bluuebunny/crossref_metadata_2025 huggingface dataset:
Grazing Induces a Patterned Selection Response in Tall Fescue
Authors: Vaylay Ravi , van Santen Edzard
Published: July 2010

Pastures with perennial grass species are continuous in stands and are subjected to continual and often intensive natural selective forces. The objective of this study was to investigate the characteristics of tall fescue (Festuca arundinacea Schreb.) cultivars in response to natural selective forces. Ungrazed survivors from four cultivars—endophyte free (EF) GA‐5, endophyte infected (El) GA‐5, Johnstone, and KY‐31—were collected randomly from four paddocks. These paddocks were then grazed at 2.50, 3.75, 5.00, and 6.25 animals ha−1 for 2 yr and grazed survivors collected in similar fashion. These two groups were compared for four whole‐plant, four tiller, and three flag leaf traits in a 2‐yr study along with plants grown directly from the original seed lots. Each cultivar × age group × paddock combination consisted of 42 spaced plants. Each replicate of the original experiment was represented by seven plants selected at random from among the 10 originally collected from each replicate × paddock × entry combination. A polynomial response in grazed survivors was fitted with coefficients of determination ranging from 0.36 (maturity) to 0.79 (tiller number and dry matter yield). Comparison of GA‐5 EF and GA‐5 E1 revealed the influence of endophyte removal on host plants, which was more pronounced after grazing of the paddocks. Endophyte‐infected grazed survivors were late maturing with longer and increased number of tillers and higher dry matter yields. The implications of this research for forage breeding are that (i) the seeded cultivar evaluated under grazing may be different from the original seed lot, and (ii) cultivars are dynamic entities that change over time.
Selection Response with Marker‐Based Assortative Mating
Authors: Bernardo Rex
Published: July 2010

Assortative mating can increase additive variance (VA) and, consequently, selection response. Marker‐based assortative mating (MAM— the mating of individuals that have similar marker genotypes—has not been studied. My objectives in this simulation study were to (i) compare the selection response associated with MAM, phenotypic assortative mating (PAM), and random mating (RM) of selected individuals and (ii) determine when MAM will be most useful breeding programs. I simulated 25 generations of selection among 200 individuals, followed by MAM, PAM, or RM, in a cross between two inbreds. A total of 100 codominant marker loci and 100 quantitative trait loci (QTL) were randomly distributed across 10 chromosomes, each 100 centimorgans (cM) long. The effects of QTL were additive and followed an exponential distribution. Cumulative selection response was determined for different initial levels of heritability (h2 = 0.20, 0.50, and 0.80) and different numbers of individuals selected (N = 4, 8,16, and 32) in each generation. Compared with RM, MAM resulted in slight increases of 3 to 8% in selection response during the first several generations, particularly when h2 = 0.20 and N = 32. The PAM procedure led to slight increases of 2 to 4% when h2 = 0.80 and N = 32. Any advantage of assortative mating over RM dissipated by Generation 8 for MAM and Generation 15 for PAM. The loss of QTL heterozygosity was much greater with MAM than with PAM or RM. For long‐term improvement, selected individuals should be intermated by RM. The MAM procedure will be most useful for short‐term improvement in a biparental cross, particularly when h2 and selection pressure are low.
Activity of ATP Sulfurylase in Reproductive Soybean
Authors: Sexton P. J. , Shibles Richard M.
Published: July 2010

A low concentration of the S‐containing amino acids, cysteine and methionine, often limits the nutritive value of soybean [Glycine max (L.) Merr.] seed protein. On a whole‐plant level, the localization and duration of cysteine and methionine synthesis during seed filling in soybean have not been reported previously. The objective of this study was to characterize the localization and duration of ATP sulfurylase activity in reproductive soybean. ATP sulfurylase is the first enzyme in the S‐reduction pathway. Samples of soybean (cv. Kenwood 94) root, leaf, stem, pod wall, and seed tissues on a whole‐plant basis were taken at beginning seed filling (approximately R5.5) from two field sites in Iowa in 1997. In addition, samples of leaf, pod, and seed tissue from the same nodal position (Node 11) were collected weekly from R5 to R8 (full maturity) at one of the sites. At R5.5 almost half of whole‐shoot ATP sulfurylase activity was located in seed tissue. Leaf tissue contributed approximately 30 to 40% of the shoot ATP sulfurylase activity, and stems and pod wall contributed approximately 10% each. The profile of specific activity (fresh weight basis) for leaf, pod, and seed tissue at node 11 over time showed that activity of leaf tissue steadily declined during seed tilfing, whereas that of seed tissue increased initially with seed expansion and remained high until physiological maturity. Thus, in terms of both specific activity, and sustained duration of activity, seed tissue was the dominant site of ATP sulfurylase activity during seed filling. It appears, then, that most of the S‐containing amino acids synthesized during reproductive growth may be synthesized in the seed itself, rather than being imported from other tissues.
Photosynthesis and Productivity of Cotton under Silverleaf Whitefly Stress
Authors: Lin Tong‐Bao , Schwartz Amnon , Saranga Yehoshua
Published: July 2010

