bluuebunny/crossref_metadata_2025 huggingface dataset:
CO2‐Enrichment Effects on Wheat Yield and Physiology1
Authors: Havelka U. D. , Wittenback V. A. , Boyle M. G.
Published: July 2010

High CO2 was applied to field‐grown winter wheat (Triticum aestivum L. cv. Arthur) during different growth periods in order to identify when photosynthesis was most limiting grain yield. Wheat was grown in open top Mylar® polyester chambers which were provided with circulated air (340 μL/L CO2 = control treatment) or air enriched with sufficient CO2 to expose the foliage to 1200 μL/L (high CO2 treatment). The CO2 enrichment treatments were applied from jointing to anthesis, from jointing to maturity, or from anthesis to maturity. Seed yield and total dry matter were influenced most by CO2 during the period from jointing to anthesis. The 17% increase in seed yield resulted from more seed per meter2, which was associated with an increase in heads per meter2. Total dry matter at maturity was increased by 11%. Neither harvest index nor nitrogen content of plant parts at harvest were altered by CO2 enrichment. In order to characterize the effect of CO2 on seed yield, several physiological parameters of leaf function were monitored using the flag leaves of plants grown in the control chambers and the high CO2 chambers treated from jointing to maturity. High CO2 had no significant effect on flag leaf chlorophyll and protein content or the onset of their decline during senescence. In addition, there was no effect on the level of ribulose bisphosphate carboxylase or its decline during senescence or on total proteolytic activity. High CO2 did, however, cause a 50% increase in apparent photosynthesis of the flag leaf. This resulted in a doubling of the sucrose and starch content of the flag leaf prior to seed growth. With the onset of seed growth this difference in sucrose and starch levels rapidly disappeared, suggesting a rapid mobilization to the head and developing seeds.
Genetic Variability and Correlations in a Modified Endosperm Texture Opaque‐2 Maize Population1
Authors: Wessel‐Beaver L. , Lambert R. J. , Dudley J. W.
Published: July 2010

To better understand the relationship between endosperm texture, protein quality, and other seed traits in modified endosperm (vitreous) opaque‐2 maize (Zea mays L.), estimates of additive and dominance variance, heritability, and genetic correlations were obtained for a population designated Disease Oil modified opaque‐2. Sixty S1 families were grown in 1977. In 1980, 240 S2 families (four from each S1 family) were evaluated. Families were measured for percent and degree of endosperm modification, 100 kernel weight, kernel density, plant height, percent lysine, percent protein, and lysine per 100 g of protein. All traits showed significant genetic variance. Heritability estimates were high to intermediate for all traits except kernel density. Additive genetic variance was significant and dominance variance nonsignificant for percent lysine and protein, lysine per 100 g protein and plant height. Dominance variance was significant and additive variance nonsignificant for endosperm modification, 100 kernel weight, kernel volume and density. Endosperm modification was negatively correlated with percent lysine, percent protein, and lysine per 100 g protein. Therefore, selection for endosperm modification should be accompanied by selection for lysine content to insure levels similar to non‐modified opaque‐2 material. Endosperm modification was highly positively correlated with kernel density.
Reproductive Duration and Date of Maturity in Populations of Three Wide Soybean Crosses1
Authors: Metz G. L. , Green D. E. , Shibles R. M.
Published: July 2010

Greater seed yield may be related to a longer reproduction period (RP) in soybean [Glycine max (L.) Merr.]. Unique combinations of genes controlling photoperiod sensitivity may allow selection for longer RP without delaying date of physiological maturity (R7). Three single‐cross populations of F2‐derived soybean lines were made from a diallel crossing of two photoperiod‐insensitive determinate plant introductions, PI317.334B and PI317.336, and an indeterminate cv. Harosoy 63 in an attempt to develop populations in which the correlations of date of R7 with length of the seed‐filling period (SFP) and RP are small. Genetic variability and response to selection of these traits were also studied. Time from beginning of flowering (R1) to beginning of rapid seed filling (RS) of determinate lines averaged 12.6 days and 7.3 days shorter than those of indeterminate lines in two crosses, while SFP, days from R5 to R7, averaged 11.2 and 6.7 days longer for determinate lines than for indeterminate lines. These results are likely due to the difference in estimating stage R5 (seeds 3 mm long in one of the top four plant nodes) between determinate and indeterminate lines rather than biological differences in SFP between determinates and indeterminates. Associations of SFP and RP with R7 in crosses of Harosoy 63 with either plant introduction were weaker than those previously reported for US‐adapted germplasm. Estimates of realized heritabilities of RP ranged from 0.63 to 1.17, even when RP was adjusted for differences in R7. Realized heritability estimates of SFP ranged from 0.40 to 1.02, except for indeterminates where considerably less genetic variance was observed. Reproduction period and SFP of selected F4 populations were lengthened by F3 selection up to 6.4 and 6.1 days, respectively, relative to population means, without significantly changing R7. These results suggest that selections from two of the three crosses should be useful for incorporation of longer SFP and RP into adapted germplasm to enhance yield potential without delaying date of R7.
Yield Components of Cowpeas Grown in Two Environments1
Authors: Kahn Brian A. , Stoffella Peter J.
Published: July 2010

