bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple Sequence Repeat Markers Linked to the Soybean Rps Genes for Phytophthora Resistance
Authors: Demirbas A. , Rector B. G. , Lohnes D. G. , Fioritto R. J. , Graef G. L. , Cregan P. B. , Shoemaker R. C. , Specht J. E.
Published: July 2010

Simple sequence repeat (SSR) markers with linkages to the Rps1, Rps2, Rps3, Rps4, Rps5, and Rps6 loci that govern soybean [Glycine max (L.) Merr.] resistance to Phytophthora root rot (caused by Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Ervin) are desired. Near‐isogenic lines (NILs) of Clark or Williams, homozygous resistant (RpsRps) at just one of those Rps loci, were mated to a NIL of Harosoy homozygous susceptible (rpsrps) at all six loci. From the 100 to 120 F2:3 progenies per mating, 20 F3 seedlings were evaluated for resistance (R) or susceptibility (S) following inoculation with the race of P. megasperma affected by the segregating Rps allele. About 15 RpsRps and 15 rpsrps F2 individuals were used to construct contrasting DNA bulks. Presumptive linkage (i.e., SSR marker polymorphism between two bulks) was confirmed or refuted by SSR assay of 15 to 40 F2 individuals within each homozygous class. Recombination values were maximum likelihood estimates from the SSR allelic segregation data of both classes, although the rpsrps class was less prone to phenotypic classification error. SSRs on linkage groups (LGs) N, J, F, and G were identified with linkages to Rps1, Rps2, Rps3, and Rps4, respectively. A skewed R:S segregation in the Rps5 population precluded detection of linked SSRs. The Rps6 locus, whose map position was heretofore unknown, was linked with three SSRs in a region of LG‐G that contains Rps4 and Rps5 SSR–Rps linkages of P < 0.05 could only be identified for the Rps1 alleles because of a paucity of SSR markers and/or parental monomorphism in the genomic regions surrounding other Rps loci.
Costing the Conservation of Genetic Resources: CIMMYT's Ex Situ Maize and Wheat Collection
Authors: Pardey Philip G. , Koo Bonwoo , Wright Brian D. , Van Dusen M. Eric , Skovmand Bent , Taba Suketoshi
Published: July 2010

Worldwide, the number of genebanks1 and the amount of seed stored in them has increased substantially over the past few decades. Most attention is focused on the likely benefits of conservation, but conserving germplasm involves costs whose nature and magnitude are largely unknown. Moreover, these costs place a lower bound on the benefits deemed likely to justify the expense of conserving seed. In this study, we compile and use a set of cost data for wheat (Triticum aestivum L.) and maize (Zea mays L.), stored in the CIMMYT genebank to address a number of questions. The marginal costs of holding an existing accession for one more year are presented, along with the costs of conserving saved seed for the life of the genebank (taken here to be 40 yr), and in perpetuity We also investigated the scale economies evident in the CIMMYT genebank operation as a basis for assessing the economics of consolidating several genebanks. For accessions known to satisfy viability requirements, it costs just $0.19 and $0.93 to carry over an existing accession of wheat and maize respectively, for one more year; $7.19 and $30.24 to store an accession of each crop for the life of a genebank, and $10.26 and $58.85 to conserve accessions in perpetuity. Under baseline assumptions about interest rates, capital depreciation, and regeneration regimes, the present value of conserving the existing accessions in perpetuity at CIMMYT is $8.86 million—$3.87 million for storing the 123000 wheat accessions and $4.99 million for the 17000 maize samples. Maintaining the current level of effort to distribute accessions free‐of‐charge to those who request them would cost an additional $5.28 million in perpetuity.
Genetic Diversity among Soybean Accessions from Three Countries Measured by RAPDs
Authors: Li Zenglu , Nelson Randall L.
Published: July 2010

Soybean [Glycine max (L.) Merr.] was domesticated in China but has a long history of cultivation on the Korean peninsula and in Japan. All three areas are considered important sources of soybean germplasm. The objectives of this study were to evaluate the genetic variation in soybean within and among China, S. Korea, and Japan by means of 120 accessions from eight Chinese and three S. Korean provinces, and three Japanese districts; and to relate genetic diversity patterns to geographical regions. Genetic relationships were estimated by 115 random amplified polymorphic DNA (RAPD) markers with simple matching coefficients expressed as Euclidean distances. Hierarchical and nonhierarchical cluster analyses as well as principal component analysis were used to define relationships among the genotypes. The results indicate that the mean genetic distance within China is much larger than that within Japan or S. Korea, but smaller than that between China and Japan or S. Korea. Cluster and principal component analyses almost completely separated the accessions from China from those of Japan and S. Korea, but could not distinguish between the accessions from Japan and S. Korea. These results are consistent with previous research using enzymes and morphological data to classify soybean germplasm from Asia. The groups formed by cluster analysis were mainly based on the frequencies of RAPD fragments among accessions and generally reflected the geographical regions of origin. No clear relationship was found between latitude and genetic diversity among accessions from these countries. Although the soybean accessions from Japan and S. Korea originally came from China, these data indicate that current accessions from Japan and S. Korea are genetically very distinct from those from China and more similar to each other.
Evaluation of a ninhydrin procedure for measuring membrane thermostability of wheat
Authors: Cekic Cemal , Paulsen Gary M.
Published: July 2010

