bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Relations in Winter Wheat as Drought Resistance Indicators
Authors: Schonfeld Manette A. , Johnson Richard C. , Carver Brett F. , Mornhinweg Dolores W.
Published: July 2010

Although drought is recognized as an important limitation to wheat (Triticum aestivum L.) production in many regions, drought resistance selection techniques are not adequately developed. In 1984–1985 and 1985–1986, field experiments were conducted in Stillwater, OK, to determine potential drought resistance parameters and their inheritance in winter wheat. Single plants of drought resistant ‘TAM W‐101’ and drought susceptible ‘Sturdy’, their F1 and F2 progeny, and backcrosses of the F1 to each parent were evaluated under a rain shelter. Tiller number was recorded throughout the growing season. As stress developed during reproductive development, water potential (WP), solute potential (SP), turgor potential (TP), relative water content (RWC) were measured at 7‐ to 10‐d intervals on single leaves until tlag leaf senescence. Tiller number and growth rate were similar among the six populations. Water potential, WP components, and RWC declined with increasing drought stress, but no significant differences among populations were found, in WP, SP, or TP. Relative water content differed significantly among populations under increasing drought stress. TAM W‐101 maintained a higher RWC under drought conditions than Sturdy, and had a longer grain‐filling period. Comparison of the RWC values among populations indicated that differences were controlled predominantly by genes with additive effects. Narrow‐sense heritability (h2) of RWC increased as drought stress intensified and reached a maximum value of 0.64 1 wk prior to flag leaf senescence. With this high h2, RWC shows promise as a selection criterion for drought resistance in winter wheat.
Leaf Senescence and Seasonal Decline in Nutritional Quality of Three Temperate Forage Grasses as Influenced by Drought
Authors: Bittman S. , Simpson G. M. , Mir Z.
Published: July 2010

Growth of cool season grasses in the northern Great Plains occurs mainly in the spring, and summer pasture consists of mature, quiescent, and drought‐affected vegetation. This study was conducted to determine drought effects on leaf'stem ratio, leaf senescence, and nutritional quality of three grasses, ‘Parkway’ crested wheatgrass [Agropyron cristatum (L.) Beauv. spp. pectinatum (Bieb.) Tzvel.], ‘Magna’ smooth bromegrass (Bromus inermis Leyss.), and ‘Prairieland’ Altai wildrye [Leymus ungustus (Trin.) Pilger] commonly grown on the northern Great Plains. The grasses were grown in the field on deep black soil (Meifort silty clay, Typic Cryoboroll) at Melfort, Saskatchewan under two moisture regimes: plots subjected to drought (DRY) were covered by rain out shelters starting at the end of May; and irrigated (IRR) plots were watered when soil water potential averaged −0.07 MPa. Altai wildrye maintained its quality through the season (as indicated by N, P, in vitro digestibility, and lignin) better than the other species because it had the lowest proportion of stems and least leaf senescence. Crested wheatgrass had the lowest quality from June to August because it had the greatest leaf senescence and highest proportion of stems. Water deficit (DRY plots) increased the rate of seasonal decline in N and P concentration probably by increasing leaf senescence. However, drought reduced the seasonal decline in digestibility by reducing the rate of increase in acid detergent fiber and lignin. Drought increased leaf senescence more in floral than in nonfloral tillers, suggesting that leaf senescence was controlled hormonally. Because leaf senescence was lower in nonfloral than in floral tillers, the quality of midsummer pasture may be improved by introducing cultivars having a high proportion of nonflowering tillers.
Heterosis and Isozyme Divergence in Indica Rice
Authors: Peng J. Y. , Glaszmann J. C. , Virmani S. S.
Published: July 2010

Earlier studies conducted in China indicated an association of heterosis in rice (Oryza sativa L.) crosses with certain esterase and peroxidase isozyme patterns. To search for methods that predict yield heterosis in hybrid rice breeding program at IRRI, we studied isozyme variation of 18 rice cultivars (seven maintainers and 11 restorers of ‘WA’ cytosterility system) and 75 F1, hybrids derived from these parents to determine the relationship between yield heterosis in the F1s and isozyme diversity among their parents. Isozyme variation among parental lines was found for six genes, viz., Est‐9, Est‐2, Amp‐3, Sdh‐1, Pgi‐2, and Pgd‐1. Midparent heterosis for yield ranged from −44.6 to 156.7%. Our studies did not show any association between magnitude of heterosis in F1s and isozyme variation among parents. The reason our results differed from those reported in China may be because most of the parental lines used in our studies were elite rice cultivars bred at IRRI from complex crosses involving parents of various geographic origin that allowed extensive recombination among genes. Consequently, linkage disequilibrium between isozyme markers and gene blocks involved in heterosis for yield might have disappeared.
Influences of Selection Method and Nitrogen Environment on Breeding Alfalfa for Increased Forage Yield and Quality
Authors: Teuber Larry R. , Phillips Donald A.
Published: July 2010

