bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Progress From 50 Years of Smooth Bromegrass Breeding
Authors: Casler M. D. , Vogel K. P. , Balasko J. A. , Berdahl J. D. , Miller D. A. , Hansen J. L. , Fritz J. O.
Published: July 2010

Since its introduction from Eurasia, smooth bromegrass (Bromus inermis Leyss.) has become an important cool‐season forage grass in North America. The objective of this study was to document breeding progress in smooth bromegrass between 1942 and 1995 in North America. Thirty cultivars or experimental populations were tested at up to seven sites in the eastern and central USA, with a range of soil types and climates. There have been small genetic changes in forage yield, brown leafspot resistance [caused by Pyrenophora bromi (Died) Drechs.], in vitro dry matter digestibility (IVDMD), and neutral detergent fiber (NDF) concentration. Brown leafspot resistance increased gradually, averaging 0.21 units decade−1. Mean forage yield did not change for cultivars developed after 1942, but was 0.54 Mg ha−1 (7.2%) higher for the post‐1942 group than in ‘Lincoln’, a direct representative of smooth bromegrass introduced into North America. Selection for increased IVDMD led to an average increase in IVDMD of 9 g kg−1 (1.4%), an increase in forage yield of 0.33 Mg ha−1 (5.0%), and a decrease in NDF of −8 g kg−1 (−1.2%) in the post‐1942 group. The slow rate of progress for smooth bromegrass forage yield is due to its complex polyploid inheritance, emphasis on traits other than forage yield, and relatively little concentrated attention from public and private breeders.
Early‐Season Plant Nitrate Test for Leaf Yield and Nitrate Concentration of Air‐Cured Burley Tobacco
Authors: MacKown Charles T. , Crafts‐Brandner S. J. , Sutton Tommy G.
Published: July 2010

Profitable yield and satisfactory leaf quality of burley tobacco (Nicotiana tabacum L.) require proper management of N fertilizer. The level of tissue NO−3 in tobacco may be a suitable diagnostic test of crop N sufficiency that could be used for N management decisions. This study determined the suitability of early‐season tissue NO−3 as a predictor of air‐cured leaf yield and NO−3 concentration. Burley tobacco was grown in 1991 and 1992 on a well‐drained Maury silt loam (fine, mixed, mesic, Typic Paleudalf) and a moderately well‐drained Captina silt loam (fine, silty, siliceous, mesic Typic Fragiudult) broadcast fertilized just before transplanting with 0 to 392 kg N ha−1 Tissue NO−3 levels of plants sampled from 3 to 5 wk after transplanting and air‐cured leaf yields increased with increasing amounts of fertilizer N. Responses differed depending on location and year. When the results were expressed as the percentage of the maximum within year and location, the relationship of leaf yield to early‐season NO−3 was described by a single linear equation (y = 51.0 + 0.448x; r2 = 0.808, P ≤ 0.001). However, to use this equation, it would be necessary to include in each tobacco field evaluated a strip of fertilizer N producing near maximum yield. The NO−3 concentration of burley tobacco between 3 and 5 wk after transplanting was suitable for predicting the NO−3 concentration of air‐cured leaf lamina from the top, middle, and bottom stalk positions, and appeared to be insensitive to year and location effects. Use of plant NO−3 concentration, as an early‐season diagnostic test to predict N sufficiency and NO−3 concentration of cured leaf lamina, appeared to offer promise for better N management of burley tobacco. Such a test during the interval between 3 and 5 wk after transplanting fits well into the normal cultivation practices. However, further research would be needed to calibrate the amount of additional N required to correct N deficits by banding N.
Winter Annual Legumes for Use as Cover Crops in Row Crops in Northern Regions: II. Frost Resistance Study
Authors: Brandsæter Lars Olav , Smeby Thomas , Tronsmo Anne Marte , Netland Jan
Published: July 2010

Several benefits, e.g., weed suppression, are achieved by including a cover crop in a cropping system. A requirement for developing cover crop systems in northern regions is to find species and cultivars which are adapted for the local climate. The basic objective of this study was to investigate the effects of freezing temperatures on subclover (Trifolium subterraneum L.) cultivars; however, because field experiments recently carried out in Norway have shown that subclover only has potential for winter survival near the southern coast, other winter annual legumes were also tested. To make an adequate freezing‐test program reflecting field conditions, a factorial experiment including cultivars, age of subclover plants, and daylength treaments was carried out. The study showed that frost resistance of subclover was increased by short‐day treatments both before and through the hardening periods. The effect of short‐day treatments was more pronounced for the early flowering cultivar Geraldton than for the later flowering cultivar Mount Barker. The freezing program developed for subclover may also be suitable for other winter annual legumes. The results of a winter annual legume experiment showed that hairy vetch (Vicia villosa Roth.) cultivars, especially cv. Hungvillosa, exhibited the best frost resistance, followed by yellow sweetclover [Melilotus officinalis (L.) Pall.], crimson clover (Trifolium incarnatum L.), black medic (Medicago lupulina L.), white clover (Trifolium repens L.), subclover, barrel medic (Medicago trunculata Gaertn.), and snail medic [Medicago scuttelata (L.) Mill.], which exhibited the poorest frost resistance. In terms of relative biomass, the hairy vetch cultivars Welta and Hungvillosa were significantly different at −9°C. In general, hairy vetch exhibited the best frost resistance in this study.
Xenia Effects in Maize with Normal Endosperm
Authors: Bulant C. , Gallais A. , Matthys‐Rochon E. , Prioul J.L.
Published: July 2010

