bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing High‐Protein, High‐Yield Soybean Populations and Lines
Authors: Cober E. R. , D Voldeng H.
Published: July 2010

Developing high‐yielding, high‐protein soybean [Glycine max (L.) Merr.] lines is difficult because of the inverse relationship between seed yield and seed protein content. The objective of this study was to evaluate single cross and rapid back cross breeding methods to achieve both high seed yield and high protein content. ‘AC Proteus’ was used as the high‐protein source and ‘Maple Glen’ was used as the adapted high‐yielding parent. Six single plants were randomly selected from each of 149 F3 progeny rows to develop 886 single cross derived lines. Reciprocal back cross populations were made using 60 F1 plants from the single cross and the high‐yielding parent, Maple Glen. Ten single plant selections were randomly taken from each of 80 F1‐derived families to develop 800 back cross derived lines. In 1994, all lines were tested in the field. About 20% of lines were retained for testing through this breeding project from 1994 to 1996 although selection intensity differed across populations and years. In 1997, six single cross and nine back cross lines were tested at six locations in Eastern Canada. The seed yield and protein content of the single cross lines were not significantly different from the back cross derived lines. All the selected lines had higher seed protein content than did Maple Glen. Both breeding strategies produced lines with significantly higher seed protein content than Maple Glen. However, none of these lines had significantly higher seed yield than Maple Glen or a recently released high protein cultivar, AC Proteina. These populations exhibited a very low or no association between seed yield and protein (r = −0.06 to −0.21). Therefore, the parents may be useful sources of alleles which do not exhibit the usual pleiotrophic effect of low seed yield and high seed protein. The use of a back cross to the adapted parent following the single cross was not beneficial in the development of high yielding lines.
Hypertriploid in Soybean: Origin, Identification, Cytology, and Breeding Behavior
Authors: Xu S. J. , Singh R. J. , Kollipara K. P. , Hymowitz T.
Published: July 2010

Autotriploids (2n = 3x) are an excellent source of producing primary trisomics and have been produced in a majority of diploid plant species. A spontaneous hypertriploid (2n = 3x + 1 = 61) in soybean [Glycine max (L.) Merr., 2n = 2x = 40] was isolated for the first time from the progeny of the cross between soybean line T31 and a primary trisomic line T190‐47‐3. This line could provide a means for producing primary trisomics in soybean. The objective of this study was to report the origin, general plant morphology, cytology, fertility, and breeding behavior of a hypertriploid. The hypertriploid and a disomic sib were planted in the greenhouse for comparing general morphology. Root tips (mitotic metaphase) and flower buds (meiotic Metaphase I and Anaphase I) were used for cytological studies, and pollen grains and seed set were evaluated for fertility. Crosses with ‘Clark 63’ and selfed population were used to evaluate breeding behavior. Results revealed that the hypertriploid expressed more vigorous vegetative growth than the corresponding disomic sibling. At Metaphase I, an average meiotic chromosome pairing was 0.10 IV + 11.18 III + 9.43 II + 8.23 I, indicating that the four homologous chromosomes mainly formed two bivalents. The hypertriploid showed 63% pollen fertility and produced 98 seeds from self‐pollination. Chromosome numbers in the selfed population of the hypertriploid ranged from 2n = 50 to 2n = 69. However, the chromosome number in F1 plants from the cross of hypertriploid × Clark 63 ranged from 2n = 44 to 2n = 48 with an exception of one plant that contained 2n = 56 chromosomes. Some plants with 2n = 44 to 2n = 47 had high seed fertility. The progenies of these aneuploid lines will segregate mostly into plants with 2n = 41 chromosomes. This study suggests that soybean male and female spores tolerate a higher number of extra chromosomes than most true diploid plant species, corroborating the hypothesis that soybean is a diploidized polyploid species.
Inheritance of Resistance to Stem Rust in Medea Durum Wheat and the Role of Suppressors
Authors: Knott D. R.
Published: July 2010