Alfalfa (Medicago sativa L.) can use both mineral N and N2 when effective Rhizobium bacteria are present. Our group previously increased dry matter and N assimilation in unadapted alfalfa germplasm sources by using independent culling levels to choose individual plants with high forage dry weight and N concentration when grown sequentially under N2‐ and NH4NO3‐dependent conditions. The objectives of the present study were (i) to assess the potential of other selection methods for improving forage yield and protein content, (ii) to evaluate the need for screening under both N2‐ and NH4NO3‐dependent conditions, and (iii) to test whether the original breeding protocol could be applied successfully to agronomically adapted germplasm. First, data from ‘Moapa 69’ plants grown sequentially under N2‐ and NH4NO3‐dependent conditions were used for simulated selection of single and multiple traits in each N environment. Results predict that single trait selection will produce undesirable changes in the unselected trait and that independent culling levels will increase forage dry weight and N concentration in both N environments. The greatest progress was made with a base index selection system, but this system required an excessive number of N determinations. Second, small populations were developed from Moapa 69 using independent culling levels to select for high forage dry weight and increased forage N concentration in plants grown under N2, NH4NO3, or a sequence of N2‐ and NH4NO3‐dependent conditions. After two cycles of phenotypic recurrent selection, the resulting germplasm pools were evaluated for growth on both N2 and NH4NO3. Sequential selection on N2 and NH4NO3 increased forage dry weight more than 24% on both N sources (P < 0.10); selection only on NH4NO3 increased forage dry weight significantly (P ≤ 0.10) only under NH4NO3‐dependent conditions; but selection only on N2 did not improve forage dry weight in either N environment significantly (P ≤ 0.10). Forage N concentration was not increased by selection in either N environment. Finally, large populations from Moapa 69 grown sequentially on N2 and NH4NO3 were synthesized through three cycles of phenotypic recurrent selection using independent culling levels for high forage dry weight and greater N concentration. The third cycle population produced 54% more forage dry weight (P < 0.001) with 9% higher forage concentration (P < 0.001) and 67% more total crude protein (P < 0.001) than the original Moapa 69 in results averaged across both N environments in the glasshouse. The conclusion from these studies is that selection for dry weight and N concentration must be done on both N2 and NH4NO3 dependent environments to develop alfalfa with increased forage yield and higher crude protein concentration in both N environments under glasshouse conditions.
Inheritance of Rosette‐Raceme in Guar
Authors: Stafford R. E.
Published: July 2010

Abnormal plants occur from time to time in cultivated fields of guar [Cyamopsis tetragonoloba (L.) Taub]. Abnormalities due to genetic change have potential for use as genetic markers in a breeding program. A mutant having a rosette‐raceme and reduced fertility was found in a released breeding line, TX76‐328S, growing near Hluwe in Natal, South Africa. Inheritance of the rosette‐raceme trait was investigated. Rosette‐raceme was found to be inherited as a monogenic recessive and is expressed on every raceme. The name rosette‐raceme and the gene symbol, ros, are proposed for the new mutant trait. This trait should be useful in genetic studies as an easily identifiable phenotype.
Mechanical Mass Selection Methods for Improvement of Oat Groat Percentage
Authors: Souza E. J. , Sorrells M. E.
Published: July 2010

Three methods of mechanical mass selection for seed density, aspiration (ASP), gravity table selection (GT), and gravity table selection with a seed polishing pretreatment (P‐GT), were evaluated and compared for effectiveness of increasing caryopsis (groat) percentage and test weight in oat (Avena sativa L.). Selection using these methods in two heterogeneous F5 populations resulted in absolute differences in the groat percentage between high and low density treatments of 0.3 and 0.5% for ASP and P‐GT, respectively. The GT selection resulted in a lower groat percentage in the high‐density treatment. Selection methods interacted with populations and seed size classes. These interactions were due to different levels of variation in the populations for seed size and shape. Two cycles of selection for high groat percentage beginning in F3 segregating bulk populations showed little overall improvement. Selection increased the number of fertile florets per spikelet. This increase in fertility was due primarily to a 22% increase in tertiary florets per panicle per cycle of selection. Tertiary floret number exhibited a negative genotypic correlation with groat percentage, which limited improvement for groat percentage. There also were significant changes in plant height, days to flowering, and harvest index in these experiments with direction and magnitude dependent on the individual population. Effectiveness of mechanical mass selection for groat percentage could be increased by avoiding selection for characters such as tertiary kernels which have undesirable correlated effects on milling quality.
Field and Greenhouse Evaluations of Stem Canker Resistance in Soybean
Authors: Weaver D. B. , Sedhom S. A. , Smith E. F. , Backman P. A.
Published: July 2010

Greenhouse screening using infested toothpicks was compared to field evaluation of soybean [Glycine max (L.) Merr.) breeding lines for resistance to stem canker disease, caused by southern strains ofDiaporthe phaseolorum (Cke. & E11. (Sacc.) var. caulivora Athow and Caldwell (Dpc). Field screenings are reliable indicators of resistance, but often the disease does not develop naturally in field screening nurseries. Thirty‐seven random F4:6 lines from the cross ‘Hutton’ (susceptible ) ✕ ‘Tracy M’ (resistant) were evaluated for their reaction to Dpc in the field (two locations, 2 yr) under natural infestation and infection conditions, and in the greenhouse (three experiments) with artificial inoculation using infested toothpicks. Our objectives were to compare field and greehouse screening and to determine the usefulness of greenhouse inoculation in predicting the yield and disease reaction of breeding lines when these lines were subjected to natural field infection conditions. Field screening based on symptoms and yield was highly effective in identifying resistant genotypes. Heritabilities for yield and disease ratings in the field were 87 and 92%, respectively. The toothpick inoculation procedure used in the greenhouse was effective with each of three Dpc isolates (different in geographic origin from the field location) in identifying the genotypes that showed highest levels of disease resistance in the field. Phenotypic correlations between greenhouse ratings and yield in the infested field ranged from −0.71 to −0.61. Results indicated that selection based on greenhouse screening can be an effective alternative to field screening when resistance is derived from Tracy M.
Fatty Acid Composition of the Oil in Reciprocal Crosses among Soybean Mutants
Authors: Erickson E. A. , Wilcox J. R. , Cavins J. F.
Published: July 2010

