bluuebunny/crossref_metadata_2025 huggingface dataset:
A RAPD Genetic Map of Saccharum officinarum
Authors: Mudge J. , Andersen W. R. , Kehrer R. L. , Fairbanks D. J.
Published: July 2010

Saccharum officinarum L. is the major contributing species to modern sugarcane varieties. It is a polyploid where 2n = 80, although the basic chromosome number and level of ploidy have not been conclusively determined. A genetic map in S. officinarum could benefit breeding programs through marker‐assisted selection and could provide information about the genetic structure of sugarcane. The objective of this research was to develop a genetic linkage map by means of random amplified polymorphic DNA (RAPD) single‐dose markers in S. offcinarum. The map was constructed with 84 F1 progeny from the cross ‘La Purple’ (S. officinarurn) × ‘Molokai 5829’ (S. robustum Brandes and Jeswiet ex Grassl.). Single‐dose markers should segregate in a 1:1 fashion in the progeny of this cross. Primers were first screened in the parental genotypes, and those revealing polymorphisms were then tested in six progeny selected at random to identify putative single‐dose markers. All resulting markers were then tested in 84 progeny and those showing a 1:1 segregation pattern were considered single‐dose markers and were used for mapping. Among 279 singledose markers identified from initital screening with 1840 primers, 161 markers were linked in 50 linkage groups with a minimum LOD of 5.0 and a maximum recombination value of 0.28. The detection of 12 repulsion linkages suggested the occurrence of limited preferential chromosome pairing in this species. Linkage of eyespot susceptibility to a RAPD marker identified an additional linkage group and indicated that linkages identified in this map could potentially be used for marker‐assisted selection.
Genetic Diversity among Elite Sorghum Inbred Lines Assessed with DNA Markers and Pedigree Information
Authors: Ahnert D. , Lee M. , Austin D. F. , Livini C. , Woodman W. L. , Openshaw S. J. , Smith J. S. C. , Porter K. , Dalton G.
Published: July 2010

The amount of genetic diversity in parental lines of commercial sorghum [Sorghum bicolor (L.) Moench] hybrids is unknown, yet such comprehensive knowledge could improve the effectiveness of future hybrid development programs. Restriction fragment length polymorphisms (RFLPs) and pedigree data were used to investigate the genetic relationships in a group of 58 fertility restorer (R) and 47 sterility maintainer (B) elite sorghum inbred lines. The objectives of this study were to (i) assess the level of genetic variation for RFLPs in these lines, (ii) estimate genetic similarity (GS) based on RFLPs and pedigree information for R‐ and B‐lines, and (iii) examine the agreement between RFLP‐based GS and coancestry coefficient (f) for related (f> 0) pairs of inbreds. R‐lines, derived mainly from Feterita and Zera‐zera, and B‐lines, mostly from kafir germplasm, were analyzed for RFLPs with 104 DNA probes. A total of 326 patterns of RFLP bands was observed, with 276 being common to both R‐ and B‐lines, 32 unique to R‐lines, and 18 unique to B‐lines. On average, 3.6 patterns per clone‐enzyme combination were found for R‐lines and 3.0 for B‐lines. Average GS based on RFLPs was 0.67 for R‐lines and 0.76 for B‐lines, indicating more diversity within the R‐group The average for R‐lines was 0.08 and for B‐lines 0.07. Cluster analysis of GS estimates from the entire set (105) of inbreds revealed separate groups for R‐ and B‐lines in agreement with parental types, pedigree information, and the classification system used by breeders. R‐lines clustered into two main groups, one derived mainly from Feterita and the other from Zera‐zera. B‐lines were grouped into different sub‐clusters. GS and f were positively correlated for R‐lines (r = 0.46) and for B‐lines (r = 0.43), suggesting that RFLP data may help quantify the degree of relatedness in elite sorghum germplasm.
Volatile and Dislodgeable Residues Following Trichlorfon and Isazofos Application to Turfgrass and Implications for Human Exposure
Authors: Murphy K. C. , Cooper R. J. , Clark J. M.
Published: July 2010

In this study, volatile and dislodgeable residues were determined following insecticide application of trichlorfon (dimethyl 2,2,2‐trichloro‐1‐hydroxyethyiphosphonate) or isazofos (O‐5‐chloro‐1‐isopropyl‐1H‐1,2,4‐triazol‐3‐yl O,O‐diethylphosphorothioate) to a 10‐m radius plot of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) to assess human exposure and possible toxicity. Trichlorfon was applied either with or without irrigation following application, whereas isazofos application was always followed by irrigation. For all applications, less than 12% of applied insecticides were lost as measured volatile residues during the experimental sampling periods. Volatile loss declined in a diphasic pattern with most loss occurring within 5 to 7 d of application. Irrigation greatly reduced initial volatile and dislodgeable residues. Subsequent volatile and dislodgeable residues, however, increased substantially on Days 2 and 3 compared with residue levels in the absence of irrigation. Trichlorfon dislodgeable residues never exceeded 1% of applied compound in the absence of irrigation, whereas with irrigation, trichlorfon, and isazofos dislodgeable residues were never greater than 0.5% of applied compound. Irrigation increased the transformation of trichlorfon to DDVP (2,2‐dichlorovinyl dimethyl phosphate), a more toxic insecticide. Inhalation and dermal exposures were estimated using measured air concentrations and dislodgeable residues, respectively, and hazard quotients (HQs) were calculated. A HQ less than 1 indicated that the residue level is below a concentration that might reasonably be expected to cause adverse effects in humans. Calculated inhalation HQs for volatile residues were equal to or less than 1 for all sampling periods except Days 1 (HQ = 5.0), 2 (HQ = 4.5) and 3 (HQ = follo wing isazofos application. Calculated dermal HQs from dislodgeable residues were equal to or less than 1 except for DDVP on Day 2 (HQ = 4.6) when trichlorfon application was followed by irrigation, and on Days 2 (HQ = 14.3) and 3 (HQ = 5.7) following isazofos application.
Heritabilities of Nutritive Quality Factors and Interrelationships with Yield in Tetraploid Crested Wheatgrass
Authors: Ray Ian M. , Karn James F. , Dara Syed T.
Published: July 2010