The durum wheat (Triticum turgidum L.) cultivar Medea Ap9d has been used as a supplementary differential in the identification of isolates of stem rust (Puccinia graminis f. sp. tritici Eriks. & Henn.). Genes for stem rust resistance from Medea were transferred to a susceptible hexaploid wheat (T. aestivum L.), LMPG, so that they could be used more efficiently in race identification and wheat breeding. Medea was backcrossed five times to LMPG with selection for resistance to stem rust races LBB and MCC. Ten near‐isogenic lines (NILS) were produced and tested with isolates of 10 stem rust races. The NILs fell into four types. Three of the four types had resistance to races to which Medea was susceptible. Apparently, Medea possesses suppressors for some of its genes for resistance and the suppressors were lost during the backcrossing to LMPG. This was confirmed when the cross, Medea/Glossy Hugenot, and the backcross, Medea/2 × Glossy Hugenot, segregated for resistance to races RCH and TMH(15B‐4), to which both parents are susceptible. The segregations could not be explained on the basis of complementary genes. Medea was also crossed and backcrossed to a susceptible durum, Glossy Hugenot, for a genetic study using races MCC and TMB. The genetic analysis showed that Medea has four genes that condition resistance to races MCC, two of which also condition resistance to race TMB. None of the four types of NILs are resistant to both. Apparently, neither of the latter genes was transferred to LMPG. The presence of suppressors in Medea suggests that they may confer a selective advantage on plants that carry them.
Genotypic and Environmental Variation in Soybean Seed Cell Wall Polysaccharides
Authors: Stombaugh S.K. , Jung H.G. , Orf J.H. , Somers D.A.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed cell wall polysaccharides (CWP) have been characterized, but little is known about their genotypic variation. This information would be beneficial for determining genetic strategies for manipulating CWP content and composition. Seed CWP was determined by the Uppsala total dietary fiber method to quantify monosaccharides of CWP in 14 soybean genotypes from Maturity Groups 00 to I grown at four Minnesota locations. CWP concentration of mature whole seed varied from 158 to 176 g/kg dry matter (DM). Genotypic but not environmental effects were significant for total CWP concentration. For individual monosaccharide concentrations, both genotypic and environmental effects were present. Seed of five genotypes were separated into cotyledon and seed coat for CWP analysis. Genotypic variation for CWP concentration was mostly in cotyledon and not seed coat. Pectin was mostly in cotyledon rather than seed coat with 80.8 and 14.6 g pectin/kg of whole seed DM in cotyledon and seed coat, respectively. Only xylose, glucose, galactose, and uronic acid concentrations were significantly different among genotypes in cotyledon. The correlation between CWP concentration and protein plus oil concentration among the 14 genotypes was r = −0.724, which suggests that an increase in protein plus oil content is associated with a reduction of CWP concentration. The genotypic variation observed suggests that it is possible to breed for reduced CWP. However, genotypic variation for some monosaccharides was limited, suggesting that other methods of genetic manipulation may be more efficient in reducing these monosaccharides.
Nitrogen Use Efficiency and Morphological Characteristics of Timothy Populations Selected for Low and High Forage Nitrogen Concentrations
Authors: Brégard A. , Bélanger G. , Michaud R.
Published: July 2010

Improving timothy (Phleum pratense L.) N use efficiency (NUE) through genetic selection aims at producing greater or similar forage dry matter (DM) yields with less N fertilizer while maintaining N concentration close to the optimal level required for ruminant nutrition. Two populations of timothy, arising from divergent selection for high (N+) and low (N−) forage N concentration, and a reference population, ‘Champ’, were studied under controlled conditions with N rates of 1, 5, 10, and 20 mg N plant−1 wk−1 The populations N− and Champ produced more forage DM yield than N+. This difference in forage production was the result of changes in biomass partitioning between shoots and roots because, at the whole plant level, no differences in total biomass (shoots + roots) were found. On the basis of total biomass, there were no population differences in NUE and N accumulation efficiency (NAE). For a given level of forage DM yield, N+ had a greater N accumulation than N− and Champ and, therefore, a greater N concentration. The greater forage N concentration of N+ was not due to a greater leaf N concentration but to a greater proportion of leaves. The population N+ also had a greater proportion of roots than N−. The forage insoluble N concentration of N+ was greater than that of N−, while NO3–N concentrations of the populations were similar. The population N+ had a greater tiller density and specific leaf area (SLA) than N−. Differences in forage DM yield and N concentration between two populations selected for low and high N concentrations were mainly due to the modification of C and N partitioning between shoots and roots, and between leaves and stems. Our results highlight the role of biomass partitioning in improving grass NUE or N concentration.
Spray Chamber Evaluation of Air‐Assisted Spraying on Broccoli
Authors: Panneton Bernard , Philion Hubert , Thériault Roger , Khelifi Mohamed
Published: July 2010

Conventional over‐the‐row sprayers achieve very little deposit on leaves near the ground and on the underside surfaces of leaves throughout the canopy. Air assistance has the potential to improve deposition of droplets on these leaf surfaces. To gain some insight on the effect of air assistance, the effects of airspeed, airflow rate, and air jet orientation were isolated. The study was carried out in a spray chamber with a standard spray boom over micro‐plots of greenhouse grown broccoli (Brassica oleracea var. botrytis L.) plants. Air was delivered slightly behind the nozzles from a variable width slot producing a uniform two‐dimensional air jet. The orientation of the air jet with respect to the vertical could be adjusted from −10 to 40°. The ranges of the independent variables were airspeed, 0 to 36 m s−1; airflow rate, 0 to 1.3 m3 s−1 m−1, and air jet angle, −10.2 to 40.2°. Two sets of flat fan nozzles (Volume Median Diameter = 230 and 400 μm, both delivering 250 L ha−1 at 6 km h−1) were used to carry out two full sets of experiments. Results showed that airspeed had the larger impact on leaf coverage. Higher airspeeds (>25 m s−1) and airflow coupled with finer sprays increased the coverage of the underside of the leaves at all levels within the canopy and of the top side of the leaves in the lower third of the canopy. However, lower airspeeds (<20 m s−1) are desirable for a better coverage of the upper side of the leaves in the higher two‐thirds of the canopy. In all cases, angling the air jet forward at 20 to 25° is recommended.
Relationship between Laboratory Seed Quality Tests and Field Emergence of Common Bean Seed
Authors: Kolasinska Krystyna , Szyrmer Jerzy , Dul Stefania
Published: July 2010