Membrane thermostability (MT) is used widely to measure high‐temperature tolerance of wheat (Triticum aestivum L.). However, the method, which measures conductivity of electrolytes released from injured cells, is affected by environmental factors for growing plants and is not effective on maturing plants. Amino acids exosmose like inorganic electrolytes from cells that are damaged by high temperature but, unlike electrolytes, typically occur only in living cells. These studies determined whether measuring leakage of amino acids effectively assessed high‐temperature injury to wheat in comparison with the conductivity method, and if it was suitable for evaluating maturing plants. Membrane thermostability was measured by conductivity and ninhydrin methods on seedlings and maturing plants grown under controlled conditions and on 12 genotypes at two field locations. Relative injury (RI) values from hardened seedlings differed significantly among 12 genotypes. Rankings of the genotypes were similar for both methods in seedlings (r = 0.94), and values of both methods were significantly correlated in maturing plants (r = 0.90). The RI values by the ninhydrin method but not the conductivity method differed significantly among the 12 genotypes and identified the top‐yielding cultivars at both field locations, but results of neither method correlated with grain yields. The results showed that the ninhydrin method measures high‐temperature injury of young plants as successfully as the conductivity method, but neither method is suitable for maturing plants.
Inheritance of High Oleic Acid Mutations in Winter Oilseed Rape (Brassica napus L.)
Authors: Schierholt A. , Rücker B. , Becker H. C.
Published: July 2010

High oleic (HO) winter oilseed rape (Brassica napus L.) with increased oleic acid content in the seed is of interest for nutritional and industrial purposes. The objectives of the present study were to (i) describe the fatty acid composition in the seed, leaf, and root material of eight HO mutants; (ii) estimate the number of genes controlling the trait; (iii) test whether the mutants are allelic for the mutated loci; and (iv) determine the inheritance of the HO trait. An 8‐by‐8 diallel of the HO mutants and two crosses between HO mutants and a normal type cultivar with their segregating F2 and BC generations were used. The results suggested that the variation in oleic acid can be explained by two mutation events. One mutated locus (HO1) was expressed mainly in the seeds and all mutants were assumed to be allelic at this locus. A second mutated locus (HO2), which increased the oleic acid content not only in the seed but also in leaves and roots, was identified in one mutant line. Both loci showed mainly additive effects: for HO1 a = 8.0 ± 1.5 and for HO1+HO2 a = 9.25 ± 1.5 (in percent oleic acid in the seed oil). Only small nonsignificant dominance effects and no epistatic or maternal effects were observed. The reduction of oleic acid desaturation in the mutants indicates that the HO1 locus is equivalent to fad2, the microsomal oleic acid desaturase, whereas the locus HO2 affects a different enzyme involved in fatty acid biosynthesis or desaturation.
Relationships among Bread Wheat International Yield Testing Locations in Dry Areas
Authors: Trethowan Richard M. , Crossa Jose , van Ginkel Maarten , Rajaram Sanjaya
Published: July 2010

Understanding the relationship among yield testing locations is important if plant breeders are to target germplasm better to different production environments or regions. To examine the relationship among international drought prone test sites, yield data from 122 locations, sown during a 6‐yr period in CIMMYT's Semi‐Arid Wheat Yield Trial (SAWYT) were analyzed. The shifted multiplicative model (SHMM) was used to group locations within each year and pattern analysis was employed to group those sites across years. Sites were grouped into regions representing the major zones of adaptation to drought according to CIMMYT's classification of mega‐environments. Results spanning 1992 to 1997 were summarized on the basis of the number of times a particular site or region clustered with the target region, which was expressed as a fraction or percentage of the total number of possible groupings. Results indicated that the Centro de Investigaciones Agricolas del Noroeste (CIANO), CIMMYT's primary drought evaluation location, clustered with locations in South Asia, specifically India and Bangladesh. However, the number of clusters between CIANO and other Mexican locations with West Asia, Africa, and South America were fewer. This result suggests that the residual moisture stress generated at CIANO under limited irrigation conditions, while relevant to equivalent sites in the Indian Subcontinent, does not predict performance at locations where different stress patterns predominate. Associations among sites and regions, determined on the basis of clustering, ranged from weak (7% of total possible groupings in the case of Mexico and the Southern Cone of South America) to relatively strong (60% for Mexico and Bangladesh). Clusters of sites repeated in more than one year indicated two dominant groups, one for South Asian locations (including CIANO, Mexico) and another containing primarily South American sites.
Leaf Pigment and Canopy Photosynthetic Response to Early Flower Removal in Cotton
Authors: Wells Randy
Published: July 2010

Loss of reproductive organs from cotton (Gossypium hirsutum L.) often results in compensatory growth that culminates in altered morphologic, physiologic, and photosynthetic patterns. This field study examined the change in leaf chlorophyll (Chl) and anthocyanin (Ant) contents and their relationship to canopy photosynthetic patterns in response to the removal of flowers for the first 2 wk of flowering. Flower removal caused an extended flowering period in all years except 1995 when temperatures were highest. The largest yield differences occurred in 1994, while there were no significant differences in any other year. Differences in canopy photosynthesis occurred on at least one date in each year that measurements were made. In 1997, significant differences were observed on four dates and plants from the removal treatment had 15% larger area under the seasonal photosynthetic curve. Chlorophyll concentrations were higher in leaves from the flower removal treatment after 100 d after planting. Anthocyanin levels were higher in controls during the same period, indicating significant negative relationships between Ant levels and either Chl a/b ratio or Chl concentration. Pigment differences late in plant ontogeny appeared to be associated with delayed senescence of plants from the removal treatment. While pigment levels late in development were associated with canopy photosynthesis, not all treatment differences could be related to Chl loss. In 2 yr, significant differences in canopy photosynthesis occurred prior to differences in Chl concentration, implicating other morphological and physiological adaptations in response to early fruit loss.
Empirical Predictions of Wheat Head Blight in the Northern Argentinean Pampas Region
Authors: Moschini Ricardo C. , Pioli Rosanna , Carmona Marcelo , Sacchi Oscar
Published: July 2010

