bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Air Temperature and Water Stress on Apex Development in Spring Wheat1
Authors: Frank A. B. , Bauer A. , Black A. L.
Published: July 2010

Grain yield of hard red spring wheat (HRSW) (Triticum aestivum L.) is influenced by the number of spikelets produced per spike. There is a need to better understand, for predictive purposes, the effects of water and temperature on apex differentiation, spike and spikelet development, and number of spikelets. The effects of these two factors on apex development and number of spikelets produced per spike were studied in a controlled environment using ‘Sinton’ HRSW. Data on spikelets per spike from field studies conducted at Mandan, ND were included to evaluate temperature effects during the spikelet development phase on number of spikelets formed per spike. Plants grown at 18°C for 4, 8, or 12 days from emergence, and thereafter at 26°C required less time to reach double ridge and terminal spikelet development stage, had a shorter spikelet development period, and produced fewer spikelets per spike than plants grown initially at 26°C for 4, 8, and 12 days and thereafter at 18°C. These data indicated that higher air temperature (26°) from about 6 to 8 days prior to apex double ridge through terminal spikelet formation reduced the number of spikelets per spike. Plants exposed to water stress starting 12 days after seedling emergence required the same duration to develop double ridges as the controls, but stressed plants had a shorter spikelet development stage, resulting in fewer spikelets per spike. The data suggested that the transition of the apex from vegetative to reproductive growth is a continuum. Regression analysis of spikelets per spike at the apex terminal spikelet stage on maximum daily air temperature during the spikelet formation period showed a significant negative linear relationship (R2 = −0.69). This relationship, along with application of growing‐degree days for estimating the spikelet development period, has application for enhancing prediction of grain yields from number of spikelets produced per spike.
Response of Cicer Milkvetch Seed to Osmoconditioning1
Authors: Abernethy R. H.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.), a forage legume for which no cases of bloating have been reported, has received limited utilization partly due to failures of stand establishment. The objectives of this study were to evaluate the laboratory germination, field emergence, and deteriorated seed response of cicer milkvetch seedlots to osmoconditioning (OC) regimes to determine if this technique would enhance germination response and stand establishment. Seedlots responded variably to OC treatment. Significant interactions between seedlot and polyethyleneglycol (PEG) level, post‐OC drying time, and duration of OC treatment were obtained for germination percent and mean germination time. An OC regime of 8 to 10 days duration in 250 g of PEG kg water−1 provided a significant reduction in mean germination time (MGT) for the two seedlots of ‘Monarch’ and two of the three seedlots of ‘Lutana’ evaluated (from 8 to 5 days over all seedlots), with little effect on laboratory germination. Concentrations of 150 and 200 g of PEG kg water−1 tended to reduce germination percent. Naturally deteriorated seed of four of the five seedlots responded positively to OC. Field emergence enhancement was variable, with a significant increase in seedling emergence for one of two experiments. The potential for improving field establishment of cicer milkvetch by OC would appear to be limited from the results of this study.
Performance and Photosensitization of Cattle Related to Forage Quality of Four Legumes1
Authors: Marten G. C. , Ehle F. R. , Ristau E. A.
Published: July 2010

Alfalfa (Medicago sativa L.) is a superior forage legume that has several shortcomings as a pasture species, including ruminant bloat potential. Our objective was to determine whether palatability differences among alfalfa and three nonbloat‐inducing alternative legume species would influence performance of grazing heifers (Bos taurus). Heifer performance was quantified on pure stands of the four legumes from 1982 through 1984 and of three legumes in 1985. Grazing pressure was controlled in pastures that had a Waukegan silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludolls) soil. Heifers confined to cicer milkvetch (Astragalus cicer L.), by far the least palatable species, usually gained less than those confined to either alfalfa, birdsfoot trefoil (Lotus corniculatus L.), or sainfoin (Onobrychis viciifolia Scop.). Mean average daily gains during 1983 and 1984 (long‐term grazing seasons) were 0.67, 0.81, 0.80, and 0.42 kg for alfalfa, birdsfoot trefoil, sainfoin, and cicer milkvetch, respectively. Measurements of nutritive value did not explain gain differences, but reduced intake and frequent photosensitization occurred in heifers that grazed cicer milkvetch. Heifer product per hectare was influenced more by daily gains than by legume carrying capacity. Birdsfoot trefoil is a promising alternative pasture legume because it provided excellent heifer gains and had better summer growth and persistence than sainfoin, although somewhat less persistence than alfalfa. The poor palatability of cicer milkvetch was associated with reduced intake, reduced gains by cattle, and possibly with the photosensitization problem; however, its excellent yield, persistence, and nutritive value indicate that cicer milkvetch deserves more research and breeding to overcome its antiquality traits.
Deriving a Large‐Seeded Switchgrass Population using Air‐Column Separation of Parent Seed1
Authors: Boe A. , Johnson P. O.
Published: July 2010

Selection for seed size is important in native, warm‐season grass improvement programs because of the positive correlation between seed size and seedling vigor. Bulk seed from a switchgrass (Panicum virgatum L.) population of 750 spaced plants from a field nursery was separated into four weight classes (174.1, 190.5, 209.5, and 225.8 mg/100 seeds) utilizing a South Dakota Seed Blower. A highly significant (P < 0.01) linear relationship was detected between mean 100‐seed weights of weight classes and mean seed weights of open‐pollinated, spaced‐planted progeny produced from these classes. Highly significant differences in mean seed weight also existed among plants within weight classes. In switchgrass, high seed weight was an effective selection criterion for increasing the seed weight of progeny from a bulk seed lot.
Selection and Heritability of Tolerance to Sodium Chloride in Four Forage Species1
Authors: Ashraf M. , McNeilly T. , Bradshaw A. D.
Published: July 2010