The silverleaf whitefly (SLW), Bemisia argentifolii (Bellows and Perring), has been a severe pest of numerous field and vegetable crops for many years. Nevertheless, little has been reported on the complex interactions between SLW and its host plants. This study was aimed at investigating the effects of SLW on cotton (Gossypium hirsutum L.) photosynthesis and productivity under various irrigation and N fertilization regimes. Cotton plants (cv. Siv'on) were examined during an entire growing season in two factorial‐designed screenhouse experiments consisting of two irrigation regimes (I) × two N application rates × two SLW levels (noninfested vs. infested). Buildup of the SLW population was markedly higher on N‐fertilized plants than on N‐deficient plants. Seed cotton yield was reduced by SLW in festation under all combinations of I × N treatments by about 40%. Yield reduction (noninfested minus infested) was significantly correlated with the number of SLW adults on the maximally infested leaf at peak flowering (r2 = 0.94, P < 0.05 in 1995; r2 = 0.91, P < 0.05 in 1996). Photosynthetic rate decreased 50% at about 60 d after SLW introduction. The relative photosynthetic rate (infested/noninfested) was significantly correlated with SLW adult density on the maximally infested leaf (r2 = 0.72, P < 0.001 in 1995; r2 = 0.53, P < 0.01 in 1996). The reduced photosynthetic rate was associated with reductions in chlorophyll variable fluorescence (Fv/Fm) and fluorescence yield. No substantial changes were found in stomatal conductance, intercellular CO2 concentration, and leaf chlorophyll content. These findings indicate that SLW infestation impairs, either directly or indirectly, the photochemical reaction of the photosynthetic system in cotton plants.
Interaction of Nitrogen, Phosphorus, and Potassium on Evapotranspiration Rate and Growth of Kentucky Bluegrass
Authors: Ebdon J. S. , Petrovic A. M. , White R. A.
Published: July 2010

Research is limited concerning the interactive effects of nitrogen, phosphorus, and potassium on turfgrass evapotranspiration (ET) rate. Previous research has emphasized the influence of N on growth and ET. In this study, a central composite experimental design was used to investigate the interactive effects of N, P, and K on Kentucky bluegrass (Poa pratensis L. ‘Majestic’) water use and growth under field conditions. Five treatment levels for each nutrient were used; N treatment levels ranged from 49 to 588 kg ha−1 yr−1, P from 0 to 86 kg ha−1 yr−1, and K from 0 to 348 kg ha−1 yr−1. Clipping yield and ET (measured in 25‐cm diam. bucket‐type lysimeters) were recorded on a weekly basis. A field study conducted in 1988 evaluated N, P, and K applied alone while in a 1989 field study N, P, and K combinations and interactions were evaluated. Applied alone, P and K had no effect on ET or shoot growth independent of the rate applied. Unless a high level of N was applied (588 kg ha−1 yr−1), N had no affect on shoot growth or ET. Shoot growth (clipping yield) and ET were highly correlated (r = 0.79, P ≤ 0.001) in the single nutrient study. There was an interaction between N, P, and K on shoot growth and ET. Shoot growth response was highly correlated with ET response when fertilized in the normal range of P for the soil type evaluated (0, 21.5, 43 kg P ha−1 yr−1). Evapotranspiration rate response to N, P, and K applied in combination were distinctly different from nutrients applied alone. At medium to high levels of N and P (294 kg N and 43 kg P ha−1 yr−1 and higher), water use increased in response to increasing K applied. Conversely, at N and P levels routinely applied to this species and soil type (147 kg N and 21.5 kg P ha−1 yr−1 and lower), increasing K levels minimized water use. Further research is needed to study specific interactions.
Sprout Damage and Preharvest Sprout Resistance in Hard White Winter Wheat
Authors: Wu Jiming , Carver Brett F.
Published: July 2010

Increased production of hard white winter (HWW) wheat, Triticum aestivum L., in the Great Plains introduces the possibility of preharvest sprouting (PHS) that is often not expressed among widely grown hard red winter (HRW) cultivars. Field experiments were conducted to learn the severity of sprouting likely to occur in contemporary HWW wheat. Specific objectives were to (i) determine the level of sprout damage in Great Plains environments for HWW and HRW genotypes, (ii) assess the level of PHS resistance among the two classes, and (iii) determine the relative merits of germination tests and spike‐wetting treatments. Twenty‐four HWW experimental lines, three HWW cultivars, and five HRW cultivars were evaluated at Stillwater and Lahoma, OK, in 1995 and 1996. Differences in sprout damage measured at two harvest dates were clearly evident between HRW and HWW entries. Pre‐harvest sprout resistance measured at physiological maturity varied widely among HWW lines. No line was as resistant as Plainsman V, a HRW cultivar previously not known to possess high PHS resistance. Two lines were equivalent to the most resistant HWW cultivar, Rio Blanco. Major genes for red kernel color did confer some protection from pre‐harvest sprouting, but their absence did not preclude useful levels of resistance. Chaff tissue played a minor role in influencing genetic differences in resistance. Germination percent at physiological maturity was strongly correlated with field measurements of sprout damage and showed high repeatability. Future improvement of PHS resistance is needed in HWW wheat and should emphasize this component.
Relationship between Relative Water Content, Nitrogen Pools, and Growth of Phaseolus vulgaris L. and P. acutifolius A. Gray during Water Deficit
Authors: Lazcano‐Ferrat Ignacio , Lovatt Carol J.
Published: July 2010

