bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub‐Okra, Semi‐Smoothness, and Nectariless Effect on Cotton Lint Yield
Authors: Meredith W. R. , Pettigrew W. T. , Heitholt J. J.
Published: July 2010

Combining all useful traits into a single genetic background does not always result in a genotype whose performance could be predicted by individual trait effects. Our objective was to evaluate the effects of three cotton (Gossypium hirsutum L.) traits, and their interactions with one another and environments. Sub‐okra leaf, semi‐smooth leaf, and nectariless were backcrossed into ‘DES 119’ from MD65‐11S. All eight combinations of the three traits were evaluated as BC4F4 and BC4F5 near isogenic populations in 1992 and 1993. They were grown at four locations near Stoneville, MS, in a randomized complete block design with six replications for yield and three for all other performance characteristics. No significant total yield response due to any trait was detected; however, sub‐okra leaf types produced significantly higher (35 kg ha−1 or 4%) first harvest yield than normal leaf types. Significant differences due to the main effects were detected for all other characteristics. Lint percentages for hairy and semi‐smooth types were 37.3 and 36.8, respectively. Fiber strengths for nectaried and nectariless isolines averaged 196 and 192 kN m kg‐1, respectively. Normal leaf had heavier bolls and seed, longer fiber, and lower fiber elongation than sub‐okra types. Seed of semi‐smooth isolines were heavier than those of hirsute cottons. Nectaried populations averaged larger bolls and seed, longer 2.5% span length, stronger fiber and higher elongation than that for nectariless populations. Interactions were smaller than the 1 to 4% differences detected for main effects. No major negative interactions among traits or with other environments were encountered. Incorporating these traits into one cultivar with similar genetic background to DES 119 should result in no major breeding problems.
Contribution of Individual Culms to Yield of Salt‐Stressed Wheat
Authors: Maas Eugene V. , Lesch Scott M. , Francois Leland E. , Grieve Catherine M.
Published: July 2010

Grain yield in wheat (Triticum aestivum L. emend. Thell.) is highly dependent upon the number of spike‐bearing tillers produced by each plant. Soil salinity can greatly decrease their number and productivity. Knowing the contribution of specific tillers is essential for breeding salt‐tolerant genotypes and for developing wheat growth simulation models. Our objective was to determine the effects of soil salinity on the contribution of individual culms to total grain and dry matter yields of two spring wheat cultivars, Anza and Yecora Rojo. Plants were grown in Pachappa fine sandy loam soil (mixed, thermic, Mollic Haploxeralf) in outdoor lysimeters for 2 yr. Three salinity treatments were imposed by irrigating with waters containing equal weights of NaCl and CaCl2 (electrical conductivities ≅ 1, 12, or 18 dS m‐1). Despite substantial losses in the number of tillers at moderate levels of salt stress, grain yields of the main stem (MS) and tillers Tl and T2 were as great or greater than those on nonstressed plants of both cultivars. The contribution of the MS to yield on a land area basis increased from about 25 to 35% in nonsaline treatments to over 80% with increasing salinity. The contribution of primary tillers ( ≅ 58‐65% in nonsaline conditions) decreased substantially only at the highest salinity levels. Salinity stress significantly decreased the number of spikelets per spike but the number of kernels per spike either increased or was unaffected except at the highest level of stress. Increasing salinity decreased total straw yields primarily because of fewer tillers, but dry weights of the MSs and remaining tillers were also smaller. Results show that loss of spike‐bearing tillers accounts for most of the yield reduction in salt‐stressed wheat.
Response of Cotton and Kenaf to Boron‐Amended Water and Soil
Authors: Bañuelos G. S. , Mackey B. , Cook C. , Akohoue S. , Zambrzuski S. , Samra P.
Published: July 2010

Well and drainage water with high B concentrations may be an alternative source of water for irrigated agriculture in the western USA. Irrigation water with even moderate levels of B may, however, be toxic to plants. Two greenhouse studies were conducted to evaluate the growth responses of kenaf (Hibiscus cannabinus L.) and cotton (Gossypium hirsutum L.) to B‐amended irrigation water (Experiment I) and B‐amendeds soils (Experiment II) irrigated with B‐free water. In Experiment I, both kenaf and cotton were irrigated with water amended with 7.5 mg B L‐1 as boric acid or with water containing <0.25 mg B L‐1. In Experiment II, B uptake and B tolerance were evaluated for kenaf and cotton grown at two different times in B‐amended soils (≈ 45 mg total B kg‐1 soil and 7 mg extractable B L‐1). In Experiment I, dry matter (DM) yield of both species was significantly reduced by B‐amendedw ater (P < 0.05 level). Compared with plants irrigated with control water, total DM yields were 50 and 30% lower for kenaf and cotton, respectively. Leaf tissue B concentrations ranged from 500 to 1400 mg B kg‐1 DM for kenaf and from 300 to 800 mg B kg‐1 DM for cotton. In Experiment II, growing kenaf and cotton in B‐amended soils reduced DM yield of kenaf and cotton 27 and 17%, respectively. Mean leaf tissue B concentrations were 422 mg B kg‐1 DM in kenaf and 222 mg B kg‐1 DM in cotton. Results show that high soil B in greenhouse pot conditions decrease DM production of kenaf and cotton.
Nitrate Uptake and Assimilation and Chlorate Tolerance of Wheat
Authors: MacKown C. T. , Van Sanford D. A. , Rothwell Christy G.
Published: July 2010

