bluuebunny/crossref_metadata_2025 huggingface dataset:
Kernel Distributions in Main Spikes of Salt‐Stressed Wheat: A Probabilistic Modeling Approach
Authors: Lesch Scott M. , Grieve Catherine M. , Maas Eugene V. , Francois Leland E.
Published: July 2010

Grain development in wheat (Triticum aestivum L.) is a complex process that responds to interactions among primary genotypic factors and the environment. This study was conducted to determine the effects of salinity stress on kernel occurrence and kernel mass distributions within the main spike. Mexican semidwarf wheat cuitivars Yecora Rojo and Anza were grown in sand tanks in the greenhouse with saline and nonsaline nutrient solutions. At harvest, each spikelet position and grain position was identified and the weight of every kernel was determined. Hierarchical multiple linear regression models were derived and fit to the kernel mass patterns. In a similar manner, logistic regression models were derived and fit to the kernel occurrence patterns. Kernel mass was shown to be highly dependent on spikelet location long the spike, kernel position within the spikelet, and salinity stress. Results from the logistic regression models confirm that these same factors affect kernel occurrence. Both types of statistical analysis are advantageous, since the changes in kernel occurrence and kernel mass distributions due to each of the above factors can be easily detected and studied.
Light Interception and Lint Yield of Narrow‐Row Cotton
Authors: Heitholt James J. , Pettigrew William T. , Meredith William R.
Published: July 2010

Narrow row spacings in crops can potentially increase total seasonal light energy interception. Our objective was to determine the effects of a combination of row spacing with different genotypes on light interception and yield of upland cotton (Gossypium hirsutum L.). In 1989 and 1990, an okra‐leaf genotype and its normal‐leaf isoline were grown in the field, using 0.5‐m (narrow) and 1.0‐m (wide) row spacings in early and late plantings each year. The photosynthetic photon flux density (PPFD) intercepted by the canopy was determined weekly and insolation interception calculated. Aboveground dry matter accumulation and leaf area were determined at five intervals throughout the season. Open bolls were counted, harvested, and their lint yield determined. Narrow row spacing increased seasonal insolation interception in both leaf types. Narrow rows increased the yield of the okra leaf over that of wide rows in both plantings in 1989 and for the late planting in 1990. Yield of the normal leaf was reduced by narrow rows in one environment, but not significantly affected by row spacing in three other environments. For okra leaf planted early or late and for the normal leaf planted late, variation in lint yield was strongly correlated with total seasonal insolation intercepted. The yield increase of the okra leaf grown in narrow rows was a result of an increase in the number of mature fruit produced per unit ground area and not an increase in fruit size. Narrow rows increased the efficiency of PPFD interception by a given leaf area. The use of narrow‐row culture for the okra‐leaf type provides an opportunity for overcoming its low leaf area, increasing its insolation interception, and increasing its lint yield.
Modification of Tiller Productivity in Spring Barley by Application of Chlormequat or Ethephon
Authors: Ma B. L. , Smith Donald L.
Published: July 2010

Application of plant growth regulators (PGR) to control lodging in cereal crops often increases the number of tillers and/or spikes. It is not clear whether the increment in spike numbers is due to enhanced tiller production or to an increased percentage of tiller spikes. The objective of this study was to evaluate the timing of chlormequat (2‐ chloroethyl‐N,N,N‐trimethylammonium chloride) (CCC) or ethephon (2‐chloroethyl phosphonic acid) application on tiller production and subsequent tiller growth and development in spring barley (Hordeum vulgare L.). A 3‐yr field study with two widely grown cultivars, Leger and Cadette, was conducted on Bearbrook clay soil (fine, mixed, nonacid Mesic Humaquept) at the Emile A. Lods Agronomy Research Center, McGill University, Canada, from 1988 to 1990. Treatments consisted of CCC (1.2 kg a.i. ha−1) or ethephon (0.48 kg a.i. ha−1) applied at Zadoks growth stages (ZGS) 13,30, or 39. Tiller production was monitored at ZGS 12,32,51, and 90. Plants treated with an early application of CCC (ZGS 13 or ZGS 30) or ethephon (ZGS 30) produced greater numbers of shoots, appearing later in time, than control plants. Early PGR treatment increased the number of spike‐bearing shoots, primarily by enhancement of tiller number (tiller‐derived spikes) rather than the spike production rate (tiller survival). Late application of CCC or ethephon at ZGS 39, when most of the tillers had emerged, resulted in a higher number of spike‐bearing shoots, mostly through the increased percentage of tiller spikes.
Adaptive Attributes of Cowpea Genotypes with Delayed Monocarpic Leaf Senescence
Authors: Gwathmey C. Owen , Hall Anthony E. , Madore Monica A.
Published: July 2010

In annual grain legumes, monocarpic senescence results in the loss of functional leaf area during pod production, which may limit the availability of fixed C to support seed filling. Genetically delayed leaf senescence (DLS) may enhance the seed yield potential of cowpea (Vigna unguiculata (L.) Walp.] by alleviating this deficiency and by increasing crop longevity. Senescence characteristics, temporal distribution of reproductive activity, and seed yields of contrasting cowpea genotypes were compared in three seasons of field experiments at Riverside, CA, and their carbohydrate reserves were monitored during one season. While senescent genotypes exhibited a typically monomodal reproductive distribution, DLS genotypes consistently produced two sets of pods. During the first podset, DLS genotypes had a lower rate of leaf senescence per unit of seed fill than did senescent genotypes, but tended to produce slightly lower first‐podset seed yields. More residual green leaf area and greater plant viability were maintained in stands of DLS genotypes, which led to production of a substantial second podset. Total seed yields were higher from DLS than from senescent genotypes under full‐season conditions. During the first podset, nonstructural carbohydrates were depleted from stems of senescent plants, while starch and sucrose accumulated in stems of DLS plants. The timing and extent of reproductive cutout from the first podset were similar in senescent and DLS genotypes, despite the perennialistic growth pattern of DLS plants. The delayed leaf senescence traits expressed in these experiments may enhance adaptation to variable‐ or long‐season conditions, and to cropping systems in which multiple harvests of mature pods are practiced.
Responses and Ramifications of Rice Canopy Leaf Stratification
Authors: Counce Paul A.
Published: July 2010