In Argentina, head blight (caused by Fusarium graminearum Schwabe), is a highly risky disease of wheat (Triticum aestivum L. emm. Thell), although its occurrence is sporadic, depending on prevalent environmental variables. This unpredictability has stimulated the development of predictive models of head blight occurrence that, if successful, would help growers in the selection of control strategies. As a result of our earlier work, empirical equations for predicting head blight incidence were developed at Pergamino INTA Experiment Center (Lat., 33° 56′S), associating temperature and moisture variables with mean disease observations from many wheat cultivars. In the current study our objective was to validate two of these meteorological based equations developed for Pergamino to predict wheat head blight incidence and severity at Zavalla (Lat., 33° 1′S) and Oliveros (Lat., 32° 33′S) in moderately susceptible to susceptible cultivars for the years 1993 to 1995. Even though the t‐test determined nonsignificant differences between mean observed disease values versus predicted values, a graphic method and a deviation examination showed an underestimation at high disease levels. Simple analyses of sensitivity were able to detect the improvement in incidence and severity goodness of fit estimations that resulted from increasing the maximum temperature threshold and the heat accumulation defining the length of the wheat critical period for infection. This study showed that meteorological based empirical equations developed for Pergamino can be useful for predicting disease intensity at more northern locations in the Pampas region, making only a few changes in temperature thresholds.
Meiotic Stability, Chloroplast DNA Polymorphisms, and Morphological Traits of Upland × Lowland Switchgrass Reciprocal Hybrids
Authors: Martínez‐Reyna J. M. , Vogel K. P. , Caha Carol , Lee Donald J.
Published: July 2010

Switchgrass (Panicum virgatum L.) has two cytotypes or cytoplasm types, L and U, that are associated with the lowland and upland ecotypes, respectively. The L cytotypes are tetraploids while the U cytotypes can be either tetraploids or octaploids. The objective of this research was to characterize meiotic stability of reciprocal crosses of U and L plants as indicated by chromosome pairing at meiosis and to determine the mode of inheritance of chloroplast DNA (cpDNA) in the hybrids of these cytotypes. Morphological markers that characterize the parents and hybrids also were investigated to confirm that progeny were true hybrids. Reciprocal crosses were made between Kanlow (L tetraploid) and Summer (U tetraploid) plants. Pubescence on the upper surface of the leaf blade, foliage color, and seed size were evaluated as markers to verify hybridization. Meiotic pairing of some of the hybrids was analyzed at the diakinesis stage of meiosis by means of immature anthers. The clone pRR12 from a spinach (Spinacia oleracea L.) cpDNA library was used as a chloroplast hybridization probe to determine chloroplast inheritance. For all the morphological traits evaluated, the hybrids were intermediate in comparison to the parents except for seed width. Chromosome pairing was primarily bivalent in all hybrids. The viability of the hybrid seed and the normal meiotic chromosome pairing of the hybrids indicate a high degree of similarity between upland and lowland genomes. In the cpDNA analysis, all verified hybrids examined carried a fragment identical in size to the fragment of the female parent, indicating predominance of maternal inheritance of the cpDNA in switchgrass.
Isozyme Diversity in North American Cultivated Red Clover
Authors: Yu J. , Mosjidis J. A. , Klingler K. A. , Woods F. M.
Published: July 2010

Red clover (Trifolium pratense L.) is a forage legume with considerable economic importance in world agriculture. Knowledge of the amount and distribution of genetic variability within a species is vital to breeders and geneticists when selecting breeding germplasm. The objectives of this study were to assess genetic diversity in 34 North American red clover cultivars by means of isozymes. Isozymes assayed were esterase, β‐glucosidase, phosphoglucomutase, peroxidase, diaphorase, phosphoglucoisomerase, and superoxide dismutase. Eleven of the 13 loci (84.62%) were polymorphic in at least one cultivar. Percentage polymorphic loci within cultivar ranged from 61.54% in cv Morred, Persist, and Redland II to 84.62% in cv Arlington, Ram, and Red Baron, with an overall mean of 73.98%. At the species level, the number of alleles per polymorphic locus was 2.55 and effective number of alleles per locus was 1.64. Within‐cultivar averages were 2.71 and 1.59, respectively. Genetic diversity was 0.292 at the species level and 0.285 for within populations. Most of the genetic diversity (98.4–99.7%) was distributed within the cultivars. Grouping the 34 cultivar on the basis of genetic distance indicated that their isozyme variability could be represented by a few cultivar of each of four groups plus the cv Morred and Redon.
Opportunities to Improve Adaptability and Yield in Grasses
Authors: Morgan Page W. , Finlayson Scott A. , Childs Kevin L. , Mullet John E. , Rooney William L.
Published: July 2010