Productivity of nonlegume crops depends partly on nitrate uptake and reduction. To study the nitrate assimilation pathway of plants, the herbicide chlorate has been exploited as an analog of nitrate. Marked variations in visible leaf chlorosis among 15 soft red winter wheat (Triticum aestivum L.) seedlings exposed to 120 μM chlorate were reported by others. From their study, we selected three chlorate‐tolerant and three chlorate‐sensitive ranked cultivars and measured influx and assimilation of 15N‐nitrate to determine if these traits were related to differences in chlorate sensitivity. Effects of 120 μM chlorate on growth, leaf chlorophyll concentration, and nutrition were also quantified. The growth and chlorophyll levels of main stem oldest leaf blades decreased in the presence of chlorate in all cultivars except for one chlorate‐tolerant cultivar. Neither the level of tissue nitrate nor the influx and assimilation of 15N‐nitrate was related to chlorate sensitivities we observed, or those previously reported for the six selected cultivars. Chlorate toxic effects unrelated to nitrate assimilation and interactions between absorbed nitrate and chlorate and their compartmentation may alter the response of these cultivars to chlorate. Inferences that chlorate sensitivity of wheat is related to nitrate uptake and assimilation appeared to be inappropriate.
Factors Affecting a Laboratory Evaluation of Alfalfa Cold Tolerance
Authors: Schwab P. M. , Barnes D. K. , Sheaffer C. C. , Li P. H.
Published: July 2010

Currently, only test winter data are used to evaluate the winter hardiness of alfalfa (Medicago sativa L.) cultivars. A test winter is defined as field conditions severe enough to kill nonhardy cultivars and to cause varying degrees of winter injury to cultivars of intermediate hardiness. Due to the unpredictability of test winter occurrence, alternative methods are needed for predicting alfalfa winter survival. This research tested the effects of temperature stress, storage time, and plant size, measured as the width of the root at the crown‐root juncture, on a laboratory cold tolerance evaluation of field grown and hardened alfalfa plants. Plants were dug from the field in mid‐November and stored at −2°C until subjected to cold stresses from 0 to −24°C. Differences among entries were greatest at the −12 and −16°C cold treatments. Crown injury score was positively correlated with field fall growth (r = 0.91) and winter injury scores (r = 0.95; P ≤ 0.01). Root injury score was correlated positively with field fall growth (r = 0.87) and winter injury scores (r = 0.95; P < 0.01). Large plants (>10‐mm root diameter) had lower cold injury scores than small plants (1‐ to S‐mm root diameter). Correlations between plant size and winter injury were greatest (r > −0.55, P ≤ 0.05) at low freezing temperatures. We propose a laboratory test in which field‐hardened seeding‐year alfalfa entries of a similar size are packed in dry vermiculite, exposed to temperatures of −12 to −16°C for 1 to 2 h, thawed, and scored after 3 wk of regrowth.
Sowing Date and Kernel Weight in Maize
Authors: Cirilo A. G. , Andrade F. H.
Published: July 2010

Sowing date in temperate regions determines the environmental conditions to which the maize (Zea mays L.) crop is exposed during grain filling. The objective of this work was to study the effect of sowing date on individual kernel weight of irrigated, well‐fertilized maize crops. Four experiments were conducted in the field from 1989–1990 to 1993–1994 with a commercial maize hybrid (DK636). The treatments consisted of different sowing dates (from mid‐September to mid‐December). Delays in sowing date reduced individual kernel weight. Late sowings decreased the effective rate of grain filling and shortened the effective duration of grain filling compared with earlier sowings. Plant growth rate during grain filling was slower in later plantings because of low daily incident radiation and radiation use efficiency. There were no differences in the number of endosperm cells formed among sowings; thus, the potential capacity of kernels to accummulate assimilates did not contribute to the low final weight observed in later plantings. The effective rate of grain filling was affected strongly by temperature, increasing about 0.3 mg d−1 per °C. The effective duration of grain filling depended on the availability of assimilates and on the rate of grain filling when sowing was delayed. Reductions in the source of assimilates at later sowing dates caused lower kernel weight at harvest.
Genetic Mapping of Loci underlying Field Resistance to Soybean Sudden Death Syndrome (SDS)
Authors: Hnetkovsky N. , Chang S. J. C. , Doubler T. W. , Gibson P. T. , Lightfott D. A.
Published: July 2010

Sudden death syndrome (SDS) is a fungal disease of soybean [Glycine max (L.) Merr.], caused by Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burk.) Snyd. & Hans., type A (FSA), that reduces crop yields in the USA. Quantitative partial resistance to SDS does exist; therefore, one method of controlling the disease is to select cultivars with genetic resistance. The objective of this study was to use molecular markers to identify and locate alleles of chromosomal segments associated with field resistance to SDS in adapted soybean genotypes. Seventy polymorphic DNA markers were compared with SDS response among 100 F5:9 recombinant inbred lines derived from a cross between SDS‐resistant ‘Forrest’ and SDS‐susceptible ‘Essex’. SDS disease incidence (D1), disease severity (DS), and yield were determined in replicated, FSA‐infested test sites during 4 yr encompassing five locations with recombinant inbred lines from the F5:7 to F5‐11.Two separate chromosomal segments identified by two RAPD markers, OOO5250 and OC0l650, were found to be associated with mean SDS response across five locations as well as within each of the five locations. These two quantitative trait loci (QTL) jointly accounted for 34% of total phenotypic variability in mean D1. OCOl650 was significantly associated with mean DS and yield and was putatively assigned to linkage group N. The beneficial allele was derived from the resistant parent Forrest. OO05250 was not significantly associated with mean DS or yield and was putatively assigned to linkage group C. The beneficial allele was derived from the susceptible parent Essex. Molecular markers can be used to define alleles of chromosomal segments conferring resistance to SDS in several environments and may allow efficient selection of resistant genotypes with good yield potential for FSA‐infested fields.
Rhizoctonia Foliar Blight Reactions and Seed Yields in Soybean
Authors: Harville B. G. , Russin J. S. , Habetz R. J.
Published: July 2010