Breeding for salt tolerance in crop species, if possible, is an economical approach to overcoming the problem of soil salinity. However, the availability of appropriate genetic variation at the intraspecific and/or interspecific level is a prerequisite for successful progress under selection. Genetic variation for NaCl tolerance at the seedling stage was assessed in nutrient solution culture in forage rape (Brassica napus L.), berseem clover (Trifolium alexandrinum L.), alfalfa (Medicago sativa L.), and red clover (Trifolium pratense L.). Shoot growth of all species was severely inhibited after 2 weeks of growth in 200, 225, and 250 mmol L−1 NaCl, but there was considerable variability between seedlings. Ten‐thousand seeds of each species were therefore screened for shoot growth at high NaCl concentrations. Selection intensities of < 1% were achieved for all species. Selected plants in two polycrossed populations of each species allowed estimation of realized heritability and narrow‐sense heritability. Realized heritabilities were 0.62, 0.34, 0.31, and 0.57 for forage rape, berseem clover, alfalfa, and red clover, while narrowsense heritabilities from parent‐progeny regression, were 0.74, 0.50, 0.52, and 0.98 for those species, respectively. It was concluded that significant responses to recurrent selection for seedling NaCl tolerance may be expected in these species.
Geographical Diversity for Quantitative Spike Characters in a World Collection of Durum Wheat1
Authors: Zeuli P. L. Spagnoletti , Qualset C. O.
Published: July 2010

Crop germplasm collections are formidable to plant breeders and others who wish to draw samples by virtue of their large number of entries and muliplicity of potentially interesting characters. We have examined discriminant and clustering methods for their utility in revealing germplasm groupings that are useful for selection of parental stocks and for revealing evolutionary patterns. More than 3000 entries of durum wheat (Triticum turgidum L., durum group) representing 26 countries of origin were obtained from the U.S. National Small Grains Collection and grown in a common environment in northern California. Eight quantitative measurements on spike characters were made, including awn and spike length, awn/spike length ratio, spikelet number, rachis internode length, number and weight of kernels per spike, and mean single kernel weight. Five clusters were delineated among the 26 country origins: (i) 11 countries in Europe and North Africa; (ii) France, USSR, and USA; (iii) nine countries in the eastern Mediterranean area; (iv) Ethiopia and India; (v) Afghanistan. An east to west clinal pattern was detected that represents a gradient in unimproved to improved types. Some countries with contrasting agroecological conditions clustered together, probably because a high percentage of breeding lines and cultivars shared parents from among the clustered countries. These results revealed wide variation in numbers of entries from among countries. Certain areas should be sampled morextensively. Documentation data are less complete than desired to establish evolutionary and ecological relationships. The methods used here helped focus upon groups of materials for use in plant breeding and research.
Effect of Raceme‐Localized Supplemental Light on Soybean Reproductive Abscission1
Authors: Myers Robert L. , Brun William A. , Brenner Mark L.
Published: July 2010

The percentage of soybean [Glycine max (L.) Merr.] reproductive structures that abscise is a potentially important yield factor. To better understand the involvement of light in the abscission of reproductive structures, a series of in vitro raceme‐culture and growthchamber experiments were conducted. In the in vitro raceme‐culture experiments, racemes with four to six flowers at or past anthesis were excised from the soybean plant (genotype 1X93‐100), embedded in a complete nutrient, solid agar medium, and subjected to various light treatments. A series of three experiments indicated that the racemes contain a photoreceptor, possibly phytochrome, capable of regulating sucrose accumulation. In each of the growth chamber studies, supplemental light was supplied directly to individual soybean flowers via fiber optic light guides. The light source (a tungsten filament bulb) increased the photon flux to the flowers by 10‐fold. The first growth chamber experiment showed that flowers receiving supplemental light were more intense sinks for 14C‐sucrose than were controls (intensity value of 1.0 vs. 0.4 ✕ 10−7, intensity = [dps of flower/dps of raceme]/[kg dry wt of flower]). In a second study, 42% of flowers treated with supplemental light set pods, while only 26% of control flowers set pods. A third experiment showed that red supplemental light produced 55% fruit set, compared to 41% set for far‐red light, and 35% for controls (far‐red not statistically different than control, but all other comparisons are significantly different). These experiments indicate that both photoassimilate accumulation and abscission in young soybean reproductive structures may be regulated by light quality.
Survival of Sesame Seeds at the Temperature (−196°C) of Liquid Nitrogen1
Authors: Stanwood Phillip C.
Published: July 2010