Leaf area within the crop canopy is treated, in various models of canopy processes, as if it were uniform. Crop canopies may, however, be nonuniform in vertical leaf area distribution. Nonuniform vertical leaf area distribution would be expected to affect the responses of rice (Oryza sativa L.) grain yield to leaf area index (LAI). measure of vertical leaf area distribution is proposed: canopy stratification index (CSI) which is the ratio of leaf area in the upper vertical half of the canopy that lower halves. My objectives were to examine (i) the CSI resopnses to rice cultivar, seeding rate, N fertilization rate, and year, and (ii) the relationships of grain yield to LAI for three rice cultivars. A 3.yr field study with three N rates (0, 100, and 200 kg ha−1), three seeding rates (100, 300, and 500 seeds m−2), and three cultivars provided the data to examine the questions posed. ‘Lebonnet’ and ‘Le. mont’ rice had higher CSI then did ‘Newbonnet’. There was a parabolic response of grain yield to LAI, with the linear grain yield response phase to LAI being greater for Newbonnet than for Lebonnet, and intermediate between Newbonnet and Lebonnet for Lemont. Optimum LAI was less for Newbonnet than for Lemont and Lebonnet. Therefore, among these cuitivars the grain yield response to LAI was more positive in the linear phase and the optimum LAI for grain yield was lower for the cultivar with the lowest CSI. These data suggest CSI may have value as a selection criterion for yield rice lines by plant breeders.
Seeding Date, Carbofuran, and Resistance to Root‐Lesion Nematode Affect Alfalfa Stand Establishment
Authors: Thies Judy A. , Barnes Donald K. , Rabas David L. , Sheaffer Craig C. , Wilcoxson Roy D.
Published: July 2010

The root‐lesion nematode, Pratylenchus penetrans (Cobb) Filipjev & Schuurmans Stekhoven, can reduce the establishment and productivity of alfalfa (Medicago sativa L.) in the northeastern and north‐central USA and in eastern Canada. Our objectives were to evaluate the effects of fallow and delayed seeding date, carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate) treatment, and plant resistance on P. penetrans populations in alfalfa roots and on alfalfa stand establishment and plant growth. In 1982,1983, and 1984, alfalfa genotypes varying in reaction to P. penetrans (‘Baker’, susceptible; ‘WL‐219’, low resistance; and MNGRN‐2 and MNGRN‐4, both with moderate resistance) were established in a Cowhorn sand (coarse‐loamy, mixed, nonacid frigid Aerie Haplaquept), naturally infested with high populations of P. penetrans. The alfalfa genotypes were seeded on different dates from 13 May to 14 July with and without soil applications of carbofuran at 2.2 kg a.i. ha−1. Plant stands were greatest and nematode populations were smallest when plots were seeded in late June or early July after 7 wk of fallow. Carbofuran application at seeding increased alfalfa stand establishment (21%) and reduced P. penetrans populations within alfalfa roots (37%) for ≈6 wk. Moderate resistance to P. penetrans in MNGRN‐4 increased alfalfa stand establishment (34%) and yield (22%) and reduced root‐lesion nematode populations within alfalfa roots (37%). Pratylenchus penetrans can be controlled in alfalfa during the establishment year by a combination of fallow and delayed seeding, use of carbofuran at establishment, and resistant cultivars.
Irrigation of Soybean Cultivars Susceptible and Resistant to Soybean Cyst Nematode
Authors: Heatherly Larry G. , Pringle H. C. , Sciumbato Gabriel L. , Young Lawrence D. , Ebelhar M. Wayne , Wesley Richard A. , Tupper Gordon R.
Published: July 2010

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) infests soils throughout the mid and lower Mississippi River Valley and the southeastern Coastal Plain in the USA, a region where irrigation is widely practiced. This study was conducted to determine the effect of irrigation on number of SCN cysts and seed yield of three soybean [Glycine max (L.) Merr.] cultivars that have varying levels of SCN resistance when grown in monoculture on SCN‐infested Dundee silt loam (fine‐silty, mixed, thermic, Aerie Ochraqualf) that has a perched water table. Cultivars (all Maturity Group V) were Forrest (resistant to SCN Race 3), A5474 (resistant to SCN Races 3 and 4), and Bay (susceptible to SCN). Bay was grown with and without nematicide applied after planting. Irrigation treatment was either with or without supplemental water during reproductive development of soybean. Neither seed yield nor number of SCN cysts at planting or harvest were significantly (P = 0.05) affected by irrigation on this soil. Application of nematicide to Bay plots reduced the number of SCN cysts at harvest, but did not significantly affect seed yield. Number of SCN cysts was lowest in A5474 plots, and seed yield of A5474 was highest in the second and third year of the study. Irrigation did not significantly interact with cultivar or nematicide to affect cyst number or seed yield. We conclude that irrigation during reproductive development of soybean did not affect (i) cultivar response to infection with SCN, (ii) the capability of SCN to maintain cysts on any cultivar, or (iii) the yield‐limiting effect of SCN on susceptible cultivars. This suggests that SCN effects on soybean are more complex than simply restricting water uptake by roots.
Digestion Kinetics of Parenchyma and Sclerenchyma Cell Walls Isolated from Orchardgrass and Switchgrass
Authors: Grabber John H. , Jung Gerald A. , Abrams Stephen M. , Howard Diantha B.
Published: July 2010

