bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Starch Accumulation in the Leaf Mesophyll Layers of Soybean1
Authors: Vendeland J. S. , Bruck D. K. , Sinclair T. R.
Published: July 2010

This study was undertaken to examine a common assumption that starch is uniformly distributed in soybean [Glycine max( L.) Merr.] leaves. Observations from leaf samples collected during 4 years, including at least 12 cultivars and a shading experiment, showed this assumption to be false. In fact, a consistent hierarchy was found in the distribution of starch. Starch was first deposited in the abaxial palisade layer, followed by the spongy mesophyll, and then each of the remaining palisade layers in sequence. Unloading occurred in the reverse order in a shading experiment. Seldom was starch observed in the paraveinal mesophyll layer.
Greenhouse Seedling Technique to Determine the Reaction of Sorghum to Maize Dwarf Mosaic Virus Strain A1
Authors: Martin T. J. , Hackerott H. L.
Published: July 2010

A greenhouse seedling test to determine the reaction of sorghum [Sorghum bicolor (L.) Moench] to maize dwarf virus strain A was compared with results of field tests of mechanically inoculated and naturally infected plants. Greenhouse tests were as accurate as field tests in identifying resistant and susceptible lines. Greenhouse seedling tests were more effective in identifying the type of susceptible reactions—temperature dependent red‐leaf necrosis or temperature independent red‐stripe.
Inheritance of Resistance to Ascochyta Blight in Chickpea1
Authors: Singh K. B. , Reddy M. V.
Published: July 2010

Few genetic studies have been made to determine the inheritance of resistance to Ascochyta blight [Ascochyta rabiei (Pass) Lab.] in chickpea (Cicer arietinum L.). The objective of this study was to determine the inheritance of resistance in the lines ILC 72, ILC 183, ILC 191, ILC 200, and ICC 4935. The plants of F1 and F2populations of 12 crosses and 5 resistant and 11 susceptible parental lines were evaluated for resistance to Ascochyta blight under artificial epiphytotic conditions in plastic house and/or field. The results suggested that a single dominant gene conditioned resistance in the four parents, ILC 72, ILC 183, ILC 200, and ILC 4935, whereas resistance in ILC 191 was conferred by a single recessive gene. This is the first report on the identification of a recessive gene governing resistance to Ascochyta blight. The gene symbols of rar 1 for the recessive gene for resistance in ILC 191 and Rar 2 for the dominant gene for resistance in ILC 200 are proposed.
Breeding Low‐Tannin Sericea. II. Effects of Rhizoctonia Foliar Blight on V1 igor and Seed Yields1
Authors: Donnelly E. D.
Published: July 2010

Some low‐tannin sericea lespedeza [Lespedeza cuneata (Dumont) G. Don] genotypes are highly susceptible to a foliar disease caused by Rhizoctonia sp., but effects of the disease on vigor and seed production have not been determined. Low‐tannin lines were evaluated in field tests at three locations, and these varied from highly susceptible to highly resistant at each location. Some lines were rated as resistant at one location but susceptible at another, which suggests there may be multiple strains of the fungus. Disease severity was negatively correlated with vigor ratings, hay weights, and seed yields. Results indicated disease severity accounted for 27 to 30% of the variation in vigor and 22 to 29% of the variation in seed yields among locations. Resistant low‐tannin germplasm was developed by crossing low‐tannin plants with high‐tannin plants that havea gene or genes for resistance.
Cold Acclimation of Field Peas in a Controlled Environment1
Authors: Swensen J. B. , Murray G. A.
Published: July 2010

Two winter pea lines [Pisum sativum subsp, arvense (L.) Poir], ‘Fenn’ and ID 113, and one spring pea cultlvar (Pisum sativum L. ‘Dark Skin Perfection’) (DSP) were acclimated for 1 to 7 weeks, and frozen to determine the rate and extent of acclimation. Dry weight and percent moisture were measured after each week of acclimation on leaf, stem, and root tissues. Freezing tolerance of the two winter pea lines increased during the first 4 weeks of acclimation, attaining a minimum mean lethal temperature of −8.5 C. Survival of the spring pea cultivar, DSP, did not improve with increasing exposure to acclimating temperature. All DSP seedlings were killed with freezing stresses of −9 and −12 C, and survival averaged less than 5% at −6 C. Dry weight accumulation during acclimation did not vary among genotypes and proceeded at linear rates of 1.95, 0.9 and 1.7 mg plant−1 week−1, in leaves, stems and roots, respectively. Percent moisture declined in all tissues of winter pea seedlings, while remaining constant in DSP seedlings. Neither rate of accumulation nor distribution of dry matter were related to freezing tolerance. Percent moisture and freezing tolerance were inversely related during acclimation. However, percent moisture of winter pea seedlings continued to decline after acclimation was completed.
Trichomes in Segregating Generations of Sorghum Matings. II. Association with Shootfly Resistance1
Authors: Maiti R. K. , Gibson P. T.
Published: July 2010