Nine cultivars of cowpea [Vigna unguiculata (L.) Walp.] were grown in Spring 1983 at Fort Pierce, FL (Alfic Arenic Haplaquods soil) and Bixby, OK (Typic Udifluvents soil). The objective was to identify yield components which were consistently related to seed yield in two diverse environments. Double‐row plots with 0.46 m between the two rows within each plot and 1.64 m between the rows of adjacent plots were used at both locations, with a within‐row spacing of 20 plants per meter. Irrigation was provided by a subsurface system in Florida and by sprinklers in Oklahoma. Cultivars were harvested individually as soon as the majority of the pods were dry. Eighty plants per cultivar were evaluated at each location for seed yield per plot and several potential morphological components of yield. Harvest indices averaged 0.17 in Florida and 0.31 in Oklahoma. Forage yields were high in Florida, perhaps due to high N fertilization, while seed yields were only slightly lower than in Oklahoma. Seed number per pod was highest in Florida while average seed size was greater in Oklahoma. Despite these differences, the same three‐variable regression model (log forage yield per plot, log harvest index, and log pod number per plant) accounted for 92 and 99% of the variability in log seed yield per plot in Florida and Oklahoma, respectively. Seed number per pod and seed size provided little additional indication of crop yield. Pod number per plant was the single component most strongly and consistently related to seed yield. An increase in the number of pod‐bearing peduncles is suggested as an appropriate objective when selecting for increased cowpea yield.
Manganese Deficiency and Toxicity Effects on Photosynthesis, Chlorophyll, and Transpiration in Wheat1
Authors: Ohki K.
Published: July 2010

Wheat (Triticum aestivum L.) production areas are expanding to soils low in available Mn in southern Georgia and to soils high in available Mn in northern Georgia. Useful data on Mn deficient and toxic levels in leaf tissue for top growth and physiological processes in wheat are needed to evaluate growth processes limiting wheat production. The objectives of this study were to correlate Mn deficiency and toxicity levels with top dry weight production, photosynthesis, chlorophyll concentration, and transpiration. Wheat plants were grown in 10 experimental concentrations ranging from 0.09 μM to 9.1 mM in nutrient solution. Photosynthesis and transpriration measurements were made on blade 1 of plants grown in the greanhouse. Total chlorophyll and Mn concentrations were determined on the experimental tissue after freeze‐drying. Foliar dry weights on a per pot (15 plants) basis were also determined. Severe Mn deficiency depressed top dry weight, photosynthesis, and total chlorophyll concentration, but transpiration was unaffected. Mild Mn toxicity reduced top dry weight but not photosynthesis, total chlorophyll concentration, or transpiration. Critical Mn deficiency levels for reducing top dry weight and apparent photosynthesis rates were similar, namely 0.23 and 0.30 mmol kg−1, repectively. Growth reduction from Mn deficiency is possibly due to reduced photosynthesis. Minimum Mn requirements for chlorophyll (0.14 mmol kg−1) is about one‐half of that for top production. The critical Mn deficiency level for transpiration could not be determined. The critical Mn toxicity level for top dry weight occurred at 7 mmol kg−1. Concentrations of 19, 19, and 24 mmol kg−1 were required for the depression of photosynthesis, total chlorophyll concentration, and transpiration, respectively. Maximum growth and yield are expected when the range of Mn concentration in blade 1 is 0.23 to 7 mmol kg−1. The critical levels are prelimilinary values to be used in evaluating Mn status of field‐grown wheat for possible deficiency and toxicity.
Exact Confidence Intervals for Heritability on a Progeny Mean Basis1
Authors: Knapp S. J. , Stroup W. W. , Ross W. M.
Published: July 2010

Heritability (H) on a progeny mean basis is frequently estimated in recurrent selection experiments for the purpose of estimating the expected progress from family selection; however, appropriate measures of precision have been developed for only a few heritability estimators. The objective of this research was to develop a measure of precision for H for certain balanced linear models. Exact confidence intervals for H were derived and are not restricted to a specific experimental design. The confidence intervals were applied to sorghum [Sorghum bicolor (L.) Moench] half‐sib family data.
Genotypic Differences in Soybean Affecting the Rates of Assimilate Transport from the Leaf1
Authors: Hanson W. D. , Kenny S. T.
Published: July 2010

Six soybean lines [Glycine max (L.) Merr.] differing in growth rates and 15 lines differing in cross‐sectional phloem areas in the petiole were selected for study. The objective was to identify and assess genetic differences that affect assimilate transfer. The 14C‐assimilate transport from the fifth leaf of plants in the V7 to V8 growth stage was evaluated. The source‐sink relationship for the fifth leaf was standarized among genotypes with respect to its leaf area (source) and axillary branch initials with developing leaves (sinks). Source‐sink manipulations involved removal of either the branch initials or source leaves other than the fifth leaf (defoliation). A l‐in‐20 divergent selection among field‐grown genotypes for petiole diameter scores created a 28% difference among genotypes for cross‐sectional phloem areas in the petiole. Under the selected source‐sink balance, genotypes had similar transport velocities and specific mass transfers but had different relative mass transfer rates. The transport differences were associated with comparisons having different phloem areas. Thus, no restriction to assimilate transfer could be associated with specific genotypes other than transport capacity. The initial response to decreasing source relative to sinks was the reduction of total sucrose in the petiole. Both transport velocity and rate were about one‐third greater for defoliation than for control treatments. Genotypes can be selected which have larger phloem area but the existing vascular systems had a surprising capacity to meet increased requirements for assimilate utilization.
Forage Quality in Stratified Canopies of Alfalfa, Birdsfoot Trefoil, and Red Clover1
Authors: Buxton D. R. , Hornstein J. S. , Wedin W. F. , Marten G. C.
Published: July 2010