Preserving valuable seed germplasm in liquid nitrogen (LN2) has the potential of extending the storage life of the sample almost indefinitely. However, during the cooling and rewarming process, temperature related stresses occur that can be lethal to many biological materials, including seeds. The capacity of seeds to withstand LN2 cooling is critical to long‐term cryopreservation of these germplasm samples. Seeds from six sesame (Sesamum indicum L.) selections were used to develop procedures to overcome cryogenic damage during the LN2 cooling/rewarming process. Seed moisture content and cooling rate were identified as controlling factors in the survival of sesame seeds exposed to LN2. As seed moisture content increased from 60 to 120 g kg−1 and cooling rate increased from 10 to 200°C min−1, mortality increased. Regardless of cooling rate, all seeds of all selections were killed at moisture content levels above 120 g kg−1. At seed moisture contents below 60 g kg−1 and cooling rates of 1, 10, and 30°C min−1, all seeds of all sesame selections tested survived. At a 200°C min−2 cooling rate and moisture contents below 60 g kg−1, four of the six selections were damaged. Results from this study suggest that sesame seeds can tolerate LN2 exposure if the seed moisture content is below 60 g kg−1 and the cooling rate is between 1 and 30°C min−1.
Rate and Duration of Grain Fill in Spring Wheat1
Authors: Bruckner P. L. , Frohberg R. C.
Published: July 2010

The grain fill (GF) period of spring wheat (Triticum aestivum L.) grown in the Northern Great Plains coincides with periods of drought and high temperature stress, whicho ften reduce crop yield and quality. Rate and duration of GF were determined for 20 spring wheat genotypes in four rainfed North Dakota environments to evaluate genotypic variation for rate and duration of GF, and to examine relationships between estimated GF parameters, environmental limitations, wheat productivity, and stress tolerance in environments prone to postanthesis drought and high temperature stresses. A quadratic polynomial was used to describe the relationship between kernel weight and accumulated growing‐degree days from anthesis to maturity. Rate and duration of GF were estimated from fitted curves. Genotypes varied for both GF rate and duration, but increasing temperatures during GF tended to stop grain growth prematurely and to hasten physiological maturity. Rate, but not duration of GF, was correlated with kernel weight. Increasing kernel weight by extension of the GF period does not appear to be a promising strategy for increasing grain yield in these environments. Rate and duration of GF were not associated in these genotypes. Results suggest that simultaneous selection for high GF rate and high kernel weight is possible without lengthening GF duration, and that selection for high GF rate through selection for high kernel weight is possible. High rate and short duration of GF appeared to contribute to increased stress tolerance in these genotypes, but only one of the 20 genotypes investigated had both characteristics. High GF rates with short to medium GF durations appear to be desirable objectives in environments in which the growing season frequently is shortened because of severe stress.
Response to Plant Densities and Nitrogen Levels for Four Maize Cultivars from Different Eras of Breeding1
Authors: Carlone M. R. , Russell W. A.
Published: July 2010

We evaluated the performance of maize (Zea mays L.) cultivars representing 10‐yr eras in 12 treatment combinations of plant densities and N levels. There were four open‐pollinated (OP) varieties and six 10‐yr (1930 to 1980) eras, four cultivars per era, of singlecross hybrids. A primary purpose was to compare the hybrids and eras for interaction with plant densities and N levels. The cultivars were grown for 2 yr near Ames, IA at densities of 34 445, 51 661, and 68 889 plants ha−1 and N levels of 0, 80, 160, and 240 kg N ha−1. Grain yields among densities averaged over N levels and cultivars were not different; yields among N levels averaged over densities and cultivars were highly significantly different (P < 0.01). The yield increase from 0 to 80 kg N ha−1 was 78.1%; from 80 to 160 kg N ha−1, 15.8%, but there was no further increase at 240 kg N ha−1. Cultivars ✕ densities and cultivars ✕ N‐levels interactions were highly significant. Cultivars from OP to 1960 eras had either nonsignificant (positive or negative), or significantly negative linear responses to plant densities. Conversely, all cultivars in the 1970 and 1980 eras had positive linear responses; for five of the eight, the responses were significant. All cultivars had highly significant, positive linear responses to N levels. There was no directional trend over successive eras of hybrids for relative values of linear responses to N levels. The second‐order interaction of densities ✕ N levels ✕ cultivars was significant for yield. Eighteen of 28 cultivars had significant linear ✕ linear components; consequently, densities and N levels were not independent factors, and a cultivar seemed to have a specific density ✕ N‐level combination for maximum grain yield. Ear length was the yield component that had highest correlations with yield, among treatments combinations.
Predicting Yield from Early Generation Estimates of Reproductive Growth periods in Soybean1
Authors: Smith James R. , Nelson Randall L.
Published: July 2010

Previous research has demonstrated positive relationship between reproductive growth periods and seed yield in soybean [Glycine max (L.) Merr.]. The purposed of this research was to evaluate predicted response in seed yield by selection for length of reproductive growth periods within early generation segregating populations. Two populations of 131 and 89 F2‐derived lines were developed from crosses between experimental lines selected for differences in seed‐filling period and were tested in the F3 and F4. Single‐rowpl ots wereg rown in a randomized complete blocked design with two replications at Urbana, IL in 1984 and 1985. The soil type each year was a Flanagan silt loam (Aquic Argindolis) Reproductive growth periods were estimated as the difference between specific reproductive growth stages (R1, R4, R5, R7, and R8). Heritabilities were estimated by the regression coefficient of F4 generation lines on F3 generation lines. Genotypic correlations were calculated from the same offspring‐parent relationship. Heritabilities and genotypic correlations was were used to predict gain from selection. Heritabilities for most of the reproductive growth periods were not higher than those for yield, and the genotypic correlations between yield and reproductive growth periods were generally small. The predicted gain in seed yield by selection for increases in reproductige growth periods, relative to selection for increases in seedy ield, was low in all cases. Early generation selection for reproductive growth periods was unreliable in identifying high yielding lines.
Development and Evaluation of Impermeable Seed Coats for Preserving Soybean Seed Quality1
Authors: Hartwig E. E. , Potts H. C.
Published: July 2010