The shootfly (Atherigona soccata Rond.) is a major seedling pest of sorghum in Asia and Africa. To determine whether the presence of nonglandular trichomes on the leaf lamina was associated with resistance to shootfly, trichomed, segregating, and trichomeless F2— derived lines in the F3 and F4 from four trlchomed ✕ trichomeless sorghum matings and their parents were studied at ICRISAT Center, Patancheru, India. Trichomed lines had significantly lower percentages of plants with shootfly eggs 18 days after emergence and of deadhearts (killed central shoot) at both 18 and 23 or more days after emergence. The ratio of the difference between the means of trichomed and trlchomdess lines for the percentage of deadhearts to the corresponding difference between the parents ranged from 0.16 to 0.92 and exceeded 0.32 in seven of nine comparisons. Thus, trichomes were clearly a major factor, but not the only factor, involved in resistance. Means of the parents and trichomed, segregating, and trichomeless offspring were regressed on four possible genetic models. The results indicated that at least two additional loci that interact with each other were involved in resistance. Trichome density was examined as a possible factor in resistance, but correlation of deadheart percentage with the density of trichomes was low and nonsignificant.
Performance of S1 Progenies from a Sorghum Random‐Mating Population Sampled in Different Years1
Authors: Ross W. M. , Hookstra G. H.
Published: July 2010

Samples of 200 S1's each taken from the same random‐mating sorghum [Sorghum bicolor (L.) Moench] population in 3 different years were evaluated as S1 progenies for agronomic and grain protein traits for 2 years in a blocks‐in‐repllcatlons design to determine the effect of different seasons and different personnel on sampling. Means, family and family ✕ year variances, heritabilities, predicted gains from selection, and genetic correlations were determined from the three samples. The results were related to expected plant breeding progress, particularly recurrent selection. Significant differences were obtained among the three sample means for each of seven traits, except tillerlng. The ranges of differences between sample means were small, however, and of little plant breeding importance. Family variance components differed little among the three samples for all traits except hcight and tillering. These two traits also had relatively large family ― year variance components compared to their respective family variance components. Variability in height was attributed to drought that suppressed height during years of sampling but which was expressed during more favorable years of evaluation. Genetic correlations among the same pair of traits tended to be similar in the three samples, but there were four nonhomogeneous sets. Broad‐sense heritabilities, calculated from plot means, and predicted gains from selection for each trait were similar in each of the three samples and indicated that S1's sampled any year from the same base population could be used for family recurrent sclectlon with expectation of essentially the same progress.
A Cytogenetic Basis for Transferring Russian Wildrye from Elymus to Psathyrostachys1
Authors: Dewey D. R. , Hsiao C.
Published: July 2010

Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski, is a native grass of the Asian interior, but it has become in important range grass in western North America where it is known as Elymus junceus Fsisch. The purposes of this investigation were 1) to determine the genome relationships between Russian wildrye and Psathyrostachys fragilis (Boiss.) Nevski, and 2) to determine the appropriate taxonomic treatment of Russian wildrye. After several unsuccessful attempts, Russian wildrye was hybridized with P. fragilis in 1979. The parents and hybrids were diploid, 2n=14. More than half of the Metaphase‐I cells in the F1 hybrids contained seven bivalents, demonstrating that the genomes of Russian wildrye and P. fragilis are closely homologous. The hybrids produced up to 5% stainable pollen, thus permitting introgression between the parent species. The cytogenetic data leave no doubt that Russian wildrye and P. fragilis are closely related and should be placed in the same genus, Psathyrostachys. The appropriate name for Russian wildrye is therefore P. juncea. European and Asian taxonomists are using this name, which should also be accepted in North America.
Inheritance of Brown Leaf Spot Resistance in Smooth Bromegrass1
Authors: Berg C. C. , Sherwood R. T. , Zeiders K. E. , Hill R. R.
Published: July 2010

Smooth bromegrass (Bromus inermis Leyss.) cultivars are susceptible to brown leaf spot (Pyrenophora bromi [Died.] Drechs.); however, some plants have smaller lesions than others. We studied inheritance of lesion size because there was no previous information on inheritance of resistance to brown leaf spot. Ten parent clones differing in lesion size were reciprocally single crossed with parent clone 11. The 10 parental clones were also polycrossed. Greenhouse‐grown parents and progeny were inoculated with conidia of P. bromi and rated for lesion size in November 1979. Regrowth was inoculated and rated in January 1980. Reciprocals were not statistically different. Four parental clones were more resistant than parent 11 in at least one of the two trials, but the F1 progeny of two of these clones were significantly more susceptible than the midparent (mean of clone 11 and the single cross parent). Five other parental clones were more susceptible than clone 11, and F1 progeny of two of them were more susceptible than the midparent. Polycross progeny means did not differ from polycross midparent means or were slightly lower in 2 of 20 observations. The results indicated that lesion size is regulated by multiple genes, and that susceptibility may be dominant or epistatic to resistance. There was a significant entry ✕ date interaction believed to be attributable to environment before and after inoculation. Developing populations with high levels of resistance to brown leaf spot will be difficult.
Weed Control on Warm Season Perennial Grass Pastures with Clovers1
Authors: Evers G. W.
Published: July 2010