Rhizoctonia foliar blight (RFB) is caused by the fungus Rhizoctonia solani Kühn anastomosis group 1, intraspecific groups IA and IB. The disease affects more than half of the soybean [Glycine max (L.) Merr.] acreage in Louisiana. Although less‐susceptible cultivars are recommended, reliable estimates of cultivar susceptibility have been difficult to obtain because of several factors, including uneven distribution of RFB in fields, differences in plant developmental stage at time of infection, and the requirement for free moisture in RFD development. The objective of this study was to screen commercial soybean cultivars grown throughout the southern USA, as well as advanced breeding genotypes, for field reaction to RFB in south Louisiana. Ninety‐one soybean genotypes, representing Maturity Groups IV, V, VI, and VII, were evaluated at two locations in 1993 and 1994. Disease ratings were made with a severity scale that included pods as well as foliage. A range of reactions to RFB was observed among cultivars, but most were severely damaged. Significant negative correlations between RFB severity and yield occurred among cultivars in all Maturity Groups. Results identified several cultivars, notably Buckshot 66 and Pioneer variety 9593, with promising levels of resistance.
Inheritance of β‐Glucan Content of Oat Grain
Authors: Holthaus J. F. , Holland J. B. , White P. J. , Frey K. J.
Published: July 2010

β‐Glucan in oat (Avena sativa L.) grain is primarily responsible for the beneficial effect of oat fiber on lowering blood serum cholesterol levels in humans. Plant breeding programs designed to genetically alter the β‐glucan contents of oat germplasm would benefit from information on the inheritance of this trait. Two experiments were conducted to study the inheritance of β‐glucan. Generation means analysis of five populations derived from biparental crosses between high and low β‐glucan lines and cultivars was used to determine the genetic effects controlling β‐glucan content in these populations. Parent‐offspring regression was performed by using β‐glucan data collected from individual plants of 166 oat lines and cultivars and their selfed offspring, allowing estimation of broad‐sense heritability for β‐glucan content in a diverse sample of oat germplasm. Additive gene effects were more important, and dominant gene effects were detected in only two of five biparental populations. No evidence of epistatic gene effects was found. Broad‐sense heritability was estimated as 0.55 on an individual plant basis. This estimate is based on the covariance of inbred parents and their selfed progeny, which involves twice the additive gene action of the reference noninbred population, as well as nonadditive genetic effects. Selection based on replicated progeny families would involve a higher heritability. A positive correlation between grain yield and β‐glucan was observed in the generation means analysis. These results suggest that plant breeders should be successful in altering β‐glucan in oat through direct selection for this genetically variable trait.
Characterization of Stem Canker Resistance in ‘Hutcheson’ Soybean
Authors: Tyler Jeff M.
Published: July 2010

Stem Canker caused by Diaporthe phaseolorum (Cooke & Ellis) Sacc. f. sp. meridionalis Morgan‐Jones (Dpm) can cause significant yield losses in soybean [Glycine max (L.) Merr.] in the southern USA. Some cultivars are known to be resistant to the disease; however, the parental donor, level, and inheritance of stem canker resistance for most of those cultivars is unknown. The objective of this study was to characterize stem canker resistance in ‘Hutcheson’, a widely used parent in breeding programs. To determine the inheritance of resistance and allelic relationships with known genes, Hutcheson was crossed with susceptible genotypes ‘Hartwig’ and J77‐339 and four lines carrying Rdcl, Rdc2, Rdc3, or Rdc4. Crosses were made in the field at Stoneville, MS, in 1993. The parents of Hutcheson and the six F2 populations were toothpick inoculated in the field in 1993 and 1994, respectively. In 1994, Hutcheson and 29 other soybean genotypes were inoculated with four isolates of Dpm and external lesion length was recorded as a measure of level of resistance. Genetic ratios from F2 populations indicate that resistance in Hutcheson is conferred by a single dominant gene that is allelic with Rdc4. ‘York’ was determined to be the parental donor of resistance carried by Hutcheson. Isolates differed in virulence. Hutcheson and several other genotypes were highly resistant to all isolates. Hutcheson should continue to be an excellent source of stem canker resistance.
Light Interception, Reserve Status, and Persistence of Clipped Mott Elephantgrass Swards
Authors: Chaparro C. J. , Sollenberger L. E. , Quesenberry K. H.
Published: July 2010