Phaseolus acutifolius A. Gray is a potential source of stress‐tolerant traits for Phaseolus vulgaris L. through interspecific hybrids. The objective of this study was to quantify the effects of water‐deficit stress on vegetative growth, shoot relative water content (RWC), and leaf concentrations of proline, polyamines, and related metabolites in P. vulgaris compared with P. acutifolius. Stress‐induced changes in N metabolism putatively related to stress tolerance have not been investigated previously in P. acutifolius. Replicate pots, each containing three 5‐d‐old plants in 18.9 L of soil with 4 L of available water, were subjected to water deficit by withholding water (terminal drought) or were maintained under well‐watered (control) conditions. Compared with controls, stressed plants of both species accumulated approximately 55% less shoot dry matter. Root dry matter accumulation was inhibited to a greater degree in P. acutifolius (≈ 70% for two genotypes) than in P. vulgaris (14 and 27% for two genotypes). P. acutifolius maintained greater shoot RWC than P. vulgaris. In droughted plants of P. acutifolius, leaf arginine and proline concentrations did not change, total polyamine (Σ agmatine + putrescine + spermidine + spermine) concentrations decreased, and ammonia increased compared with controls. In P. vulgaris, water deficit increased concentrations of arginine (>30%) and proline (>300%), whereas total polyamine and ammonia concentrations did not change compared with controls. In all four genotypes examined, proline concentration was inversely related to RWC (R2 0.90). Leaf proline concentration is an indicator of plant water status in Phaseolus but not of tolerance or sensitivity of vegetative growth to water deficit.
Analysis of Seed Growth by Linear Increase in Harvest Index
Authors: Bindi M. , Sinclair T. R. , Harrison J.
Published: July 2010

A convenient and stable method for expressing crop seed growth is important both in experimental and simulation studies. The conventional approach has been to measure the seed growth rate (SGR) of individual seeds and multiply this by the number of seeds per unit ground area. An alternative to measurements of SGR has emerged from the observation that during seed growth, harvest index (HI) increases linearly over time. The objective of this study was to examine and compare SGR and dHI/dt as the appropriate description of crop seed growth on the basis of 22 data sets representing four crop species for which there were intensive measures of seed growth and HI. Seed growth was analyzed by linear, quadratic, cubic, and logistic models, in regression analysis. These analyses showed that SGR and dHI/dt were not constant for the entire seed growth period. However, constant values for these two measures of seed growth were statistically equivalent to a cubic function of seed growth for much of the seed growth period. A linear increase in SGR and dHI/dt was found to be statistically appropriate when seed weight and harvest index were increasing from 10 to 90% of their maximum value. It was found in comparisons of the coefficients of variability that the stability of dHI/dt was greater than for SGR for individual cultivars grown under a range of conditions. Overall, this analysis indicated that a constant dHI/dt is an attractive approach for expressing crop seed growth.
Inheritance of Phyllochron in Barley
Authors: Dofing Stephen M.
Published: July 2010

Phyllochron, defined as the time between elongation of successive leaves, influences the development of cereals. Small phyllochron may be advantageous for barley (Hordeum vulgare L.) grown in cool or short‐season conditions, in order to increase the number of leaves produced from a given number of heat units, usually measured in growing degree days (GDD). Although environmental effects on phyllochron have been extensively studied, the inheritance of phyllochron has received little attention. The purpose of this study was to quantify the inheritance of phyllochron in barley, and determine its genetic relationship with other agronomic traits. Phyllochron, leaf number, and other traits were measured on parents and 33 double‐haploid lines in two crosses grown at Palmer, AK, for 3 yr. Heritability of phyllochron was 91.1% in one cross and 70.6% in the second. Despite the relative similarity of parents for phyllochron within each cross, a wide range of phyllochron was observed in their progeny, ranging from 51.7 to 69.7 GDD leaf−1 in one cross and 53.0 to 67.9 GDD leaf−1 in the other. In both crosses, phyllochron was positively associated with time to maturity, but not with grain yield. Selection for small phyllochron reduced time to maturity, but also reduced grain yield in one cross. These results indicate that phyllochron is a good measure of plant development, and that it is associated with time to maturity and other developmental traits.
Antioxidant Response to Harmone‐Containing Product in Kentucky Bluegrass Subjected to Drought
Authors: Zhang Xungzhong , Schmidt R. E.
Published: July 2010

The purpose of this study was to determine if exogenous hormonecontaining products (HCP) (seaweed extract and humic acid) enhance endogenous antioxidant concentration in Kentucky bluegrass (Poa pratensis L.) subjected to drought. Two‐week‐old seedlings of Kentucky bluegrass (cv. Plush) were treated with seaweed extract at 326 g ha−1, humic acid (25% active) at 5 L ha−1, alone or in combination, and grown under two soil moisture levels (−0.03 MPa and −0.5 MPa) for 5 wk, and subsequently analyzed for antioxidant concentration and growth. The HCP treatments improved leaf water status and enhanced shoot and root growth regardless of soil moisture levels. Water stress induced a significant increase of α‐tocopherol, ascorbic acid, and β‐carotene content but did not influence superoxide dismutase (SOD) activity. Foliar application of HCP significantly increased α‐tocopherol, ascorbic acid, β‐carotene content, and SOD activity, especially under low soil moisture (LSM). Positive correlations between antioxidants and antioxidants with growth parameters were observed in Kentucky bluegrass grown under either LSM or high soil moisture (HSM). These data indicate that HCP enhancement of the grass's endogenous antioxidant status may contribute to turfgrass drought tolerance.
Recovery of Superior Homozygous Progeny from Biparental Crosses and Backcrosses
Authors: Isleib T. G.
Published: July 2010