Xenia can be defined as the effect of the pollen genes on the development of the fruit or the seeds. In maize (Zea mays L) with normal endosperm, the relative advantage in weight of cross‐fertilized to self‐fertilized kernels can reach 13% when inbred lines are used as females. To improve our understanding of the physiological bases of such a phenomenon in this species, we studied the accumulation of carbohydrate and the activities of starch‐synthesizing enzymes during the grain filling period in kernels from self and cross fertilization on independent ears from the same female inbred line. With one inbred line as female, selfed and crossed to an unrelated male, kernel growth was studied at 14, 21, 28, 39, and 74 d after pollination (DAP). The cross‐fertilization effect on kernel dry weight was maximum at 14 DAP and then decreased about 10%. Male effects on enzyme activities and carbohydrate content were studied at 14 and 28 DAP in a 3‐by‐3 diallel from inbred lines. At 14 DAP, the advantage of cross‐fertilization on average was 28.8% for starch content, 24.8% for ADP‐glucose‐pyrophosphorylase (EC 2.7.7.27) activity, and 24.1% for neutral invertase (EC 3.2.1.26) activity. The advantage depended on the cross for sucrose content, acid invertase activity, and sucrose synthase (EC 2.4.1.13) activity. At 28 DAP, cross‐fertilization advantage was not significant for enzyme activities or carbohydrate content but was still significant for kernel dry weight (+7.8%). At both stages, there was no correspondence between male and female effects, when both were significant. The data tend to show that differences in male effects for enzyme activities are expressed early after fertilization but are insufficient to explain male effects at the level of kernel weight.
Spectral Irradiance Available for Turfgrass Growth in Sun and Shade
Authors: Bell G. E. , Danneberger T. K. , McMahon M. J.
Published: July 2010

The spectral quality of solar radiance affects plant growth and development. The purpose of this study was to assess the spectral quality of deciduous shade, coniferous shade, building shade, and full sun in a natural environment common to turfgrass growth throughout a day and throughout a growing season. A spectroradiometer was used to acquire solar spectra in these four environments. Acquisitions were made on an hourly basis from 0730 to 1930 h, biweekly, from vernal equinox to autumnal equinox at The Ohio Turfgrass Foundation Research and Educational Center and from 10 April to 1 July 1997 at The Ohio State University campus. Data were tested for variation in spectral quality between morning hours and afternoon hours in full sun and among full sun and deciduous, coniferous, and building shade. Results indicated that changes in spectral quality occurred between morning and afternoon periods in full sun, but total (red + blue) photosynthetically active irradiance was not affected. Measurements indicated that a deciduous tree and a conifer tree filtered significantly more high activity (red + blue) quanta than a building. Blue irradiance relative to total irradiance increased and red irradiance decreased with increasing shade density. Significant differences were detected between full sun, tree shade, and building shade for blue photoreceptor potential (blue photon flux/far‐red photon flux) and phytochrome potential (red photon flux/far‐red photon flux). Results indicated that relationships among blue, red, and far‐red irradiance that influence many plant responses were affected by both shade source and shade density.
Root Physiological Characteristics Associated with Drought Resistance in Tall Fescue Cultivars
Authors: Huang Bingru , Gao Hongwen
Published: July 2010

Knowledge of root traits associated with drought tolerance is important for further understanding drought tolerance mechanisms of the whole plant. The experiment was designed to investigate effects of drought stress on root physiological activities of six cultivars (Kentucky‐31, Falcon II, Houndog V, Phoenix, Rebel Jr., and Bonsai) of tall fescue (Festuca arundinaceaSchreb.) varying in drought resistance. Grasses were grown in well‐watered or drying (nonirrigated) soil for 35 d in a greenhouse. Drying reduced root length and dry mass in the 0‐ to 20‐cm layer for all six cultivars. Root length and dry mass in the 40‐ to 60‐cm layer was enhanced for Houndog V, Falcon II, and Kentucky‐31; was not affected for Phoenix and Bonsai; and was reduced for Rebel Jr. by soil drying. Water uptake rates for Falcon II and Kentucky‐31 decreased with soil drying in the 0‐ to 20‐cm layer but increased in the 40‐ to 60‐cm layer. Soil drying limited water uptake by Rebel Jr. in both layers. Drought stress increased root mortality in the 0‐ to 20‐, 20‐ to 40‐, and 40‐ to 60‐cm layers, but the increase was most dramatic in the surface soil layer. The increase in root mortality in each soil layer was most severe for Rebel Jr. and least severe for Kentucky‐31. Root death of tall fescue cultivars during drought was positively correlated with root desiccation, as evidenced by severe leakage of organic solutes from roots in drying soil. Carbohydrate supply to roots was not a contributor to root death during drought stress. This was supported by the increased or unaffected total nonstructural carbohydrates in both shoots and roots, and the increased C allocation to roots under soil drying conditions.
Manipulation of the 1RS.1BL Translocation in Wheat by Induced Homoeologous Recombination
Authors: Lukaszewski Adam J.
Published: July 2010

