bluuebunny/crossref_metadata_2025 huggingface dataset:
Heritability of Resistance in Cowpea to the Western Plant Bug1
Authors: Bosque‐Perez Nilsa A. , Foster Ken W. , Leigh Thomas F.
Published: July 2010

Lygus bugs (Lygus hesperus Knight) reduce both the quality and yield of cowpea [Vigna unguiculata (L.) Walp.]. The objectives this study were to evaluate two expressions of resistance to L. hesperus in cowpea: (i) inhibition of nymphal growth (antibiosis) (ii) level of Lygus‐induced seed damage; and to estimate heritability of resistance. Heritability was estimated in populations derived from crosses between four resistant accessions with ‘California Blackeye 5’ (CBS). For the Cross PI170861 ✕ CBS, heritabilities of antibiosis estimated from the F2 variance and from the variance of F4 family means were 40 and 43%, respectively, whereas the estimate from the parent‐offspring regression (F4 on F2) was only 4%. Thus, single plant evaluations did not provide reliable estimates of nymphal growth‐inhibition. Selection for antibiosis requires progeny testing and/or family selection. Heritability of resistance to Lygus‐induced seed damage was investigated among progenies of the crosses New Era✕CBS, CBS✕PI227829 and CBS✕CR17‐1‐13 (Crosses 1, 2, and 3, respectively). Heritabilities estimated from F2 variances were 49, 65, and 63%, respectively. Heritabilities estimated from variances of F3 family means for Crosses 1 and 2 were 75 and 54%,respectively. For Cross 3, heritability estimated from the variance of F4 family means was 72%. Heritability of resistance to Lygus‐induced seed damage was sufficiently high to indicate probable effectiveness of single plant selection. Seed weight and percent seed damage were not significantly correlated indicating that simultaneous selection for both characters is feasible.
An Evaluation of Ideotype Breeding1
Authors: Rasmusson Donald C.
Published: July 2010

Plant breeders have attempted to enhance yield by selecting for individual traits since the beginning of plant breeding. This approach has been broadened to encompass the breeding of model plants or ideotypes. An ideotype is a hypothetical plant described in terms of traits that are thought to enhance genetic yield potential. Ideotype breeding is defined as a method of breeding to enhance genetic yield potential based on modifying individual traits where the breeding goal (phenotype) for each trait is specified. The purposes of this paper are to elaborate on and evaluate ideotype breeding as a method to enhance genetic yield potential and to describe an ideotype for barley (Hordeum vulgare L.). Successes that have occurred in breeding to enhance yield with individual traits, the value of genetic diversity for individual traits, and benefits from goal setting are presented as arguments in support of ideotype breeding. Alternatively, information is presented on the requirement of symmetry in size among plant parts, compensation among plant parts, pleiotropy, and genetic background, all factors that may slow progress in ideotype breeding. Ranges of genetic diversity, heritability estimates, and introgression information are presented for 27 barley traits. A barley ideotype consisting of 14 traits and the target or goal for each trait are described. Ideotype breeding is recommended as a methodology to augment traditional plant breeding, when the breeding goal is enhancing genetic yield potential. Breeding experience and research to date suggest that ideotype breeding is not a suitable substitute for traditional yield breeding.
Influence of Polyethylene Glycol‐Induced Water Deficits on Tiller Production in Spring Wheat1
Authors: Davidson D. J. , Chevalier P. M.
Published: July 2010

Tillering of wheat (Triticum aestivum L.) is influenced by management practices and environment. Numerous studies have shown that final tiller number in wheat is reduced by drought. This study was conducted to determine the effect of decreasing osmotic potential in the root zone on the production of specific classes of tillers in spring wheat under controlled conditions. ‘Edwall’ and ‘Waverly’ were grown hydroponically in an environmental chamber. In addition to a control, water potential of the hydroponic medium was maintained at −0.1, −0.3 and −0.5 MPa with polyethylene glycol (PEG). Tiller production, leaf area, plant dry weight, and plant water relations were determined during vegetative development. Varying the osmotic concentration in the vicinity of the roots delayed tiller initiation and reduced leaf area production, dry matter accumulation, and the number of tertiary and quarternary tillers. The number of primary and secondary tillers was not affected by the PEG treatments. At 40 days after planting, the water and osmotic potentials of plants growing in the PEG treatments were more negative than the control plants, but the pressure potentials of the treated and control plants were similar. The plants acclimated to the PEG stress by accumulating solutes to lower their osmotic potential and maintain normal turgot. After acclimation, tiller initiation resumed but tillers were small. Thus, tiller initiation and emergence were less sensitive to osmotic stress than was the subsequent vegetative growth of the tillers.
Growth Regulator Effects on Wheat Culm Nonstructural and Structural Carbohydrates and Lignin1
Authors: Knapp J. S. , Harms C. L. , Volenec J. J.
Published: July 2010