The genotype of the embryo, maternal parent, or cytoplasm may influence the expression of seed composition traits in soybean [Glycine max (L.) Merr.]. The objective of this study was to evaluate the above effects on the genetic control of fatty acid composition of the oil of six recently identified soybean mutants. Fatty acid composition of soybean oil was determined from seed of reciprocal F1 and F2 populations produced from crosses among the six soybean mutants and the parent, ‘Century’. Differences were consistently present for oleic and linoleic acid percent in seed from reciprocal crosses. These differences were due to maternal influence rather than to cytoplasmic inheritance. The genotype of the embryo also affected levels of oleic and linoleic acid in these mutants. No differences were observed for palmitic or stearic acid percentages in any reciprocal crosses or for linolenic acid percentage in two of three reciprocal crosses. Determining fatty acid composition of individual F2 seeds from F1 plants is appropriate for inheritance and selection studies of palmitic, stearic, and linolenic acid percentages, but not of oleic and linoleic acid percentages in crosses with these mutant lines.
Field Comparison of Dinitrogen Fixation Determined with Nitrogen‐15‐Depleted and Nitrogen‐15‐Enriched Ammonium Sulfate in Selected Inbred Backcross Lines of Common Bean
Authors: St. Clair D. A. , Wolyn D. J. , DuBois J. , Burris R. H. , Bliss F. A.
Published: July 2010

The field determination of N2 fixation by 15N‐isotopic methods provides a direct and precise measure of N2 fixation. Since 15N‐enriched fertilizers are expensive, 15N‐depleted (NH4)2SO4 was used as a more economical, readily available alternative to determine N2 fixation in common bean, Phaseolus vulgaris L. The objectives of this study were to determine whether 15N‐depleted (NH4)2SO4 provided reliable estimates of relative differences in N2 fixation among bean lines comparable to those obtained using 15N‐enriched (NH4)2SO4, and whether nine previously selected progeny lines differed from their respective recurrent parents for N2 fixation ability. The nine progeny lines and three parents were grown in two randomized complete block field experiments that were treated identically except that each experiment received only one of the two 15N fertilizers. Lines were harvested at an early reproductive stage (R3) and maturity (R9), partitioned into plant parts, and the 15N and total N yield of the tissue determined. The two 15N fertilizers produced comparable differences among lines at the R9 stage based on significant genotypic rank correlations between the two experiments, and similar fertilizer use efficiency values (% FUE). Three of the five selected progeny lines from population 24 fixed significantly more N2 than their recurrent parent ‘Sanilac’. The four progeny lines from population 21 were not significantly different from or less effective in N2 fixation than their recurrent parent ‘Porrillo Sintetico’, therefore, either previous selection based on indirect measures of N2 fixation was not effective, or the two parents did not differ genetically for N2 fixation. In all progeny and parental lines, seed N2 fixed was positively rank correlated with plant N2 fixed, and the highest N2‐ fixing lines in both populations had more fixed N2 in the seeds than did low N2‐fixing lines.
Effects of Recurrent Selection in Corn Populations
Authors: Rodriguez Omar A. , Hallauer Arnel R.
Published: July 2010

Recurrent selection methods were conducted in corn (Zea mays L.) populations to increase the frequency of favorable alleles for grain yield. Populations under recurrent selection were evaluated to estimate response to selection and to compare the relative effectiveness of the different methods of recurrent selection for grain yield improvement. Ten populations, their improved strains, and the S1 generation of the original and improved strains were evaluated in four field environments. This study was conducted to estimate the direct and indirect responses to selection of the 10 populations and their respective S1 generations for different methods of selection. Positive response to selection for greater grain yield was realized for each selection method except for one population (BSCB1) undergoing reciprocal recurrent selection. Average response (0.249 Mg ha−1 cycle−1) for the intrapopulation selection methods was greater than the average response (0.033 Mg ha−1 cycle−1) for the interpopulation selection methods. Response in the S1 generations was similar to the response of the noninbred populations. Reduction in inbreeding depression averaged 12%. The S1 generations of two selected populations [BS13(S)C4 and BS12(HI)C7] had significantly greater yields than the nonselected, noninbred populations from which the selected populations were derived. Positive response to selection was accomplished without selection for taller, later‐maturity genotypes. No consistent trends were detected for changes in root and stalk lodging with selection for grain yield.
Effectiveness of Index Selection for Switchgrass Forage Yield and Quality
Authors: Godshalk E. B. , Timothy D. H. , Burns J. C.
Published: July 2010