Breeders of self‐pollinated species are often confronted with the question of how best to incorporate exotic germplasm into breeding populations. The objective of this work was to illustrate those situations in which a breeder might utilize one or more backcrosses to the better parent of a self‐pollinating population to increase the probability of recovery of desirable homozygous progeny from the population. The stochastic theory is presented along with probabilities associated with different conditions. The number of cycles of backcrossing needed to recover desirable progeny is a function of three variables specific to a particular pair of parents: the number of allelic differences between parents (N), the proportion (k) of desirable alleles in the better parent, and the number of loci homozygous for desirable alleles by which a progeny must exceed the number in the better parent to be selected (nd). In crosses between parents bearing equal or nearly equal numbers of desirable alleles (k close to 0.5), selfing provides the greatest probability of recovering the desired plants. As k approaches 1, the increased probability of recovering desirable alleles by backcrossing to the better parent outweighs the decreased probability of recovering desirable alleles from the worse parent, and backcrossing is indicated. With increasing N, or increasing nd, more cycles of backcrossing are needed to maximize the probability of recovery of desirable plants.
Prediction Assessment of Shrinkage Estimators of Multiplicative Models for Multi‐Environment Cultivar Trials
Authors: Cornelius Paul L. , Crossa José
Published: July 2010

Multiplicative statistical models such as the additive main effects and multiplicative interaction model (AMMI), the genotypes regression model (GREG), the sites regression model (SREG), the completely multiplicative model (COMM), and the shifted multiplicafive model (SHMM) are useful for studying patterns of yield response across sites and estimating realized cuitivar responses in specific environments. Traditionally the series of multiplicative terms is truncated at some point beyond which further terms are believed to have little statistical significance or predictive value. Shrinkage estimators have been advocated as a model fitting method superior to model truncation. In this study, by data splitting and cross validation, we evaluated the predictive accuracy of (i) truncated multiplicative models, (ii) shrinkage estimators of multiplicative models, (iii) Best Linear Unbiased Predictors (BLUP) of the cell means based on a two‐way random effects model with interaction, and (iv) empirical cell means in one wheat [durum (Triticum turgidum L. var. durum) and bread (Triticum aestivum L.)] and four maize (Zea mays L.) cultivar trials, with and without adjustment for replicate differences within environments. Shrinkage estimates of multiplicative models were at least as good as the better choice of truncated models fitted by least squares or BLUPs. Shrinkage estimation yields potentially better estimates of cultivar performance than do truncated multiplicative models and eliminates the need for cross validation or tests of hypotheses as criteria for determining the number of multiplicative terms to be retained. If random cross validation is used to choose a truncated model, data should be adjusted for replicate differences within environments.
Do Second Cycle Maize Inbreds Preserve the European Flint Heterotic Group?
Authors: Cartea M. E. , Revilla P. , Butrón A. , Malvar R. A. , Ordás A.
Published: July 2010

Knowledge of heterotic patterns is essential in hybrid maize (Zea mays L.) breeding programs. Second cycle inbreds of maize were developed from crosses between three historical European inbreds (EP1, F2, and F7) and American or European germplasm. The objective of this study was to find out if the second cycle inbreds derived from EP1, F2, and F7 preserved the European flint heterotic group. Crosses of first and second cycle inbreds with four testers (W64A, A619, A632, and W117) were evaluated in northwestern Spain. Second cycle inbreds from EP1 or F2 × European germplasm had the highest yield and early vigor in crosses to the testers, probably because flint × dent heterosis was preserved. The U.S. germplasm used to develop second cycle inbreds from EP1 and F2 included germplasm from the open‐pollinated variety Minnesota No. 13. The use of Minnesota No. 13 germplasm to develop second cycle inbreds from crosses to European flint should be avoided because almost all the early U.S. Corn Belt dent inbreds introduced into Europe are related to Minnesota No. 13. ‘Lancaster’ germplasm was suitable to improve the yield of F7, but this material lacked early vigor. Lancaster‐related second cycle inbreds performed better for yield than the ‘Reid Yellow Dent’ because two testers were of Reid origin. The highest early vigor was obtained for second cycle inbreds from F7 × European inbreds. European flint germplasm is appropriate for improving European inbreds in crosses to U.S. germplasm, whereas the U.S. germplasm may be used to improve a specific cross.
Photosynthetic Characteristics of Three Asparagus Cultivars Differing in Yield
Authors: Faville Marty J. , Silvester Warwick B. , Green T. G. Allan , Jermyn William A.
Published: July 2010