Detailed information on the genetic variation of forage quality traits and their relationship with forage yield under seeded competitive conditions is limited in crested wheatgrass. This research was conducted to determine the heritabilities (h2), of forage quality parameters in tetraploid crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] grown under competitive conditions. Genetic correlations among nutritive quality traits and yield were also determined. Thirty randomly selected half‐sib families from a genetically broadbased crested wheatgrass population were evaluated at one location from 1991 to 1992 in single‐row plots that were 1.5 m long, spaced 38 cm apart, and seeded at a rate of 90 seed m−1. Heritabilities were determined for crude protein, in vitro digestible dry matter (IVDDM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose based on the means of the 30 families. Variation among families was significant (P ≤ 0.01) for all traits. Heritability estimates (approaching narrow sense heritability) for IVDDM, crude protein, NDF, ADF, and hemicellulose were 50, 53, 63, 68, and 72%, respectively. Genetic correlations indicated that digestibility was positively associated with crude protein (r = 0.65; P < 0.01) and negatively influenced by NDF and ADF (r = − 0.79 and − 1.04; P < 0.01). Genetic correlations between forage quality traits and yield were low under competitive conditions indicating that independent selection for each trait would result in improved forage quality and yield. Interaction variance components were significantly different from zero, and rank correlations between years were low for most forage quality traits. The data indicated that maximum gain in nutritive quality improvement in crested wheatgrass may require multiple years of evaluation.
Forage Yield and Digestibility of African Pearl Millet Landraces in Diallel with Missing Cross
Authors: Ouendeba B. , Hanna W. W. , Ejeta G. , Nyquist W. E. , Santini J. B.
Published: July 2010

Shortage of nutritious forage is limiting animal production in the semiarid regions of Africa. This study was conducted to evaluate the magnitude of heterosis for forage production and dry matter digestibility in African landraces of pearl millet [Pennisetum glaucum (L.) R. Br.]. Five landrace populations, 9 of 10 interpopulation crosses, and two hybrids were evaluated in a randomized complete‐block design with five replications for dry matter forage yield and in vitro dry matter digestibility (IVDMD) in 1989 and 1990 in Tifton, GA. Entries in only two replications were evaluated for digestibility. The missing cross was estimated, and both the traditional and Gardner‐Eberhart analyses were performed. Highly significant difference between crosses (9.94 t ha−1) and parents (8.50 t ha−1), or average heterosis, well as general combining ability was observed in the combined analyses for dry weight forage yield. No other partitions of entries for either trait were significant. Year × entries was significant for forage yield but not for IVDMD. All midparent and high‐parent heterosis values were positive for forage yield but were nonsignificant. High‐parent heterosis values ranged from 3.3 (‘Iniari’ × ‘Mansori’) to 22.9% (Iniari × ‘P3Kolo’) for dry matter forage yield. No heterosis was observed for IVDMD. Heterosis for forage yield did not affect IVDMD. These results suggest that use of pearl millet hybrids can contribute to increased forage production in semiarid Africa.
Gain for Pickling Cucumber Yield and Fruit Shape Using Recurrent Selection
Authors: Wehner Todd C. , Cramer Christopher S.
Published: July 2010

Qualitative traits of cucumbers (Cucumis sativus L.) such as disease resistance have been improved significantly during the past 30 yr. On the other hand, quantitative traits such as yield, earliness, and fruit shape have been improved less. The objective of this study was to determine the progress that could be made on such traits with recurrent selection in three pickling cucumber populations (NCMBP, NCEPI, and NCH1). During population improvement, one or two replications of 200 to 335 half‐sib families were evaluated in the spring season for total, early, and marketable fruits per plot, a fruit shape rating, and a simple weighted index (SWI = 0.2 × total yield / 2 + 0.3 × Early yield + 0.2 × % marketable yield / 10 + 0.3 × quality). Families from each population were intercrossed in an isolation block during each summer with remnant seeds of the best 12% selected with the index. Progress was evaluated by means of a split‐plot treatment arrangement in a randomized complete block design with 32 replications in each of two seasons (spring and summer). Whole plots were the three populations, and subplots were the 10 to 11 cycles (Cycles 0–9 plus cheeks). Populations were improved for performance in a selected (spring season) as well as a non‐selected environment (summer season). Greatest gains were made for the NCMBP population, with an average of 54% gain from Cycle 0 to 9 over the five traits, and for early yield, with an average of 65% gain from Cycle 0 to 9 over the three populations. In other trials, NCH1 had the best mean performance. Based on those results, modified half‐sib recurrent selection can be used to improve fruit yield and quality of NCMBP, NCEP1, and NCH1 populations. Further studies should be made on NCMBP because it had the greatest gain per year, and on NCH1 because it had the highest mean performance.
Assessment of Potato Breeding Progress in the USA over the Last Century
Authors: Douches D. S. , Maas D. , Jastrzebski K. , Chase R. W.
Published: July 2010