Lodging can be a problem when wheat (Triticum aestivum L.) is grown using high rates of N in intensive management systems. The plant growth regulators (PGRs) chlormequat chloride (CCC) (2‐Chloro‐ethyl‐N,N,N‐trimethylammonium chloride) and ethephon [(2‐Chloro‐ethyl)phosphonic acid] often decrease lodging. Our objective was to determine the influence of CCC and ethephon on lodging and on carbohydrate and lignin composition of wheat culms. Water‐soluble carbohydrate (WSC) composition of the peduncle, middle, and lower internodes; and cellulose, hemicellulose, and lignin concentrations in cell walls of the middle and lower internodes were investigated in ‘Arthur 71’ (lodging susceptible) and ‘Auburn’ (lodging resistant) soft red winter wheat. Wheat was planted into a Parr silt loam (fine‐loamy, mixed, mesic Typic Argiudolls) in autumn of 1983 and 1984. Plants were fertilized with 45 and 180 kg N ha−1 and sprayed with CCC and ethephon the following spring. Arthur 71 had a higher lodging rating than Auburn, averaging 1.9 and 0.4, respectively (0.2 to 9 scale). Lodging increased as N fertilization rates were increased and decreased with the application of CCC and ethephon. Culm WSC concentrations averaged 20% higher for Arthur 71 than for Auburn. The low N application resulted in increased WSC concentrations (25% in the peduncle, 21% in the middle internode, and 42% in the lower internodes) compared to high N. Ethephon and CCC resulted in increased WSC concentration as compared to controls. Concentrations of cellulose, hemicellulose, and lignin in cell walls of the middle internode and lower internodes changed less than 5% when comparing cultivars, low N and high N, or controls and PGR‐treated plants. Lodging could not be associated with changes in concentrations of WSC in the culm or with changes in concentrations of structural carbohydrates and lignin in cell walls of the culm. The arrangement and interaction of the various structural carbohydrates and lignin in the culm cell walls may be more important in lodging resistance than concentrations of these components.
Influence of Photosynthetically Active Radiation on Grain Density of Rice1
Authors: Venkateswarlu B. , Vergara B. S. , Visperas R. M.
Published: July 2010

Increasing the number of high density (HD) grains can increase the grain yield of rice (Oryza sativa L.). Studies were conducted on the effect of different levels of photosynthetically active radiation (PAR) on the density of grains. ‘IR36’ was grown throughout its life cycle at 195, 390, and 780 μmol m−2 s−1 in the growth cabinets of the phototron. There was an increased production of spikelets and HD grains (specific gravity >1.20) as PAR increased. The low density (LD) grains also increased as PAR increased. When plants grown previously under natural light were exposed to different PAR after anthesis, the HD grains increased at higher PAR, while the LD grains decreased as PAR increased. The percentage contribution of HD grains to total grain yield emerged as a major determinant of grain yield; thus, cultivars possessing a higher proportion of HD grains would be advantageous even under low PAR. Individual grain weights were higher when plants were exposed to higher PAR after anthesis. The weight of individual grains showed a widerange at lower specific gravities (1.16 to 1.20) than at higher specific gravities (> 1.20). Spikelet and grain number per hill showed high positive correlation with shoot weight per hill. High density grains had a positive but lower correlation with shoot weight, indicating a possible limitation in production or transport of assimilates as HD grains were not realized in all the filled spikelets regardless of PAR level. High PAR from flowering to harvest can greatly increase the number of HD grains, which contributes to higher grain yield.
Yield Components Related to Seed Yield in Determinate Soybean1
Authors: Board J. E.
Published: July 2010

Studies were conducted to determine which yield components were correlated with seed yield among eight determinate soybean [Glycine max (L.) Merr.] cultivars. Soybean cultivars were planted in early April, mid‐May, and mid‐June in 1981 and 1982 at Baton Rouge, LA (30° N lat) on an Olivier silt loam (fine‐silty, mixed, thermic Aquic Fragiudalfs) soil. At maturity, plant samples were separated into main and branch stem components. Main and branch stem length, branch number, node number, fertile node number, pod number, pods per fertile node, seed per pod, seed size, and seed yield were determined. Across planting dates, cultivars, and years, seed yield was more closely related to number of seed (r = 0.69**, significant at the 0.01 probability level) than to seed size (r = 0.20**) or seeds per pod (r = 0.11). Seed yield was also highly correlated with number of pods, number of fertile nodes, and number of nodes, but not with pods per fertile node or with the percentage of nodes becoming fertile. Observations indicated that branch portions resulted in higher correlations than did main stem portions. Results indicate that these branch yield components maybe useful criteria in selecting higher yielding cultivars.
Relationship between Plant Height and Flowering Date in Determinate Soybean
Authors: Lin Maw Sun , Nelson Randall L.
Published: July 2010

There is increasing interest in growing determinate soybean [Glycine max (L.) Merr.] in the northern USA because of their yielding ability and lodging resistance. These cultivars are approximately half as tall as indeterminate cultivars. The objectives of this study were to estimate the heritabilities of days to R1 and R8, and plant heights at R1 and R8; and to evaluate the relationships among these traits to assess the possibility of selecting tall determinate plants with early flowering. Two determinate populations derived from PI 407711B ✕ PI 360835 and PI 417398 ✕ PI 423882A, were used. These two populations (containing 42 and 43 F2 families) were studied in the F3 and F4 generation in 1984 and 1985, respectively, at Urbana, IL in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll). A randomized complete‐block design with two replications was used for each population each year. Heritabilities estimated by parent‐offspring regression were high (0.67–1.21) for days to RI and R8, and for plant heights at these two stages except for days to R1 in one population (0.49). Positive genotypic and phenotypic correlations between days to R1 and R8, and plant height indicated obtaining tall, determinate plants with early flowering would be difficult. Main stem growth continued 1 week or more after R1. Plant height at R1 represented approximately 80% of the final plant height. Thus, selection for plant height can be effective at as early a stage as R1 for determinate soybean.
Inheritance of Resistance to Macrophomina phaseolina (Tassi) Goid. and Fusarium moniliforme Sheldom in Sorghum
Authors: Bramel‐Cox P. J. , Stein I. S. , Rodgers D. M. , Claflin L. E.
Published: July 2010