Advanced generation soybean [Glycine max (L.) Merr.J breeding lines have been developed that have impermeable seed coats. The donor parent for impermeable seed coats was the wild soybean [Glycine soja Sieb. and Zucc.]. A group of 11 impermeable seed coat lines along with the parent 'Forrest' were grown at five southeastern USA locations to further evaluate the effectiveness of the character for maintaining seed quality. Center rows of 4‐row plots were harvested at maturity, and a border row was harvested 4 to 6 weeks later. Seeds from the delayed harvest were exposed to prolonged warm, rainy weather. At Starkville, MS, rain fell on 18 days with a total of 220 mm during October. Total viable seeds from Forrest were 96% for the early harvest and 5% for the delayed harvest. for D81‐9776, one of the best impermeable seed coated lines, total viable seeds for early and late harvest were 95 and 86%, respectively. From another group of material, one line exhibited 100% viable seeds after 6 weeks exposure to warm, rainy weather, while ‘Epps’ had only 27% viable seeds.
Regression and Cluster Analysis of Environmental Responses of Hybrid and Pureline Winter Wheat Cultivars1
Authors: Carver Brett F. , Smith Edward L. , England Howard O.
Published: July 2010

The commercial development and release of F1 hybrid wheat (Triticum aestivum L.) cultivars should enable wheat producers to achieve higher levels of grain production. Despite increased interest in hybrid wheat, planting of hybrid cultivars at the presentime is limited to areas traditionally having high yield potential or receiving intensive management. This study was conducted to compare yield responses of hybrid and pureline cultivars across a wide range of environments. Regression and cluster analyses were applied to data obtained from four winter wheat performance trials from 1982 to 1985. A different set of either 30 or 40 genotypes, approximately half of which were hybrids, was evaluated each year in Oklahoma. Because the environmental responses of all genotypes were highly correlated in each year, environment means were employed as the index in the regression analysis. In 1982, the average regression coefficient (b) for hybrids (1.12) was significantly greater than that for either semidwarf purelines (0.99) or tall pnrelines (0.79), indicatingreater responsiveness of hybrids to improving production conditions. For the remaining years (1983–1985), similar linear responses of hybrids and semidwarf pnrelines indicated that the hybrid yield advantage did not increase in environments with higher index values. In addition, classification of genotypes into homogeneous‐response clusters according to actual responses indicated high similarity between environmental responses of hybrids and semidwarf pnrelines. Responses of hybrids and tall purelines, however, were dissimilar. The similar environmental response patterns of the most recently developed hybrid and semidwarf pureline winter wheat cultivars does not support the recommendation of either cultivar type when considering overall production potential of the environment.
Artifacts in the Analysis of Plant Tissues for Soluble Carbohydrates1
Authors: Hendrix Donald L. , Peelen Kimberly K.
Published: July 2010

A study of the soluble sugars in cotton (Gossypium hirsutum L.) leaf tissue was undertaken to explain preliminary results which indicated little or no fructose (ca. 0.03 g m‐2) in this tissue. To further test the analytical methods employed, leaves of watermelon [Citrullus lanatus, (Thunb.) Matsum, & Nakai], sugar beet (Beta vulgaris L.), and sugarcane (Saccharum spp.) were also analyzed. Developing cotton seed coat tissue was also analyzed to test the suitability of these methods on extracts from tissues that are high in interfering substances (i.e., phenolics). Results using standard enzymatic methods to determine the carbohydrate content of aqueous ethanol extracts of these tissues were compared to those obtained by HPLC of the same extracts. Careful analysis showed that fructose was a minor soluble carbohydrate component in cotton leaf, contrary to numerous citations in the literature. An active soluble invertase in cotton leaf tissue degraded 28% of the sucrose within 15 minutes of thawing. Sucrose was degraded in the leaves of other species following freezing and thawing, but to a lesser extent than in cotton leaf. The enzymatic method worked well for the analysis of carbohydrates extracted from leaves but was susceptible to interference when used to analyze carbohydrates from cotton seed coats; however, the addition of powdered charcoal to seed coat extracts prior to analysis was found to alleviate such interference.
Cell‐Wall Composition and Digestibility of Alfalfa Stems and Leaves1
Authors: Albrecht K. A. , Wedin W. F. , Buxton D. R.
Published: July 2010