Potato (Solanum tuberosum subsp. tuberosum) production has increased six‐fold (per unit area) in the USA since the 1920s. Direct comparison of potato cultivars released during the past century can help us understand how potato breeding has contributed to these production improvements and to other important traits associated with marketing and utilization. Our objective was to study trends in potato genetic improvement during four subjective breeding periods (BP) (pre‐1900 = BP I; 1930 to 1949 = BP II; 1950 to 1969 = BP III; 1970 to present = BP IV), and also to compare performance between and within the three major cultivar types (round‐white, long, and red‐skinned). In field trials conducted from 1990 to 1992, under best management practices (with scheduled irrigation) in Michigan, the greatest total yield potential was observed in several cultivars released during BP I and II. These cultivars also had late vine maturities. On average, BP II had the greatest marketable yield. Cultivars released in BP III had the lowest total yield, earliest vine maturity, highest scab resistance and most favorable tuber appearance. General trends over periods were for earlier maturity and improved tuber appearance. Round‐white cultivars improved for chip‐processing ability and dry matter content over breeding periods, while long types increased in percent marketable yield only in BP IV. No trends were observed for scab resistance. When cultivars were grouped according to tuber type, there were no differences in total yield; however, the long types had the lowest marketable yield and the red‐skinned types had lowest dry matter content.
Leaf Rust Resistance Gene Lr9 and Winter Wheat Yield Reduction: I. Yield and Yield Components
Authors: Ortelli Silvano , Winzeler Hans , Winzeler Michael , Fried Padruot M. , Nösberger Josef
Published: July 2010

Leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici) resistant near isogenic lines (NIL) of wheat (Triticum aestivum L.) have generally lower yields than the susceptible recurrent parent under disease free conditions. Analysis of growth and yield should increase our understanding of the reduced yielding ability of NIL. In a 3‐yr field study, the yield components of the leaf rust susceptible cultivar Arina were compared with six resistant NIL carrying the resistance gene Lr9 introduced from Aegilops umbellulata. The NIL were derived from two independently developed backcross populations with Arina as the recurrent parent. The NIL were phenotypicaily very similar to Arina. At anthesis and at mediumilk stage, the total aboveground dry matter was similar for the NIL and Arina. Differences in the dry matter accumulation appeared only after the medium milk stage. At maturity, the NIL had a 12% lower grain yield than Arina (5.88 ha−1) with a range from 5 to 14%. The lower grain yield resulted from a 3 to 11% reduction in grain number per square meter and a 2 to 7% reduction in mean grain weight. The smaller grain number per square meter was the result of a 6% smaller tiller number per plant and a 2% smaller grain number per ear. Artificially reducing grain number per ear suggested that both a reduced supply of assimilates and a diminished capacity to incorporate assimilates in the grain caused the reduced grain yield of the NIL. Deleterious effects of alien genes linked with the Lr9 gene from Aegilops umbellulata cannot be ruled out. However, the small differences within and between the NIL of the two Lr9 populations for the parameters tested suggest a direct relation between the yield depression and the leaf rust resistance conferred by the Lr9 gene.
Soybean Seed Quality Reductions by High Day and Night Temperature
Authors: Gibson L. R. , Mullen R. E.
Published: July 2010

Environmental stress during reproductive growth of soybean [Glycine max (L.) Merr.] may reduce seed germination and vigor. Most studies of environmental influence on soybean seed germination and vigor have concentrated on the effects of drought, maximum day temperature, or average daily temperatured uring seed fill. This study was conducted to determine the effects of different combinations of day temperatures and night temperatures during reproductive growth on soybean seed quality. Day/night temperatures of 30/20, 30/30, 35/20, and 35/30°C were imposed at flowering and pod set (R1‐R5), seed fill and maturation (R5‐R8), and during the entire reproductive growth period (R1‐R8). High day and night temperature reduced soybean seed germination and seedling vigor. The extent of reductions in germination and vigor by high temperature was influenced by duration of temperature exposure and phase of reproductive growth. Temperatures during flowering and pod set exerted little influence on soybean seed quality. A combination of 35°C day temperature and 30°C night temperature during seed fill and maturation or 35°C day temperature from flowering to maturity decreased germination. Seedling vigor was reduced by 35/20, 30/30, and 35/30°C during seed fill and maturation and the entire reproductive period. Increase in night temperature from 20 to 30°C decreased seedling vigor at both 30 and 35°C day temperatures. These results suggest that Incational and seasonal differences in soybean seed quality may be induced by high temperatures during reproductive growth and indicate that night temperatures along with day temperatures are important in determining soybean seed quality.
Simple Sequence Repeat Markers Developed from Maize Sequences Found in the GENBANK Database: Map Construction
Authors: Senior M. L. , Chin E. C. L. , Lee M. , Smith J. S. C. , Stuber C. W.
Published: July 2010

