bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maize Yield Response to Increased Assimilate Supply1
Authors: Schoper J. B. , Johnson R. R. , Lambert R.J. 
Published: July 2010

The capacity of the maize (Zea mays L.) ear to accept greater assimilate supplies is an important parameter in some strategies to increase grain yield. This problem was studied by increasing assimilate supply at several growth stages and determining the effects on grain yield, yield components and partitioning ratios. During a 2‐year period, a single‐eared hybrid was grown at a control density of 64,500 plants/ha and was thinned to 43,000 and 21,500 plants/ha at growth stages ranging from soon after emergence to 3 weeks after silk emergence. In a second experiment, light reflectors were placed between rows of three different hybrids for 2‐week intervals ranging from about 3 weeks before to about 6 weeks after silk emergence. Both thinning and reflector treatments were designed to increase assimilate supply to the ear.In thinning experiments, control densities yielded about 10,700 kg/ha during 1978 and 1979. Thinning at 2.5 weeks before silking increased yield per plant up to 41% while thinning at 3 weeks after silking caused an 11% increase. Increased kernel number and weight/kernel accounted for the yield increase, and the relative contribution of each shifted from one year to the next even though yields were similar both years. Ear number, kernel row number and duration of grain fill were unaffected by increased assimilate supply. Yield increases obtained by thinning to the intermediate density occurred with little change in partitioning ratio of dry weight and N. Thinning to the lowest density caused a decline in the partitioning ratios. Reflector experiments in spite of some heat stress demonstrated that increased assimilate supply for short, discrete periods could cause similar results. We conclude that under our U.S. Corn Belt conditions, increasing assimilate supply can result in a grain yield increase per plant and can do this without altering the length of grain‐filling or the partitioning ratios.
Allelic and Linkage Relations among Genes for Stem Rust Resistance from Triticum turgidum, ‘Mindum,’ ‘Acme’ Selection, ‘Palestine,’ and ‘Khapli’1
Authors: Williams N. D. , Miller J. D. 
Published: July 2010

The objective was to determine allelic and linkage relations among genes for resistance to stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn) in 13 lines of tetraploid wheat (Triticum turgidum L.) derived from crosses of susceptible ‘Marruecos 9623’ with resistant ‘Mindum’ (three lines), ‘Acme’ selection (three lines), ‘Khapli’ emmer (four lines), and ‘Palestine’ (three lines). Each of the 13 lines had a single gene for resistance to stem rust. A partial diallel cross was made among the lines, and F2 seedlings were tested for reaction to cultures 111‐SS2 and 56‐1 of stem rust. Absence of segregation indicated that the parents had allelic or closely linked genes for resistance; segregation for resistance and susceptibility indicated nonallelism.A uniformly resistant F2 from a cross between lines Srda‐2 (gene for resistance from Acme selection) and Srdm‐1 (gene for resistance from Mindum) indicated that these lines had allelic (or closely linked) genes for resistance. Also, lines Srda‐3, Srdm‐2, and Plt‐C (genes for resistance from Acme selection, Mindum, and Palestine, respectively) had allelic (or closely linked) genes for resistance. All other crosses segregated resistant and susceptible seedlings which indicated that the parental lines had different single genes for resistance.Twenty‐eight crosses appeared to segregate into three classes, one like the parent having the highest level of resistance, one like the parent having the lowest level of resistance, and one susceptible. Of the 28 crosses, segregation in 19 was a good fit to a 12:3:1 ratio. Genes conditioning high levels of resistance usually masked those conditioning low levels.Segregants more resistant than either parent occurred in 11 crosses and indicated that genes for resistance from the two parents had cumulative effects. Genes for resistance in parental lines in each of five crosses conditioned similar levels of resistance, and most of these F2s segregated in ratios of approximately 15 resistant:1 susceptible. Statistically significant deviations from tested ratios occurred in the F2 from 16 crosses, but the direction of the deviations did not imply linkage. The F2 data of seven crosses were not tested by chi‐square because sample sizes were small or segregation ratios were irregular.
Development of Arm Specific RAPD Markers for Rye Chromosome 2R in Wheat
Authors: Brunell Mark S. , Lukaszewski Adam J. , Whitkus Richard 
Published: July 2010