The cell walls of alfalfa (Medicago sativa L.) are a major source of energy for both dairy and beef cattle. Despite this, little is known about composition of the cell walls. Our objective was to characterize changes in the proportion of, and cell‐wall carbohydrate and lignin composition in, stems and leaves of maturing alfalfa. Field‐grown ‘Tempo’ and ‘Spredor 2’ alfalfa (upright and semiprostrate cultivars, respectively) were sampled at weekly intervals seven times in 1981 and eight times in 1982. Sampling both years commenced approximately 1 week before early‐bud stage and was terminated when seed pods formed. Plants were divided into stem and leaf fractions before cell‐wall and in vitro digestible dry matter (IVDDM) analyses were conducted. Concentrations of IVDDM in leaves were approximately 800 g kg‐1 and changed little with maturity. Stem IVDDM declined from approximately 750 g kg‐1 before bud development to 480 g kg‐1 in 1981 and 520 g kg‐1 in 1982. The concentration of cell‐wall material (CWM) increased by nearly 60% in stems in both seasons, whereas leaf CWM increased by only 10%. The proportion of lignin in the stem CWM increased by 30% with a corresponding decrease in the neutral‐sugar fraction as the plants matured. Xylose and glucose (low digestibility) increased with maturity as a proportion of total cell wall neutral sugars while arabinose and galactose (high digestibility) decreased. Soil‐moisture deficits in 1981 seemed to increase the amount of stem cell‐wall arabinose and xylose and decrease glucose concentrations compared with 1982. This work confirms that digestibility of alfalfa decreases with maturity as a result of increased concentration of CWM in stems, decreased stem digestibility, and increased proportions of stems. Significant compositional changes in CWM in stems and little change in leaves occurred as plants matured.
Relationships between the Lengths of the Vegetative and Grain Filling Periods and Agronomic Characters in Three Durum Wheat Crosses1
Authors: Knott D. R. , Gebeyehou G.
Published: July 2010

Random sets of lines from three durum wheat (Triticum turgidum L.) crosses were developed by single seed descent to study the relationship between yield and the lengths of the vegetative and grain filling periods. The parents of the three crosses, ‘Pelissier’/‘Hercules’, ‘Stewart 63’/‘Anhinga’, and ‘Wakooma’/‘Anhinga’, were selected to represent different combinations of the lengths of the vegetative and filling periods. The random lines were tested in rainfed field experiments in 1982 and irrigated experiments in 1983, and eight characteristics were measured—lengths of the vegetative and filling periods, days to maturity, height, straw strength, yield, weight per 1000 kernels, and protein content. The lengths of the vegetative and filling periods were negatively correlated in both years. Correlations between yield and the lengths of the two growth periods were inconsistent and generally fairly small. The data provided no indication that there was an optimum combination of the lengths of the vegetative and filling periods that gave maximum yield. Yield and protein content showed a significant negative correlation in only two of six tests.
Transfer of High Seed Protein to High‐Yielding Soybean Cultivars1
Authors: Wehrmann V. K. , Fehr W. R. , Cianzio S. R. , Cavins J. F.
Published: July 2010

An effective breeding strategy is needed for the development of high‐protein, high‐yielding soybean [Glycine max (L.) Merr.] cultivars. This study was conducted to evaluate a backcross strategy for transferring genes for high seed protein from a low‐yielding plant introduction to high‐yielding lines with a average protein content. Pando, a plant introduction with low yield and about 480 g kg−1 of seed protein was crossed to three high‐yielding lines with an average protein content about 400 g kg−1. Selection for high protein was practiced between two generations of backcrossing to the high‐yielding parent. After two backcrosses, 95 random BC2F2‐derived lines from each population were evaluated for seed yield, protein, and oil content in Iowa. None of the BC2F2‐derived lines equaled the protein content of Pando, but an average of 72% of the lines from the three populations had significantly higher protein than the recurrent parent. On average, about 19% of the BC2F2‐derived lines with a protein content significantly different (α = 0.05) from the recurrent parent in seed yield. The results indicated that when a low‐yielding, high‐protein donor parent is utilized. selection for high protein between two backcross generations would effectively increase the seed protein in the backcross progeny above that of the high‐yielding recurrent parent and still result in some progeny having a seed yield not significantly different from that parent.
Seed Age and Salt Tolerance at Germination in Alfalfa1
Authors: Smith S. E. , Dobrenz A. K.
Published: July 2010

There is widespread interest in evaluating the salt tolerance of crop germplasm, especially at the germination stage. Unfortunately, the effects of variation in seed quality on germination behavior under saline conditions are not well understood. In this study, we investigated the effects of natural and artificial aging on germination salt tolerance in alfalfa (Medicago sativa L.) under laboratory conditions. The salt tolerance at germination of different aged seed lots from the same germplasm source was shown to differ significantly when expressed as a proportion of the nonsaline germination of each lot. Solute leakage from seeds during imbibition (a proposed measure of germination performance) increased as seed age increased. Increases in solute leakage of unstressed seed were correlated with declines in germination salt tolerance for aged but not fresh seed. Our research demonstrates the limitations inherent in comparing the germination salt tolerance of lots of alfalfa seed that differ in age and of using artificial aging and solute leakage tests to predict germination performance under stress.
Relationship of Ethylene Production to Elongation in Deepwater Rice1
Authors: Khan Anwar A. , Thakur R. , Akbar M. , HilleRisLambers D. , Seshu D. V.
Published: July 2010