Both cell‐wall chemistry and anatomical structure determine the digestion characteristics of cell types in forages. The objectives of this study were to determine the digestion kinetics of cell types apart from anatomical factors, and to relate these digestion kinetics to previously determined cell‐wall constituents. Parenchyma and sclerenchyma cell walls, isolated from plant parts of orchardgrass (Dactylis glomerata L.) and switchgrass (Panicum virgatum L.) at four growth stages, were milled (digestion >150 µm) and incubated in buffered rumen fluid for 0 to 96 h. Lag time (L) of cell types ranged from 4.0 to 8.0 h, rate constant (k) from 0.035 to 0.100 h−1, and indigestible residue (IR) from 89 to 595 g kg−1. Differences between L of cell types were small. The k of parenchyma was ≈50% greater (P < 0.01) than that of sclerenchyma. The concentration of IR increased (P < 0.05) during plant maturation, particularly for stem cell types. The IR of orchardgrass parenchyma was less (P < 0.01) than that of sclerenchyma at immature growth stages, but not at late anthesis. In contrast, IR of switchgrass parenchyma was greater (P < 0.01) than that of sclerenchyma. Among cell types, IR concentrations were lowest (P < 0.05) for leaf sheath parenchyma and leaf blade sclerenchyma. The L and k of both cell types and IR of sclerenchyma were poorly correlated to neutral sugar, esterified phenolic acid, and lignin concentrations. The IR concentration of parenchyma was correlated (P < 0.01) with most cell‐wall constituents, suggesting that fiber digestibility could be improved by altering the cell‐wall composition of this cell type. The rate and extent of digestion of sclerenchyma was much greater than reported from histological studies, suggesting that the anatomical configuration of this cell type, rather than its cell‐wall composition, is the major factor limiting its digestion.
Rapid Screening Techniques for Lipoxygenases in Soybean Seeds
Authors: Hammond Earl G. , Duvick Daniel N. , Fehr Walter R. , Hildebrand David F. , Lacefield Eugene C. , Pfeiffer Todd W.
Published: July 2010

Soybean [Glycine max] breeders are developing cultivars that lack one or more lipoxygenase enzymes for use in certain food products, but electrophoresis for screening lipoxygenase phenotypes in a large segregating population is expensive and time‐consuming. Rapid procedures were developed to screen seeds for lipoxygenase‐1, ‐2, and ‐3, based on the ability of these enzymes at the surface of cut or broken seed to form hydroperoxides when exposed to emulsions containing linoleate or linolenate. The peroxides are detected by a color test based on the oxidation of iodide‐starch for lipoxygenase‐I or of ferrous thiocyanate for lipoxygenase‐2 and ‐3. The test for lipoxygenase‐3 is valid only in the absence of lipoxygenase‐2; all other combinations of lipoxygenases can be tested. For more than a few samples, the new procedures are generally more rapid, convenient, and less costly than electrophoresis and do not require special equipment.
Changes in mRNA Species during Drought Stress in Winter Wheat
Authors: King Steven W. , Verling Richard A. , Nguyen Henry T.
Published: July 2010

Drought stress is a major factor limiting wheat (Triticum aestivum L.) production in arid and semiarid regions. Our objective was to characterize changes occurring at the molecular level in response to drought stress. TAM W‐101 wheat was chosen for these studies since it has been previously reported to be drought tolerant in the U.S. Southern Great Plains. Two‐dimensional gel electrophoresis of translation products of RNA isolated from control and stressed leaves and roots revealed numerous polypeptides that had qualitative and quantitative changes following drought stress. Northern blot analysis of RNA showed large increases in rab (responsive to ABA) transcripts during drought stress. Both the in vitro translation and northern blot studies indicate that there is a molecular drought stress response in wheat leaves and roots.
Heterosis and Combining Ability of CIMMYT's Subtropical and Temperate Early‐Maturity Maize Germplasm
Authors: Vasal Surinder K. , Srinivasan Ganesan , Crossa José , Beck David L.
Published: July 2010

Knowledge about the combining ability and heterotic patterns among CIMMYT's maize (Zea mays L.) germplasm is essential for hybrid development work at CIMMYT, as well as at other national research programs using CIMMYT germplasm. This study was conducted to determine the heterosis and combining ability among CIMMYT's subtropical and temperate early‐maturity maize germplasm. A seven parent diallel involving two populations and five gene pools was made. The parents and 21 crosses were evaluated in 17 temperate and 5 subtropical environments during 1985‐1986. Average yield across temperate environments (4.35 Mg ha−1) was comparable to that obtained in subtropical environments (4.59 Mg ha−l). Highest yield subtropical environments was recorded by Population 48 × Pool 27 (5.42 Mg ha−1), with a high‐parent heterosis of 9.9%. Maximum high parent heterosis was observed in Population 46 × Pool 30 (13%), which yielded 5.17 Mg ha−1. Under temperate environments, the highest‐yielding combinations included Population 48 crossed with Population 46 and Pools 27, 28, and 30, although magnum heterosis (10.2%) was recorded for Pool 27 × Pool 40. General combining ability (GCA) effects for yield were significant in both sets of environments, while specific combining ability (SCA) effects were significant only in temperate environments. Highly significant positive GCA effects for yield were observed with Population 48 (0.43 Mg ha−1) and Pool 30 (0.33 Mg ha−1) under temperate conditions. Pools 40 and 42 were poor general combiners in both sets of environments. Significant positive SCA effects for yield were observed with Population 46 × Population 48 and Population 46 × Pool 30 crosses in temperate environments and the Population 48 × Pool 27 cross under subtropical environments. Population 48 and Pool 30 may hold potential for use as source germplasm for both temperate and subtropical maize breeding programs.
Genes for Rust Resistance in International Winter Wheat Nurseries XII through XVII
Authors: McVey Donald V.
Published: July 2010