In cool climates, early planting of bean (Phaseolis vulgaris L.) is recommended to assure a longer vegetative growth period. Early planting exposes seed to unfavorable conditions and the commonly used standard germination test cannot predict field emergence. The objective of this work was to examine the relationships between various seed quality tests and field emergence of common bean seeds. Thirty‐nine strains and cultivars of bean were tested in the field and laboratory over 3 yr. Each year seed samples were tested in the laboratory and then planted in the field at very early, early, and at optimal planting dates. The viability of seeds was test by tetrazolium staining and was generally high; standard germination was above 80%, but germination in the cool test (at 10°C) varied from 0 to 99%. The percentage of seeds with broken coats varied from 0.5 to 50.3 and conductivity ranged from 7 to 45 μS cm−1 g−1. Field emergence varied from 0 to 100%. Soil temperature at sowing appeared to be not only the most important environmental factor influencing field emergence but also a factor able to be used to differentiate the field emergence potential of a seed lot. Only the conductivity test could be used to predict seedling emergence in the field irrespective of soil temperature at sowing. At temperatures ranging from 9 to 15°C, the first and the last count of the standard germination test and the broken seed coat test should be used in conjunction with the conductivity test to estimate field emergence potential.
Salinity Effects on Zoysiagrass Cultivars and Experimental Lines
Authors: Qian Y. L. , Engelke M. C. , Foster M. J. V.
Published: July 2010

Salt tolerant turfgrasses are highly desirable in areas associated with saline soils and/or saline irrigation waters. To determine the salt tolerance of 29 zoysiagrass (Zoysia spp.) experimental lines and cultivars, two greenhouse studies were conducted by means of a hydroponic culture system. Sodium chloride was gradually added to a basic nutrient solution to obtain a final salinity level of 42.5 dS m−1 Relative salt injury, indicated by leaf firing percentage, was associated with zoysiagrass leaf length and texture. Short, fine leaf‐textured zoysiagrass (‘Diamond’, DALZ8501, and their hybrids) were most salt tolerant, coarse leaf‐textured entries (Z. japonica Steud. and their hybrids) intermediate, whereas long, fine leaf‐textured entries (‘Cavalier’, ‘Emerald’, and ‘Zeon’) exhibited the least salt tolerance. Salinity resulted in decreased K+ and increased Na+ in shoots of all cultivars. Sodium content was significantly correlated with percentage of leaf firing, with Zeon, Emerald, ‘DeAnza’, Cavalier, and TAES4377 having the highest concentration of Na+, and TAES4357, TAES4361, and TAES4373 the lowest concentration. Most hybrids with Diamond and DALZ8501 as parents exhibited good to intermediate salinity tolerance. The broad sense heritability was 0.67, 0.50, 0.41, 0.54, and 0.40 for relative leaf firing, shoot and root growth, and Na+ and K+ content, respectively. Results suggest that genetic progress may be made to develop salt tolerant zoysiagrass with conventional breeding techniques.
Tissue Production and Quality of ‘Tifway’ Bermudagrass as Affected by Seasonal Application Patterns of Trinexapac‐Ethyl
Authors: Fagerness M. J. , Yelverton F. H.
Published: July 2010

Research on the gibberellic acid (GA)–inhibiting plant‐growth regulator (PGR) trinexapac‐ethyl (TE) regarding seasonal effects of single vs. multiple applications of this product on turfgrass quality and tissue production has not been reported. Research was conducted at North Carolina State University on ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis (Burtt‐Davy)] to compare effects of different seasonal application patterns of TE. Applications of TE were made to fully established Tifway bermudagrass at either 0.107 or 0.071 kg a.i. ha−1 Seasonal application patterns included an initial application, followed by zero, one, or two sequential applications at 4‐wk intervals. Plots were rated weekly for turfgrass quality and clippings were collected weekly for evaluation of tissue production. Results demonstrated that one application of TE provided temporary growth inhibition of Tifway bermudagrass. This effect, as expected, disappeared 4 wk after initial treatment (WAIT). Post‐inhibition growth enhancement (PIGE) was observed from 6 to 10 WAIT in areas treated with a single application of TE at 0.071 kg a.i. ha−1 However, total seasonal tissue production following a single application of TE was equal to untreated areas, suggesting limited overall effects of PIGE. Conversely, one or two sequential applications of TE provided prolonged growth inhibition; total seasonal tissue production was reduced by up to 40%. Overall quality of Tifway bermudagrass was enhanced by multiple TE applications and perceived fall dormancy was delayed. Results support the use of sequential applications of TE in Tifway bermudagrass for consistent growth management throughout the growing season, avoidance of PIGE, and improvement in visual turfgrass quality.
Positioning the wp Flower Color Locus on the Soybean Genome Map
Authors: Hegstad J. M. , Tarter J. A. , Vodkin L. O. , Nickell C. D.
Published: July 2010

