bluuebunny/crossref_metadata_2025 huggingface dataset:
Assignment of the Y17 Locus to Classical Soybean Linkage Group 14
Authors: Devine T. E.
Published: July 2010

The classical genetic map of soybean [Glycine max (L.) Merr.] remains at a primitive stage of development relative to the map of other crops. This study was undertaken to augment the information base needed for a more comprehensive classical map. The cultivar Minsoy, which carries the dominant allele Pb that conditions a sharp pubescence tip, was crossed to the genetic type T162, which carries the recessive allele yl7 that conditions chlorotic foliage. The F2 seedlings were classified for sharp vs. blunt pubescence tip and green vs. chlorotic foliage. the chi‐square for linkage partitioned from the total chi‐square was significant and recombination value of 27% was calculated for the y17 and pb loci. Because a recombination value of 27% had previously been reported for pb and the y9 gene, which also conditions foliar chlorosis, an allelism test was conducted to test for the allelism of y17 and y9 by hybridizing genetic type T135, which carries the recessive allele y9, with T162, which carries the recessive allele y17. The F1 hybrids had normal green foliage indicating that y17 and y9 were separate loci. To determine whether y9 and y17 were on the same side or opposite sides of the Pb locus, the F2 of the T135 ✕ T162 cross was tested with chi‐square for fit to a 9:7 ratio or a 1:1 ratio for green:chlorotic foliage. The F2 segregation data fit the 1:1 ratio indicating that the Y17 and Y9 loci were both on the same of the Pb and in close proximity.
A High Leaf‐Starch Mutant in Alfalfa Has Altered Invertase Activity
Authors: Das Shankar B. , Bowley Stephen R. , McKersie Bryan D.
Published: July 2010

A mutant phenotype isolated from alfalfa (Medicago sativa L) cv. Excalibur appeared to have dramatic changes in source‐sink relations and the partitioning of carbohydrates. Leaves emerged normally, but starch accumulatedin the chloroplasts of the palisade mesophyll cells with maturity. Subsequently the cells of the palisade layer lost chlorophyll, exhibited ultrastructural symptoms of senescence, and necrotic spotting appeared on the adaxiai surface of fully expanded leaves. Segregation analysis of this phenotype, designated as hls (high‐leaf starch), with F1, BC1, and F2 progenies revealed that two independent dominant genes condition the trait. The hls phenotype had five‐fold more starch in mature leaves and less in the taproot than in the normal leaf phenotypes, suggesting a blockage in transport of carbohydrate from the leaf to the root. In vitro activity assays and native polyacrylamide gel electrophoresis (PAGE) analysis revealed that most enzymes involved in carbohydrate metabolism were not altered in the hls phenotype. However, invertase activity of expanding leaves was significantly higher in plants with the hls phenotype than in those with a normal phenotype. The visual appearance of the mutation, high leaf starch content, and high invertase activity co‐segregated in the progeny. Native PAGE revealed that a fast‐moving invertase isozyme (F) was developmentally inactivated in normal phenotypes during leaf expansion but remained active in the hls phenotype. A biochemical model for the hls phenotype is proposed in which high invertase activity blocks phloem loading and reduces the availability of cytosolic inorganic orthophosphate for exchange with triose‐phosphate across the chloroplast envelope, thereby promoting starch accumulation.
Variation in Water‐Use Efficiency and Its Relation to Carbon Isotope Ratio in Cotton
Authors: Saranga Yehoshua , Flash Igal , Yakir Dan
Published: July 2010

Cotton (Gossypium spp.) is often exposed to drought, which adversely affects both yield and quality. Improved water‐use efficiency (WUE = total dry matter produced or yield harvested / water used) is expected to reduce these adverse effects. Genetic variability in WUE and its association with photosynthetic rate and carbon isotope ratio (13C/12C) in cotton are reported in this paper. WUE of six cotton cuitivars—G. hirsutum L., G. barbadense L., and an interspecific FI hybrid (G. hirsutum ✕ G. barbadense, ISH), was examined under two irrigation regimes in two field trials. The greatest WUE was obtained by two G. hirsutum cultivars (2.55 g dry matter or 1.12 g seed‐cotton L−1 H2O); the ISH obtained similar or somewhat lower values, and two G. barbadense cultivars and one G. hirsutum cultivar exhibited the lowest values (2.1 g dry matter or 0.8 to 0.85 g seedcotton L−1H2O). These results indicate that different cotton cultivars may have evolved different environmental adaptations that affect their WUE. Photosynthetic rate was correlated with WUE in only a few cases, emphasizing the limitation of this parameter as a basis for estimating crop WUE. Under both trials, WUE was positively correlated with carbon isotope ratio, indicating the potential of this technique as a selection criterion for improving cotton WUE
Effect of Burrs vs. Caryopses and Planting Date on Establishment of Seeded Buffalograss in the Southern Great Plains
Authors: Gaitán‐Gaitán Fernando , McKenney Cynthia B. , Auld Dick L.
Published: July 2010