Spring weeds in perennial grass pastures compete for limited nutrients and moisture and may lower palatability of the available for age. Mowing and a limited number of herbicides are the principal available methods of control in established pastures. Cool season clovers, which emerge in the fall and form a solid canopy during the winter, should have a competitive advantage over spring weeds. ‘Coastal’ bermudagrass (Cynodon dactylon (L.) Pers.) and ‘Pensacola’ bahiagrass (Paspalum notatum Flugge) sods were 1) overseeded with ‘Yuchi’ arrowleaf (Trifolium vesiculosum Savi.) or ‘Mt. Barker’ subterranean (Trifolium subterraneum L.) clovers, 2) fertilized with 0, 84, 168, 252, or 336 kg N/ha or 3) fertilized with 0, 84, and 168 kg N/ha and sprayed with 1.1 kg/ha of simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine]. Simazine substantially reduced spring weed yields to less than 500 kg/ha on Coastal bermudagrass and 200 kg/ha on Pensacola bahiagrass. Weed production on grass sods overseeded with clovers was not significantly different from the simazine treated plots. By the second year, weeds were essentially elimated from the plots overseeded with clover. These data demonstrate that clovers can play a major role in integrated pest management programs for warm season perennial grass pastures.
Long‐Term Pollen Storage of Pearl Millet1
Authors: Hanna W. W. , Wells H. D. , Burton G. W. , Monson W. G.
Published: July 2010

The purpose of this research was to develop a practical method for long‐term pollen storage of pearl millet (Pennisetum americanum L. Leeke). Pearl millet pollen with 7.5% moisture stored for 185 days in plastic zip‐lock bags at –73 C gave 100% seed set when used to pollinate cytoplasmic male sterile (cms) ‘Tift 23DA’ heads. Pollen dried to 2.2% also gave 100% seed set on cms heads after 129 days of storage. Frozen pollen with 6 to 7% moisture content that was thawed for 3 hours, refrozen, and later used in crosses produced 100% seed set.
Stomatal Frequency and Stomatal Resistance of Maize Hybrids Differing in Photosynthetic Capability1
Authors: Gaskell M. L. , Pearce R. B.
Published: July 2010

Stomatal frequency (Sf) and stomatal resistance (r2) have been inconsistently related to CO2 exchange rate (CER). We evaluated field‐grown maize (Zea mays L.) hybrids variable in leaf CER to determine if these CER differences might be related to Sf and/or r2 differences. Six experimental maize hybrids were selected on the basis of previously observed high or low relative leaf CER. Plants were sown in the field on Clarion (Typic Hapludoll) soils during the 1978 and 1979 growing seasons. Adaxial surfaces of leaves subtending uppermost developing ears were measured for r2 and Sf on three consecutive days shortly after silking. The high‐CER group of hybrids exhibited lower r2 and greater Sf than low‐CER hybrids both years. Stomatal frequency and resistance relative ranking within CER groups changed from year to year, but the relationships between groups of maize hybrids remained consistent. It is concluded that breeding programs for CER enhancement may be associated with inadvertent selection for lower r2.
Relationship Between Nutritional Quality Characters and Grain Yield in Pearl Millet1
Authors: Kumar K. A. , Gupta S. C. , Andrews D. J.
Published: July 2010

Before selecting genotypes for such quality characteristics as protein or amino acid contents, it is important to know how such selection is likely to affect yield. Using a diverse range of germplasm grown over seasons, locations and years, the relationships that exist between protein content, dye binding capacity (DBC) per unit protein (an estimate of the basic amino acids in protein), grain yield and grain size in pearl millet [P. americanum (L.) Leeke] were investigated. Protein content was estimated as total N ✕ 6.25, total N being measured with an automatic analyzer. Basic amino acid content was estimated using the Udy DBC technique. Grain yield and protein content were not significantly correlated and the relationship between grain yield and DBC/protein was nonsignificant and negative. The relationship between protein and DBC/protein was strongly negative. These results suggest that in pearl millet it should be possible to select for increased protein content or basic amino acid content (of which lysine is the most important) by monitoring levels of lysine and protein, respectively, without detrimental effect on grain yield or grain weight.
Inheritance of Resistance of PI 94587 Wheat to Biotypes B and D of Hessian Fly1
Authors: Stebbins Nancy B. , Patterson F. L. , Gallun R. L.
Published: July 2010

The resistance of PI 94587 wheat (Triticum turgidum L. durum group) to biotype D of Hessian fly [Mayetiola destructor (Say)] was studied at the tetraploid and hexaploid chromosome levels and to biotype B of Hessian fly at the tetraploid chromosome level. Progenies of selfed BC1 or testcross plants were infested with biotypes B or D of Hessian fly at 20 ± 2 C. Chi‐square goodness‐of‐fit tests were used to test genetic hypotheses. Recombination frequencies and standard errors were determined using the maximum likelihood method.Test cross analysis of the resistance of PI 94587 to biotype D of Hessian fly strongly suggests two independent dominant genes. Test cross plant progenies susceptible to biotype D of Hessian fly were retested to biotype B of Hessian fly using reserve seed. It was probable that two genes (one in addition to the H6 gene) or three were segregating in the test cross progenies. Thus, PI 94587 may have four or five independent dominant genes for resistance to the Hessian fly. Three common wheat selections resistant to biotype D of Hessian fly were derived from crosses between cultivar ‘Riley’ or Purdue breeding line 5724B3‐5P‐8‐2 and PI 94587. They are selections 916, 920 and 941. All three selections have a common dominant gene for resistance from PI 94587. This gene was linked 4.40 ± 1.78 map units from the H5 gene in ‘Abe’ wheat and was designated H11.
Relationship Between Tillering and Forage Yield of Tall Fescue. I. Yield1
Authors: Zarrough Khames M. , Nelson C. J. , Coutts J. H.
Published: July 2010