Defoliation management is an important determinant of persistence of perennial forages. Persistence and related responses of ‘Mott’ elephantgrass (Pennisetum purpureum Schum.) have not been studied under a wide range of defoliation management practices. The objective of this study was to determine the effect of defoliation frequency and stubble height on Mott canopy light interception, rhizome mass and reserve status at season end, tiller number in spring, and persistence. Treatments imposed in 1989 through 1991 included all 16 treatment combinations of four defoliation heights (10‐, 22‐, 34‐, and 46‐cm stubble) and four defoliation frequencies (3, 6, 9, and 12 wk). Treatments were replicated three times in a randomized block design, and the soil was a hyperthermic, uncoated Aquic Quartzipsamment. Data were analyzed by litting multiple regression equations starting with a second order polynomial model. Light interception after harvest ranged from 11 to 60% and was affected only by defoliation height. Light interception increased as defoliation height increased, but at a decreasing rate. Light interception before harvest ranged from 52 to 96% and was lowest for the 3‐wk defoliation frequency, 10‐cm stubble height treatment. In December following 2 yr of defoliation, rhizome total nonstructural carbohydrate concentration (TNC) ranged from 135 to 271 g kg−1 dry matter (DM), rhizome mass ranged from 24 to 733 g DM m−2, rhizome TNC content was from nearly 0 to 197 g TNC m−2, and rhizome N concentration was from 10.9 to 14.2 g kg−1 DM. Plants defoliated every 3 wk at a 10‐cm stubble height had the lowest rhizome mass, TNC concentration and content, and N concentration, while values were greatest for those defoliated every 12 wk at a 46‐cm defoliation height. Number of tillers per plant in May of 1990 and 1991 followed a similar trend. We conclude that Mott elephantgrass is persistent over a relatively wide range of clipping management practices, but close and frequent defoliation results in depletion of reserves and stand decline.
Evaluation of F2 Genotypes of Cotton for Conservation Tillage
Authors: Bauer Philip J. , Green Cynthia C.
Published: July 2010

Reduced plant populations often occur when cotton (Gossypium hirsutum L.) is grown in conservation tillage systems. Our objectives were to determine the potential of exploiting hybrid vigor in F2 cotton to improve stand establishment and yield in conservation tillage systems and to compare the expression of heterosis in this system with that in a conventional tillage system. This field study was conducted in 1991,1992, and 1994 on a Norfolk loamy sand soil (fine‐loamy, silicious, thermic, Typic Kandiudult) near Florence, SC. Five cotton cultivars were crossed in a half‐diallel design to generate 10 F2 generation genotypes. The parent and F2 generations were planted into conservation tillage plots that had desiccated crimson clover (Trifolium incarnatum L.) as a surface mulch and into conventional tillage plots. Cotton stands were similar for both generations in both tillage systems in 1991. At 2 wk after planting in 1992, a tillage × (Parent vs. F2) interaction (P ≤ 0.05) occurred for plant population as stands in conventional tillage were 7.5 and 8.4 plants m−1 for the parent and F2 generations, respectively, while stands in conservation tillage were 4.1 plants m−1 for the parents and 4.2 plants m−1 for the F2 generation. At 2 wk after planting in 1994, stands of the F2 generation were 1.3 plants m−1 greater than the parents averaged over both tillage systems. Yield differences occurred only in 1992, when the F2 generation had greater lint yield than the parents in both tillage systems. The results suggest that growing F2 genotypes may improve cotton stand establishment and yield under certain conditions in conservation tillage systems, but the amount of improvement will be similar to that found in conventional tillage.
Genetic Analysis for Stalk Lodging Resistance in Narrow‐Base Maize Synthetic Population ZPS14
Authors: Djordjevic Jovan S. , Ivanovic Mile R.
Published: July 2010

Stalk lodging resistance and grain yield are the result of interactions of many traits expressed during maize (Zea mays L.) development. Determination of which traits influence stalk lodging resistance and grain yield might improve breeding program efficiency. The main objective of this study was to identify stalk traits that might relate to stalk lodging and grain yield, so that they can be selected as correlated traits for improving both grain yield and stalk quality. For this investigation, S1 progenies were randomly derived from the Yugoslavian maize synthetic population ZPS14. Correlations and path coefficient analysis showed stalk water content had the greatest impact on stalk lodging resistance and grain yield. Genotypic correlations (rg) revealed that stalk water content had a negative and significant influence on both percentage of lodged plants (rg = – 0.46*) and grain yield (rg = – 0.42*). Thus, improvement in grain yield and stalk lodging would be not expected from selection for stalk water content. However, a small number of S1 families with high stalk water content and above average grain yield were identified, suggesting some progress could be made in improving both traits simultaneously if the breeding population was large. A significant genotypic relationship was not found for grain yield and stalk lodging resistance (rg = 0.04). As shown by path analysis, direct effects of stalk lodging on grain yield were small and nonsignificant (P1.2 = 0.003). Breeding for better stalk quality, thus, will not affect future progress of selection for grain yield.
Production and Characterization of Tobacco Addition Lines Carrying Nicotiana debneyi Chromosomes with a Gene for Resistance to Black Root Rot
Authors: Bai Dapeng , Reeleder R. , Brandle J. E.
Published: July 2010

Black root rot, caused by Chalara elegans Nag. Raj and Kendrick (syn: Thielaviopsis basicola [Berk. and Broome] Ferr.), is a common soil‐borne fungal disease in cultivated tobacco (Nicotiana tabacum L., 2n = SSTT=48). Only polygenic partial resistance to this disease is available in the original tobacco genomes; however, Nicotiana debneyi Domin, a tetraploid relative of tobacco (2n = XXYY = 48) has complete resistance to a wide spectrum of black root rot biotypes. A fertile somatic hybrid between N. tabacum ‘Delgold’ and N. debneyi was previously produced and was used to transfer the N. debneyi black root rot resistance into tobacco. Tobacco addition lines carrying the N. debneyi chromosomes with the gene for black root rot resistance were produced after two generations of backcrossing to the recurrent tobacco parent followed by two generations of selfing. Random amplified polymorphic DNA (RAPD) analyses of the disomic (2n = 50) addition lines and 14 monosomic (2n = 49) addition lines derived there from provided strong evidence that the two N. debneyi chromosomes in the 2n = 50 addition lines were identical. However, the tobacco genetic background apparently prevented homologous pairing of these chromosomes or caused their desynapsis. Lagging chromosomes at anaphase I and micronuclei at telophase I were observed. Transmission rates of the N. debneyi chromosomes through the egg and pollen of the addition lines were 8.1 and 10.1%, respectively. The N. debneyi chromosomes in the addition lines occasionally paired with tobacco chromosomes, and therefore, translocation lines with black root rot resistance (2n = 24 II) may be obtained in the self‐pollinated progeny by crossing‐over. Seventeen RAPD markers were found to be associated with the N. debneyi chromosomes in the addition lines and these should be useful in monitoring further transfer of N. debneyi chromosome fragments into the tobacco genomes.
Transfer of Wheat Streak Mosaic Virus Resistance from Agropyron intermedium into Wheat
Authors: Friebe B. , Gill K. S. , Tuleen N. A. , Gill B. S.
Published: July 2010