There is a need to unravel mechanisms controlling elongation and submergence tolerance in rice (Oryza sativa L.) and to develop technology for improving rice for deepwater regions. Because of the reported involvement of ethylene in stem internode elongation of deepwater rice, we examined the relationship of seedling elongation to ethylene production. Fourteen rice cultivars/breeding lines with widely ranging differences in elongating capacity in deepwater were used in these studies. Ethylene production by intact 20 to 27‐day‐old seedlings was determined by submergence in 122 ✕ 6‐cm glass cylinders and related to leaf blade/sheath elongation. The floating rice, ‘TCA 177’, elongated largely by the leaf sheath supporting the youngest leaf. The elongating capacity of the rice seedling resided in the top two leaf blades and their sheaths. Elongation decreased with the duration of submergence and after 72 h little increase occurred. A 24‐h submergence enhanced the capacity of the seedlings to produce ethylene and the production was highest during the first hour after removal from water. Complete submergence caused greater production of ethylene than partial submergence. The capacity for ethylene production and elongation peaked at 24 to 36 h of complete submergence and then declined. Ethylene production following submergence generally followed the order: floating rice > deepwater rice > elongating modern cultivar > nonelongating modern cultivar. Elongation index correlated well (r = 0.88**, significant at the 0.01 probability level) with ethylene producing capacity of seedlings in a population of 14 rice cultivars/breeding lines. The results show that ethylene production by young rice seedlings, following complete submergence, is a good measure of their elongating ability.
Root System Genotype and Nitrogen Fertility Effects on Physiological Differences between Burley and Flue‐Cured Tobacco. II. Whole Plant1
Authors: Crafts‐Brandner S. J. , Sutton T. G. , Sims J. L.
Published: July 2010

Flue‐cured tobacco (Nicotiana tabacum L.) cultivars produce similar leaf yields compared to hurley tobacco cultivars despite requiring approximately four times less N fertilizer. This study is the second part of an experiment to characterize physiological differences between representative burley and flue‐cured cultivars and to determine the influence of the root system on shoot physiology. Control and reciprocally grafted plants of burley ‘Ky 14’ and flue‐cured ‘Speight G28’ (G28) were grown in soil pots [Maury silt loam (Typic Paleudalfs)] at two levels of N fertilization (580 or 230 mg N week"1)‐ Plants were sampled and divided into laminae, midveins, stalk, and roots from 10 days before to 30 days after topping. Dry weight distribution for the cultivars was similar for all plant parts except laminae. G28 accumulated significantly more lamina dry weight than Ky 14, although leaf area and leaf number were similar for both genotypes. Cultivar differences in lamina dry weight occurred even though lamina and stalk N contents were similar, within an N level. Thus, G28 produced more lamina dry weight based on either units of N fertilizer added or lamina N accumulated. Laminae dry weight differences were explained in large part by higher starch concentration for G28 than Ky 14. Laminae free sugar concentration was low and similar for all treatments. These data inferred that starch metabolism or storage capability was dissimilar for the two tobacco types. The genotype of the root system did not influence any parameter measured for shoots and, thus, differences between cultivars may be expressed at the level of the leaf lamina cell.
Ethylene as an Indicator of Salt Tolerance in Rice1
Authors: Khan Anwar A. , Akbar M. , Seshu D. V.
Published: July 2010

Salt accumulation in cultivated and cultivable rice (Oryza sativa L.) and other croplands poses a serious threat to irrigated agriculture. Development of cultivars with high tolerance to salinity, and methodology to monitor and rapidly screen for salt tolerance may ameliorate the problem to a considerable extent. Because of the involvement of ethylene in growth responses under stress, its potential as an indicator of salt tolerance in rice in laboratory tests was investigated. Little ethylene was detected in rice seeds in the presence or absence of 0.1 M NaCl with up to 6 days of soaking. When 1‐aminocyclopropane‐1‐carboxylic acid (ACC) was used alone or in combination with salt, ethylene production began on the third day of soaking, reached a maximum by 4 to 5 days, and then declined. A parallel increase in ethylene production and shoot growth occurred in the presence or absence of salt with an increase in ACC concentration, reaching a maximum at 1 to 2 mM; at 5 to 50 mM both processes were inhibited. The ACC‐derived ethylene production and shoot growth were inhibited to varying extent in the rice genotypes by the addition of 0.1 M NaCl. At the saturating dose of ACC (2 mM), ethylene production and shoot growth appeared to depend on the activity of the ethylene forming enzyme (EFE) since Co2+, and not aminoethoxyvinylglycine (AVG), inhibited both processes. The capacity of rice to produce ACC‐dependent ethylene was a cultivar trait and correlated well (r = 0.91) with salt tolerance at the seedling stage. The data indicate that ethylene may serve as a biochemical marker for mass screening of large breeding populations of rice for salinity tolerance at the seedling establishment phase.
Effects of Four Growth Regulators on Photosynthate Partitioning in ‘Majestic’ Kentucky Bluegrass1
Authors: Hanson K. V. , Branham B. E.
Published: July 2010