Little information exists regarding the influence of tiller density on yield of forage grass swards, but tiller density has been shown to be associated positively with yield of spaced plants. Therefore, three field experiments were conducted on developing and developed swards to evaluate the relationship between tiller density and forage yield of tall fescue (Festuca arundinacea Schreb.). Genotypes were selected that displayed high (HYT) medium (MYT) and low yield/tiller (LYT). As spaced plants, these genotypes were known to have a slow, medium, and rapid rate of tiller development, respectively. Plots were established in early spring from vegetative tillers and were allowed to develop into swards. Cutting heights of 5 and 10 cm above ground level were compared, and in one experiment the genotypes were grown with birdsfoot trefoil (Lotus corniculatus L.) to evaluate their competitive ability. All plots were cut four times during the growing season. Before equilibrium tiller density was reached (when addition of new tillers offset death of others), a close relationship existed between forage yield and tiller density. However, in all experiments, forage yield was closely associated with yield/tiller once tiller density approached equilibrium and tended to stabilize. Under those conditions, the highest yielding genotype of tall fescue was the one characterized by low tiller density and high yield/tiller. Increasing cutting height from 5 to 10 cm did not affect tiller density, but did increase yield/tiller and forage yield for the season. This difference was probably due to residual leaf area remaining on the stubble after cutting. Birdsfoot trefoil grown in a mixture with the HYT genotype was 26% more productive than when grown in a mixture with the LYT genotype of tall fescue. Selection of tall fescue for high tiller weight and reduced rate of tillering may be beneficial for grass grown alone and for use in mixtures with legumes.
Relation of Verital Root‐Pull Resistance and Flowering in Maize1
Authors: Kevern T. C. , Hallauer Arnel R.
Published: July 2010

Interest in development of maize (Zea mays L.) roots has increased the past 20 years because of the incidence of maize rootworms (Diabrotica species) in the U.S. Corn Belt. Objectives of our study were to determine whether preflower root‐pull resistance was related to postflower root‐pull resistance and whether preflower root‐pull resistance should be included in recurrent selection programs to enhance resistance to root lodging. We evaluated 98 Sj progenies derived from each of four populations at two locations for 3 years for rootpull resistance and at one location for 3 years for frequency of root lodging. The S, progeny heritability estimates for pre‐ (76%) and postflower (81%) root‐pull resistance and root lodging (74%) were relatively high, suggesting that progress could be made for each trait. Genetic correlations between pre‐ and postflower root‐pull resistance ranged from 0.78 to 0.90, but the average genetic correlations between preflower (r = − 0.20) and postflower (r = −0.28) root‐pull resistance and percentage of root lodging were relatively low. Predicted correlated response of postflower root‐pull resistance based on preflower root‐pull resistance was 81.3% (23.9 kg) of predicted direct response (29.4 kg) for postflower root‐pull resistance. Though correlated responses of root‐pull resistance for resistance to root lodging were only 35.5% (postflower) and 25.8% (preflower), greater resistance to root pulling would contribute to reduced root lodging. Our results suggest preflower root‐pull resistance was a good predictor of postflower rootpull resistance and that effective selection can be made at flowering for increased root‐pull resistance.
A Photoperiod and Temperature Sensitive Period for Leaf Number of Maize1
Authors: Tollenaar M. , Hunter R. B.
Published: July 2010

The heat unit concept, e.g. Growing Degree Days, is used extensively to account for temperature effects on maize (Zea mays L.) development in models which attmept to predict crop development and yield. Environmental effects on rate and duration of leaf initiation, which determine final leaf number, have received much less attention in such models, although leaf number and the period from planting to silking are highly correlated for maize. Photoperiod and temperature are two environmental variables known to affect leaf number. The objective of this study was to delineate the sensitive period during which leaf number of the short‐season maize hybrid, Guelph GX 122, is influenced by photoperiod and temperature. Periods during which leaf number was influenced by temperature and photoperiod were determined by transferring plants to different photoperiod/temperature regimes at various stages of vegetative development. Leaf number was determined at tassel emergence and, in two of three experiments, leaf stage at which tassel initiation occurred was estimated by dissection of plants at regular intervals. All experiments were conducted in the environmentally controlled growth cabinets of the University of Guelph. Results of these experiments indicate that initiated leaf number of Guelph GX 122 was influenced by temperature between the five‐ and the seven‐leaf stage and by photoperiod betweenthe four‐ and the seven‐leaf stage. The transition from vegetative to reproductive development (i.e., tassel initiation) occurred a leaf stage which was numerically equal to 50% of final leaf number. Photoperiod and temperature effects on leaf number were additive for Guelph GX 122 grown under the conditions of these experiments.
Performance of Non‐Nodulating and Nodulating Soybean Isolines in Mixed Culture with Nodulating Cultivars1
Authors: Burton J. W. , Brim C. A. , Rawlings J. O.
Published: July 2010