Genes for resistance to stem rust (Sr) (caused by Puccinia graminis Pers.:Pers. f. sp. tritici) and leaf rust (Lr) (P. recondita Roberge ex. Desmaz f. sp. tritici) were detected in cultivars of wheat (Triticum aestivum L.) of the International Winter Wheat Performance Nursery XII through XVII. The objectives were to test for the presence and distribution of Sr and Lr genes. Entries were inoculated with 28 isolates of P. graminis f. sp. tritici and 15 isolates of P. recondita f. sp. tritici, previously characterized for avirulenceJvirulenee to 26 Sr an 14 Lr genes, respectively. Sixteen of the 26 Sr genes and six of the 14 Lr genes were postulated as present. A few cultivars possessed a gene or genes for resistance other than those studied. No Sr genes for resistance were detected in three cultivars, a single gene was detected in each of 32 cultivars, two in 32, three in 13, and four Sr genes in two cultivars. Genes for stem rust resistance Sr5, SrMcN, Srl7 Sr31, and SrlO were most commonly postulated, whereas Sr7b, Sr9d, Sr9e, Srl2, Srl3, Srl4, Srl5, Srl6, Sr25, Sr26, and Sr27 were not detected in any of the entries. No Lr genes for resistance were detected in 27 cultivars, one in each of 40, two genes each in 14, and three genes in each of two cultivars. Genes for leaf rust resistance LrlO and Lr26 were most commonly postulated, whereas Lr21, Lr2c, Lr3ka, Lr9, Lrl7, LrlS, Lrl9, and Lr30 were not detected.
Modified Seed Maturation Rates and Seed Yield Potentials in Soybean
Authors: Hanson W. D.
Published: July 2010

Seed embryos of soybean [Glycine max (L.) Men‐.] genotypes can have different levels of specific dry matter accumulation rate (SDMAR) and specific seed density (SSD) under greenhouse growing conditions, but the relevance of these measures for field‐grown plants is not known. The objectives of this research were to interrelate these measures as they reflect characteristics of the developing soybean seed and to determine their association with seed‐yield potential. As the seed matured, SSD increased ⊄0.01 g cm−3 d−1. Differences in this rate of change were positively associated with SDMAR. Genotypes selected for increased, as compared with decreased, seed‐filling duration had lower SDMAR and lower rate of change in SSD (decreased seed maturation rate) and greater seed yield under favorable field conditions. However, the yield advantage was lost under environments having drought stress during the reproductive period. Selections for high seed protein content exhibited an apparent increased seed‐maturation rate and a reduced seed yield. Divergent selection for SSD produced major shifts in SSD at the 55% seed‐filling stage. In contrast, the modified reproductive period selections and the seed protein selections had only secondary differences for SSD at that seed‐filling stage, indicating that the low SSD selections initiated delayed seed maturation at an earlier stage of seed development. While the low SSD selections had the reduced seed‐maturation rates, they did not express the expected yield advantage. Under drought stress, they exhibited lower seed number and seed yield than the modified reproductive period and high SSD selections. The stage of maturity for initiating delayed maturation appeared important. The proposed desirable genotype maintained specific dry matter accumulation rate during early seed fill but shifted to reduced seed maturation rate at a later stage of seed development.
Section for Low Ear Moisture in Corn, Using a Hand‐Held Meter
Authors: Freppon Jeffrey T. , St. Martin Steven K. , Pratt Richard C. , Henderlong Paul R.
Published: July 2010

A rapid, effective method for identifying inbred lines of corn (Zea mays L.) that produce hybrids with a low grain‐moisture content at harvest would be helpful to corn breeders. We evaluated use of a hand‐held moisture meter to select for low ear‐moisture content in a set of St plants that had similar pollination dates. A set of 30 lines, derived from plants classified as low‐, medium‐, and high‐moisture 30 d after pollination, was identified. The lines were evaluated for moisture content in a randomized complete‐block experiment. Testcrosses of the lines to two testers were evaluated for yield and harvest moisture at five locations in 1 yr. The moisture meter produced estimates of moisture content that correlated well in 2 yr (r2 = 0.85 and 0.82) with estimates obtained by the oven method. Lines derived from ears selected for low moisture with the meter had lower moisture at harvest than lines from high‐moisture ears. Hybrids of low‐moisture lines were lower in harvest moisture than hybrids of high‐moisture lines but were similar in grain yield. The moisture meter should enable corn breeders to select for low harvest moisture in segregating populations.
Dinitrogen Fixation, Nitrogen and Dry Matter Accumulation, and Nodulation in White Lupine
Authors: Ayisi Kingsley K. , Putnam Daniel H. , Vance Carroll P. , Graham Peter H.
Published: July 2010