Centric translocations of the short arm of rye (Secale cereale L.) chromosome 1R are useful in wheat (Triticum aestivum L.) breeding because they confer resistance to several pests and diseases and improve yield. Their major disadvantage is in reduced bread making quality. To remedy this defect, rye chromosome arm 1RS in translocations 1RS.1BL and 1RS.1DL was induced by the ph1b mutation to recombine with the short arms of wheat group‐1 chromosomes. Among 20 234 progeny screened, 139 primary recombinant chromosomes were recovered including 103 with 1BS, 22 with 1AS and 14 with 1DS. The Gli‐1/Glu‐3 loci of wheat were non‐homoeoallelic to the Sec‐1 locus of rye and were separated by about a 13‐cM‐long segment, which on the rye chromosome contained disease resistance loci Pm8, Lr26, Sr31, and Yr9 Pairs of primary recombinants 1RS‐1BS with breakpoints flanking the storage protein loci were intercrossed and two types of secondary recombinant chromosomes 1RS were produced: a group of over 30 chromosomes where the Sec‐1 locus was replaced by segments of 1BS of various lengths, and two chromosomes where 1.4‐ and 3.2‐cM segments of 1BS introduced the Gli‐1/Glu‐3 loci. Selected chromosomes from each class were allowed to recombine within the shared segments of 1RS separating the intercalary wheat segments and two tertiary recombinant chromosomes were recovered. Cytologically, these chromosomes appear as normal 1RS arms but each has two intercalary segments of 1BS: one introducing the Gli‐1/Glu‐3 loci and the second one removing the Sec‐1 locus. Because the protein composition of the resulting translocation lines is identical to that of normal wheat, it is believed that these manipulations could eliminate the quality defect associated with the 1RS.1BL translocation.
A hand‐held porometer for rapid assessment of leaf conductance in wheat
Authors: Rebetzke G. J. , Read J. J. , Barbour M. M. , Condon A. G. , Rawson H. M.
Published: July 2010

Grain yield in bread wheat (Triticum aestivum L.) has been associated with variation in leaf stomatal conductance. However, breeding programs have been reluctant to exploit this relationship because the equipment required is either too costly or too slow for assessing large breeding populations. This study compared a new hand‐held viscous‐flow porometer against a steady‐state diffusion porometer for leaf conductance measured on progeny derived from widely varying conductance wheats, ‘Quarrion’ and ‘Genaro 81’. Leaf conductance values from the two instruments were related linearly, and significant phenotypic and genotypic correlations were obtained across sampling days, suggesting the new porometer is a robust predictor of leaf diffusive conductance. The enhanced speed of the new viscous‐flow porometer in evaluating variation for leaf conductance should enable wheat breeders to screen large breeding populations for leaf conductance more efficiently.
Selection Response in Subdivided Target Regions
Authors: Atlin G. N. , Baker R. J. , McRae K. B. , Lu X.
Published: July 2010

In a small target region, it may be possible to exploit local adaptation to increase gains from selection. However, in a large region more extensive testing is usually possible, resulting in more precise estimation of genotype means. A correlated response model was adapted to determine if division of a large target region is likely to increase gains. Genotypic value in a large region and constituent subregions are considered correlated traits. Correlated response in a subregion to indirect selection across the undivided region, relative to direct response to selection within the subregion, is expressed as a function of heritability in the undivided region (H) and in the subregion (Hi ), and of the genotypic correlation between region and subregion means (rG′). rG′ depends on the magnitude of the genotype × subregion interaction (σ2GS) relative to the genotypic variance (σ2G). σ2GS is the portion of the genotype × location interaction (σ2GL) caused by local adaptation, rather than by random site‐to‐site variability in genotype means. Subdivision can increase heritability through the addition of σ2GS to the numerator of Hi, but this may be offset by reduced replication across locations within the subregion. Modeling using variance estimates from several cereal programs indicated that, unless σ2GL is large relative to σ2G and at least 30% of σ2GL is due to σ2GS, subdivision is unlikely to increase response. These results help explain the success of breeding programs that test broadly.
A Model for Marker‐Based Selection in Gene Introgression Breeding Programs
Authors: Reyes‐Valdés M. Humberto
Published: July 2010

Marker‐based breeding can be useful to expedite introgression of specific genetic material from a donor parent into the background of an elite variety, through backcrossing. A model is proposed to predict the probability of donor parent genetic material being present in specific regions of the genome, and its proportion at the chromosome‐specific or whole genome levels, as a result of marker‐based introgression. Furthermore, formulas are provided to calculate the variance of the predicted values. Two kinds of markers are considered: donor parent specific and recurrent parent specific. The first type serves to introgress the desired fraction of donor genome, and the second one to recover the recurrent parent background genome. In all cases, the probabilities and genomic proportions are calculated on a genetic map basis. This model permits any localization of markers through the genome, but requires knowledge of their map positions and the map lengths of the chromosomes. It is robust to mapping functions, and admits any one based on the assumption of coincidence being equal to the kth power of twice the recombination fraction. Two widely used mapping functions gave fairly different predictions of global chromosome introgression. Monte Carlo simulations for several circumstances allowed the testing of the model, and no significant statistical deviations from the theoretical predictions were found. The results indicate that the formulas presented herein can be useful for planning and prediction in a backcross breeding program.
Association of Puroindoline Sequence Type and Grain Hardness in Hard Red Spring Wheat
Authors: Giroux Michael J. , Talbert Luther , Habernicht Debrah K. , Lanning Susan , Hemphill Amber , Martin John M.
Published: July 2010