Wheat streak mosaic is a damaging disease of cultivated bread wheat, Triticum aestivum L. em Thell., in many parts of the world. No wheat cultivar has a high level of resistance to WSMV or its vector, the wheat curl mite, Eriophyes tulipae Keifer. Genes conferring resistance to wheat curl mite colonization have been transferred from Aegilops tauschii Coss., Cmc1, and from Agropyron elongatum (Host) Beauv., Cmc2. A gene conditioning resistance to WSMV, Wsm1, was transferred from Agropyron intermedium (Host) Beauv. into common wheat. To broaden the genetic base of wheat, new sources of WSMV resistance are continuously sought. This study reports a new source of WSMV resistance derived from A. intermedium and its transfer into hexaploid wheat. C‐banding analysis was used to cytogenetically identify the A. intermedium chromosomes and chromosome arms in three WSMV resistant wheat‐A. intermedium derivatives, designated as 6957,6961, and 6962. All lines were identified as disomic chromosome addition lines with an A. intermedium chromosome arm in common. Restriction fragment length polymorphism analysis was used to establish homoeology of the A. intermedium chromosome arm carrying the gene or gene complex conditioning resistance to WSMV. The arm belonged to the long arm of the wheat Group 4 chromosomes, and was designated as 4Ai#3L. The added A. intermedium chromosomes present in Lines 6957 and 6961 probably originated from centricfusion. The WSMV resistance of these lines is different from that conditioned by Wsm1 and may have significance in breeding WSMV resistant wheat cultivars.
Best Linear Unbiased Prediction of Maize Single‐Cross Performance Given Erroneous Inbred Relationships
Authors: Bernardo Rex
Published: July 2010

Best linear unbiased prediction (BLUP) of maize (Zea mays L.) single‐cross performance requires estimates of genetic relationship among parental inbreds. Error in estimates of genetic relationship may result from selection, genetic drift during inbreeding, or incomplete or unknown pedigrees. The objective of this study was to investigate the robustness of BLUP when estimates of genetic relationship among inbreds are erroneous. Grain yield, moisture, stalk lodging, and root lodging data were obtained for 2043 maize single crosses evaluated in the multilocation testing program of Limagrain Genetics, from 1990 to 1994. Three types of errors in inbred relationships were studied: (i) simulated random deviations from the expected contributions of parents to progeny; (ii) unknown parentage for 10% of the inbreds; and (iii) unknown parentage for 25% of the inbreds. Malécot’s coefficients of coancestry (ƒ) were calculated by tabular analysis of the correct and erroneous pedigrees and were subsequently used in BLUP. Average absolute deviations between erroneous ƒ and ƒ calculated from correct pedigrees ranged from near‐zero to ≈ 0.30. But the correlations between predicted and observed single‐cross performance were not affected by the relatively large errors in ƒ. Most of the differences, caused by erroneous ƒ, in the correlations between predicted and observed performance ranged from 0.001 to 0.030 and were too small to have any practical significance. These results indicated that BLUP is robust when inbred relationships are erroneously specified. Estimating ƒ with molecular markers, prior to predicting the single‐cross performance of inbreds with incomplete or unknown pedigrees, seems unnecessary.
Late Season Water Stress in Cotton: II. Leaf Gas Exchange and Assimilation Capacity
Authors: Faver K. L. , Gerik T. J. , Thaxton P. M. , El‐Zik K. M.
Published: July 2010

Water stress reduces net CO2 assimilation (A) and yield of cotton (Gossypium hirsutum L.), but our knowledge of the physiology, of water stress on A and assimilation capacity is incomplete. Experiments were conducted in a rain shelter‐lysimeter facility in 1990 and 1991 to determine if the yields of two short‐season cotton cultivars with common ancestry, TAMCOT HQ95 (HQ95) and G&P74 + (GP74), resulted from intrinsic differences in A and assimilation capacity. Water stress was imposed by withholding 0, 50 or 75, and 100% of the depleted soil water after flowering. Results indicated that both stomatal and nonstomatal factors were important in controlling A. HQ95 bad higher A and g than GP74 over leaf water potentials (ΨL) ranging from − 1.0 to − 3.2 MPa. Nonstomatal limitations to A were more important than stomatal factors when ΨL was > − 1.5 MPa. Stomatal factors limited A when ΨL was < − 1.5 MPa for both cultivars. The initial slope (Si) and the maximum A at high ci (Amax)declined with increasing water stress for both cultivars. The Si was greater for HQ95 than GP74 over the range in ΨL and suggest that HQ95 had higher ribulose‐l,5‐bisphosphate carboxylase‐oxygenase activity than GP74. Increasing water stress reduced Amax equally in both cultivars. This suggests that electron transport processes for ribulose‐l,5‐bisphosphate regeneration of the cultivars did not differ. Therefore, stomatal and nonstomatal CO2 assimilation processes are important in limiting A of water stressed cotton. Intrinsic differences in these processes enable some cotton cultivars to better tolerate water stress.
Processes Contributing to N2‐Fixation Intensitivity to Drought in the Soybean Cultivar Jackson
Authors: Serraj Rachid , Sinclair Thomas R.
Published: July 2010