Timing of N uptake and N2 fixation may be important determinants of yield and seed N concentration in spring sown white lupine (lupinus albus L.). This study was initiated to determine N2 fixation, N and dry matter (DM) accumulation and distribution patterns, and nodulation as influenced by Bradyrhizobium sp. (lupinus) inoculation and N fertilizer. Inoculum strains WU425 and 96B15 were combined in a 1:1 cell ratio in inoculated plots and compared with noninoculated controls at 0, 56, 112, and 168 kg N ha−1 under irrigation on a loamy sand (Udorthentic Haploboroll) in 1989 and 1990. Control plots were maintained nodule.free. Bradyrhizobium strains persisted in this environment, and applied strains nodulated the tap root primarily. Increased total DM and N yield due to inoculation was first observed 42 days after emergence (DAE), and by 84 DAE, was more than twofold that of uninoculated 0‐N controls in both years. Dinitrogen fixation, estimated by the difference method, was insignificant before flowering but totalled 157 kg N ha−1 and 196 kg N ha−1 by 84 DAE in 1989 and 1990, respectively. Inoculation or N fertilizer did not influence distribution of dry matter among plant parts. Previously observed enhancement of seed protein concentration due to inoculation was probably due to increased total plant N supply late in the season, not to more efficient mobilization of N to seed in inoculated plants. Supplemental N fertilizer suppressed nodulation and N2 fixation and did not improve early growth. These results indicate that spring‐planted white lupine in effective symbiosis with bradyrhizobia are not normally N‐limited at any time during growth under most conditions.
Ultraviolet‐B Radiation Effects on Growth and Physiology of Four Rice Cultivars
Authors: Dai Qiujie , Coronel Victoria P. , Vergara Benito S. , Barnes Paul W. , Quintos Arlene T.
Published: July 2010

Enhanced ultraviolet‐B (UV‐B, 280–320 nm) radiation, such as could be caused by stratospheric O, depletion, has been demonstrated to profoundly affect plants. This study was conducted to determine the effects of UV‐B on four high‐yielding, lowland rice (Oryza sativa L.) cultivars (IR30, IR45, IR64, and IR74), and to evaluate morphological and physiological parameters for identifying sensitive and less‐sensitive genotypes in future screenings. Ultraviolet‐B radiation was supplied by UV‐B–emitting fluorescent lamps in the phytotron. Plant height, leaf area, dry weight, net assimilation rate (NAR), and relative growth rate (RGR) were significantly influenced by 4‐wk UV‐B treatment in some cultivars. Based on the relative change in total biomass production between UV‐B‐irradiated and control plants, cultivar IR74 was the most sensitive and cultivar IR64 the least sensitive. Biomass production, however, did not proportionally decrease with plant height under UV‐B treatment. Changes in plant height and leaf area induced by UV‐B can alter the rice plant canopy structure. Differential varietal response was found in shoot dry weight, leaf area, specific leaf weight (SLW), NAR, and RGR. These parameters can be used as selection criteria for rice cultivars less sensitive to UV‐B. Most physiological and biochemical parameters evaluated, including root‐oxidizing activity, soluble protein, nucleic acid, ion leakage, stomatal aperture, and flavonoid and chlorophyll contents, were affected by 2 wk of UV‐B treatment and gave differential cultivar responses. The distinct responses and relative ease in measurement of stomatal opening and ion leakage make these parameters suitable indices in selecting rice cultivars less sensitive to UV‐B after 2 wk of UV‐B treatment.
Relative Date of Wheat Seedling Emergence and Its Impact on Grain Yield
Authors: Gan Yantai , Stobbe Elmer H. , Moes Jack
Published: July 2010

Emergence of wheat (Triticum aestivum L.) seedlings usually occurs over a period of several days, resulting in nonuniformity among neighboring plants. The impact of nonuniformity in time of emergence on grain yield has not been determined. We determined effect of planting depth on relative date of seedling emergence, and of relative date of emergence on grain‐bearing tillers and grain yield per plant. Large seed (39.8 ± 4.59 mg kernel−1) in 1989, and large (41.7 ± 3.83 mg kernel−1) and small seeds (24.3 ± 4.56 mg kernel−1) in 1990 were obtained from ‘Roblin’ wheat. Seeds were hand.planted at 25‐, 50‐, and 75‐mm depths on Neuborst clay loam (fine‐loamy, frigid, Aquic Haploborolls) at Portage la Prairie, MB. Plants were tagged the day they emerged, and individual plant yield was determined at harvest. Planting depths did not differ for total percent emergence in 1989, but in 1990, increasing planting depth led to decreased total emergence. Gompertz growth model predictions of inflection time, maximum emergence rate, and cumulative percent emergence indicated that seedling emergence rate decreased as planting depth increased, and the decrease was greater with small seed than with large seed. The first date on which seedlings emerged each year was designated as Day 1. Averaged across 2 yr, plants that emerged on Day 1 to 3 produced 1.4 times the yield of those emerged on Day 4 to 6, and 3.2 times the yield of those emerged on Day 7 to 9. Reduced yield of late emerged plants was due primarily to fewer grain‐bearing tillers. This research demonstrates the benefit of shallow placement of large seeds in minimizing variation in time of seedling emergence among plants, and increasing grain yield.
Meadowfoam Seed Yield Response to Temperature during Flower Development
Authors: Franz Robert E. , Seddigh Majid , Jolliff Gary D. , Alba Elena L.
Published: July 2010

Variation in meadowfoam (Limnanthes alba Hartw. ex Benth. subsp. alba cv. Mermaid) seed yield has resulted in unpredictable economic returns and limited the area of production of this new oilseed crop. A controlled‐environment experiment was conducted to evaluate the effects of a 7‐d period of 16/10, 24/10 and 32/10 °C day/night temperature regimes imposed during floral bud development or peak bloom stages on seed set and seed yield. Thirty hand‐pollinated flowers were used to determine mean seed set per flower, weight per seed, and seed weight per plant. Increasing temperature from 16/10 to 32/10 °C during bud development did not affect seeds per flower, increased (P = 0.04) weight per seed, and increased (P = 0.04) seed weight per plant. Increasing temperature from 16/10 to 32/10 °C at peak bloom decreased (P = 0.02) seeds per flower, did not affect weight per seed, and decreased (P = 0.03) seed weight per plant. It was concluded that higher day temperatures (≤32 °C) during bud development, and lower day temperatures (≈16 °C) during flowering and early seed formation, would favor seed production in Mermaid meadowfoam.
Night Temperature Affects Radiation‐Use Efficiency in Peanut
Authors: Bell M.J. , Wright G.C. , Hammer G.L.
Published: July 2010