Successful establishment of buffalograss [Bucholë dactyloides (Nutt.) Engelm.] by seed is the greatest limitation of this native species as a turfgrass. There has been limited research to determine the impact of planting date and use of untreated burrs vs. caryopses on establishment in the semiarid environments of the Southern Great Plains. During the 1992,1993, and 1994 growing seasons, buffalograss was established by seed at 2‐wk intervals from mid‐May to mid‐ September at the Texas Tech Univ. Plant Stress Lab. in Lubbock, TX. The test site was located on an Amarillo fine, sandy soil (fineloamy, mixed, thermic Aridic Paleustalf). Seedling emergence at 2 and 4 wk after planting, and stand density and turf quality at the end of the growing season were used as indices of stand establishment. The cultivars Texoka and Comanche differed only slightly in stand establishment and final turfgrass quality ratings in these studies. Caryopses had an average of 34 and 28% higher seedling establishment than burrs at 2 and 4 wk after planting, respectively. The improved establishment of caryopses was significant in 1992 and 1994. Neither caryopses nor burrs produced good quality turf by the end of the growing season when planted after mid‐July (Day of the Year 193–197). Based on these studies, both commercial turfgrass growers and homeowners in the Southern Great Plains should be encouraged to plant buffalograss caryopses in the late spring or early summer to ensure successful establishment of high quality turf.
Genetic Variation and Predicted Gain from Selection for Winterhardiness and Turf Quality in a Perenial Ryegrass Topcross Population
Authors: Waldron B. L. , Ehlke N. J. , Wyse D. L. , Vellekson D. J.
Published: July 2010

Improved winterhardiness in turf‐type perennial ryegrass (Lolium perenne L.) could expand its area of adaptation for turf and seed production, but breeding efforts have been hindered in part by a lack of identifiable winter‐hardy germplasm. This research was conducted to estimate genetic variation for winterhardiness in a perennial ryegrass topcross population and to determine the feasibility of simultaneously improving turf quality and winter field survival. ‘NK‐200’, a perennial ryegrass cultivar with acceptable winterhardiness in northern Minnesota, was topcrossed to a large sample of improved turftype cultivars and 243 of the resulting half‐sib families were selected for evaluation. Genetic variances, correlations, and predicted gain from single and multiple trait selection were stimated for winterhardiness and turf quality characteristics of half‐sib progeny evaluated at two Minnesota locations in 1994 and 1995. Significant additive genetic variation and moderate narrow‐sense heritability estimates were obtained for winterhardiness (σ2A = 0.64 ± 0.11;h2 =0.59 ± 0.10). Fiftyfive half‐sib families had higher or equivalent winterhardiness than NK‐200 suggesting transgressive segregation. Significant additive genetic variation was found for turf quality, crown rust (Puccinia coronata Corda) resistance, and leaf texture, but turf quality and leaf texture were undesirably correlated with winterhardiness (rA = −0.15 and −0.25, respectively). Gain from selection estimates revealed that single trait selection could rapidly improve winterhardiness and turf quality. However, some form of multiple trait selection would be necessary to improve winterhardiness and turf quality traits simultaneously. These results indicate that the potential exists to develop improved
Genetic Variation for Biomass and Residue Production in Lentil: I. Relation to Agronomic Traits
Authors: Kusmenoglu Ismail , Muehlbauer Fred J.
Published: July 2010

Sufficient crop residues on soil surfaces are needed for protection from water and wind erosion in the U.S. Pacific Northwest. The lentil (Lens culinaris Medik.) crop grown in this region lacks sufficient crop residues which leads to severe soil erosion in subsequent crops. The objectives of this study were (i) determine the relationship between physiological and morphological traits that affect biomass and residue production, and (ii) identify suitable selection criteria for increasing biomass and residue production by lentil crops. Thirty nine breeding lines were evaluated at three sites each year from 1993 to 1995. Straw yield in 1993 was correlated with days to flower (r = 0.72**), days to maturity (r = 0.82**), plant height (r = 0.76**), harvest index (r = −0.97**), and seed yield (r = −0.71**). In addition there were significant correlations between straw yield and harvest index (r = −0.48**) in 1995, and between straw yield and seed yield (r = 0.59**) in 1994. The regression coefficient (b) indicated that for each day that flowering and maturity were delayed, there were increases of 214 kg/ha and 734 kg/ha straw yield, respectively. A 1 cm increase in plant height resulted in a 277 kg/ha increase in straw yield. Results indicated that plant height could be used for indirect selection for increased biomass. Seed yield can also be improved by selecting for larger vegetative biomass while keeping harvest index constant.
14C‐Trinexapac‐Ethyl Absorption and Translocation in Kentucky Bluegrass
Authors: Fagerness Matthew James , Penner Donald
Published: July 2010

Trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethyle ster] is a foliar‐applied growth regulator for turfgrass that can reduce mowing frequency, clipping production, and enhance turfgrass color. 14C‐Trinexapac‐ethyl was used to evaluate absorption and subsequent 14C‐trinexapac‐ethyl translocation in hydroponically grown ‘Blacksburg’ Kentucky bluegrass (Poa pratensis L.). The magnitude and rate of 14C trinexapacethyl absorption by various organs was as follows: plant base > leaf blade > roots. Plant base, as a morphological description and site of application, refers to the collection of leaf sheaths surrounding the compressed turfgrass stem and the crown of the plant. Over the time period of 0 to 24 h, maximum absorption by the plant base was obtained in 8 h and by the leaf blade in 24 h. Absorption by the roots was negligible. Addition of an activator organosilicone abjuvant, Sylgard 309, significantly enhanced 14C‐trinexapac‐ethyl absorption by the leaf blade 1 h after application but did not enhance absorption by the plant base. Of the 14C‐trinexapac‐ethyl absorbed dy the plant base, over 50% was translocated to the plant foliage after 24 h. Of the 14C‐trinexapac‐ethyl absorbed by the leaf blade, one‐third was translocated after 24 h; the direction of movement was predominantly basipetal.Less than 5% of absorbed 14C‐trinexapac‐ethyl from either site was translocated to roots or to rhizomes with daughter plants, explaining the lack of inhibition of lateral turfgrass growth. Combined effects of enhanced leaf blade absorption, basipetal translocation from the leaf blade, and acropetal translocation from the plant base of 14C‐trinexapac‐ethyl helped explain the positive impact of Sylgard 309 on efficacy and rainfastness of trinexapac‐ethyl.
Spray Application Parameters That Influence the Growth Inhibiting Effects of Trinexapac‐Ethyl
Authors: Fagerness Matthew James , Penner Donald
Published: July 2010

Trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethyle ster] is a foliar absorbed, cyclohexanedione turfgrass growth regulator that can inhibit shoot growth in numerous turfgrass species. However, observed antagonisms, based on spray application parameters for other cyclohexanedione agrichemicals are a cause for concern in achieving maximum efficacy. Greenhouse studies were conducted with trinexapac‐ethyl investigate the effects of adjuvants, hard water, rainfastness, photolability, and spray carrier volume on efficacy such that efficacy might be maximized. Results were compared to those obtained with the cyclohexanedione herbicide, sethoxydim [2‐[1‐ethyoxyimino)butyl]‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one], to illustrate any similarities in observed antagonism patterns. Studies with Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), creeping bentgrass (Agrostis palustris Huds.), and tall fescue (Festuca arundinacea Schreb.) showed that the adjuvant combination of Sylgard 309 plus 28% (w/v) urea ammonium nitrate (UAN) could significantly enhance the efficacy of trinexapac‐ethyl when applied at or below 0.382 kg ha−1. Ammonium sulfate compensated for reductions in both trinexapac‐ethyl and sethoxydim activity on perennial ryegrass when hard water was the carrier. Ammonium sulfate increased the rainfastness of trinexapac‐ethyl on perennial ryegrass to greater extent than did Sylgard 309 while the rainfastness of sethoxydim was only increased with Sylgard 309. Photolability of formulated trinexapac‐ethyl on perennial ryegrass was not observed to be a liability. Increasing spray carrier volume did not significantly influence the efficacy of trinexapac‐ethyl on perennial ryegrass, although efficacy enhancements observed with additions of ammonium sulfate were only apparent at low volumes. the impact of ammonium salts on trinexapac‐ethyl activity has a broad range of implications for applications of this growth regulator.
Selecting Kentucky Bluegrass Cultivars
Authors: Voigt T. B. , Fermanian T. W. , Sullivan W. C.
Published: July 2010

A computer‐aided learning process has been previously developed to identify unique turfgrass cultivar performance levels under specific growing conditions. However, it was not determined if this process was similar to the routine assessments made by turfgrass experts. A survey was sent to 191 turfgrass experts to determine turf cultivar recommendation consistency, to validate a set of computer developed rules of association, and to determine the environmental and management characteristics the experts considered most influential on turfgrass cultivar performance. Seventy completed surveys, mostly from respondents who had worked professionally for at least 10 yr at Land Grant universities, were returned. In the first section of the survey, experts showed a high degree of consistency in recommending Kentucky bluegrass (Poa pratensis L.) cultivars for specific settings. In the second section of the survey, there was inconsistent agreement among survey respondents and machine learning output when presented with rules associating cultivar performance and turf settings. Finally, when asked to indicate which environment or management parameters experts felt most influence performance of specific Kentucky bluegrass cultivars, survey respondents selected mowing height, nitrogen fertilization levels, and irrigation. The computer‐aided learning process also identified mowing height and nitrogen fertilization levels as influencing cultivar performance. The machine learning process also selected soil pH and average monthly air temperature as influential. Thus, there was not overall agreement between survey respondents and machine learning output.
Degradability of Cell‐Wall Polysaccharides in Maize Internodes during Stalk Development
Authors: Jung H. G. , Morrison T. A. , Buxton D. R.
Published: July 2010

Limitations to degradation of forage cell‐wall constituents in maturing plant tissue are not fully understood, which limits progress in developing cultivars with improved digestibility. We determined in vitro degradability of cell‐wall components by rumen microorganisms in developing internodes of maize (Zea mays L.). Plants were grown in the growth chamber and harvested at the 15th‐leaf stage of development. Individual internodes were divided in half and separated into rind and pith fractions. Cell‐wall degradability was measured on the internode samples and correlated with cell‐wall degradability. Degradability of all cell‐wall polysaccharide components, except galactose and mannose, declined with maturation of maize internodes. Degradabilities of glucose and xylose residues exhibited large differences between 24‐ and 96‐h fermentation intervals (31 to 58% additional degradation in 72 h), whereas the arabinose and uronic acids potentially degradable in 96 h were already almost completely degraded in 24 h. Maize rind, consisting of epidermal and sclerenchyma tissues and many vascular bundles, was less degradable than the pith (736 vs. 811 g kg‐−1, respectively), which had thinner‐walled parenchyma tissue and fewer vascular bundles. Lower portions of internodes were younger and more degradable than the upper halves (805 vs. 743 g kg−1, respectively). Ferulate ether concentration was negatively correlated with cell‐wall polysaccharide degradability in young, elongating internodes but not for internodes in which elongation had ceased to occur. This pattern is in agreement with the hypothesis that ferulate cross‐linking limits cell‐wall degradation, but that the effect is only observable in young tissues before dilution of ferulate ether concentrations by secondary wall deposition of lignin and polysaccharides obscures the relationship.
Molecular and Biochemical Characterization of a Non‐Robertsonian Wheat‐Rye Chromosome Translocation Line
Authors: Wang Erming , Xing Hongyan , Wen Yuxiang , Zhou Wenjuan , Wei Rongxuan , Han Hu
Published: July 2010