Previous research has shown that N2 fixation in soybean [Glycine max (L.) Merr.] is sensitive to drought and begins to decrease at relatively high soil water contents. The fact that N2 fixation rates decrease with soil water deficits in advance of other physiological processes causes an important constraint on soybean performance. Recent evidence, however, indicates possible genetic variation within soybean for this trait. The cultivar Jackson reportedly has N2 fixation activity that was relatively drought insensitive. The objective of this research was to investigate the physiological basis of this unique response in Jackson in comparison with the drought‐sensitive cultivar Biloxi. Experiments were carried out with plants grown in pots in a greenhouse and exposed to drought by soil dehydration. The drought tolerance of N2 fixation in Jackson was confirmed, as well as in one of its parents, ‘Volstate’. Interestingly, Jackson as either the rootstock or scion in grafting studies conferred drought tolerance. Enriching the atmosphere with oxygen around the nodules resulted in a complete recovery of nodule activity in moderately drought‐stressed plants and in partial recovery as the stress severity increased. Elevated oxygen also induced a substantial stimulation of acetylene‐reduction rates in Jackson well‐watered plants. Finally, Jackson was found to have lower levels of ureides in petioles in well‐watered plants than in a sensitive cultivar, and the accumulation of ureides under drought was much less in Jackson. These results demonstrated that N metabolism, physiology, and genetic background are important in accounting for unique behavior of N2 fixation in Jackson under water‐deficit conditions.
Chloroplast DNA and Nuclear DNA Content Variations among Cultivars of Switchgrass, Panicum virgatum L
Authors: Hultquist Sherry J. , Vogel K. P. , Lee D. J. , Arumuganathan K. , Kaeppler S.
Published: July 2010

Switchgrass, Panicum virgatum L., is a native, cross‐pollinated, morphologically diverse species with an array of ploidy levels and ecotypes. Switchgrass is found throughout most of the USA and Canada, primarily east of the Rocky Mountains and south of Hudson Bay. The objective of this research was to determine if chloroplast DNA (cpDNA) restriction fragment length polymorphisms (RFLPs) occur among switchgrass cultivars and experimental strains that differ in ploidy level or ecotype classification. Eighteen switchgrass cultivars or experimental strains representative of reported ecotypes, ploidy levels, and the geographical range of switchgrass were surveyed for cpDNA polymorphisms by means of four restriction endonucleases and 20 sorghum cpDNA probes. One polymorphism was detected which was associated with the lowland‐upland ecotype classification. The lowland cultivars contained a restriction site change that was not present in the upland cultivars. The two cytotypes discovered have been designated as the U (upland) or L (lowland) cytotype. The lowland cultivars had 3 pg DNA/nuclei as measured by flow cytometry while the upland types had either 3 or 6 pg DNA/nuclei. There were no cpDNA polymorphisms among the upland cultivars regardless of ploidy level as measured by DNA content. These results demonstrate that cpDNA differs among switchgrasses and that this variation is associated with ecotype variation but not with nuclear DNA content.
Genetic Control of High Oleic Acid Content in the Seed Oil of Two Soybean Mutants
Authors: Rahman Shaikh M. , Takagi Yutaka , Kinoshita Takehito
Published: July 2010

Soybean [Glycine max (L.) Merr.] oil with high content of oleic acid (>300 g kg−1) is less susceptible to oxidative changes during refining, storage, and frying. Two mutants (M23 and M11) were developed that had high content of oleic acid in the seed oil compared with the original cultivar (Bay). The objective of this study was to compare the genetic control of oleic acid content in these mutants. Reciprocal crosses were made between each mutant and Bay and between the two mutants. There were no maternal and cytoplasmic effects for oleic acid content in any of these crosses. The analysis of fatty acid composition of the parents, F1, and F2 seeds from the cross between M23 and Bay and between M11 and Bay indicated that oleic acid content was controlled by a single gene. The cross between M23 and M11 indicated that each mutant had a different allele at the same locus for the oleic acid content. The Ol allele for low oleic acid content in Bay was partially dominant to the allele ol for high oleic acid content in M23 but completely dominant to the allele ola for high oleic acid content in M11. The allele ola in M11 was completely dominant to the ol allele in the M23. There was a complete inverse relationship between oleic and linoleic acid contents in both mutants. It indicated that the mutant alleles ol and ola may also control the linoleic acid content by blocking the synthesis of this acid at the step of oleic acid desaturation.
The Inheritance of a Branching Type in Soybean
Authors: Nelson Randall
Published: July 2010