The wp allele generates a pink flowered phenotype in soybean [Glycine max (L.) Merr.]. Genotypes with W1_wp wp are associated with larger seed size and higher seed protein content. The influence of a single locus on the anthocyanin pathway and seed protein accumulation has not been documented in other species. It is of interest to clone wp by initially identifying linked molecular markers. The objective of this research was to use restriction fragment length polymorphism (RFLP) and simple sequence repeat (SSR) molecular markers to position the wp locus on the soybean public genetic map. Of the 74 markers tested, two RFLP and 14 SSR markers were identified as linked to wp The two RFLP markers linked to wp in this study were previously reported to be associated with quantitative trait loci (QTL) controlling seed protein in a G. soja Siebold & Zucc. × G. max population. It is proposed that wp is located between RFLP locus K011 and SSR locus Satt600. The molecular markers linked to wp were located on linkage group D1b+W of the public soybean genetic map. The knowledge of linked molecular markers will assist in cloning wp, potentially leading to further characterization of how wp influences the anthocyanin pathway and seed protein accumulation.
Seed Production of White Clover Cultivars and Naturalized Populations when Grown in a Pasture
Authors: Pederson G. A. , Brink G. E.
Published: July 2010

Small‐type white clover, Trifolium repens L., plants predominate in most closely grazed pastures in the southeastern USA. The role of relative seed production in stand persistence of white clover types in pastures has not been quantified. This study compared the relative seed production of seven small‐type naturalized populations with that of seven large‐type white clover cultivars and germplasms in a pasture. All entries were space‐planted into plots in a common bermudagrass [Cynodon dactylon (L.) Pers.] pasture at Mississippi State, MS, on a Savannah fine sandy loam (fine‐loamy, siliceous, semiactive, thermic Typic Fragiudult) in fall 1995 and 1996, and grazed with cattle prior to flowering and seed production. All naturalized populations averaged about three times as many flowers and seed‐bearing flowers as all cultivars other than ‘Louisiana S‐1’ each year. Flower production differences were consistent throughout the study, though maximum flower production for naturalized populations was earlier in the season than cultivars. Seed production differences were similar to flower production, as cultivars averaged only 27 to 43% as much seed as naturalized populations. The low growth stature and excessive seed production of naturalized populations enable them to tolerate close continuous grazing and have a greater opportunity to reseed in pastures than common large‐type cultivars. This reseeding potential probably contributes to the domination of small‐type white clover in closely grazed pastures of the southeastern USA.
Level and Geographical Distribution of Resistance to Meloidogyne arenaria in the U.S. Peanut Germplasm Collection
Authors: Holbrook C. Corley , Stephenson Michael G. , Johnson A. William
Published: July 2010

The peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] causes significant economic losses in many peanut (Arachis hypogaea L.) production areas of the world. The objectives of this study were (i) to examine the peanut core collection to identify sources of resistance, (ii) to estimate the level of resistance that occurs in the U.S. germplasm collection, and (iii) to examine the geographical distribution for resistance in peanut germplasm. Seven hundred forty‐one accessions from the core collection were tested in greenhouse trials. The egg‐mass rating for cultivar Florunner, the susceptible check, was 4.0 on a 1.0 to 5.0 scale with a nematode reproduction rate of 15 496 eggs per gram of fresh root weight. Fifty‐six accessions exhibited an egg‐mass rating of ≤2.5. Thirty‐six core accessions showed a reduction in root galling, egg‐mass rating, egg count per root system, and egg count per gram of root in comparison to Florunner. Twenty‐one accessions showed a 70% reduction in egg count per root system and per gram of root, and two accessions showed a 90% reduction of these variables in comparison with Florunner. The 56 resistant indicators from screening the core collection identified 39 clusters in the entire germplasm collection that should be examined more thoroughly. China and Japan appear to be valuable geographical sources for resistance to this nematode.
Response of Six Alfalfa Populations to Selection under Laboratory Conditions for Germination and Seedling Vigor at Low Temperatures
Authors: Klos Kathy L. E. , Brummer E. Charles
Published: July 2010

Alfalfa (Medicago sativa L.) seeded in early spring often germinates and emerges under cold temperatures. We conducted this study to determine if phenotypic recurrent selection improved germination time and seedling growth under cool temperatures in the laboratory. Four selection methods were conducted in the laboratory for two cycles within six commercial alfalfa cultivars: 5454, Alfagraze, Amerigraze 401+Z, Innovator +Z, Magnum IV, and WL252HQ ranging in fall dormancy class from two to four. Cycles 0, 1, and 2 were evaluated in controlled environmental chambers. Two cycles of selection for rapid germination at 5°C decreased germination time (GT) by 29%. Response to selection was greatest in the first cycle. Two cycles of selection for high seedling vigor increased seedling height (SH) after 45 d at 10°C by 15%. In some cultivars, selection for high seedling vigor was effective at increasing SH in the laboratory and further increases may be expected. Selection for high seedling vigor increased GT, indicating an association between these traits under laboratory conditions. The mean realized heritability estimates were 0.49 for GT and 0.18 for SH. Selection for both early germination and high seedling vigor resulted in an average decrease in GT of 29% with no effect on SH after two cycles, but combined selection against both traits increased GT by 162% and decreased SH by 18%. Laboratory selection for decreased GT and increased SH under low temperatures can be successful, but the amount of improvement is population dependant.
Salinity Effects on Seedling Growth and Yield Components of Rice
Authors: Zeng Linghe , Shannon Michael C.
Published: July 2010