A non‐Robertsonian wheat‐rye chromosome translocation was observed in pollen‐derived line WER‐I‐1 from the FI hybrid between M27 [a 1R(1D) substitution line] and ‘Chinese Spring’. Biochemical assays of high molecular weight glutenin subunits and gliadin components and Southern hybridization of dispersed rye repeat sequences pSc 119.2 and pSc 5.3H3 provided sufficient evidence that in WER‐1‐1, wheat chromosome pair ID was substituted by 1R chromosome pair. C‐banding and genomic in situ hybridization further revealed that the 1R chromosomes, present in WER‐I‐1, were abnormal in that the distal parts of their long arms were lost and translocated to the long arm ends of a pair of wheat chromosomes. The mode of origin of this transiocation is also discussed.
Testcross Evaluation of Soybean Germplasm
Authors: Lewers K. S. , St. Martin S. K. , Hedges B. R. , Palmer R. G.
Published: July 2010

The F1 generation of a testcross previously was not used to evaluate soybean [Glycine max (L.) Merr.] germplasm, primarily because production of large amounts of hybrid seed has been impractical and because evaluation of quantitative traits with one or a few plants does not give reproducible results. Recently, a method for efficiently producing testcross seed was developed by using the male sterility locus, Ms6, and a genetically linked seedling marker locus, W1. The objectives of this research were (i) estimation and comparison heterosis and inbreeding depression values for agronomic traits of testcross lines; and (it) determination of the utility of per se and testcross evaluation for selecting germplasm to be included in an existing cultivar development program. Two testers were used to evaluate six lines in three‐row plots. Significant F1 and F2 midparent heterosis and inbreeding depression were observed for nearly all traits, including grain yield. The choice of tester was ascertained to be important in determining parental value of germplasm. Parental lines were evaluated by using a combination of per se performance, heterosis values, and a recently developed testcross statistic, Ti. The Ti value was better than F1 midparent heterosis for identifying lines suitable for use in direct crosses. F1 midparent heterosis was better than the Ti value for identifying valuable lines requiring pre‐breeding effort. A combination of F1 and F2 midparent heterosis values identified lines likely to have genes with dominance effects; although, because of inbreeding depression, use of F2 heterosis alone failed to identify valuable lines.
Shoot Physiological Responses of Two Bentgrass Cultivars to High Temperature and Poor Soil Aeration
Authors: Huang Bingru , Liu Xiaozhong , Fry Jack D.
Published: July 2010

Understanding the effects of high temperature and poor soil aeration and their interaction on growth and physiology of creeping bentgrass (Agrostis palustris Huds.) will help management and breeding programs to improve summer turf quality. The objective of this study was designed to examine shoot physiological responses of ‘Crenshaw’ and ‘Penncross’ to high temperature and poor soil aeration. Turf was maintained in growth chambers at day/night temperatures of 22/15°C (optimum) or 35/25°C (high temperature, HT). Soil aeration treatments were (i) adequate aeration with oxygen diffusion rate (ODR) at 1.5 μg cm−2 min−1 by maintaining the soil medium well watered and well drained and (ii) low aeration (LA) with ODR below 0.2 μg cm−2 min−1 induced by flooding the soil medium. Turf growth, quality, chlorophyll content (Chl), and net photosynthetic rate (Pn) declined with increasing temperatures or declining aeration for both Crenshaw and Penncross. The HT treatment increased canopy minus air temperatures (ΔT) and dark respiration rates (Rn) for both cultivars, with a greater rise in Rn for Penncross (44%) than for Crenshaw( 25%). The LA treatment inhibited Rn but had no effect on ΔT. The combination of HT and LA had more severe adverse effects than either HT or LA alone on turf quality, leaf chlorophyll content, photosynthesis, and respiration, particularly for Penncross. The results demonstrated genetic variations in shoot physiological responses to high temperature and poor soil aeration stresses in creeping bentgrass and indicated that high temperature, when combined with poor soil aeration lead to turf quality decline. This was mainly due to reduced net photosynthesis and increased respiration rates.
Histochemical, Physiological, and Ultrastructural Changes in the Maize Embryo during Artificial Drying
Authors: Perdomo Antonio , Burris Joseph S.
Published: July 2010

When drying high moisture(450–500 g H2O kg−1 fw) Zea mays L. seeds, a preconditioning period of drying at low temperatures(PC) may prevent injury due to subsequent high temperature drying. We preconditioned maize seeds under four different environments(35°C / 35% RH, 35°C / 90% RH, 20°C / 35% RH, and 20°C / 90% RH) and determined the level of seed deterioration in terms of reserve stability, enzyme activity, respiration, and ultrastructural changes in the radicle meristem. During PC, respiration rates were significantly higher for the 35°C than the 20°C treatments; however, overall respiration during PC was considerably lower than during germination. After 48 h of PC, amylase activity was present in all of the PC treatments with the highest levels and additional isozymes in the 35°C / 90% RH treatment. This treatment was also the only one in which we found degradation of starch grains in the histochemical analysis. During PC, transmission electron micrographs revealed migration of lipid bodies toward the cell wall and formation of protein bodies within vacuoles. Both of these processes were more likely to appear in those treatments that allowed higher rates of desiccation or in which the seeds were more mature (Harvest 2). Mitochondrial cristae were well differentiated with no evident impairment of their integrity in any of the PC treatments. Better seed quality was obtained when seed were preconditioned at moderate (35°C) temperature and low (35%) relative humidity. We conclude from these results that the positive effects of preconditioning may occur as a balance between metabolic and morphological processes resulting in high temperature desiccation tolerance, while minimizing the negative impact of the catabolic events such as degradation of starch grains and higher respiration rates.
The NIa‐Proteinase of Different Plant Potyviruses Provides Specific Resistance to Viral Infection
Authors: Fellers John P. , Collins Glenn B. , Hunt Arthur G.
Published: July 2010