Lodging of grain sorghum [Sorghum bicolor] a serious problem under certain environmental conditions such as water stress or heat stress. Lodging at the base of the stalk or the base of the panicle has been attributed to a complex of stalk rotting organisms, which includes Macrophomina phaseolina (Tassi) Goid and Fusarium moniliforme Sheldon. The field study reported here evaluated the use of a toothpick inoculation technique to artificially infect plants with these two organisms and determined inheritance of resistance. The experimental material consisted of the 45 F1's from a 10‐parent diallel with no reciprocals, the 10 parents, and five hybrid checks grown in 2 yr under two water regimes. The inoculated and noninoculated plants in a plot were rated for stalk disintegration on a scale of 1 (resistant) to 6 (susceptible). Hybrids differed nificantly and consistently across environments for the two inoculation treatments but not for the noninoculated. General combining ability was significant in both dryland environments for both inoculation treatments; specific combining ability was significant for F. moniliforme in both years but only in 1984 for M. phaseolina. The expression of resistance seems to depend upon the environment, especially for F. moniliforme.
Nitrogen Allocation with Altered Sink Demand in Wheat
Authors: MacKnown C. T. , Van Sanford D. A.
Published: July 2010

Wheat (Triticum aestivum L.) grain N is derived concurrently from mobilization of vegetative N accumulated prior to anthesis and soil N absorbed after anthesis. The effect of main stem spike removal on N redistribution, total tiller grain yield, and total grain N yield was determined to assess the relationship between N utilization and reproductive sink demand. The soft red winter wheat cultivar ‘Hart’ was field grown on a Maury silt loam soil (fine, mixed, mesic, Typic Paleudalf). Net changes in tissue N contents and allocation of 50 μmol of 99 atom % 15N‐NH+4 injected into the main stem penultimate internode were determineduring grain fill. Senescence of main stem vegetative tissues, as indicated by net loss of vegetative N, was equivalent for plants with main stem spikes intact (control) and plants with only main stem spikes removed (‐spike). However, after anthesis negligible main stem injected 15N was allocated to control tillers, whereas the tillers of the ‐spike treatment contained 69% of the aboveground excess 15N at maturity. Even though the main stem vegetative N of the ‐spike treatment was allocated to the tillers, grain yield was not significantly increased compared to the control. There was a trend for increased tiller N yield such that total N yield of the ‐spike treatment was 12% less than the control, whereas plant total grain yield of the ‐spike treatment was 21% less than the control. These results indicate that senescence proceeds normally in stems lacking a reproductive sink, provided that alternate tiller sinks are present. Furthermore, effects of reduced sink demand appear to have a greater impact on plant grain yield than on plant N yield.
Seedling Root Development and Morphology of Cool‐Season and Warm‐Season Forage Grasses
Authors: Newman P. R. , Moser L. E.
Published: July 2010

A detailed description of grass seedli ng root morphology is essential to understand the differences in the establishment process among grasses. A repeated greenhouse study using a 1:1 mixture of Sharpsburg silty clay loam (fine, montmorillonit|c, mesic Typic Argiudolls) and coarse sand was conducted to determine root morphology differences at the third‐leaf stage among nine cool‐season forage grasses, creeping foxtail (A1opecurus arundinaceous Poir., reed canarygrass, (Phalaris arundinacea L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), russian wildrye (Elymus junceus Fish.), crested wheatgrass [Agropyron cristatum (L.) Gaertn.], intermediate wheatgrass [A. intermedium (Host) Beauv.], and western wheatgrass (A. smithii Rydb.); and nine warm‐season forage grasses, sideoats grama [Bouteloua curtipendula (Michx.) Tort.], blue grama [B. gracillis (H.B.K.) Lag. ex. Steud.], sand lovegrass [Eragrostis trlchodes (Nutt.) Wood], big bluestem (Andropogon gerardii var. gerardii) Vitman), sand bluestem [A. gerardii var. paucipilus (Nash) Fern.], little bluestem [Schizachyrium scoparium (Michx.) Nash], caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hobb.], indiangrass [Sorghastrum nutans (L.) Nash], and switchgrass (Panicum virgatum L.). These grasses were selected as representative forage grasses of the northern USA. Andropogoneae species reached third leaf emergence 3 to 5 days earlier than other warm‐season grasses and 3 to 15 days earlier than cool‐season grasses. Most cool‐season grasses had no or little subcoleoptile internode elongation except Aveneae species. Aveneae species and warm‐season grasses, except Chlorideae species, had root development from the subcoleoptile internode. Sand bluestem had less subcoleoptile internode root development than big bluestem. Seminal root development was greater in species of the Triticeae tribe. Adventitious root development occurred by the three‐leaf stage on species of all tribes except for Andropogoneae members. Most grasses were in a juvenile period of root growth at third leaf emergence. Stage of root development did not coincide with stage of shoot development among species.
Nitrogen Effects on Soft Red Winter Wheat Yield, Agronomic Characteristics, and Quality
Authors: Brucker P. L. , Morey D. D.
Published: July 2010