Simple sequence repeats (SSRs) are rapidly becoming an important class of DNA markers that are being widely used to map both plant and animal genomes. SSRs have the advantage of providing a codominant marker system based on polymerase chain reaction (PCR) methodology. Although the presence of SSRs is now well documented in the plant kingdom, a mapped set of primer sequences in maize (Zea mays L.) is not available. Polymorphic primer pairs developed from maize sequences in GENBANK were mapped to 42 loci in maize by means of either a B73 × Mo17, Mo17 × H99, or B73 × G35 recombinant inbred population. All SSR loci were found to be linked to one or more adjacent restriction fragment length polymorphism (RFLP) and/or isozyme loci. Segregation followed a pattern of Mendelian inheritance with one SSR locus deviating from expected ratios at a 1% level of significance. The SSRs were distributed throughout the maize genome with no evidence of clustering. Each SSR marker detected a single locus.
Micropropagation of Switchgrass by Node Culture
Authors: Alexandrova K. S. , Denchev P. D. , Conger B. V.
Published: July 2010

Switchgrass (Panicum virgatum L.) is naturally outcrossing; therefore, maintenance of genotype is difficult through sexual propagation. The objective of this study was to develop a micropropagation procedure for the multiplication of desired or selected genotypes. Nodal segments were surface sterilized, split longitudinally, and placed with the cut surface on solid MS medium containing 30 g L−1 maltose and different concentrations of 6‐benzylaminopurine (BAP) as the only growth regulator. Best shoot proliferation was obtained with 12.5 μM BAP and culture at 29°C. Shoots were easily rooted on MS medium without BAP. Under optimum conditions, it is possible to produce approximately 500 plantlets from one parent plant in 12 wk.
Improving Common Bean Performance under Drought Stress
Authors: Schneider Kristin A. , Rosales‐Serna Rigoberto , Ibarra‐Perez Francisco , Cazares‐Enriquez Benito , Acosta‐Gallegos Jorge A. , Ramirez‐Vallejo Porfirio , Wassimi Nasrat , Kelly James D.
Published: July 2010

Drought is the second major constraint to common bean (Phaseolus vulgaris L) production after disease. This study examined yield under drought, yield potential, drought susceptibility index, harvest index, and geometric mean as potential indicators of drought resistant genotypes. The performance of two common bean populations, consisting of 78 and 95 recombinant inbred lines, was examined under moisture stress and nonstress regimes. Experiments were conducted at seven locations (1990–1994) in Michigan and Mexico to identify effective selection criteria for drought resistance. Two genotypes from each population yielded in the top 10% under both stress and nonstress conditions. Heritability estimates for yield in the Sierra/AC1028 population, based on 5 yr of data, ranged from 0.55 to 0.59 for stress and nonstress, respectively, and from 0.20 to 0.19 for stress and nonstress, respectively, in the Sierra/Lef‐2RB population. Heritability for plant biomass was 0.52 for stress and 0.55 for nonstress in the Sierra/AC1028 population and 0.15 under stress and 0.05 under nonstress in the Sierra/Lef‐2RB population. One‐hundred seed weight was the most highly heritable trait in both populations with heritability estimates of 0.80 for the Sierra/AC1028 population and 0.65 for the Sierra/Lef‐2RB population. The geometric mean of the two moisture regimes was the single strongest indicator of performance under stress and nonstress, and a breeding strategy that involves selection based first on the geometric mean, followed by selection based on yield under stress, was suggested as the most effective strategy to improve drought resistance in common bean.
Estimation of Outcrossing Rate in Common Bean
Authors: Ibarra‐Perez Francisco J. , Ehdaie Bahman , Waines J. Giles
Published: July 2010

To assess genetic and environmental variation for outcrossing in common bean (Phaseolus vulgaris L.), a bulk of nine purplehypocotyled (dominant), black‐seeded, common bean lines (pollen parents) and six green‐hypocotyled (recessive), white‐seeded, common bean lines (seed parents) representing Mexican germplasm were used to estimate outcrossing rate. The experiment was conducted at Irvine and Riverside, CA, in mid‐May and mid‐July of 1989 and 1991. Outcrossing estimates were based on the proportion of purplehypocotyled progeny from green‐hypocotyled parents. Approximately 1400 single‐plant families were progeny tested in which 120 278 seedlings were scored for the presence of anthocyanin in the hypocotyl. Of these, 113 246 were classified as selfed progeny and 7031 as hybrid progeny, giving rise to a weighted mean outcrossing rate of 6.9%. Entire progenies from each maternal line were grown and scored, and the minimum and maximum rates of outcrossing observed ranged between 0.0 and 78.0%. Mean outcrossing rate for the six white‐seeded lines ranged from 4.41 to 10.16%. However, differences in outcrossing rate among these lines were not significant, nor were differences between dates of planting, locations, or years. The combined analysis of variance showed significant location × planting date × line interaction and year × location × line interaction, indicating that environmental factors had a strong effect on rate of outcrossing in the lines examined.
Total Non‐Structural Carbohydrates in Winter Wheat Populations Segregating for Snow Mold Tolerance
Authors: Mohammad F. , Windes J. M. , Souza E.
Published: July 2010