Index selection has been proposed as an effective method to improve agronomic traits in switchgrass (Panicum virgatum L.), but the actual effectiveness of this selection tool has not been determined. The objective of this research was to ascertain the efficacy of the estimated index when used to improve switchgrass forage yield and in vitro dry matter disappearance (IVDMD). Three populations were generated by selection on the basis of three different sets of criteria: (i) increased yield, with IVDMD and nitrogen concentration (N) as covariates, (ii) increased yield and IVDMD, with N as a covariate, and (iii) increased IVDMD, with yield and N as covariates. Selections were made among a total of 660 Cycle 1 plants, designating 16 plants to comprise each of the three index‐derived populations. The resulting groups of plants were allowed to open‐pollinate in isolation and their progeny (Cycle 2) were evaluated for forage yield and quality traits. Comparisons were made among the three groups and also with a set of 15 plants randomly chosen to represent the Cycle 0 population. Significant differences were found among the three Cycle 2 groups for yield, in vitro dry matter disappearance (IVDMD), acid detergent fiber, and neutral detergent fiber. Only the third group, selected for increased IVDMD, had regrowth IVDMD that was significantly greater than that of the Cycle 0 population. Gains in IVDMD were possible, but not without reduced gains in forage yield. Yields of Indices 1 and 2 were significantly greater than the Cycle 0 population yield for both initial growth and regrowth. Canonical discriminant analysis demonstrated the value of the three selection indices in separating the Cycle 2 population into distinct subpopulations with differing attributes. Selection indices were shown to be effective in obtaining moderate increases in trait means and in tailoring switchgrass populations with desired forage production characteristics.
Responses of Glasshouse Grown Cotton to Irrigation with Carbon Dioxide‐Saturated Water
Authors: Mauney J. R. , Hendrix D. L.
Published: July 2010

Experiments were conducted to test the suitability of using irrigation water as a carrier for CO2 to enhance growth and productivity of cotton (Gossypium hirsutum L.). Potted plants (‘DPL 61’) were irrigated daily with CO2‐saturated water in a greenhouse in Phoenix, AZ. Growth, productivity, and physiological responses of these plants were compared to those irrigated with deionized water. All plants were fertilized twice weekly with a modified Hoagland's solution. Yield as measured by boll load at maturity was increased 70 and 53% in two sets of experiments. Carbon dioxide exchange rate (CER) was increased 38%. Leaf chlorophyll content and starch content were also increased. None of the carbon in lint samples was derived from the CO2 in the irrigation water. Leaf Zn and Mn were deficient in the control plants but were sufficient in the plants watered with CO2‐saturated water. The CO2‐saturated irrigation water increased uptake of Zn and Mn, which supported a more robust photosynthetic apparatus in the treated compared to the control plants. The greater photosynthetic activity during boll loading resulted in a significant increase in yield of the treated plants.
Variation in Forage Component Composition and In Vitro Digestion of Creeping Bluestem
Authors: Brown W. F. , Kalmbacher R. S.
Published: July 2010

Creeping bluestem [Schizachyrium scoparium (Michx.) Nash var. polycladus (Scribner & Ball) Bruner (S. stoloniferum Nash)] is predominant, high yielding range grass native to Florida; however, in vitro organic matter digestion (IVOMD) is low. This research investigated IVOMD variation in 200 creeping bluestem ecotypes grown on an area of Onka Fine Sandy (sandy, siliceous, Hyperthermic Typic) and Myaxxa Fine Sand (sandy, siliceous, hyperthermic Arenic Haplaquod) soils. Ecotypes were collected from peninsular Florida, and space planted in a nursery. Plants were staged to 150 mm stubble in March 1984 and 1985 and the forage discarded. In late June of each year while plants were vegetative, leaves from each ecotype were hand harvested (150 mm stubble), and analyzed for IVOMD, which ranged from 350 to 642 g kg−1. (P < 0.001). Fifteen ecotypes with four replications in each of 2 yr (120 samples), representing the range in IVOMD, were selected to determine relationships between IVOMD and both concentration and in vitro digestion of fibrous components. A linear relationship (P < 0.05) existed between IVOMD and acid detergent lignin (ADL; r −0.66) concentration. A quadratic relationship (P < 0.05; r = 0.66) was found between IVOMD and in vitro hemicellulose (HC) digestion, indicating that HC was not the major structural component limiting IVOMD of creeping bluestem. In vitro rate of neutral detergent fiber (NDF) digestion was not related to IVOMD (P > 0.05; r = 0.14); however, lag time was shortest (P < 0.05; r = −0.74) ecotypes highest in IVOMD. Regression coefficients for relationships between in vitro digestion of OM, NDF, acid detergent fiber, and HC vs. ADL concentration were negative and significant for the linear contrast. In vitro lag time was highest for ecotypes highest in ADL. In conclusion, variation exists in IVOMD of creeping bluestem ecotypes found in Florida, and appears to be due primarily to the inhibitory effects of lignin on the initiation and extent of forage digestion.
Quantitative Translocation of Photoassimilates from Nonsurviving Tillers in Barley
Authors: Chafai‐Elalaoui A. , Simmons S. R.
Published: July 2010