Many environmental factors including plant spacing, photoperiod, and plant nutrition can affect the number and distribution of branches on soybean [Glycine max (L.) Merr.] plants. Differences in branching have been noted among soybean lines, but because of the strong environmental influences on branching very little is known of the genetic control of this trait. The lack of information about the genetic control of branching in soybean limits the modifications that can be made in soybean plant architecture. Experimental lines developed from the cross of PI 391.583 (Jilin No. 10) by PI 189.916 were found to have very different branching patterns. The low‐branching type had fewer branches and the branches were restricted to the lower portion of the main stem. The high‐branching type had more branches and many branches originated at the upper nodes giving the plant a bushy appearance. Crosses were made among four lines of similar and different branching types in order to study inheritance. When similar branching types were crossed no segregation for branching type was observed among progeny. Crosses between high and low branching types produced progeny that segregated in a 9:7 ratio. It was necessary to observe the F2:3 families in order to accurately determine the genotype of the F2 plants. These data indicate that two dominant alleles at independent loci were necessary to produce the high branching phenotype. The gene symbols Br1 and Br2 are proposed for these loci.
Genetic and Allelism Analyses of Hypernodulation Soybean Mutants from Two Genetic Backgrounds
Authors: Vuong T. D. , Nickell C. D. , Harper J. E.
Published: July 2010

Several chemically mutagenized lines of soybean [Glycine max (L.) Merr.] have shown enhanced nodulation and partial tolerance to high NO−3 levels. Previous genetic analyses of hypernodulating or supernodulating soybean mutants indicated that they were genetically controlled by recessive monogenes following simple Mendelian principles. In the present study, we determined the genetic control of hypernodulating mutants selected from two soybean cultivars, Williams and Enrei, and analyzed the allelism of mutant genes controlling the hypernodulating phenotypes. Reciprocal crosses between four hypernodulating mutants (NOD1‐3, NOD2‐4, NOD4, and En6500) and two normally nodulated cultivars (Williams 82 and Harosoy 63) were made. The patterns of nodulation in F1s, F2s, and F2:3 progeny were visually evaluated at 14 d after planting in the greenhouse. Chi squares for each progeny and homogeneity tests for each cross were calculated. The results indicated that hypernodulation in the mutants studied was conditioned by single recessive genes. Three mutants (NOD1‐3, NOD4, and En6500) were controlled by a single recessive allele rj7, although they were isolated from distinctly different genetic materials. The allelism study indicated that another non‐allelic mutant gene was identified which was responsible for hypernodulation in mutant NOD2‐4. This new gene has been tentatively designated rj8. With respect to genetic interaction between the two mutant genes identified, the segregation ratio in the F2 did not fit a classical pattern and therefore we speculated that these two genes interact to modify expression in an unknown fashion. Hence, additional genetic analysis is needed to clarify the genetic interaction between rj7 and the proposed rj8 gene.
Soybean Response to Nodulation by Wild‐Type and an Isogenic Bradyrhizobium elkanii Mutant Lacking Rhizobitoxine Production
Authors: Xiong K. , Fuhrmann J. J.
Published: July 2010

Soybean [Glycine max (L.) Merr.] cultivars differ in their susceptibility to rhizobitoxine‐producing (RT+) bradyrhizobia, but the physiological basis for this variation is uncertain. We conducted greenhouse experiments to determine the response of six cultivars, that differ in their RT susceptibilities, to nodulation by four strains of Bradyrhizobium: USDA 61 and 94 (RT+ wild‐type B. elkanii strains), USDA 110 (RT wild‐type B. japonicum strain), and RX 18E (a Tn5‐induced mutant of USDA 61 lacking RT production in planta). At 45 d after planting, plants were rated for RT symptoms and analyzed for shoot N contents and shoot, root, and nodule biomass and RT concentrations. Foliar chlorosis was generally better correlated with shoot RT concentrations than with nodular concentrations. Strain USDA 94 generally produced more RT in planta than did USDA 61. When nodulated by USDA 61, cultivars rated as RT‐resistant often had lower nodular RT concentrations than did RT‐susceptible plants. Relative to RX 18E, nodulation by USDA 61 significantly reduced plant shoot weight for the RT‐sensitive cultivar Hutcheson and tended to reduce shoot weight for all remaining cultivars except the highly resistant SS FFR 565; decreased shoot N content by 50.5 and 17.4% in cultivar Hutcheson and Williams, respectively; and had no significant effect on nodule number and nodule weight. These results indicate that mechanisms of RT resistance may differ among the cultivar‐strain combinations examined and involve differences in RT production, RT export from the nodules, and RT detoxification during and following transport to the shoot.
Mobility and Persistence of Pesticides Applied to a USGA Green. III: Organophosphate Recovery in Clippings, Thatch, Soil, and Percolate
Authors: Cisar J. L. , Snyder G. H.
Published: July 2010

The general public is concerned about potential environmental in pacts of agrochemicals applied to turfgrass. It is especially important that certain industry standard turfgrass systems, such as USGA greens, be evaluated for potential environmental impact. The objective of this study was to assess the mobility and persistence of chlorpyrifos (O,O‐diethyl‐O‐3,5,6‐trichloro‐2‐pyridylphosphorothioate),isazophos [O‐[5‐chloro‐1‐(methylethyl)‐lH‐l,2,4‐triazol‐3yl] O,O‐diethyl phosphorothioate], isofenphos [1‐methylethyl 2‐[[ethoxy(1‐methylethyl) amino] phosphinothioyl]oxy] benzoate], and ethoprop (O‐ethyl S,S‐dipropylphosphorodithioate) applied to a USGA cv. Tifdwarf bermudagrass (Cynodon dactylon × C. transvaalensis Burtt‐Davy) green. The quantity of each organophosphate (OP) pesticide in turf clippings, thatch, soil, and percolate was determined over two application cycles, with the exception of ethoprop which was applied once. Pesticide recovery in clippings after a single application of fenamiphos (ethyl 3‐methyl‐4(methylthio)phenyl (1‐methylethyl)phosphoramidate) and fonofos (O‐ethyl‐S‐phenyl ethylphosphonodithioate) was determined, in addition to the above mentioned OP pesticides. For liquid formulations, less than 1% of the OP pesticides applied were found in clippings. However, nearly 8% of chlorpyrifos and 1.2% of fonofos was removed in clippings after a granular application. Total average pesticide removed in clippings after granular applications of ethoprop, chlorpyrifos, fenamiphos, and fonofos were 9.9, 9.2, 5.1, and 4.3 mg m−2, respectively, while the largest amount from a liquid application of pesticide removed in clippings was 2.0 mg m−2 of isofenphos. Less than 0.1% of the OP pesticides applied to the USGA green were recovered in percolate water, regardless of substantial variations in rainfall and total percolation. Most of the applied OP pesticides appeared to be retained in the thatch layer, where presumably they were microbially degraded over time.
Near‐Isogenic Analysis of Uniculm and Conventional‐Tiilering Barley Lines
Authors: Dofing S. M.
Published: July 2010