Wheat (Triticum aestivum L.) endosperm texture is a primary determinant of milling and end‐product quality. Friabilin, a marker protein for grain hardness, is composed of two proteins, puroindoline a and b (pinA and pinB, respectively). Hard‐textured wheats have variant alleles consisting of a glycine‐to‐serine change in pinB (pinB‐D1b) or the complete absence of pinA (pinA‐D1b). Our objectives were to examine the influence of pinA and pinB alterations on grain hardness from populations among elite hard red spring wheat cultivars differing in puroindoline alteration, and to measure associations of grain hardness with kernel weight and grain protein concentration. Fifty F3:6 progenies from three pinA‐D1b × pinB‐D1b, one pinB‐D1b × pinB‐D1b, and one pinA‐D1b × pinA‐D1b type crosses were evaluated with their parents in two field experiments. Lines classified as pinA‐D1b were significantly harder than lines classified as pinB‐D1b when averaged across the three segregating populations. This difference was significant (P < 0.05) in one of the three populations. Significant genetic variation existed for grain hardness, protein concentration, and kernel weight within puroindoline classes and among lines from crosses not segregating for pinA‐D1b vs. pinB‐D1b Significant positive correlations were observed in all five populations for grain hardness and protein concentration (). Our results indicate that most of the genetic variation in grain hardness among the populations studied was due to factors other than pinA and pinB, as the pinA‐D1b vs. pinB‐D1b difference explained <12% of the variation in grain hardness in these hard wheat populations.
A Uniform, Objective, and Adaptive System for Expressing Rice Development
Authors: Counce Paul A. , Keisling Terry C. , Mitchell Andrew J.
Published: July 2010

The large area of rice (Oryza sativa L.) production worldwide is critical to the well being of large numbers of the world's people. Yet for rice, the most important single plant species for human nutrition, there is not a widely used growth staging system. Despite good points of the published rice growth staging systems, none has been used widely for describing rice growth and development. Consequently, an objective growth staging system with enumeration adapted to cumulative leaf number (CLN) would improve communication among scientists, farmers, and educators. We propose a rice developmental staging system divided into three main phases of development: seedling, vegetative, and reproductive. Seedling development consists of four growth stages: unimbibed seed (S0), radicle and coleoptile emergence from the seed (S1, S2), and prophyll emergence from the coleoptile (S3). Vegetative development consists of stages V1, V2 … VN; N being equal to the final number of leaves with collars on the main stem. Reproductive development consists of 10 growth stages based on discrete morphological criteria: panicle initiation (R0), panicle differentiation (R1), flag leaf collar formation (R2), panicle exertion (R3), anthesis (R4), grain length and width expansion (R5), grain depth expansion (R6), grain dry down (R7), single grain maturity (R8), and complete panicle maturity (R9). Assigning rice growth stages based on discrete morphological criteria will result in unambiguous growth‐stage determination. For example, using this system, two people staging the same plant will arrive at the same growth stage. This is because the system exploits the presence or absence of distinct morphological criteria in a symbolic logic dichotomous framework that only permits yes or no answers.
Heat Stress Injury in Relation to Membrane Lipid Peroxidation in Creeping Bentgrass
Authors: Liu Xiaozhong , Huang Bingru
Published: July 2010

Understanding physiological and biochemical factors involved in heat‐stress injury would help improve heat tolerance of cool‐season grasses. The objective of this study was to investigate lipid peroxidation of cell membranes in relation to heat‐stress tolerance in creeping bentgrass (Agrostis palustris Huds.). Two creeping bentgrass cultivars differing in heat tolerance, L‐93 (heat tolerant) and Penncross (heat sensitive) were grown under two temperature regimes: 22/16°C (day/night) and 35/25°C for 56 d in growth chambers. Photochemical efficiency (Fv/Fm) and chlorophyll content of leaves; and electrolyte leakage (EL); content of the lipid peroxidation product, malondialdehyde (MDA); and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in leaves and roots were determined biweekly during heat stress. Leaf Fv/Fm ratio and chlorophyll content decreased, whereas EL and MDA contents of both leaves and roots increased under heat stress in both cultivars, but to a greater extent in Penncross. The activities of SOD and CAT decreased, whereas POD activity increased in both leaves and roots, which occurred to a greater extent for Penncross. The increases in MDA content and POD activity under heat stress were greater for leaves than for roots in both cultivars. These results suggest that decreased activities of antioxidant enzymes could result in an increased level of lipid peroxidation. Thus, decreased activities of antioxidant enzymes could contribute to damage of cell membranes and to leaf senescence as demonstrated by increased EL and reduced Fv/Fm, and by decreased chlorophyll content during heat stress. Cultivar variations in antioxidant enzyme activities were associated with their differences in heat tolerance as evidenced by Fv/Fm ratio, chlorophyll content, and EL.
Does Maintaining Green Leaf Area in Sorghum Improve Yield under Drought? II. Dry Matter Production and Yield
Authors: Borrell Andrew K. , Hammer Graeme L. , Henzell Robert G.
Published: July 2010