Evaluation of wheat (Triticum aestivum L.) for tolerance to snow mold (caused by Typhula idahoensis Remsberg) is difficult because of the irregular occurrence and distribution of the disease in the field. Some wheat genotypes tolerant to snow mold are known to accumulate high levels of total non‐structural carbohydrates (TNC), a trait that could be utilized for rapid screening of snow mold tolerance. The objective was to determine the heritability of TNC and the correlation of TNC with survival under disease pressure in two hard red winter wheat populations segregating for snow mold tolerance. Whole‐plant TNC content (excluding roots), grain yield, and survival were measured in experiments planted near Tetonia, ID, an area prone to snow mold in wheat. Two experiments consisted of BC1F6 and BC1F7 lines derived from two crosses, ‘Manning’*2/‘Survivor’ and ‘Blizzard’*2/‘Sumner’. The third (mixed) experiment consisted of selected lines from each cross. In 1992–1993, conditions were excellent for the occurrence of snow mold infection, but no obvious snow mold damage occurred in 1993–1994. Heritability estimates of TNC measured before snowfall were 64.7% for the Manning population, 82.6% for the Blizzard population, and 87.0% for the Mixed population. Heritability estimates for winter survival were nonsignificant because of differences in snow mold infection between the 2 yr. Correlation of fall TNC levels with spring 1993 survival was r = 0.55 (P < 0.01) in the Manning backcross population, nonsignificant for the Blizzard population, and r = 0.48 (P < 0.01) in the Mixed population, suggesting that accumulation of TNC is moderately correlated to snow mold tolerance. Levels of TNC in the fall had no significant line × year interaction. Selection based upon TNC would advance a population toward higher TNC levels and may indirectly increase tolerance to snow mold in some populations.
Association of Elevated Stearate with Agronomic and Seed Traits of Soybean
Authors: Hartmann Richard B. , Fehr Walter R. , Welke Grace A. , Hammond Earl G. , Duvick Daniel N. , Cianzio Silvia R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] genotypes with elevated stearate content in the seed oil may be useful for food and industrial applications. The objective of this study was to determine the association of elevated stearate with agronomic and seed traits of soybean. Two high‐yielding cultivars with normal stearate content of ≈ 40 g kg−1 were crossed to lines with the genotype fasa fasa that had an elevated stearate content of >200 g kg−1. From each of the two populations, 75 F3‐ or F5‐derived lines that ranged in stearate content from ≈ 40 to 230 g kg−1 were selected for replicated testing at two locations in Iowa during 1993 and 1994. There were significant differences between the means of the elevated and normal stearate lines for seed yield, maturity, lodging, plant height, and content of protein, oil, palmitate, oleate, linoleate, and linolenate. The coefficients obtained from the linear regression of mean seed yield of the lines on their mean stearate content were negative and significant. Although the fasa allele generally had a negative influence on seed yield across a range of elevated stearate contents, there were lines with elevated stearate contents that were not significantly different in seed yield than the highest yielding line in the population. The results indicated that it may be possible to develop cultivars with the fasa fasa genotype that have acceptable seed yield and moderately elevated stearate content.
Inheritance of the Stay Green Trait in Sunflower
Authors: Cukadar‐Olmedo Belgin , Miller Jerry F.
Published: July 2010

The stay green trait of sunflower (Helianthus annuus L.) inbred lines and hybrids has been observed in the field. These genotypes have greener stems at physiological maturity, potentially resulting in improvements in overall plant health, resistance to drought and pests, and standability. Research on inheritance of the stay green trait may provide valuable information to plant breeders for developing new cultivars with this important trait. This study was conducted to investigate inheritance of the stay green trait between two maintainer (HA234 and HA290) and between two restorer (RHA377 and RHA274) sunflower inbred lines. The inheritance study included parents, F1, F2, and backcross generations. Change in stem color was used as the criterion for the stay green characteristic. Color slide pictures of stems were taken at 10‐ to 15‐d intervals in the field between flowering and physiological maturity, and stem color was analyzed by a computer program called Map and Image Processing System. Generation mean analysis indicated that additive effects were the main source of genetic variation for the stay green trait in both crosses. In addition to additive and dominance gene effects, additive × dominance epistatic effects contributed significantly to the variability in the restorer line cross. Since additive effects were predominant, selection for this trait could be made in early generation segregating populations. Significant but small correlation coefficients between stem color at physiological maturity and stem color at earlier stages of development indicated that selection for stay green would be most effective at physiological maturity.
Visible and Near‐Infrared Reflectance Assessment of Salinity Effects on Barley
Authors: Peñuelas Josep , Isla Ramón , Filella Iolanda , Araus José Luis
Published: July 2010

Synopsis

We studied the effects of a soil salinity gradient (0.8−1.9 dS m−1 ECa) on spectral reflectance of 10 genotypes of barley (Hordeum vulgare L.) to determine the efficacy of reflectance as a tool for assessing the responses of barley to salinity. NDVI [normalized difference vegetation index, (R900 nm − R680 nm)/(R900 nm + R680 nm)] and WI (water index, R970 nm/R900 nm) were the reflectance indices used. In response to increasing salinity, near infrared reflectance decreased and visible reflectance increased, thereby lowering NDVI from 0.85 to 0.4, in parallel with decreases in biomass (from 2500–500 g m−2) and yield (from 900–50 g m−2). NDVI was, thus, a good indicator of biomass and yield. WI increased from 0.73 to 0.96, δT (canopy temperature minus air temperature) increased from −2 to 7°C, and 13C discrimination (Δ13C) in mature kernels decreased from 19 to 14.5 with increasing salinity levels. WI was, thus, related to crop water status response to salinity. NDVI and WI were, therefore, useful for measuring agronomic responses of barley to salinity.
Field Emergence of Solid Matrix Seed Primed Turfgrasses
Authors: Yamamoto I. , Turgeon A. J. , Duich J. M.
Published: July 2010