Forage quality usually is evaluated on a total‐herbage basis although in vitro digestible dry matter (IVDDM) and crude protein (CP) concentrations can vary greatly among plant parts. This study was conducted to compare IVDDM and CP concentrations of leaf blades (leaves) and remaining plant parts (stems) and the relative amount of these plant parts present within plant‐canopy segments of alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.). Unseparated herbage of white clover (Trifolium repens L.) was included for comparison. Plants were sampled three or four times during two 6‐week growth periods, starting when plants were in the prebud stage. At each harvest, alfalfa and birdsfoot trefoil stems were separated above 6th and 12th nodes (from cut stem base), and leaf blades were removed. Red clover was divided above the 3rd and 6th nodes, and leaf blades also were removed. The IVDDM concentration in total herbage was greatest in white clover and frequently least in alfalfa. The IVDDM concentration of alfalfa and birdsfoot trefoil stems decreased about twice as rapidly as total herbage plant IVDDM concentration during advancing maturity. Stem bases had less IVDDM concentration than stem tops with a rate of change among stem segments of about 20 g kg‐1 dry matter (DM) node‐1. Red clover stems had greater IVDDM concentration than did leaves until flowering. The rate of change among red clover stem segments was less than 8 g kg‐1 DM node‐1. In contrast to IVDDM, range in CP concentration among the plant parts was nearly as large at the beginning as at the end of each period because of a nearly parallel rate of CP decline in the plants. Leaf mass decreased and stem mass increased in the basal segment during each period, which decreased the leaf‐to‐stem mass ratio of basal segments to 0.06 or less for alfalfa, 0.16 for birdsfoot trefoil, and 0.23 or less for red clover by the end of the two periods. We conclude that attempts to improve forage quality of alfalfa and birdsfoot trefoil should be directed toward the lower portion of the plant canopy.
Genetic and Linkage Analysis of a Leucine Aminopeptidase in Wild and Cultivated Soybean1
Authors: Kiang Y. T. , Gorman M. B. , Chiang Y. C.
Published: July 2010

Two electrophoretic variants of leucine aminopeptidase have been observed in mature soybean seeds [Glycine max (L.) Merrill, and G. soja Sieb. and Zucc.]. The two variants are inherited as codominant alleles at one locus. The genetic symbol Lap1‐a and Lap1‐b are assigned to slow (Rf 0.49) and fast (Rf 0.53) migrating zymograms, respectively. The Lap 1 enzyme is cytosol‐associated. The Lap1‐b is the most common allele in both G. max (allele frequency 0.985) and G. soja (0.879). The Lap1 and Ap (acid phosphatase) loci are found to be linked with 19.88 ± 0.01 map units between them. The Lapl locus is inherited independently of three other biochemical loci (Am3, Dia2, and Pgm1).
Scanning Electron Microscope (SEM) Studies of Morphology of Range Grasses in Relation to Feeding by Labops hesperius1
Authors: Ling Y. H. , Campbell W. F. , Haws B. A. , Asay K. H.
Published: July 2010

Large populations of black grass bugs, Labops hesperius Uhler (Hemiptera:Miridae), have been observed on extensive hectares of range lands. These bugs cause severe damage to range grasses, lowering their palatability and productivity. Perusal of the literature indicated a correlation between trichome size and density and plant resitance to insect damage. This study was to determine whether morphological differences among breeding lines of grass species or synthetics could be correlated with the feeding behavior of black grass bugs. If so, plant breeders should be able to develop resistant cultivars. To explore this possibility, bug densities per treatment chamber of 10, 20 or 40 for Instars‐ II and ‐IIl and 10 or 20 for Instars‐IV and ‐V were grazed on quackgrass, Elytrigia repens (L.) Nevski, bluebunch wheatgrass, Pseudoroegneria spicata (Pursh) Löve, standard crested wheat‐grass, Agropyron desertorium (Fisch. ex Link) Schult., fairway crested wheatgrass, A. cristatum (L.) Gaertn., quackgrass ✕ standard crested wheatgrass, E. repens ✕ A. desertorium, RD hybrid, quackgrass ✕ bluegrass wheatgrass, E. repens ✕ P. spicata, RS hybrid, quackgrass ✕ fairway crested wheatgrass, E. repens ✕ A. cristatum, RC hybrid, Kentucky bluegrass, Poa pratensis L., orchardgrass, Dactylis glomerata L., and reed canarygrass, Phalaris arundinacea L. A scanning electron microscope (SEM) was used to compare and relate trichome size and density on range grass plants with the level of black grassbug preference or nonpreference. Based on leaf area damaged by feeding insect, orchardgrass and reed canarygrass were the least preferred. Kentucky bluegrass, quackgrass, standard and fairway crested wheatgrass, RS, and RC hybrids were most preferred. Older nymphs preferred the RD hybrid over the RC hybrid. Bluebunch wheatgrass and the RD hybrid were less preferred by the nymphs. Quackgrass, Kentucky bluegrass, orchardgrass and reed canary‐grass had relatively smooth surfaces with very short trichomes, if any, on either side of the leaf. Trichomes on the leaf surface of the RS hybrid were similar to those of the quackgrass parent, whereas the trichomes on the RC and RD hybrids were similar and intermediate between that of their parents. Field grown grasses had denser trichomes and more surface waxes, and the trichomes appeared more rigid than on.grasses grown in the green house. Given the relatively large size of the trichomes (194.5 μm) on some grasses, e.g., fairway crested wheatgrass, comparison to the small size of the early nymphal stages of the black grass bug, selecting clones of wheatgrasses with large trichomes should offer some resistance to this troublesome pest.
Nodulation Mutants in Chickpea1
Authors: Davis Thomas M. , Foster K. W. , Phillips Donald A.
Published: July 2010