Nodulating and non‐nodulating soybean isolines were grown in mixed culture with six nodulating soybean cultivars to determine if non‐nodulating plants would benefit from an association with nodulating plants. All seed mixtures were half isoline and half cultivar at planting. Pure cultures of the isolines and cultivars were included in the experiments. At maturity, seed yield, seed size, and protein and o11 concentration were determined for each component of the mixed cultures and for each pure culture. The average performance of the non‐nodulated component of the mixture was 38% greater than the average yield of the non‐nodulated line in pure culture. Likewise, protein concentration and total protein were 13 and 56% greater, respectively, in the non‐nodulated lines that were grown in mixed culture with nodulated cultivars. Considering the amount of available soil N at planting and competition of the cultivars for that N, the additional N accumulated by the non‐nod in mixture may have come from other than soll sources. It is likely that N was lost from the nodulated plants either through the sloughing and decomposition of root and nodular tissue and/or through the direct excretion of nitrogenous compounds from the roots. Evidence that the cultivars differed with respect to the amount of N lost, suggests that the trait could be changed with selection and breeding methods.
Application of GOSSYM to Genetic Feasibility Studies. II. Analyses of Increasing Photosynthesis, Specific Leaf Weight and Longevity of Leaves in Cotton1
Authors: Landivar J. A. , Baker D. N. , Jenkins J. N.
Published: July 2010

The model GOSSYM was used to demonstrate how a computerized crop simulation model can be used in a breeding or agronomic research program to simulate the performances of genotypes with different physiological response when grown under various environmental conditions. Results of simulating a cotton (Gossypium hirsutum L.) crop with higher leaf photosynthetic rate indicated that cotton lint yield could be increased up to 54% by increasing photosynthetic rate by 30%, providing that adequate N and water were available. With 30% increase in photosynthetic rate the high water (375 mm) input outyielded the low water (186 mm) treatment in both 56 and 112 kg/ha of N treatment, however, no difference in lint yield was obtained between the water regimes at 336 kg/ha of N. Maturity was delayed in the higher water treatment. Simulation results indicated a higher N requirement to obtain maximum lint yields with a cultivar having increased photosynthetic rate. It was concluded that if the increased CO2 exchange rate observed in a genotype were associated with increased specific leaf weight, more of the CO2 fixed would be used in the production of thicker leaf rather than lint production. This suggests caution in using specific leaf weight to select indirectly for higher leaf photosynthetic rates in cotton. Keeping the leaves photosynthetically active for a period of up to 70 days resulted in a higher leaf area index (LAI), the crop intercepted a higher fraction of the incoming solar radiation, and produced a higher lint yield. This seems to be a more promising characteristic to be used as criteria in a breeding or agronomic research program oriented toward increasing lint yield.
Barley Yellow Dwarf Virus Translocation in Wheat and Oats1
Authors: Carrigan L. L. , Ohm H. W. , Foster J. E.
Published: July 2010

We studied the translocation of barley yellow dwarf virus in two soft red winter wheats (Triticum aestivum L. em. Thell.) and three spring oat (Avena sativa L.) cultivars and lines. Plants grown under ample soil moisture or moisture stress were infected with a local field collection of barley yellow dwarf virus. Nonviruliferous (test) aphids were then attached to sampling sites on emerging and fully emerged leaves at various times after infection. Virus movement was similar for all cultivars in our test. Virus was transferred to test plants from each sample site in each cultivar. As the plants grew, virus could be detected in the leaves before they elongated fully. Less than 24 hours were required for translocation of the virus throughout the plant. Based on results of this study the systemic translocation of barley yellow dwarf virus is probably not a useful measure of host plant resistance or tolerance.
Comparison of Genetic Models for Inbreeding in Autotetraploids Using Maize Data1
Authors: Rice J. S. , Dudley J. W.
Published: July 2010

In an attempt to clarify inbreeding depression in autotetraploids, three models for inbreeding depression were compared using data from autotetraploid maize (Zea mays L.). Generations included were S1 through S4 and full‐sib generations 1 through 6. The first genetic model was μ1 = μ + 6Fβii + (4P0 + P1)γiii + P0δiii + P2δiijj (Gallais). The second model (Hill's) was μ1 = μ + pq(D + 2pT + p2,Q) + Pq(q ‐ P) (T + pQ) + pQ) + p2q2Q. Hill's model can be applied with or without assumptions about the origin of the parents for the inbreds. It was fit with the assumption of a source population in random mating equilibrium in this study except for a comparison involving four selfed generations. The third model fit the first four powers of F (coefficient of inbreeding). Deviations from fitting powers of F were significant in 10 of 20 cases while deviations from the other models were significant in only four. Thus, the F model was considered unsatisfactory. Comparison of Hill's model with no assumption of equilibrium with Gallais' model and Hill's model with assumption of equilibrium revealed no significant differences. Although no clear evidence from fits to data favored either model, it appears reasonable to conclude that Gallais' model or Hill's model assuming equilibrium is more appropriate when the source population was at equilibrium and that Hill's model without assumptions may be more appropriate when the equilibrium assumption is not possible.
Effect of Pink Bollworm on Agronomic Properties of Resistant and Susceptible Cotton1
Authors: Wilson F. D. , George B. W.
Published: July 2010