Three peanut (Arachis hypogaea L.) cultivars were grown under optimal field conditions in two environments in subtropical Australia contrasting primarily in night temperature. Mean minimum temperatures during the growing season were 16.7 °C (Kingaroy, cool) and 20.1 °C (Bundaberg, warm). Dry matter production was similar in both environments, but pod yields were slightly higher with warm nights (P < 0.05). This occurred despite large differences in rates of development between environments, with plants of all cultivars in the warm night environment maturing 23 to 24 d earlier. Accumulation of energy‐corrected dry matter was highly correlated with cumulative intercepted shortwave solar radiation. There were no significant differences among cultivars in the rate of accumulation of energy‐corrected dry matter per unit of intercepted shortwave radiation (radiation‐use efficiency; RUE, g MJ−1) in either environment. Data were pooled within environments, with RUE in the warm environment 39% higher than with cool nights. This higher RUE in the warm nights occurred despite poorer radiation distribution within the canopy and lower specific leaf N. A subsequent glasshouse study with ‘Early Bunch’ peanut compared growth and RUE at day/night temperature regimes of 33/23 °C and 33/17 °C, and confirmed the role of night temperature in determining RUE. Cool night effects were associated with increased specific leaf weight and lower stomatal conductances. Both effects were evident from 7 d after start of treatments, but differences were never greater than ≈ 10%. Analysis of published RUE data for Early Bunch peanut from tropical and subtropical environments collectively showed a highly significant (P < 0.01) negative linear relationship between RUE and night temperature.
Evaluation of Urease Inhibitors as Urea Amendments for Use on Kentucky Bluegrass Turf
Authors: Joo Young K. , Christians Nick E. , Spear Grant T. , Bremner John M.
Published: July 2010

Urea applied to turf areas can result in loss of urea N through NH3 volatilization. One approach to decrease N loss is the use of urease inhibitors. The objectives of this study were to evaluate the urease inhibitors N‐(n‐butyl) thiophosphoric triamide (NBPT) and phenylphosphorodiamidate (PPD) as fertilizer amendments for increasing N‐use efficiency of urea applied to Kentucky bluegrass (Poa pratensis L.) turf in both the laboratory and the field. A forced‐draft system used to measure NH3 volatilization in the laboratory incorporated four levels of NBPT and three levels of PPD combined with 49 kg urea N ha−1. Cumulative loss of urea N as NH3 without inhibitors was 49.9% over 7d. Percentage reduction of NH3 volatilization in 7 d was 34.4, 46.5, and 50.1% for 1, 2, and 3% (w/w) PPD treatments, respectively; and 41.8, 50.7, 54.2, and 59.2% for 0.125, 0.25, 0.5, and 1.0% (w/w) NBPT treatments, respectively. A 2‐yr field experiment was also conducted that measured turf response to urea N at 0 to 73.5 kg ha−1 with NBPT at 0, 0.25, and 0.5% of the weight of N. There was little quality or clipping yield response to NBPT in the 1988 and the 1989 field trials. When responses were measured, they ranged from negative, due to tip burn, to a positive clipping response at the high rate of NBPT late in the 1989 season. More work will be necessary to further assess the usefulness of urease inhibitors for reduction of NH3‐N loss under field conditions.
Leaf Feeding Resistance to Multiple Insect Species in a Maize Diallel
Authors: Thome Catherine R. , Smith Margaret E. , Mihm John A.
Published: July 2010

The southwestern corn borer (SWCB), Diatraea grandiosella Dyar, and the sugarcane borer (SCB), D. saccharalis F., are important pests of maize, Zea mays L., in some regions of the Americas. The European corn borer (ECB), Ostrinia nubilalis Hübner, is a major maize pest in temperate North America and Europe. Germplasm with resistance to leaf feeding by these insect species was developed at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, but little was known about the inheritance of resistance in this germplasm. A 10‐parent diailel cross of eight CIMMYT inbreds and two susceptible public inbreds was evaluated for leaf feeding by SWCB, SCB, and ECB in separate trials. General combining ability (GCA) for leaf feeding rating was a significant source of variation among F1's under artificial infestation with each of the three insect species. Variation due to specific combining ability (SCA) was not significant. Both leaf feeding ratings for F1's and estimated GCA effects were highly correlated between SWCB and SCB infested trials, indicating that selection for resistance to one species probably confers resistance to the other in the materials in the study. ECB leaf feeding ratings of the F1's and GCA effects were also highly significantly correlated with those of the other two species, but correlation coefficients were slightly lower than those between SWCB and SCB. ECB is the least aggressive leaf feeder in this study, hence selection for resistance to ECB may not confer resistance to SWCB or SCB, but selection for resistance to SWCB or SCB appears to confer ECB leaf feeding resistance. Some inbreds developed from CIMMYT's multiple borer resistant (MBR) population showed good leaf feeding resistance to all three insect species. Breeding methods that take advantage of additive genetic variance should be effective in utilizing this resistance.
Geographical Variation in Alfalfa Accessions for Resistance to Two Isolates of Peronospora trifoliorum
Authors: Skinner Daniel Z. , Stuteville Donald L.
Published: July 2010