Research conducted in the USA in recent years has verified that grain yields of soft red winter (SRW) wheat (Triticum aestivum L.) can be increased by intensification of management procedures, including higher N fertilization. Relatively little information has been reported on how N, cultivar, and their interaction influence end use qualities of SRW wheat. Field studies were conducted in 1983 and 1984 on a Greenville sandy clay loam (clayey, kaolinitic, thermic Rhodic Paleudults) to determine the influence of applied N on above ground biomass, grain yield, kernel weight, and grain protein of five SRW wheat cultivars. Nitrogen effects on tiller density, kernels per head, and SRW wheat milling and baking quality were determined in 1983 but not 1984. Nitrogen treatments were 0, 33.6, 67.2, 100.8, and 134.4 kg N ha‐1, applied as two equal topdressings between the tellering and early jointing growth stages. Nitrogen and cultivar affected all response parameters. Nitrogen × cultivar interactions were important only for grain protein content. Biomass and grain yield were maximized with 106 and 94 kg N ha‐1, respectively. As N rate increased, grain protein, tiller density, and kernels per head increased, while harvest index and kernel weight decreased. Nitrogen rates in excess of 67 kg N ha‐1 caused luxurious N consumption and contributed to undesirable grain protein increases in both years, and reduced SRW wheat milling and baking quality by increasing flour protein and endosperm hardness in 1983. ‘Omega 78’ was more adapted to higher N regimes than the other cultivars evaluated, producing the highest grain yield and lowest average grain protein content, having superior overall milling and baking qualities, and having the most favorable grain protein response pattern to increased N rates.
Comparison of Selection Systems for the Identification of Exotic Soybean Lines for Use in Germplasm Development
Authors: Reese P. F. , Kenworthy W. J. , Cregan P. B. , Yocum J. O.
Published: July 2010

Hybridization programs utilizing exotic soybean [Glycine max (L.) Merr.] germplasm might be more successful if selection systems were used to identify plant introductions (PIs) that combine well with adapted genotypes to produce high‐yielding breeding populations. The objectives of this study were to compare PIs selected for visual appearance vs. yield using a topcross procedure (TCP), compare the performance of PI parents with their progeny utilizing a TCP, to compare the performance of testers used in the topcross, and to identify PIs that combine well with adapted genotypes to produce high‐yielding progeny. Nine PIs selected for desirable visual appearance and 14 yield‐selected PIs were each crossed to four adapted lines in a TCP. The 92 F2 bulks were evaluated along with the 23 PIs and four adapted testers in three environments with two replications per environment. The F2 bulks produced from the yield‐selected PIs had a mean yield of 2669 kg/ha, which was significantly (P < 0.01) greater than the yield (2566 kg/ha) of the F2 bulks produced from the visually selected PIs. A positive correlation (r = 0.65; P < 0.01) between PI parent yield and PI group yield (mean of four F2 bulks with a common PI parent) demonstrated good association for yield between parent and progeny. Selecting PIs for yield, per se, appeared to be the more efficient method to identify desirable PIs for germplasm development programs. Our results indicate that the choice of a tester would not be critical if a TCP was utilized. The plant introductions PI 85469, PI 88306, and PI 88486 produced the three highest‐yielding PI groups and, therefore, are recommended for germplasm development programs in the mid‐Atlantic states. We suggest that these three PIs be evaluated in other geographic regions. The F2 bulks generally had acceptable lodging resistance, seed qualities, and seed weights.
Photoperiod and Planting Date Effects on the Spatial Distribution of Branch Development in Soybean
Authors: Settimi J. R. , Board J. E.
Published: July 2010

Reduced branch development in late‐planted soybean [Glycine max (L.) Merr.] is a cause of yield reductions in the southeastern USA. To determine the effects of photoperiod and planting date on the spatial distribution of branches, photoperiod simulations of an optimal (24 May) and a nonoptimal late planting date (24 June) at Baton Rouge, LA (30°N Lat), were imposed on ‘Centennial’ soybean in growth chambers. In a field study, ‘Lee 74’ was planted at optimal (mid‐May) and nonoptimal (early July) planting dates in 1984 and 1985 at Baton Rouge, LA, on an Olivier silt loam (fine‐silty, mixed thermic Aquic Fragiudalf) soil. Plants grown under the May stimulated photoperiod had greater total branch length and concentrated their branches in the lower and middle sections of the plant. Under the June simulation, there was little branch development below the sixth main axis node, with most branches occurring on the middle and upper sections of the plant. Total branch length and branch number were reduced in the July field planting as compared to the May planting. This was related to the failure of branches to form in the axils of the lower main axis nodes and by the lack of upper main stem nodes from which branching could occur. Main stem seed yield was greater in the July compared to May planting date. The photoperiod of a late nonoptimal planting date thus restricts branch development at the lower nodes through a direct influence on the formation of branches and at the upper nodes through indirectly reducing the potential sites for branch development by promotion of early flowering.
Influence of Leaf Grafting on Leaf Constituents and Senescence Characteristics of Burley and Flue‐Cured Tobacco
Authors: Crafts‐Brandner S. J. , Sutton T. G. , Sims J. L.
Published: July 2010