Flood irrigation practices that are commonly used in California during the early stages of rice (Oryza sativa L.) establishment may contribute to salinity damage and eventually decrease yield. Knowledge of salinity effects on rice seedling growth and yield components would improve management practices in fields and increase our understanding of salt tolerance mechanisms in rice. Salinity sensitivity of rice was studied to determine salinity effects on seedlings and yield components. Plants of rice cultivar M‐202 were grown in a greenhouse in sand and irrigated with nutrient solutions of control and treatments amended with NaCl and CaCl2 (2:1 molar concentration) at 1.9, 3.4, 4.5, 6.1, 7.9, and 11.5 dS m−1 electrical conductivity. Shoot dry weights of seedlings were measured at five harvests in the first month after seeding. Seedling growth was significantly reduced by salinity at the lowest salinity treatment, 1.9 dS m−1. At 1.9 and 3.4 dS m−1, significant reduction of seedling growth occurred at longer cumulative thermal time than at higher salt levels. Seedling survival was significantly reduced when salinity was 3.40 dS m−1 and higher. Highly significant linear responses of grain weight per plant, grain weight per panicle, spikelet number per panicle, and tiller number per plant to salinity were observed. There was a common lowest salt level for fertility and pollen germination beyond which they were significantly reduced by salinity. Harvest index was significantly decreased when salinity was at 3.40 dS m−1 and higher. Tiller number per plant and spikelet number per panicle contributed the most variation in grain weight per plant under salinity. Reductions in seedling survival, tiller number per plant, and spikelet number per panicle were the major causes of yield loss in M‐202 under salinity. The compensation between spikelets and other yield components was confounded with salinity effects, but was believed to be minor relative to the reduction of spikelets due to salinity and, therefore, not sufficient to offset yield loss even at moderate salt levels.
Repeatability and Genotype × Environment Interaction of Coleoptile Length Measurements in Winter Wheat
Authors: Hakizimana Frederic , Haley Scott D. , Turnipseed E. Brent
Published: July 2010

Coleoptile length is often associated with fall stand establishment in winter wheat (Triticum aestivum L.). While coleoptile length evaluation and improvement is a common objective of wheat breeding programs, little information is presently available to guide effective evaluation efforts. The objectives of this study were to assess the association between kernel and test weight and coleoptile length, to determine the inherent precision of a coleoptile length screening procedure through repeatability analysis, and to assess the presence and nature of genotype x environment (G × E) interaction for coleoptile length. Seed samples from 45 winter wheat genotypes planted in a randomized complete block design at four locations in the 1994‐1995 growing season were used to evaluate G × E interaction. A subset of samples of 15 lines from two contrasting environments (Selby, high kernel and test weight; Winner, low kernel and test weight) were used to estimate repeatability (R) from five repeated measurements of the same seed sample. Analysis of variance revealed highly significant (P < 0.01) G × E interactions for coleoptile length measurements from seed samples from the four locations. Spearman rank correlations between genotype means at the four environments were highly significant , suggesting that G × E interactions were caused by differences in scale among environments and not by differences in genotype rankings among environments. Estimates of repeatability of coleoptile length measurements were high and not significantly different between samples from the two contrasting environments (Selby: ; Winner: ). Our results suggest that coleoptile length is a moderately heritable trait and that seed source for coleoptile length measurements has little or no effect on coleoptile length expression or the variation experienced with the evaluation procedures.
Light Interception Efficiency and Light Quality Affect Yield Compensation of Soybean at Low Plant Populations
Authors: Board Jim
Published: July 2010

Greater understanding of how soybean [Glycine max (L.) Merr.] yield compensation occurs across plant populations would aid research aimed at reducing optimal plant population. Objectives were to determine how net assimilation rate (NAR) and leaf area index (LAI) contribute to crop growth rate (CGR) equilibration across low, medium, and high plant populations during the vegetative (emergence–R1) and early reproductive periods (R1–R5). Determinate cultivar Delta Pine 3606 (Maturity Group VI) was planted at an optimal planting date during 1995 and 1996 at low (80000 plants ha−1), medium (145000 plants ha−1), and high (390000 plants ha−1) plant populations on a Commerce silt loam near Baton Rouge, LA (30°N). Yield was unaffected by plant population. Equilibration of CGR for low vs. higher plant populations near R1 was achieved through greater NAR for the low plant population during the vegetative period, created by greater light interception efficiency (LIE, light interception per unit leaf area). Although NAR equilibrated to minimal levels across plant populations near R1, low population maintained CGR parity with higher populations until R5 through greater relative leaf area expansion rate (RLAER) during the late vegetative and early reproductive periods. Higher relative leaf area expansion rate for low vs. higher plant populations resulted from increased partitioning of dry matter into branches, probably induced by greater red/far red light ratios within the canopy. In conclusion, a possible genetic characteristic conducive to low optimal plant population is greater partitioning of dry matter into branches.
Mechanisms of Wear Tolerance in Seashore Paspalum and Bermudagrass
Authors: Trenholm L. E. , Carrow R. N. , Duncan R. R.
Published: July 2010