We evaluated the resistance of 631 plant introduction accessions (PIs) of alfalfa (Medicago sativa L.) from 50 countries, to two isolates (I‐7 and I‐8) of Peronospora trifoliorum de Bary, causal fungus of alfalfa downy mildew. The objectives were to investigate the association of alfalfa subspecies, basic germplasm source, fall dormancy, and regions of origin, with levels of resistance to P. trifoliorum. Differences between mean percentages of resistance to the fungus isolates were tested for statistical significance with t‐prime tests, or LSD tests, adjusted in accordance with Bonferroni's inequalities. Five M. sativa subspecies were included: falcata, × varia, sativa, × hemicycla, and caerulea. The mean proportions of plants resistant to one isolate were not significantly different from the proportions resistance to the other isolate within any subspecies. Hence, genetic ancestry of the plants apparently was unrelated to isolate‐specific resistance. Mean percentages of resistant plants ranged from 26.8 (subsp. falcata), to 6.3 (subsp. caerulea). Subspecies sativa accessions averaged 15.4% resistant plants. Significant differences between isolates within individual accessions were found in 160 accessions. The PIs with significantly more plants resistant to I‐7 than to I‐8 were from South and Central America, the Mediterranean area, and Australia. Plant introductions with significantly more plants resistant to isolate I‐8 than to I‐7 were from northern Europe and North America. This isolate‐specific resistance did not appear to be associated with the geographic centers of origin of the basic types of alfalfa germplasms.
Grain Protein Inheritance and Nitrogen Uptake and Redistribution in a Spring Wheat Cross
Authors: Beninati Noel F. , Busch Robert H.
Published: July 2010

Grain‐protein concentration in hard red spring wheat (Triticum aestivum L.) is important to bread‐making quality and human nutrition, and for its economic impact in marketing. The inheritance of high protein concentration in Minnpro, a cultivar released in 1989, was studied because progeny from its previous crosses in the breeding program appeared to have segregated in a qualitative fashion. Minnpro was crossed to MN7570, a lower‐protein line, and 88 and 84 F4‐ derived F7 lines were grown in a simple lattice design at two locations in Minnesota in 1984. Traits measured were grain yield, grain‐protein concentration, and the physiological traits (biological yield, harvest index, plant N concentration, N concentration index, total plant N, and N harvest index) associated with N uptake and redistribution. The latter traits were measured in order to determine their associations and the possible physiological relationship with the increased grain protein. For grain‐protein concentration, the data fit a bimodal distribution at each location and across locations with a monogenic ratio (9 high:7 low) expected for randomly selected F4‐derived lines. As further evidence of probable qualitative inheritance of grain protein concentration, the genotype × location interaction was nonsignificant, and the correlation of the lines between locations for grain protein concentration was positive and high (r = 0.8, P < 0.01). Grain‐protein concentration was positively associated with N concentration in the aerial vegetation on a per unit area basis but not with total aerial biomass. Thus, grain‐protein concentration was associated with more efficient N redistribution per unit of aerial biomass, but not with the redistribution of a greater quantity of N per unit area.
Recurrent Selection for Seed Size in Soybean: II. Indirect Effects on Seed Growth Rate
Authors: Tinius Christopher N. , Burton Joseph W. , Carter Thomas E.
Published: July 2010

Seed growth rate (SGR) and effective filling period (EFP) have been associated with both seed size and seed yield in soybean [Glycine max (L.) Merr.]. Three subpopulations (designated SS1, SS2, and SS3) the intermating population N79‐1500, which segregates for male sterility (ms1ms1), were subjected to recurrent selection for increased seed size of male‐sterile (MS) plants. The objective was to examine the relationship between seed size and development, and their effects on seed yield in the materials derived from selection. After four cycles of selection in SS1 and SS2, and three cycles in SS3, a composite of the parents of each cycle was tested at two locations in North Carolina in 1987 and 1988. A random sample of pods was collected on three dates ≈ 10 d apart from the upper third of the canopy beginning at growth stage R5. The SGR was estimated by linear regression of seed weight on sampling day after 31 August, and EFP was calculated as mature seed size divided by SGR. A significant linear increase in SGR occurred in SS2 and SS3 across cycles of selection. Differences in EFP within and among subpopulations were not significant. The SGR apparently was more important than EFP in producing the increases in seed size of male‐fertile (MF) plants. Seed size increased significantly in all three subpopulations and seed yield increased significantly in SS2 and SS3, but there were no significant differences across cycles of selection for seed number (seeds ha−1).
Genetics of Parenchyma Cell Death in Corn Stalk Internodes and Leaf Midribs
Authors: Dronavalli S. , Kang Manjit S. , Gorman D. P.
Published: July 2010

