effect of ovary water status on kernel development. The nearly complete kernel loss observed in the water‐deficit plants indicates that low ovary water potential at pollination decreased kernel set beyond that which can be attributed to reduced assimilate supplies alone.
Carbon Dioxide Effects on Potato Growth under Different Photoperiods and Irradiance
Authors: Wheeler Raymond M. , Tibbitts Theodore W. , Fitzpatrick Ann H.
Published: July 2010

Carbon dioxide concentration can exert a strong influence on plant growth, but this influence can vary depending on irradiance. To study this, potato plants (Solanum tuberosum L.) cultivars ‘Norland’, ‘Russet Burbank’, and ‘Denali’ were grown in controlled‐environment rooms at different levels of CO2 and irradiance. Carbon dioxide levels were maintained either at 350 or 1000 μmol mo1−1 and applied in combination with 12‐ or 24‐h photoperieds at 400 or 800 μmol m−2 s−1 photosynthetic photon flux. Air temperatures and relative humidity were held constant at 16 °C and 70%, respectively, and plants were harvested 90 d after planting. When averaged across all cultivars, CO2 enrichment increased tuber yield and total plant dry weight by 39 and 34%, respectively, under a 12‐h photoperied at 400 μmol m−2 s−1; 27 and 19% under 12 h at 800 μmol m−2 s−1; 9 and 9% under 24 h at 400 μmol m−2 s−1. It decreased dry weights by 9 and 9% under 24 h at 800 μmol m−2 s−1. Tuber yield of Denali showed the greatest increase (21%) in response to increased CO2 across all irradiance treatments, while tuber yields of Russet Bur‐bank and Norland were increased 18 and 9%, respectively. The results show a pattern of greater plant growth from CO2 enrichment under lower PPF and a short photoperiod.
Partitioning of Biomass in Well‐Watered and Water‐Stressed Cotton Plants Treated with Mepiquat Chloride
Authors: Fernández C. J. , Cothren J. T. , McInnes K. J.
Published: July 2010

Most of the research investigating the effect of mepiquat chloride (1,1‐dimethylpiperidinium chloride) on the growth of cotton (Gossypium hirsutum L.) has been limited to well‐irrigated plants and has been focused primarily on the growth of aboveground organs. This study was conducted to evaluate the effect of mepiquat chloride (MC) on the partitioning of biomass in whole cotton plants grown in controlled‐environment test chambers under well‐irrigated and water‐deficient conditions. Single plants of ‘Stoneville 825’ were transferred from a nursery room into test chambers when they reached a leaf area of ≈500 cm2 and were then exposed to the following treatments: (i) sprayed at a recommended rate for commercial crops with 12 ± 1 mL plant−1 of a MC solution (27.3 mg L−1 a.i.) and maintained well irrigated, (ii) not sprayed with MC and maintained well irrigated, (iii) sprayed with MC and not irrigated, and (iv) not sprayed with MC and not irrigated. Durations of experiments varied from 11 to 14 d. Tests were replicated four times. Environmental conditions in the test chambers were typical of sunny and humid summer days in central Texas. Leaf area was measured daily during the tests. At the end of each test, the plants were harvested and separated into various categories of plant organs, oven‐dried and weighed. Water deficits inhibited the accumulation of plant biomass through inhibition of leaf lamina, petiole, and branch growth. The MC, on the other hand, did not affect the accumulation of biomass on a whole‐plant basis, but did affect biomass partitioning by inhibiting growth of branches and stem and by promoting growth of fine roots; MC also inhibited expansion of leaves and extension of stem internodes and petioles, which led to the development of a more compact canopy structure. These effects of MC on biomass partitioning and size of plant organs may result in decreased plant photosynthesis rates, but also may induce a water‐conservative behavior.