Experiments were conducted in the greenhouse and growth chamber to determine the effect of plant growth retardants on photosynthate partitioning patterns in vegetative ‘Majestic’ Kentucky bluegrass (Poa pratensis L.). Single mature plants were treated with one of the following plant growth regulators (PGRs): Limit® (N‐ [(acetylamino)methyl]‐2‐chloro‐N‐(2,6‐diethylphenyl)acetamide) at 2.84 kg ha−1, Cutless® (αa(1‐methylethyl)‐α‐[4‐(triflouromethoxy)phenyl]‐5‐pyrimidin meethanol) at 2.24 kg ha−1, paclobutrazol [(2RS,3RS)‐l‐(4‐chiorophenyl)‐4,4‐dimethyl‐2‐(1,2,4‐triazol‐1‐yl)pentan‐3‐oil at 2.24 kg ha−1, and mefluidide (N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide) at 0.28 kg−1. Partitioning patterns were examined 1, 2, and 4 weeks after PGR application by exposing individual leaves to 14CO2 and quantifying translocated 14C in immature leaves, mature leaves, crowns, axillary shoots (tillers plus rhizomes), and roots. In the greenhouse study, Limit tended to cause an increase in photosynthate accumulation in the crown with 63% of the applied label found in the crown at 4 weeks after application compared to 17% for the control plants. Mefluidide caused similar behavior with 39% of the label in the crown at week 4. In both studies, paclobutrazol caused a significant decline in photosynthate partitioning to the roots at week 4 with 20% vs. 49% for the control in the greenhouse study and 9% vs. 27% for the control in the growth chamber study. Cutless exhibited a similar response with 10% accumulation in the roots vs. 27% for the control at week 4. Mefluidide significantly increased translocation to the roots when compared to the control plant in the growth chamber study at weeks 2 and 4 (39% vs. 21% and 51% vs. 27%, respectively). Results of this study indicate that while all four growth regulators suppress top growth, each alters partitioning patterns differently among above and below ground organs, an important factor in understanding turf response to PGR application in the field.
Diversity of United States Hybrid Maize Germplasm; Isozymic and Chromatographic Evidence
Authors: Smith J. S. C.
Published: July 2010

One‐hundred and thirty‐eight hybrids currently used in U.S. maize (Zea mays L.) production were genotyped for 21 isozymic loci. Sixtysix of these hybrids could be classified into 10 groups on the basis of their isozymic similarities and were additionally analyzed for their zein constitution by reversed‐phase high‐performance liquid chromatography. Objectives were to: (i) obtain isozymic genotypes widely used maize hybrids; (ii) to reveal any trends toward eithernarrowing or a broadening of the genetic base; and (iii) to reveal associations among hybrids on the basis of isozymic and chromatographic data. Compared to an earlier survey, isozymic data revealed no trend toward either an increased or decreased level of diversity over all hybrids during the prior 5‐yr period. Fifty‐six percent of proprietary brand hybrids and 88% of foundation seed company hybrids examined were judged to represent different genetic entities when both isozymic and chromatographic data were considered. Over all hybrids examined, 42% were unique and were released by private companies; 25% were unique and were released by foundation seed companies. Nonunique hybrids fell into seven groups with similar or identical isozymic and chromatographic profiles. From biochemical data, U.S. maize cultivation and breeding appear to remain heavily dependent upon usage of B73, A632, Oh43, and Mo17 or closely related derivatives thereof. ‘Iowa Stiff Stalk Synthetic’ lines crossed to ‘Lancaster Sure Crop’ derived lines still appear to be the predominant heterotic pattern.
Hormonal Regulation of Elongation in Floating Rice During Submergence
Authors: Khan Anwar A. , Thakur R. , Akbar M. , HilleRisLambers D. , Seshu D. V.
Published: July 2010

Enhanced ethylene‐producing capacity of young seedlings of floating and deepwater rice (Oryza sativa L.) during submergence has been related to increased seedling elongation via leaf sheath/leaf blade. In this study we present evidence for modulation of elongation by hormones. Floating rice cuitivars ‘TCA 4’, ‘TCA 177’, and ‘TCA 212’ were used. Effects of various hormones and chemicals on elongation and ethylene‐producing capacity were determined during complete submergence of seedlings in 122‐ ✕ 6‐cm glass cylinders. Enhancement in ethylene‐producing capacity by submergence was completely suppressed by 0.05 mM aminoethoxyvinylglycine (AVG), indicating that the enhancement depended on the synthesis of 1‐ aminocyclopropane‐l‐carboxylic acid (ACC). Submergence‐induced elongation was partially inhibited by 0.05 mM AVG in 24 h and reversed to some extent by 0.1 mM ACC or 0.05 mM ethephon (2‐chlorethane phosphonic acid). Increase in ethylene‐producing capacity during submergence was also inhibited by 1 mM Co2+, which had no effect on seedling elongation. Gibberellin (GA) biosynthesis inhibitor, tetcyclacis [5‐(4‐chlorophenyl)‐3,4,5,9,10‐pentaazatetracyclo‐5,4,102.6, 08.11 dodeca‐3, 9‐diene] (TCY), strongly inhibited the increase in seedling elongation of TCA 177 without affecting ethylene‐ producing capacity. The effect of TCY on elongation was reversed by 0.1 mM GA4+7 (gibberellin A4 + A7). Abscisic acid (ABA) inhibited the ethylene‐producing capacity and the effect was reversed by kinetin. Application of GA4+7 plus kinetin caused a 60% reversal of ABA inhibited elongation. Nonsubmerged floating (TCA 177) and deepwater (‘BR 118‐3B‐17’) rice elongated to a greater extent than the nonelongating types when sprayed with 0.1 mM GA4+7. Thus, GA may influence elongation more directly than other hormones.
Outcrossing Rates of Six Common Bean Lines
Authors: Wells W. C. , Isom W. H. , Waines J. G.
Published: July 2010