Little is known about the differential effects of the attack of pink boilworm (PBW), Pectinophora gossypiella (Saunders), on agronomic properties of resistant and susceptible cottons, Gossypium spp. The major objective of this study was to determine and compare those effects in a susceptible cultivar and a resistant breeding stock of upland cotton, G. hirsutum L., and a susceptible cultivar of Pima cotton, G. barbadense L. Other objectives were to compare an x‐ray method with a visual boll‐grading method of determining damage done by the insect, and to study the relationship of seed damage with selected agronomic properties. The three cottons were grown for two seasons in untreated field plots and in plots treated for PBW control Seed cotton was harvested weekly as boils opened, seed samples were x‐rayed to determine seed damage, and agronomic properties were measured. At the end of the season, all bolls were removed from five plants/plot and boils were graded into damage classes. Pink bollworm mainly damaged rather than destroyed seed. Damaged bolls did not abscise but remained on the plant. The Pima entry, ‘Pima S‐5’ had more dry, unharvestable bolls than the two upland entries, ‘Deltapine 61’ and AET‐5. Damage was higher in unsprayed than in sprayed plots. The resistant AET‐5 had less seed damage and fewer damaged bolls than the other two entries, and its agronomic properties were less affected by PBW attack. The x‐ray method failed to integrate data from unharvestable bolls, and the graded‐boll method failed to quantify the amounts of damage in the damaged‐boll category. The percentages of variation in decreases in agronomic properties, attributable to increases in seed damage, were higher in unsprayed than in sprayed plots, but also differed among the three cottons. Thus, direct comparison of the effects of PBW on agronomic properties among cottons in unsprayed plots could be misleading because these effects would be superimposed on different natural patterns of decrease in those properties as the season progressed.
Recurrent Selection in Soybeans. IV. Selection for Increased Oleic Acid Percentage in Seed Oil1
Authors: Burton J. W. , Wilson R. F. , Brim C.A.
Published: July 2010

Soybean [Glycine max (L.) Merr.] oil is the major edible vegetable oil that has a high endogenous level of linolenic acid. Natural oxidation of linolenic acid produces chemical intermediates which cause poor oil flavor. An expensive hydrogenation process is required to lower the concentration of linolenic acid to an acceptable level. Because of this, a plant breeding project was begun to reduce the percentage of linolenic acid in soybean oil. The selection criterion was high oleic acid percentage which is negatively correlated with linolenic acid percentage. A soybean population was developed by mating six lines with relatively high oleic acid percentage to the genetic male‐sterile (ms1ms1) maintainer line, N69‐2774. Four cycles of recurrent mass selection for increased oleic acid were conducted in the population. In the fourth cycle, mass selection was followed by within half‐sib family selection. In each cycle segregation of the male‐sterile trait within the population permitted cross matings to occur naturally between selected male‐sterile and male‐fertile plants by insect pollination. Progress due to selection was evaluated by growing the selected lines from each cycle in replicated tests in six environments. Results of these tests show that oleic acid percentage of the soybean oil increased linearly from 24.8 to 33.0%. The correlated trait, linolenic acid percentage, decreased linearly from 7.8 to 6.3%. In addition, the linoleic acid level declined from 53.3 to 47.0%. Changes in stearic acid percentage were not correlated with cycles of selection. Realized heritability (h2) for oleic acid percentage was 0.21 ± 0.06. There was a significant interaction between environments and cycle populations. The effect of that interaction, however, was expressed as differences in the magnitude of oleic acid percentages in the different environments rather than differences in ranking. Hence, selection for oleic acid percentage in soybean oil may not be compromised severely by environmental interaction.
Quantification of Specific Gene Interaction Effects between Populations Utilizing Diallel Information1
Authors: Hanson W. D.
Published: July 2010

Specific gene interactions associated with crosses are usable in corn (Zea mays L.) breeding programs. Analyses developed to quantify these gene interactions utilized diallel information among populations. A spatial relationship was developed where one axis resolved additive gene effects and additional axes as needed resolved dominance‐associated gene interaction effects. A diversity analysis weighed differences in gametic frequencies by nonadditive interaction effects found among populations, while a complementation analysis emphasized interactions effects found between groups of populations. Techniques for pooling information from different sources and for reducing dimensions were discussed. Least‐square estimates for coordinates, which permitted presentation in reduced dimensions, were developed. These analyses should be useful for evaluating the complementation of local breeding material by introduced germplasm and the changes in populations resulting from long‐term selection programs. The complementation of two North Carolina maize, Zea mays (L.), varieties (cultivars) by a Mexican race, ‘Tuxpeño’, was investigated where genes for adaptation were introduced from these two local varieties. Major favorable gene complementation of these local germplasms by genes introduced from Tuxpeño was found and was a consistent feature for two environments. Tuxpeño was sufficiently diverse from these two North Carolina varieties so that integration with these local varieties to obtain a gene pool for adaptation left considerable residual diversity. Replicate selections diverged for genes affecting both additive and dominance associated effects even though populations of 40 plants were intermated for each cycle of selection.
Stand Density, Shoot Weight, and Acetylene Reduction Activity of Alfalfa Populations Subjected to Field and Greenhouse Moisture Gradients1
Authors: Rumbaugh M. D. , Johnson D. A. , Rinehart D. N.
Published: July 2010