The physiological basis of yield in asparagus (Asparagus offincinalis L.) is poorly understood, but some reports have inferred a link between lateral fern photosynthesis (A) and annual spear yield. Gas exchange measurements were made on single lateral ferns of mature asparagus plants in the field and younger, potted plants. Among three cultivars with different levels of yield, the light‐saturated rate ofphotusynthesis (Asat) was positively associated with crop yield in both sets of plants. There was a highly significant correlation between Asat and stomatal conductance (gs). Asat also increased with fern nitrogen, chlorophyll, and soluble protein concentrations across the cultivars. These data imply that differences in both gs and photosynthetic capacity contributed to the variation in Asat, and this was supported by AJCI (internal CO2 concentration) analysis. Variation in photosynthetic capacity was related to genotypic differences in cladophyli diameter and thus the content (per unit sudace area) of photosynthetic biochemical constituents and, possibly, mesophyll resistance to CO2 diffusion. The possibility of genotypic variation in other photosynthetic parameters was also noted. It is concluded that fern Asat might be a predictor of yield in asparagus, and of potential use in early selection for breeding, but confirmation of such a relationship requires investigation in a wider range of genotypes.
Weed Invasion in New Stands of Alfalfa Seeded with Perennial Forage Grasses and an Oat Companion Crop
Authors: Spandl Eric , Kells James J. , Hesterman Oran B.
Published: July 2010

Weed invasion in alfalfa (Medicago sativa L.) may be reduced by seeding with a perennial forage grass. Our objectives were to determine if any of four perennial forage grasses influenced weed invasion when seeded with alfalfa, with and without an oat companion, and if this reduction was consistent among harvests and throughout the duration of the stand. Alfalfa was seeded alone and in binary mixtures with smooth bromegrass (Bromus inermis Leysser), orchardgrass (Dactylis glomerata L.), timothy (Phleum pratense L.), or Kentucky bluegrass (Poa pratensis L.). All forages were seeded with and without an oat (Avena sativa L.) companion crop in May of 1993 and 1994. Seeding grasses with alfalfa occasionally reduced weed yield in the first 2 yr of the stand. Weed density was not influenced by the perennial grasses in the seeding year. In the third year, mixtures containing orchardgrass or Kentucky bluegrass reduced weed yields by 20 to 130 kg ha−1 in three of four harvests and dandelion (Taraxacum officinale Wigg.) density up to 5.4 plants m2 (71%). Bromegrass and timothy did not persist with four annual harvests. Seeding the mixtures with an oat companion reduced weed and perennial grass yield in the seeding year and perennial grass yield the fo|lowing year. As a result, dandelion density in the third year was 2.6 plants m2 (70%) greater in mixtures established with oat than without oat. Including perennial forage grasses can be effective at reducing weed invasion by the third year of the stand if grass is maintained as a major component of the forage.
Quantitative Trait Loci Associated with Kernel Traits in a Soft × Hard Wheat Cross
Authors: Campbell Kim Garland , Bergman Christine J. , Gualberto Daisy G. , Anderson James A. , Giroux Micheal J. , Hareland Gary , Fulcher R. Gary , Sorrells Mark E. , Finney Patrick L.
Published: July 2010

Kernel morphology and texture influence the value of wheat (Triticum aestivum L.). The objectives of this study were to determine associations between kernel traits and molecular markers and to identify quantitative trait loci (QTLs) affecting kernel traits in a soft × hard white wheat cross. Seventy eight F2:5‐derived recombinant inbred lines (RILs) from cross between the soft white wheat NY6432‐18 (NY18) and the hard white wheat ‘Clark's Cream’ (CC) were developed by single seed descent. Kernel texture was measured by near infrared reflectance (NIR) on RIL grain samples from six environments. Digital image analysis (DIA) was used to measure kernel length, width, area, perimeter on grain samples from four environments. Test weight and thousand kernel weight (TKW) were also determined. Shape factor and density factor were calculated. The map for this population consisted of 313 molecular markers in 47 linkage groups located on all wheat homoeologous chromosome groups. Linkage groups that mapped to wheat homoeologous group 2 chromosomes were highly skewed towards NY18 alleles. Genotype effects and genotype × environment interactions were highly significant for most traits. QTLs for kernel width and kernel length also influenced kernel area and TKW, but did not influence each other. The pinB marker at the puroindoline B locus on chromosome 5DS explained over 60% of the phenotypic variation for kernel texture. QTLs for kernel traits were located on chromosomes IA, 2B, 2D, 3B, 7A, and 7B.
Progenitor Germplasm of Domisticated Hexaploid Oat
Authors: Zhou X. , Jellen E. N. , Murphy J. P.
Published: July 2010

Cultivated hexaploid oat (Avena sativa L. and A. byzantina C. Koch) is classified as a secondary crop, i.e., derived from weeds of the primary cereal domesticates of the Near East. Avena sterilis L., the oldest hexaploid oat, is the putative progenitor of all other cultivated and wild hexaploid oat species. The objectives of this research were to gain insight into the origin of cultivated hexaploid oat by means of random amplified polymorphic DNA (RAPI)) marker variation and the distribution of the 7C‐17 intergenomic chromosomal translocation in cultivated and progenitor accessions. Cluster analyses based on 248 polymorphic RAPD markers found close association between several A. sterilis accessions from the Iran‐Iraq‐Turkey region and cultivated accessions. Genotypes within this group of cultivated and progenitor accessions were divided into those with the 7C‐17 translocation (A. sativa and A. sterilis) and those without the translocation (A. byzantina and A. sterilis). The results suggested that all cultivated hexaploids are derived from progenitor germplasm from Southwest Asia, present‐day Iran, Iraq, and Turkey. At least two paths of domestication occurred: one from A. sterilis with the translocation to A. sativa and one from A. sterilis without the translocation to A. byzantina.
Winter Annual Legumes for Use as Cover Crops in Row Crops in Northern Regions
Authors: Brandsæter Lars Olav , Netland Jan
Published: July 2010