As a first step toward future studies of symbiotic N2 fixation in chickpea (Cicer arietinum L.), genotypes exhibiting aberrant responses to inoculation with Rhizobium strain CC1192 were isolated by selection following γ,‐irradiation mutagenesis of chickpea line P502. In greenhouse experiments, 28 of 968 M2 families contained one or more plants which showed stunted, chlorotic growth after 30 to 35 days under N2‐dependent conditions but which resumed vigorous growth with the addition of 8 mM NH4NO5. Of 24 selections advanced to the M4 generation, two lines, PM233 and PM665, rep:roducibly failed to form root nodules under various conditions where the parental control P502 was well nodulated. PM233 and PM665 grew vigorously with 8 mM NH4NO5, but PM665 could be distinguished from the wild type by lighter green leaves and slightly crinkled pods. Six other lines exhibited aberrant responses to inoculation in replicated M4‐generation testing, but have not yet been satisfactorily characterized.
Comparison Of Germination Techniques for Wild Helianthus Seeds1
Authors: Chandler J. M. , Jan C. C.
Published: July 2010

Seed dormancy has hampered previous efforts to study Helianthus sp. and to use them in breeding programs for improving the cultivated sunflower, H. annuus L. Several seed treatments were tested to determine their effectiveness in overcoming the strong seed dormancy found in many wild Helianthus sp. The first treatment (referred to as the complete treatment) involved mechanical scarification of the seed, a 1 h soak in a 100 mg/L solution of gibberellic acid (GA3), plus hull removal. Other treatments were simplifications of this procedure, and three whole seed treatments using GA3 or ethylene. The results indiicate that treatments which removed the hull and seed coat were the most effective, giving germination of over 90% for many species including the hard‐to‐germinate annual desert species. Soaking scarified seeds for 1 h in a 100 mg/L GA9 solution increased germination for some accessions. Soaking whole seeds in 100 mg/L GA3 for 1 h or 50 mg/L 2‐chloroethylphosphonie acid for 16 h did not increase germination. Incubating whole seeds for 10 days in either 100 or 1000 mg/L GA3 increased germination but produced abnormal plants. The complete treatment is recommended despite its complexity because it gives a high germination percentage and varies least from accession to accession.
Effect of Temperature on Seed Dormancy of Wheat1
Authors: Reddy L. V. , Metzger R. J. , Ching T. M.
Published: July 2010

In wheat (Triticum aestivum I.) the level of seed dormancy expressed depends on the temperatures encountered during the grain‐filling period. Because of the significant role of seed dormancy in preharvest sprout damage of wheat cultivars, this study was undertaken to determine the levels of seed dormancy induced in wheat cultivars ‘Hyslop’, ‘Yamhill’, ‘P.I. 178211’, ‘Brevor’, and ‘Tom Thumb’ grown at controlled temperatures at 15 and 26°C in growth chambers during the grain‐filling period and in the field‐grown plants. The degree of dormancy was measured in terms of weighted germination percentage (WGP) that takes into account the rate and number of seeds that germinated at controlled germination temperatures of 15, 20, and 26°C. Yamhill and Hyslop exhibited the least potential for producing dormant seeds. Seeds of P.I. 17(1211, Brevor, and Tom Thumb acquire some dormancy when developed at 26°C, but the greatest degree of dormancy was measured in seeds developed at 15°C. It appears that the maximum potential a cultivar possesses for producing dormant seeds can be revealed by determining the germination of seeds developed at 15°C and germinated at 15, 20, and 26°C.
Selection Response Based on Selfed Progenies1
Authors: Cockerham C. Clark , Matzinger D. F.
Published: July 2010

A quantitative genetic modelf or arbitrary numbers of alleles and loci with additive, dominance, and additive by additive epistatle effects was employed. Utilizing descent measures and the genetic components, the selection response from selecting among self‐fertilized progenies in generation g, and measuredin selffertilized relatives in generation g', where the last common ancestor was in generation t, was formulated. Permanent response, g' = ∞, led to considerable simplifications. The effect of the number of generations, t, of selfing before testing on the permanent response relative to the response from selecting among homozygotes,t = ∞, was evaluated numerically for a model with two loci, two alleles each. The result varied within a narrow range depending on gene frequencies and effects with a mean relative response of 0.68, 0.83, 0.92, 0.96, 0.98 for t = 1,2,3,4,5, respectively. Selection response based on self‐progeny evaluation was also formulated for the outbred performance of the offspring of randomly mated g's. On a per generation basis, the numerical evaluations gave about the same overall picture for t = 1 and t = 2 and less response for t > 2. If time is of no importance, the response generally increased with t, but there are parameter combinations of gene frequencies and effects for which the response is slightly negative. These responses were compared to those from evaluating full‐sib progenies from crossing pairs of self progenies, which give exactly the same result for t = 1 and t = 2 on a per generation basis. Self‐progeny evaluations generally lead to more selection response than fullsib progenies except for those parameter combinations for which the response is slightly negative, and then it is very small for the full‐sib progeny evaluation. Permanent response is slightly less than immediate response for inbred performance, and varies more with gene frequencies and effects when t is small. Permanent response for outbred performancec an be muchl ess than immediate response depending on the additive by additive variance.
Effect of Gene Rps1 for Resistance to Phytophthora Rot on Yield and Other Characteristics of Soybean1
Authors: Singh N. B. , Lambert J. W.
Published: July 2010