Population trends predict increasing food needs while progress in developmental and genomic plant sciences offer new opportunities for crop improvements. The grass‐based grain crops have a high degree of synteny in their genomes, thus raising the possibility of using specific information more broadly. Studies of Sorghum bicolor (L.) Moench are beginning to link physiological behavior to specific genes and hormone‐based regulatory systems in ways that suggest specific strategies for improvement. Findings from several other grasses are adding to the pool of information being derived from Sorghum This information relates to flowering and floral development, maturity and senescence, temperature effects via the biological clock, shade avoidance behavior, apical dominance, shoot elongation, and root development including constitutive aerenchyma formation. These studies, along with others, offer a number of options for conventional plant breeding and genetic transformations to improve grass‐based crops and satisfy part of the projected human food needs of coming decades.
Inheritance of Fertility Restoration for Two Cytoplasmic Male Sterility Sources of Helianthus pauciflorus (rigidus) Nutt.
Authors: Jan C. C. , Zhang T. X. , Miller J. F. , Fick G. N.
Published: July 2010

New sources of cytoplasmic male sterility (cms) and fertility restoration genes would reduce the genetic vulnerability of commercial sunflower (Helianthus annuus L.) hybrids because of the current use of a single male sterile H. petiolaris Nutt. cytoplasm and a few fertility restoration genes. The objectives of this study were to evaluate the inheritance of fertility restoration, to compare the cytoplasmic similarity between the two cms sources, and to confirm the vigor reducing effect of combining perennial species cytoplasms with cultivated nuclei. Cms‐RMX plants, maintained by backcrossing with inbred line HA89, were crossed with 21 prospective restoration lines. Male‐fertile F1 progeny were observed in crosses with ‘Luch’ and ‘RCMG1’. Segregation of male sterility in F2 and testcrosses with HA89 indicated fertility restoration was controlled by two complementary dominant genes. Identical segregation ratios of male fertile to male sterile in both F2 and testcross F1 were obtained with cms‐RIG1 using the fertility restoration genes identified for cms‐RIGX. These results suggest a single origin of the two cms sources. In a field test, cms‐RIGX plants produced no seeds after self‐pollination, and 99% seed set from open‐pollination, indicating complete male sterility and female fertility. The new cms‐RIG sources and corresponding fertility restoration genes will provide cytoplasmic diversity for sunflower hybrid production.
Selection for Large Seed and High Protein in Two‐ and Three‐Parent Soybean Populations
Authors: Alt Brian J. , Fehr Walter R. , Welke Grace A.
Published: July 2010

Soybean [Glycine max (L.) Merr.] cultivars with large seed size and high protein content are desirable for the production of tofu and other food products. The objectives of this study were to evaluate the amount of genetic variability and the effectiveness of single‐plant selection for seed size and protein in two‐ and three‐parent soybean populations. Two parents with large seed and high protein (LSHP) and one parent with normal seed size and protein (N) were used to produce three population types: LSHP × N, LSHP × LSHP, and LSHP × (LSHP × N). Four sets of the three population types were evaluated with different parents in each set. For each of the populations, 100 random F2 plants and 10 plants of each parent were harvested at Ames, IA, and their seed size and protein were measured. The F3 progeny of the 100 F2 plants and 10 entries of the three parents of each set were evaluated in replicated tests at two Iowa locations. The percentage of F2:3 lines with seed size greater than or equal to the smallest LSHP parent and protein greater than or equal to the lowest LSHP parent in the set averaged 4% for the LSHP × N, 88% for the LSHP × LSHP, and 31% for the three‐parent crosses. Single‐plant selection was not considered cost effective in the LSHP × N populations because the percentage of acceptable segregates was so small or in the LSHP × LSHP populations because the percentage of acceptable segregates was so high. For the three‐parent populations, single‐plant selection was most effective when the F2 plants were ranked for the two traits and those with the most favorable rank were selected for evaluation as F2:3 lines. LSHP × LSHP and three‐parent populations should be the most useful for developing LSHP cultivars.
Fresh Green Seed Yield and Seed Nutritional Traits of Vegetable Soybean Genotypes
Authors: Rao M. S. S. , Bhagsari A. S. , Mohamed A. I.
Published: July 2010

Edamame (pronounced eh‐dah‐MAH‐meh) are large‐seeded soybean [Glycine max (L.) Merr.] harvested as green pods at the R6 stage when the seed are approximately 80% matured. The demand for edamame as fresh or frozen vegetable is increasing worldwide. Currently, lack of adapted edamame cultivars is one of the major factors limiting its commercial production in the southeastern USA. A need exists, therefore, to evaluate and identify Asian vegetable soybean genotypes for potential production and/or as a source of vegetable traits for breeding suitable cultivars. In a 4‐yr study, six Japanese edamame cultivars, four large‐seeded Japanese plant introductions, two Chinese vegetable soybean cultivars, and two adapted U.S. cultivars were evaluated for fresh green pod and seed yields and seed composition at the R6 stage. The genotypes were planted in a randomized complete block with four replications and were harvested at the R6 stage. The mean fresh pod and seed yields were 18.5 and 9.6 Mg ha−1, respectively. The PI 181565, ‘Tambagura’, ‘Shangrao Wan Qingsi’, and PI 200506 with fresh pod and seed yields in excess of 20 and 10 Mg ha−1, respectively, offer potential for commercial production in Georgia. The seed oil and protein contents ranged from 130.7 to 155.8 and 333.2 to 386.0 g kg−1, respectively. The mean glucose content was 67.1 g kg−1, whereas the mean phytate content was 12.6 g kg−1 Fresh pod weight was the major yield determinant (R2 = 0.88). The Japanese edamame genotypes may be utilized as a source of vegetable soybean traits in breeding programs.
Agrobacterium‐Mediated Genetic Transformation of Switchgrass
Authors: Somleva M. N. , Tomaszewski Z. , Conger B. V.
Published: July 2010