Weed suppression is one of several benefits achieved by including a cover crop in a cropping system. A requirement for developing cover crop systems is to find species and cultivars which are adapted for the local climate and latitude, prevent weed infestation, and do not compete with the main crop. Two experimental series were established at three locations in Norway to evaluate the ability of different species for use as cover crops in vegetable production. The first series of experiments was with subclover (Trifolium subterraneum L.) cultivars sown at different dates throughout the summer and the second with different winter annual legume species sown in late summer. Winter hardiness, life cycle, growth characteristics, and weed suppression ability of winter annual legumes sown in the autumn were studied. The experiments showed the following ranking of winter hardiness: hairy vetch (Vicia villosa Roth.) (best), black medic (Medicago lupulina L.), crimson clover (Trifolium incarnatum L.), and subclover (poorest). Time of flowering and senescence, factors related to competition in cover crop systems, showed that subclover was the most promising species followed by crimson clover and hairy vetch–black medic. The winter annual legume species showed the ability for natural reestablishment in the second autumn. Hairy vetch showed the highest biomass production, the lowest regrowth ability after mowing, and the best weed suppression. Subclover showed a very promising life cycle for the use as living mulch; however, more winter hardy cultivars or species with similar growth characteristic are needed before common commercial use in northern regions. In conclusion, until more suitable species or cultivars are found or developed through plant breeding, hairy vetch is the most promising winter annual cover crop under Norwegian conditions.
Sorghum Intercropping Effects on Yield, Morphology, and Quality of Forage Soybean
Authors: Redfearn Daren D. , Buxton Dwayne R. , Devine Tom E.
Published: July 2010

Shading patterns when two forage species are intercropped may be different than in a monocrop environment. Our objectives were to quantify yield and forage quality response of forage soybean [Glycine max (L.) Merr.] intercropped with forage sorghum [Sorghum bicolor (L.) Moench] and compare to the measurements of monocrop soybean. Soybean plants were harvested from the middle portion of individual rows in plots containing only soybean and from plots having alternating soybean and sorghum rows spaced 76 cm apart. Morphological and forage quality measurements were determined on leaf and stem fractions. Morphological measurements included main stem length, node number, leaf area ratio (LAR), specific leaf weight (SLW), and stem diameter. Forage quality constituents included in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), hemicellulose, and cellulose, and crude protein (CP) concentrations. Intercropped soybean had 6 more plants m−1 of row, less advanced morphological development, and 2.3 Mg ha−1 less dry matter than monocrop soybean. Leaf IVDMD, NDF, hemicellulose, and cellulose did not differ between intercrop and monocrop soybean. However, stem IVDMD was 33 g kg−1 greater for intercropped than monocrop soybean, reflecting the 36 g kg−1 decrease in NDF concentration. Intercropped soybean was lodged both years more than monocrop soybean, which may have been due to the significant decrease in stem NDF. Leaf CP concentration was 25 g kg−1 greater for monocrop soybean than intercropped soybean; however, stems from intercropped soybean had 12 g kg−1 greater CP than monocrop soybean stems. Soybean exhibited a high degree of morphological plasticity, presumably in response to increased competition for solar radiation. Although forage quality of intercrop soybean was greater than monocrop soybean, intercropping forage‐type soybean with another tall‐growing forage does not appear to be practical because of the decrease in dry matter accumulation.
Survival Characteristics of Corn Seed during Storage: II. Rate of Seed Deterioration
Authors: Tang Shande , TeKrony Dennis M. , Egli Dennis B. , Cornelius Paul L.
Published: July 2010

The Ellis‐Roberts deterioration model depends on the assumption that the rate of seed deterioration is the same among seed lots of a crop species when stored in identical environments. The rate of deterioration of 11 corn (Zea mays L.) seed lots from six hybrids was measured during storage in various combinations of constant temperatures (20, 30, 40, and 50°C) and seed moisture contents (100, 120, 140, and 160 g kg−1, fresh weight basis). The seed‐survival curves were constructed by conducting successive germination tests at frequent intervals during storage. The rates of seed deterioration were estimated by probit analysis and differences among seed lots were identified by analysis of variance. The deterioration rates were significantly different among seed lots in 16 of 21 storage environments when analyzing full data sets (all data points) and in 14 of 21 storage environments when using truncated data sets (germination percentages between 5 and 95%). Both genotype and initial seed quality affected the rate of deterioration with low‐vigor seed lots generally deteriorating at a faster rate than high‐vigor seed lots. The rate of deterioration was greatly influenced by storage environment and increased with an increase in storage temperature, seed moisture, or both. The assumption of a constant rate of seed deterioration in identical storage environments was not valid for hybrid corn seed.
Yield Potential, Plant Assimilatory Capacity, and Metabolic Efficiencies
Authors: Loomis R. S. , Amthor J. S.
Published: July 2010