The genome‐linked protein‐proteinase (NIa) genes of three potyviruses (tobacco vein mottling virus[TVMV], tobacco etch virus[TEV], and potato virus Y [PVY]) were introduced into tobacco (Nicotiana tabacum L.) cultivar Burley 21 and transgenic plant lines were evaluated for viral symptoms and virus accumulation. Plant lines that expressed the TVMV NIa gene were resistant to infection by TVMV; inoculated plants did not develop disease symptoms after inoculation, and virus did not accumulate. Most lines that carried the TEV NIa and PVY NIa genes did develop symptoms after inoculation with TEV and PVY, respectively, but these symptoms abated with time (a response termed as recovery). Three genes, each consisting of two NIa coding regions (TEV NIa‐PVY NIa, TEV NIa‐TVMV NIa, and TVMV NIa‐PVY NIa) were also introduced into Burley 21. Transgenic lines that carried either TEV NIa‐PVY NIa or TEV NIa‐TVMV NIa constructs either did not develop disease symptoms or exhibited the process of recovery after inoculation with TEV. TEV NIa‐TVMV NIa and TVMV NIa‐PVY NIa lines recovered from an initial infection after inoculation with TVMVL. Likewise, TEV NIa‐PVY NIa and TVMV NIa‐PVY NIa transformed lines recovered from an initial infection after inoculation with PVY. These results demonstrate that different potyvirus NIa‐proteinase genes can be used for protection against virus infection and that multiple NIa genes may be used to produce plants that are protected against more than one potyvirus.
QTLs underlying Rice Tolerance to Low‐Potassium Stress in Rice Seedlings
Authors: Wu P. , Ni J. J. , Luo A. C.
Published: July 2010

Potassium is an important nutrient in plant growth and development of rice (Oryza sativa L.), but K availability may be seriously limited in developing countries. Genotypic variation in tolerance to Iow‐K stress has been shown. This study was conducted to investigate the genetic basis for tolerance to low‐K stress in rice and to identify the quantitative trait loci (QTLs) that provide this tolerance. On the basis of preliminary tests, seedlings of 123 double haploid (DH) lines and their parents (which differed in response to K supply) ‘IR64’, indica cultivar and ‘Azucena’, a Japonica variety, were grown in a hydroponic greenhouse study at adequate and at stress levels of K in August, 1995, at Zhejiang Agricultural University, Hangzhoo, China. Plants were sampled after 4 wk in culture solution and measurements were made for plant height, shoot and root dry matter, K concentration in plant tissue, K uptake, and K use efficiency. Relative changes of the parameters from K‐sufficient to K‐stress culture were calculated to evaluate the genotypic variation in tolerance to K‐stress. IR64 was more tolerant to low‐K stress than Azucena. A total of 175 molecular markers mapped on all 12 chromosomes of rice was used to detect QTLs underlying tolerance to Iow‐K stress. These QTLs individually explained about 8 to 15% of the variations in relative changes of the parameters from K‐sufficient to K‐stress culture across the population. The differences in the changes of the parameters between Azucena and IR64 at the marker loci linked to the QTLs detected were from 16 to 39% above the overall means of the population. The identification of QTLs underlying the tolerance of low‐K stress may be useful in selection for multiple traits which include Iow‐K tolerance.
Strategies of Marker‐Aided Recurrent Selection
Authors: Xie Chongqing , Xu Shizhong
Published: July 2010

The choice of a marker‐aided recurrent selection (MARS) strategy depends on a number of factors. An experimental comparison of these factors can be costly or infeasible, but a theoretical comparison can provide some guidelines. This study was conducted to evaluate the genetic aspects of expected responses to various MARS methods and to compare the efficiencies of MARS relative to traditional phenotypic recurrent selection (PRS) and to marker‐aided mass selection (MS). The MARS methods examined here are MS, half‐sib family (HSF), full‐sib family (FSF), S1 family (S1F), testcross progeny (TC), combined FSF selection with within‐family MS (CSFS), and combined HSF selection with within‐family MS (CSI‐IS). If large fr action of the additive genetic variance (p) in a character can be explained by marker loci, the efilciencies of MARS relative to corresponding PRS can be great. This is most pronounced when family size (n) is small and decreases as n increases. An exception to this is for CSHS, where MARS is superior to PRS across all family sizes. Similarly, CSFS performs better than FSF selection under a wider range of family sizes (1 < n < 50). With constant rate selected and a relatively large family size, S1F, CSFS and CSHS selection are superior to MS, whereas HSF selection is inferior to MS. With constraints of the same effective size selected for each method, MS, which takes advantage of the greatest selection intensity, is the most efficient method. Nevertheless, MARS among small families or individual plants can produce substantial increases in selection responses.
Separation and Quantitation of the Sources of Dew on Creeping Bentgrass
Authors: Williams D. W. , Powell A. J. , Dougherty C. T. , Vincelli P.
Published: July 2010