Seedling emergence is a critical stage in turfgrass establishment, influencing the managemenant d use of turfs. A series of field experiments and supplemental germination tests were conducted to determine solid matrix priming (SMP) effects on turfgrass species and cultivars. Seedling emergence was investigated under field conditions for three cool‐season species, 11 cuitivars of Kentucky bluegrass (KBG) (Poa pratensis L.), seven cultivars of perennial ryegrass (PR) (Lolium perenne L.), and seven cultivars of tall fescue (TF) (Festuca arundinacea Schreb.). The SMP treatments reduced time required for emergence and improved final emergence. The degree of effects varied among species and cultivars, and environmental conditions. The greatest SMP responses appeared in slow‐emergence species, such as KBG, under cool temperatures. The apparent emergence responses observed under field conditions resulted from combined effects of original seed vigor, SMP treatments, and environmental conditions. The use of SMP turfgrass seed of selected cultivars‐species may be preferable to the use of unprimed seed when seeding schedule is delayed, unseasonably cold weather is forecasted, and/or quick renovation is desired.
Estimation of Mixed Linkage [β‐Glucan Concentration in Oat and Barley from Viscosity of Whole Grain Flour Slurry
Authors: Doehlert Douglas C. , Zhang Decai , McMullen Michael S. , Moore Wayne R.
Published: July 2010

The presence of [β‐glucan from oat (Avena sativa L.) or barley (Hordeum vulgare L.) products in the human diet can lower serum cholesterol. The selection of new oat or barley cuitivars with higher β‐glucan concentration in the grain is usually limited by the efficiency of the analytical procedure required to measure this component. The utility of flour slurry viscosity as an indirect means of estimating flour β‐glucan concentration was investigated. Water at 25°C was added to enzyme‐inactivated whole‐grain oat flour to form a 23% dry matter mixture, and stirred to form a uniform slurry. Viscosity, as measured with a rotational spindle‐type viscometer, increased hyperbolically with time. Viscosity measured 3 h after water addition was exponentially dependent on flour content and was linearly correlated with β‐glucan concentration in the flour. The procedure was useful as a screening method for the estimation of β‐glucan concentration in preliminary breeding lines of oat and barley. The procedure is effective with enzyme‐inactivated (steam‐treated) whole or dehulled grain, but the presence of endo‐β‐glucanases in hulls of oats and barley prevent the application of this procedure with flours of raw whole oats and barleys.
Identifying Mega‐Environments and Targeting Genotypes
Authors: Gauch Hugh. G. , Zobel Richard W.
Published: July 2010

To maximize yield throughout a crop's heterogeneous growing region, despite differences in cultivar rankings from place to place due to genotype‐environment interactions, frequently it is necessary to subdivide a growing region into several relatively homogeneous mega‐environments and to breed and target adapted genotypes for each mega‐environment. The objectives of this study are to identify relevant criteria for evaluating mega‐environment analyses and to apply the Additive Main Effects and Multiplicative Interaction (AMMI) model to mega‐environment analysis. The proposed analysis is illustrated using a Louisiana corn (Zea mays L.) trial. Statistical strategies for identifying mega‐environments should meet four criteria: flexibility in handling yield trials with various designs, focus on that fraction of the total variation that is relevant for identifying mega‐environments, duality in giving integrated information on both genotypes and environments, and relevance for the primary objective of showing which genotypes win where. The AMMI model meets these criteria effectively when the usual biplots are supplemented with several new types of graphs designed to address questions about mega‐environments. Preliminary results indicate that a small and workable number of mega‐environments often suffices to exploit interactions and increase yields.
Improvement of Resistance to Rust through Recurrent Selection in Pearl Millet
Authors: Tapsoba Hamado , Wilson Jeffrey P. , Hanna Wayne W.
Published: July 2010

Two pearl millet [Pennisetum glaucum (L.) R. Br. = P. typhoides (Burm.) Staff & Hubb., P. americanum (L.) K. Schum.] bulk populations, Tift #2 and Tift #5, served as base populations for four cycles of recurrent selection against susceptibility to Puccinia substriata Ell. & Barth. var. indica Ramachar & Cumm. A bulk inoculum of the pathogen was used. The objectives were to evaluate the progress achieved regarding overall resistance to the pathogen in the field and resistance to different races of the pathogen, and also to evaluate changes in unselected traits. During selection, the frequency of rust resistant plants continuously increased from about 30% in each base population to more than 85% by the third cycle of selection in both populations. An average increase of about 21 and 18% per cycle was obtained in Tift #2 and Tiff #5, respectively. A continuous increase of the frequency of plants resistant to some races of the pathogen was also obtained. In Tift #5, 80% of the plants were resistant to eight races by the third cycle of selection. The accumulation of resistance observed in the seedlings was manifested in the field, both in 1993 and 1994, by a reduction of the final rust severity from the base population to the fourth selection cycle of both populations. This improvement in resistance to the rust pathogen was accompanied by an increase in the frequency of plants resistant to Pyricularia grisea (Cooke) Sacc. only in Tift #2. Despite the improvement in the selected character, genetic variability for agronomic traits such as plant height, number of culms/plant, flowering date, and panicle length was successfully maintained within each population.
Mapping QTL for Seed Protein and Oil Content in Eight Soybean Populations
Authors: Brummer E. C. , Graef G. L. , Orf J. , Wilcox J. R. , Shoemaker R. C.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seeds contain high levels of protein and oil useful for human consumption. Increasing emphasis in breeding programs to produce soybeans with specific protein or oil content for specialty markets demands that more efficient manipulation of these traits be achieved. The objective of this study was to evaluate eight different soybean populations from the midwestern USA for genetic markers linked to seed protein and oil content. The populations were derived from the breeding programs at the Univ. of Minnesota, the Univ. of Nebraska, and Purdue Univ.‐USDA‐ARS. Each population consisted of between 69 and 100 individuals and was mapped with 21 to 85 restriction fragment length polymorphism markers. The F2‐derived populations were grown in field tests in 1992, 1993, and 1994 in the state in which they originated. Single factor analysis of variance was used to detect significant associations between markers and traits. Environmentally stable and environmentally sensitive quantitative trait loci (QTL) were identified for both protein and oil contents in all eight populations. The identified QTL were sensitive to both environment and genetic background although some common QTL were identified in multiple populations across several years. The results show that a number of QTL affect these traits and that markers could potentially be used in breeding programs designed to alter the seed protein and oil content.
Fifty‐Eight Years of Genetic Improvement of Short‐Season Soybean Cultivars in Canada
Authors: Voldeng H. D. , Cober E. R. , Hume D. J. , Gillard C. , Morrison M. J.
Published: July 2010