ABSTRACTRye (Secale cereale L.) chromosome 2R carries several genes for resistance to biotic and abiotic stresses, which could be used in wheat (Triticum aestivum L.) improvement. To make these genes accessible in breeding, translocations of 2R to wheat chromosome 2B have been generated. To compensate for the lack of clearly identifiable cytological markers on chromosome 2R, random amplified polymorphic DNAs (RAPDs) were employed as markers. Wheat lines homozygous for centric translocations 2RS.2BL and 2BS.2RL were screened with 489 primers, resulting in 65 clear and reproducible RAPD polymorphisms. To assign the polymorphisms to individual arms of chromosomes 2R and 2B, the arms of the translocations were separated by centric misdivision and the resulting progeny with desired chromosome constructs were rescreened. As a result, 17 markers were assigned to chromosome arm 2RS, 15 to 2RL, and the remaining 33 most likely located on 2B. Preliminary mapping studies (not shown here) have indicated that some of these markers are evenly distributed along the chromosome arms. These markers should be useful for the localization of translocation breakpoints in recombinant wheat‐rye chromosomes.
Yield Components of Wheat Grown under High Temperature Stress during Reproductive Growth
Authors: Gibson L. R. , Paulsen G. M. 
Published: July 2010

ABSTRACTHigh temperature is a major determinant of wheat (Triticum aestivum L.) development and growth, decreasing yields by 3 to 5% per 1°C increase above 15°C in plants under controlled conditions. Even greater yield differences have been reported between favorable and unfavorable temperature conditions in the field. The objective of this study was to identify the yield components of the hard red winter wheat cultivar Karl 92 that are affected by controlled high temperature during maturation of intact plants under simulated field populations. Plants at a final density of 144 m2 were grown in the greenhouse until anthesis and transferred to growth chambers for temperature treatment. Day/night temperatures of 20/20, 25/20, 30/20, and 35/20°C were imposed from 10 and 15 d after anthesis until ripeness in two experiments, and temperatures of 25/20, 30/20, and 35/20°C were applied from 20 d after anthesis until ripeness in a third experiment. Grain yield was reduced by 78%, kernel number was reduced by 63%, and kernel weight was reduced by 29% at 35/20°C compared with 20/20°C from 10 d after anthesis until ripeness. The yield loss from high temperature applied during this period was much greater than for previous controlled‐environment studies. Kernel numbers in treatments applied during early reproductive growth in our study were as sensitive to high temperature as wheat plants in previous field studies. High temperature applied 15 d after anthesis until ripening reduced grain yield 18%. Since kernel number was set by this time, the loss was exclusively due to decreased kernel weight. High temperature imposed from 20 d after anthesis decreased kernel weight by 18%.
Seed Dormancy and Aging in Atra Paspalum
Authors: Kalmbacher R. S. , West S. H. , Martin F. G. 
Published: July 2010

ABSTRACTSeed dormancy and aging affect maintenance of germination in storage and ultimately seedling establishment. The effects that year of harvest, heat vs. air drying seed at harvest, storage environment, and aging had on germination of ‘Suerte’ atra paspalum (Paspalum atratum Swallen) were studied. Across 5 yr, average germination of fresh seed at harvest was 0% during 0 to 7 d and 5% during 8 to 14 d of a 28‐d germination period. Total germination depended on year of harvest and ranged from 9 to 46%. Oven drying (40°C for 24 h) at harvest increased germination in 2 of 5 yr. Storing seed for 6 mo in a building with no environmental control (ambient condition) increased germination to 69% (3‐yr average) and shifted most of the germination to the first 7 d, but germination was nil after 1 yr. Germination averaged 55% at 28 d after harvest for seed stored at 3°C and changed little for up to 4 yr. Oven drying seed at harvest delayed the break in dormancy ≈1 mo compared with air drying seed. Chilling air‐dried, ambient stored seed at 3°C for 48 h before testing reduced germination at 84 d after harvest (compared with 28 d and 6 mo). Neither chilling oven‐dried seed nor heat (40°C for 24 h before testing) treatment of oven‐ and air‐dried seed affected germination. Removal of the lemma and palea at harvest resulted in 96% germination compared with 26% for intact seed. Treatment of freshly harvested seed with H2SO4 for 6 min and accelerated aging (48 h at 41°C, 100% relative humidity) increased germination from 29 to 68% and 30 to 48%, respectively. Dormancy in atra paspalum is short‐lived and should be of minor agronomic importance with fall seed harvest and spring sowing. Consideration must be given to seed storage conditions to assure viability beyond 1 yr.
Inheritance of Russian Wheat Aphid Resistance in Spring Barley Germplasm Line STARS‐9577B
Authors: Mornhinweg D. W. , Porter D. R. , Webster J. A. 
Published: July 2010