Productivity of flue‐cured tobacco (Nicotiana tabacum L.) is similar to that of burley tobacco in spite of the former's lower need for N fertilizer. The objective of this study was to utilize a leaf grafting technique to demonstrate the level of control of an individual leaf with regard to the unique characteristics of burley and flue‐cured tobacco cultivars. Leaves of burley cultivar ‘Ky 14’ were grafted onto shoots of flue‐cured cultivar ‘Speight G28’ (G28) and visa versa and compared to both grafted and nongrafted controls of a particular cultivar. Plants were grown in a greenhouse at two N fertility levels (648 or 144 mg N wk−1). Leaf grafting decreased leaf growth of both the burley and the flue‐cured cultivar compared to nongrafted controls, but relative cultivar differences were maintained. Compared to Ky 14, G28 leaves accumulated more dry weight, due primarily to greater starch accumulation, had higher chlorophyll concentration and, at low N fertility, maintained a higher carbon dioxide exchange rate (CER) and ribulose 1,5‐bisphosphate carboxylase/oxygenase (rubisco) concentration. Grafting a Ky 14 leaf onto a G28 stalk or a G28 leaf onto a Ky 14 stalk did not alter dry weight, starch, or N characteristics of the grafted leaf. Leaf senescence, however, as indicated by loss of chlorophyll, CER, and rubisco, was delayed for Ky 14 leaves grafted onto G28 stalks. For G28 leaves grafted to Ky 14 stalks, loss of chlorophyll was hastened, but declines in CER and rubisco were not altered. The results indicated that cultivar differences in dry weight and starch accumulation were controlled by biochemical or physical factors within an individual leaf, but that senescence characteristics of individual leaves could be influenced by the plant genotype.
Photoassimilate Partitioning by Tillers and Individual Tiller Leaves in Field‐Grown Spring Barley
Authors: Lauer Joseph G. , Simmons Steve R.
Published: July 2010

A large proportion of initiated tillers on field‐grown barley (Hordeum vulgare L.) plants does not survive to bear grain. Increasing the percentage of tillers that survive has been hypothesized as an approach for increasing yield. The objective of this study was to determine photoassimilate translocation patterns of surviving and nonsurviving tillers in barley and to begin assessing the consequences of premature tiller senescence on grain yield. Field experiments were conducted in 1983 and 1984 at St. Paul, MN, on a Waukegan silt loam soil (Typic Hapludoll) using a replicated, randomized complete block design. Entire shoots, as well as individual tiller leaves, were labeled with 14CO2 in separate experiments. Following a 24‐h translocation period, the three genotypes evaluated did not differ in their fundamental tiller photoassimilate partitioning patterns. Nonsurviving tillers allocated proportionately more photoassimilate to the main shoot than surviving tillers, with the main shoot stem and emerging leaves receiving most of the photoassimilate. After onset of stem elongation, surviving tillers translocated proportionately less photoassimilate to the main shoot. During this time, the tiller stem received most of the photoassimilate fixed by a surviving tiller. From these experiments, we conclude that tillers, and especially nonsurviving tillers, may contribute appreciable quantities of current photoassimilate to the main shoot during early stem elongation, a factor that should be considered in assessing the agronomic value of tillers in barley.
Relationships among Daily Flower Production, Length of the Flowering Period, and Seed Yield of Flax
Authors: Dybing C. Dean , Evenson P. D. , Lay C.
Published: July 2010

The number of flowers produced each day is easily determined for flax (Linum usitatissimum L.). An analysis of daily changes in flower production should reflect genetic, environmental, and edaphic effects on an important component of seed yield, namely fruits per area, because of the direct relationship between flower and fruit numbers in this crop. The objectives of this study were to develop techniques for analyzing flower count data for ‘Linott’ flax; to relate flower counts and their transformations to total flower production, length of flowering stage, and seed yield; and to relate weather data to the same characteristics. Flower production and seed yield varied markedly in seven field trials over 6 yr. Total flower count and length of flowering were closely correlated. Equations with high coefficient of determination were obtained for both by regression using easily obtained flowering measures as independent variables. Seed yield had high positive correlation to calendar dates of maximum daily flower count and last flower, but was not closely related to maximum daily flower count, total count, or length of flowering. Years when daily flower production rate increased rapidly with little lag phase were low in yield. High coefficients of determination for yield were obtained using relative flower count (flowers flower−1 d−1), calculated similarly to relative growth rate in plant growth analysis, and daily count (flowers m−2) for 1 to 4 d of the flowering period as independent variables. Regression of weekly mean air temperature, soil temperature, precipitation, and wind on yield also resulted in high coefficients of determination. It is concluded that the calendar dates of certain flowering events and how flowering rate changed with time were more important for seed yield in Linott than length of the flowering period.
Establishment of Red Fescue Seed Crops with Cereal Companion Crops. II. Seed Production and Economic Implications
Authors: Chastain T. G. , Grabe D. F.
Published: July 2010