Soybean [Glycine max (L.) Merr.] production in short‐season areas has increased greatly because of improvements in cultivars and production practices. Previous studies of genetic improvement in soybean have reported yield increases of 0.5 to 1% per year. To evaluate the genetic improvement of short‐season germplasm, 41 cultivars ranging from maturity group 000 to 0, released from 1934 to 1992, were grown for 8 station‐years in Ontario and Quebec. Yield, maturity, plant height, lodging score, 100‐seed weight, seed protein and oil levels, and yield stability were regressed on year of release to determine if improvements have been made. Yield has been improved about 0.5% per year during the period under study; however, since 1976 yield has been improved about 0.7% per year. There is evidence that the rate of genetic improvement of seed yield is accelerating. Significant lodging reduction was also observed. Seed protein levels have been reduced 4 g kg‐1 yr‐1 and seed oil levels have increased 4 g kg‐1 yr‐1. Although yield has been increased, yield stability has remained constant.
Heat and Chilling Tolerance during Germination and Heat Tolerance during Flowering Are Not Associated in Cowpea
Authors: El‐kholy Aziza S. , Hall Anthony E. , Mohsen Awatif A.
Published: July 2010

Warm season crops can be stressed by either chilling or hot temperatures; however, breeding may overcome these problems. Studies were conducted to determine whether cowpea [Vigna unguiculata (L.) Walp.] genotypes differing in heat tolerance during flowering also differed in germination at chilling or hot temperatures. Genotypic differences in germination were detected at 15.5 ± 0.5°C and 38.5 ± 0.5°C. Leakage of electrolytes, carbohydrates, and amino acids were quantified during germination at chilling and at intermediate (25°C) and hot temperatures. Six closely related pairs of lines differing in heat tolerance during flowering did not consistently differ in either chilling or heat tolerance during germination. Genotypic differences in germination ability at chilling and hot temperatures were not associated. With chilling, genotypes differed in rate but not in maximal percentage germination, and rates of germination and leakage were negatively associated. With hot temperature, genotypic differences were in maximal percentage germination and these differences were not associated with differences in leakage. Leakage rates of electrolytes, carbohydrates, and amino acids were positively correlated and were very high under chilling and only slightly higher under hot compared with intermediate temperature. The mechanisms and presumably the genes involved in tolerance to chilling and heat during germination appear to differ and be different from the genes that confer heat tolerance during flowering. Consequently, it should be possible to breed cowpea cnltivars with both chilling tolerance during germination and heat tolerance during flowering for use in subtropical zones and different cnltivars with heat tolerance during both germination and flowering for use in tropical zones.
Modeling Temperature Effects on Cotton Internode and Leaf Growth
Authors: Reddy K. Raja , Hodges Harry F. , McKinion James M.
Published: July 2010

Cotton (Gossypium hirsutum L.) is grown commercially in temperatures that vary greatly during the season. The purpose of this study was to develop potential growth and developmental rates of cotton leaves and internodes as a function of temperature in a temperature limiting environment. That information may be used with growth duration and appropriate stress factors to develop a crop canopy development model. Plants were grown in sunlit plant growth chambers in five temperatures, 20/12°C to 40/32°C (day/night), at ambient (350 μL L− CO2) and twice ambient carbon dioxide levels in well‐watered and fertilized conditions. Plants were monitored daily for leaf unfolding dates, areas of leaves, and lengths of internodes at leaf unfolding, and growth of leaves and internodes. Durations of leaf and internode expansion were also determined. Leaf unfolding interval rates of both mainstem and fruiting branches increased as temperature increased; the rate of mainstem leaf unfolding interval increased more than the rate of branch leaf unfolding. Irrespective of sizes, leaves, and internodes fit a single relationship of relative expansion rates and age for each temperature condition. Enriching CO2 to twice the ambient level did not change these relationships. Increasing temperature increased maximum growth rate, decreased the decay in the rate of expansion due to age, and reduced growth duration of both leaves and internodes. Internodes typically took less time than leaves to elongate at all temperatures. Leaf area and internode length at leaf unfolding increased as temperature increased to 27 to 30°C, then decreased at higher temperatures.
Genetic Diversity among North American Spring Wheat Cultivars: II. Ancestors Contributions to Gene Pools of Different Eras and Region
Authors: van Beuningen L. T. , Busch R. H.
Published: July 2010