Traffic causes shoot injury to turfgrass, with resulting inhibition of growth and reduction of quality. Turfgrasses in high traffic venues are generally selected for tolerance to traffic or for an ability to quickly outgrow the injury. However, limited knowledge exists on the mechanisms that impart wear tolerance to turfgrass, particularly for warm‐season grasses. This field research was undertaken to assess overall wear tolerance within and between seashore paspalum (Paspalum vaginatum Swartz.) ecotypes and bermudagrass hybrids (Cynodon dactylon L. × C. transvaalensis Burtt‐Davy) and to determine the mechanisms that contribute to wear tolerance for both species. The research was conducted in two consecutive field trials during 1997 on seven seashore paspalum ecotypes and three hybrid bermudagrass cultivars established on a native Appling (fine, kaolinitic, thermic Typic Kanhapludult) soil at the University of Georgia Experiment Station in Griffin, GA. Regression analysis determined that the most important potential mechanism related to enhanced wear tolerance of seashore paspalum was reduced leaf total cell wall (TCW) content, which accounted for 51% of the variation. Other factors that enhanced wear tolerance in this species were low leaf strength, low stem TCW, greater leaf moisture, greater shoot density, and higher K shoot tissue concentration. In bermudagrass, high stem moisture (40.9% of variation) and reduced stem cellulose content (31.5% of variation) were associated with better wear tolerance. Other factors that enhanced wear tolerance were greater stem and leaf moisture, shoot density, leaf lignin, stem and leaf lignocellulose, and concentration of K, Mn, and Mg. Knowledge of these characteristics will assist in developing screening protocols for selection of future wear tolerance cultivars within these species.
Growth and Physiological Responses of Creeping Bentgrass to Changes in Air and Soil Temperatures
Authors: Xu Qingzhang , Huang Bingru
Published: July 2010

High air or soil temperature is a major factor limiting growth of cool‐season grasses during summer months in the transition zone and warm climate regions. Knowledge of how cool‐season grasses respond to differential high air and soil temperatures would facilitate our understanding of heat tolerance mechanisms. The objectives of this study were to compare the influence of air versus soil temperature on turf quality, physiological activities, and root growth of creeping bentgrass (Agrostis palustris Huds. cv. Penncross), and to investigate whether shoot and root growth could be improved by reducing soil temperature at high air temperatures. Shoots and roots were exposed to four air/soil temperature regimes (20/20, 20/35, 35/20, and 35/35°C) for 56 d in growth chambers. High soil (20/35°C) and high air/soil (35/35°C) temperatures reduced canopy photosynthetic rate (Pn), turf quality, and the number of roots. High air/soil temperatures also reduced photochemical efficiency (Fv/Fm). The adverse effects of high air/soil temperatures were more pronounced than either high soil or air temperature alone for turf quality, Fv/Fm, Pn, and root growth. High soil temperature was more detrimental than high air temperature. Lowering soil temperature at high air temperatures (35/20°C) increased root growth, canopy Pn, Fv/Fm, and turf quality, compared with high soil temperature at low or high air temperatures (20/35 and 35/35°C). The results demonstrated that roots mediated shoot responses to high temperature stress in creeping bentgrass, and that reducing root‐zone temperature could help maintain quality creeping bentgrass under supraoptimal ambient temperatures.
AFLP Analysis of DNA from Dried Hop Cones
Authors: Townsend M. Shaun , Henning John A. , Moore Daniel L.
Published: July 2010

Hop (Humulus lupulus L.) cones are used extensively in beer brewing to enhance flavor and impart bittering. Verifying hops cultivar identity has traditionally been accomplished by morphological characteristics or a chemical analysis of lupulin glands but these traits may vary according to environmental influences. The objective of this research was to develop an AFLP (amplified fragment length polymorphism) protocol for analyzing DNA extracted from dried hop cones. The DNA was extracted from dried cones of six hop genotypes by a technique published for grapes (Vitis spp). The reagents, MseI primers, and protocol were part of a commercially available kit, while the 6‐carboxyfluorescein‐labeled EcoRI primers were purchased separately. Eleven primer combinations amplified an average of 546.5 scorable fragments with an average of 49.7 fragments per primer combination. All genotypes were differentiated with the primer combinations studied. Average genetic similarity estimates ranged between 0.956 and 0.995 among the six hop genotypes studied. This research provides the hops industry with a powerful technique to verify accurately hops cultivar identity and purity through an analysis of dried cone DNA.
Mapping Genetic Factors Associated with Winter Hardiness, Fall Growth, and Freezing Injury in Autotetraploid Alfalfa
Authors: Brouwer Douglas J. , Duke Stanley H. , Osborn Thomas C.
Published: July 2010