Many fungal pathogens require free water to cause infections. In high‐maintenance turfgrass systems, accumulations of dew are an important source of this water. Little is known about the amount or rate of dew accumulations on turfgrasses under golf course maintenance regimes. Experiments were conducted in 1994 and 1995 to measure separately the different sources of dew as they accumulated throughout the night on irrigated creeping bentgrass (Agrostis palustris Huds.) maintained as a golf fairway. Sources of dew were separated as (i) condensate and (ii) plant‐generated moisture (wound exudates plus guttation). Additionally, re‐accumulating moisture was measured from original collection sites at 0800 h to establish amounts and rates of re‐accumulation after displacement, and the optimal time to displace dew to achieve maximum reductions of dew periods. Mean total dew measured at 0800 h over both years was 0.195 mm, 33% of which was plant generated. Moisture re‐accumulating following displacement had a higher proportion of plant‐generated moisture, ranging from 46 to 77% depending on the time of the observation. Condensate and plant‐generated moisture accumulated at similar rates over time. Significant amounts of total dew re‐accumulated following displacement prior to 0400 h, indicating that dew displacement prior to that time may be much less efficient at reducing the duration of leaf wetness episodes, regardless of the displacement method used.
Interrelationships of Nitrate Uptake, Nitrate Reductase, and Nitrogen Use Efficiency in Selected Kentucky Bluegrass Cultivars
Authors: Jiang Zhongchun , Hull Richard J.
Published: July 2010

The efficiency of nitrate use by turfgrasses is likely related to its efficiency of absorption by roots and its rate of metabolism in roots and shoots. This study was conducted to quantify the relationship between nitrate uptake rate and nitrate reductase activity with N use efficiency in a cool‐season turfgrass. Six cultivars of Kentucky bluegrass (Poa pratensis L.), which differ markedly in field performance, were used to measure intraspecific variation in nitrate uptake, in vivo nitrate reductase activity of roots and leaves, and N use efficiency expressed as clipping mass per unit N in clippings. Companion field studies compared N use efficiency and metabolism among 14 Kentucky bluegrass cultivars established on an Enfield silt loam (Coarse loamy over sandy skeletal, mixed, mesic, Typic Dystrochrepts). Nitrate uptake rate was determined by an in situ nitrate depletion method. Nitrate reductase activity was assayed by an optimized in vivo method. Significant differences among cultivars were observed for nitrate absorption, nitrate reductase activity in roots and leaves, and N use efficiency. Ambient nitrate concentrations influenced these parameters and their intraspecific differences. Nitrate uptake and reduction were saturable at external nitrate concentrations in excess of 1 mM. Regression analyses demonstrated that nitrate reductase activity in roots and leaves was strongly influenced by nitrate uptake rate. Nitrogen use efficiency was negatively related to ambient nitrate levels, nitrate uptake rate and nitrate reductase activity, with nitrate reductase activity in leaves having the strongest negative effect on use efficiency. These results suggest that the efficiency of N use by Kentucky bluegrass may be increased by genetically altering nitrate reductase activity and its partitioning between roots and shoots.
Genetically Engineering Elite Oat Cultivars
Authors: Torbert K. A. , Rines H. W. , Kaeppler H. F. , Menon G. K. , Somers D. A.
Published: July 2010

Previous work has shown that tissue cultures initiated from mature embryos of a specific experimental oat (Avena sativa L.) line, Gaf/Park, can be genetically engineered and fertile plants regenerated. The objectives of this study were to investigate the initiation of tissue cultures from mature embryos of 16 elite North American spring oat cultivars and to determine whether these tissue cultures can be used to produce transgenic plants. Fifteen of the genotypes tested produced at least some embryogenic callus that was similar in appearance to transformable callus. The elite cultivar Belle was tested to determine whether it could be genetically engineered. From 30 microprojectile bombardment treatments, 17 independently genetically engineered tissue cultures were produced that regenerated fertile, transgenic plants. These results indicate that the mature embryo‐derived tissue culture system will be useful for genetically engineering elite oat cultivars.
DNA‐Based Markers for a Recessive Gene Conferring Anthracnose Resistance in Sorghum
Authors: Boora Khazan S. , Frederiksen Richard , Magill Clint
Published: July 2010

Resistance to anthracnose in sorghum [Sorghum bicolor (L.) Moench] accession SC326‐6 was found to segregate as a simple recessive trait in a cross to the susceptible cultivar BTx623.F3 progeny tests following self pollination of 115 F2 individuals identified homozygous resistant and susceptible F2 plants for use in bulked‐segregant analysis. DNA from the parental cultivars and the bulks was screened by PCR amplification with 300 RAPD (random amplified polymorphic DNA) primers. Two RAPD primers amplified a sequence that co‐segregated with the recessive resistance allele, while another amplified a band linked to the susceptible allele.
Accomplishments and Impact from Breeding for Increased Forage Nutritional Value
Authors: Casler M. D. , Vogel K. P.
Published: July 2010