The outcrossing rate of a species is an important parameter to consider when making a decision on the method to improve the species. Outcrossing rates were estimated for six white‐seeded common bean (Phaseolus vulgaris L.) lines sown in May and July 1985, at Irvine, CA. Estimates were based upon the proportion of black‐seeded (dominant) progeny from white‐seeded parents. Genetic variation for outcrossing rates among the six lines studied was suggested by the large difference between the mean estimate for ‘FM 53’ (66.8%) and the combined mean estimate for the other five lines (19.3%). Outcrosses occurred less frequently at the early planting date (18.8%) than at the late‐planting date (47.0%). Further studies on the outcrossing in the common bean and its application to recurrent selection are warranted in light of the reported results.
Yield Potential of Tropical Hybrid Maize Derivatives
Authors: Holley R. N. , Goodman M. M.
Published: July 2010

In an effort to enhance the germplasm base of the U.S. maize (Zea mays L.) crop an adaptation program was initiated in 1975. A group of nine 100% tropical hybrids were crossed in all possible combinations, without reciprocals. Progeny from each cross were sib mated for six generations with selection for earliness, low plant and ear height, tassel and silk synchronization, lodging resistance, and prolificacy. Following sib mating, selection continued through two generations of setting. All generations were grown in Raleigh, NC. In 1983 34 selected inbred lines were crossed onto two Corn Belt single cross testers, (A632Ht ✕ B73) and (Mo17 ✕ H95 ✕ H993). The number of entries representing each cross varied greatly depending upon response to selection. The testcrosses were divided into two groups by tester and combined with eight commercial check hybrids to form two tests. The tests were grown at three locations in 1984 and 1985, with three replications at each location. Testcrosses developed from 100% tropical inbred lines crossed with elite U.S. materials were agronomically competitive with commercial U.S. hybrids. The inbreds are adapted to the southern USA and flower about 1 wk later than B73. Plant height and grain moisture of the testcrosses were all within the range of the commercial checks. About 25% of the testcrosses had yields comparable to the commercial checks. The inbreds are relatively insensitive to photoperiod as a result of the apparent presence of complementary genetic systems for photoperiod sensitivity among the different tropical materials.
Inheritance of Glandular Trichomes in Tobacco
Authors: Johnson J. C. , Nielsen M. T. , Collins G. B.
Published: July 2010

Trichome type and density may be responsible for genotypic differences for insect resistance and leaf chemical constituents in tobacco (Nicotiana tabacum L.). We investigated the inheritance of glandular trichomes to determine the feasibility of selecting this trait in a breeding program. Segregating generations were derived from crosses among several tobacco introductions (T.I.) and ‘Ky 14’, a burley tobacco cultivar, which differ in densities of glandular trichomes. Microscopic examinations of the abaxial surface of 20 cm long leaves were made in the field in 1982 and 1984. The F1, F2, and F3 generation means for glandular trichome density were much lower than midparent values. Additive genetic effects for trichome density were highly significant, as were the estimates of the additive ✕ additive epistatic effects. Dominance effects were significant only in the cross T.I. 1112 ✕ T.I. 1068. Heritability estimates, obtained by regression of F3 family means on F2 parental values, were 0.74, 0.77, and 0.95 for the populations derived from crosses between T.I. 1112 and T.I. 1068, T.I. 1406, and Ky 14, respectively. Chi‐square analyses of F2 data for the presence or absence of glandular trichomes indicated Ky 14 and T.I. 1406 had alleles at two loci that were different from those present in T.I. 1112, and T.I. 1068 differed from T.I. 1112 at three loci. Genes at these loci may affect glandular trichome density as well as presence or absence of glandular trichomes, but other genetic factors, including those influencing leaf size and shape, may affect trichome density.
Establishment of Red Fescue Seed Crops with Cereal Companion Crops. I. Morphological Responses
Authors: Chastain T. G. , Grabe D. F.
Published: July 2010

A number of perennial grass seed crops, including red fescue (Festuca rubra L.), do not produce a seed crop during the establishment year. Planting red fescue with cereal companion crops would enable the grower to obtain an income from the grain crop during the establishment year. The objectives of this study were to determine the feasibility of establishing red fescue seed crops with cereal companion crops in Oregon's Willamette Valley and to examine the influence of cereal companion crops, cultivars, and row spacings on growth environment and plant development of red fescue. ‘Pennlawn’ red fescue was charcoal‐seeded in 30‐cm rows in October 1982 and 1983 on a Woodburn silt loam (fine‐silty, mixed, mesic Aquultic Argixeroll) soil near Corvallis, OR. ‘Yamhill’ and ‘Hill 81’ winter wheat (Triticum aestivum L.), and ‘Hesk’ and ‘Scio’ winter barley (Hordeum vulgare L.) were drilled in 15‐, 30‐, 45‐ and 60‐cm rows perpendicular to the red fescue rows. The effect of wheat and barley on photosynthetic photon flux density (PPFD), soil moisture available to red fescue plants, and red fescue growth characteristics were monitored until cereals were harvested. Companion crops reduced PPFD incident on red fescue plants by as much as 90% at peak cereal leaf area. This greatly decreased red fescue tiller numbers, dry matter production, and increased tiller height. The two cereals did not differentially affect red fescue growth. Increasing row spacing resulted in more red fescue tillers, dry matter, and reduced etiolation of tillers. Soil moisture content was not decreased by establishment with cereals. Competition by companion crops for PPFD was more important than for soil moisture in reducing red fescue growth during the establishment year. The effect of companion crops on red fescue seed yield and the economic returns from this cropping system are reported in a companion paper.