Winter hardiness is a complex trait and one of the most important adaptations for alfalfa (Medicago sativa L.) grown in northern climates. In the absence of winter hardiness data, alfalfa breeders predict the potential of genotypes with component traits related to winter hardiness. This research was undertaken to identify and compare some of the genomic regions that control winter injury (WI) and two component traits, fall growth (FG) and freezing injury (FI). Two plants, B17 and P13, representing the extremes for each trait were crossed, and a F1 plant was backcrossed to each parent to create two populations of 101 individuals each. Each population was scored for 82 single dose restriction fragment loci, and 17 or 19 two‐allele loci and evaluated for FG, FI, and WI in 2 yr of replicated field trials. Trait measures over the 2 yr were significantly correlated (r = 0.71, r = 0.42, and r = 0.76 for FG, FI, and WI, respectively). Significant correlations also existed between WI and FG (r = 0.50 and 0.56) and FI (r = 0.34 and 0.58) for each year. One to six single dose restriction fragment were significant factors in multiple regression models that explained 6.3 to 52.2% of the phenotypic variation for each trait in each year and the average of 2 yr. More of the phenotypic variation was explained in the backcross to B17 (the winter hardy, fall dormant parent) than in the backcross to P13 (the winter sensitive, non‐fall dormant parent) and for FG than for FI and WI. Partial dominance was detected for P13 alleles at most loci associated with FG and for B17 at loci associated with FI. Additive gene action predominated for loci associated with WI. Severe winter kill and the association of FG with plant vigor may have masked identification of quantitative trait loci (QTL) in the P13 backcross. In the B17 backcross, genomic regions that contain QTL affecting FG, FI, and WI were identified on linkage groups 5 and 8, but QTL affecting only FG and FI were identified on linkage groups 1 and 3. These data indicate that there is a genetic basis for the use of predictor traits in the absence of winter hardiness data. However, they also suggest that genetic components of fall dormancy and winter hardiness can be manipulated independently, and they reveal regions that may be useful for marker‐assisted selection with this material.
Marker‐Based Selection of QTL Affecting Grain and Malt Quality in Two‐Row Barley
Authors: Igartua E. , Edney M. , Rossnagel B. G. , Spaner D. , Legge W. G. , Scoles G. J. , Eckstein P. E. , Penner G. A. , Tinker N. A. , Briggs K. G. , Falk D. E. , Mather D. E.
Published: July 2010

Malt quality traits of barley (Hordeum vulgare L.) may be suitable candidates for marker‐assisted selection, as their evaluation involves laborious and costly procedures. Four regions of the genome were previously reported to affect several grain and malt quality traits in the two‐row barley cross ‘Harrington’/‘TR306’. This study used an independent set of lines derived from the same cross to verify the existence of quantitative trait loci (QTL) in these regions. Molecular marker genotypes were used to select 47 lines from among 410 Harrington/TR306 lines that had not been used in the original mapping experiment. Four groups of lines were selected on the basis of their genotype at marker loci in two regions on chromosome 7 (5H) with QTL affecting kernel weight and plumpness, grain protein, extract β‐glucan content, the difference between fine‐grind and coarse‐grind extract, soluble protein, diastatic power, α‐amylase activity and fine‐grind extract, and in regions on chromosomes 3 (3H) and 6 (6H) with QTL affecting extract β‐glucan content and fine‐coarse difference. Grain and malt quality traits of these lines were determined from grain grown in five field environments in western Canada. The results confirmed the presence of QTL on chromosome 7 affecting all traits previously reported. Marker‐based selection for two regions on chromosome 7 was effective in identifying phenotypically superior lines, and the magnitudes of the combined effects for these regions were close to the estimates calculated in the mapping experiment. The presence of QTL on chromosomes 3 and 6 could not be confirmed as categorically, but combined selection for extract β‐glucan content and fine‐coarse difference at all four QTL regions was more effective than selection for only the two regions on chromosome 7.
Analysis of a Quantitative Trait Locus Allele from Wild Soybean That Increases Seed Protein Concentration in Soybean
Authors: Sebolt A. M. , Shoemaker R. C. , Diers B. W.
Published: July 2010

Increases in the seed protein concentration of soybean [Glycine max (L.) Merr.] would improve the value of the crop. Two major quantitative trait locus (QTL) alleles from Glycine soja Sieb. and Zucc. that increased seed protein concentration were identified previously. The first objective of our study was to test the two G. soja QTL alleles in a population developed through backcrossing the alleles into a soybean background. The second objective was to evaluate the effect of one of the G. soja QTL alleles in three genetic backgrounds. A backcross three (BC3) population was developed and evaluated in the field across two locations over 2 yr. To test the allele in different backgrounds, a line from the backcross population was crossed to three soybean genotypes. Populations developed from these crosses were then evaluated in three field environments. In the backcross population, genetic marker alleles linked to the QTL allele from G. soja on linkage group (LG) I were significantly (P < 0.05) associated with greater protein and less oil concentration, reduced yield, smaller seeds, taller plants, and earlier maturity than the G. max alleles. Markers linked to the second G. soja QTL allele on LG E were not significantly associated with seed or agronomic traits. In the genetic background tests, markers linked to the G. soja QTL allele on LG I were associated with an increase in protein concentration in two of the three crosses. These results show that seed component traits can be successfully modified through genetic mapping coupled with marker assisted selection.
Genetic Base of 651 Chinese Soybean Cultivars Released during 1923 to 1995
Authors: Cui Zhanglin , Carter Thomas E. , Burton Joseph W.
Published: July 2010