Retention of green leaf area at maturity (GLAM), known as stay‐green, is used as an indicator of postanthesis drought resistance in sorghum [Sorghum bicolor (L.) Moench] breeding programs in the USA and Australia. The critical issue is whether maintaining green leaves under postanthesis drought increases grain yield in stay‐green compared with senescent hybrids. Field studies were undertaken in northeastern Australia on a cracking and self‐mulching gray clay. Nine closely related hybrids varying in rate of leaf senescence were grown under two water‐limiting regimes, post‐flowering water deficit and terminal (pre‐ and postflowering) water deficit, and a fully irrigated control. Under terminal water deficit, grain yield was correlated positively with and negatively with rate of leaf senescence Grain yield also increased by ≈0.35 Mg ha−1 for every day that onset of leaf senescence was delayed beyond 76 DAE in the water‐limited treatments. Stay‐green hybrids produced 47% more postanthesis biomass than their senescent counterparts (920 vs. 624 g m−2) under the terminal water deficit regime. No differences in grain yield were found among eight of the nine hybrids under fully irrigated conditions, suggesting that the stay‐green trait did not constrain yield in the well‐watered control. The results indicate that sorghum hybrids possessing the stay‐green trait have a significant yield advantage under postanthesis drought compared with hybrids not possessing this trait.
Delayed‐Leaf‐Senescence and Heat‐Tolerance Traits Mainly Are Independently Expressed in Cowpea
Authors: Ismail Abdelbagi M. , Hall Anthony E. , Ehlers Jeffrey D.
Published: July 2010

Reproductive activity in cowpea [Vigna unguiculata (L.) Walp.] is characterized by two separate flushes of pod production. Grain yield from the second flush strongly depends on extent of plant death due to soil pathogens after the first flush is completed. A delayed‐leaf‐senescence (DLS) trait enhances the extent of plant survival but may reduce first‐flush grain yield. Heat tolerance during reproductive development can increase first‐flush grain yield and has been incorporated into cowpea but may reduce plant survival after the first flush is completed. Interactive effects when combining DLS and heat‐tolerance traits were evaluated. A cross was made between a DLS heat‐susceptible line and a non‐DLS heat‐tolerant line. Evaluation and selection for these traits were carried out over several generations and a set of 40 lines with 10 each of the four combinations of DLS +/− heat tolerance and non‐DLS +/− heat tolerance was developed. These lines were evaluated in contrasting field environments. Under senescence‐inducing conditions, the DLS trait greatly increased plant survival and individual seed size, and it only caused a small reduction in first‐flush grain yield that would have been off‐set several fold by an enhanced second‐flush grain yield. The heat‐tolerance trait increased first‐flush grain yield in very hot environments and only slightly enhanced the tendency for premature plant death in non‐DLS lines with no effect on lines having the DLS trait. The DLS and heat‐tolerance traits can be effectively incorporated into cowpea and would have beneficial effects on grain yield in specific circumstances with only small detrimental interactive effects.
Soybean Cultivar Differences in Ureides and the Relationship to Drought Tolerant Nitrogen Fixation and Manganese Nutrition
Authors: Purcell Larry C. , King C. Andy , Ball Rosalind A.
Published: July 2010

Water deficit in soybean [Glycine max (L.) Merr.] results in the accumulation of the products of N2 fixation (ureides) in shoots, and this may lead to feedback inhibition of N2 fixation. Manganese is required for ureide degradation in leaves, and it was hypothesized that increased leaf Mn+2 would alleviate ureide accumulation during drought, lessen feedback inhibition, and prolong N2 fixation. In a growth chamber experiment, ureides supplied through roots decreased N2 fixation in well‐watered plants, and a soybean cultivar with demonstrated tolerance of N2 fixation to water deficit (Jackson) had a lesser concentration of shoot ureides following exogenous ureide application than a cultivar sensitive to water deficit (KS4895). In a greenhouse experiment, N2 fixation in Jackson under moderate water deficit was not different from the control in the absence or presence of soil‐applied Mn+2, whereas N2 fixation in KS4895 was 30% of the control in the absence of soil‐applied Mn+2 and 111% of the control in the presence of soil‐applied Mn+2 Increased N2 fixation in KS4895 with soil‐applied Mn+2 under water deficit was associated with decreased shoot ureide concentration. In field experiments, Jackson consistently had lesser shoot ureide concentrations than did KS4895, and enzymatic degradation of ureides was greater for Jackson on one date than for KS4895. We concluded that ureides inhibit N2 fixation, that genetic variation in the ability to degrade ureides may be important in drought tolerance, and that increased leaf Mn+2 concentration promotes ureide breakdown and prolongs N2 fixation under water deficit.
Influence of Paired‐Row Spacing and Fertilizer Placement on Yield and Root Diseases of Direct‐Seeded Wheat
Authors: Cook R. James , Ownley Bonnie H. , Zhang Hao , Vakoch Dan
Published: July 2010