Two experiments were conducted to measure the effect of gene Rps1, on seed yield and seven other agronomic traits by comparing closely related soybean [Glycine max (L.) Merr.] lines differing in resistance and susceptibility to Phytophthora megasperma f. sp. glycinea, Kuan and Erwin, in environments where the disease was not evident. In Exp. 1, seven resistant (Rps1 Rps1) and seven susceptible ((rps1, rps1) lines from each of six crosses were grown in replicated field tests near Morris, Rosemount, and Waseca, MN in 1975 and 1976. In Exp. 2, six pairs of nearisogenic lines, differing in Phytophthora reaction within each pair, from each of the third, fourth, and fifth generations of a backcross program were grown in replicated field tests near Rosemount and Waseca in 1976. On the basis of means representing 630 observations in Exp. 1 and 108 observations in Exp. 2, we concluded that resistant and susceptible lines were not significantly different for maturity, lodging, plant height, seed yield, seed quality, seed size, seed protein, or seed oil in either experiment. There was no convincing evidence of any genetic association between the Rps1, gene and any of the agronomic traits studied.
Inhibition of Growth, Nodulation, and Nitrogen Fixation of Legumes by Quackgrass1
Authors: Weston Leslie A. , Putnam Alan R.
Published: July 2010

Quackgrass (Agropyron repens L. Beauv.) has been previously reported to possess allelopathic potential. Both the shoots and rhizomes of quackgrass have been shown to contain inhibitors of seed germination and crop growth. We recently observed chlorosis and decreases in nodulation in snapbeans that were planted into quackgrass infested sites. The objective of this study was to determine if nodulation, N,2 fixation and legume growth were inhibited in the presence of living or herbicidally treated quackgrass. Soybeans (Glycine max L. Merr.) and navybeans and snapbeans (Phaseolus vulgarls L.) were grown both in greenhouse and field experiments in living or killed quackgrass. Inoculated legumes were seeded in the following regimes: 1) living quackgrass sod which was regularly mowed; 2) glyphosate [N‐(phosphonomethyl) glycine] ‐treated quackgrass sod 3) soil from quackgrass sod from which plant material was removed by sieving or raking; 4) a control soil of similar type and physical structure free from quackgrass infestation. Nodulation and plant growth were measured by recording nodule number and fresh weight and root and shoot weights before flowering. Nitrogen fixation was estimated by the acetylene reduction assay. Legumes grown in mowed quackgrass sod in the greenhouse and in the field exhibited decreased nodule number, nodule fresh weight and N, fixation when compared to legumes grown under similar conditions in screened quackgrass soil or the control soil. Shoot and root weights were also significantly decreased in field and greenhouse experiments when legumes were grown in living quackgrassod. In many cases, legume nodulation and growth were decreased in glyphosate‐treated quackgrassod as compared to screened quackgrass soil or the control soil. Decreases in legume growth and nodulation in the presence of quackgrass may be attributed to allelochemical effects.
A Single Dominant Gene for Rust Resistance in Pearl Millet1
Authors: Andrews D. J. , Rai K. N. , Singh S. D.
Published: July 2010

Pearl millet rust (Puccinia penniseti Zimm = P. substriata var. indica) can reduce yields in hybrid seed production fields, quality in forage, and occasionally grain yields. Results are reported on the inheritance of a source of rust resistance discovered in crosses which involved one Sf progeny, #2696‐1‐4, selected from a pearl millet [Pennisetum americanum (L.) Leeke] germplasm accession originating from Chad. F1, F2, BC1, BC2 plants and the parents of crosses between the resistant source and two different susceptible male sterile lines were evaluated under severe rust pressure at three locations in India. Progeny of 2696‐1‐4 and the F1 hybrids between 2696‐1‐4 and male sterile lines were all resistant, while the male sterile lines were severely rusted at each location. In general, F2 populations from susceptible ✕ resistant crosses showed a good fit to a 3 resistant: 1 susceptible ratio and the backcrosses involving susceptible male‐sterile lines as recurrent parents showed a reasonably good fit to 1 resistant:! susceptible, indicating that rust resistance is conferred by a single dominant gene and susceptibility by its recessive allele. We propose the symbols Rpp1 and rpp1 for these genes.
Variation in Kernel Growth Characters Among Soft Red Winter Wheats1
Authors: Van Sanford D. A.
Published: July 2010