Many tillers produced in barley (Hordeum vulgure L.) crop communities senesce without bearing grain. To better understand the physiological and agronomic implications of this tiller mortality, partitioning of photoassimilate by nonsurviving tillers was monitored for field‐grown plants at St. Paul, MN on a Waukegan silt loam soil (fine‐silty over sandy or sandy‐skeletal, mixed Typic Hapludoll). Primary tillers formed in the axils of the first and second main shoot leaves (designated T1 and T2, respectively) were labeled with 14C02 on four occasions and the labeled plants sampled at 7‐ to 10‐day intervals. Some labeled tillers were immediately girdled using steam to restrict photoassimilate export and permit estimation of radioactivity losses due to tiller respiration. Knowing the respiratory losses as well as the quantity of radioactivity remaining in a labeled tiller following a given translocation period, the proportional 14C export from the tiller was calculated. These estimates were coupled with changes in tiller dry mass to calculate the photoassimilate dry matter transferred from a tiller between labeling dates, which were summed to give the cumulative dry matter translocated during the entire period of labeling. Nonsurviving T1 tillers translocated 45% of their photoassimilate to other plant parts, which equated to approximately 150 mg of dry matter. These tillers retained 17% and respired 38% of their fixed radioactivity. Nonsurviving T2 tillers exported 57% (approximately 40 mg), retained 20%, and respired 23%. Most photoassimilate exported from nonsurviving tillers was recovered in the main shoot stem, with lesser amounts in the main shoot spike and leaves. Nonsurviving primary tillers may contribute substantial amounts of dry matter for growth of other plant parts, particularly the main shoot. Thus, initiation of such tillers may not be inherently wasteful of plant photoassimilates.
Plant Density and Soybean Yield
Authors: Egli D. B.
Published: July 2010

The spacial distribution of plants in a crop community is an important determinant of yield. However, the mechanisms responsible for the observed responses to changing plant density are not well understood. Field experiments utilizing a systematic design that made it possible to evaluate a wide range of plant densities in a single experiment were conducted with an indeterminate (‘Cumberland’‐ 2 yr) and a determinate (‘Pixie’‐1 yr) soybean [Glycine mar (L.) Merrill]. Population densities used in the analyses varied from 0.6 to 24 plants m−2. At low population densities, where there was no interplant competition, yield increased in direct proportion to increases in plant density. At plant densities providing interplant competition, the rate of yield increase was reduced. Yield of the indeterminate cultivar increased as plant density increased above the density required for 95% insolation interception at growth stage R5. The increase in yield was a result of increases in seed m−1 in both years along with seed size in 1985. However, the determinate cultivar exhibited maximum yield at the plant density that provided 95% insolation interception at growth stage R5. The data for the indeterminate cultivar confirms a recently published theoretical analysis of soybean yield responses to plant density. The data suggest that plant densities higher than those required to maximize insolation interception by growth stage R5 may be required for maximum yields of indeterminate cultivars.
Seed and Soil Treatments to Improve Emergence of Muskmelon from Cold or Crusted Soils
Authors: Bradford Kent J. , May Donald M. , Hoyle Burton J. , Skibinski Z. Stan , Scott S. Jeffrey , Tyler Kent B.
Published: July 2010

Cold soil temperatures, seedling diseases, and soil crusting may limit stand establishment of early‐season muskmelons (Cucumis melo L.). We tested the ability of seed and soil treatments to overcome these factors and improve seedling emergence. The seed treatments were seed priming (6 d at 25 °C in aerated 0.3 M KNO3 solution followed by drying) to improve the rate of germination at low temperatures, and metalaxyl [N‐(2,6‐dimethylphenyl)‐N‐(methoxyacetyi) alanine methyl ester] fungicide (Apron 25W) to prevent damping‐ off diseases. The soil treatments were spot applications of soil drenches containing metalaxyl fungicide (100 μg L‐1 Ridomil 2E), an anticrostant [2% Naico 2190, (Nalco Chemical Corp, Carson, CA)] or both fungicide and anticrustant. In laboratory tests at 18 °C, both germination rate and final germination were markedly improved by seed priming in ‘PMR 45’, ‘Magnum 45’, ‘Topmark’, and ‘Topscore’ plants. Seedling emergence from sterilized soil in flats under ambient outdoor temperatures (7‐23 °C) was also improved by seed priming. Seed priming resulted in more rapid emergence or increased final emergence in five of seven field trials in two locations. Anticrustant applications to the soil covering the seed consistently improved stand establishment, particularly in badly crusted soils. Metalaxyl application to the seed or soil generally improved emergence, but the effect varied with cultivar, location, and planting method. None of the treatments significantly influenced final fruit yield. The combination of seed priming, fungicides, and anticrustants could allow lower seeding rates of expensive hybrid seed while achieving earlier emergence and adequate plant densities in earlyseason muskmelon crops.
Yield Earliness, and Fiber Properties of Cotton Carrying Combined Traits for Pink Bollworm Resistance
Authors: Wilson F. Douglas
Published: July 2010