ABSTRACTThe Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a major pest of barley (Hordeum vulgare L.) in the western USA. STARS‐9577B (PI 591617), a six‐rowed, spring barley germplasm line with a high level of resistance to RWA, was recently released to barley breeders for barley improvement. Understanding the inheritance of RWA resistance in this germplasm line is necessary for breeders to develop an effective strategy for utilization of this germplasm in their breeding programs. This greenhouse study was conducted to determine the genetic control of RWA resistance in STARS‐9577B. Crosses were made between ‘Morex’, a susceptible, six‐rowed, malting barley cultivar, and STARS‐9577B. Genetic analyses were performed on reaction to RWA of parents, F1, reciprocal F1, F2, backcrosses (BC1F1) to both parents, and F2‐derived F3 families. Reaction was based on a visual rating scale of 1 to 9 (1 = no damage, 9 = dead plant). Segregation in the F2 and BC1F1 populations indicated multiple gene control. Seventy‐seven F3 families were found to be homozygous resistant and 18 homozygous susceptible, indicating two gene control of RWA resistance in STARS‐9577B. Analysis of data from F2 and BC1F1 populations suggested RWA resistance in STARS‐9577B is controlled by dominant alleles at two loci, with alleles at one locus conferring a high level of resistance and alleles at the other locus conferring an intermediate level of resistance only when recessive alleles are present at the first locus.
Root Growth and Yield of Differing Alfalfa Rooting Populations under Increasing Salinity and Zero Leaching
Authors: Vaughan Laura V. , MacAdam Jennifer W. , Smith Steven E. , Dudley Lynn M. 
Published: July 2010

ABSTRACTAccumulation of salinity in the root zone can be detrimental to sustained crop production. Irrigation, even with moderately saline water, pushes accumulated salts deeper into the root zone, allowing roots to proliferate in regions of relatively low salinity. Two alfalfa (Medicago sativa L.) subpopulations with low‐ and high‐fibrous rooting characteristics, MnPL‐9‐LF and MnPL‐9‐HF, were used to test the effectiveness of increased rooting on yield when plants were irrigated with saline water but without leaching. Treatments were three levels of heterogeneous root zone salinity predicted by the SOWACH model to represent 10, 20, and 30 yr of irrigation with saline water. Plants were grown for five successive harvests in 10‐cm‐diam., 130‐cm‐deep cylinders. The treatments were constructed with NaCl and gypsum. As soil became depleted to 50% extractable water, irrigation water with an electrical conductivity (EC) of 2.8 dS m−1 was applied. By the fifth harvest, soil solution EC from the top to the bottom of the profile ranged from 3 to 12 dS m−1 for the control and from 3 to 23 dS m−1 for the highest salinity treatment. Root production of the high‐fibrous root type was stimulated more at low and medium salinity than that of the low‐fibrous root type. Across salinity treatments, final root length density (cm root length per cm3 soil volume) was 24% higher for the high‐fibrous root type, and herbage yield of the high‐fibrous root type was 14% higher than that of the low‐fibrous root type. Differential rooting was greatest in the upper half of the root zone. High fibrous rooting in alfalfa is a trait with potential usefulness as a salinity stress avoidance mechanism.
Mapping and Progress toward Map‐Based Cloning of Brown Planthopper Biotype‐4 Resistance Gene Introgressed from Oryza officinalis into Cultivated Rice, O. sativa
Authors: Renganayaki K. , Fritz Allan K. , Sadasivam S. , Pammi Sujata , Harrington Sandra E. , McCouch Susan R. , Kumar S. Mohan , Reddy Avutu Sam 
Published: July 2010