One of the components of grain yield in wheat is kernel size. Kernel size is determined by rate and duration of kernel growth. Genetic variation and genotype ✕ environment interaction for these traits has not been assessed in a large sample of soft red winter wheats. In this study, variation in kernel growth characters was evaluated in 61 elite soft red winter wheat (Triticum aestivum L.) breeding lines and cultivars. Kernel growth rate (KGR) and effective filling period (EFP) were estimated from samples of 30 spikes in replicated plots at two locations in Kentucky. Significant genotypic variation for KGR and EFP was observed at both locations. Significant genotype ✕ environment interaction was also observed for these two traits. The KGR and EFP varied from 0.78 to 1.79 mg kernel ‒1 day ‒1 and 17.3 to 32.9 days respectively. Kernel size and grain yield were significantly correlated with KGR, while EFP was not significantly correlated with either character. The data suggest that date of physiological maturity may not always be correlated with date of anthesis. Early flowering genotypes with long EFP's reached physiological maturity later than genotypes which flowered later and had shorter EFP's. Selection for high KGR may be appropriate in developing early maturing wheat cultivars suitable for double cropping.
Influence of Etched Seed Coats and Environmental Conditions on Soybean Seed Quality1
Authors: Burchett C. A. , Schapaugh W. T. , Overley C. B. , Walter T. L.
Published: July 2010

Environmental factors prevalent during the growing season in Kansas frequently result in soybean ([Glycine max (L.) Merr.] seed with a high incidence of seed‐coat etching. This seed‐coat condition has been associated with seedlots which have low germination and vigor ratings. However, seedlots free of any seedcoat etching have also exhibited low levels of germination and vigor. Since the impact etching had on the performance of a soybean seedlot was unclear, this study was conducted to examine the effect of etched seed coats on the durability of soybean seed and to determine if the incidence of etching could be reduced through supplemental irrigation or a delayed planting. Seedlots of etched seeds generally were found to have 18% lower germination and were more susceptible to damage from low drop heights than were non‐etched seedlots. Handling, as simulated by the drop heights, at low moisture ilevels and low temperatures tended to cause greater amounts of damage in etched seedlots as compared with non‐etched seedlots. Supplemental irrigation did not influence the incidence of seed‐coat etching. Supplemental irrigation did increase warm germination scores by about 2%. During the hot, dry growing season of 1980 delayed planting increased the warm germination of four early maturing genotypes. However, the improvement in seed germination was accompanied by a threefold increase in the amount of etching. During the cooler and wetter growing season of 1981, date of planting did not influence the incidence of seed‐coat etching. These results emphasized the need for careful handling of soybean seed, especially lots. exhibiting the etched seed‐coat condition, but failed to identify an environment that would reduce the severity of seed‐coat etching.
Carbohydrate Reserves and Reproductive Development at Low Leaf Water Potentials in Maize1
Authors: Westgate Mark E. , Boyer John S.
Published: July 2010

Low water potentials (ψw) during anthesis and early grain fill can decrease yields in grain crops. If photosynthesis is inhibited under these conditions, carbohydrate reserves may become limiting for grain growth. We measured the mobilization of stored nonstructural carbohydrates in the maize plant (Zea mays L.) during low ψw, imposed at silk emergence (T1), early grain fill (T2), and mid‐grain fill (T3) and maintained to maturity. low leaf ψw, completely inhibited photosynthesis, and reproductive development depended entirely on reserves. The control yield was equivalent to 9910 kg ha−1. Mean yields on a per‐plant basis were 139, 89, 25, and 0 g for the control, T3, T2, and T1 treatments, respectively. Yield losses resulted from decreased seed size in T3, decreased seed size and number in T2, and a cessation of silk and ear development in T1. After anthesis, dry matter accumulated in the stems and leaves and was mobilized to the ear at low ψw in T3 and T2 but not in T1. All the mobilized dry matter from the stems and a sizable fraction from the leaves was carbohydrate. By maturity, the mobilized carbohydrates had been depleted to the level at anthesis. In T1, there was no mobilization and the carbohydrates remained at the low anthesis levels until maturity. The low carbohydrate at T1 indicates that reserves were not sufficient to support reproductive development when photosynthesis was inhibited at low ψw. The lack of reserves may explain the high sensitivity of anthesis and early grain fill to low ψw, as well as previous reports of the inability of silks to maintain turgor by osmotic adjustment. The decreasing sensitivity of grain development to low ψw as reproduction progresses may result from an increasing availability of reserves.
A Model of Grape Growth and Development: the Mathematical Structure and Biological Considerations1
Authors: Gutierrez A. P. , Williams D. W. , Kido H.
Published: July 2010

A mathematical age structure model for dry matter production (photosynthesis) and allocation to plant parts in European grape (Vitis vinifera L.) is presented, and it is used to examine the priorities and allocation dynamics of photosynthate partitioning to respiration, reserves, leaf, stem and root tissues (i.e., vegetative), and fruit in four varieties. In the model, photosynthate is allocated first to respiration, then fruit and reserves, and lastly to vegetative growth, while the allocation rates are controlled by the ratio of photosynthate supply to the various demands at the successive priority levels. Maximum and minimum temperatures are used to compute physiological time and physiological age in the model (i.e., in degree days above 10 °C), while solar radiation (Jm−2 day−1) is used to compute the per unit leaf rate of photosynthesis. Extensive field data on dry matter allocation for the variety Chenin blanc were used to construct and validate the model, while smaller data sets were used to estimate parameters for three other varieties of grape. The model results simulate well the observed data.
Effect of Inoculations with Cochliobolus sativus at Specific Growth Stages on Grain Yield and Quality of Malting Barley1
Authors: Nutter F. W. , Pederson V. D. , Foster A. E.
Published: July 2010