The nectariless (N) and okra‐leaf (L) traits confer low levels of resistance in cotton, Gossypium hirsutum L., to pink bollworm (PBW), Pectinophora gossypiella (Saunders). The semi‐smoothleaf (SS) trait reduces the amount of leaf trash in mechanically harvested seedcotton. The main objective of this study was to compare NL (or NSSL) isolines with N (or NSS) isolines and with check cultivars for resistance to PBW, lint yield, earliness, and fiber properties. The experiments were grown at three locations: Tempe, AZ; Maricopa, AZ; and Brawley, CA. In three experiments grown without the use of insecticide, two of the six NL (or NSSL) isolines (DES 56NL and DES 24NSSL) had significantly less seed damage caused by PBW, did not yield significantly less lint, were significantly earlier, and had deficient to comparable fiber properties when compared with the N counterpart isolines. The Stoneville 825 NL isoline yielded significantly more lint and had fiber properties comparable to the N isoline, but was not earlier and did not have less seed damage. All N, NL, NSS, and NSSL lines that were compared with nectaried, regular‐leaf cultivars sustained less seed damage, and most were equal in lint yield and earliness. In a fourth, insecticide‐treated experiment, DES S6NL required fewer insecticide applications, had significantly less seed damage, and was earlier maturing than the nectaried, regular‐leaf ‘Deltapine 61’ (DPL‐61) at two locations, and yielded more lint at one location. Fiber of DES 56NL was shorter, weaker, and coarser, but had elongation strength equal to that of DPL‐61. In three of the four experiments, some year ✕ cotton and location ✕ cotton interaction effects were significant. Thus, in spite of some deficiencies in properties and performance, cotton germplasm lines are becoming available that combine PBW resistance with yield potential, earliness, and fiber properties that approach or equal those traits in cultivars
Variation among Inbred Lines of Maize for Leaf Surface Wax Composition
Authors: Blaker T. W. , Greyson R. I. , Walden D. B.
Published: July 2010

Arising from an interest in the degree to which leaf surface wax could be used as a marker for the identification of genetic lines and cultivars of maize (Zea mays L.), this study explored wax variability among five inbred lines (A619, B73, OH43, VA26, and W23) as revealed by gas chromatography. Individual leaves of the five inbred lines were excised from plants harvested at or near anthesis. The surface wax was extracted by a chloroform dip, samples were dried in vacuo and stored at −5°C until analysis. The composition of leaf surface wax varied among the inbreds. The chromatographic patterns of A619 and OH43 were indistinguishable from each other, while the waxes of B73 and W23 differed slightly. The wax of VA26 was the least similar to the waxes of the other inbreds. Different statistical treatments [Analysis of Variance (ANOVA), Principal Components Analysis (PCA), and Average Linkage Clustering (ALC)] of the data derived from gas chromatographic analyses were successful in arranging individual leaves into their inbred groups, with the exception of A619 and OH43. The between inbred variation suggested that leaf surface wax composition can be a suitable character for some inbred characterizations if developmental and leaf number‐based differences are taken into account.
Cultivar and Clonal Differences for Water‐use Efficiency and Yield in Four Forage Grasses
Authors: Barker R. E. , Frank A. B. , Berdahl J. D.
Published: July 2010

Available water is a major factor limiting productivity of forage grasses grown in the northern Great Plains of the USA. Cultivars with greater water‐use efficiency (WUE) would be beneficial to forage production and utilization in this semiarid region. Our objective was to assess variability in forage yield and WUE among genotypes of four common forage grasses. Four clones with contrasting phenotypes were selected from each of three cultivars or strains of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Shult.], western wheatgrass [Pascopyrum smithii Rybd. (Löve)], intermediate wheatgrass [Thinopyrum Intermedium (Host) Barkworth and Dewey], and reed canarygrass (Phalaris arundinacea L.). Soil water content was determined by neutron probe for 5 yr on clonal plots grown on a Parshall sandy loam soil (coarse‐loamy, mixed Pachic Haploboroll) near Mandan, ND. A single forage harvest was taken each year when plants were at soft dough stage of seed development. Forage yield and WUE increased the first 2 yr of the study, then decreased for the next 2 yr. Increases and decreases in forage yield were associated with total available water (soil water plus growing season precipitation) prior to harvest and effects of stress in one year on subsequent years. There were no significant (P≥0.05) differences among entries for total water used before harvest. Environmental effects (years and replications) on yield and WUE in each species were large compared with genotypic effects. Genotypic mean squares were from 2 to over 35 times larger than experimental error mean squares for yield and WUE. Broad sense heritability estimates ranged from 71 to 95% for yield and from 69 to 94% for WUE over the four species, which indicated that gain from selection may be possible. However, because of the large year effects, extensive testing will be necessary to evaluate yield and WUE in the four grasses we studied. Development of more effective screening techniques will be necessary to reduce resource input required for evaluating WUE.
Selection for Tolerance to Root‐Knot Nematodes in Red Clover
Authors: Quesenberry K. H. , Baltensperger D. D. , Dunn R. A. , Wilcox C. J. , Hardy S. R.
Published: July 2010