A diverse genetic base is important to breeding progress. The genetic base of U.S. and Canadian (US‐CAN) soybean [Glycine max (L.) Merr.] cultivars is narrow. Modern Chinese soybean cultivars have been cited as a reservoir of genetic diversity for U.S. breeding. However, the genetic base of Chinese soybean cultivars is not well characterized. The purpose of this paper was to quantify the genetic base of Chinese soybean breeding by means of coefficient of parentage (CP) analysis and to compare it with that of US‐CAN soybean. Three hundred thirty‐nine ancestors were identified in the pedigrees of 651 Chinese soybean cultivars released during 1923–1995. Ancestors originating from China contributed 88% of the genes to the Chinese genetic base, and 45 exotic ancestors contributed 12%, as determined by CP analysis. Comparison of Chinese and US‐CAN bases showed that (i) the genetic base of Chinese soybean breeding was much larger than that of the US‐CAN and (ii) the Chinese base has continued to expand with time while the US‐CAN base has changed little. Analysis showed that 35 and 339 ancestors contributed 50 and 90% of the genes to Chinese soybean cultivars, while only five and 26 ancestors contributed similar amounts to the US‐CAN base. The three major soybean growing regions in China, Northeastern (NEC), Northern (NC) and Southern (SC) had little soybean ancestry in common with each other and constituted almost independent genetic bases. Each of the major Chinese growing regions had more ancestors and a more uniform distribution of ancestral contributions than did the total US‐CAN breeding effort. Although the genetic base of both Chinese and U.S. soybeans are dominated by Chinese landraces, no landraces were identified by name as common to both. In recent decades, 24 U.S. cultivars and lines have been bred to Chinese stock. These U.S. materials now constitute 7.3% of the genetic base for Chinese cultivars and have led to important yield advances in China. In contrast, U.S. breeding has made little use of Chinese cultivars. By virtue of their broad genetic base and isolation from U.S. cultivars, modern Chinese soybean cultivars are potentially important to U.S. breeding programs.
Cross Species Inoculation of Chewings and Strong Creeping Red Fescues with Fungal Endophytes
Authors: Johnson‐Cicalese J. , Secks M. E. , Lam C. K. , Meyer W. A. , Murphy J. A. , Belanger F. C.
Published: July 2010

An effective technique was developed to inoculate mature Chewings fescue [Festuca rubra L. subsp. fallax (Thuill) Nyman] and strong creeping red fescue (Festuca rubra L. subsp. rubra) tillers with fungal endophytes (Epichloe festucae Leuchtm., Schardl, & Siegel and Neotyphodium spp.). Six fine fescue genotypes were successfully inoculated with endophytes originating from fine fescues and Poa ampla Merr. Eleven percent of the tillers were successfully inoculated, and all inoculated plants transmitted the endophytes to their offspring. This set of inoculated plants, with various combinations of genotypes and endophyte strains, allowed us to compare the effects of different endophytes on one host, and one endophyte on several hosts. When evaluated in the field, the growth characteristics of these plants were dependent on endophyte and host genotype. Considerable interaction between the genotypes was seen. For example, one host inoculated with the Poa ampla endophyte showed enhanced performance, while another host inoculated with the same endophyte performed poorly.
Inheritance of Grain Mold Resistance in Grain Sorghum without a Pigmented Testa
Authors: Rodriguez-Herrera R. , Rooney W. L. , Rosenow D. T. , Frederiksen R. A.
Published: July 2010

The improvement of grain mold resistance in sorghum [Sorghum bicolor (L.) Moench] has been difficult, presumably because of the complex inheritance of the trait. The objective of this study was to determine the inheritance of grain mold resistance by generation means analysis. The F1, F2, and backcross generations of a cross between `Sureño' (a dual‐purpose food grain and forage variety, resistant to grain mold) and `RTx430' (a widely adapted inbred line, highly susceptible to grain mold) were evaluated in eight different field environments. Significant differences in grain mold incidence between the generations evaluated in this study were observed in all environments. Combined analysis detected a significant generation five‐environment interaction indicating that the genotypes reacted differently to each environment. Generation means analysis of transformed grain mold scores detected additive effects in all eight environments, and dominance effects were detected in seven of eight environments. Epistatic effects were detected in only two of eight environments, but combined analysis indicated that higher order interactions were important when evaluated across environment. Broad‐sense heritability estimates ranged from 0.46 to 0.82, while narrow‐sense heritability estimates ranged from 0.39 to 0.59. At least four to 10 genes were estimated to contribute to grain mold resistance. The results of this study indicate that selection in specific environments is useful for enhancing resistance to mold in these environments, but it may not be as effective in providing grain mold resistance across a wide range of environments.
Isolation of High Seed Inorganic P, Low‐Phytate Soybean Mutants
Authors: Wilcox James R. , Premachandra Gnanasiri S. , Young Kevin A. , Raboy Victor
Published: July 2010

Phosphorous in soybean [Glycine max (L.) Merr.] seed is stored primarily as phytic acid, which is nutritionally unavailable to nonruminant livestock. The objective of this study was to isolate mutations that reduce soybean seed phytic acid P and increase seed inorganic P. Following treatment with ethyl methanesulfonate, M2 through M6 plants were screened for high seed inorganic P. Seeds of M2 plants high in inorganic P produced progenies high in inorganic P through the M6 generation. M6 progenies of one plant averaged 6.84 g kg−1 seed phytic acid and inorganic P varied from 2.34 to 4.41 g kg−1 or 60 to 66% of phytic acid P plus inorganic P. M6 progenies of a second plant averaged 10.89 g kg−1 phytic acid and varied from 1.21 to 3.84 g kg−1 inorganic P, representing from 47 to 51% of the sum of phytic acid P plus inorganic P. In contrast, nonmutant seeds of the check cultivar Athow contained 15.33 g kg−1 phytic acid and averaged 0.74 g kg−1 inorganic P, representing 15% of the sum of phytic acid P plus inorganic P. Low phytic acid and high inorganic P in these progenies should increase the nutritional value of soy meal and reduce excess P in livestock manure.