ABSTRACTBrown plant hopper (BPH), Nilaparvata lugens (Stal.), is a serious insect pest of rice in Asia, causing direct losses and vectoring Rice grassy stunt virus (RGSV) and Rice ragged stunt virus (RRSV). Recombinant inbred lines (RILs) developed from a cross between ‘IR50’ and ‘IR54745‐2‐21‐12‐17‐6’ were used to identify random amplified polymorphic DNA (RAPD) markers closely linked to a BPH Biotype‐4 resistance gene [Bph13 (t)] derived from Oryza officinalis Wall. Bulked segregant analysis (BSA) using RAPD primers identified 11 polymorphic fragments. Six fragments, AJ09260a, AL05220a, AK10690a, AK10430c, AK10380d, and AJ01200a, were linked in coupling phase to the Bph13 (t) locus. The remaining five fragments, AJ09230b, AJ09180c, AJ09100d, AL05400b, and AK10340e, were linked in repulsion. The most closely linked RAPD marker, AJ09230b, was converted to a codominant linked sequence tagged sites (STS) marker. This marker mapped 1.3 centimorgans (cM) from the resistance gene and was placed on rice chromosome 3 by means of ‘IR64’ × ‘Azucena’ doubled haploid (DH) population. The tightly linked STS marker could be used for marker‐assisted selection (MAS). In addition, these markers will be useful for a positional cloning strategy to isolate the resistance gene.
Seasonal Poa annua L. Seedling Emergence Patterns in Maryland
Authors: Kaminski John E. , Dernoeden Peter H. 
Published: July 2010

ABSTRACTAnnual bluegrass (Poa annua L.; ABG) can be a major weed problem in golf course turf. Research‐based information on the seasonal emergence patterns of ABG is limited. The objectives of this four‐year field study were (i) to determine seasonal ABG emergence patterns in Maryland, (ii) to determine peak period(s) of ABG emergence, and (iii) to determine the date and estimated percentage of seedlings emerged when the rate of emergence declines. Annual bluegrass seedlings were found to emerge between August and May in two Maryland golf course roughs. A majority (50–70%) of seedling emergence occurred between late September and mid‐October, and peak germination generally was observed in early October. The linear increase in ABG seedling emergence generally ended by early November; however, 24% of all seedlings emerged between November and May. No major ABG emergence cycles were observed during the spring in any year. Mean daily temperatures generally were ≤20°C during peak ABG emergence periods, and germination was stimulated by precipitation. Since the genetic diversity of ABG is well known, these findings may only be applicable to Maryland and regions with similar environmental conditions.
Genetic Relatedness of Portuguese Rice Accessions from Diverse Origins as Assessed by Microsatellite Markers
Authors: Jayamani P. , Negrão S. , Martins M. , Maçãs B. , Oliveira M. M. 
Published: July 2010

ABSTRACTSimple sequence repeat (SSR) markers detect a significantly high degree of polymorphism in rice (Oryza sativa L.) and are particularly suitable for evaluating genetic diversity among closely related cultivars. A total of 176 rice accessions originating from 19 countries in the Portuguese working germplasm collection and two standard rice varieties (IR36‐indica and Nipponbare‐japonica) were analyzed for DNA profile using 24 SSR loci covering two loci per chromosome. A total of 184 alleles were detected. The number of alleles per locus ranged from 3 to 16, with an average of 7.7, and the PIC value ranged from 0.179 to 0.894 with an average of 0.667. All the loci were polymorphic among the accessions and clearly distinguished the indica and japonica subspecies. At 20% similarity, cluster analysis of the 178 accessions revealed three major groups, japonica, basmati, and indica (Groups I, II, and III, respectively). The japonica group contained 87% of the accessions and showed a wide range of similarity values (0.21–0.92), revealing a high degree of diversity among the accessions. Many of the accessions included in this study are morphologically similar and lack pedigree information. Hence, identification of genetic distances among the accessions should improve their use in breeding programs. As a result of this study, genetically diverse parents can be identified, increasing the usefulness of germplasm collections by broadening the genetic base of rice varieties.
Probabilistic Models for Collecting Genetic Diversity: Comparisons, Caveats, and Limitations
Authors: Lockwood Dale R. , Richards Christopher M. , Volk Gayle M. 
Published: July 2010