Although Agrobacterium tumefaciens has been successfully used to transfer genes to a wide range of plant species, it has received little attention for transformation of forage grasses. Therefore, the objective of the present study was to demonstrate Agrobacterium‐mediated transformation of switchgrass (Panicum virgatum L.). The A. tumefaciens strain AGL 1 carrying the binary vector pDM805, coding for the phosphinothricin acetyltransferase (bar) and β‐glucuronidase (gus) genes, was utilized in these experiments. Somatic embryos, embryogenic calluses, mature caryopses, and plantlet segments served as target tissues for infection. Treated cultures were selected in the presence of 10 mg L−1 bialaphos and the resultant plantlets were treated with the herbicide Basta [monoammonium 2‐amino‐4(hydroxymethylphosphinyl)butanoate]. T‐DNA delivery efficiency was affected by genotype, explant used and the presence or absence of acetosyringone (3′,5′‐dimethoxy‐4′‐hydroxyacetophenone) during inoculation and cocultivation. Approximately 600 transgenic plants were produced, and transformation efficiencies ranged from 0 to nearly 100%. Stable integration, expression, and inheritance of both transgenes were confirmed by molecular and genetic analyses. Approximately 90% of the tested plants appeared to have only one or two copies of the T‐DNA inserts. Controlled crosses between T0 and nontransgenic ‘Alamo’ plants indicated the expected ratio of 1:1 (transgenic:nontransgenic) in T1 plants for both transgenes according to a χ2 test at P = 0.05. These results indicate that the Agrobacterium method is effective for transferring foreign genes into switchgrass.
Soil Fragment Size Distribution and Compactive Effort Effects on Maize Root Seedling Elongation in Moist Soil
Authors: Díaz-Zorita M. , Grove J. H. , Perfect E.
Published: July 2010

Distributions of soil fragments (a mixture of primary aggregates resulting from tillage fragmentation) in seedbeds are known to influence emergence and early shoot and root growth of crops. However, it is not clearly understood which distribution model parameters the roots are responding to when water imbibition and nutrient availability are not limiting factors. The objective of this study was to determine the effect(s) of variation in geometric mean diameter (GMD) and log of the geometric standard deviation (LogGSD) taken from a log‐normal model of soil fragment size distribution on maize (Zea mays L.) root elongation over a range of soil bulk density (ρb) and air‐filled porosity (AFP) levels. Root growth, determined 48 h after seedling emergence, was evaluated in a greenhouse experiment with artificially packed soil fragments sieved from a Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalf) under sod. Two experiments were conducted. The first consisted of a complete factorial combination of four compactive efforts (CEs) (0.0, 26.8, 53.5, and 107.0 kJ m−3) applied over four GMDs (4.3, 5.1, 6.8, and 9.0 mm) at a uniform LogGSD of 0.22. The second experiment was a complete factorial combination of the same four CE treatments applied over three LogGSD (0.22, 0.31, and 0.48) values at a uniform GMD of 5.1 mm. Increasing CE, GMD, or LogGSD caused the ρb to increase. Maximum root elongation occurred at intermediate (5.1–6.8 mm) GMD values when 26.8 kJ m−3 of CE was applied, corresponding to an average ρb of 1.15 Mg m−3 There was no direct effect of the spread in soil fragment size (LogGSD) on root elongation. Total root length density (RLD) showed a quadratic response to ρb, relative bulk density (ρbr), bulk density divided by maximum Proctor density), or AFP levels reaching maximum elongation at values of 1.12 Mg m−3, 0.78 m3 m−3, or 0.187 m3 m−3, respectively. These results suggest that maximum radicle elongation depends more on the size of soil fragments rather than on the spread in their size distribution. Bulk density seems to be a more relevant parameter than size or distribution of soil fragments in characterizing compacted seedbeds. Loose or highly compacted seedbeds are inadequate for maximal early growth of maize roots.
The Seed Protein, Oil, and Yield QTL on Soybean Linkage Group I
Authors: Chung J. , Babka H. L. , Graef G. L. , Staswick P. E. , Lee D. J. , Cregan P. B. , Shoemaker R. C. , Specht J. E.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed protein is negatively correlated with seed oil and often with yield. Our goal was to examine the basis for these correlations at a quantitative genetic locus (QTL) level. Seventy‐six F5–derived recombinant inbred lines (RILs) from the mating of the high‐protein (480 g protein per kg seed) G. max accession PI 437088A with the high‐yield cultivar Asgrow A3733 (420 g kg−1 seed protein content) were evaluated in six irrigation treatments (i.e., 100, 80, 60, 40, 20, and 0% replacement of weekly evapotranspiration loss) of a two‐replicate experiment conducted for 2 yr. The RILs were genotyped with 329 random amplified polymorphic DNAs (RAPDs), 103 simple sequence repeats (SSRs), and four other markers, creating a 2943‐centimorgan (cM) genetic map of 35 linkage group (LGs) that, on the basis of SSR homology, aligned with the 20 known soybean LGs. The phenotypic regression of RIL protein and oil on yield revealed respective linear coefficients of −2.6 and +1.6 percentage points per kg ha−1 (a protein/oil exchange ratio of −1.6). A seed protein, oil, and yield QTL mapped close to RAPD marker OPAW13a in a small LG‐I interval that was flanked by the SSR markers Satt496 and Satt239. The additive effects of the PI 437088A allele on seed protein, oil, and yield were a respective +1.0 and −0.6 percentage points (a protein/oil ratio of −1.6) and −154 kg ha−1 Given that the genetic‐based protein/oil exchange ratio of 1.6 is smaller than the 2.0 calorific‐based oil/protein ratio, one might expect the remaining 0.4 units of carbon and/or energy to be made available for other seed dry matter. However, yield almost invariably falls when seed protein is genetically enhanced at the expense of seed oil, suggesting that protein synthesis and its deposition in the seed is energetically more costly to the plant than is commonly assumed.
Ecogeography of Annual Wild Cicer Species
Authors: Berger Jens , Abbo Shahal , Turner Neil C.
Published: July 2010