Susceptibility to root‐knot nematodes (Meloidogyne spp.) is one of the major factors limiting production and persistence of cool season forage legumes in the sandy soils of the southeastern USA. The objectives of this research were to evaluate Florida adapted red dover (Trifolium pratense L.) germplasm for response to root‐knot nematodes, to determine the effectiveness of greenhouse recurrent selection for tolerance to root‐knot nematode, and to develop a red clover population with increased levels of root‐knot nematode tolerance. Syn 2 plants from each of five cycles of restricted recurrent phenotypic selection (RRPS) for early vigor in a root‐knot nematode infested field were evaluated in the greenhouse for response to Meloidogyne arenaria (Neal) Chitwood race 1 (MA), M. incognita (Kofold and White) Chitwood race 3 (MI), and M. javanica (Treub) Chitwood (M J). The most tolerant plants from these evaluations were used to initiate three half‐sib family populations selected for tolerance to MA, MI, and MJ. These populations were carried through two cycles of recurrent half‐sib family selection in the greenhouse and progress was evaluated in a final greenhouse evaluation. Field RRPS for early vigor decreased root gall scores 0.20, 0.33, and 0.26 units per cycle and decreased egg mass scores 0.42, 0.32, and 0.30 units per cycle (1–5 rating scale) when the cycles were infested with MA, MI, and M J, respectively. Two additional cycles of greenhouse haif‐sib family selection lowered gall score 0.45 and 0.31 units per cycle in the MA and MJ populations, respectively, but only 0.16 in the MI population. Egg mass scores were decreased an average of 0.49 units per cycle over the three populations. Mean egg mass scores decreased more than mean gall scores. Additional selection may be necessary to develop red clover germplasm that will suppress field nematode populations and produce well in fields infested with high root‐knot nematode levels.
Gas Exchange, Carbon Isotope Discrimination, and Chloroplast Ultrastructure of a Chlorophyll‐Deficient Mutant of Cowpea
Authors: Kirchhoff W. R. , Hall A. E. , Thomson W. W.
Published: July 2010

Chlorophyll‐deficient mutants provide an opportunity for studying relationships among chlorophyll composition, chloroplast ultrastructure, and plant function. A chlorophyll‐deficient mutant of cowpea [Vigna unguiculata (L.) Walp.] and its normally pigmented parent were grown in glasshouse and field conditions. The chlorophyll (a + b) content of the mutant was 35 to 48% less per unit leaf area and the chlorophyll a:b ratio was 62 to 74% greater than the parents. Chloroplasts of the mutant had distended thylakoids and substantially reduced granal stacking, supporting the hypothesis that chlorophyll content, chlorophyll a:b ratio, and chloroplast lamellar organization are developmentally related. The mutant had significantly higher CO2 assimilation rates per unit leaf area (+13%) at high photon flux densities and a quantum requirement that was not significantly different from the parent. Apparently, the mutant's ability to assimilate CO2 was not adversely affected by the substantial changes in chlorophyll content and composition, and chloroplast ultrastructure, compared with the parent. Significant differences in 13C discrimination for leaves sampled from field‐grown plants led to the prediction that plants in a drier treatment had higher intrinsic water‐use efficiency than well‐watered plants, which was consistent with significant differences observed in leaf gas exchange by the same plants. The mutant had significantly greater 13C discrimination than the parent; however, leaf gas exchange data indicated no significant differences in intrinsic water‐use efficiency.
Late Season Alfalfa Plantings: Conventional vs. No‐Till Methods
Authors: Wolf D. D. , Edmisten K. L.
Published: July 2010

Fall establishment of alfalfa (Medicago saliva L.) in locations such as southwest Virginia (37 ° N, 80 ° W, and 600 m elevation) is often not possible by conventional methods because of the difficulty in meeting currently recommended planting deadlines. This usually results from unfavorable weather, a need to utilize a previous crop for an extended time, or the removal of a corn crop for silage. The objective of this study was to establish a recommended date for late‐season no‐till alfalfa planting as an alternative to conventional methods so that plantings need not be delayed until the following spring. Alfalfa was planted on 1, 10, 20, 30 September, and 10 October 1982, 1983, 1984, and 1985 using conventional and no‐till procedures. Soils were Groseclose (clayey, mixed, mesic Typic Hapludults) with 3 to 7% slopes. Excellent stands were achieved by mid‐December from both conventional and no‐till procedures regardless of planting date. Seedling survival during the winter decreased with delay in planting after 1 September, with less loss occurring with no‐till than conventional plantings. Each 10‐d delay in planting after 1 September caused a 6.8‐d delay in first harvest date the following spring beyond the mid‐May cutting date resulting from the 1 September planting. These data support a recommendation that no‐till planting can be made 3 wk later in the growing season than is possible with conventional methods. This extra latitude will allow flexibility when unavoidable delays in planting may occur and where the previous crop cannot be removed early enough to permit successful conventional planting.
Callus Induction and Differentiation from Leaf Explants of Different Species of the Genus Beta
Authors: Yu M. H.
Published: July 2010

The noncultivated Beta species are a potential source of germplasm for sugarbeet (B. vulgaris L.) improvements, yet their in vitro regeneration has rarely been explored. This study was conducted to determine the regeneration ability of beet species across all four sections of the genus Beta. Leaf explants from 16 germplasm sources were cultured on MS basal medium containing N6‐benzyladenine (BA). Accessions showed large differences in response to the medium. There was a positive association between leaf expansion and callus formation. Leaf explants from nine Vulgares and Corollinae species that became highly swollen generally produced a larger mass of callus than that of Nanae and Patellares. A large amount of callus was induced in B. vulgaris L., B. maritima L., B. intermedia Bung., and B. macrocarpa Guss, Callus formed in more than one cycle; when it was maintained without subculture 10 of the 14 species formed secondary callus on the darkened, senescing primary callus. Rooting occurred with nine species, none belonging to Nanae or Patellares. Shoots were regenerated only with B. vulgaris and B. macrocarpa. Explants from most Beta species exhibited optimum callus formation and differentiation at 31 °C; however, at 33 °C only B. atriplicifolia Rouy, B. lomatogona Fisc. et Mey., and B. intermedia responded. To induce in vitro regeneration of the diverse Beta germplasm, other growth regulators in addition to BA and 1‐Naphthaleneacetic acid (NAA) should be explored.
Modified S1 Recurrent Selection in Maize Improvement
Authors: Dhillon B. S. , Khehra A. S.
Published: July 2010