Despite considerable rhetoric, there were no serious efforts to improve genetically the nutritional value of forage crops until the 1960s when advances in analytical chemistry and rumen fermentation technology allowed breeders to adapt meaningful laboratory techniques for repeatably screening thousands of samples in a short time period. Genetic increases in some measure of digestibility, typically in vitro dry matter digestibility (IVDMD), have been documented in new cultivars of at least seven forage crops, including legumes, coolseason grasses, warm‐season grasses, annuals, and perennials. The rate of gain for IVDMD ranges from 8 to 45 g kg±1 cycle±1, which, on a percentage basis (0.7–2.5% yr±1), is similar to long‐term gains for grain yield of many cereal crops. In asexually propagated species, in which all genetic variance can be utilized in a single cycle of selection, gains as high as 11.8% cycle±1 have been reported. Generally, gains in IVDMD are repeatable across a wide range of environments and management systems, including on‐farm tests. Averaged across species, a 1% increase in IVDMD generally leads to a 3.2% increase in average daily gains of beef cattle (Bos taurus). Because increased IVDMD generally does not decrease forage yield per se, and sometimes occurs with increased forage yield, these gains also translate to improved beef production per hectare. The ability to document increased animal performance associated with breeding for increased forage nutritional value can greatly enhance the value of a new cultivar to forage producers, which can lead to rapid adoption of new cultivars.
Individual Locus Effects on Dormancy during Seed Development and After Ripening in Barley
Authors: Romagosa Ignacio , Han Feng , Clancy Janet A. , Ullrich Steven E.
Published: July 2010

Genetic control of seed dormancy in barley (Hordeum vulgare L.) has been studied recently by means of quantitative trait loci (QTL) mapping. Four QTL, designated SDI to SD4, were found associated with about 75% of the phenotypic variation for dormancy in ‘Steptoe’/ ‘Morex’ crosses. The objective of this study was to investigate the individual effects of seed dormancy(SD) QTL and the nature of their epistatic interactions on dormancy during seed development and after ripening. Six F1‐derived doubled haploid lines from Steptoe/Morex crosses, selected on the basis of the flanking marker alleles for the four SD QTL, and the two parents were grown under greenhouse conditions. The same lines and four additional doubled haploid lines from the same cross were also grown in a field experiment. Genotypic dependence of onset, maintenance, and release of dormancy was studied. To assess dormancy, germination tests of excised embryos from fresh and artificially dried seed were conducted during seed development. All genotypes showed a similar pattern of germination of excised embryos. Since no differences in the time of dormancy inception were found, this phenomenon does not seem to be controlled by the SD QTL. Rather, the SD QTL were involved in the release of dormancy at the end of the development process and during after ripening. The presence of the Steptoe allele at SD1 on chromosome 7 (5H) kept precocious germination to a minimum until the end of the seed development process. On the basis of the dormancy profiles at after ripening, genotypes could be classified as affecting early, intermediate, and late dormancy release. These groups were genotypically dependent. A model for allele interactions among the SD QTL was developed.
Comparative Response of Two Reciprocal Recurrent Selection Methods in BS21 and BS22 Maize Populations
Authors: Menz Rademacher Mónica A. , Hallauer Arnel R. , Russell W. A.
Published: July 2010

Reciprocal recurrent selection (RRS) has not been widely adopted by maize (Zea mays L.) breeders because pedigree selection methods were effective in developing improved inbred lines. RRS as been used successfully, but modified reciprocal recurrent selection (MRRS) uses elite inbred lines as testers, which may be more useful in applied breeding programs. A study was conducted to compare responses to selection via RRS and MRRS in the BS21 and BS22 maize populations. After six cycles of RRS and MRRS, an experiment was conducted to determine the direct and the indirect responses to selection. The populations themselves, testcrosses to inbred testers, and crosses between BS21 and BS22 were evaluated at four locations for 2 yr. Grain yield increased significantly in all population crosses. Direct response to selection was greater for the RRS method than for the MRRS method: 4.4% cycle−1 for BS21(R) × BS22(R); 2.8% cycle−1 for BS21(HI) × A632; and 1.6% cycle for BS22(HI) × H99. RRS was as effective as MRRS for improving grain yield of BS21(R) and BS22(R) in crosses with A632 and H99, but MRRS was not as effective as RRS in the improvement of the BS21(HI) × BS22(HI) cross populations: 1.6%−1 cycle for BS21(HI) × BS22(HI) vs. 4.4% cycle−1 for BS21(R) × BS22(R).There was no evidence that the genetic variation among testcrosses for grain yield was greater with use of inbred lines as testers compared with use of populations as testers.
Evaluation of a Viability Model for Predicting Soybean Seed Germination during Warehouse Storage
Authors: Fabrizius Eric , TeKrony Dennis , Egli D. B. , Rucker Marcy
Published: July 2010

A method for predicting soybean [Glycine max (L.) Merr.] seed germination during storage would benefit seed producers and the seed industry. This investigation evaluated the ability of the Ellis and Roberts deterioration model to predict seed germination after warehouse storage and the accuracy of a rapid‐aging test to estimate initial seed quality (K1). Seed lots with low levels of mechanical injury and Phomopsis longicolla (Hobbs) seed infection produced in 1990 and 1991 were stored more than 2 yr in multiwall paper bags in seed warehouses in Kentucky and Indiana. Warehouse temperature was monitored and seed moisture and germination were determined at 3‐mo intervals. The rapid‐aging test (40°C and 150 g kg−1 seed moisture [fresh weight basis]) was used to estimate K1 for each seed lot. The model accurately (±10 percentage points) predicted germination most seed lots after one carryover year of storage (1 yr after the first spring planting season, = 430 d), when little deterioration had occurred. After 2 yr of carryover storage (= 800 d), when germination had declined, the model accurately predicted the germination of only six of 16 seed lots. The inaccurate predictions may have been related to variation in K1 (substantial variation occurred between repeated determinations on the same seed lot) or to variation among seed lots in the rate of deterioration at constant temperature and seed moisture. These results suggest that some of the assumptions underlying the Ellis‐Roberts seed deterioration model may be invalid and require further evaluation.
Influence of Trinexapac‐Ethyl on Diamond Zoysiagrass in a Shade Environment
Authors: Qian Y. L. , Engelke M. C.
Published: July 2010

‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.] has excellent shade tolerance when compared with other zoysiagrass cultivars. However, because of excessive shoot growth and carbohydrate depletion, turf stand declines with time when shade levels exceed 80%. Two separate studies were conducted to determine if the plant growth regulator trinexapac‐ethyl (TE), which suppresses shoot growth, could improve turf performance of Diamond zoysiagrass under shade conditions. Well‐established turf was subjected to a constant 86 and 88% shade in the greenhouse and polyhouse, respectively. Trinexapacethyl treatments included monthly applications at 0.048 kg a.i. ha−1 (MTE), bimonthly applications at 0.096 kg a.i. ha−1 (BTE), trimonthly applications at 0.192 kg a.i. ha−1 (TTE), and the untreated control. Treatments in 1997 were made from January through August for the greenhouse study and from April to September for the polyhouse study. Diamond receiving MTE and BTE maintained acceptable turf quality throughout the study, while turf quality of the control deteriorated to unacceptable levels <3 mo after shading. Diamond treated with TTE maintained better turf quality than that of the control, but was inferior to MTE and BTE treatments. Compared with control plots, turf receiving MTE and BTE had (i) 76 to 73% less shoot vertical growth and 77 to 75% less clippings, (ii) 40 to 38% higher total nonstructural carbohydrate content, (iii) 60 to 50% higher root mass and 51 to 46% higher root viability, and (iv) 48 to 42% higher photosynthesis. Results suggested that monthly or bimonthly repeated application of TE at 0.048 or 0.096 kg a.i. ha−1 greatly enhanced the shade tolerance of Diamond zoysiagrass.
Quantitative Trait Loci for Flour Viscosity in Winter Wheat
Authors: Udall J. A. , Souza E. , Anderson J. , Sorrells M. E. , Zemetra R. S.
Published: July 2010

Starch paste viscosity of wheat (Triticum aestivum L.) flour is predictive of wheat quality in some styles of oriental noodles. We mapped quantitative genetic variation for flour paste viscosity in the recombinant inbred (RI) population of 78 lines derived from the cross NY6432‐18/‘Clark's Cream’. The population was evaluated for three seasons in Aberdeen, ID, and one season at Moscow, ID, and Ithaca, NY. We identified nine restriction fragment length polymorphism (RFLP) markers (Xbcd1086, Xbcdl307, Xbcd135c, Xbcdl8, Xbcd402, Xbcd98, Xcdo456, Xcdo678, and Xcdo718) that were associated with significant differences (P < 0.01) in starch viscosity among the RI lines at two or more locations. The RFLP markers Xbcdl307, Xbcd135c, and Xbcdl8c had the largest effects across all five environments; they were each associated with an approximate 7% increase in flour viscosity averaged across all RI lines and environmens. Starch viscosity can be increased by mutations to the granule bound starch synthase( GBSS) gene of wheat. However, this mapping population is not segregating for GBSS mutations. Therefore, the quantitative trait loci (QTL) identified in this research could likely be combined with the qualitative mutations that are know in other genotypes.
Evaluation of the Gossypium Gene Pool for Foliar Terpenoid Aldehydes
Authors: Khan M. Altaf , Stewart J. McD. , Murphy J. B.
Published: July 2010

Terpenoid aldehydes (TAs) accumulate in the lysigenous glands of Gossypium L. (cotton genus) and related genera and are toxic many insect pests. Knowledgeo f the diversity of TAsa vailable in the Gossypium germplasm pool could be useful in developing cultivars with enhanced expression of specific compounds to improve hostplant resistance (HPR). Qualitative and quantitative foliar analyses for seven TAs were performed by means of high performance liquid chromatography (HPLC) on Thespesia thespesioides (Brown ex Benth.) Fryxell and on 40 Gossypium genotypes comprising 30 species. Gossypium mustelinum Miers ex Watt had the highest leaf concentration of the heliocides H1 and H4 and total TAs, while heliocides H2 and H3, and hemigossypolone were highest in G. capitis‐viridis Mauer, G. lobatum Gentry, and G. nobile Fryxell, Craven & Stewart, respectively. Gossypol was highest in T. thespesioides and an accession of G. laxum Phillips, although the former contained 60% more than the latter. Gossypium raimondii UIbrich contained principally the unique TA, raimondal. Gossypol was the principal foliar TA in most of the D genome species, whereas, species in the B, C, F, G, and K genomic groups had very low concentrations of foliar gossypol compared with other TAs. In the AD genome, with minor exceptions, all six TAs occurred. Three distinct TA patterns were observed among seven G. laxum accessions. The diversity in biosynthesis and accumulation of TAs among Gossypium species should provide useful germplasm for modifying the TA quality and quantity of cotton. Resource material is also identified to study the metabolic pathways and regulatory mechanisms controlling the synthesis of these compounds.