The annual wild Cicer species are becoming increasingly important to the cultigen (Cicer arietinum L.) as a source of genetic diversity, and resistance to both biotic and abiotic stresses. The objectives of this study were to consolidate and review the current status of the world collection of annual wild Cicer species and the closely related perennial, C. anatolicum Alef. The world collection is very limited. Although 572 entries are held in nine genebanks around the world, only 287 are separate accessions, the rest represent duplicated material. However, only 124 accessions (43%) were collected independently from wild populations, the remaining 163 represent selections from the original material. These 124 original accessions are not evenly distributed between species. There is only a single original accession of C. cuneatum Hochst ex. Rich, two of C. chorassanicum (Bunge) Popov, three of C. yamashitae Kitamura, eight of C. anatolicum, 10 of C. echinospermum P. H. Davis, 18 of C. reticulatum Ladzinsky, 20 of C. bijugum Rechinger, 28 of C. pinnatifidum Jaubert & Spach, and 34 of C. judaicum Boissier. Principal components analysis was used to summarize the habitat characteristics of the annual wild Cicer collection sites in terms of geography and climate, and compare these with the range of habitats recorded for the species in regional floras. With few exceptions, the range of habitats sampled in ex situ collections is far smaller than that covered by the species' distribution in the wild. As a consequence of low original accession number, and narrow collection site distribution, the world collection represents only a fraction of the potential diversity available in wild populations. We suggest that targeted collection missions based on ecogeographic principles are imperative.
Photoperiod‐Insensitive Japanese Soybean Landraces Differ at Two Maturity Loci
Authors: Abe Jun , Xu Donghe , Miyano Akane , Komatsu Kunihiko , Kanazawa Akira , Shimamoto Yoshiya
Published: July 2010

Insensitivity of flowering to long daylengths is an important character in the adaptation of soybean [Glycine max (L.) Merrill] to higher latitudinal environments. The objective of this study was to identify and map the maturity genes for incandescent long daylength (ILD) insensitivity for two landraces, ‘Miharudaizu’ and ‘Sakamotowase’, which belong to different cultivar groups. Two F9 recombinant inbred line (RIL) families were developed by means of a repetitive heterozygote selection method from the F2 population of the cross between the two landraces. Linkage analyses with isozyme and simple sequence repeat (SSR) markers revealed that the maturity gene for ILD insensitivity from Miharudaizu was a recessive allele at the E4 locus on Molecular linkage group (MLG) I. The MLG I order of the E4 locus and four markers was determined as Satt239–Satt496–E4–Enp–Satt354. The maturity gene for ILD insensitivity from Sakamotowase was found to cosegregate with four tightly linked SSRs on MLG C2, and was determined as a recessive allele at the E1 locus. The genotypes at the E3 locus for both Miharudaizu and Sakamotowase were estimated as e3e3 on the basis of the responses of late‐flowering near‐isogenic lines to fluorescent long daylength (FLD). The results obtained in this study suggest that Miharudaizu has the genotype of E1E1e3e3e4e4 and Sakamotowase has the genotype of e1e1e3e3E4E4 Because the e1 allele cannot induce flowering in ILD in the presence of the E4 allele, an unknown gene may condition the ILD insensitivity of Sakamotowase, possibly while combined with the e1 allele.
Seed Source Effect on Field Emergence of Soybean Lines with Reduced Phytate and Raffinose Saccharides
Authors: Meis Shane J. , Fehr Walter R. , Schnebly Steven R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] lines homozygous for the mips allele (mips lines) have reduced phytate P and raffinose saccharides in the protein meal. Less phytate is desirable for reducing the P content of manure from nonruminant animals and less raffinose saccharides increases the amount of metabolizable energy available to them. Field trials indicated that seedling emergence percentage of mips lines was less for seed produced in a subtropical environment than a temperate environment. The objective of this study was to determine if field emergence of mips lines is influenced by the environment used for seed production. Seed of six mips lines and four commercial cultivars (Mips lines) produced in four temperate and 12 subtropical environments during 2 yr was evaluated for field emergence percentage, seed viability percentage, and germination percentage in warm germination, cold vigor, and accelerated aging tests. The field emergence percentage of mips lines was significantly less than Mips lines for all seed sources. The mips lines had a mean field emergence of 63% for temperate sources and 8% for subtropical sources while Mips lines had a mean field emergence of 77% for temperate sources and 83% for subtropical sources. The mean seed viability percentage for the mips lines based on the tetrazolium test of 88% for temperate sources and 70% for subtropical sources accounted for only part of the differences in field emergence. Differences in field emergence between the mips and Mips lines were not consistently predicted by the warm germination and cold vigor tests for temperate sources. The accelerated aging test effectively differentiated the field emergence potential of the mips and Mips lines for all seed sources. Seed source should be a consideration when evaluating the field emergence of mips lines in a breeding program or for obtaining acceptable plant populations in commercial fields.
Relationships between Leaf‐Blade Nitrogen and Relative Seedcotton Yields
Authors: Bell Paul F. , Boquet D. J. , Millhollon E. , Moore S. , Ebelhar W. , Mitchell C. C. , Varco J. , Funderburg E. R. , Kennedy C. , Breitenbeck G. A. , Craig C. , Holman M. , Baker W. , McConnell J. S.
Published: July 2010