Pith (parenchyma) cell death (PCD) in stalk internodes of corn (Zea mays L.) is positively associated with stalk rot. Only limited information on inheritance of PCD is available, and none for corn with the leafy (Lfy) gene. The objectives of this study were to (i) estimate general (GCA) and specific combining ability (SCA) effects, (ii) determine the effect of the Lfy gene on PCD and leaf midrib parenchyma cell death (LMCD) among 21 F1 crosses from seven Lfy synthetics (A619, A632, B73, Hy, Mo17, wf9, and 914), and (iii) determine if LMCD is correlated with PCD. In 1989 and 1990, we visually rated LMCD of five Lfy and five non‐Lfy plants (5 leaves plant−1) ≈1 wk before midsilk. Then for PCD, 21 d after midsilk, we visually rated the first four stalk internodes above the brace roots of all plants (1988) or 10 Lfy and 10 non‐Lfy plants in each plot (1989 and 1990). For PCD, SCA was more important than GCA, as suggested by small ratios (0.32 and 0.18) of GCA (σ2s) and SCA (σ2g) variances computed using 2σ2g/(σ2g + σ2g). The A632, B73, and Mo17 synthetics showed significant negative GCA effects for PCD; their use in a breeding program might be effective in reducing stalk internodal parenchyma cell death. Use of F1 crosses Mo17 syn × 914 syn, A619 syn × Mo17 syn, and B73 syn × Hy syn should be avoided, as they showed significant positive SCA effects for PCD. Evaluation of all four stalk internodes might not be necessary, as the third internodes provided more reliable PCD data than the others. Pith cell death was significantly lower in the Lfy than the non‐Lfy plants. Leaf midrib cell death and PCD were not correlated genetically or phenotypically, which suggests that selection for LMCD would not change PCD. A 2σ2g/(σ2g + σ2s) ratio of 0.59 for LMCD suggests that both GCA and SCA are important. The A632 syn and B73 syn showed significant negative and 914 syn showed significant positive GCA effects for both LMCD and PCD. Mean LMCD (across leaves) of Lfy plants was significantly lower than that of non‐Lfy plants in two of three environments.
Heterosis and Combining Ability of CIMMYT's Quality Protein Maize Germplasm: I. Lowland Tropical
Authors: Vasal Surinder K. , Srinivasan Ganesan , Pandey Shivaji , González F.C. , Crossa José , Beck David L.
Published: July 2010

CIMMYT has developed a wide array of hard endosperm opaque‐2 (o2) maize (Zea mays L.) germplasm, through the combined use of two genetic systems involving the o2 gene for improving protein quality and the genetic modifiers of the o2 locus for improving kernel phenotype and ameliorating other o2‐associated defects. The objective of this study was to determine the heterotic patterns and combining ability of tropical quality protein maize (QPM) germplasm, and identify superior germplasm suitable for hybrid development. Ten parents (four QPM pools, five QPM populations, and experimental variety PR 7737) were used in a diallel study in eight environments. Data on grain yield, time to silk, plant height, and endosperm hardness were recorded. General combining ability (GCA) effects were highly significant for all traits; specific combining ability (SCA) effects were signififant for time to silk and plant height. Genotype × environment interactions and their partitions were significant for grain yield and endosperm hardness. Pool 24 QPM was the highest‐yielding parent (6.48 Mg ha‐1) and Pool 24 QPM × Population 63 was the highest‐yielding croos (6.56 Mg ha‐1) among hard endosperm parents. PR 7737, a soft endosperm opaque‐2, was low yielding as a parent, but performed better in crosses with other hard endosperm parents and showed high heterosis. High‐parent heterosis for grain yield was generally low in all crosses except those involving PR 7737 as a parent. Endosperm hardness ratings were intermediate relative to the parents, suggesting polygenic control. Crosses among white endosperm parents generally performed better than crosses among yellow endosperm parents. Crosses among dents and dent × flints yielded higher than flint crosses, but flint parents and their crosses had a superior endosperm modification. compared with dents. Populations 62, 63, and PR 7737 showed significant positive GCA effects for grain yield; Pool 23 QPM, Pool 25 QPM, and Populations 62, 64, and 65 had significant negative GCA effects for endosperm hardness. Populations 62 and 63 among white endosperm materials and Population 65 among yellow endosperm could be used for initiating hybrid development work. The broad genetic base provides opportunities for developing intrapopulation interline hybrids.
Heterosis and Combining Ability of CIMMYT's Quality Protein Maize Germplasm: II. Subtropical
Authors: Vasal Surinder K. , Srinivasan Ganesan , González F.C. , Beck David L. , Crossa José
Published: July 2010

Information on the combining ability and heterotic patterns of CIMMYT's maize (Zea mays L.) germ plasm is of great value to maize breeders worldwide, for hybrid development. The objective of this study was to determine the heterosis and combining ability of CIMMYT's subtropical quality protein maize (QPM) germplasm, and to identify suitable germplasm for hybrid development. Six QPM gene pools and four QPM populations were used to make a 10‐parent diallei. Parents and the 45 crosses were tested in three environments in Mexico and three in the USA. Highly significant (P < 0.01) differences were observed among entries, parents, and crosses for grain yield, time to silk, plant height, and endosperm hardness in Mexican environments, and for grain yield, ear height, and time to silk in U.S. environments. General combining ability (GCA) effects were highly significant for all traits, while specific combining ability (SCA) effects were nonsignificant (P > 0.05). Population 68 QPM was the highestyielding parent (6.99 Mg ha‐1) in Mexican environments, and Pool 31 QPM was the highest yielding (4.65 Mg ha‐1) in U.S. environments. The highest‐yielding crosses were Pool 32 QPM × Population 68 QPM (7.05 Mg ha‐1) in Mexican and Pool 29 QPM × Population 70 QPM (5.12 Mg ha‐1) in U.S. environments. Under Mexican environments, Population 68 QPM and Pool 32 QPM among whites and Population 69 QPM and Pool 34 QPM among yellows were the best general combiners for grain yield. For endosperm hardness, the best combiners were Pool 33 QPM, Population 69 QPM, and Pool 31 QPM, all of which have flint grain type. Under temperate U.S. conditions, the two early‐maturity gene pools (Pool 27 QPM and Pool 29 QPM) and Population 70 QPM were the best combiners for grain yield. For subtropical conditions, Population 68 QPM, Pool 32 QPM, Population 69 QPM, and Pool 34 QPM hold potential for hybrid development. These are hard endosperm opaque‐2 (o2) parents (except for Pool 34 QPM, a partially modified parent). For temperate breeding programs in the USA, Pool 27 QPM, Pool 29 QPM, and Population 70 QPM could be used as exotic germplasm sources for introgression into U.S. Corn Belt QPM materials and for developing hard endosperm QPM hybrids.