Root diseases, namely take‐all caused by Gaeumannomyces graminis (Sacc.) Arx & D. Olivier var. tritici J. Walker, Rhizoctonia root rot caused by R. solani Kühn AG8, and Pythium root rot caused by several Pythium Pringsh. species, become yield‐limiting to wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the Inland Pacific Northwest when these crops are grown without adequate rotation, especially in direct‐seed (no‐till) systems. We tested whether yields of wheat could be increased by (i) pairing the rows rather than spacing them uniformly, so as to keep the crop canopy open longer into the growing season, and (ii) placing fertilizer within rather than between the rows, so as to make nutrients more accessible to diseased roots. All experiments were done in fields with a recent history of intensive wheat. Direct seeding was used to further intensify pressure from root diseases, and soil fumigation and/or stubble burning were used in some experiments to reduce pressure from root diseases. Mixed effect models were used to analyze the yield results, with location (observation) treated as the random effect. When all yield data for four winter wheat experiments were used, and spacing, fumigation, and their interaction were the fixed effects in the model, spacing and fumigation but not their interaction were significant. When the yield data were limited to fertilizer placed within each row (directly beneath the seed), spacing, fumigation, and their interaction all were significant. However, when the yield data were limited to fertilizer placed between the rows, or to yields from plots without straw on the soil surface, neither spacing, fumigation, nor their interaction were significant. Similar results were obtained in a spring wheat experiment where fumigation, row spacing, and fertilizer placement were tested in all combinations. Moreover, the amount of Rhizoctonia root rot, take‐all, or both were less in response to paired‐row spacing in two winter wheat experiments. The higher yields can be explained by the microenvironmental benefits of a more open canopy with paired rows together with the concentration of soil disturbance and row cleaning with paired shanks (presumably resulting in more warming and drying of the top soil where the pathogens are most active), and placement of fertilizer directly beneath each seed row, all of which have the potential to reduce the effects of root diseases.
Inheritance of Angular Leaf Spot Resistance in Common Bean and Identification of a RAPD Marker Linked to a Resistance Gene
Authors: Ferreira C.F. , Borém A. , Carvalho G.A. , Nietsche S. , Paula T.J. , Barros E.G. , Moreira M.A.
Published: July 2010

Angular leaf spot, caused by Phaeoisariopsis griseola (Sacc.) Ferraris, is one of the major diseases affecting the common bean (Phaseolus vulgaris L.) in Brazil which can lead to severe yield losses. Previous studies demonstrated that cultivar MAR‐2 was resistant to race 63.39 of P. griseola. The objective of this work was to characterize the resistance to angular leaf spot in MAR‐2 in an F2 population derived from the cross with Ruda (susceptible parent), and also to identify random amplified polymorphic DNA (RAPD) markers linked to the resistance gene. Cultivar MAR‐2 was crossed with Ruda, a “carioca‐type” cultivar susceptible to angular leaf spot, to determine the inheritance of resistance. The results demonstrated that a single dominant gene present in MAR‐2 was responsible for the resistance to P. griseola, race 63.39. Resistant and susceptible DNA bulks from the F2 population were constructed to identify RAPD markers linked to the resistance gene. Amplification with primer OPE‐04 generated a 500‐bp fragment which distinguished the resistant from the susceptible bulk populations. Co‐segregation analysis of the entire population demonstrated that the RAPD marker was linked to the resistance gene at a distance of 5.8 Cm.
Genetic Diversity of Bluebunch Wheatgrass Cultivars and a Multiple‐Origin Polycross
Authors: Larson S. R. , Jones T. A. , Hu Z‐M. , McCracken C. L. , Palazzo A.
Published: July 2010

Bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve = Agropyron spicatum Pursh: Poaceae) is a cross‐pollinating perennial grass native to western North America. Two bluebunch wheatgrass cultivars, Goldar and Whitmar, are currently available for large‐scale rangeland seeding. However, cultivars may lack the genetic diversity and adaptation necessary for dynamic non‐local environments. The objective of this study was to quantify and compare genomic DNA variation within and between Goldar, Whitmar, and Generation 2 of P‐7, a multiple‐origin polycross (MOPX2) of 25 naturally diverse bluebunch wheatgrass collections. We assayed 1043 polymorphic amplified fragment length polymorphism (AFLP) products and 88 monomorphic AFLP products from three sample populations of 22 plants. The number of polymorphic loci (and unique alleles) within sample populations of P‐7, Goldar, and Whitmar was 898 (99), 813 (49), and 746 (59), respectively. Conversely, the number of fixed AFLP loci within sample populations of P‐7, Goldar, and Whitmar was 233, 318, and 385, respectively. The overall nucleotide‐sequence diversity [π ± SE (×1000)] estimated for P‐7, Goldar, and Whitmar was 100.2 ± 7.1, 80.1 ± 6.6, and 79.4 ± 6.7, respectively. By all measures, genetic variation within P‐7 is significantly higher than genetic variation within cultivars. However, the estimated number of inter‐population nucleotide differences per site [dX ± SE (×1000)] between Goldar and Whitmar, e.g., 36.6 ± 1.6, is only slightly higher than π within these cultivars, therefore the net nucleotide‐sequence divergence [dA ± SE (× 1000)] between these cultivars is relatively small, e.g. 2.5 ± 0.3. These results indicate that selectively neutral genetic diversity has not been dramatically reduced or inadvertently lost via genetic drift that may have occurred since the divergence of Goldar and Whitmar. No AFLP markers completely distinguish Goldar and Whitmar, therefore discrete morphological differences between these cultivars (e.g., the presence and absence of awns) most likely result from natural or artificial selection.
Evaluation of the Core Collection Approach for Identifying Resistance to Meloidogyne arenaria in Peanut
Authors: Holbrook C. Corley , Timper Patricia , Xue H. Q.
Published: July 2010