The influence of companion crops on red fescue (Festuca rubra L.) seed production and net income over a 3‐yr period was investigated. ‘Pennlawn’ red fescue was interplanted in 1982 and 1983 with cereal companion crops near Corvallis, OR, on Woodburn silt loam (fine‐silty, mixed, mesic Aquultic Argixeroll) soil. ‘Yamhill’ and ‘Hill 81’ winter wheat (Triticum aestivum L.), and ‘Hesk’ and ‘Scio’ winter barley (Hordeum vulgare L.) were planted in 15‐, 30‐, 45‐ and 60‐cm rows at right angles to red fescue rows. Although companion crops adversely affected red fescue growth during establishment, first‐year seed yield in the first experiment was not significantly reduced. Red fescue seed yields ranged from 490 kg ha−1 when planted with Hill 81 wheat to 654 kg ha−1 with Scio barley, whereas yield without a companion crop was 589 kg ha−1. First‐year seed yield was somewhat depressed in the second experiment by the wheat cultivars and Hesk barley, but not by Scio barley. Yields ranged from 908 kg ha−1 for red fescue planted with Hill 81 to 1008 kg ha−1 with Scio, whereas 1177 kg ha−1 was obtained with no companion crop. Second‐year seed yield was not affected by companion crops in either experiment. Establishment with Yamhill wheat increased net income over a 3‐yr period by U.S. $508 ha−1 over red fescue established alone, whereas planting with Hesk barley produced the lowest increase in net economic returns, $211 ha−1. Red fescue seed production was most profitable when wheat companion crops were planted in 15‐cm rows. This study demonstrates the potential for profitable and reliable establishment of red fescue seed crops with cereal companion crops in Oregon.
Identification and Quantification of Abscisic Acid in Zoysiagrass Seeds and Its Inhibitory Effect on Germination
Authors: Yeam Do Yi , Mandava N. Bhushan , Terry Paul H. , Murray J. Jack , Portz H. L.
Published: July 2010

Seed dormancy has been a major limiting factor in the use of zoysiagrass (Zoysia japonica Steud.) for turf. The identification of the major dormancy factors and their mode of action would increase the potential for developing seed treatments to break dormancy. Abscisic acid (ABA), a well‐known seed dormancy‐inducing substance found in the dormant seeds of many temperate perennial weeds and grasses, was confirmed and quantified in Zoysiagrass seed. High performance liquid chromatography was used to purify the seed extract, gas chromatography/electron capture was used to quantitate the amount of ABA present in the seeds via the methyl ester, and further verification of the compound in the seed as ABA was made using masspectrometry. The quantity of the cis, trans isomer found, 3.44 mg ABA kg1 seed, is the highest level of ABA reported for any seed. There was no trans, trans isomer found in zoysiagrass seed. The high level of ABA may be the reason that dormancy is so difficult to break in zoysiagrass seed. Exogenous ABA applied to nondormant (KOH and light treated) seed inhibited germination. Germination after 21 d was reduced 69 and 95% by 0.4 and 40.0 μM of ABA, respectively. The promotive effects of light on germination were reversed by ABA applications. A positive relationship was found between ABA concentration and the duration of light required for germination.
Effect of X‐ray Irradiation on Maize Inbred Line B73 Tissue Cultures and Regenerated Plants
Authors: Wang A. S. , Cheng D. S. K. , Milcic J. B. , Yang T. C.
Published: July 2010

In order to enhance variation induced by the tissue culture process and to obtain agronomically desirable mutants, friable embryogenic tissue cultures of maize (Zea mays L.) inbred line B73 were x‐ray irradiated with 11 doses [0–8.4 kilorads (kR)]. Reductions in callus growth rate and embryogenic callus formation occurred with increasing x‐ray doses 20 d and 3 months (90 d) after irradiation. Callus irradiated with 0.8 kR showed a significant increase in growth rate and a 20% increase in embryogenic callus 9 months (270 d) after irradiation. A total of 230 R0 plants were regenerated for evaluation. Pollen fertility and seed set of R0 plants decreased with increasing x‐ray dosage. Days to anthesis and plant height of R0 plants varied among x‐ray treatments but were generally reduced with higher dosages. The number of chromosomal aberrations increased with x‐ray dosage. The R1 seeds taken from R0 plants were also grown and tested for mutant segregation. Plants regenerated from irradiated calli had a two‐ to 10‐fold increase in mutations over plants regenerated from unirradiated control callus. Germination frequency of seeds from R0 plants decreased with increasing x‐ray dosage. Although chlorophyll mutants were most frequently observed, a number of vigorous plants with earlier anthesis date were also recovered.
Seedling Tolerance to Aluminum Toxicity in Hard Red Winter Wheat Germplasm
Authors: Carver Brett F. , Inskeep William P. , Wilson Nancy P. , Westerman Robert L.
Published: July 2010

Critically acid soils (pH < 5.0) now exist in the major wheat (Triticum aestivum L.) production areas of the Southern Great Plains. This condition has encouraged the identification and development of hard red winter (HRW) wheat genotypes that can tolerate higher amounts of soluble soil AI. The objectives of this research were to identify Al‐tolerant HRW genotypes better adapted to soils high in soluble Al and to determine alternative gene sources. Seedlings were grown in nutrient solutions containing 0.18, 0.36, and 0.72 mM AI. As a measure of tolerance, the degree of staining on root tips of 5‐d‐old seedlings was visually scored after exposure to hematoxylin. A total of 156 HRW pureline cultivars, ancestors, and parental lines used in HRW breeding programs was classified into four tolerance levels, i.e., very susceptible (54%), moderately susceptible (15%), intermediate (14%), and tolerant (17%). Several ancestors from other wheat classes showed intermediate or tolerant responses including ‘Kenya 58’, ‘Mediterranean’, ‘Purplestraw’, and ‘Red Fife’; yet, the predominant ancestor of HRW wheat, ‘Turkey’, was very susceptible. Eight of the 16 tolerant USA cultivars shared similar pedigrees, and thus probably shared the same source(s) of Ai tolerance (i.e., ‘Sonora 64’ and ‘Trapper’). Confirmed sources of tolerance in remaining cultivars included ‘Centurk’ and ‘Prelude’, although several were derived from parents classified as very susceptible. Nine of the 15 intermediate USA cultivars were separated into two groups based on their distantly related Al‐tolerant parents (Kenya 58 and Prelude vs. Mediterranean). In summary, AI tolerance in HRW wheat could not be traced in a single lineage to any single ancestor or to a set of closely related lines. These results provide an information base to test for different genes among sources and to help develop recommendations of more tolerant cultivars for acid soils high in soluble AI.
Resistance of Corn to Southern Root‐Knot Nematode
Authors: Williams W. Paul , Windham Gary L.
Published: July 2010