In intrapopulation improvement, S1 recurrents election is widely used. The objective of this study was to propose a method of a modified S1 recurrent selection for use in maize (Zea mays L.), and to use the expected genetic gain from the modified method for comparison with other methods of intrapopulation improvement. Three growing seasons are usually required for completing one cycle of S1 recurrent selection. In the proposed method, the evaluation and recombination phases were combined. The selection was assumed to have been practiced among and within S1 families. This modification enables the completion of one cycle of selection in two growing seasons only. This reduces, from two to one, the number of years required per cycle, provided off‐season nurseries can be used. Under certain situations, one cycle of modified S1 selection alternated with one cycle of half‐sib selection can be completed in a year. The genetic gains per year from the proposed methods were expected to be greater than those from other methods of intrapopulation improvement.
Polyploids from 2x‐4x and 4x‐2x Crosses in Red Clover
Authors: Taylor Norman L. , Berger Sandy
Published: July 2010

Efficient methods of producing tetraploids are important to red clover (Trifolium pratense L.) breeders. An effort to widen the genetic base of tetraploid experimental lines via gametic nonreduction provided an opportunity to further examine this methodology. The objectives of this research were to further evaluate the frequency of triploid and tetraploid progeny from 2x‐4x and 4x‐2x crosses in red clover, and to examine the use of seed dockage sieves as a labor saving device in separating polyploid from diploid seeds. A few triploids were found among progenies from 2x‐4x crosses in contrast to our earlier research, but the frequency was considerably lower than from 4x‐2x crosses. Tetraploids were more frequent among progeny of the 4x‐2x cross than progenies from 2x‐4x crosses. Isolation of polyploid seeds was facilitated by sieving seeds and growing only those from the larger sieve sizes. The most efficient method of producing both triploids and tetraploids was by 4x‐2x crosses rather than by 2x‐4x crosses. However, a leaf mark or other gene marker is necessary to eliminate tetraploid selfs.
Genetics of Resistance of PI 422297 Durum Wheat to the Hessian Fly
Authors: Obanni M. , Ohm H. W. , Foster J. E. , Patterson F. L.
Published: July 2010

The durum wheat (Triticum durum Desf.) PI 422297 was selected for genetic studies because of its resistance to Biotypes B, C, D, and L of the Hessian fly, Mayetiola destructor (Say). The objectives of this study were to determine the number of genes controlling the resistance of PI 422297 to Biotype D, and to establish the allelic relationships or independence of these genes to currently known genes that confer resistance against this biotype. This experiment was conducted in a controlled environment chamber maintained at 19 ± 2 °C. In testcross analyses, random selfed BC progeny rows between the susceptible parent D6647 and PI 422297 indicated that two genes controlled the expression of this resistance; these two genes are independent of H5, H9, H10, H14, H15, and H17. No fully susceptible progeny rows were observed in the crosses involving H11 and H16 together, or H16 singly, with the two genes in PI 422297. However, the level of resistance of the PI 422297 genes at 26 °C indicates that a linkage or allelic relationship is involved between one gene in PI 422297 and H16. Therefore, one of the two genes in PI 422297 is different from all previously known genes for resistance to Biotype D. We designate this gene as H19. The other gene is associated with H16. Additional research is planned to determine whether the second gene of PI 422297 that confers resistance to biotype D of Hessian fly is allelic or linked to H16.
Composition and Forage Yield of Hybrid‐Inbred Mixtures of Pearl Millet
Authors: Burton Glenn W.
Published: July 2010

In repeated tests, ‘Gahi‐1’ pearl millet [Pennisetum glaucum (L.) R. Br.] seed containing 75% of F1 hybrid and 25% of selfed and sibbed seed yielded as much forage as double‐cross (100% F1) seed involving the same four inbreds. Even mechanical mixtures containing 50% of hybrid and 50% of inbred seed failed to significantly reduce pure hybrid forage yields. It was assumed that this happened because the more vigorous hybrids crowded out the inbreds in the seedling stage leaving only hybrid plants to be harvested. The objectives of this study were to test this hypothesis by determining the fate of colored inbreds in mixtures containing various percentages of their seeds mixed with seeds of the green hybrid ‘Gahi‐3’, and to measure their effect on forage yield. Red and yellow plant inbreds yielding about 40% as much as Gahi‐3 were used in this study. for 2 yr, mixtures containing 20, 40, 60, and 80% of seeds of colored inbreds planted in hills (30 seeds/hill) yielded 101.7, 91.4,84.7, and 71.5% as much forage as pure hybrid seed. Only the 60 and 80% of colored inbred seed mixtures yielded significantly less (P < 0.05). Colored culms left per hill were 3.2, 4.6, 8.0 and 15.7, respectively. Planted in rows (210 seeds/in) for 3 yr, mixtures containing 20, 40, and 60% of colored inbred seeds yielded 104.0, 90.9, and 90.5% as much as pure hybrid seed. Colored culms in the row plots produced 1.5, 4.7, and 9.7% of the total forage, respectively. Reducing the seeding rate in row plots to 70 seeds/m of row lowered forage yields 14%, but only the 60% colored inbred seed mixture significantly lowered forage yields (P < 0.01).