A broad genetic base for a crop species such as wheat (Triticum spp.) may be important to reduce genetic vulnerability and assure long‐term potential for genetic gain. The number and diversity of original ancestors can provide insight into relative genetic diversity within and among gene pools. Based on the coefficient of parentage values between cultivars and ancestral lines, the relative genetic contributions of ancestral lines to spring wheat (Triticum aestivum L.) cultivars were computed for successive 25‐yr time periods. The cultivars were from Canada (47), the USA (133), and Mexico (90). Genetic backgrounds were studied for important changes in the ancestral base over time and to determine trends that continue today. About 124 ancestors, tracing to 32 countries on five continents, were found to have contributed to the North American spring wheat gene pool. Canadian western red spring cultivars released before 1950 had an intermediate level of ancestral diversity. Their post‐1975 cultivars have narrow ancestral diversities probably due to strict quality regulations. They consist primarily of ‘Thatcher’ germplasm modified by a set of pest resistance genes carefully managed in backcross schemes. Before 1950, the U.S. hard red spring wheat cultivars traced to the same Thatcher ancestors but also to ‘Kota’ and ‘Yaroslav’. Many more ancestors were added to this base after 1950 and especially after 1975. This was a side effect of the incorporation of pest resistance, most notably from sources ‘Gabo‐Timstein’, ‘Frontana’, and ‘Kenya 58’, and reduced height sources, most notably CIMMYT cultivars with new ancestry from ‘Kenya 324’ and Turkey. CIMMYT cultivars have also expanded their genetic base over time, with the systematic incorporation of new ancestry from various sources including winter wheats. Introduction of novel alleles from wild ancestors or other, sources should contribute to future broadening of the genetic base, maximizing genetic gains, and reducing genetic vulnerability of the gene pools.
DNA Content and Chloroplast DNA Polymorphisms among Switchgrasses from Remnant Midwestern Prairies
Authors: Hultquist Sherry J. , Vogel K. P. , Lee D. J. , Arumuganathan K. , Kaeppler S.
Published: July 2010

Panicum virgatum L. (switchgrass) is perennial grass that is native to most of the USA. The principal use of switchgrass has been as a pasture and range grass for forage production during the warmer summer months. The objective of this research was to determine if DNA content and chloroplast DNA (cpDNA) polymorphisms existed among and within switchgrass accessions from Midwestern prairie sites. Twenty‐eight switchgrass accessions from remnant prairie sites were surveyed in 1994 for the upland cytotype (U) or lowland (L) cytotype in the cpDNA by means of restriction endonuclease BamHI and sorghum cpDNA probe pLD 5. These accessions were also surveyed in 1994 for DNA content differences ltow cytometry. One accession, IA 31, contained a mixture of cytotypes indicating that both cytotypes can occur at a single remnant prairie site. The other Midwestern remnant prairies that were represented in this study contained only the U cytotype. The flow cytometry results indicated that switchgrass populations found within the Midwestern sites can be a mixture of ploidy levels with either 3 (tetraploid) or 6 (octaploid) pg DNA per cell. These results indicated that germplasm from Midwestern prairies should be identified according to DNA content and cytotype before it is utilized in developmental programs by plant breeders.
Winter Survival and Competition in a Mixture of Winter Wheat Cultivars
Authors: Thomas J. B. , Schaalje G. B.
Published: July 2010

For winter wheat (Triticum aestivum L.) in western Canada, cold resistance is a major factor in winter survival ability (WSA) and yield stability. The few genotypes that display the highest levels of WSA are tall, low in yield potential and weak strawed. While improved types with good WSA have been developed, none of these are as hardy as the elite lines. This study examines the role of natural selection in the development of winterhardy wheats with desirable plant types. A mixture of six botanically distinguishable cultivars with wide differences in plant type and WSA was started from equal numbers of seed and grown repeatedly in southwestern Alberta over several environments and years. ‘Kharkov 22MC’, ‘Westmont’, ‘Jones Fife’, and ‘Gaines’ have all been cultivated commercially in southern Alberta while ‘Alabaskaja’ and ‘Bezostaya’ are also adapted. Under severe cold stress, tender cultivars killed out and winterhardy cultivars dominated the mixture in 1 yr. In a second experiment, six cycles of grain harvest and reseeding through milder winters produced similar changes (rs = 0.94, d.f. = 4, P < 0.01) with no evidence of differential winterkill. For five cultivars, high reproduction in the second experiment was associated with the ability of pure stands to compete with adjacent rows (rs = 1.0, d.f. = 3, P < 0.0001). The exception (Jones Fife) was tall and competitive as a pure stand but reproduced poorly in the mixture. Unlike most winter wheats which become prostrate in the fall, Jones Fife resembles spring wheat and keeps its leaves upright. Increased defoliation from freezing due to non‐prostrate plant habit may be expected to reduce the competitive ability of seedlings in mixtures during spring recovery. Jones Fife notwithstanding, tall and winterhardy cultivars with low yield survived best in the mixture while higher yielding, short‐strawed types survived poorly. In the absence of winterkill, changes hi the mixture were attributed to competition. To minimize the advantage of competitive types, mass selection for WSA should be conducted in high‐stress environments for a few generations only.