The structure, control, and efficiency of photosynthetic and respiratory systems are examined. Genetic control is complex and highly conserved. While many features are still unresolved, basic efficiency seems little altered by domestication and breeding of crops. Rubisco, the carboxylase–oxygenase enzyme central to photosynthesis and photorespiration, remains a weak point but may be amenable to improvement. However, the actual radiation‐use efficiency of crops is generally less than the potential with present rubisco kinetics, leaving considerable room for improvement without change in rubisco. Good opportunities for progress lie in definition of optimal canopies of leaves having suitable acclimation and photoprotection. The efficiency of the respiratory system also seems unaffected by plant breeding. Precise evaluation of the roles and efficiencies of the glycolytic pathway and the tricarboxylic acid cycle in production is difficult because, in addition to being sources of energy carriers and reductant, those systems also supply carbon skeletons for biosyntheses. How those systems are controlled and balanced for such diversions is largely unknown. The alternative oxidase found in mitochondria may be involved in that balance but its true role(s) is also unknown. Distinguishing two components of respiration, one related to maintenance and the other to growth, remains a powerful tool in theoretical studies. In such work, the respiratory system appears efficient, but proving that in experiments remains elusive.
Physiological and Genetic Changes of Irrigated Wheat in the Post–Green Revolution Period and Approaches for Meeting Projected Global Demand
Authors: Reynolds M. P. , Rajaram S. , Sayre K. D.
Published: July 2010

Global demand for wheat (Triticum aestivum L.) is growing faster than gains in genetic yield potential are being realized, currently a little under 1% per year in most regions. Improvement in yield of semidwarf wheat has generally been associated with increased harvest index (HI) and grain per square meter. For CIMMYT (International Maize and Wheat Improvement Center) varieties released between 1962 and 1988, yield increase was also associated with higher flag‐leaf photosynthetic rate and related traits, but not higher biomass. Nevertheless, significantly higher biomass has been reported in more recent CIMMYT lines. Improved HI is associated with higher N use efficiency (yield per unit of available N) and improved yield of semidwarf lines is expressed at high and low levels of N input. Where interplant competition for light and soil factors are manipulated, yield improvement is associated with adaptation to high plant density. Studies have confirmed that the juvenile spike growth phase is critical in determining both grain number and kernel weight (sink) potential. Improving assimilate availability during this stage, perhaps by lengthening its relative duration, may be one way to improve yield potential. Traits that could potentially be exploited for improving assimilate (source) capacity include early vigor, stay‐green, leaf‐angle, and remobilization of stem reserves. Use of alien chromatin is a successful approach for introducing yield‐enhancing genes into elite genetic backgrounds. Examples include the 1B/1R chromosome translocation from rye (Secale cereale L.), and more recently the LR19 segment from tall wheatgrass [Agropyron elongatum (Host) P. Beauv.] Improving the efficiency of early‐generation selection may be another strategy for raising yield potential by increasing the probability of identifying physiologically superior lines by techniques such as infrared thermometry and spectral reflectance.
Genetics of Soybean Agronomic Traits: I. Comparison of Three Related Recombinant Inbred Populations
Authors: Orf J. H. , Chase K. , Jarvik T. , Mansur L. M. , Cregan P. B. , Adler F. R. , Lark K. G.
Published: July 2010

Molecular markers provide a rapid approach to breeding for desired agronomic traits. To use them, it is necessary to determine the linkage between quantitative trait loci (QTLs) and such markers. The objective of this research was to determine such linkage in recombinant inbred (RI) soybean [Glycine max (L.) Merrill] populations. To do this, RI soybean segregants were characterized for molecular genetic markers and traits measured in several different environments. QTLs then were identified by interval mapping. Agronomic traits were measured and compared in large (about 240 segregants) RI populations derived from crosses between the cultivars Minsoy and Noir 1 (MN population), Minsoy and Archer (MA population), and Noir 1 and Archer (NA population). The MA and NA populations were grown together as two replications in each of four environments. Measurements from the MN population were reported previously and were taken from three replications grown in four environments. Traits measured were plant height, lodging, date of flowering, reproductive period, maturity, yield, seed weight, seed oil, seed protein, leaf length, and leaf width. Additional traits were derived from these primary measurements. Each of the three RI populations was also characterized by a large (>400) number of molecular genetic markers including RFLP (restriction fragment length polymorphism) and SSR (simple sequence repeat polymorphisms). QTLs were identified for all of the primary and derived traits at a significance level ≥LOD 3 on 17 of the 20 linkage groups and tended to be clustered on three. QTLs with major effects (R2 > 10%) were identified for all traits, and for many, these explained more than half of the heritable variation. Comparison of QTLs between the three RI populations established that for the majority of the traits, only two alleles could be identified. In only a few instances could a third allele be detected. Many of the significant QTLs identified in one population were confirmed in another. However, an almost equal number were found in only one population, suggesting that a dependence on the genetic background for expression (epistasis) was common.
Potential of Using Plant Row Yield Trials to Predict Soybean Yield
Authors: Hegstad J. M. , Bollero G. , Nickell C. D.
Published: July 2010