Nitrogen fertilization is a required production practice for cotton (Gossypium hirsutum L.) with risks arising from under‐ and over‐fertilization. Tissue testing for diagnosing N deficiencies in crops can use leaf blades and the total N concentration, but this practice has not been rigorously examined in cotton. The primary objective of these experiments was to determine the leaf‐N concentration of the uppermost, fully mature leaf blade below which yield loss could be expected. Nitrogen‐rate field experiments were conducted at 12 research station and farm sites in the Midsouth USA in Louisiana, Arkansas, Mississippi, and Alabama in 1996 and 1997. Leaf‐blade total N concentrations associated with yield loss were 4.3% N at early bloom (R2 = 0.50) and 4.1% N at mid‐bloom (3 wk after early bloom, R2 = 0.32). The likelihood of applying N when not needed could be reduced by lowering the early bloom critical value to 3.9%. Only 4% of all samples sufficient in N would have been incorrectly diagnosed N deficient at that critical value, but 44% of all deficient samples would have been misidentified as N sufficient. Reduced yields due to over application of N were evident in some samples with leaf N between 4.6 and 4.8% at early bloom. These concentrations were also common for N‐sufficient plants, making accurate diagnoses of the over application of N unlikely. Our leaf‐N critical values probably differ from previously established values because earlier values were derived via survey techniques and because faster fruiting cultivars may require higher leaf N.
Genetic Diversity in Diploid Cultivars of Rhodesgrass Determined on the Basis of Amplified Fragment Length Polymorphism Markers
Authors: Ubi Benjamin Ewa , Kölliker Roland , Fujimori Masahiro , Komatsu Toshinori
Published: July 2010

Rhodesgrass (Chloris gayana Kunth) is a highly variable, perennial forage grass widely cultivated in all tropical and subtropical regions of the world. Despite its economic importance, there is a lack of information on the genetic diversity within and among rhodesgrass cultivars, which are all based on genetic resources initially introduced from East and South Africa. The objective of this study was to assess genetic diversity within and among 13 cultivars of diploid rhodesgrass and to determine whether recent breeding efforts have resulted in cultivars distinct from the African source populations. For each cultivar, 15 individuals were examined for 237 amplified fragment length polymorphism (AFLP) markers generated from three EcoRI/MseI primer pairs. Partition of the variation revealed that the major proportion of the total genetic variation occurred within cultivars and with only 12 to 13% attributed to geographical origin or breeding history. Cluster analysis revealed three distinct groups among the cultivars investigated. Group one consisted mainly of recent Japanese cultivars and their African source population, group two contained mostly African cultivars, and group three contained one African cultivar. However, the genetic diversity within recent Japanese cultivars was comparable to the diversity within old African cultivars and there was no evidence of a reduced genetic base because of breeding efforts.
Characterization of Rose Clover Germplasm for Flowering Traits
Authors: Nunes M. E. S. , Smith G. R.
Published: July 2010

Rose clover (Trifolium hirtum All) cultivars with long‐season (November through May) forage production and cold tolerance are needed to increase pasture availability during the winter in northeast Texas. More information about the genetic and environmental control of rose clover flowering is warranted, before this trait can be manipulated through plant breeding. The objective of this study was to evaluate the variability for flowering traits in the U.S. Plant Introduction Collection of rose clover. Sixty‐six accessions of rose clover, from eight different countries, were evaluated. Observations recorded on individual plants at 4‐d intervals included first elongation of internodes, first bud, first flower, first color, full bloom, and mature seed. In general, rose clover behaved as a long‐day plant and flowered in photoperiods from 12 to 14h. Thirty‐one rose clover lines were identified within the maturity range of 172 to 182 days of the year (DOY) to full bloom, twenty‐seven were identified within the maturity range of 162 to 170 DOY to full bloom, only five rose clover lines reached full bloom in less than 162 DOY, and only three took more than 183 DOY. There was a range of 40 d difference in time to reach maturity for the rose clover germplasm studied. Utilizing principal component analysis and cluster analysis, the germplasm was separated into three different maturing groups: early, midseason, and late maturity groups.
Elevated Temperature and Carbon Dioxide Effects on Soybean Seed Composition and Transcript Abundance
Authors: Thomas J. M. G. , Boote K. J. , Allen L. H. , Gallo‐Meagher M. , Davis J. M.
Published: July 2010