Root‐knot nematodes, Meloidogyne spp., are frequently associated with corn, Zea mays L., in the southern USA. Limited information is available on resistance of corn to these nematodes; however, recent investigations indicated that their reproduction varied among green‐house‐grown inbred lines of corn. This investigation was undertaken to evaluate the performance in crosses of inbred lines showing different levels of resistance to M. incognita and to obtain information on the relative importance of general and specific combining ability. Eight inbred lines exhibiting varying levels of resistance were selected as parents of a diallel cross. Seedlings of the 28 F1 hybrids and the parental inbred lines were evaluated for reaction to inoculation with 3000 M. incognita (Race 4) eggs per plant. After 60 d, the roots were washed and weighed, eggs extracted and counted, and nematode reproduction determined. An analysis indicated that both general and specific combining ability were significant sources of variation in the inheritance of resistance to nematode reproduction. Inbred line Mp307 showed the lowest nematode reproduction (510 eggs/g fresh root) and T216, the highest (4134 eggs/g fresh root). The Mp307 also showed superior general combining ability for resistance whereas hybrids with T216 as one parent were among the most susceptible. Resistance to reproduction of M. incognita is available for developing resistant corn hybrids.
Polygenes in Diploid Alfalfa That Affect Resistance to Downy Mildew
Authors: Skinner D. Z. , Stuteville D. L.
Published: July 2010

The genetics of resistance in alfalfa (Medicago sativa L.) to downy mildew (caused by Peronospora trifoliorum d By.) is complex. Our previous studies with diploid alfalfa indicated that resistance (absence of conidial production) resulted from single dominant genes in some plants, and combinations of minor genes in other plants. The present sludy was conducted with diploid plants possessing only minor resistance genes to determine if different combinations of minor genes conditioned a single disease phenotype, and to determine the dominance relationships of the alleles involved. A seedling test was used in which downy mildew symptoms were described on a 0 (resistant, no conidial production) to 5 (very susceptible, copious conidiai production) infection type (IT) scale. Chi‐square analysis of progeny IT data revealed that 30% of paired plants with the same IT were genetically different. Most F2 plants from resistant F1, plants were resistant, whereas susceptible F1, plants produced F2's of all disease scores, including resistance. This was consistent with dominant susceptibility at most loci, and additivity of effects among loci.
Evaluation of Screening Techniques for Breeding Drought‐Resistanct Winter Wheat
Authors: Winter S. R. , Musick J. T. , Porter K. B.
Published: July 2010

Effective screening techniques for drought resistance would be beneficial in a winter wheat (Triticum aestivum L.) breeding program. Several greenhouse and field screening techniques were evaluated for abilily to differentiate drought resistance in five cultivars reputed to differ in drought resistance and yield: Scout 66, Sturdy, TAM W‐101, TAM 105, and TAM 108. Grain yield for droughtstressed and irrigated conditions was determined in field trials on Pullman clay loam soil (fine, mixed, thermic Torrertic Paleustoll). Yield ranking, both irrigated and drought stressed, was: TAM 108 ≧ TAM 105 > TAM W‐101 = Scout 66 ≧ Sturdy. Drought susceptibility index (S) values were: 0.55, 0.57, 0.59, 0.63, and 0.63, for Scout 66, TAM 105, TAM W‐101, Sturdy, and TAM 108, respectively. These values indicate that Scout 66 has the greatest yield stability in drought, while Sturdy and TAM 108 have the least. Screening techniques that were unsuitable because they did not differentiate cultivars were germination in mannitol, rooting depth, leaf conductance, and canopy temperature. Seedling root length appeared unsuitable because of limited cultivar differentiation and high labor requirement. Seedling survival after desiccation was the most suitable technique for screening large populations. Water loss of excised leaves and leaf water potential (Ψ) are labor intensive but would be informative screening techniques for parental material and advanced lines. Water loss of excised leaves was correlated with S (least loss = lowest S). High yield was associated with low Ψ, which may be associated with high ability to retain green leaves in drought
Callus Induction and Plant Regeneration in Elite U.S. Rice Lines
Authors: Oard J. H. , Rutger J. N.
Published: July 2010