Core collections are representative subsamples of germplasm collections. Use of core collections may improve the efficiency of germplasm evaluations by reducing the number of accessions evaluated while increasing the probability of finding genes of interest. The peanut (Arachis hypogaea L.) core collection has been examined for resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1]. Resistant indicator accessions from screening the core collection identified 39 clusters in the entire germplasm collection that should be examined more thoroughly. The objective of this study was to evaluate how effective a two‐stage core screening approach would be in identifying resistance to M. arenaria in the entire U.S. germplasm collection of peanut. Accessions from 30 clusters having resistant indicator accessions and from four clusters having very susceptible indicator accessions were tested for resistance in two greenhouse trials. This second stage screening identified 259 accessions that had a mean egg‐mass rating of 2.5 or less. Twenty‐eight of these accessions had a mean egg‐mass rating of 1.0 or less. There were relatively large numbers of resistant accessions from China and Japan compared with the percentages of the germplasm collection that originated from these countries. The efficiency of identifying accessions resistant to M. arenaria was greater in clusters having resistant indicator accessions than in clusters having susceptible indicator accessions. These results demonstrate that the use of a two‐stage screening approach with a core collection can improve the efficiency of identifying valuable genes in germplasm collections.
Automated Greenhouse Spray System for Increased Safety and Flexibility
Authors: Rowe D. E. , Malone S. , Yates Q. L.
Published: July 2010

Under EPA's Workers Protection Standard Act of 1992, persons applying pesticide in a greenhouse are usually required to wear protective clothing and a face mask and to breath filtered air. The impervious clothing is usually uncomfortable and may be a health risk via overheating and potential for dehydration. The objective of this research was to devise an automated greenhouse spray system to eliminate hand application. Using off‐the‐shelf components, pesticides are applied at a predetermined time through mist nozzles suspended in greenhouse bays. The automated spray system reduces pesticide exposure to the applicator and others and thus reduces potential liability for the employer, facilitates better control on application rates, is more repeatable than hand application, reduces costs of hazardous waste disposal, and reduces disruption of other greenhouse operations.
Comparison of Three Leaf Area Index Meters in a Corn Canopy
Authors: Wilhelm W. W. , Ruwe K. , Schlemmer M. R.
Published: July 2010

Measurement of leaf area index (LAI) is critical to understanding many aspects of crop development, growth, and management. Availability of portable meters to estimate LAI non‐destructively has greatly increased our ability to determine this parameter during the cropping season. However, with several devices on the market, each with an independent set of protocols for gathering accurate estimates of LAI, it is necessary for scientists to have comparisons of these meters under field conditions before selecting one for purchase and use. The objective of our study was to compare the LAI estimates by three meters (AccuPAR, LAI‐2000, and SunScan) to LAI measured by destructive sampling. Leaf area index of two corn (Zea mays L.) hybrids, grown on a Pachic Haplustoll, was measured at the R2 stage by the four methods before and after successive thinning of plant stands. Destructively sampled LAI ranged from 4.59 to 1.25 for the initial stand to the most severe thinning. Hybrids did not differ in LAI. All meters underestimated LAI compared with destructive sampling. When all data from all rings of the LAI‐2000 meter were included in the calculations, LAI‐2000 estimates of LAI differed from those of the other two meters. However, when data from Ring 5 was removed from the calculations, estimates of LAI for the LAI‐2000 improved and were indistinguishable from the other meters. The relationship between LAI estimated destructively and by each of the meters was described by a unique linear equation for each hybrid. Results of this study, and experience with use of the meters, suggest that users should consider protocols for operating each meter before deciding which device best suits their application.
Adaptations of Endophyte‐Infected Cool‐Season Grasses to Environmental Stresses: Mechanisms of Drought and Mineral Stress Tolerance
Authors: Malinowski Dariusz P. , Belesky David P.
Published: July 2010

Cool‐season grasses infected with Neotyphodium spp. endophytes have an extraordinary impact on the ecology and economy of pasture and turf. A range of adaptations of endophyte‐infected grasses to biotic and abiotic stresses has been identified but mechanisms of these adaptations are not clearly understood. In this review, we present recent research progress on endophyte‐related mechanisms affecting abiotic (drought, mineral) and selected aspects of biotic stress tolerance in cool‐season grasses. Endophytes induce mechanisms of drought avoidance (morphological adaptations), drought tolerance (physiological and biochemical adaptations), and drought recovery in infected grasses. Mineral nutrition (nitrogen, phosphorus, calcium) affects production of ergot alkaloids, thus understanding mechanisms involved in mineral economy of endophyte‐infected grasses will help in developing management practices to reduce forage toxicity to livestock. Previous research resolved the role of endophyte in nitrogen (N) economy of tall fescue. We identified two endophyte‐related mechanisms in tall fescue operating in response to phosphorus (P) deficiency. The mechanisms are altered root morphology (reduced root diameters and longer root hairs) and chemical modification of the rhizosphere resulting from exudation of phenolic‐like compounds. These mechanisms were shown to benefit endophyte‐infected plants grown under P deficiency. We also report a mechanism of aluminum (Al) sequestration on root surfaces in endophyte‐infected tall fescue, which appears to be related to exudation of phenolic‐like compounds with Al‐chelating activity. Understanding mechanisms of abiotic stress tolerance in endophyte‐infected grasses is essential for continued improvement and persistence of grasses for a range of applications, e.g., forage for semi‐arid areas or cover plants for soil renovation.
Monosomics in Soybean: Origin, Identification, Cytology, and Breeding Behavior
Authors: Xu S. J. , Singh R. J. , Hymowitz T.
Published: July 2010