The uniculm phenotype has been proposed as a component of a small grain ideotype that maximizes crop productivity. Additionally, uniculm plants do not produce late‐developing tillers that delay harvest and reduce grain quality in short‐season or northern areas of production. No comprehensive studies that assessed the uniculm phenotype in barley (Hordeum vulgare L.) using near‐isogenic lines were found in the literature. This study was conducted to compare the performance of uniculm and conventional‐tillering near‐isogenic barley lines that differed by the presence of the uc2 (uniculm) gene. Two pairs of nearqsogenic lines were evaluated at seeding rates of 50, 140, 230, and 320 kernels m−2 and row spacings of 15 and 30 cm, for 3 yr at Palmer, AK. Uniculm lines matured an average of 6 d earlier than conventional‐tillering lines. However, maximum grain yield of uniculm lines was only 52% of that of conventional‐tillering lines. At all seeding rates, spikes per square meter and kernels per spike of uniculm lines were lower than conventional‐tillering lines, but kernel weight was higher. The lower grain yield of uniculm lines was due primarily to reduced kernels per spike at high seeding rates. Selection for grain yield or kernels per spike at high seeding rates should be investigated as a possible means of increasing grain yield of uniculm lines.
Comparison of Two Phenology Models for Predicting Flowering and Maturity Date of Soybean
Authors: Piper Ernest L. , Boote Kenneth J. , Jones James W. , Grimm Sadi S.
Published: July 2010

Unbiased prediction of plant growth stages is essential for accurate simulation of stage‐specific responses to environmental factors. The phenology model in SOYGRO V5.42 was compared with the phenology model in CROPGRO V3.0 for prediction of flowering and maturity date. Data came from 17 sources in North America and covered a wide range of maturity groups. An additional large‐scale data set from the U.S. Soybean Uniform Tests was used to evaluate predictions of maturity date. Parameters of the phenology models were estimated with an optimization procedure in which the downhill simplex method determined the direction of the search. While the optimization procedure was valuable to estimate the parameters, additional criteria were required to obtain realistic values. Based on the root mean square error (RMSE) criterion between predicted and observed dates, SOYGRO and CROPGRO predicted flowering equally well. Development rate after flowering was underpredicted by SOYGRO in cool environments so that in some years, maturity was predicted very late. CROPGRO has a separate temperature function after beginning seedfill, which decreased the RMSE for prediction of maturity date compared with SOYGRO, especially for early maturity cultivars. Allowing the critical short day length to increase after flowering date in the CROPGRO model consistently decreased the RMSE for prediction of beginning seedfill and maturity. CROPGRO was superior to SOYGRO for prediction of maturity date.
Plant Recovery of Selfs and Interspecific Hybrids of Arachis by In Vitro Culture of Peg Tips
Authors: Feng Q. , Stalker H. Thomas , Pattee Harold E.
Published: July 2010

Embryo abortion is a barrier to interspecific hybridization between cultivated and wild species of Arachis L., and in vitro culture of embryos prior to abortion is potentially useful for overcoming this problem. In Arachis, the peg tips encase the embryos as they move from above to below ground. The objectives of this research were to enhance the in vitro techniques to rescue selfed embryos of Arachis species and to apply this technique to obtain hybrid plants. Arachis hypogaea L. and four diploid wild species—A. glandulifera Stalker, A. duranensis Krapov. and W.C. Gregory, A. batizocoi Krapov. and W.C. Gregory, and A. valida Krapov. and W.C. Gregory—which have different degrees of compatibility with A. hypogaea were used. Ten‐day‐old peg tips were cultured on the combined MS and B5 media with 1‐naphthaleneacetic acid (NAA), gibherellic acid (GA3), and and 6‐benzylaminopurine (BAP) for 90 d. In vitro‐developed ovules, embryos, or seeds were subcultured to regenerate plants. The results indicated that A. hypogaea had higher frequencies of pod and seed production than the wild species. Arachis glandulifera produced more pods and seeds than the other three wild species, and no significant difference in pod and seed production was found among A. duranensis, A. valida, and A. batizocoi. Selfed plants were recovered from all live species. In vitro development of hybrid embryos to the cotyledonary stage was observed in all eight interspecific crosses among A. hypogaea and the four Arachis dipioids. Mature hybrid plants were recovered from seven of eight combinations. This is in contrast to plants recovered from five of eight hybrid combinations (including reciprocals) when pods were left on the plant. Arachis glandulifera × A. hypogaea hybrids which previously had been attempted, but not obtained, were recovered through peg tip culture followed by somatic embryogenesis. This study demonstrated that Arachis hybrid proembryos can be rescued through peg tip culture.