ABSTRACTMethods for collecting genetic diversity from in situ populations are important tools for plant conservation. Many quantitative collection strategies for sampling populations without a priori information regarding the ecology, reproductive biology, or population genetic structure of the taxa have been proposed, but their different assumptions regarding the collection scale and the basis for diversity often make them difficult to compare. Understanding the limitations of the different strategies enables collectors to make more informed choices when implementing conservation and restoration projects or collecting for germplasm improvement. We compare two genetically based strategies under a common set of assumptions and extend the probabilistic arguments of the strategies to accommodate rare alleles, multiple loci, and multiple populations. The recommendations of many models are based on a single locus, but larger numbers of individuals must be collected to assure with a high probability (>0.95) the acquisition of alleles at multiple independent loci within a population. Sampling from multiple populations linked by gene flow may offset this increase. Additionally, the likelihood of capturing rare alleles remains high when sampling for multiple loci or across multiple populations. Comparison of the models provides germplasm collectors with a basis to evaluate risks of over‐ and undersampling to capture genetic diversity within a species.
Relationship of Flag Leaf Characteristics to Economically Important Traits in Two Spring Wheat Crosses
Authors: Blake N. K. , Lanning S. P. , Martin J. M. , Sherman J. D. , Talbert L. E. 
Published: July 2010

ABSTRACTSelection in unreplicated head rows for traits that affect yield potential is an objective for many wheat (Triticum aestivum L. ) breeding programs. Flag leaf characteristics provide a potential target for selection. In this experiment, we determined flag leaf and yield characteristics for recombinant inbred lines (RIL) from two crosses, McNeal/Thatcher and McNeal/Reeder. McNeal is intermediate between Thatcher and Reeder for green flag leaf duration after heading. Flag leaf characteristics had heritability greater than 0.70 for all traits. Heading date was positively associated with yield for one cross in dryland and irrigated environments but tended to be negatively associated with grain volume, kernel weight, and kernel protein in both crosses. The duration of green leaves after heading was positively correlated with yield, grain volume, and kernel weight in both sets of environments in the McNeal/Thatcher RIL. This trait was positively correlated with grain volume, kernel weight, and grain protein in dryland environments in the McNeal/Reeder RIL. Our results suggest that selection against late heading and for a long duration of green flag leaves after heading should result in gains in yield potential, grain volume, and kernel weight for spring wheat.
Pollen Dispersion within a Population, Nonrandom Mating Theory, and Number of Replications in Polycross Nurseries
Authors: Nyquist W. E. , Santini J. B. 
Published: July 2010

ABSTRACTA breeder is uncertain how many replications to include in a polycross. Our objective was to develop a method to answer the question. Four isolated, space‐planted nurseries on a 0.91‐m grid of 29 rows by 35 plants were established of ryegrass (Lolium perenne L.), a wind‐pollinated species, with rows in each nursery oriented differently with respect to the compass. The middle row was homozygous for the dominant fluorescent marker gene. Seeds from the seven middle plants in the seven rows closest to the middle row on both sides were observed for the frequency of the dominant gene. From these observations a two‐parameter exponential pollen dispersal function was fitted for the mean of all eight directions combined. The variance among the cross‐pollination frequencies qjk was calculated under two pollination assumptions: (i) pollination confined within each replication and (ii) pollination across all replications. After bulking equal quantities of seed from all replications we have the variance of the mean cross frequencies The square root of this variance, , was used as a measure of the closeness to random mating. The required number of replications to achieve specific levels of closeness to random mating is given for 3 to 100 clones for Assumption 1. The measure of closeness to random mating is given for 3 to 100 clones and up to 30 replications for Assumption 2. When pollination is assumed to occur across replications, a 70% reduction in the variance of is obtained compared to pollination within replications. Hence, fewer replications are required in this case.
Analysis of Genotype‐by‐Environment Interaction in Wheat Using a Structural Equation Model and Chromosome Substitution Lines
Authors: Dhungana P. , Eskridge K. M. , Baenziger P. S. , Campbell B. T. , Gill K. S. , Dweikat I. 
Published: July 2010

ABSTRACTThe presence of genotype‐by‐environment interaction (GEI) complicates selection of superior genotypes and an understanding of environmental and genotypic causes of significant GEI is important in all stages of plant breeding. We present a systematic approach for understanding GEI of complex interrelated traits by combining chromosome substitution lines that allowed us to study the effects of genes on a single chromosome with a structural equation model that approximated the complex processes involving genes, environmental conditions, and traits. We applied the approach to recombinant inbred chromosome wheat lines grown in multiple environments. The final model explained 74% of the yield GEI variation and we found that spikes per square meter (SPSM) GEI had the highest direct effect on yield GEI and that the genetic markers were mostly sensitive to temperature and precipitation during the vegetative and reproductive periods. In addition, we identified a number of direct and indirect causal relationships that described how genes interacted with environmental factors to affect GEI of several important agronomic traits which would not have been possible with previously used methods.