An individual lacking one chromosome is called monosomic and is designated as 2n − 1. Monosomics are useful for locating genes to specific chromosomes and in the assignment of linkage groups. Monosomics are rare in diploid crops. The objective of this study was to determine the origin, morphology, cytology, fertility, and breeding behavior of two spontaneously produced monosomics in soybean [Glycine max (L.) Merr., ]. The two monosomic plants were identified among progenies of triplo 3 (BC3) and triplo 6 (BC4) trisomic plants, backcrossed to ‘Clark 63’ as the recurrent parent. The two monosomics are designated as mono‐3 and mono‐6. The two monosomic and one disomic sibling plants were grown in the greenhouse to evaluate reproductive and morphological traits. Chromosome associations were examined at Metaphase I. F1 hybrids from the crosses of monosomics with Clark 63 and selfed populations were used to evaluate breeding behavior. Morphologically, mono‐6 was similar to the disomic, while mono‐3 was smaller with reduced vigor. Both monosomics showed 19 II + 1 I chromosome association at Metaphase I. Pollen fertility in mono‐3 was 8.8% and in mono‐6 was 20.0%. Mono‐3 and mono‐6 produced 59 and 176 S1 (first selfed generation) seeds. Female transmission (mono‐3 Clark 63) in mono‐3 was 6.5% and self‐pollination yielded 3.5% 2n − 1 offspring. By contrast, mono‐6 was not transmitted among 105 S1 plants, although one plant with 39 normal chromosomes plus one acrocentric chromosome was found. This study demonstrates that monosomics in soybean are viable and fertile, but that the transmission rate is sporadic.
Inheritance and Linkage of Two Genes that Confer Resistance to Fusarium Wilt in Chickpea
Authors: Tekeoglu Mucella , Tullu Abebe , Kaiser Walter J. , Muehlbauer Fred J.
Published: July 2010

Fusarium oxysporum Schlechtend.: Fr. f. sp. ciceris (Padwick) causes a vascular wilt of chickpea (Cicer arietinum L.) and significantly limits production worldwide. The objectives of this study were (i) to determine the inheritance of resistance to races 0 and 5 of fusarium wilt and the genetic map positions of the resistance genes and (ii) to assess the linkage relationships between these two genes and other known wilt resistance genes in chickpea. Seedlings of 131 F6‐derived recombinant inbred lines (RILs) were tested for reaction to races 0 and 5. A 1 resistant:1 susceptible segregation ratio was observed for both races, indicating that resistance to each race is controlled by a single gene. Linkage analysis indicated that the genes for resistance to races 4 and 5 were in the same linkage group and were separated by 11.2 centiMorgans (cM). The gene for resistance to race 0 was not linked to the race 4 and 5 resistance genes. In addition, an allele‐specific associated primer (ASAP) product (CS‐27R/CS‐27F), developed from the CS‐27 primer, was located between the two resistance genes and was 7.2 and 4 cM from the genes for resistance to races 4 and 5, respectively. Map positions of these two race‐specific resistance genes and the marker reported to be linked to the genes for resistance to races 1 and 4 support the hypothesis that wilt resistance genes are clustered on the same chromosome. Since the gene conferring resistance to race 0 is found in a different region of the genome, other genomic regions may be responsible for resistance to wilt pathogens. The gene symbols foc‐0, foc‐4, and foc‐5 are proposed for the genes for resistance to races 0, 4, and 5 of the pathogen, respectively. Identification and further evaluation of disease resistance gene clusters would improve our understanding of wilt resistance in chickpea and facilitate the transfer of resistance genes to new cultivars.
Regulation of Seed Protein Concentration in Soybean by Supra‐Optimal Nitrogen Supply
Authors: Nakasathien Sutkhet , Israel Daniel W. , Wilson Richard F. , Kwanyuen Prachuab
Published: July 2010

The physiological and biochemical basis for increased seed protein concentrations (SPC) observed in restriction‐index, recurrent‐selection breeding programs with soybean [Glycine max (L.) Merr.] are poorly understood. The hypothesis that soybean SPC is regulated by the supply of nitrogenous substrates available to the seed was evaluated. Effects of supra‐optimal external N on seed storage protein accumulation, amino acid concentration and composition in leaves and seeds at R5, and levels of specific storage protein subunits were measured. Genotypes with different SPC (NC 107, normal; N87‐984‐16, intermediate; and NC 111, high) were grown in controlled‐environment chambers and supplied with 30 mM N as NH4NO3 from V5 to maturity or from R5 to maturity. Control plants received 10 mM N throughout the growth cycle. Relative to control, supra‐optimal N increased SPC of NC 107 and N87‐984‐16 by an average of 28%. Greater enhancement of protein accumulation than of dry matter accumulation in the seed resulted in SPCs of 460 to 470 g kg−1, which are appreciably greater than concentrations observed for these cultivars grown in the field. Supra‐optimal N also increased SPC of the high protein line (NC 111) by 15%, but this increase resulted entirely from a decrease in yield. Supra‐optimal N supplied to NC 107 and N87‐984‐16 from V5 until R5 increased total free amino acid concentrations in seeds and leaves at R5 by an average of 21 and 46%, respectively. Enhanced accumulation of the β subunit of β conglycinin which does not contain methionine and cysteine accounted for the increase in SPC. While enhanced N availability increased the SPC of a normal protein line into the high range, availability of sulfur amino acids in the developing seed determined which storage protein subunits were synthesized from the extra N.