Climate change due to increased [CO2] and elevated temperature may impact the composition of crop seed. This study was conducted to determine the potential effects of climate change on composition and gene expression of soybean [Glycine max (L.) Merr. cv. ‘Bragg’] seed. Soybean plants were grown in sunlit, controlled environment chambers under diel, sinusoidal temperatures of 28/18, 32/22, 36/26, 40/30, and 44/34°C (day/night, maximum/minimum), and two levels of [CO2], 350 and 700 μmol mol−1, imposed during the entire life cycle. The effect of temperature on mature seed composition and transcripts in developing seed was pronounced, but there was no effect of [CO2]. Total oil concentration was highest at 32/22°C and decreased with further increase in temperature. Oleic acid concentration increased with increasing temperature whereas linolenic acid decreased. Concentrations of N and P increased with temperature to 40/30°C, then decreased. Total nonstructural carbohydrates (TNC) decreased as temperatures increased, and the proportion of soluble sugars to starch decreased. Transcripts of a gene that is downregulated by auxin (ADR12) were dramatically downregulated by elevated temperature, possibly reflecting the altered course of seed development under environmental stress. Transcripts of β‐glucosidase, a gene expressed during normal soybean seed development, were detected in seed grown at 28/18°C but not in seed grown at 40/30°C, which also suggests that normal programs affecting seed composition were perturbed by elevated temperature. These results confirm previous studies indicating that high temperature alters soybean seed composition, and suggest possible mechanisms by which climate change may affect soybean seed development and composition.
Challenges in Testing Transgenic and Nontransgenic Cotton Cultivars
Authors: May O. L. , Bourland F. M. , Nichols R. L.
Published: July 2010

Cotton (Gossypium hirsutum L.) cultivars transgenically enhanced to impart herbicide resistance to either bromoxynil [3,5‐dibromo‐4‐hydroxybenzonitrile; BXN (Bayer Advanced, Peoria, IL)] or glyphosate [N‐(phosphonomethyl)‐glycine; Roundup Ready (Monsanto Co., St. Louis, MO)], and/or Bacillus thuringiensis var. kurstaki [Bt; Bollgard (Monsanto)] mediated resistance to certain lepidopteran insects were planted to 77% of the 2002 U.S. cotton hectarage, yet Official Cultivar Trial (OCT) protocols remain little changed since inception. The presence of transgenic, pest‐managing, and nontransgenic cultivars in OCTs poses challenges to provide unbiased cultivar performance because OCTs impose herbicide and insect management regimes appropriate for nontransgenic cultivars. Our objectives were to assess the merits of OCTs to test transgenic and nontransgenic cultivars and to recommend alternatives. Because OCTs levy common pest management on all cultivars, value‐added transgenic traits are not demonstrated, cultivar variation in their expression is not shown, and main effects and interaction of cultivar and pest management regime are confounded. Examples of pest management main effects that potentially affect cultivar ranks in OCTs include yield penalties imposed on herbicide‐resistant cultivars from routinely used, soil‐applied herbicides and yield advantages imparted to Bt cultivars from added insect control of OCT insecticide regimes. One recommendation to more comprehensively test cultivars is to augment OCTs with trials wherein the best performing transgenic and nontransgenic cultivars in OCTs are produced with their respective pest management programs. Such trials simultaneously evaluate cultivars and transgenic traits for yield, fiber quality, and economic returns. Still, bias imposed by nontransgenic pest management regimes in OCTs can only be quantified through trials levying transgenic and OCT‐type pest management treatments on transgenic cultivars.
Associations among Twenty Years of International Bread Wheat Yield Evaluation Environments
Authors: Trethowan R. M. , van Ginkel M. , Ammar K. , Crossa J. , Payne T. S. , Cukadar B. , Rajaram S. , Hernandez E.
Published: July 2010

Understanding the way different environments differentiate cultivars for yield allows the plant breeder to optimize choice of parents, germplasm screening, yield testing, and resource use within the target region. To determine the associations among yield testing environments, wheat (Triticum aestivum L.) yield data from 963 replicated trials sown across a 20‐yr period were analyzed by means of pattern analysis and the shifted multiplicative model (SHMM) to group sites within and across years. Pattern analysis identified four primary clusters of sites and four representative locations within these clusters were identified by squared Euclidean distances. Group‐1 represented primarily Mediterranean and West Asian locations and South American sites. Group‐2 was comprised of generally warmer sites in southern and eastern Asia. Group‐3 comprised higher rainfall locations in South America and eastern Africa and Group‐4 represented cooler sites in South America and West Asia. The respective key locations for each of the four groups were Sakha, Egypt; Quezaltenango, Guatemala; Londrina, Brazil; and Pirsabak, Pakistan. The four key sites were then used to examine site clusters within each year by SHMM. The sites at Pirsabak and Sakha associated best across all global wheat‐growing regions where a combined total of 700 of 1117 (62%) possible clusters with other global wheat locations were realized. This compared with 52% for Quezaltenango and 38% for Londrina. Factors with a primary influence on site clustering were cropping season moisture availability and temperature. Genotype performance at Pirsabak and Sakha can be used to enhance genetic progress in a range of related wheat growing environments thereby improving the effectiveness of global wheat breeding.