Field experiments were conducted to characterize the relationship between severity of spot blotch epidemics in barley (Hordeum vulgare L.) and loss in grain yield and malt quality. The effect of spot blotch on yield and quality must be known to evaluate the economic benefit of specific disease control strategies such as the use of resistant cultivars or fungicide. Spot blotch epidemics of different intensities were established by inoculating field plots at specific barley growth stages and by using two cultivars, ‘Larker’ and ‘Dickson’, that differ in disease reaction to spot blotch. Inoculations with Cochliobolus sativus reduced yield, yield components, and malt quality of Larker more than Dickson. Yield and quality factors were more adversely affected if inoculation was just prior to flag leaf emergence or at anthesis than at early milk development. Reduction in yield in response to spot blotch epidemics was largely a function of reduction in kernel weight. In 1983, field plots of Larker, Dickson, ‘Glenn’, ‘Bumper’, ‘Robust’, and ‘Hazen’ were either inoculated with C. sativus spores or sprayed with fungicide to evaluate changes in cultivar resistance to spot blotch since the release of Larker in 1961. Based on percentage yield loss [(yield of inoculated plots)/(yield of fungicide‐treated plots)], a significant improvement in disease resistance was achieved with the release of Dickson in 1964. Percentage yield losses observed for Dickson (released in 1964), Glenn (released in 1978), Bumper (released in 1980), and Robust (released in 1983) were not statistically different from each other, indicating no further improvement in disease resistance over Dickson. However, a significant improvement in disease resistance was again achieved with the release of Hazen in 1984.
Genetic Linkage of Biochemical and Morphological Traits in Soybean1
Authors: Kiang Y. T. , Chiang Y. C.
Published: July 2010

Biochemical and morphological markers were used to study linkage relationships in soybean [Glycine max (L.) Merr.]. Pubescence color locus (t) and the ß‐amylase locus (Am3) are linked with 31.88%±2.02% recombination frequency. They are in Linkage Group 1. Pubescence color locus is unlinked with diaphorase locus (Dial), isocitrate dehydrogenase loci (Idh1, Idh2) and leucine aminopeptidase locus (Lap1). Pod color locus (l2) segregates independently of Am3, Dia2, Idh1, Idh2, Lap1, and Pgm1 loci. No linkage relationship was found between any pair of the enzyme loci studied.
Interaction of Storage Root and Shoot in Grafted Sugarbeet and Chard1
Authors: Rapoport H. F. , Loomis R. S.
Published: July 2010

Localization of controls over assimilate partitioning between storage root and shoot of Beta vulgaris L. was investigated with reciprocally grafted plants of sugarbeet and chard. It was expected that the relative roles of root and shoot would be clarified by whether or not the normally large leaves of chard would be smaller and its normally small storage root would be larger when presented with sugarbeet counterparts. The plants were grown under greenhouse and growth‐chamber conditions in pots filled with a solid rooting medium and supplied daily with excess nutrient solution. The grafts were made during the seedling stage. Dry weight accumulation of sugarbeet roots grown with chard shoots was as great or almost as great as with sugarbeet shoots, while chard roots remained small with either shoot type, indicating that storage root growth in spaced plantings is governed strongly by the capacity of the root to enlarge. The different rootstocks affected leaf size and weight and sugar composition, demonstrating competition between the leaves and storage roots for available substrate. Sugarbeet leaves were larger than normal when grown with a chard rootstock while chard tops were smaller than normal when grown with a sugarbeet rootstock. The magnitude of the effect of rootstock type was much greater for petioles than for blades, indicating that petioles have a lower priority for photosynthate than either the blades or the storage root. Leaf appearance rate was not affected by rootstock type.
Mechanisms of Yield Stability in Sorghum1
Authors: Heinrich G. M. , Francis C. A. , Eastin J. D. , Saeed Mohammad
Published: July 2010

Mechanisms that contribute to yield stability in sorghum [Sorghum bicolor (L.) Moench] were studied using six hybrids grown in 14 environments in Nebraska and Kansas. The objective was to relate yields and yield components to rainfall and temperature regimes during the growth stages GS1, GS2, and GS3. Potential sink size in each hybrid was evaluated by tiller and/or partial panicle removal in a supplementary experiment. The hybrids produced mean yields from 5410 to 9840 kg ha−1 in the diverse environments. In the regression of hybrid yield on environment mean yield, three hybrids with below average slope (b < 1.0) were designated as “stable,” and three hybrids with above average slope (b > 1.0) were designated as “unstable” or highly responsive. There was no significant correlation of yields or yield components with rainfall during the three growth stages. Length of GS2 (initiation of panicle to anthesis) was negatively correlated with mean temperature in that period. Fewer days in GS2 resulted in fewer seeds panicle−1, fewer seeds m−2, and lower yields only in unstable cultivars. Neither length of GS2 nor length of GS3 (anthesis to physiological maturity) was related to seed weight. Maximum 100‐seed weights over 14 environments were 2.47 to 2.79 g in stable hybrids, and 2.10 to 2.20 g in unstable hybrids. When portions of panicles were removed, all hybrids snowed genetic capacity to expand 100‐seed weight (2.87 to 3.54 g), with no apparent difference in potential between stable and unstable hybrids. Differences in 100‐seed weight between stable and unstable hybrids in low‐yield environments contributed to yield stability, adding credence to the importance of larger seed weight as one objective in a breeding program for low input agriculture.
Relationship Between Field and Greenhouse Ratings for Tolerance to Verticillium Wilt on Cotton1
Authors: Devey M. E. , Rosielle A. A.
Published: July 2010