Four California and one Texas rice (Oryza sativa L.) cultivars were examined for potential use in tissue culture studies. Under varying 2,4‐dichlorophenoxyacetic acid (2,4‐D) and kinetin levels embryogenic calli derived from mature seed ranged in weight from 0 to 502 mg after 4 wk. Addition of kinetin allowed a 2‐ to 10‐fold increase in embryogenic callus size for ‘M‐202’, ‘Calmochi‐101’, and ‘Lemont’. The frequency of embryogenic callus formation across different 2,4‐D and kinetin levels was highest with ‘S‐201’ (0.93 to 1.00) and lowest with Lemont (0.00 to 0.44). Mean green shoot number varied from 0 to 14.2 (100 mg)−1 embryogenic callus 8 wk after initiation of regeneration. Similar numbers of shoots were derived from compact, friable, and leafy callus types. S‐201 and Calmochi‐101 developed green shoots from virtually all regions of the embryogenic callus while the others formed shoots from the underside of regenerating tissue. Frequency of albino shoots ranged from 0.00 to 0.045 for the five cultivars. Albino shoots from California cultivars were detected only in regeneration medium containing 0.1 mg L−1 6‐benzylaminopurine (BAP). L‐202 and S‐201 were identified as the best cultivars for cell culture studies. Data from these cultivars suggest that the California rice germplasm should respond equally as well to in vitro manipulation as other non‐U.S, strains.
Compatibility of Metalaxyl with Rhizobium Meliloti on Alfalfa Seed to Control Pythium Damping Off
Authors: Edmisten K. L. , Wolf D. D. , Stromberg E. L.
Published: July 2010

Metalaxyl [N‐(2,6‐dimethylphenyi)‐N‐(methoxyacetyl)‐alanine methyl ester], an acylalanine fungicide, has been reported to be effective in controlling fungi in the order Peronosporales. Metalaxyl shows promise for control of Phytophthora root rot (Phytophthora megasperma Drechs.) and damping‐off (Pythium spp.) in seedling alfalfa (Medicago satlva L.) if seed treatment does not interfere with the N2‐fixing bacterium (Rhizobium meliloti Dangeard). Spring nofill plantings often are made earlier where fall‐applied herbicide is used to suppress sod. Plantings made in cooler weather are more susceptible to seed‐ and soil‐borne diseases. Compatibility of this fungicide with R. meliloti when used as a seed treatment was determined using the most‐probable‐number technique, by measuring seedling growth, total seedling crude protein, and N2 fixation as estimated by acetylene reduction. Metalaxyl had no detrimental effect on viability or N2‐fixing capability of R. melilotl at recommended rates of application. Under growth chamber conditions, metalaxyl increased seedling survival by 45 to 60% over nontreated P. ultimum Trow infested controls.
Evaluating Soybean Germplasm for Specific Leaf Weight
Authors: Nelson Randall L. , Schweitzer Lee E.
Published: July 2010

Specific leaf weight (SLW) defined as the mass of tissue per unit leaf area has been positively correlated with leaf photosynthesis in several species and has therefore been suggested as a potentially useful selection criterion. Little research has been done to assess the range in genetic variability of SLW in soybean [Glycine max (L.) Merr.] as a first step in evaluating the potential of selection for SLW. In previous reports, comparisons of SLW among lines of differing maturity have been confounded with environmental conditions associated with the various sampling times. The objectives of this research were to determine the phenotypic variability of SLW that exists in a portion of the Maturity Group I soybean germplasm of comparable maturity, and to estimate the genetic component of that variability. Four leaf discs, 8.7 mm in diam., were cut from each of two leaflets of five plants for 231 Maturity Group I accessions in the USDA soybean germplasm collection. One leaflet each was collected from the most recently fully expanded leaf and the next youngest leaf on each plant between R5 and R6 growth stages. All selected leaves were in an unshaded position in the canopy and sampled near solar noon on clear sky days. Plots were grown at Urbana, IL in 1983 and 1984 and at West Lafayette, IN in 1984 with one replication in each environment. Averaged across all locations and years accession means for SLW ranged from 47 to 86 g m−2. ‘Hodgson 78’ replicated nine times in each 1984 environment, had a mean SLW of 62 g m−2. Repeatability for SLW was 0.48 indicating that effective selection for this trait should be possible.
Morphology, Anatomy, and Distribution of Capitate Glandular Trichomes on Selected Trifolium Species
Authors: Retallack Beth , Willison J. H. Martin
Published: July 2010

Glandular trichomes may impart insect resistance to crops. This study was conducted to determine the morphology, anatomy, and distribution of glandular trichomes on Trifolium pratense L., T. medium L., T. hybridum L., and T. repens L. Fluorescence microscopy, scanning electron microscopy, and transmission electron microscopy were used to facilitate this study. Procumbent and erect glandular trichomes were found on cultivars of these species. Both procumbent and erect glands arose from epidermal cells, were capitate, and had thick‐wailed stalks. The heads of the procumbent glands were long and thin, consisting of four to eight layers of cells, each layer consisting of one to four cells. By contrast, the heads of the erect glands were globose and not organized in layers, although they were multicellular. Leaves, stems, peduncles, and sepal surfaces had procumbent and erect glands. All floral organs, other than sepals, were devoid of procumbent glands, except in alsike clover (T. hybridum L.) specimens, where these glands were found on the gynoecium. Tissue‐culture grown white clover (T. repens L.) leaflets showed the greatest density of procumbent glands, these being located abaxially only. Erect glands frequently appeared on petioles and on foliar margins, near vein endings, and in association with simple (vegetative) hairs. On the basis of previous evidence, it is proposed that the two kinds of glandular trichomes present on these Trifolium species may be involved in plant defense.