The objective of this study was to determine if selection of alfalfa (Medicago falcata L. and M. sativa L.) for increased forage yield has resulted in increased seedling stand density, shoot weight, and acetylene reduction rate in favorable environments but corresponding decreases in these characteristics in less favorable environments. Thirty‐eight alfalfa populations were divided into four groups differing in origin, breeding, and adaptation. They were grown in replicated field experiments in 2 successive years as well as in the greenhouse. Line‐source sprinkler systems were used to provide a range of water applications. Stand densities of alfalfa populations in the seedling year were related to the degree of selection by plant breeders but also were dependent upon water availability. Modern cultivars had higher stand densities of seedlings in more favorable environments, but exhibited lower stand densities than wild populations when subjected to increased moisture deficits. Shoot weight of field‐grown plants was also closely related to the intensity of breeding effort with the most highly bred cultivars achieving greater shoot weights than wild populations at all water applications. In the high moisture application treatment in the field in 1980, acetylene reduction activity was positively associated with the degree of agronomic selection of the populations. In the greenhouse environment the acetylene reduction activity of dryland pasture and range populations exceeded those of other types of alfalfas (P<0.05). However, we found no quantitative evidence of superior stand density, growth, or acetylene reduction activity of these dryland pasture and rangeland populations in their seeding year when grown in the field. At least for the seedling stage, the most highly bred germplasm would be more desirable for source material to improve shoot weight in either optimum or suboptimum environments than wild populations. Use of highly bred germplasm also would probably be most effective if the breeding objective is to increase field N2 fixation and stand density at the seedling stage in favorable water environments.
N2 Fixation (C2H2) and Ureide Content of Soybeans: Environmental Effects and Source‐Sink Manipulations1
Authors: Patterson T. G. , LaRue T. A.
Published: July 2010

The use of ureides as an indirect index of symbiotic N2 fixation requires an understanding of how their relationship is influenced by environmental factors. Source‐sink manipulation (leaf or pod removal) and environmental factors (time of day, light intensity, root anaerobiosis, and soil nitrate) were tested for their effects on acetylene reductiona ctivity (ARA) and ureide concentration in the shoot. In soybeans [Glycine max (L.) Merr.] there was no significant diurnal variation of stem ureide concentration. Inhibition of ARA by root anaerobiosis reduced ureide concentrations in both xylem sap and stem tissue. Ureide concentrations in xylem sap reflected decreased N2 fixation more rapidly than concentrations in stem tissue. The ureide content of stem tissue apparently responds more slowly to a reduction in ARA. Partial leaf removal or a reduction in light intensity reduced ARA. Defoliation increased concentrations of ureides in the stem. Loweringli ght intensity had no effect on stem ureide concentrations, but increased leaf ureide concentration. Pod removaldid not affect ARA but increased the concentrations of ureides in the stem. In the field, addition of 30 kg N ha‐1 had little influence on ARA or ureide content of young stem or first stem internodes. Higher nitrate levels (100 and 200 kg N ha‐1) greatly reduced both ureide concentration and ARA.
Effects of Photoperiod and Temperatures on the Duration of Vegetative Growth in Maize1
Authors: Russell W. K. , Stuber C. W.
Published: July 2010

One objective of this study was to identify parental genotypes to be used in subsequent research into the inheritance of sensitivity to photoperiod in maize (Zea mays L.). Seventy inbreds were surveyed for their maturity responses under two photoperiods in a phytotron greenhouse. For short‐day maturity, a range was observed from 10.0 leaves for C3 to 23.0 leaves for Tx601. For photosensitivity (difference between long‐day and short‐day maturity), the range extended from 0.0 leaves for B14A to 8.5 leaves for CM103. The correlation between short‐day maturity, and photosensitivity across all entries was significantly positive, but among inbreds exhibiting moderate or late short day maturity, a large range in photosensitivity occurred. The maturity responses of seven inbreds were further examined in growth chambers primarily to study photoperiod ✕ temperature interactions and to compare two measures of maturity in maize. Based on days to tassel initiation (DTI) and particularly total leaf number (TLN), the effect of photoperiod was considerably greater than that of temperature. Photoperiod ✕ temperature interactions were significant only for DTI. Total leaf number (TLN) was concluded to be better than DTI for measuring effects of photoperiod upon the duration of vegetative growth in maize. Several other results with important implications for subsequent research on the inheritance of photosensitivity in maize are discussed.
Genetic Improvement in Minnesota‐Adapted Oat Cultivars Released Since 19231
Authors: Wych R. D. , Stuthman D. D.
Published: July 2010

Increased crop yields over the past 50 to 100 years have been attributed to new cuitivars and improved cultural and management practices. Documentation of the contribution of plant breeding to oat (Avena sativa L.) yield improvement may provide insights into the optimum strategy for attaining further gains. Our objective was to quantify genetic improvements in grain yield, kernel quality, and associated agronomic and physiological traits of oat cultivars grown in Minnesota over the past six decades. Nine cultivars released since 1923 were grown in field experiments at St. Paul, Minn. in 1979 to 1981. Mean grain yield over all years ranged from 20.0 q/ha for ‘Anthony’, to 31.3 q/ha for ‘Moore’. Based on the mean yield of ‘Gopher’, the annual rate of increase since 1923 was 0.8%. Newer cultivars generally lodged less than older cultivars, which may also contribute to the increases in harvestable grain yield obtained in commercial fields today. Cultivars differed in groat percentage, but no trend with time of release was evident. The collective improvement in both grain yield and, to a lesser extent, groat percentage, resulted in an annual rate of increase in groat yield of 0.9%, slightly higher than that for grain yield. Kernel weight has increased over time, while the number of kernels per unit area has generally decreased. Newer cultivars thus reflect the emphasis that has often been placed on selection for yield and kernel quality and size. Biological yield, harvest index, total N (in groats plus straw), groat N, and N harvest index (NHI) were all greater newer cultivars, linearly related to cultivar age, and positively correlated with grain yield. Higher groat protein yield of modern cultivars was primarily a reflection of the gains in groat yield and improvement in NHI or N partitioning.
Linkage Relationships in Soybean Between Genes Controlling Reactions to Phytophthora Rot and Metribuzin1
Authors: Kilen T. C. , Barrentime W. L.
Published: July 2010