Greenhouse evaluations of tolerance to Verticillium wilt, caused by Verticillium dahliae Kleb., in cotton, Gossypium hirsutum L, have been used in the past; however the relationship between field and greenhouse evaluations for the disease is not clear. In the present study, 48 cultivates and breeding lines of G. hirsutum were evaluated following induced infection by stem or root inoculation in the greenhouse and natural infection under field conditions (Exeter loam soil; Fine‐loamy, mixed, thermic Typic Durixeralfs). Highly significant differences were observed among genotypes in both greenhouse and field experiments, and broad‐sense heritability estimates were comparable, 0.70 and 0.74 for field and greenhouse, respectively. There was good agreement between field ratings and greenhouse reactions following stem inoculation; phenotypic and genotypic correlations were 0.72 and 0.86, respectively. There was essentially no relationship between field ratings and greenhouse reactions following root inoculation. Selection for wilt tolerance on the basis of field evaluations may result in later maturing plants and reduced lint yield since these characters appear to be associated with tolerance. However, greenhouse screening, which uses young plants, may avoid these correlated responses to selection. Greenhouse evaluation of Verticillium wilt tolerance may be used with confidence in selection programs for disease tolerance.
Quantitative Genetics of Agronomic and Nutritional Traits in Related Grain Sorghum Random‐mating Populations as Affected by Selection1
Authors: Flores C. I. , Ross W. M. , Maranville J. W.
Published: July 2010

Two related populations (NP20BR‐ME and NP20BR‐MEYD) of sorghum [Sorghum bicolor (L.) Moench] that were developed by one cycle of mass selection with the objectives of increasing metabolizable energy (ME) and metabolizable energy yield (MEYD), respectively, were evaluated for the effect of selection on and the relationships between agronomic and nutritional traits. Estimates were obtained from random S1 families from each population in a replications‐in‐blocks design. The means of the two populations did not differ statistically for any agronomic or nutritional trait and had similar estimates of genetic variances that revealed large genetic variation for agronomic traits but relatively little for nutritional traits. Mostraits had significant genotype ✕ year interaction variances. Broad‐sense heritabilities for all traits were relatively high (0.44 to 0.92), had low standard errors (0.10 to 0.12), and were similar in both populations. Predicted gains from 20% selection intensity were 18.2 and 15.9% of the population means for grain yield in NP20BRME and NP20BR‐MEYD, respectively. Expected gains for ME were small, and sometimes negative, whether selection was for yield, ME, or MEYD. Directional selection for grain yield alone or for ME alone would not be expected to result in simultaneous improvement of grain yield and ME, but selection for high MEYD should result in yield improvement equivalent to selection for grain yield alone with similar reductions in most nutritional traits negatively correlated with grain yield.
Combining Ability Analyses and Relationships Among Yield, Yield Components, and Architectural Traits in Dry Bean1
Authors: Nienhuis James , Singh Shree P.
Published: July 2010

Among dry bean, Phaseolus vulgarls L., cultivars developed for monoculture cropping systems in the tropics, small‐seeded cultivars often yield more than those with medium and large seeds. However, in many countries consumers prefer larger seeds. To develop high‐yielding, large‐seeded cultivars, knowledge is needed regarding the inheritance of, and relationships among yield, yield components and architectural traits. Therefore, lines with small seed (<26 g/100 seed), medium (26 to 40 g/100 seed), and/or large (>40 g/100 seed) from each of three growth habits (I, II and III), which are commonly grown in monoculture, were crossed in a diallel fashion to obtain a complete set of 72 crosses. The F1 and F2 generations were evaluated in separate consecutive seasons at two locations, Palmira (mollisols) and Popayan (inceptisols), in Colombia. All traits studied showed F1 heterosis over the midparent. Yield heterosis of the F1 over the high parent averaged 36% in Palmira and 23% in Popayan; and heterosis values tended to increase in crosses between parents of increasingly divergent growth habits. General combining ability (GCA), determined by Grifling's Method 4, Model 1 analysis, was more important than specific combining ability for yield and yield components in both the F1 and F2 analyses. In both the F1 and F1 diallel analyses, the same parents, A375 and A457, were identified as having the largest positive GCA effects for both yield and seed weight. Determinate (Type I) parents tended to have positive GCA effects for branches/plant, and negative GCA effects for the remaining architectural traits in either one or both locations, whereas the opposite was true for the indeterminate (Types II and III) parents. Yield was positively correlated with pods/m2, seeds/pod and all architectural traits except branches/plant. In contrast, seed weight was negatively correlated with yield, nodes/branch, nodes/plant, and nodes on the main stem; and positively correlated with main stem internode length and main stem length. The genetic correlations among traits suggest that selection for increased main stem internode length and main stem length should result in simultaneous improvement in both yield and seed weight; however, the resulting plant type may prove too viny and prostrate for monoculture cropping systems.