Plant row yield trials (PRYT) are measured as an indicator of yield potential for many private and public soybean breeding programs. To identify elite lines and develop new cultivars, the highest yielding PRYT lines are usually advanced to multiple replications in different environments. Early generation PRYT testing has the advantage of identifying elite lines in the initial phases of the selection process. The objective of this study was to determine if single row PRYT testing is a reliable predictor of yield in multiple environment advanced yield testing. In 1996, five F2:3 populations of crosses between different elite cultivars were grown as single row PRYT. After the 1996 PRYT test, the top 10, middle 10, and bottom 10 yielding PRYT lines from each population were selected for advanced testing in 1997 and 1998. Yield and yield rank correlations between selected 1996 PRYT and advanced yield testing were highest for the ‘Jack’ × ‘Resnik’ and ‘Asgrow A3733’ × ‘Burlison’ populations, respectively. Matrix analysis indicated that the lines selected from the Asgrow A3733 × Burlison population were the most stable when 1996 PRYT data are compared with advanced yield test data. Approximately five lines can be identified from each population that are the highest yielding in PRYT testing and advanced yield testing. Additionally, approximately five lines could be identified from each population that are the lowest yielding in PRYT testing and advanced yield tests. In the populations examined it can be concluded that early generation PRYT testing would allow for progress to be made in identifying elite soybean lines with high yield potential.
FISH and RFLP Marker‐Assisted Introgression of Festuca mairei Chromosomes into Lolium perenne
Authors: Chen C. , Sleper D. A.
Published: July 2010

Plant breeders and geneticists have attempted for several decades to combine perennial ryegrass (Lolium perenne L.) with fescue (Festuca spp.) to create novel forage grasses containing both high forage quality and good drought tolerance. Difficulty in selecting true hybrids with alien chromatin or chromosome addition–substitution has been a major barrier in Festuca × Lolium breeding programs. In this investigation, fluorescence in situ hybridization (FISH) and restriction fragment length polymorphism (RFLP) markers were used to monitor transfer of Festuca mairei St. Yves chromosomes into L. perenne through intergeneric hybrids. Among 64 hybrid plants of the BC1G1 generation (intercrossed progeny of first backcross to L. perenne), chromosome addition and substitution of F. mairei were identified by FISH using total genomic DNA of F. mairei as a probe. Forty‐two clones from a Pst I‐genomic DNA library of F. arundinacea Schreb. were used to screen for the presence of F. mairei DNA in the hybrid plants. These RFLP probes rapidly identified presence of the F. mairei genome in F1, F2, BC1, but not in BC2 plants. In contrast, genomic FISH on meiotic cells effectively detected any F. mairei chromosomes as well as chromosomal pairing relationships in any hybrid. By monitoring and selectively introducing F. mairei chromosomes into ryegrass, these molecular markers may accelerate the Festuca × Lolium breeding for improvement of ryegrass.
Using Amplified Fragment Length Polymorphisms and Simple Sequence Length Polymorphisms to Identify Cultivars of Brown and White Milled Rice
Authors: Bligh H. F. J. , Blackhall N. W. , Edwards K. J. , McClung A. M.
Published: July 2010

Increase in world rice consumption combined with the recent World Trade Organization General Agreement on Trade and Tariffs agreement on import tariffs have resulted in a need for a method to distinguish between white milled rice (Oryza sativa L.) cultivars sold at a premium from other milled cultivars. We have used two DNA‐based methods, amplified fragment length polymorphisms (AFLPs) and simple sequence length polymorphisms (SSLPs), to distinguish six genetically related long‐grain rice cultivars, and a premium Basmati cultivar. Of the two methods, AFLPs proved difficult to reproduce due to the quality of DNA that could be extracted from the samples, while SSLPs showed sufficient variation to distinguish all seven cultivars with only a small number of markers. Our study demonstrates that, using white milled grains, SSLPs are a more robust and efficient method than AFLPs for the identification of rice cultivars. We also report the development of six new SSLP primer sets.
Soybean Canopy Development as Affected by Population Density and Intercropping with Corn: Fractal Analysis in Comparison with Other Quantitative Approaches
Authors: Foroutan‐pour Kayhan , Dutilleul Pierre , Smith Donald L.
Published: July 2010

To better understand how crops intercept light, the complexity of plant structure needs to be characterized. Fractal analysis provides a novel approach for quantifying the geometric structure of individual plants. The objectives of this study were to determine (i) an appropriate methodology for estimating fractal dimension (FD) two‐dimensionally for complex three‐dimensional structures of plants such as soybean [Glycine max (L.) Merr.]; (ii) whether the temporal pattern of FD for soybean structure is altered by population density or intercropping with corn (Zea mays L.); and (iii) how the FD for soybean structure compares with other quantitative measures of shoot development. Soybean plants were randomly sampled in monocropped soybean and intercropped corn‐soybean plots grown at the same site in three successive years. Sampled plants were cut at the stem base, and leaf blades were immediately detached. Leafless plant structure was photographed from the side which allowed maximum appearance of branches and petioles. The FD was estimated two‐dimensionally from the scanned and processed images. Fractal dimension of soybean leafless structure increased with time for all treatments, coincident with the increasing complexity of structure as shoots developed. The rate of linear increase of FD with time varied among treatments. Leaf area per plant, plant height, and number of leaves per plant increased with time for all treatments, indicating a positive correlation with FD. In contrast, light penetration decreased during canopy development, and was negatively correlated with FD. Whereas leaf area evaluates the surface available for light interception, FD characterizes its geometric distribution in space.