Linkage between desirable and undesirable genes increases the population sizes required to recover preferred gene combinations and hinders the progress of breeding programs. The soybean [Glycine max (L.) Merr.] cultivar Tracy is resistant 15 of the 20 identified races of Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin, but it also has an undesirable gene conferring sensitivity to the herbicide metribuzin [4‐amino‐6tert‐butyl‐3‐(methylthio)‐as‐triazin‐5(4H)‐one]. The objectives of this study were to determine the inheritance of sensitivity to metribuzin found in Tracy, to determine if the genetic basis for sensitivity in Tracy was related to that previously described in ‘Semmes’, and to examine possible linkage relationships between genes for phytophthora rot resistance and metribuzin sensitivity. The results suggest that the sensitivity to metribuzin in Tracy is controlled by the same recessive gene, hm, that controls sensitivity to metribuzin in the cultivar Semmes. A combined recombination estimate of 7% between genes Rps1 (for phytophthora rot resistance) and Hm was determined from repulsion and coupling crosses which suggests close linkage between the two loci.
Simultaneous Stem Diameter Expansions and Apoplastic Electropotential Variations Following Irrigation or Rainfall in Cotton1
Authors: Gensler W. , Diaz‐Munoz F.
Published: July 2010

Temporary and permanent expansions of the stem diameter result from rainfall and irrigation of cotton under field conditions. This study is concerned with the simultaneous use of physical and invasive electrochemical sensors to monitor the timing of these expansions. The measurements were made over three seasons and have yielded a set of generalizations concerning the timing and magnitude of the expansions. The plant begins expansion during the night and/or next night following irrigation and/or rainfall. At the onset of the expansion there is a large magnitude precipitous drop in electropotential. Both the physical expansion and the electropotential drop are systemic, i.e., they occur simultaneously at widely separated parts of the plant. Several possible mechanisms giving rise to the physical and electropotential variations are discussed.
Inheritance of Kernel Number Per Spikelet and Its Association with Kernel Weight in Two Winter Wheat Crosses1
Authors: Ibrahim Osman E. , Ohm H. W. , Nyquist W. E. , Cantrell R. P.
Published: July 2010

Inheritance of kernel number per spikelet in wheat (Triticum aestivum L. em. Thell.) was studied using F3 families and parental, F1, backcross F1, and F2 populations from the crosses, ‘Benni’ ✕ ‘Sullivan’ (cross 1) and Benni ✕ ‘Sava’ (cross 2). Benni has a larger number of kernels compared to current soft red winter wheat cultivars. The joint scaling test indicated that the additive‐dominance model was inadequate for cross 1 and that epistasis could be one of the possible causes. However, the additive‐dominance model was adequate for cross 2. Broad‐sense heritability estimates were 0.41 and 0.27 for crosses 1 and 2, respectively, suggesting sizable environmental effects. Narrowsense heritability estimates were 0.18 and 0.14 for crosses 1 and 2, respectively, indicating relatively small additive effects. Four and eight effective factors were estimated to control kernel number/spikelet in crosses 1 and 2, respectively. Negative nonsignificant phenotypic association between kernel number/spikelet and 200‐kernel weight was observed. The genotypic correlation was not significantly different from zero, and simultaneous improvement of the two traits is not likely to be difficult.
Comparative Performance of Obsolete and Current Cotton Cultivars1
Authors: Bridge Robert R. , Meredith W. R.
Published: July 2010

The purpose of this study was to evaluate current and obsolete cotton (Gossypium hirsutum L.) cultivars and determine the rate of gain in cotton yields in Mississippi. We evaluated 17 cultivars on a Bosket sandy loam (fine‐loamy, mixed, thermic, Mollic Hapludalf) over a 2‐year period (1978 and 1979) to determine what genetic improvements the new cultivars had over the older ones. The study was comprised of two recently released cultivars (‘Stoneville 825’ and ‘DES 56’), 14 obsolete cultivars, and ‘Stoneville 213’. Stoneville 213 was released in 1962 but still accounts for approximately 12% of the cotton acreage in Mississippi. The two recently released cultivars produced significantly higher yields than the other cultivars. The obsolete cultivars produced 100 to 700 kg/ha less lint than the cultivars currently grown. The average rate of yield increase from 1910 through 1979 due to cultivar improvement was found to be 9.46 kg/ha/year. A regression analysis of the average lint yields in Mississippi from 1910 through 1979 shows that yields have actually increased at the rate of 8.62 kg/ha/year. Since 1965 yields have gradually decreased in spite of a genetic potential for increased yield. These data substantiate the fact that the inherent yielding ability of cultivars is not responsible for declining yields.